1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
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14 @setfilename gnat_ugn.info
17 Copyright @copyright{} 1995-2009 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.2 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
71 @c cause the document build to fail.
73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
81 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
84 @c This flag is used where the text refers to conditions that exist when the
85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * Generating Ada Bindings for C and C++ headers::
191 * Other Utility Programs::
192 * Running and Debugging Ada Programs::
194 * Code Coverage and Profiling::
197 * Compatibility with HP Ada::
199 * Platform-Specific Information for the Run-Time Libraries::
200 * Example of Binder Output File::
201 * Elaboration Order Handling in GNAT::
202 * Conditional Compilation::
204 * Compatibility and Porting Guide::
206 * Microsoft Windows Topics::
208 * GNU Free Documentation License::
211 --- The Detailed Node Listing ---
215 * What This Guide Contains::
216 * What You Should Know before Reading This Guide::
217 * Related Information::
220 Getting Started with GNAT
223 * Running a Simple Ada Program::
224 * Running a Program with Multiple Units::
225 * Using the gnatmake Utility::
227 * Editing with Emacs::
230 * Introduction to GPS::
233 The GNAT Compilation Model
235 * Source Representation::
236 * Foreign Language Representation::
237 * File Naming Rules::
238 * Using Other File Names::
239 * Alternative File Naming Schemes::
240 * Generating Object Files::
241 * Source Dependencies::
242 * The Ada Library Information Files::
243 * Binding an Ada Program::
244 * Mixed Language Programming::
246 * Building Mixed Ada & C++ Programs::
247 * Comparison between GNAT and C/C++ Compilation Models::
249 * Comparison between GNAT and Conventional Ada Library Models::
251 * Placement of temporary files::
254 Foreign Language Representation
257 * Other 8-Bit Codes::
258 * Wide Character Encodings::
260 Compiling Ada Programs With gcc
262 * Compiling Programs::
264 * Search Paths and the Run-Time Library (RTL)::
265 * Order of Compilation Issues::
270 * Output and Error Message Control::
271 * Warning Message Control::
272 * Debugging and Assertion Control::
273 * Validity Checking::
276 * Using gcc for Syntax Checking::
277 * Using gcc for Semantic Checking::
278 * Compiling Different Versions of Ada::
279 * Character Set Control::
280 * File Naming Control::
281 * Subprogram Inlining Control::
282 * Auxiliary Output Control::
283 * Debugging Control::
284 * Exception Handling Control::
285 * Units to Sources Mapping Files::
286 * Integrated Preprocessing::
291 Binding Ada Programs With gnatbind
294 * Switches for gnatbind::
295 * Command-Line Access::
296 * Search Paths for gnatbind::
297 * Examples of gnatbind Usage::
299 Switches for gnatbind
301 * Consistency-Checking Modes::
302 * Binder Error Message Control::
303 * Elaboration Control::
305 * Binding with Non-Ada Main Programs::
306 * Binding Programs with No Main Subprogram::
308 Linking Using gnatlink
311 * Switches for gnatlink::
313 The GNAT Make Program gnatmake
316 * Switches for gnatmake::
317 * Mode Switches for gnatmake::
318 * Notes on the Command Line::
319 * How gnatmake Works::
320 * Examples of gnatmake Usage::
322 Improving Performance
323 * Performance Considerations::
324 * Text_IO Suggestions::
325 * Reducing Size of Ada Executables with gnatelim::
326 * Reducing Size of Executables with unused subprogram/data elimination::
328 Performance Considerations
329 * Controlling Run-Time Checks::
330 * Use of Restrictions::
331 * Optimization Levels::
332 * Debugging Optimized Code::
333 * Inlining of Subprograms::
334 * Other Optimization Switches::
335 * Optimization and Strict Aliasing::
337 * Coverage Analysis::
340 Reducing Size of Ada Executables with gnatelim
343 * Correcting the List of Eliminate Pragmas::
344 * Making Your Executables Smaller::
345 * Summary of the gnatelim Usage Cycle::
347 Reducing Size of Executables with unused subprogram/data elimination
348 * About unused subprogram/data elimination::
349 * Compilation options::
351 Renaming Files Using gnatchop
353 * Handling Files with Multiple Units::
354 * Operating gnatchop in Compilation Mode::
355 * Command Line for gnatchop::
356 * Switches for gnatchop::
357 * Examples of gnatchop Usage::
359 Configuration Pragmas
361 * Handling of Configuration Pragmas::
362 * The Configuration Pragmas Files::
364 Handling Arbitrary File Naming Conventions Using gnatname
366 * Arbitrary File Naming Conventions::
368 * Switches for gnatname::
369 * Examples of gnatname Usage::
374 * Examples of Project Files::
375 * Project File Syntax::
376 * Objects and Sources in Project Files::
377 * Importing Projects::
378 * Project Extension::
379 * Project Hierarchy Extension::
380 * External References in Project Files::
381 * Packages in Project Files::
382 * Variables from Imported Projects::
385 * Stand-alone Library Projects::
386 * Switches Related to Project Files::
387 * Tools Supporting Project Files::
388 * An Extended Example::
389 * Project File Complete Syntax::
391 The Cross-Referencing Tools gnatxref and gnatfind
393 * Switches for gnatxref::
394 * Switches for gnatfind::
395 * Project Files for gnatxref and gnatfind::
396 * Regular Expressions in gnatfind and gnatxref::
397 * Examples of gnatxref Usage::
398 * Examples of gnatfind Usage::
400 The GNAT Pretty-Printer gnatpp
402 * Switches for gnatpp::
405 The GNAT Metrics Tool gnatmetric
407 * Switches for gnatmetric::
409 File Name Krunching Using gnatkr
414 * Examples of gnatkr Usage::
416 Preprocessing Using gnatprep
417 * Preprocessing Symbols::
419 * Switches for gnatprep::
420 * Form of Definitions File::
421 * Form of Input Text for gnatprep::
424 The GNAT Run-Time Library Builder gnatlbr
427 * Switches for gnatlbr::
428 * Examples of gnatlbr Usage::
431 The GNAT Library Browser gnatls
434 * Switches for gnatls::
435 * Examples of gnatls Usage::
437 Cleaning Up Using gnatclean
439 * Running gnatclean::
440 * Switches for gnatclean::
441 @c * Examples of gnatclean Usage::
447 * Introduction to Libraries in GNAT::
448 * General Ada Libraries::
449 * Stand-alone Ada Libraries::
450 * Rebuilding the GNAT Run-Time Library::
452 Using the GNU make Utility
454 * Using gnatmake in a Makefile::
455 * Automatically Creating a List of Directories::
456 * Generating the Command Line Switches::
457 * Overcoming Command Line Length Limits::
460 Memory Management Issues
462 * Some Useful Memory Pools::
463 * The GNAT Debug Pool Facility::
468 Stack Related Facilities
470 * Stack Overflow Checking::
471 * Static Stack Usage Analysis::
472 * Dynamic Stack Usage Analysis::
474 Some Useful Memory Pools
476 The GNAT Debug Pool Facility
482 * Switches for gnatmem::
483 * Example of gnatmem Usage::
486 Verifying Properties Using gnatcheck
488 * Format of the Report File::
489 * General gnatcheck Switches::
490 * gnatcheck Rule Options::
491 * Adding the Results of Compiler Checks to gnatcheck Output::
492 * Project-Wide Checks::
496 Sample Bodies Using gnatstub
499 * Switches for gnatstub::
501 Other Utility Programs
503 * Using Other Utility Programs with GNAT::
504 * The External Symbol Naming Scheme of GNAT::
505 * Converting Ada Files to html with gnathtml::
508 Code Coverage and Profiling
510 * Code Coverage of Ada Programs using gcov::
511 * Profiling an Ada Program using gprof::
514 Running and Debugging Ada Programs
516 * The GNAT Debugger GDB::
518 * Introduction to GDB Commands::
519 * Using Ada Expressions::
520 * Calling User-Defined Subprograms::
521 * Using the Next Command in a Function::
524 * Debugging Generic Units::
525 * GNAT Abnormal Termination or Failure to Terminate::
526 * Naming Conventions for GNAT Source Files::
527 * Getting Internal Debugging Information::
535 Compatibility with HP Ada
537 * Ada Language Compatibility::
538 * Differences in the Definition of Package System::
539 * Language-Related Features::
540 * The Package STANDARD::
541 * The Package SYSTEM::
542 * Tasking and Task-Related Features::
543 * Pragmas and Pragma-Related Features::
544 * Library of Predefined Units::
546 * Main Program Definition::
547 * Implementation-Defined Attributes::
548 * Compiler and Run-Time Interfacing::
549 * Program Compilation and Library Management::
551 * Implementation Limits::
552 * Tools and Utilities::
554 Language-Related Features
556 * Integer Types and Representations::
557 * Floating-Point Types and Representations::
558 * Pragmas Float_Representation and Long_Float::
559 * Fixed-Point Types and Representations::
560 * Record and Array Component Alignment::
562 * Other Representation Clauses::
564 Tasking and Task-Related Features
566 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
567 * Assigning Task IDs::
568 * Task IDs and Delays::
569 * Task-Related Pragmas::
570 * Scheduling and Task Priority::
572 * External Interrupts::
574 Pragmas and Pragma-Related Features
576 * Restrictions on the Pragma INLINE::
577 * Restrictions on the Pragma INTERFACE::
578 * Restrictions on the Pragma SYSTEM_NAME::
580 Library of Predefined Units
582 * Changes to DECLIB::
586 * Shared Libraries and Options Files::
590 Platform-Specific Information for the Run-Time Libraries
592 * Summary of Run-Time Configurations::
593 * Specifying a Run-Time Library::
594 * Choosing the Scheduling Policy::
595 * Solaris-Specific Considerations::
596 * Linux-Specific Considerations::
597 * AIX-Specific Considerations::
598 * Irix-Specific Considerations::
600 Example of Binder Output File
602 Elaboration Order Handling in GNAT
605 * Checking the Elaboration Order::
606 * Controlling the Elaboration Order::
607 * Controlling Elaboration in GNAT - Internal Calls::
608 * Controlling Elaboration in GNAT - External Calls::
609 * Default Behavior in GNAT - Ensuring Safety::
610 * Treatment of Pragma Elaborate::
611 * Elaboration Issues for Library Tasks::
612 * Mixing Elaboration Models::
613 * What to Do If the Default Elaboration Behavior Fails::
614 * Elaboration for Access-to-Subprogram Values::
615 * Summary of Procedures for Elaboration Control::
616 * Other Elaboration Order Considerations::
618 Conditional Compilation
619 * Use of Boolean Constants::
620 * Debugging - A Special Case::
621 * Conditionalizing Declarations::
622 * Use of Alternative Implementations::
627 * Basic Assembler Syntax::
628 * A Simple Example of Inline Assembler::
629 * Output Variables in Inline Assembler::
630 * Input Variables in Inline Assembler::
631 * Inlining Inline Assembler Code::
632 * Other Asm Functionality::
634 Compatibility and Porting Guide
636 * Compatibility with Ada 83::
637 * Compatibility between Ada 95 and Ada 2005::
638 * Implementation-dependent characteristics::
640 @c This brief section is only in the non-VMS version
641 @c The complete chapter on HP Ada issues is in the VMS version
642 * Compatibility with HP Ada 83::
644 * Compatibility with Other Ada Systems::
645 * Representation Clauses::
647 * Transitioning to 64-Bit GNAT for OpenVMS::
651 Microsoft Windows Topics
653 * Using GNAT on Windows::
654 * CONSOLE and WINDOWS subsystems::
656 * Mixed-Language Programming on Windows::
657 * Windows Calling Conventions::
658 * Introduction to Dynamic Link Libraries (DLLs)::
659 * Using DLLs with GNAT::
660 * Building DLLs with GNAT::
661 * GNAT and Windows Resources::
663 * Setting Stack Size from gnatlink::
664 * Setting Heap Size from gnatlink::
671 @node About This Guide
672 @unnumbered About This Guide
676 This guide describes the use of @value{EDITION},
677 a compiler and software development toolset for the full Ada
678 programming language, implemented on OpenVMS for HP's Alpha and
679 Integrity server (I64) platforms.
682 This guide describes the use of @value{EDITION},
683 a compiler and software development
684 toolset for the full Ada programming language.
686 It documents the features of the compiler and tools, and explains
687 how to use them to build Ada applications.
689 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
690 Ada 83 compatibility mode.
691 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
692 but you can override with a compiler switch
693 (@pxref{Compiling Different Versions of Ada})
694 to explicitly specify the language version.
695 Throughout this manual, references to ``Ada'' without a year suffix
696 apply to both the Ada 95 and Ada 2005 versions of the language.
700 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
701 ``GNAT'' in the remainder of this document.
708 * What This Guide Contains::
709 * What You Should Know before Reading This Guide::
710 * Related Information::
714 @node What This Guide Contains
715 @unnumberedsec What This Guide Contains
718 This guide contains the following chapters:
722 @ref{Getting Started with GNAT}, describes how to get started compiling
723 and running Ada programs with the GNAT Ada programming environment.
725 @ref{The GNAT Compilation Model}, describes the compilation model used
729 @ref{Compiling Using gcc}, describes how to compile
730 Ada programs with @command{gcc}, the Ada compiler.
733 @ref{Binding Using gnatbind}, describes how to
734 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
738 @ref{Linking Using gnatlink},
739 describes @command{gnatlink}, a
740 program that provides for linking using the GNAT run-time library to
741 construct a program. @command{gnatlink} can also incorporate foreign language
742 object units into the executable.
745 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
746 utility that automatically determines the set of sources
747 needed by an Ada compilation unit, and executes the necessary compilations
751 @ref{Improving Performance}, shows various techniques for making your
752 Ada program run faster or take less space.
753 It discusses the effect of the compiler's optimization switch and
754 also describes the @command{gnatelim} tool and unused subprogram/data
758 @ref{Renaming Files Using gnatchop}, describes
759 @code{gnatchop}, a utility that allows you to preprocess a file that
760 contains Ada source code, and split it into one or more new files, one
761 for each compilation unit.
764 @ref{Configuration Pragmas}, describes the configuration pragmas
768 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
769 shows how to override the default GNAT file naming conventions,
770 either for an individual unit or globally.
773 @ref{GNAT Project Manager}, describes how to use project files
774 to organize large projects.
777 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
778 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
779 way to navigate through sources.
782 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
783 version of an Ada source file with control over casing, indentation,
784 comment placement, and other elements of program presentation style.
787 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
788 metrics for an Ada source file, such as the number of types and subprograms,
789 and assorted complexity measures.
792 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
793 file name krunching utility, used to handle shortened
794 file names on operating systems with a limit on the length of names.
797 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
798 preprocessor utility that allows a single source file to be used to
799 generate multiple or parameterized source files by means of macro
804 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
805 a tool for rebuilding the GNAT run time with user-supplied
806 configuration pragmas.
810 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
811 utility that displays information about compiled units, including dependences
812 on the corresponding sources files, and consistency of compilations.
815 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
816 to delete files that are produced by the compiler, binder and linker.
820 @ref{GNAT and Libraries}, describes the process of creating and using
821 Libraries with GNAT. It also describes how to recompile the GNAT run-time
825 @ref{Using the GNU make Utility}, describes some techniques for using
826 the GNAT toolset in Makefiles.
830 @ref{Memory Management Issues}, describes some useful predefined storage pools
831 and in particular the GNAT Debug Pool facility, which helps detect incorrect
834 It also describes @command{gnatmem}, a utility that monitors dynamic
835 allocation and deallocation and helps detect ``memory leaks''.
839 @ref{Stack Related Facilities}, describes some useful tools associated with
840 stack checking and analysis.
843 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
844 a utility that checks Ada code against a set of rules.
847 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
848 a utility that generates empty but compilable bodies for library units.
851 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
852 generate automatically Ada bindings from C and C++ headers.
855 @ref{Other Utility Programs}, discusses several other GNAT utilities,
856 including @code{gnathtml}.
860 @ref{Code Coverage and Profiling}, describes how to perform a structural
861 coverage and profile the execution of Ada programs.
865 @ref{Running and Debugging Ada Programs}, describes how to run and debug
870 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
871 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
872 developed by Digital Equipment Corporation and currently supported by HP.}
873 for OpenVMS Alpha. This product was formerly known as DEC Ada,
876 historical compatibility reasons, the relevant libraries still use the
881 @ref{Platform-Specific Information for the Run-Time Libraries},
882 describes the various run-time
883 libraries supported by GNAT on various platforms and explains how to
884 choose a particular library.
887 @ref{Example of Binder Output File}, shows the source code for the binder
888 output file for a sample program.
891 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
892 you deal with elaboration order issues.
895 @ref{Conditional Compilation}, describes how to model conditional compilation,
896 both with Ada in general and with GNAT facilities in particular.
899 @ref{Inline Assembler}, shows how to use the inline assembly facility
903 @ref{Compatibility and Porting Guide}, contains sections on compatibility
904 of GNAT with other Ada development environments (including Ada 83 systems),
905 to assist in porting code from those environments.
909 @ref{Microsoft Windows Topics}, presents information relevant to the
910 Microsoft Windows platform.
914 @c *************************************************
915 @node What You Should Know before Reading This Guide
916 @c *************************************************
917 @unnumberedsec What You Should Know before Reading This Guide
919 @cindex Ada 95 Language Reference Manual
920 @cindex Ada 2005 Language Reference Manual
922 This guide assumes a basic familiarity with the Ada 95 language, as
923 described in the International Standard ANSI/ISO/IEC-8652:1995, January
925 It does not require knowledge of the new features introduced by Ada 2005,
926 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
928 Both reference manuals are included in the GNAT documentation
931 @node Related Information
932 @unnumberedsec Related Information
935 For further information about related tools, refer to the following
940 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
941 Reference Manual}, which contains all reference material for the GNAT
942 implementation of Ada.
946 @cite{Using the GNAT Programming Studio}, which describes the GPS
947 Integrated Development Environment.
950 @cite{GNAT Programming Studio Tutorial}, which introduces the
951 main GPS features through examples.
955 @cite{Ada 95 Reference Manual}, which contains reference
956 material for the Ada 95 programming language.
959 @cite{Ada 2005 Reference Manual}, which contains reference
960 material for the Ada 2005 programming language.
963 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
965 in the GNU:[DOCS] directory,
967 for all details on the use of the GNU source-level debugger.
970 @xref{Top,, The extensible self-documenting text editor, emacs,
973 located in the GNU:[DOCS] directory if the EMACS kit is installed,
975 for full information on the extensible editor and programming
982 @unnumberedsec Conventions
984 @cindex Typographical conventions
987 Following are examples of the typographical and graphic conventions used
992 @code{Functions}, @command{utility program names}, @code{standard names},
996 @option{Option flags}
999 @file{File names}, @samp{button names}, and @samp{field names}.
1002 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1009 @r{[}optional information or parameters@r{]}
1012 Examples are described by text
1014 and then shown this way.
1019 Commands that are entered by the user are preceded in this manual by the
1020 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1021 uses this sequence as a prompt, then the commands will appear exactly as
1022 you see them in the manual. If your system uses some other prompt, then
1023 the command will appear with the @code{$} replaced by whatever prompt
1024 character you are using.
1027 Full file names are shown with the ``@code{/}'' character
1028 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1029 If you are using GNAT on a Windows platform, please note that
1030 the ``@code{\}'' character should be used instead.
1033 @c ****************************
1034 @node Getting Started with GNAT
1035 @chapter Getting Started with GNAT
1038 This chapter describes some simple ways of using GNAT to build
1039 executable Ada programs.
1041 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1042 show how to use the command line environment.
1043 @ref{Introduction to GPS}, provides a brief
1044 introduction to the GNAT Programming Studio, a visually-oriented
1045 Integrated Development Environment for GNAT.
1046 GPS offers a graphical ``look and feel'', support for development in
1047 other programming languages, comprehensive browsing features, and
1048 many other capabilities.
1049 For information on GPS please refer to
1050 @cite{Using the GNAT Programming Studio}.
1055 * Running a Simple Ada Program::
1056 * Running a Program with Multiple Units::
1057 * Using the gnatmake Utility::
1059 * Editing with Emacs::
1062 * Introduction to GPS::
1067 @section Running GNAT
1070 Three steps are needed to create an executable file from an Ada source
1075 The source file(s) must be compiled.
1077 The file(s) must be bound using the GNAT binder.
1079 All appropriate object files must be linked to produce an executable.
1083 All three steps are most commonly handled by using the @command{gnatmake}
1084 utility program that, given the name of the main program, automatically
1085 performs the necessary compilation, binding and linking steps.
1087 @node Running a Simple Ada Program
1088 @section Running a Simple Ada Program
1091 Any text editor may be used to prepare an Ada program.
1093 used, the optional Ada mode may be helpful in laying out the program.)
1095 program text is a normal text file. We will assume in our initial
1096 example that you have used your editor to prepare the following
1097 standard format text file:
1099 @smallexample @c ada
1101 with Ada.Text_IO; use Ada.Text_IO;
1104 Put_Line ("Hello WORLD!");
1110 This file should be named @file{hello.adb}.
1111 With the normal default file naming conventions, GNAT requires
1113 contain a single compilation unit whose file name is the
1115 with periods replaced by hyphens; the
1116 extension is @file{ads} for a
1117 spec and @file{adb} for a body.
1118 You can override this default file naming convention by use of the
1119 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1120 Alternatively, if you want to rename your files according to this default
1121 convention, which is probably more convenient if you will be using GNAT
1122 for all your compilations, then the @code{gnatchop} utility
1123 can be used to generate correctly-named source files
1124 (@pxref{Renaming Files Using gnatchop}).
1126 You can compile the program using the following command (@code{$} is used
1127 as the command prompt in the examples in this document):
1134 @command{gcc} is the command used to run the compiler. This compiler is
1135 capable of compiling programs in several languages, including Ada and
1136 C. It assumes that you have given it an Ada program if the file extension is
1137 either @file{.ads} or @file{.adb}, and it will then call
1138 the GNAT compiler to compile the specified file.
1141 The @option{-c} switch is required. It tells @command{gcc} to only do a
1142 compilation. (For C programs, @command{gcc} can also do linking, but this
1143 capability is not used directly for Ada programs, so the @option{-c}
1144 switch must always be present.)
1147 This compile command generates a file
1148 @file{hello.o}, which is the object
1149 file corresponding to your Ada program. It also generates
1150 an ``Ada Library Information'' file @file{hello.ali},
1151 which contains additional information used to check
1152 that an Ada program is consistent.
1153 To build an executable file,
1154 use @code{gnatbind} to bind the program
1155 and @command{gnatlink} to link it. The
1156 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1157 @file{ALI} file, but the default extension of @file{.ali} can
1158 be omitted. This means that in the most common case, the argument
1159 is simply the name of the main program:
1167 A simpler method of carrying out these steps is to use
1169 a master program that invokes all the required
1170 compilation, binding and linking tools in the correct order. In particular,
1171 @command{gnatmake} automatically recompiles any sources that have been
1172 modified since they were last compiled, or sources that depend
1173 on such modified sources, so that ``version skew'' is avoided.
1174 @cindex Version skew (avoided by @command{gnatmake})
1177 $ gnatmake hello.adb
1181 The result is an executable program called @file{hello}, which can be
1189 assuming that the current directory is on the search path
1190 for executable programs.
1193 and, if all has gone well, you will see
1200 appear in response to this command.
1202 @c ****************************************
1203 @node Running a Program with Multiple Units
1204 @section Running a Program with Multiple Units
1207 Consider a slightly more complicated example that has three files: a
1208 main program, and the spec and body of a package:
1210 @smallexample @c ada
1213 package Greetings is
1218 with Ada.Text_IO; use Ada.Text_IO;
1219 package body Greetings is
1222 Put_Line ("Hello WORLD!");
1225 procedure Goodbye is
1227 Put_Line ("Goodbye WORLD!");
1244 Following the one-unit-per-file rule, place this program in the
1245 following three separate files:
1249 spec of package @code{Greetings}
1252 body of package @code{Greetings}
1255 body of main program
1259 To build an executable version of
1260 this program, we could use four separate steps to compile, bind, and link
1261 the program, as follows:
1265 $ gcc -c greetings.adb
1271 Note that there is no required order of compilation when using GNAT.
1272 In particular it is perfectly fine to compile the main program first.
1273 Also, it is not necessary to compile package specs in the case where
1274 there is an accompanying body; you only need to compile the body. If you want
1275 to submit these files to the compiler for semantic checking and not code
1276 generation, then use the
1277 @option{-gnatc} switch:
1280 $ gcc -c greetings.ads -gnatc
1284 Although the compilation can be done in separate steps as in the
1285 above example, in practice it is almost always more convenient
1286 to use the @command{gnatmake} tool. All you need to know in this case
1287 is the name of the main program's source file. The effect of the above four
1288 commands can be achieved with a single one:
1291 $ gnatmake gmain.adb
1295 In the next section we discuss the advantages of using @command{gnatmake} in
1298 @c *****************************
1299 @node Using the gnatmake Utility
1300 @section Using the @command{gnatmake} Utility
1303 If you work on a program by compiling single components at a time using
1304 @command{gcc}, you typically keep track of the units you modify. In order to
1305 build a consistent system, you compile not only these units, but also any
1306 units that depend on the units you have modified.
1307 For example, in the preceding case,
1308 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1309 you edit @file{greetings.ads}, you must recompile both
1310 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1311 units that depend on @file{greetings.ads}.
1313 @code{gnatbind} will warn you if you forget one of these compilation
1314 steps, so that it is impossible to generate an inconsistent program as a
1315 result of forgetting to do a compilation. Nevertheless it is tedious and
1316 error-prone to keep track of dependencies among units.
1317 One approach to handle the dependency-bookkeeping is to use a
1318 makefile. However, makefiles present maintenance problems of their own:
1319 if the dependencies change as you change the program, you must make
1320 sure that the makefile is kept up-to-date manually, which is also an
1321 error-prone process.
1323 The @command{gnatmake} utility takes care of these details automatically.
1324 Invoke it using either one of the following forms:
1327 $ gnatmake gmain.adb
1328 $ gnatmake ^gmain^GMAIN^
1332 The argument is the name of the file containing the main program;
1333 you may omit the extension. @command{gnatmake}
1334 examines the environment, automatically recompiles any files that need
1335 recompiling, and binds and links the resulting set of object files,
1336 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1337 In a large program, it
1338 can be extremely helpful to use @command{gnatmake}, because working out by hand
1339 what needs to be recompiled can be difficult.
1341 Note that @command{gnatmake}
1342 takes into account all the Ada rules that
1343 establish dependencies among units. These include dependencies that result
1344 from inlining subprogram bodies, and from
1345 generic instantiation. Unlike some other
1346 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1347 found by the compiler on a previous compilation, which may possibly
1348 be wrong when sources change. @command{gnatmake} determines the exact set of
1349 dependencies from scratch each time it is run.
1352 @node Editing with Emacs
1353 @section Editing with Emacs
1357 Emacs is an extensible self-documenting text editor that is available in a
1358 separate VMSINSTAL kit.
1360 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1361 click on the Emacs Help menu and run the Emacs Tutorial.
1362 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1363 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1365 Documentation on Emacs and other tools is available in Emacs under the
1366 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1367 use the middle mouse button to select a topic (e.g.@: Emacs).
1369 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1370 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1371 get to the Emacs manual.
1372 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1375 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1376 which is sufficiently extensible to provide for a complete programming
1377 environment and shell for the sophisticated user.
1381 @node Introduction to GPS
1382 @section Introduction to GPS
1383 @cindex GPS (GNAT Programming Studio)
1384 @cindex GNAT Programming Studio (GPS)
1386 Although the command line interface (@command{gnatmake}, etc.) alone
1387 is sufficient, a graphical Interactive Development
1388 Environment can make it easier for you to compose, navigate, and debug
1389 programs. This section describes the main features of GPS
1390 (``GNAT Programming Studio''), the GNAT graphical IDE.
1391 You will see how to use GPS to build and debug an executable, and
1392 you will also learn some of the basics of the GNAT ``project'' facility.
1394 GPS enables you to do much more than is presented here;
1395 e.g., you can produce a call graph, interface to a third-party
1396 Version Control System, and inspect the generated assembly language
1398 Indeed, GPS also supports languages other than Ada.
1399 Such additional information, and an explanation of all of the GPS menu
1400 items. may be found in the on-line help, which includes
1401 a user's guide and a tutorial (these are also accessible from the GNAT
1405 * Building a New Program with GPS::
1406 * Simple Debugging with GPS::
1409 @node Building a New Program with GPS
1410 @subsection Building a New Program with GPS
1412 GPS invokes the GNAT compilation tools using information
1413 contained in a @emph{project} (also known as a @emph{project file}):
1414 a collection of properties such
1415 as source directories, identities of main subprograms, tool switches, etc.,
1416 and their associated values.
1417 See @ref{GNAT Project Manager} for details.
1418 In order to run GPS, you will need to either create a new project
1419 or else open an existing one.
1421 This section will explain how you can use GPS to create a project,
1422 to associate Ada source files with a project, and to build and run
1426 @item @emph{Creating a project}
1428 Invoke GPS, either from the command line or the platform's IDE.
1429 After it starts, GPS will display a ``Welcome'' screen with three
1434 @code{Start with default project in directory}
1437 @code{Create new project with wizard}
1440 @code{Open existing project}
1444 Select @code{Create new project with wizard} and press @code{OK}.
1445 A new window will appear. In the text box labeled with
1446 @code{Enter the name of the project to create}, type @file{sample}
1447 as the project name.
1448 In the next box, browse to choose the directory in which you
1449 would like to create the project file.
1450 After selecting an appropriate directory, press @code{Forward}.
1452 A window will appear with the title
1453 @code{Version Control System Configuration}.
1454 Simply press @code{Forward}.
1456 A window will appear with the title
1457 @code{Please select the source directories for this project}.
1458 The directory that you specified for the project file will be selected
1459 by default as the one to use for sources; simply press @code{Forward}.
1461 A window will appear with the title
1462 @code{Please select the build directory for this project}.
1463 The directory that you specified for the project file will be selected
1464 by default for object files and executables;
1465 simply press @code{Forward}.
1467 A window will appear with the title
1468 @code{Please select the main units for this project}.
1469 You will supply this information later, after creating the source file.
1470 Simply press @code{Forward} for now.
1472 A window will appear with the title
1473 @code{Please select the switches to build the project}.
1474 Press @code{Apply}. This will create a project file named
1475 @file{sample.prj} in the directory that you had specified.
1477 @item @emph{Creating and saving the source file}
1479 After you create the new project, a GPS window will appear, which is
1480 partitioned into two main sections:
1484 A @emph{Workspace area}, initially greyed out, which you will use for
1485 creating and editing source files
1488 Directly below, a @emph{Messages area}, which initially displays a
1489 ``Welcome'' message.
1490 (If the Messages area is not visible, drag its border upward to expand it.)
1494 Select @code{File} on the menu bar, and then the @code{New} command.
1495 The Workspace area will become white, and you can now
1496 enter the source program explicitly.
1497 Type the following text
1499 @smallexample @c ada
1501 with Ada.Text_IO; use Ada.Text_IO;
1504 Put_Line("Hello from GPS!");
1510 Select @code{File}, then @code{Save As}, and enter the source file name
1512 The file will be saved in the same directory you specified as the
1513 location of the default project file.
1515 @item @emph{Updating the project file}
1517 You need to add the new source file to the project.
1519 the @code{Project} menu and then @code{Edit project properties}.
1520 Click the @code{Main files} tab on the left, and then the
1522 Choose @file{hello.adb} from the list, and press @code{Open}.
1523 The project settings window will reflect this action.
1526 @item @emph{Building and running the program}
1528 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1529 and select @file{hello.adb}.
1530 The Messages window will display the resulting invocations of @command{gcc},
1531 @command{gnatbind}, and @command{gnatlink}
1532 (reflecting the default switch settings from the
1533 project file that you created) and then a ``successful compilation/build''
1536 To run the program, choose the @code{Build} menu, then @code{Run}, and
1537 select @command{hello}.
1538 An @emph{Arguments Selection} window will appear.
1539 There are no command line arguments, so just click @code{OK}.
1541 The Messages window will now display the program's output (the string
1542 @code{Hello from GPS}), and at the bottom of the GPS window a status
1543 update is displayed (@code{Run: hello}).
1544 Close the GPS window (or select @code{File}, then @code{Exit}) to
1545 terminate this GPS session.
1548 @node Simple Debugging with GPS
1549 @subsection Simple Debugging with GPS
1551 This section illustrates basic debugging techniques (setting breakpoints,
1552 examining/modifying variables, single stepping).
1555 @item @emph{Opening a project}
1557 Start GPS and select @code{Open existing project}; browse to
1558 specify the project file @file{sample.prj} that you had created in the
1561 @item @emph{Creating a source file}
1563 Select @code{File}, then @code{New}, and type in the following program:
1565 @smallexample @c ada
1567 with Ada.Text_IO; use Ada.Text_IO;
1568 procedure Example is
1569 Line : String (1..80);
1572 Put_Line("Type a line of text at each prompt; an empty line to exit");
1576 Put_Line (Line (1..N) );
1584 Select @code{File}, then @code{Save as}, and enter the file name
1587 @item @emph{Updating the project file}
1589 Add @code{Example} as a new main unit for the project:
1592 Select @code{Project}, then @code{Edit Project Properties}.
1595 Select the @code{Main files} tab, click @code{Add}, then
1596 select the file @file{example.adb} from the list, and
1598 You will see the file name appear in the list of main units
1604 @item @emph{Building/running the executable}
1606 To build the executable
1607 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1609 Run the program to see its effect (in the Messages area).
1610 Each line that you enter is displayed; an empty line will
1611 cause the loop to exit and the program to terminate.
1613 @item @emph{Debugging the program}
1615 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1616 which are required for debugging, are on by default when you create
1618 Thus unless you intentionally remove these settings, you will be able
1619 to debug any program that you develop using GPS.
1622 @item @emph{Initializing}
1624 Select @code{Debug}, then @code{Initialize}, then @file{example}
1626 @item @emph{Setting a breakpoint}
1628 After performing the initialization step, you will observe a small
1629 icon to the right of each line number.
1630 This serves as a toggle for breakpoints; clicking the icon will
1631 set a breakpoint at the corresponding line (the icon will change to
1632 a red circle with an ``x''), and clicking it again
1633 will remove the breakpoint / reset the icon.
1635 For purposes of this example, set a breakpoint at line 10 (the
1636 statement @code{Put_Line@ (Line@ (1..N));}
1638 @item @emph{Starting program execution}
1640 Select @code{Debug}, then @code{Run}. When the
1641 @code{Program Arguments} window appears, click @code{OK}.
1642 A console window will appear; enter some line of text,
1643 e.g.@: @code{abcde}, at the prompt.
1644 The program will pause execution when it gets to the
1645 breakpoint, and the corresponding line is highlighted.
1647 @item @emph{Examining a variable}
1649 Move the mouse over one of the occurrences of the variable @code{N}.
1650 You will see the value (5) displayed, in ``tool tip'' fashion.
1651 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1652 You will see information about @code{N} appear in the @code{Debugger Data}
1653 pane, showing the value as 5.
1655 @item @emph{Assigning a new value to a variable}
1657 Right click on the @code{N} in the @code{Debugger Data} pane, and
1658 select @code{Set value of N}.
1659 When the input window appears, enter the value @code{4} and click
1661 This value does not automatically appear in the @code{Debugger Data}
1662 pane; to see it, right click again on the @code{N} in the
1663 @code{Debugger Data} pane and select @code{Update value}.
1664 The new value, 4, will appear in red.
1666 @item @emph{Single stepping}
1668 Select @code{Debug}, then @code{Next}.
1669 This will cause the next statement to be executed, in this case the
1670 call of @code{Put_Line} with the string slice.
1671 Notice in the console window that the displayed string is simply
1672 @code{abcd} and not @code{abcde} which you had entered.
1673 This is because the upper bound of the slice is now 4 rather than 5.
1675 @item @emph{Removing a breakpoint}
1677 Toggle the breakpoint icon at line 10.
1679 @item @emph{Resuming execution from a breakpoint}
1681 Select @code{Debug}, then @code{Continue}.
1682 The program will reach the next iteration of the loop, and
1683 wait for input after displaying the prompt.
1684 This time, just hit the @kbd{Enter} key.
1685 The value of @code{N} will be 0, and the program will terminate.
1686 The console window will disappear.
1691 @node The GNAT Compilation Model
1692 @chapter The GNAT Compilation Model
1693 @cindex GNAT compilation model
1694 @cindex Compilation model
1697 * Source Representation::
1698 * Foreign Language Representation::
1699 * File Naming Rules::
1700 * Using Other File Names::
1701 * Alternative File Naming Schemes::
1702 * Generating Object Files::
1703 * Source Dependencies::
1704 * The Ada Library Information Files::
1705 * Binding an Ada Program::
1706 * Mixed Language Programming::
1708 * Building Mixed Ada & C++ Programs::
1709 * Comparison between GNAT and C/C++ Compilation Models::
1711 * Comparison between GNAT and Conventional Ada Library Models::
1713 * Placement of temporary files::
1718 This chapter describes the compilation model used by GNAT. Although
1719 similar to that used by other languages, such as C and C++, this model
1720 is substantially different from the traditional Ada compilation models,
1721 which are based on a library. The model is initially described without
1722 reference to the library-based model. If you have not previously used an
1723 Ada compiler, you need only read the first part of this chapter. The
1724 last section describes and discusses the differences between the GNAT
1725 model and the traditional Ada compiler models. If you have used other
1726 Ada compilers, this section will help you to understand those
1727 differences, and the advantages of the GNAT model.
1729 @node Source Representation
1730 @section Source Representation
1734 Ada source programs are represented in standard text files, using
1735 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1736 7-bit ASCII set, plus additional characters used for
1737 representing foreign languages (@pxref{Foreign Language Representation}
1738 for support of non-USA character sets). The format effector characters
1739 are represented using their standard ASCII encodings, as follows:
1744 Vertical tab, @code{16#0B#}
1748 Horizontal tab, @code{16#09#}
1752 Carriage return, @code{16#0D#}
1756 Line feed, @code{16#0A#}
1760 Form feed, @code{16#0C#}
1764 Source files are in standard text file format. In addition, GNAT will
1765 recognize a wide variety of stream formats, in which the end of
1766 physical lines is marked by any of the following sequences:
1767 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1768 in accommodating files that are imported from other operating systems.
1770 @cindex End of source file
1771 @cindex Source file, end
1773 The end of a source file is normally represented by the physical end of
1774 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1775 recognized as signalling the end of the source file. Again, this is
1776 provided for compatibility with other operating systems where this
1777 code is used to represent the end of file.
1779 Each file contains a single Ada compilation unit, including any pragmas
1780 associated with the unit. For example, this means you must place a
1781 package declaration (a package @dfn{spec}) and the corresponding body in
1782 separate files. An Ada @dfn{compilation} (which is a sequence of
1783 compilation units) is represented using a sequence of files. Similarly,
1784 you will place each subunit or child unit in a separate file.
1786 @node Foreign Language Representation
1787 @section Foreign Language Representation
1790 GNAT supports the standard character sets defined in Ada as well as
1791 several other non-standard character sets for use in localized versions
1792 of the compiler (@pxref{Character Set Control}).
1795 * Other 8-Bit Codes::
1796 * Wide Character Encodings::
1804 The basic character set is Latin-1. This character set is defined by ISO
1805 standard 8859, part 1. The lower half (character codes @code{16#00#}
1806 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1807 is used to represent additional characters. These include extended letters
1808 used by European languages, such as French accents, the vowels with umlauts
1809 used in German, and the extra letter A-ring used in Swedish.
1811 @findex Ada.Characters.Latin_1
1812 For a complete list of Latin-1 codes and their encodings, see the source
1813 file of library unit @code{Ada.Characters.Latin_1} in file
1814 @file{a-chlat1.ads}.
1815 You may use any of these extended characters freely in character or
1816 string literals. In addition, the extended characters that represent
1817 letters can be used in identifiers.
1819 @node Other 8-Bit Codes
1820 @subsection Other 8-Bit Codes
1823 GNAT also supports several other 8-bit coding schemes:
1826 @item ISO 8859-2 (Latin-2)
1829 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1832 @item ISO 8859-3 (Latin-3)
1835 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1838 @item ISO 8859-4 (Latin-4)
1841 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1844 @item ISO 8859-5 (Cyrillic)
1847 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1848 lowercase equivalence.
1850 @item ISO 8859-15 (Latin-9)
1853 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1854 lowercase equivalence
1856 @item IBM PC (code page 437)
1857 @cindex code page 437
1858 This code page is the normal default for PCs in the U.S. It corresponds
1859 to the original IBM PC character set. This set has some, but not all, of
1860 the extended Latin-1 letters, but these letters do not have the same
1861 encoding as Latin-1. In this mode, these letters are allowed in
1862 identifiers with uppercase and lowercase equivalence.
1864 @item IBM PC (code page 850)
1865 @cindex code page 850
1866 This code page is a modification of 437 extended to include all the
1867 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1868 mode, all these letters are allowed in identifiers with uppercase and
1869 lowercase equivalence.
1871 @item Full Upper 8-bit
1872 Any character in the range 80-FF allowed in identifiers, and all are
1873 considered distinct. In other words, there are no uppercase and lowercase
1874 equivalences in this range. This is useful in conjunction with
1875 certain encoding schemes used for some foreign character sets (e.g.,
1876 the typical method of representing Chinese characters on the PC).
1879 No upper-half characters in the range 80-FF are allowed in identifiers.
1880 This gives Ada 83 compatibility for identifier names.
1884 For precise data on the encodings permitted, and the uppercase and lowercase
1885 equivalences that are recognized, see the file @file{csets.adb} in
1886 the GNAT compiler sources. You will need to obtain a full source release
1887 of GNAT to obtain this file.
1889 @node Wide Character Encodings
1890 @subsection Wide Character Encodings
1893 GNAT allows wide character codes to appear in character and string
1894 literals, and also optionally in identifiers, by means of the following
1895 possible encoding schemes:
1900 In this encoding, a wide character is represented by the following five
1908 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1909 characters (using uppercase letters) of the wide character code. For
1910 example, ESC A345 is used to represent the wide character with code
1912 This scheme is compatible with use of the full Wide_Character set.
1914 @item Upper-Half Coding
1915 @cindex Upper-Half Coding
1916 The wide character with encoding @code{16#abcd#} where the upper bit is on
1917 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1918 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1919 character, but is not required to be in the upper half. This method can
1920 be also used for shift-JIS or EUC, where the internal coding matches the
1923 @item Shift JIS Coding
1924 @cindex Shift JIS Coding
1925 A wide character is represented by a two-character sequence,
1927 @code{16#cd#}, with the restrictions described for upper-half encoding as
1928 described above. The internal character code is the corresponding JIS
1929 character according to the standard algorithm for Shift-JIS
1930 conversion. Only characters defined in the JIS code set table can be
1931 used with this encoding method.
1935 A wide character is represented by a two-character sequence
1937 @code{16#cd#}, with both characters being in the upper half. The internal
1938 character code is the corresponding JIS character according to the EUC
1939 encoding algorithm. Only characters defined in the JIS code set table
1940 can be used with this encoding method.
1943 A wide character is represented using
1944 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1945 10646-1/Am.2. Depending on the character value, the representation
1946 is a one, two, or three byte sequence:
1951 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1952 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1953 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1958 where the @var{xxx} bits correspond to the left-padded bits of the
1959 16-bit character value. Note that all lower half ASCII characters
1960 are represented as ASCII bytes and all upper half characters and
1961 other wide characters are represented as sequences of upper-half
1962 (The full UTF-8 scheme allows for encoding 31-bit characters as
1963 6-byte sequences, but in this implementation, all UTF-8 sequences
1964 of four or more bytes length will be treated as illegal).
1965 @item Brackets Coding
1966 In this encoding, a wide character is represented by the following eight
1974 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1975 characters (using uppercase letters) of the wide character code. For
1976 example, [``A345''] is used to represent the wide character with code
1977 @code{16#A345#}. It is also possible (though not required) to use the
1978 Brackets coding for upper half characters. For example, the code
1979 @code{16#A3#} can be represented as @code{[``A3'']}.
1981 This scheme is compatible with use of the full Wide_Character set,
1982 and is also the method used for wide character encoding in the standard
1983 ACVC (Ada Compiler Validation Capability) test suite distributions.
1988 Note: Some of these coding schemes do not permit the full use of the
1989 Ada character set. For example, neither Shift JIS, nor EUC allow the
1990 use of the upper half of the Latin-1 set.
1992 @node File Naming Rules
1993 @section File Naming Rules
1996 The default file name is determined by the name of the unit that the
1997 file contains. The name is formed by taking the full expanded name of
1998 the unit and replacing the separating dots with hyphens and using
1999 ^lowercase^uppercase^ for all letters.
2001 An exception arises if the file name generated by the above rules starts
2002 with one of the characters
2004 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2007 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2009 and the second character is a
2010 minus. In this case, the character ^tilde^dollar sign^ is used in place
2011 of the minus. The reason for this special rule is to avoid clashes with
2012 the standard names for child units of the packages System, Ada,
2013 Interfaces, and GNAT, which use the prefixes
2015 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2018 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2022 The file extension is @file{.ads} for a spec and
2023 @file{.adb} for a body. The following list shows some
2024 examples of these rules.
2031 @item arith_functions.ads
2032 Arith_Functions (package spec)
2033 @item arith_functions.adb
2034 Arith_Functions (package body)
2036 Func.Spec (child package spec)
2038 Func.Spec (child package body)
2040 Sub (subunit of Main)
2041 @item ^a~bad.adb^A$BAD.ADB^
2042 A.Bad (child package body)
2046 Following these rules can result in excessively long
2047 file names if corresponding
2048 unit names are long (for example, if child units or subunits are
2049 heavily nested). An option is available to shorten such long file names
2050 (called file name ``krunching''). This may be particularly useful when
2051 programs being developed with GNAT are to be used on operating systems
2052 with limited file name lengths. @xref{Using gnatkr}.
2054 Of course, no file shortening algorithm can guarantee uniqueness over
2055 all possible unit names; if file name krunching is used, it is your
2056 responsibility to ensure no name clashes occur. Alternatively you
2057 can specify the exact file names that you want used, as described
2058 in the next section. Finally, if your Ada programs are migrating from a
2059 compiler with a different naming convention, you can use the gnatchop
2060 utility to produce source files that follow the GNAT naming conventions.
2061 (For details @pxref{Renaming Files Using gnatchop}.)
2063 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2064 systems, case is not significant. So for example on @code{Windows XP}
2065 if the canonical name is @code{main-sub.adb}, you can use the file name
2066 @code{Main-Sub.adb} instead. However, case is significant for other
2067 operating systems, so for example, if you want to use other than
2068 canonically cased file names on a Unix system, you need to follow
2069 the procedures described in the next section.
2071 @node Using Other File Names
2072 @section Using Other File Names
2076 In the previous section, we have described the default rules used by
2077 GNAT to determine the file name in which a given unit resides. It is
2078 often convenient to follow these default rules, and if you follow them,
2079 the compiler knows without being explicitly told where to find all
2082 However, in some cases, particularly when a program is imported from
2083 another Ada compiler environment, it may be more convenient for the
2084 programmer to specify which file names contain which units. GNAT allows
2085 arbitrary file names to be used by means of the Source_File_Name pragma.
2086 The form of this pragma is as shown in the following examples:
2087 @cindex Source_File_Name pragma
2089 @smallexample @c ada
2091 pragma Source_File_Name (My_Utilities.Stacks,
2092 Spec_File_Name => "myutilst_a.ada");
2093 pragma Source_File_name (My_Utilities.Stacks,
2094 Body_File_Name => "myutilst.ada");
2099 As shown in this example, the first argument for the pragma is the unit
2100 name (in this example a child unit). The second argument has the form
2101 of a named association. The identifier
2102 indicates whether the file name is for a spec or a body;
2103 the file name itself is given by a string literal.
2105 The source file name pragma is a configuration pragma, which means that
2106 normally it will be placed in the @file{gnat.adc}
2107 file used to hold configuration
2108 pragmas that apply to a complete compilation environment.
2109 For more details on how the @file{gnat.adc} file is created and used
2110 see @ref{Handling of Configuration Pragmas}.
2111 @cindex @file{gnat.adc}
2114 GNAT allows completely arbitrary file names to be specified using the
2115 source file name pragma. However, if the file name specified has an
2116 extension other than @file{.ads} or @file{.adb} it is necessary to use
2117 a special syntax when compiling the file. The name in this case must be
2118 preceded by the special sequence @option{-x} followed by a space and the name
2119 of the language, here @code{ada}, as in:
2122 $ gcc -c -x ada peculiar_file_name.sim
2127 @command{gnatmake} handles non-standard file names in the usual manner (the
2128 non-standard file name for the main program is simply used as the
2129 argument to gnatmake). Note that if the extension is also non-standard,
2130 then it must be included in the @command{gnatmake} command, it may not
2133 @node Alternative File Naming Schemes
2134 @section Alternative File Naming Schemes
2135 @cindex File naming schemes, alternative
2138 In the previous section, we described the use of the @code{Source_File_Name}
2139 pragma to allow arbitrary names to be assigned to individual source files.
2140 However, this approach requires one pragma for each file, and especially in
2141 large systems can result in very long @file{gnat.adc} files, and also create
2142 a maintenance problem.
2144 GNAT also provides a facility for specifying systematic file naming schemes
2145 other than the standard default naming scheme previously described. An
2146 alternative scheme for naming is specified by the use of
2147 @code{Source_File_Name} pragmas having the following format:
2148 @cindex Source_File_Name pragma
2150 @smallexample @c ada
2151 pragma Source_File_Name (
2152 Spec_File_Name => FILE_NAME_PATTERN
2153 @r{[},Casing => CASING_SPEC@r{]}
2154 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2156 pragma Source_File_Name (
2157 Body_File_Name => FILE_NAME_PATTERN
2158 @r{[},Casing => CASING_SPEC@r{]}
2159 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2161 pragma Source_File_Name (
2162 Subunit_File_Name => FILE_NAME_PATTERN
2163 @r{[},Casing => CASING_SPEC@r{]}
2164 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2166 FILE_NAME_PATTERN ::= STRING_LITERAL
2167 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2171 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2172 It contains a single asterisk character, and the unit name is substituted
2173 systematically for this asterisk. The optional parameter
2174 @code{Casing} indicates
2175 whether the unit name is to be all upper-case letters, all lower-case letters,
2176 or mixed-case. If no
2177 @code{Casing} parameter is used, then the default is all
2178 ^lower-case^upper-case^.
2180 The optional @code{Dot_Replacement} string is used to replace any periods
2181 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2182 argument is used then separating dots appear unchanged in the resulting
2184 Although the above syntax indicates that the
2185 @code{Casing} argument must appear
2186 before the @code{Dot_Replacement} argument, but it
2187 is also permissible to write these arguments in the opposite order.
2189 As indicated, it is possible to specify different naming schemes for
2190 bodies, specs, and subunits. Quite often the rule for subunits is the
2191 same as the rule for bodies, in which case, there is no need to give
2192 a separate @code{Subunit_File_Name} rule, and in this case the
2193 @code{Body_File_name} rule is used for subunits as well.
2195 The separate rule for subunits can also be used to implement the rather
2196 unusual case of a compilation environment (e.g.@: a single directory) which
2197 contains a subunit and a child unit with the same unit name. Although
2198 both units cannot appear in the same partition, the Ada Reference Manual
2199 allows (but does not require) the possibility of the two units coexisting
2200 in the same environment.
2202 The file name translation works in the following steps:
2207 If there is a specific @code{Source_File_Name} pragma for the given unit,
2208 then this is always used, and any general pattern rules are ignored.
2211 If there is a pattern type @code{Source_File_Name} pragma that applies to
2212 the unit, then the resulting file name will be used if the file exists. If
2213 more than one pattern matches, the latest one will be tried first, and the
2214 first attempt resulting in a reference to a file that exists will be used.
2217 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2218 for which the corresponding file exists, then the standard GNAT default
2219 naming rules are used.
2224 As an example of the use of this mechanism, consider a commonly used scheme
2225 in which file names are all lower case, with separating periods copied
2226 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2227 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2230 @smallexample @c ada
2231 pragma Source_File_Name
2232 (Spec_File_Name => "*.1.ada");
2233 pragma Source_File_Name
2234 (Body_File_Name => "*.2.ada");
2238 The default GNAT scheme is actually implemented by providing the following
2239 default pragmas internally:
2241 @smallexample @c ada
2242 pragma Source_File_Name
2243 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2244 pragma Source_File_Name
2245 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2249 Our final example implements a scheme typically used with one of the
2250 Ada 83 compilers, where the separator character for subunits was ``__''
2251 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2252 by adding @file{.ADA}, and subunits by
2253 adding @file{.SEP}. All file names were
2254 upper case. Child units were not present of course since this was an
2255 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2256 the same double underscore separator for child units.
2258 @smallexample @c ada
2259 pragma Source_File_Name
2260 (Spec_File_Name => "*_.ADA",
2261 Dot_Replacement => "__",
2262 Casing = Uppercase);
2263 pragma Source_File_Name
2264 (Body_File_Name => "*.ADA",
2265 Dot_Replacement => "__",
2266 Casing = Uppercase);
2267 pragma Source_File_Name
2268 (Subunit_File_Name => "*.SEP",
2269 Dot_Replacement => "__",
2270 Casing = Uppercase);
2273 @node Generating Object Files
2274 @section Generating Object Files
2277 An Ada program consists of a set of source files, and the first step in
2278 compiling the program is to generate the corresponding object files.
2279 These are generated by compiling a subset of these source files.
2280 The files you need to compile are the following:
2284 If a package spec has no body, compile the package spec to produce the
2285 object file for the package.
2288 If a package has both a spec and a body, compile the body to produce the
2289 object file for the package. The source file for the package spec need
2290 not be compiled in this case because there is only one object file, which
2291 contains the code for both the spec and body of the package.
2294 For a subprogram, compile the subprogram body to produce the object file
2295 for the subprogram. The spec, if one is present, is as usual in a
2296 separate file, and need not be compiled.
2300 In the case of subunits, only compile the parent unit. A single object
2301 file is generated for the entire subunit tree, which includes all the
2305 Compile child units independently of their parent units
2306 (though, of course, the spec of all the ancestor unit must be present in order
2307 to compile a child unit).
2311 Compile generic units in the same manner as any other units. The object
2312 files in this case are small dummy files that contain at most the
2313 flag used for elaboration checking. This is because GNAT always handles generic
2314 instantiation by means of macro expansion. However, it is still necessary to
2315 compile generic units, for dependency checking and elaboration purposes.
2319 The preceding rules describe the set of files that must be compiled to
2320 generate the object files for a program. Each object file has the same
2321 name as the corresponding source file, except that the extension is
2324 You may wish to compile other files for the purpose of checking their
2325 syntactic and semantic correctness. For example, in the case where a
2326 package has a separate spec and body, you would not normally compile the
2327 spec. However, it is convenient in practice to compile the spec to make
2328 sure it is error-free before compiling clients of this spec, because such
2329 compilations will fail if there is an error in the spec.
2331 GNAT provides an option for compiling such files purely for the
2332 purposes of checking correctness; such compilations are not required as
2333 part of the process of building a program. To compile a file in this
2334 checking mode, use the @option{-gnatc} switch.
2336 @node Source Dependencies
2337 @section Source Dependencies
2340 A given object file clearly depends on the source file which is compiled
2341 to produce it. Here we are using @dfn{depends} in the sense of a typical
2342 @code{make} utility; in other words, an object file depends on a source
2343 file if changes to the source file require the object file to be
2345 In addition to this basic dependency, a given object may depend on
2346 additional source files as follows:
2350 If a file being compiled @code{with}'s a unit @var{X}, the object file
2351 depends on the file containing the spec of unit @var{X}. This includes
2352 files that are @code{with}'ed implicitly either because they are parents
2353 of @code{with}'ed child units or they are run-time units required by the
2354 language constructs used in a particular unit.
2357 If a file being compiled instantiates a library level generic unit, the
2358 object file depends on both the spec and body files for this generic
2362 If a file being compiled instantiates a generic unit defined within a
2363 package, the object file depends on the body file for the package as
2364 well as the spec file.
2368 @cindex @option{-gnatn} switch
2369 If a file being compiled contains a call to a subprogram for which
2370 pragma @code{Inline} applies and inlining is activated with the
2371 @option{-gnatn} switch, the object file depends on the file containing the
2372 body of this subprogram as well as on the file containing the spec. Note
2373 that for inlining to actually occur as a result of the use of this switch,
2374 it is necessary to compile in optimizing mode.
2376 @cindex @option{-gnatN} switch
2377 The use of @option{-gnatN} activates inlining optimization
2378 that is performed by the front end of the compiler. This inlining does
2379 not require that the code generation be optimized. Like @option{-gnatn},
2380 the use of this switch generates additional dependencies.
2382 When using a gcc-based back end (in practice this means using any version
2383 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2384 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2385 Historically front end inlining was more extensive than the gcc back end
2386 inlining, but that is no longer the case.
2389 If an object file @file{O} depends on the proper body of a subunit through
2390 inlining or instantiation, it depends on the parent unit of the subunit.
2391 This means that any modification of the parent unit or one of its subunits
2392 affects the compilation of @file{O}.
2395 The object file for a parent unit depends on all its subunit body files.
2398 The previous two rules meant that for purposes of computing dependencies and
2399 recompilation, a body and all its subunits are treated as an indivisible whole.
2402 These rules are applied transitively: if unit @code{A} @code{with}'s
2403 unit @code{B}, whose elaboration calls an inlined procedure in package
2404 @code{C}, the object file for unit @code{A} will depend on the body of
2405 @code{C}, in file @file{c.adb}.
2407 The set of dependent files described by these rules includes all the
2408 files on which the unit is semantically dependent, as dictated by the
2409 Ada language standard. However, it is a superset of what the
2410 standard describes, because it includes generic, inline, and subunit
2413 An object file must be recreated by recompiling the corresponding source
2414 file if any of the source files on which it depends are modified. For
2415 example, if the @code{make} utility is used to control compilation,
2416 the rule for an Ada object file must mention all the source files on
2417 which the object file depends, according to the above definition.
2418 The determination of the necessary
2419 recompilations is done automatically when one uses @command{gnatmake}.
2422 @node The Ada Library Information Files
2423 @section The Ada Library Information Files
2424 @cindex Ada Library Information files
2425 @cindex @file{ALI} files
2428 Each compilation actually generates two output files. The first of these
2429 is the normal object file that has a @file{.o} extension. The second is a
2430 text file containing full dependency information. It has the same
2431 name as the source file, but an @file{.ali} extension.
2432 This file is known as the Ada Library Information (@file{ALI}) file.
2433 The following information is contained in the @file{ALI} file.
2437 Version information (indicates which version of GNAT was used to compile
2438 the unit(s) in question)
2441 Main program information (including priority and time slice settings,
2442 as well as the wide character encoding used during compilation).
2445 List of arguments used in the @command{gcc} command for the compilation
2448 Attributes of the unit, including configuration pragmas used, an indication
2449 of whether the compilation was successful, exception model used etc.
2452 A list of relevant restrictions applying to the unit (used for consistency)
2456 Categorization information (e.g.@: use of pragma @code{Pure}).
2459 Information on all @code{with}'ed units, including presence of
2460 @code{Elaborate} or @code{Elaborate_All} pragmas.
2463 Information from any @code{Linker_Options} pragmas used in the unit
2466 Information on the use of @code{Body_Version} or @code{Version}
2467 attributes in the unit.
2470 Dependency information. This is a list of files, together with
2471 time stamp and checksum information. These are files on which
2472 the unit depends in the sense that recompilation is required
2473 if any of these units are modified.
2476 Cross-reference data. Contains information on all entities referenced
2477 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2478 provide cross-reference information.
2483 For a full detailed description of the format of the @file{ALI} file,
2484 see the source of the body of unit @code{Lib.Writ}, contained in file
2485 @file{lib-writ.adb} in the GNAT compiler sources.
2487 @node Binding an Ada Program
2488 @section Binding an Ada Program
2491 When using languages such as C and C++, once the source files have been
2492 compiled the only remaining step in building an executable program
2493 is linking the object modules together. This means that it is possible to
2494 link an inconsistent version of a program, in which two units have
2495 included different versions of the same header.
2497 The rules of Ada do not permit such an inconsistent program to be built.
2498 For example, if two clients have different versions of the same package,
2499 it is illegal to build a program containing these two clients.
2500 These rules are enforced by the GNAT binder, which also determines an
2501 elaboration order consistent with the Ada rules.
2503 The GNAT binder is run after all the object files for a program have
2504 been created. It is given the name of the main program unit, and from
2505 this it determines the set of units required by the program, by reading the
2506 corresponding ALI files. It generates error messages if the program is
2507 inconsistent or if no valid order of elaboration exists.
2509 If no errors are detected, the binder produces a main program, in Ada by
2510 default, that contains calls to the elaboration procedures of those
2511 compilation unit that require them, followed by
2512 a call to the main program. This Ada program is compiled to generate the
2513 object file for the main program. The name of
2514 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2515 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2518 Finally, the linker is used to build the resulting executable program,
2519 using the object from the main program from the bind step as well as the
2520 object files for the Ada units of the program.
2522 @node Mixed Language Programming
2523 @section Mixed Language Programming
2524 @cindex Mixed Language Programming
2527 This section describes how to develop a mixed-language program,
2528 specifically one that comprises units in both Ada and C.
2531 * Interfacing to C::
2532 * Calling Conventions::
2535 @node Interfacing to C
2536 @subsection Interfacing to C
2538 Interfacing Ada with a foreign language such as C involves using
2539 compiler directives to import and/or export entity definitions in each
2540 language---using @code{extern} statements in C, for instance, and the
2541 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2542 A full treatment of these topics is provided in Appendix B, section 1
2543 of the Ada Reference Manual.
2545 There are two ways to build a program using GNAT that contains some Ada
2546 sources and some foreign language sources, depending on whether or not
2547 the main subprogram is written in Ada. Here is a source example with
2548 the main subprogram in Ada:
2554 void print_num (int num)
2556 printf ("num is %d.\n", num);
2562 /* num_from_Ada is declared in my_main.adb */
2563 extern int num_from_Ada;
2567 return num_from_Ada;
2571 @smallexample @c ada
2573 procedure My_Main is
2575 -- Declare then export an Integer entity called num_from_Ada
2576 My_Num : Integer := 10;
2577 pragma Export (C, My_Num, "num_from_Ada");
2579 -- Declare an Ada function spec for Get_Num, then use
2580 -- C function get_num for the implementation.
2581 function Get_Num return Integer;
2582 pragma Import (C, Get_Num, "get_num");
2584 -- Declare an Ada procedure spec for Print_Num, then use
2585 -- C function print_num for the implementation.
2586 procedure Print_Num (Num : Integer);
2587 pragma Import (C, Print_Num, "print_num");
2590 Print_Num (Get_Num);
2596 To build this example, first compile the foreign language files to
2597 generate object files:
2599 ^gcc -c file1.c^gcc -c FILE1.C^
2600 ^gcc -c file2.c^gcc -c FILE2.C^
2604 Then, compile the Ada units to produce a set of object files and ALI
2607 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2611 Run the Ada binder on the Ada main program:
2613 gnatbind my_main.ali
2617 Link the Ada main program, the Ada objects and the other language
2620 gnatlink my_main.ali file1.o file2.o
2624 The last three steps can be grouped in a single command:
2626 gnatmake my_main.adb -largs file1.o file2.o
2629 @cindex Binder output file
2631 If the main program is in a language other than Ada, then you may have
2632 more than one entry point into the Ada subsystem. You must use a special
2633 binder option to generate callable routines that initialize and
2634 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2635 Calls to the initialization and finalization routines must be inserted
2636 in the main program, or some other appropriate point in the code. The
2637 call to initialize the Ada units must occur before the first Ada
2638 subprogram is called, and the call to finalize the Ada units must occur
2639 after the last Ada subprogram returns. The binder will place the
2640 initialization and finalization subprograms into the
2641 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2642 sources. To illustrate, we have the following example:
2646 extern void adainit (void);
2647 extern void adafinal (void);
2648 extern int add (int, int);
2649 extern int sub (int, int);
2651 int main (int argc, char *argv[])
2657 /* Should print "21 + 7 = 28" */
2658 printf ("%d + %d = %d\n", a, b, add (a, b));
2659 /* Should print "21 - 7 = 14" */
2660 printf ("%d - %d = %d\n", a, b, sub (a, b));
2666 @smallexample @c ada
2669 function Add (A, B : Integer) return Integer;
2670 pragma Export (C, Add, "add");
2674 package body Unit1 is
2675 function Add (A, B : Integer) return Integer is
2683 function Sub (A, B : Integer) return Integer;
2684 pragma Export (C, Sub, "sub");
2688 package body Unit2 is
2689 function Sub (A, B : Integer) return Integer is
2698 The build procedure for this application is similar to the last
2699 example's. First, compile the foreign language files to generate object
2702 ^gcc -c main.c^gcc -c main.c^
2706 Next, compile the Ada units to produce a set of object files and ALI
2709 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2710 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2714 Run the Ada binder on every generated ALI file. Make sure to use the
2715 @option{-n} option to specify a foreign main program:
2717 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2721 Link the Ada main program, the Ada objects and the foreign language
2722 objects. You need only list the last ALI file here:
2724 gnatlink unit2.ali main.o -o exec_file
2727 This procedure yields a binary executable called @file{exec_file}.
2731 Depending on the circumstances (for example when your non-Ada main object
2732 does not provide symbol @code{main}), you may also need to instruct the
2733 GNAT linker not to include the standard startup objects by passing the
2734 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2736 @node Calling Conventions
2737 @subsection Calling Conventions
2738 @cindex Foreign Languages
2739 @cindex Calling Conventions
2740 GNAT follows standard calling sequence conventions and will thus interface
2741 to any other language that also follows these conventions. The following
2742 Convention identifiers are recognized by GNAT:
2745 @cindex Interfacing to Ada
2746 @cindex Other Ada compilers
2747 @cindex Convention Ada
2749 This indicates that the standard Ada calling sequence will be
2750 used and all Ada data items may be passed without any limitations in the
2751 case where GNAT is used to generate both the caller and callee. It is also
2752 possible to mix GNAT generated code and code generated by another Ada
2753 compiler. In this case, the data types should be restricted to simple
2754 cases, including primitive types. Whether complex data types can be passed
2755 depends on the situation. Probably it is safe to pass simple arrays, such
2756 as arrays of integers or floats. Records may or may not work, depending
2757 on whether both compilers lay them out identically. Complex structures
2758 involving variant records, access parameters, tasks, or protected types,
2759 are unlikely to be able to be passed.
2761 Note that in the case of GNAT running
2762 on a platform that supports HP Ada 83, a higher degree of compatibility
2763 can be guaranteed, and in particular records are layed out in an identical
2764 manner in the two compilers. Note also that if output from two different
2765 compilers is mixed, the program is responsible for dealing with elaboration
2766 issues. Probably the safest approach is to write the main program in the
2767 version of Ada other than GNAT, so that it takes care of its own elaboration
2768 requirements, and then call the GNAT-generated adainit procedure to ensure
2769 elaboration of the GNAT components. Consult the documentation of the other
2770 Ada compiler for further details on elaboration.
2772 However, it is not possible to mix the tasking run time of GNAT and
2773 HP Ada 83, All the tasking operations must either be entirely within
2774 GNAT compiled sections of the program, or entirely within HP Ada 83
2775 compiled sections of the program.
2777 @cindex Interfacing to Assembly
2778 @cindex Convention Assembler
2780 Specifies assembler as the convention. In practice this has the
2781 same effect as convention Ada (but is not equivalent in the sense of being
2782 considered the same convention).
2784 @cindex Convention Asm
2787 Equivalent to Assembler.
2789 @cindex Interfacing to COBOL
2790 @cindex Convention COBOL
2793 Data will be passed according to the conventions described
2794 in section B.4 of the Ada Reference Manual.
2797 @cindex Interfacing to C
2798 @cindex Convention C
2800 Data will be passed according to the conventions described
2801 in section B.3 of the Ada Reference Manual.
2803 A note on interfacing to a C ``varargs'' function:
2804 @findex C varargs function
2805 @cindex Interfacing to C varargs function
2806 @cindex varargs function interfaces
2810 In C, @code{varargs} allows a function to take a variable number of
2811 arguments. There is no direct equivalent in this to Ada. One
2812 approach that can be used is to create a C wrapper for each
2813 different profile and then interface to this C wrapper. For
2814 example, to print an @code{int} value using @code{printf},
2815 create a C function @code{printfi} that takes two arguments, a
2816 pointer to a string and an int, and calls @code{printf}.
2817 Then in the Ada program, use pragma @code{Import} to
2818 interface to @code{printfi}.
2821 It may work on some platforms to directly interface to
2822 a @code{varargs} function by providing a specific Ada profile
2823 for a particular call. However, this does not work on
2824 all platforms, since there is no guarantee that the
2825 calling sequence for a two argument normal C function
2826 is the same as for calling a @code{varargs} C function with
2827 the same two arguments.
2830 @cindex Convention Default
2835 @cindex Convention External
2842 @cindex Interfacing to C++
2843 @cindex Convention C++
2844 @item C_Plus_Plus (or CPP)
2845 This stands for C++. For most purposes this is identical to C.
2846 See the separate description of the specialized GNAT pragmas relating to
2847 C++ interfacing for further details.
2851 @cindex Interfacing to Fortran
2852 @cindex Convention Fortran
2854 Data will be passed according to the conventions described
2855 in section B.5 of the Ada Reference Manual.
2858 This applies to an intrinsic operation, as defined in the Ada
2859 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2860 this means that the body of the subprogram is provided by the compiler itself,
2861 usually by means of an efficient code sequence, and that the user does not
2862 supply an explicit body for it. In an application program, the pragma may
2863 be applied to the following sets of names:
2867 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2868 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2869 two formal parameters. The
2870 first one must be a signed integer type or a modular type with a binary
2871 modulus, and the second parameter must be of type Natural.
2872 The return type must be the same as the type of the first argument. The size
2873 of this type can only be 8, 16, 32, or 64.
2876 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2877 The corresponding operator declaration must have parameters and result type
2878 that have the same root numeric type (for example, all three are long_float
2879 types). This simplifies the definition of operations that use type checking
2880 to perform dimensional checks:
2882 @smallexample @c ada
2883 type Distance is new Long_Float;
2884 type Time is new Long_Float;
2885 type Velocity is new Long_Float;
2886 function "/" (D : Distance; T : Time)
2888 pragma Import (Intrinsic, "/");
2892 This common idiom is often programmed with a generic definition and an
2893 explicit body. The pragma makes it simpler to introduce such declarations.
2894 It incurs no overhead in compilation time or code size, because it is
2895 implemented as a single machine instruction.
2898 General subprogram entities, to bind an Ada subprogram declaration to
2899 a compiler builtin by name with back-ends where such interfaces are
2900 available. A typical example is the set of ``__builtin'' functions
2901 exposed by the GCC back-end, as in the following example:
2903 @smallexample @c ada
2904 function builtin_sqrt (F : Float) return Float;
2905 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2908 Most of the GCC builtins are accessible this way, and as for other
2909 import conventions (e.g. C), it is the user's responsibility to ensure
2910 that the Ada subprogram profile matches the underlying builtin
2918 @cindex Convention Stdcall
2920 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2921 and specifies that the @code{Stdcall} calling sequence will be used,
2922 as defined by the NT API. Nevertheless, to ease building
2923 cross-platform bindings this convention will be handled as a @code{C} calling
2924 convention on non-Windows platforms.
2927 @cindex Convention DLL
2929 This is equivalent to @code{Stdcall}.
2932 @cindex Convention Win32
2934 This is equivalent to @code{Stdcall}.
2938 @cindex Convention Stubbed
2940 This is a special convention that indicates that the compiler
2941 should provide a stub body that raises @code{Program_Error}.
2945 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2946 that can be used to parametrize conventions and allow additional synonyms
2947 to be specified. For example if you have legacy code in which the convention
2948 identifier Fortran77 was used for Fortran, you can use the configuration
2951 @smallexample @c ada
2952 pragma Convention_Identifier (Fortran77, Fortran);
2956 And from now on the identifier Fortran77 may be used as a convention
2957 identifier (for example in an @code{Import} pragma) with the same
2961 @node Building Mixed Ada & C++ Programs
2962 @section Building Mixed Ada and C++ Programs
2965 A programmer inexperienced with mixed-language development may find that
2966 building an application containing both Ada and C++ code can be a
2967 challenge. This section gives a few
2968 hints that should make this task easier. The first section addresses
2969 the differences between interfacing with C and interfacing with C++.
2971 looks into the delicate problem of linking the complete application from
2972 its Ada and C++ parts. The last section gives some hints on how the GNAT
2973 run-time library can be adapted in order to allow inter-language dispatching
2974 with a new C++ compiler.
2977 * Interfacing to C++::
2978 * Linking a Mixed C++ & Ada Program::
2979 * A Simple Example::
2980 * Interfacing with C++ constructors::
2981 * Interfacing with C++ at the Class Level::
2984 @node Interfacing to C++
2985 @subsection Interfacing to C++
2988 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2989 generating code that is compatible with the G++ Application Binary
2990 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2993 Interfacing can be done at 3 levels: simple data, subprograms, and
2994 classes. In the first two cases, GNAT offers a specific @code{Convention
2995 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2996 Usually, C++ mangles the names of subprograms. To generate proper mangled
2997 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2998 This problem can also be addressed manually in two ways:
3002 by modifying the C++ code in order to force a C convention using
3003 the @code{extern "C"} syntax.
3006 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
3007 Link_Name argument of the pragma import.
3011 Interfacing at the class level can be achieved by using the GNAT specific
3012 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3013 gnat_rm, GNAT Reference Manual}, for additional information.
3015 @node Linking a Mixed C++ & Ada Program
3016 @subsection Linking a Mixed C++ & Ada Program
3019 Usually the linker of the C++ development system must be used to link
3020 mixed applications because most C++ systems will resolve elaboration
3021 issues (such as calling constructors on global class instances)
3022 transparently during the link phase. GNAT has been adapted to ease the
3023 use of a foreign linker for the last phase. Three cases can be
3028 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3029 The C++ linker can simply be called by using the C++ specific driver
3032 Note that if the C++ code uses inline functions, you will need to
3033 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3034 order to provide an existing function implementation that the Ada code can
3038 $ g++ -c -fkeep-inline-functions file1.C
3039 $ g++ -c -fkeep-inline-functions file2.C
3040 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3044 Using GNAT and G++ from two different GCC installations: If both
3045 compilers are on the @env{PATH}, the previous method may be used. It is
3046 important to note that environment variables such as
3047 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3048 @env{GCC_ROOT} will affect both compilers
3049 at the same time and may make one of the two compilers operate
3050 improperly if set during invocation of the wrong compiler. It is also
3051 very important that the linker uses the proper @file{libgcc.a} GCC
3052 library -- that is, the one from the C++ compiler installation. The
3053 implicit link command as suggested in the @command{gnatmake} command
3054 from the former example can be replaced by an explicit link command with
3055 the full-verbosity option in order to verify which library is used:
3058 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3060 If there is a problem due to interfering environment variables, it can
3061 be worked around by using an intermediate script. The following example
3062 shows the proper script to use when GNAT has not been installed at its
3063 default location and g++ has been installed at its default location:
3071 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3075 Using a non-GNU C++ compiler: The commands previously described can be
3076 used to insure that the C++ linker is used. Nonetheless, you need to add
3077 a few more parameters to the link command line, depending on the exception
3080 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3081 to the libgcc libraries are required:
3086 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3087 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3090 Where CC is the name of the non-GNU C++ compiler.
3092 If the @code{zero cost} exception mechanism is used, and the platform
3093 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3094 paths to more objects are required:
3099 CC `gcc -print-file-name=crtbegin.o` $* \
3100 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3101 `gcc -print-file-name=crtend.o`
3102 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3105 If the @code{zero cost} exception mechanism is used, and the platform
3106 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3107 Tru64 or AIX), the simple approach described above will not work and
3108 a pre-linking phase using GNAT will be necessary.
3112 Another alternative is to use the @command{gprbuild} multi-language builder
3113 which has a large knowledge base and knows how to link Ada and C++ code
3114 together automatically in most cases.
3116 @node A Simple Example
3117 @subsection A Simple Example
3119 The following example, provided as part of the GNAT examples, shows how
3120 to achieve procedural interfacing between Ada and C++ in both
3121 directions. The C++ class A has two methods. The first method is exported
3122 to Ada by the means of an extern C wrapper function. The second method
3123 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3124 a limited record with a layout comparable to the C++ class. The Ada
3125 subprogram, in turn, calls the C++ method. So, starting from the C++
3126 main program, the process passes back and forth between the two
3130 Here are the compilation commands:
3132 $ gnatmake -c simple_cpp_interface
3135 $ gnatbind -n simple_cpp_interface
3136 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3137 -lstdc++ ex7.o cpp_main.o
3141 Here are the corresponding sources:
3149 void adainit (void);
3150 void adafinal (void);
3151 void method1 (A *t);
3173 class A : public Origin @{
3175 void method1 (void);
3176 void method2 (int v);
3186 extern "C" @{ void ada_method2 (A *t, int v);@}
3188 void A::method1 (void)
3191 printf ("in A::method1, a_value = %d \n",a_value);
3195 void A::method2 (int v)
3197 ada_method2 (this, v);
3198 printf ("in A::method2, a_value = %d \n",a_value);
3205 printf ("in A::A, a_value = %d \n",a_value);
3209 @smallexample @c ada
3211 package body Simple_Cpp_Interface is
3213 procedure Ada_Method2 (This : in out A; V : Integer) is
3219 end Simple_Cpp_Interface;
3222 package Simple_Cpp_Interface is
3225 Vptr : System.Address;
3229 pragma Convention (C, A);
3231 procedure Method1 (This : in out A);
3232 pragma Import (C, Method1);
3234 procedure Ada_Method2 (This : in out A; V : Integer);
3235 pragma Export (C, Ada_Method2);
3237 end Simple_Cpp_Interface;
3240 @node Interfacing with C++ constructors
3241 @subsection Interfacing with C++ constructors
3244 In order to interface with C++ constructors GNAT provides the
3245 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3246 gnat_rm, GNAT Reference Manual}, for additional information).
3247 In this section we present some common uses of C++ constructors
3248 in mixed-languages programs in GNAT.
3250 Let us assume that we need to interface with the following
3258 @b{virtual} int Get_Value ();
3259 Root(); // Default constructor
3260 Root(int v); // 1st non-default constructor
3261 Root(int v, int w); // 2nd non-default constructor
3265 For this purpose we can write the following package spec (further
3266 information on how to build this spec is available in
3267 @ref{Interfacing with C++ at the Class Level} and
3268 @ref{Generating Ada Bindings for C and C++ headers}).
3270 @smallexample @c ada
3271 with Interfaces.C; use Interfaces.C;
3273 type Root is tagged limited record
3277 pragma Import (CPP, Root);
3279 function Get_Value (Obj : Root) return int;
3280 pragma Import (CPP, Get_Value);
3282 function Constructor return Root;
3283 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3285 function Constructor (v : Integer) return Root;
3286 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3288 function Constructor (v, w : Integer) return Root;
3289 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3293 On the Ada side the constructor is represented by a function (whose
3294 name is arbitrary) that returns the classwide type corresponding to
3295 the imported C++ class. Although the constructor is described as a
3296 function, it is typically a procedure with an extra implicit argument
3297 (the object being initialized) at the implementation level. GNAT
3298 issues the appropriate call, whatever it is, to get the object
3299 properly initialized.
3301 Constructors can only appear in the following contexts:
3305 On the right side of an initialization of an object of type @var{T}.
3307 On the right side of an initialization of a record component of type @var{T}.
3309 In an Ada 2005 limited aggregate.
3311 In an Ada 2005 nested limited aggregate.
3313 In an Ada 2005 limited aggregate that initializes an object built in
3314 place by an extended return statement.
3318 In a declaration of an object whose type is a class imported from C++,
3319 either the default C++ constructor is implicitly called by GNAT, or
3320 else the required C++ constructor must be explicitly called in the
3321 expression that initializes the object. For example:
3323 @smallexample @c ada
3325 Obj2 : Root := Constructor;
3326 Obj3 : Root := Constructor (v => 10);
3327 Obj4 : Root := Constructor (30, 40);
3330 The first two declarations are equivalent: in both cases the default C++
3331 constructor is invoked (in the former case the call to the constructor is
3332 implicit, and in the latter case the call is explicit in the object
3333 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3334 that takes an integer argument, and @code{Obj4} is initialized by the
3335 non-default C++ constructor that takes two integers.
3337 Let us derive the imported C++ class in the Ada side. For example:
3339 @smallexample @c ada
3340 type DT is new Root with record
3341 C_Value : Natural := 2009;
3345 In this case the components DT inherited from the C++ side must be
3346 initialized by a C++ constructor, and the additional Ada components
3347 of type DT are initialized by GNAT. The initialization of such an
3348 object is done either by default, or by means of a function returning
3349 an aggregate of type DT, or by means of an extension aggregate.
3351 @smallexample @c ada
3353 Obj6 : DT := Function_Returning_DT (50);
3354 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3357 The declaration of @code{Obj5} invokes the default constructors: the
3358 C++ default constructor of the parent type takes care of the initialization
3359 of the components inherited from Root, and GNAT takes care of the default
3360 initialization of the additional Ada components of type DT (that is,
3361 @code{C_Value} is initialized to value 2009). The order of invocation of
3362 the constructors is consistent with the order of elaboration required by
3363 Ada and C++. That is, the constructor of the parent type is always called
3364 before the constructor of the derived type.
3366 Let us now consider a record that has components whose type is imported
3367 from C++. For example:
3369 @smallexample @c ada
3370 type Rec1 is limited record
3371 Data1 : Root := Constructor (10);
3372 Value : Natural := 1000;
3375 type Rec2 (D : Integer := 20) is limited record
3377 Data2 : Root := Constructor (D, 30);
3381 The initialization of an object of type @code{Rec2} will call the
3382 non-default C++ constructors specified for the imported components.
3385 @smallexample @c ada
3389 Using Ada 2005 we can use limited aggregates to initialize an object
3390 invoking C++ constructors that differ from those specified in the type
3391 declarations. For example:
3393 @smallexample @c ada
3394 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3399 The above declaration uses an Ada 2005 limited aggregate to
3400 initialize @code{Obj9}, and the C++ constructor that has two integer
3401 arguments is invoked to initialize the @code{Data1} component instead
3402 of the constructor specified in the declaration of type @code{Rec1}. In
3403 Ada 2005 the box in the aggregate indicates that unspecified components
3404 are initialized using the expression (if any) available in the component
3405 declaration. That is, in this case discriminant @code{D} is initialized
3406 to value @code{20}, @code{Value} is initialized to value 1000, and the
3407 non-default C++ constructor that handles two integers takes care of
3408 initializing component @code{Data2} with values @code{20,30}.
3410 In Ada 2005 we can use the extended return statement to build the Ada
3411 equivalent to C++ non-default constructors. For example:
3413 @smallexample @c ada
3414 function Constructor (V : Integer) return Rec2 is
3416 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3419 -- Further actions required for construction of
3420 -- objects of type Rec2
3426 In this example the extended return statement construct is used to
3427 build in place the returned object whose components are initialized
3428 by means of a limited aggregate. Any further action associated with
3429 the constructor can be placed inside the construct.
3431 @node Interfacing with C++ at the Class Level
3432 @subsection Interfacing with C++ at the Class Level
3434 In this section we demonstrate the GNAT features for interfacing with
3435 C++ by means of an example making use of Ada 2005 abstract interface
3436 types. This example consists of a classification of animals; classes
3437 have been used to model our main classification of animals, and
3438 interfaces provide support for the management of secondary
3439 classifications. We first demonstrate a case in which the types and
3440 constructors are defined on the C++ side and imported from the Ada
3441 side, and latter the reverse case.
3443 The root of our derivation will be the @code{Animal} class, with a
3444 single private attribute (the @code{Age} of the animal) and two public
3445 primitives to set and get the value of this attribute.
3450 @b{virtual} void Set_Age (int New_Age);
3451 @b{virtual} int Age ();
3457 Abstract interface types are defined in C++ by means of classes with pure
3458 virtual functions and no data members. In our example we will use two
3459 interfaces that provide support for the common management of @code{Carnivore}
3460 and @code{Domestic} animals:
3463 @b{class} Carnivore @{
3465 @b{virtual} int Number_Of_Teeth () = 0;
3468 @b{class} Domestic @{
3470 @b{virtual void} Set_Owner (char* Name) = 0;
3474 Using these declarations, we can now say that a @code{Dog} is an animal that is
3475 both Carnivore and Domestic, that is:
3478 @b{class} Dog : Animal, Carnivore, Domestic @{
3480 @b{virtual} int Number_Of_Teeth ();
3481 @b{virtual} void Set_Owner (char* Name);
3483 Dog(); // Constructor
3490 In the following examples we will assume that the previous declarations are
3491 located in a file named @code{animals.h}. The following package demonstrates
3492 how to import these C++ declarations from the Ada side:
3494 @smallexample @c ada
3495 with Interfaces.C.Strings; use Interfaces.C.Strings;
3497 type Carnivore is interface;
3498 pragma Convention (C_Plus_Plus, Carnivore);
3499 function Number_Of_Teeth (X : Carnivore)
3500 return Natural is abstract;
3502 type Domestic is interface;
3503 pragma Convention (C_Plus_Plus, Set_Owner);
3505 (X : in out Domestic;
3506 Name : Chars_Ptr) is abstract;
3508 type Animal is tagged record
3511 pragma Import (C_Plus_Plus, Animal);
3513 procedure Set_Age (X : in out Animal; Age : Integer);
3514 pragma Import (C_Plus_Plus, Set_Age);
3516 function Age (X : Animal) return Integer;
3517 pragma Import (C_Plus_Plus, Age);
3519 type Dog is new Animal and Carnivore and Domestic with record
3520 Tooth_Count : Natural;
3521 Owner : String (1 .. 30);
3523 pragma Import (C_Plus_Plus, Dog);
3525 function Number_Of_Teeth (A : Dog) return Integer;
3526 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3528 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3529 pragma Import (C_Plus_Plus, Set_Owner);
3531 function New_Dog return Dog;
3532 pragma CPP_Constructor (New_Dog);
3533 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3537 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3538 interfacing with these C++ classes is easy. The only requirement is that all
3539 the primitives and components must be declared exactly in the same order in
3542 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3543 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3544 the arguments to the called primitives will be the same as for C++. For the
3545 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3546 to indicate that they have been defined on the C++ side; this is required
3547 because the dispatch table associated with these tagged types will be built
3548 in the C++ side and therefore will not contain the predefined Ada primitives
3549 which Ada would otherwise expect.
3551 As the reader can see there is no need to indicate the C++ mangled names
3552 associated with each subprogram because it is assumed that all the calls to
3553 these primitives will be dispatching calls. The only exception is the
3554 constructor, which must be registered with the compiler by means of
3555 @code{pragma CPP_Constructor} and needs to provide its associated C++
3556 mangled name because the Ada compiler generates direct calls to it.
3558 With the above packages we can now declare objects of type Dog on the Ada side
3559 and dispatch calls to the corresponding subprograms on the C++ side. We can
3560 also extend the tagged type Dog with further fields and primitives, and
3561 override some of its C++ primitives on the Ada side. For example, here we have
3562 a type derivation defined on the Ada side that inherits all the dispatching
3563 primitives of the ancestor from the C++ side.
3566 @b{with} Animals; @b{use} Animals;
3567 @b{package} Vaccinated_Animals @b{is}
3568 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3569 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3570 @b{end} Vaccinated_Animals;
3573 It is important to note that, because of the ABI compatibility, the programmer
3574 does not need to add any further information to indicate either the object
3575 layout or the dispatch table entry associated with each dispatching operation.
3577 Now let us define all the types and constructors on the Ada side and export
3578 them to C++, using the same hierarchy of our previous example:
3580 @smallexample @c ada
3581 with Interfaces.C.Strings;
3582 use Interfaces.C.Strings;
3584 type Carnivore is interface;
3585 pragma Convention (C_Plus_Plus, Carnivore);
3586 function Number_Of_Teeth (X : Carnivore)
3587 return Natural is abstract;
3589 type Domestic is interface;
3590 pragma Convention (C_Plus_Plus, Set_Owner);
3592 (X : in out Domestic;
3593 Name : Chars_Ptr) is abstract;
3595 type Animal is tagged record
3598 pragma Convention (C_Plus_Plus, Animal);
3600 procedure Set_Age (X : in out Animal; Age : Integer);
3601 pragma Export (C_Plus_Plus, Set_Age);
3603 function Age (X : Animal) return Integer;
3604 pragma Export (C_Plus_Plus, Age);
3606 type Dog is new Animal and Carnivore and Domestic with record
3607 Tooth_Count : Natural;
3608 Owner : String (1 .. 30);
3610 pragma Convention (C_Plus_Plus, Dog);
3612 function Number_Of_Teeth (A : Dog) return Integer;
3613 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3615 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3616 pragma Export (C_Plus_Plus, Set_Owner);
3618 function New_Dog return Dog'Class;
3619 pragma Export (C_Plus_Plus, New_Dog);
3623 Compared with our previous example the only difference is the use of
3624 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3625 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3626 nothing else to be done; as explained above, the only requirement is that all
3627 the primitives and components are declared in exactly the same order.
3629 For completeness, let us see a brief C++ main program that uses the
3630 declarations available in @code{animals.h} (presented in our first example) to
3631 import and use the declarations from the Ada side, properly initializing and
3632 finalizing the Ada run-time system along the way:
3635 @b{#include} "animals.h"
3636 @b{#include} <iostream>
3637 @b{using namespace} std;
3639 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3640 void Check_Domestic (Domestic *obj) @{@dots{}@}
3641 void Check_Animal (Animal *obj) @{@dots{}@}
3642 void Check_Dog (Dog *obj) @{@dots{}@}
3645 void adainit (void);
3646 void adafinal (void);
3652 Dog *obj = new_dog(); // Ada constructor
3653 Check_Carnivore (obj); // Check secondary DT
3654 Check_Domestic (obj); // Check secondary DT
3655 Check_Animal (obj); // Check primary DT
3656 Check_Dog (obj); // Check primary DT
3661 adainit (); test(); adafinal ();
3666 @node Comparison between GNAT and C/C++ Compilation Models
3667 @section Comparison between GNAT and C/C++ Compilation Models
3670 The GNAT model of compilation is close to the C and C++ models. You can
3671 think of Ada specs as corresponding to header files in C. As in C, you
3672 don't need to compile specs; they are compiled when they are used. The
3673 Ada @code{with} is similar in effect to the @code{#include} of a C
3676 One notable difference is that, in Ada, you may compile specs separately
3677 to check them for semantic and syntactic accuracy. This is not always
3678 possible with C headers because they are fragments of programs that have
3679 less specific syntactic or semantic rules.
3681 The other major difference is the requirement for running the binder,
3682 which performs two important functions. First, it checks for
3683 consistency. In C or C++, the only defense against assembling
3684 inconsistent programs lies outside the compiler, in a makefile, for
3685 example. The binder satisfies the Ada requirement that it be impossible
3686 to construct an inconsistent program when the compiler is used in normal
3689 @cindex Elaboration order control
3690 The other important function of the binder is to deal with elaboration
3691 issues. There are also elaboration issues in C++ that are handled
3692 automatically. This automatic handling has the advantage of being
3693 simpler to use, but the C++ programmer has no control over elaboration.
3694 Where @code{gnatbind} might complain there was no valid order of
3695 elaboration, a C++ compiler would simply construct a program that
3696 malfunctioned at run time.
3699 @node Comparison between GNAT and Conventional Ada Library Models
3700 @section Comparison between GNAT and Conventional Ada Library Models
3703 This section is intended for Ada programmers who have
3704 used an Ada compiler implementing the traditional Ada library
3705 model, as described in the Ada Reference Manual.
3707 @cindex GNAT library
3708 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3709 source files themselves acts as the library. Compiling Ada programs does
3710 not generate any centralized information, but rather an object file and
3711 a ALI file, which are of interest only to the binder and linker.
3712 In a traditional system, the compiler reads information not only from
3713 the source file being compiled, but also from the centralized library.
3714 This means that the effect of a compilation depends on what has been
3715 previously compiled. In particular:
3719 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3720 to the version of the unit most recently compiled into the library.
3723 Inlining is effective only if the necessary body has already been
3724 compiled into the library.
3727 Compiling a unit may obsolete other units in the library.
3731 In GNAT, compiling one unit never affects the compilation of any other
3732 units because the compiler reads only source files. Only changes to source
3733 files can affect the results of a compilation. In particular:
3737 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3738 to the source version of the unit that is currently accessible to the
3743 Inlining requires the appropriate source files for the package or
3744 subprogram bodies to be available to the compiler. Inlining is always
3745 effective, independent of the order in which units are complied.
3748 Compiling a unit never affects any other compilations. The editing of
3749 sources may cause previous compilations to be out of date if they
3750 depended on the source file being modified.
3754 The most important result of these differences is that order of compilation
3755 is never significant in GNAT. There is no situation in which one is
3756 required to do one compilation before another. What shows up as order of
3757 compilation requirements in the traditional Ada library becomes, in
3758 GNAT, simple source dependencies; in other words, there is only a set
3759 of rules saying what source files must be present when a file is
3763 @node Placement of temporary files
3764 @section Placement of temporary files
3765 @cindex Temporary files (user control over placement)
3768 GNAT creates temporary files in the directory designated by the environment
3769 variable @env{TMPDIR}.
3770 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3771 for detailed information on how environment variables are resolved.
3772 For most users the easiest way to make use of this feature is to simply
3773 define @env{TMPDIR} as a job level logical name).
3774 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3775 for compiler temporary files, then you can include something like the
3776 following command in your @file{LOGIN.COM} file:
3779 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3783 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3784 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3785 designated by @env{TEMP}.
3786 If none of these environment variables are defined then GNAT uses the
3787 directory designated by the logical name @code{SYS$SCRATCH:}
3788 (by default the user's home directory). If all else fails
3789 GNAT uses the current directory for temporary files.
3792 @c *************************
3793 @node Compiling Using gcc
3794 @chapter Compiling Using @command{gcc}
3797 This chapter discusses how to compile Ada programs using the @command{gcc}
3798 command. It also describes the set of switches
3799 that can be used to control the behavior of the compiler.
3801 * Compiling Programs::
3802 * Switches for gcc::
3803 * Search Paths and the Run-Time Library (RTL)::
3804 * Order of Compilation Issues::
3808 @node Compiling Programs
3809 @section Compiling Programs
3812 The first step in creating an executable program is to compile the units
3813 of the program using the @command{gcc} command. You must compile the
3818 the body file (@file{.adb}) for a library level subprogram or generic
3822 the spec file (@file{.ads}) for a library level package or generic
3823 package that has no body
3826 the body file (@file{.adb}) for a library level package
3827 or generic package that has a body
3832 You need @emph{not} compile the following files
3837 the spec of a library unit which has a body
3844 because they are compiled as part of compiling related units. GNAT
3846 when the corresponding body is compiled, and subunits when the parent is
3849 @cindex cannot generate code
3850 If you attempt to compile any of these files, you will get one of the
3851 following error messages (where @var{fff} is the name of the file you compiled):
3854 cannot generate code for file @var{fff} (package spec)
3855 to check package spec, use -gnatc
3857 cannot generate code for file @var{fff} (missing subunits)
3858 to check parent unit, use -gnatc
3860 cannot generate code for file @var{fff} (subprogram spec)
3861 to check subprogram spec, use -gnatc
3863 cannot generate code for file @var{fff} (subunit)
3864 to check subunit, use -gnatc
3868 As indicated by the above error messages, if you want to submit
3869 one of these files to the compiler to check for correct semantics
3870 without generating code, then use the @option{-gnatc} switch.
3872 The basic command for compiling a file containing an Ada unit is
3875 $ gcc -c @ovar{switches} @file{file name}
3879 where @var{file name} is the name of the Ada file (usually
3881 @file{.ads} for a spec or @file{.adb} for a body).
3884 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3886 The result of a successful compilation is an object file, which has the
3887 same name as the source file but an extension of @file{.o} and an Ada
3888 Library Information (ALI) file, which also has the same name as the
3889 source file, but with @file{.ali} as the extension. GNAT creates these
3890 two output files in the current directory, but you may specify a source
3891 file in any directory using an absolute or relative path specification
3892 containing the directory information.
3895 @command{gcc} is actually a driver program that looks at the extensions of
3896 the file arguments and loads the appropriate compiler. For example, the
3897 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3898 These programs are in directories known to the driver program (in some
3899 configurations via environment variables you set), but need not be in
3900 your path. The @command{gcc} driver also calls the assembler and any other
3901 utilities needed to complete the generation of the required object
3904 It is possible to supply several file names on the same @command{gcc}
3905 command. This causes @command{gcc} to call the appropriate compiler for
3906 each file. For example, the following command lists three separate
3907 files to be compiled:
3910 $ gcc -c x.adb y.adb z.c
3914 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3915 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3916 The compiler generates three object files @file{x.o}, @file{y.o} and
3917 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3918 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3921 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3924 @node Switches for gcc
3925 @section Switches for @command{gcc}
3928 The @command{gcc} command accepts switches that control the
3929 compilation process. These switches are fully described in this section.
3930 First we briefly list all the switches, in alphabetical order, then we
3931 describe the switches in more detail in functionally grouped sections.
3933 More switches exist for GCC than those documented here, especially
3934 for specific targets. However, their use is not recommended as
3935 they may change code generation in ways that are incompatible with
3936 the Ada run-time library, or can cause inconsistencies between
3940 * Output and Error Message Control::
3941 * Warning Message Control::
3942 * Debugging and Assertion Control::
3943 * Validity Checking::
3946 * Using gcc for Syntax Checking::
3947 * Using gcc for Semantic Checking::
3948 * Compiling Different Versions of Ada::
3949 * Character Set Control::
3950 * File Naming Control::
3951 * Subprogram Inlining Control::
3952 * Auxiliary Output Control::
3953 * Debugging Control::
3954 * Exception Handling Control::
3955 * Units to Sources Mapping Files::
3956 * Integrated Preprocessing::
3957 * Code Generation Control::
3966 @cindex @option{-b} (@command{gcc})
3967 @item -b @var{target}
3968 Compile your program to run on @var{target}, which is the name of a
3969 system configuration. You must have a GNAT cross-compiler built if
3970 @var{target} is not the same as your host system.
3973 @cindex @option{-B} (@command{gcc})
3974 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3975 from @var{dir} instead of the default location. Only use this switch
3976 when multiple versions of the GNAT compiler are available.
3977 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3978 GNU Compiler Collection (GCC)}, for further details. You would normally
3979 use the @option{-b} or @option{-V} switch instead.
3982 @cindex @option{-c} (@command{gcc})
3983 Compile. Always use this switch when compiling Ada programs.
3985 Note: for some other languages when using @command{gcc}, notably in
3986 the case of C and C++, it is possible to use
3987 use @command{gcc} without a @option{-c} switch to
3988 compile and link in one step. In the case of GNAT, you
3989 cannot use this approach, because the binder must be run
3990 and @command{gcc} cannot be used to run the GNAT binder.
3994 @cindex @option{-fno-inline} (@command{gcc})
3995 Suppresses all back-end inlining, even if other optimization or inlining
3997 This includes suppression of inlining that results
3998 from the use of the pragma @code{Inline_Always}.
3999 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
4000 are ignored, and @option{-gnatn} and @option{-gnatN} have no
4001 effect if this switch is present.
4003 @item -fno-inline-functions
4004 @cindex @option{-fno-inline-functions} (@command{gcc})
4005 Suppresses automatic inlining of simple subprograms, which is enabled
4006 if @option{-O3} is used.
4008 @item -fno-inline-small-functions
4009 @cindex @option{-fno-inline-small-functions} (@command{gcc})
4010 Suppresses automatic inlining of small subprograms, which is enabled
4011 if @option{-O2} is used.
4013 @item -fno-inline-functions-called-once
4014 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
4015 Suppresses inlining of subprograms local to the unit and called once
4016 from within it, which is enabled if @option{-O1} is used.
4019 @cindex @option{-fno-ivopts} (@command{gcc})
4020 Suppresses high-level loop induction variable optimizations, which are
4021 enabled if @option{-O1} is used. These optimizations are generally
4022 profitable but, for some specific cases of loops with numerous uses
4023 of the iteration variable that follow a common pattern, they may end
4024 up destroying the regularity that could be exploited at a lower level
4025 and thus producing inferior code.
4027 @item -fno-strict-aliasing
4028 @cindex @option{-fno-strict-aliasing} (@command{gcc})
4029 Causes the compiler to avoid assumptions regarding non-aliasing
4030 of objects of different types. See
4031 @ref{Optimization and Strict Aliasing} for details.
4034 @cindex @option{-fstack-check} (@command{gcc})
4035 Activates stack checking.
4036 See @ref{Stack Overflow Checking} for details.
4039 @cindex @option{-fstack-usage} (@command{gcc})
4040 Makes the compiler output stack usage information for the program, on a
4041 per-function basis. See @ref{Static Stack Usage Analysis} for details.
4043 @item -fcallgraph-info@r{[}=su@r{]}
4044 @cindex @option{-fcallgraph-info} (@command{gcc})
4045 Makes the compiler output callgraph information for the program, on a
4046 per-file basis. The information is generated in the VCG format. It can
4047 be decorated with stack-usage per-node information.
4050 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4051 Generate debugging information. This information is stored in the object
4052 file and copied from there to the final executable file by the linker,
4053 where it can be read by the debugger. You must use the
4054 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4057 @cindex @option{-gnat83} (@command{gcc})
4058 Enforce Ada 83 restrictions.
4061 @cindex @option{-gnat95} (@command{gcc})
4062 Enforce Ada 95 restrictions.
4065 @cindex @option{-gnat05} (@command{gcc})
4066 Allow full Ada 2005 features.
4069 @cindex @option{-gnata} (@command{gcc})
4070 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4071 activated. Note that these pragmas can also be controlled using the
4072 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4073 It also activates pragmas @code{Check}, @code{Precondition}, and
4074 @code{Postcondition}. Note that these pragmas can also be controlled
4075 using the configuration pragma @code{Check_Policy}.
4078 @cindex @option{-gnatA} (@command{gcc})
4079 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4083 @cindex @option{-gnatb} (@command{gcc})
4084 Generate brief messages to @file{stderr} even if verbose mode set.
4087 @cindex @option{-gnatB} (@command{gcc})
4088 Assume no invalid (bad) values except for 'Valid attribute use
4089 (@pxref{Validity Checking}).
4092 @cindex @option{-gnatc} (@command{gcc})
4093 Check syntax and semantics only (no code generation attempted).
4096 @cindex @option{-gnatC} (@command{gcc})
4097 Generate CodePeer information (no code generation attempted).
4098 This switch will generate an intermediate representation suitable for
4099 use by CodePeer (@file{.scil} files). This switch is not compatible with
4100 code generation (it will, among other things, disable some switches such
4101 as -gnatn, and enable others such as -gnata).
4104 @cindex @option{-gnatd} (@command{gcc})
4105 Specify debug options for the compiler. The string of characters after
4106 the @option{-gnatd} specify the specific debug options. The possible
4107 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4108 compiler source file @file{debug.adb} for details of the implemented
4109 debug options. Certain debug options are relevant to applications
4110 programmers, and these are documented at appropriate points in this
4115 @cindex @option{-gnatD[nn]} (@command{gcc})
4118 @item /XDEBUG /LXDEBUG=nnn
4120 Create expanded source files for source level debugging. This switch
4121 also suppress generation of cross-reference information
4122 (see @option{-gnatx}).
4124 @item -gnatec=@var{path}
4125 @cindex @option{-gnatec} (@command{gcc})
4126 Specify a configuration pragma file
4128 (the equal sign is optional)
4130 (@pxref{The Configuration Pragmas Files}).
4132 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4133 @cindex @option{-gnateD} (@command{gcc})
4134 Defines a symbol, associated with @var{value}, for preprocessing.
4135 (@pxref{Integrated Preprocessing}).
4138 @cindex @option{-gnatef} (@command{gcc})
4139 Display full source path name in brief error messages.
4142 @cindex @option{-gnateG} (@command{gcc})
4143 Save result of preprocessing in a text file.
4145 @item -gnatem=@var{path}
4146 @cindex @option{-gnatem} (@command{gcc})
4147 Specify a mapping file
4149 (the equal sign is optional)
4151 (@pxref{Units to Sources Mapping Files}).
4153 @item -gnatep=@var{file}
4154 @cindex @option{-gnatep} (@command{gcc})
4155 Specify a preprocessing data file
4157 (the equal sign is optional)
4159 (@pxref{Integrated Preprocessing}).
4162 @cindex @option{-gnateS} (@command{gcc})
4163 Generate SCO (Source Coverage Obligation) information in the ALI
4164 file. This information is used by advanced coverage tools. See
4165 unit @file{SCOs} in the compiler sources for details in files
4166 @file{scos.ads} and @file{scos.adb}.
4169 @cindex @option{-gnatE} (@command{gcc})
4170 Full dynamic elaboration checks.
4173 @cindex @option{-gnatf} (@command{gcc})
4174 Full errors. Multiple errors per line, all undefined references, do not
4175 attempt to suppress cascaded errors.
4178 @cindex @option{-gnatF} (@command{gcc})
4179 Externals names are folded to all uppercase.
4181 @item ^-gnatg^/GNAT_INTERNAL^
4182 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4183 Internal GNAT implementation mode. This should not be used for
4184 applications programs, it is intended only for use by the compiler
4185 and its run-time library. For documentation, see the GNAT sources.
4186 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4187 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4188 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4189 so that all standard warnings and all standard style options are turned on.
4190 All warnings and style error messages are treated as errors.
4194 @cindex @option{-gnatG[nn]} (@command{gcc})
4197 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4199 List generated expanded code in source form.
4201 @item ^-gnath^/HELP^
4202 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4203 Output usage information. The output is written to @file{stdout}.
4205 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4206 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4207 Identifier character set
4209 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4211 For details of the possible selections for @var{c},
4212 see @ref{Character Set Control}.
4214 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4215 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4216 Ignore representation clauses. When this switch is used,
4217 representation clauses are treated as comments. This is useful
4218 when initially porting code where you want to ignore rep clause
4219 problems, and also for compiling foreign code (particularly
4220 for use with ASIS). The representation clauses that are ignored
4221 are: enumeration_representation_clause, record_representation_clause,
4222 and attribute_definition_clause for the following attributes:
4223 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4224 Object_Size, Size, Small, Stream_Size, and Value_Size.
4225 Note that this option should be used only for compiling -- the
4226 code is likely to malfunction at run time.
4229 @cindex @option{-gnatjnn} (@command{gcc})
4230 Reformat error messages to fit on nn character lines
4232 @item -gnatk=@var{n}
4233 @cindex @option{-gnatk} (@command{gcc})
4234 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4237 @cindex @option{-gnatl} (@command{gcc})
4238 Output full source listing with embedded error messages.
4241 @cindex @option{-gnatL} (@command{gcc})
4242 Used in conjunction with -gnatG or -gnatD to intersperse original
4243 source lines (as comment lines with line numbers) in the expanded
4246 @item -gnatm=@var{n}
4247 @cindex @option{-gnatm} (@command{gcc})
4248 Limit number of detected error or warning messages to @var{n}
4249 where @var{n} is in the range 1..999999. The default setting if
4250 no switch is given is 9999. If the number of warnings reaches this
4251 limit, then a message is output and further warnings are suppressed,
4252 but the compilation is continued. If the number of error messages
4253 reaches this limit, then a message is output and the compilation
4254 is abandoned. The equal sign here is optional. A value of zero
4255 means that no limit applies.
4258 @cindex @option{-gnatn} (@command{gcc})
4259 Activate inlining for subprograms for which
4260 pragma @code{inline} is specified. This inlining is performed
4261 by the GCC back-end.
4264 @cindex @option{-gnatN} (@command{gcc})
4265 Activate front end inlining for subprograms for which
4266 pragma @code{Inline} is specified. This inlining is performed
4267 by the front end and will be visible in the
4268 @option{-gnatG} output.
4270 When using a gcc-based back end (in practice this means using any version
4271 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4272 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4273 Historically front end inlining was more extensive than the gcc back end
4274 inlining, but that is no longer the case.
4277 @cindex @option{-gnato} (@command{gcc})
4278 Enable numeric overflow checking (which is not normally enabled by
4279 default). Note that division by zero is a separate check that is not
4280 controlled by this switch (division by zero checking is on by default).
4283 @cindex @option{-gnatp} (@command{gcc})
4284 Suppress all checks. See @ref{Run-Time Checks} for details.
4287 @cindex @option{-gnatP} (@command{gcc})
4288 Enable polling. This is required on some systems (notably Windows NT) to
4289 obtain asynchronous abort and asynchronous transfer of control capability.
4290 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4294 @cindex @option{-gnatq} (@command{gcc})
4295 Don't quit. Try semantics, even if parse errors.
4298 @cindex @option{-gnatQ} (@command{gcc})
4299 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4302 @cindex @option{-gnatr} (@command{gcc})
4303 Treat pragma Restrictions as Restriction_Warnings.
4305 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4306 @cindex @option{-gnatR} (@command{gcc})
4307 Output representation information for declared types and objects.
4310 @cindex @option{-gnats} (@command{gcc})
4314 @cindex @option{-gnatS} (@command{gcc})
4315 Print package Standard.
4318 @cindex @option{-gnatt} (@command{gcc})
4319 Generate tree output file.
4321 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4322 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4323 All compiler tables start at @var{nnn} times usual starting size.
4326 @cindex @option{-gnatu} (@command{gcc})
4327 List units for this compilation.
4330 @cindex @option{-gnatU} (@command{gcc})
4331 Tag all error messages with the unique string ``error:''
4334 @cindex @option{-gnatv} (@command{gcc})
4335 Verbose mode. Full error output with source lines to @file{stdout}.
4338 @cindex @option{-gnatV} (@command{gcc})
4339 Control level of validity checking (@pxref{Validity Checking}).
4341 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4342 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4344 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4345 the exact warnings that
4346 are enabled or disabled (@pxref{Warning Message Control}).
4348 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4349 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4350 Wide character encoding method
4352 (@var{e}=n/h/u/s/e/8).
4355 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4359 @cindex @option{-gnatx} (@command{gcc})
4360 Suppress generation of cross-reference information.
4362 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4363 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4364 Enable built-in style checks (@pxref{Style Checking}).
4366 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4367 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4368 Distribution stub generation and compilation
4370 (@var{m}=r/c for receiver/caller stubs).
4373 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4374 to be generated and compiled).
4377 @item ^-I^/SEARCH=^@var{dir}
4378 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4380 Direct GNAT to search the @var{dir} directory for source files needed by
4381 the current compilation
4382 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4384 @item ^-I-^/NOCURRENT_DIRECTORY^
4385 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4387 Except for the source file named in the command line, do not look for source
4388 files in the directory containing the source file named in the command line
4389 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4393 @cindex @option{-mbig-switch} (@command{gcc})
4394 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4395 This standard gcc switch causes the compiler to use larger offsets in its
4396 jump table representation for @code{case} statements.
4397 This may result in less efficient code, but is sometimes necessary
4398 (for example on HP-UX targets)
4399 @cindex HP-UX and @option{-mbig-switch} option
4400 in order to compile large and/or nested @code{case} statements.
4403 @cindex @option{-o} (@command{gcc})
4404 This switch is used in @command{gcc} to redirect the generated object file
4405 and its associated ALI file. Beware of this switch with GNAT, because it may
4406 cause the object file and ALI file to have different names which in turn
4407 may confuse the binder and the linker.
4411 @cindex @option{-nostdinc} (@command{gcc})
4412 Inhibit the search of the default location for the GNAT Run Time
4413 Library (RTL) source files.
4416 @cindex @option{-nostdlib} (@command{gcc})
4417 Inhibit the search of the default location for the GNAT Run Time
4418 Library (RTL) ALI files.
4422 @cindex @option{-O} (@command{gcc})
4423 @var{n} controls the optimization level.
4427 No optimization, the default setting if no @option{-O} appears
4430 Normal optimization, the default if you specify @option{-O} without
4431 an operand. A good compromise between code quality and compilation
4435 Extensive optimization, may improve execution time, possibly at the cost of
4436 substantially increased compilation time.
4439 Same as @option{-O2}, and also includes inline expansion for small subprograms
4443 Optimize space usage
4447 See also @ref{Optimization Levels}.
4452 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4453 Equivalent to @option{/OPTIMIZE=NONE}.
4454 This is the default behavior in the absence of an @option{/OPTIMIZE}
4457 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4458 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4459 Selects the level of optimization for your program. The supported
4460 keywords are as follows:
4463 Perform most optimizations, including those that
4465 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4466 without keyword options.
4469 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4472 Perform some optimizations, but omit ones that are costly.
4475 Same as @code{SOME}.
4478 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4479 automatic inlining of small subprograms within a unit
4482 Try to unroll loops. This keyword may be specified together with
4483 any keyword above other than @code{NONE}. Loop unrolling
4484 usually, but not always, improves the performance of programs.
4487 Optimize space usage
4491 See also @ref{Optimization Levels}.
4495 @item -pass-exit-codes
4496 @cindex @option{-pass-exit-codes} (@command{gcc})
4497 Catch exit codes from the compiler and use the most meaningful as
4501 @item --RTS=@var{rts-path}
4502 @cindex @option{--RTS} (@command{gcc})
4503 Specifies the default location of the runtime library. Same meaning as the
4504 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4507 @cindex @option{^-S^/ASM^} (@command{gcc})
4508 ^Used in place of @option{-c} to^Used to^
4509 cause the assembler source file to be
4510 generated, using @file{^.s^.S^} as the extension,
4511 instead of the object file.
4512 This may be useful if you need to examine the generated assembly code.
4514 @item ^-fverbose-asm^/VERBOSE_ASM^
4515 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4516 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4517 to cause the generated assembly code file to be annotated with variable
4518 names, making it significantly easier to follow.
4521 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4522 Show commands generated by the @command{gcc} driver. Normally used only for
4523 debugging purposes or if you need to be sure what version of the
4524 compiler you are executing.
4528 @cindex @option{-V} (@command{gcc})
4529 Execute @var{ver} version of the compiler. This is the @command{gcc}
4530 version, not the GNAT version.
4533 @item ^-w^/NO_BACK_END_WARNINGS^
4534 @cindex @option{-w} (@command{gcc})
4535 Turn off warnings generated by the back end of the compiler. Use of
4536 this switch also causes the default for front end warnings to be set
4537 to suppress (as though @option{-gnatws} had appeared at the start of
4543 @c Combining qualifiers does not work on VMS
4544 You may combine a sequence of GNAT switches into a single switch. For
4545 example, the combined switch
4547 @cindex Combining GNAT switches
4553 is equivalent to specifying the following sequence of switches:
4556 -gnato -gnatf -gnati3
4561 The following restrictions apply to the combination of switches
4566 The switch @option{-gnatc} if combined with other switches must come
4567 first in the string.
4570 The switch @option{-gnats} if combined with other switches must come
4571 first in the string.
4575 ^^@option{/DISTRIBUTION_STUBS=},^
4576 @option{-gnatzc} and @option{-gnatzr} may not be combined with any other
4577 switches, and only one of them may appear in the command line.
4581 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4582 switch), then all further characters in the switch are interpreted
4583 as style modifiers (see description of @option{-gnaty}).
4586 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4587 switch), then all further characters in the switch are interpreted
4588 as debug flags (see description of @option{-gnatd}).
4591 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4592 switch), then all further characters in the switch are interpreted
4593 as warning mode modifiers (see description of @option{-gnatw}).
4596 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4597 switch), then all further characters in the switch are interpreted
4598 as validity checking options (@pxref{Validity Checking}).
4601 Option ``em'', ``ec'', ``ep'', ``l='' and ``R'' must be the last options in
4602 a combined list of options.
4606 @node Output and Error Message Control
4607 @subsection Output and Error Message Control
4611 The standard default format for error messages is called ``brief format''.
4612 Brief format messages are written to @file{stderr} (the standard error
4613 file) and have the following form:
4616 e.adb:3:04: Incorrect spelling of keyword "function"
4617 e.adb:4:20: ";" should be "is"
4621 The first integer after the file name is the line number in the file,
4622 and the second integer is the column number within the line.
4624 @code{GPS} can parse the error messages
4625 and point to the referenced character.
4627 The following switches provide control over the error message
4633 @cindex @option{-gnatv} (@command{gcc})
4636 The v stands for verbose.
4638 The effect of this setting is to write long-format error
4639 messages to @file{stdout} (the standard output file.
4640 The same program compiled with the
4641 @option{-gnatv} switch would generate:
4645 3. funcion X (Q : Integer)
4647 >>> Incorrect spelling of keyword "function"
4650 >>> ";" should be "is"
4655 The vertical bar indicates the location of the error, and the @samp{>>>}
4656 prefix can be used to search for error messages. When this switch is
4657 used the only source lines output are those with errors.
4660 @cindex @option{-gnatl} (@command{gcc})
4662 The @code{l} stands for list.
4664 This switch causes a full listing of
4665 the file to be generated. In the case where a body is
4666 compiled, the corresponding spec is also listed, along
4667 with any subunits. Typical output from compiling a package
4668 body @file{p.adb} might look like:
4670 @smallexample @c ada
4674 1. package body p is
4676 3. procedure a is separate;
4687 2. pragma Elaborate_Body
4711 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4712 standard output is redirected, a brief summary is written to
4713 @file{stderr} (standard error) giving the number of error messages and
4714 warning messages generated.
4716 @item -^gnatl^OUTPUT_FILE^=file
4717 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4718 This has the same effect as @option{-gnatl} except that the output is
4719 written to a file instead of to standard output. If the given name
4720 @file{fname} does not start with a period, then it is the full name
4721 of the file to be written. If @file{fname} is an extension, it is
4722 appended to the name of the file being compiled. For example, if
4723 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4724 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4727 @cindex @option{-gnatU} (@command{gcc})
4728 This switch forces all error messages to be preceded by the unique
4729 string ``error:''. This means that error messages take a few more
4730 characters in space, but allows easy searching for and identification
4734 @cindex @option{-gnatb} (@command{gcc})
4736 The @code{b} stands for brief.
4738 This switch causes GNAT to generate the
4739 brief format error messages to @file{stderr} (the standard error
4740 file) as well as the verbose
4741 format message or full listing (which as usual is written to
4742 @file{stdout} (the standard output file).
4744 @item -gnatm=@var{n}
4745 @cindex @option{-gnatm} (@command{gcc})
4747 The @code{m} stands for maximum.
4749 @var{n} is a decimal integer in the
4750 range of 1 to 999999 and limits the number of error or warning
4751 messages to be generated. For example, using
4752 @option{-gnatm2} might yield
4755 e.adb:3:04: Incorrect spelling of keyword "function"
4756 e.adb:5:35: missing ".."
4757 fatal error: maximum number of errors detected
4758 compilation abandoned
4762 The default setting if
4763 no switch is given is 9999. If the number of warnings reaches this
4764 limit, then a message is output and further warnings are suppressed,
4765 but the compilation is continued. If the number of error messages
4766 reaches this limit, then a message is output and the compilation
4767 is abandoned. A value of zero means that no limit applies.
4770 Note that the equal sign is optional, so the switches
4771 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4774 @cindex @option{-gnatf} (@command{gcc})
4775 @cindex Error messages, suppressing
4777 The @code{f} stands for full.
4779 Normally, the compiler suppresses error messages that are likely to be
4780 redundant. This switch causes all error
4781 messages to be generated. In particular, in the case of
4782 references to undefined variables. If a given variable is referenced
4783 several times, the normal format of messages is
4785 e.adb:7:07: "V" is undefined (more references follow)
4789 where the parenthetical comment warns that there are additional
4790 references to the variable @code{V}. Compiling the same program with the
4791 @option{-gnatf} switch yields
4794 e.adb:7:07: "V" is undefined
4795 e.adb:8:07: "V" is undefined
4796 e.adb:8:12: "V" is undefined
4797 e.adb:8:16: "V" is undefined
4798 e.adb:9:07: "V" is undefined
4799 e.adb:9:12: "V" is undefined
4803 The @option{-gnatf} switch also generates additional information for
4804 some error messages. Some examples are:
4808 Details on possibly non-portable unchecked conversion
4810 List possible interpretations for ambiguous calls
4812 Additional details on incorrect parameters
4816 @cindex @option{-gnatjnn} (@command{gcc})
4817 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4818 with continuation lines are treated as though the continuation lines were
4819 separate messages (and so a warning with two continuation lines counts as
4820 three warnings, and is listed as three separate messages).
4822 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4823 messages are output in a different manner. A message and all its continuation
4824 lines are treated as a unit, and count as only one warning or message in the
4825 statistics totals. Furthermore, the message is reformatted so that no line
4826 is longer than nn characters.
4829 @cindex @option{-gnatq} (@command{gcc})
4831 The @code{q} stands for quit (really ``don't quit'').
4833 In normal operation mode, the compiler first parses the program and
4834 determines if there are any syntax errors. If there are, appropriate
4835 error messages are generated and compilation is immediately terminated.
4837 GNAT to continue with semantic analysis even if syntax errors have been
4838 found. This may enable the detection of more errors in a single run. On
4839 the other hand, the semantic analyzer is more likely to encounter some
4840 internal fatal error when given a syntactically invalid tree.
4843 @cindex @option{-gnatQ} (@command{gcc})
4844 In normal operation mode, the @file{ALI} file is not generated if any
4845 illegalities are detected in the program. The use of @option{-gnatQ} forces
4846 generation of the @file{ALI} file. This file is marked as being in
4847 error, so it cannot be used for binding purposes, but it does contain
4848 reasonably complete cross-reference information, and thus may be useful
4849 for use by tools (e.g., semantic browsing tools or integrated development
4850 environments) that are driven from the @file{ALI} file. This switch
4851 implies @option{-gnatq}, since the semantic phase must be run to get a
4852 meaningful ALI file.
4854 In addition, if @option{-gnatt} is also specified, then the tree file is
4855 generated even if there are illegalities. It may be useful in this case
4856 to also specify @option{-gnatq} to ensure that full semantic processing
4857 occurs. The resulting tree file can be processed by ASIS, for the purpose
4858 of providing partial information about illegal units, but if the error
4859 causes the tree to be badly malformed, then ASIS may crash during the
4862 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4863 being in error, @command{gnatmake} will attempt to recompile the source when it
4864 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4866 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4867 since ALI files are never generated if @option{-gnats} is set.
4871 @node Warning Message Control
4872 @subsection Warning Message Control
4873 @cindex Warning messages
4875 In addition to error messages, which correspond to illegalities as defined
4876 in the Ada Reference Manual, the compiler detects two kinds of warning
4879 First, the compiler considers some constructs suspicious and generates a
4880 warning message to alert you to a possible error. Second, if the
4881 compiler detects a situation that is sure to raise an exception at
4882 run time, it generates a warning message. The following shows an example
4883 of warning messages:
4885 e.adb:4:24: warning: creation of object may raise Storage_Error
4886 e.adb:10:17: warning: static value out of range
4887 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4891 GNAT considers a large number of situations as appropriate
4892 for the generation of warning messages. As always, warnings are not
4893 definite indications of errors. For example, if you do an out-of-range
4894 assignment with the deliberate intention of raising a
4895 @code{Constraint_Error} exception, then the warning that may be
4896 issued does not indicate an error. Some of the situations for which GNAT
4897 issues warnings (at least some of the time) are given in the following
4898 list. This list is not complete, and new warnings are often added to
4899 subsequent versions of GNAT. The list is intended to give a general idea
4900 of the kinds of warnings that are generated.
4904 Possible infinitely recursive calls
4907 Out-of-range values being assigned
4910 Possible order of elaboration problems
4913 Assertions (pragma Assert) that are sure to fail
4919 Address clauses with possibly unaligned values, or where an attempt is
4920 made to overlay a smaller variable with a larger one.
4923 Fixed-point type declarations with a null range
4926 Direct_IO or Sequential_IO instantiated with a type that has access values
4929 Variables that are never assigned a value
4932 Variables that are referenced before being initialized
4935 Task entries with no corresponding @code{accept} statement
4938 Duplicate accepts for the same task entry in a @code{select}
4941 Objects that take too much storage
4944 Unchecked conversion between types of differing sizes
4947 Missing @code{return} statement along some execution path in a function
4950 Incorrect (unrecognized) pragmas
4953 Incorrect external names
4956 Allocation from empty storage pool
4959 Potentially blocking operation in protected type
4962 Suspicious parenthesization of expressions
4965 Mismatching bounds in an aggregate
4968 Attempt to return local value by reference
4971 Premature instantiation of a generic body
4974 Attempt to pack aliased components
4977 Out of bounds array subscripts
4980 Wrong length on string assignment
4983 Violations of style rules if style checking is enabled
4986 Unused @code{with} clauses
4989 @code{Bit_Order} usage that does not have any effect
4992 @code{Standard.Duration} used to resolve universal fixed expression
4995 Dereference of possibly null value
4998 Declaration that is likely to cause storage error
5001 Internal GNAT unit @code{with}'ed by application unit
5004 Values known to be out of range at compile time
5007 Unreferenced labels and variables
5010 Address overlays that could clobber memory
5013 Unexpected initialization when address clause present
5016 Bad alignment for address clause
5019 Useless type conversions
5022 Redundant assignment statements and other redundant constructs
5025 Useless exception handlers
5028 Accidental hiding of name by child unit
5031 Access before elaboration detected at compile time
5034 A range in a @code{for} loop that is known to be null or might be null
5039 The following section lists compiler switches that are available
5040 to control the handling of warning messages. It is also possible
5041 to exercise much finer control over what warnings are issued and
5042 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5043 gnat_rm, GNAT Reference manual}.
5048 @emph{Activate all optional errors.}
5049 @cindex @option{-gnatwa} (@command{gcc})
5050 This switch activates most optional warning messages, see remaining list
5051 in this section for details on optional warning messages that can be
5052 individually controlled. The warnings that are not turned on by this
5054 @option{-gnatwd} (implicit dereferencing),
5055 @option{-gnatwh} (hiding),
5056 @option{-gnatwl} (elaboration warnings),
5057 @option{-gnatw.o} (warn on values set by out parameters ignored)
5058 and @option{-gnatwt} (tracking of deleted conditional code).
5059 All other optional warnings are turned on.
5062 @emph{Suppress all optional errors.}
5063 @cindex @option{-gnatwA} (@command{gcc})
5064 This switch suppresses all optional warning messages, see remaining list
5065 in this section for details on optional warning messages that can be
5066 individually controlled.
5069 @emph{Activate warnings on failing assertions.}
5070 @cindex @option{-gnatw.a} (@command{gcc})
5071 @cindex Assert failures
5072 This switch activates warnings for assertions where the compiler can tell at
5073 compile time that the assertion will fail. Note that this warning is given
5074 even if assertions are disabled. The default is that such warnings are
5078 @emph{Suppress warnings on failing assertions.}
5079 @cindex @option{-gnatw.A} (@command{gcc})
5080 @cindex Assert failures
5081 This switch suppresses warnings for assertions where the compiler can tell at
5082 compile time that the assertion will fail.
5085 @emph{Activate warnings on bad fixed values.}
5086 @cindex @option{-gnatwb} (@command{gcc})
5087 @cindex Bad fixed values
5088 @cindex Fixed-point Small value
5090 This switch activates warnings for static fixed-point expressions whose
5091 value is not an exact multiple of Small. Such values are implementation
5092 dependent, since an implementation is free to choose either of the multiples
5093 that surround the value. GNAT always chooses the closer one, but this is not
5094 required behavior, and it is better to specify a value that is an exact
5095 multiple, ensuring predictable execution. The default is that such warnings
5099 @emph{Suppress warnings on bad fixed values.}
5100 @cindex @option{-gnatwB} (@command{gcc})
5101 This switch suppresses warnings for static fixed-point expressions whose
5102 value is not an exact multiple of Small.
5105 @emph{Activate warnings on biased representation.}
5106 @cindex @option{-gnatw.b} (@command{gcc})
5107 @cindex Biased representation
5108 This switch activates warnings when a size clause, value size clause, component
5109 clause, or component size clause forces the use of biased representation for an
5110 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5111 to represent 10/11). The default is that such warnings are generated.
5114 @emph{Suppress warnings on biased representation.}
5115 @cindex @option{-gnatwB} (@command{gcc})
5116 This switch suppresses warnings for representation clauses that force the use
5117 of biased representation.
5120 @emph{Activate warnings on conditionals.}
5121 @cindex @option{-gnatwc} (@command{gcc})
5122 @cindex Conditionals, constant
5123 This switch activates warnings for conditional expressions used in
5124 tests that are known to be True or False at compile time. The default
5125 is that such warnings are not generated.
5126 Note that this warning does
5127 not get issued for the use of boolean variables or constants whose
5128 values are known at compile time, since this is a standard technique
5129 for conditional compilation in Ada, and this would generate too many
5130 false positive warnings.
5132 This warning option also activates a special test for comparisons using
5133 the operators ``>='' and`` <=''.
5134 If the compiler can tell that only the equality condition is possible,
5135 then it will warn that the ``>'' or ``<'' part of the test
5136 is useless and that the operator could be replaced by ``=''.
5137 An example would be comparing a @code{Natural} variable <= 0.
5139 This warning option also generates warnings if
5140 one or both tests is optimized away in a membership test for integer
5141 values if the result can be determined at compile time. Range tests on
5142 enumeration types are not included, since it is common for such tests
5143 to include an end point.
5145 This warning can also be turned on using @option{-gnatwa}.
5148 @emph{Suppress warnings on conditionals.}
5149 @cindex @option{-gnatwC} (@command{gcc})
5150 This switch suppresses warnings for conditional expressions used in
5151 tests that are known to be True or False at compile time.
5154 @emph{Activate warnings on missing component clauses.}
5155 @cindex @option{-gnatw.c} (@command{gcc})
5156 @cindex Component clause, missing
5157 This switch activates warnings for record components where a record
5158 representation clause is present and has component clauses for the
5159 majority, but not all, of the components. A warning is given for each
5160 component for which no component clause is present.
5162 This warning can also be turned on using @option{-gnatwa}.
5165 @emph{Suppress warnings on missing component clauses.}
5166 @cindex @option{-gnatwC} (@command{gcc})
5167 This switch suppresses warnings for record components that are
5168 missing a component clause in the situation described above.
5171 @emph{Activate warnings on implicit dereferencing.}
5172 @cindex @option{-gnatwd} (@command{gcc})
5173 If this switch is set, then the use of a prefix of an access type
5174 in an indexed component, slice, or selected component without an
5175 explicit @code{.all} will generate a warning. With this warning
5176 enabled, access checks occur only at points where an explicit
5177 @code{.all} appears in the source code (assuming no warnings are
5178 generated as a result of this switch). The default is that such
5179 warnings are not generated.
5180 Note that @option{-gnatwa} does not affect the setting of
5181 this warning option.
5184 @emph{Suppress warnings on implicit dereferencing.}
5185 @cindex @option{-gnatwD} (@command{gcc})
5186 @cindex Implicit dereferencing
5187 @cindex Dereferencing, implicit
5188 This switch suppresses warnings for implicit dereferences in
5189 indexed components, slices, and selected components.
5192 @emph{Treat warnings as errors.}
5193 @cindex @option{-gnatwe} (@command{gcc})
5194 @cindex Warnings, treat as error
5195 This switch causes warning messages to be treated as errors.
5196 The warning string still appears, but the warning messages are counted
5197 as errors, and prevent the generation of an object file.
5200 @emph{Activate every optional warning}
5201 @cindex @option{-gnatw.e} (@command{gcc})
5202 @cindex Warnings, activate every optional warning
5203 This switch activates all optional warnings, including those which
5204 are not activated by @code{-gnatwa}.
5207 @emph{Activate warnings on unreferenced formals.}
5208 @cindex @option{-gnatwf} (@command{gcc})
5209 @cindex Formals, unreferenced
5210 This switch causes a warning to be generated if a formal parameter
5211 is not referenced in the body of the subprogram. This warning can
5212 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5213 default is that these warnings are not generated.
5216 @emph{Suppress warnings on unreferenced formals.}
5217 @cindex @option{-gnatwF} (@command{gcc})
5218 This switch suppresses warnings for unreferenced formal
5219 parameters. Note that the
5220 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5221 effect of warning on unreferenced entities other than subprogram
5225 @emph{Activate warnings on unrecognized pragmas.}
5226 @cindex @option{-gnatwg} (@command{gcc})
5227 @cindex Pragmas, unrecognized
5228 This switch causes a warning to be generated if an unrecognized
5229 pragma is encountered. Apart from issuing this warning, the
5230 pragma is ignored and has no effect. This warning can
5231 also be turned on using @option{-gnatwa}. The default
5232 is that such warnings are issued (satisfying the Ada Reference
5233 Manual requirement that such warnings appear).
5236 @emph{Suppress warnings on unrecognized pragmas.}
5237 @cindex @option{-gnatwG} (@command{gcc})
5238 This switch suppresses warnings for unrecognized pragmas.
5241 @emph{Activate warnings on hiding.}
5242 @cindex @option{-gnatwh} (@command{gcc})
5243 @cindex Hiding of Declarations
5244 This switch activates warnings on hiding declarations.
5245 A declaration is considered hiding
5246 if it is for a non-overloadable entity, and it declares an entity with the
5247 same name as some other entity that is directly or use-visible. The default
5248 is that such warnings are not generated.
5249 Note that @option{-gnatwa} does not affect the setting of this warning option.
5252 @emph{Suppress warnings on hiding.}
5253 @cindex @option{-gnatwH} (@command{gcc})
5254 This switch suppresses warnings on hiding declarations.
5257 @emph{Activate warnings on implementation units.}
5258 @cindex @option{-gnatwi} (@command{gcc})
5259 This switch activates warnings for a @code{with} of an internal GNAT
5260 implementation unit, defined as any unit from the @code{Ada},
5261 @code{Interfaces}, @code{GNAT},
5262 ^^@code{DEC},^ or @code{System}
5263 hierarchies that is not
5264 documented in either the Ada Reference Manual or the GNAT
5265 Programmer's Reference Manual. Such units are intended only
5266 for internal implementation purposes and should not be @code{with}'ed
5267 by user programs. The default is that such warnings are generated
5268 This warning can also be turned on using @option{-gnatwa}.
5271 @emph{Disable warnings on implementation units.}
5272 @cindex @option{-gnatwI} (@command{gcc})
5273 This switch disables warnings for a @code{with} of an internal GNAT
5274 implementation unit.
5277 @emph{Activate warnings on overlapping actuals.}
5278 @cindex @option{-gnatw.i} (@command{gcc})
5279 This switch enables a warning on statically detectable overlapping actuals in
5280 a subprogram call, when one of the actuals is an in-out parameter, and the
5281 types of the actuals are not by-copy types. The warning is off by default,
5282 and is not included under -gnatwa.
5285 @emph{Disable warnings on overlapping actuals.}
5286 @cindex @option{-gnatw.I} (@command{gcc})
5287 This switch disables warnings on overlapping actuals in a call..
5290 @emph{Activate warnings on obsolescent features (Annex J).}
5291 @cindex @option{-gnatwj} (@command{gcc})
5292 @cindex Features, obsolescent
5293 @cindex Obsolescent features
5294 If this warning option is activated, then warnings are generated for
5295 calls to subprograms marked with @code{pragma Obsolescent} and
5296 for use of features in Annex J of the Ada Reference Manual. In the
5297 case of Annex J, not all features are flagged. In particular use
5298 of the renamed packages (like @code{Text_IO}) and use of package
5299 @code{ASCII} are not flagged, since these are very common and
5300 would generate many annoying positive warnings. The default is that
5301 such warnings are not generated. This warning is also turned on by
5302 the use of @option{-gnatwa}.
5304 In addition to the above cases, warnings are also generated for
5305 GNAT features that have been provided in past versions but which
5306 have been superseded (typically by features in the new Ada standard).
5307 For example, @code{pragma Ravenscar} will be flagged since its
5308 function is replaced by @code{pragma Profile(Ravenscar)}.
5310 Note that this warning option functions differently from the
5311 restriction @code{No_Obsolescent_Features} in two respects.
5312 First, the restriction applies only to annex J features.
5313 Second, the restriction does flag uses of package @code{ASCII}.
5316 @emph{Suppress warnings on obsolescent features (Annex J).}
5317 @cindex @option{-gnatwJ} (@command{gcc})
5318 This switch disables warnings on use of obsolescent features.
5321 @emph{Activate warnings on variables that could be constants.}
5322 @cindex @option{-gnatwk} (@command{gcc})
5323 This switch activates warnings for variables that are initialized but
5324 never modified, and then could be declared constants. The default is that
5325 such warnings are not given.
5326 This warning can also be turned on using @option{-gnatwa}.
5329 @emph{Suppress warnings on variables that could be constants.}
5330 @cindex @option{-gnatwK} (@command{gcc})
5331 This switch disables warnings on variables that could be declared constants.
5334 @emph{Activate warnings for elaboration pragmas.}
5335 @cindex @option{-gnatwl} (@command{gcc})
5336 @cindex Elaboration, warnings
5337 This switch activates warnings on missing
5338 @code{Elaborate_All} and @code{Elaborate} pragmas.
5339 See the section in this guide on elaboration checking for details on
5340 when such pragmas should be used. In dynamic elaboration mode, this switch
5341 generations warnings about the need to add elaboration pragmas. Note however,
5342 that if you blindly follow these warnings, and add @code{Elaborate_All}
5343 warnings wherever they are recommended, you basically end up with the
5344 equivalent of the static elaboration model, which may not be what you want for
5345 legacy code for which the static model does not work.
5347 For the static model, the messages generated are labeled "info:" (for
5348 information messages). They are not warnings to add elaboration pragmas,
5349 merely informational messages showing what implicit elaboration pragmas
5350 have been added, for use in analyzing elaboration circularity problems.
5352 Warnings are also generated if you
5353 are using the static mode of elaboration, and a @code{pragma Elaborate}
5354 is encountered. The default is that such warnings
5356 This warning is not automatically turned on by the use of @option{-gnatwa}.
5359 @emph{Suppress warnings for elaboration pragmas.}
5360 @cindex @option{-gnatwL} (@command{gcc})
5361 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5362 See the section in this guide on elaboration checking for details on
5363 when such pragmas should be used.
5366 @emph{Activate warnings on modified but unreferenced variables.}
5367 @cindex @option{-gnatwm} (@command{gcc})
5368 This switch activates warnings for variables that are assigned (using
5369 an initialization value or with one or more assignment statements) but
5370 whose value is never read. The warning is suppressed for volatile
5371 variables and also for variables that are renamings of other variables
5372 or for which an address clause is given.
5373 This warning can also be turned on using @option{-gnatwa}.
5374 The default is that these warnings are not given.
5377 @emph{Disable warnings on modified but unreferenced variables.}
5378 @cindex @option{-gnatwM} (@command{gcc})
5379 This switch disables warnings for variables that are assigned or
5380 initialized, but never read.
5383 @emph{Activate warnings on suspicious modulus values.}
5384 @cindex @option{-gnatw.m} (@command{gcc})
5385 This switch activates warnings for modulus values that seem suspicious.
5386 The cases caught are where the size is the same as the modulus (e.g.
5387 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5388 with no size clause. The guess in both cases is that 2**x was intended
5389 rather than x. The default is that these warnings are given.
5392 @emph{Disable warnings on suspicious modulus values.}
5393 @cindex @option{-gnatw.M} (@command{gcc})
5394 This switch disables warnings for suspicious modulus values.
5397 @emph{Set normal warnings mode.}
5398 @cindex @option{-gnatwn} (@command{gcc})
5399 This switch sets normal warning mode, in which enabled warnings are
5400 issued and treated as warnings rather than errors. This is the default
5401 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5402 an explicit @option{-gnatws} or
5403 @option{-gnatwe}. It also cancels the effect of the
5404 implicit @option{-gnatwe} that is activated by the
5405 use of @option{-gnatg}.
5408 @emph{Activate warnings on address clause overlays.}
5409 @cindex @option{-gnatwo} (@command{gcc})
5410 @cindex Address Clauses, warnings
5411 This switch activates warnings for possibly unintended initialization
5412 effects of defining address clauses that cause one variable to overlap
5413 another. The default is that such warnings are generated.
5414 This warning can also be turned on using @option{-gnatwa}.
5417 @emph{Suppress warnings on address clause overlays.}
5418 @cindex @option{-gnatwO} (@command{gcc})
5419 This switch suppresses warnings on possibly unintended initialization
5420 effects of defining address clauses that cause one variable to overlap
5424 @emph{Activate warnings on modified but unreferenced out parameters.}
5425 @cindex @option{-gnatw.o} (@command{gcc})
5426 This switch activates warnings for variables that are modified by using
5427 them as actuals for a call to a procedure with an out mode formal, where
5428 the resulting assigned value is never read. It is applicable in the case
5429 where there is more than one out mode formal. If there is only one out
5430 mode formal, the warning is issued by default (controlled by -gnatwu).
5431 The warning is suppressed for volatile
5432 variables and also for variables that are renamings of other variables
5433 or for which an address clause is given.
5434 The default is that these warnings are not given. Note that this warning
5435 is not included in -gnatwa, it must be activated explicitly.
5438 @emph{Disable warnings on modified but unreferenced out parameters.}
5439 @cindex @option{-gnatw.O} (@command{gcc})
5440 This switch suppresses warnings for variables that are modified by using
5441 them as actuals for a call to a procedure with an out mode formal, where
5442 the resulting assigned value is never read.
5445 @emph{Activate warnings on ineffective pragma Inlines.}
5446 @cindex @option{-gnatwp} (@command{gcc})
5447 @cindex Inlining, warnings
5448 This switch activates warnings for failure of front end inlining
5449 (activated by @option{-gnatN}) to inline a particular call. There are
5450 many reasons for not being able to inline a call, including most
5451 commonly that the call is too complex to inline. The default is
5452 that such warnings are not given.
5453 This warning can also be turned on using @option{-gnatwa}.
5454 Warnings on ineffective inlining by the gcc back-end can be activated
5455 separately, using the gcc switch -Winline.
5458 @emph{Suppress warnings on ineffective pragma Inlines.}
5459 @cindex @option{-gnatwP} (@command{gcc})
5460 This switch suppresses warnings on ineffective pragma Inlines. If the
5461 inlining mechanism cannot inline a call, it will simply ignore the
5465 @emph{Activate warnings on parameter ordering.}
5466 @cindex @option{-gnatw.p} (@command{gcc})
5467 @cindex Parameter order, warnings
5468 This switch activates warnings for cases of suspicious parameter
5469 ordering when the list of arguments are all simple identifiers that
5470 match the names of the formals, but are in a different order. The
5471 warning is suppressed if any use of named parameter notation is used,
5472 so this is the appropriate way to suppress a false positive (and
5473 serves to emphasize that the "misordering" is deliberate). The
5475 that such warnings are not given.
5476 This warning can also be turned on using @option{-gnatwa}.
5479 @emph{Suppress warnings on parameter ordering.}
5480 @cindex @option{-gnatw.P} (@command{gcc})
5481 This switch suppresses warnings on cases of suspicious parameter
5485 @emph{Activate warnings on questionable missing parentheses.}
5486 @cindex @option{-gnatwq} (@command{gcc})
5487 @cindex Parentheses, warnings
5488 This switch activates warnings for cases where parentheses are not used and
5489 the result is potential ambiguity from a readers point of view. For example
5490 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5491 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5492 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5493 follow the rule of always parenthesizing to make the association clear, and
5494 this warning switch warns if such parentheses are not present. The default
5495 is that these warnings are given.
5496 This warning can also be turned on using @option{-gnatwa}.
5499 @emph{Suppress warnings on questionable missing parentheses.}
5500 @cindex @option{-gnatwQ} (@command{gcc})
5501 This switch suppresses warnings for cases where the association is not
5502 clear and the use of parentheses is preferred.
5505 @emph{Activate warnings on redundant constructs.}
5506 @cindex @option{-gnatwr} (@command{gcc})
5507 This switch activates warnings for redundant constructs. The following
5508 is the current list of constructs regarded as redundant:
5512 Assignment of an item to itself.
5514 Type conversion that converts an expression to its own type.
5516 Use of the attribute @code{Base} where @code{typ'Base} is the same
5519 Use of pragma @code{Pack} when all components are placed by a record
5520 representation clause.
5522 Exception handler containing only a reraise statement (raise with no
5523 operand) which has no effect.
5525 Use of the operator abs on an operand that is known at compile time
5528 Comparison of boolean expressions to an explicit True value.
5531 This warning can also be turned on using @option{-gnatwa}.
5532 The default is that warnings for redundant constructs are not given.
5535 @emph{Suppress warnings on redundant constructs.}
5536 @cindex @option{-gnatwR} (@command{gcc})
5537 This switch suppresses warnings for redundant constructs.
5540 @emph{Activate warnings for object renaming function.}
5541 @cindex @option{-gnatw.r} (@command{gcc})
5542 This switch activates warnings for an object renaming that renames a
5543 function call, which is equivalent to a constant declaration (as
5544 opposed to renaming the function itself). The default is that these
5545 warnings are given. This warning can also be turned on using
5549 @emph{Suppress warnings for object renaming function.}
5550 @cindex @option{-gnatwT} (@command{gcc})
5551 This switch suppresses warnings for object renaming function.
5554 @emph{Suppress all warnings.}
5555 @cindex @option{-gnatws} (@command{gcc})
5556 This switch completely suppresses the
5557 output of all warning messages from the GNAT front end.
5558 Note that it does not suppress warnings from the @command{gcc} back end.
5559 To suppress these back end warnings as well, use the switch @option{-w}
5560 in addition to @option{-gnatws}.
5563 @emph{Activate warnings for tracking of deleted conditional code.}
5564 @cindex @option{-gnatwt} (@command{gcc})
5565 @cindex Deactivated code, warnings
5566 @cindex Deleted code, warnings
5567 This switch activates warnings for tracking of code in conditionals (IF and
5568 CASE statements) that is detected to be dead code which cannot be executed, and
5569 which is removed by the front end. This warning is off by default, and is not
5570 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5571 useful for detecting deactivated code in certified applications.
5574 @emph{Suppress warnings for tracking of deleted conditional code.}
5575 @cindex @option{-gnatwT} (@command{gcc})
5576 This switch suppresses warnings for tracking of deleted conditional code.
5579 @emph{Activate warnings on unused entities.}
5580 @cindex @option{-gnatwu} (@command{gcc})
5581 This switch activates warnings to be generated for entities that
5582 are declared but not referenced, and for units that are @code{with}'ed
5584 referenced. In the case of packages, a warning is also generated if
5585 no entities in the package are referenced. This means that if the package
5586 is referenced but the only references are in @code{use}
5587 clauses or @code{renames}
5588 declarations, a warning is still generated. A warning is also generated
5589 for a generic package that is @code{with}'ed but never instantiated.
5590 In the case where a package or subprogram body is compiled, and there
5591 is a @code{with} on the corresponding spec
5592 that is only referenced in the body,
5593 a warning is also generated, noting that the
5594 @code{with} can be moved to the body. The default is that
5595 such warnings are not generated.
5596 This switch also activates warnings on unreferenced formals
5597 (it includes the effect of @option{-gnatwf}).
5598 This warning can also be turned on using @option{-gnatwa}.
5601 @emph{Suppress warnings on unused entities.}
5602 @cindex @option{-gnatwU} (@command{gcc})
5603 This switch suppresses warnings for unused entities and packages.
5604 It also turns off warnings on unreferenced formals (and thus includes
5605 the effect of @option{-gnatwF}).
5608 @emph{Activate warnings on unassigned variables.}
5609 @cindex @option{-gnatwv} (@command{gcc})
5610 @cindex Unassigned variable warnings
5611 This switch activates warnings for access to variables which
5612 may not be properly initialized. The default is that
5613 such warnings are generated.
5614 This warning can also be turned on using @option{-gnatwa}.
5617 @emph{Suppress warnings on unassigned variables.}
5618 @cindex @option{-gnatwV} (@command{gcc})
5619 This switch suppresses warnings for access to variables which
5620 may not be properly initialized.
5621 For variables of a composite type, the warning can also be suppressed in
5622 Ada 2005 by using a default initialization with a box. For example, if
5623 Table is an array of records whose components are only partially uninitialized,
5624 then the following code:
5626 @smallexample @c ada
5627 Tab : Table := (others => <>);
5630 will suppress warnings on subsequent statements that access components
5634 @emph{Activate warnings on wrong low bound assumption.}
5635 @cindex @option{-gnatww} (@command{gcc})
5636 @cindex String indexing warnings
5637 This switch activates warnings for indexing an unconstrained string parameter
5638 with a literal or S'Length. This is a case where the code is assuming that the
5639 low bound is one, which is in general not true (for example when a slice is
5640 passed). The default is that such warnings are generated.
5641 This warning can also be turned on using @option{-gnatwa}.
5644 @emph{Suppress warnings on wrong low bound assumption.}
5645 @cindex @option{-gnatwW} (@command{gcc})
5646 This switch suppresses warnings for indexing an unconstrained string parameter
5647 with a literal or S'Length. Note that this warning can also be suppressed
5648 in a particular case by adding an
5649 assertion that the lower bound is 1,
5650 as shown in the following example.
5652 @smallexample @c ada
5653 procedure K (S : String) is
5654 pragma Assert (S'First = 1);
5659 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5660 @cindex @option{-gnatw.w} (@command{gcc})
5661 @cindex Warnings Off control
5662 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5663 where either the pragma is entirely useless (because it suppresses no
5664 warnings), or it could be replaced by @code{pragma Unreferenced} or
5665 @code{pragma Unmodified}.The default is that these warnings are not given.
5666 Note that this warning is not included in -gnatwa, it must be
5667 activated explicitly.
5670 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5671 @cindex @option{-gnatw.W} (@command{gcc})
5672 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5675 @emph{Activate warnings on Export/Import pragmas.}
5676 @cindex @option{-gnatwx} (@command{gcc})
5677 @cindex Export/Import pragma warnings
5678 This switch activates warnings on Export/Import pragmas when
5679 the compiler detects a possible conflict between the Ada and
5680 foreign language calling sequences. For example, the use of
5681 default parameters in a convention C procedure is dubious
5682 because the C compiler cannot supply the proper default, so
5683 a warning is issued. The default is that such warnings are
5685 This warning can also be turned on using @option{-gnatwa}.
5688 @emph{Suppress warnings on Export/Import pragmas.}
5689 @cindex @option{-gnatwX} (@command{gcc})
5690 This switch suppresses warnings on Export/Import pragmas.
5691 The sense of this is that you are telling the compiler that
5692 you know what you are doing in writing the pragma, and it
5693 should not complain at you.
5696 @emph{Activate warnings for No_Exception_Propagation mode.}
5697 @cindex @option{-gnatwm} (@command{gcc})
5698 This switch activates warnings for exception usage when pragma Restrictions
5699 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5700 explicit exception raises which are not covered by a local handler, and for
5701 exception handlers which do not cover a local raise. The default is that these
5702 warnings are not given.
5705 @emph{Disable warnings for No_Exception_Propagation mode.}
5706 This switch disables warnings for exception usage when pragma Restrictions
5707 (No_Exception_Propagation) is in effect.
5710 @emph{Activate warnings for Ada 2005 compatibility issues.}
5711 @cindex @option{-gnatwy} (@command{gcc})
5712 @cindex Ada 2005 compatibility issues warnings
5713 For the most part Ada 2005 is upwards compatible with Ada 95,
5714 but there are some exceptions (for example the fact that
5715 @code{interface} is now a reserved word in Ada 2005). This
5716 switch activates several warnings to help in identifying
5717 and correcting such incompatibilities. The default is that
5718 these warnings are generated. Note that at one point Ada 2005
5719 was called Ada 0Y, hence the choice of character.
5720 This warning can also be turned on using @option{-gnatwa}.
5723 @emph{Disable warnings for Ada 2005 compatibility issues.}
5724 @cindex @option{-gnatwY} (@command{gcc})
5725 @cindex Ada 2005 compatibility issues warnings
5726 This switch suppresses several warnings intended to help in identifying
5727 incompatibilities between Ada 95 and Ada 2005.
5730 @emph{Activate warnings on unchecked conversions.}
5731 @cindex @option{-gnatwz} (@command{gcc})
5732 @cindex Unchecked_Conversion warnings
5733 This switch activates warnings for unchecked conversions
5734 where the types are known at compile time to have different
5736 is that such warnings are generated. Warnings are also
5737 generated for subprogram pointers with different conventions,
5738 and, on VMS only, for data pointers with different conventions.
5739 This warning can also be turned on using @option{-gnatwa}.
5742 @emph{Suppress warnings on unchecked conversions.}
5743 @cindex @option{-gnatwZ} (@command{gcc})
5744 This switch suppresses warnings for unchecked conversions
5745 where the types are known at compile time to have different
5746 sizes or conventions.
5748 @item ^-Wunused^WARNINGS=UNUSED^
5749 @cindex @option{-Wunused}
5750 The warnings controlled by the @option{-gnatw} switch are generated by
5751 the front end of the compiler. The @option{GCC} back end can provide
5752 additional warnings and they are controlled by the @option{-W} switch.
5753 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5754 warnings for entities that are declared but not referenced.
5756 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5757 @cindex @option{-Wuninitialized}
5758 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5759 the back end warning for uninitialized variables. This switch must be
5760 used in conjunction with an optimization level greater than zero.
5762 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5763 @cindex @option{-Wall}
5764 This switch enables all the above warnings from the @option{GCC} back end.
5765 The code generator detects a number of warning situations that are missed
5766 by the @option{GNAT} front end, and this switch can be used to activate them.
5767 The use of this switch also sets the default front end warning mode to
5768 @option{-gnatwa}, that is, most front end warnings activated as well.
5770 @item ^-w^/NO_BACK_END_WARNINGS^
5772 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5773 The use of this switch also sets the default front end warning mode to
5774 @option{-gnatws}, that is, front end warnings suppressed as well.
5780 A string of warning parameters can be used in the same parameter. For example:
5787 will turn on all optional warnings except for elaboration pragma warnings,
5788 and also specify that warnings should be treated as errors.
5790 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5815 @node Debugging and Assertion Control
5816 @subsection Debugging and Assertion Control
5820 @cindex @option{-gnata} (@command{gcc})
5826 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5827 are ignored. This switch, where @samp{a} stands for assert, causes
5828 @code{Assert} and @code{Debug} pragmas to be activated.
5830 The pragmas have the form:
5834 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5835 @var{static-string-expression}@r{]})
5836 @b{pragma} Debug (@var{procedure call})
5841 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5842 If the result is @code{True}, the pragma has no effect (other than
5843 possible side effects from evaluating the expression). If the result is
5844 @code{False}, the exception @code{Assert_Failure} declared in the package
5845 @code{System.Assertions} is
5846 raised (passing @var{static-string-expression}, if present, as the
5847 message associated with the exception). If no string expression is
5848 given the default is a string giving the file name and line number
5851 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5852 @code{pragma Debug} may appear within a declaration sequence, allowing
5853 debugging procedures to be called between declarations.
5856 @item /DEBUG@r{[}=debug-level@r{]}
5858 Specifies how much debugging information is to be included in
5859 the resulting object file where 'debug-level' is one of the following:
5862 Include both debugger symbol records and traceback
5864 This is the default setting.
5866 Include both debugger symbol records and traceback in
5869 Excludes both debugger symbol records and traceback
5870 the object file. Same as /NODEBUG.
5872 Includes only debugger symbol records in the object
5873 file. Note that this doesn't include traceback information.
5878 @node Validity Checking
5879 @subsection Validity Checking
5880 @findex Validity Checking
5883 The Ada Reference Manual defines the concept of invalid values (see
5884 RM 13.9.1). The primary source of invalid values is uninitialized
5885 variables. A scalar variable that is left uninitialized may contain
5886 an invalid value; the concept of invalid does not apply to access or
5889 It is an error to read an invalid value, but the RM does not require
5890 run-time checks to detect such errors, except for some minimal
5891 checking to prevent erroneous execution (i.e. unpredictable
5892 behavior). This corresponds to the @option{-gnatVd} switch below,
5893 which is the default. For example, by default, if the expression of a
5894 case statement is invalid, it will raise Constraint_Error rather than
5895 causing a wild jump, and if an array index on the left-hand side of an
5896 assignment is invalid, it will raise Constraint_Error rather than
5897 overwriting an arbitrary memory location.
5899 The @option{-gnatVa} may be used to enable additional validity checks,
5900 which are not required by the RM. These checks are often very
5901 expensive (which is why the RM does not require them). These checks
5902 are useful in tracking down uninitialized variables, but they are
5903 not usually recommended for production builds.
5905 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5906 control; you can enable whichever validity checks you desire. However,
5907 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5908 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5909 sufficient for non-debugging use.
5911 The @option{-gnatB} switch tells the compiler to assume that all
5912 values are valid (that is, within their declared subtype range)
5913 except in the context of a use of the Valid attribute. This means
5914 the compiler can generate more efficient code, since the range
5915 of values is better known at compile time. However, an uninitialized
5916 variable can cause wild jumps and memory corruption in this mode.
5918 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5919 checking mode as described below.
5921 The @code{x} argument is a string of letters that
5922 indicate validity checks that are performed or not performed in addition
5923 to the default checks required by Ada as described above.
5926 The options allowed for this qualifier
5927 indicate validity checks that are performed or not performed in addition
5928 to the default checks required by Ada as described above.
5934 @emph{All validity checks.}
5935 @cindex @option{-gnatVa} (@command{gcc})
5936 All validity checks are turned on.
5938 That is, @option{-gnatVa} is
5939 equivalent to @option{gnatVcdfimorst}.
5943 @emph{Validity checks for copies.}
5944 @cindex @option{-gnatVc} (@command{gcc})
5945 The right hand side of assignments, and the initializing values of
5946 object declarations are validity checked.
5949 @emph{Default (RM) validity checks.}
5950 @cindex @option{-gnatVd} (@command{gcc})
5951 Some validity checks are done by default following normal Ada semantics
5953 A check is done in case statements that the expression is within the range
5954 of the subtype. If it is not, Constraint_Error is raised.
5955 For assignments to array components, a check is done that the expression used
5956 as index is within the range. If it is not, Constraint_Error is raised.
5957 Both these validity checks may be turned off using switch @option{-gnatVD}.
5958 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5959 switch @option{-gnatVd} will leave the checks turned on.
5960 Switch @option{-gnatVD} should be used only if you are sure that all such
5961 expressions have valid values. If you use this switch and invalid values
5962 are present, then the program is erroneous, and wild jumps or memory
5963 overwriting may occur.
5966 @emph{Validity checks for elementary components.}
5967 @cindex @option{-gnatVe} (@command{gcc})
5968 In the absence of this switch, assignments to record or array components are
5969 not validity checked, even if validity checks for assignments generally
5970 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5971 require valid data, but assignment of individual components does. So for
5972 example, there is a difference between copying the elements of an array with a
5973 slice assignment, compared to assigning element by element in a loop. This
5974 switch allows you to turn off validity checking for components, even when they
5975 are assigned component by component.
5978 @emph{Validity checks for floating-point values.}
5979 @cindex @option{-gnatVf} (@command{gcc})
5980 In the absence of this switch, validity checking occurs only for discrete
5981 values. If @option{-gnatVf} is specified, then validity checking also applies
5982 for floating-point values, and NaNs and infinities are considered invalid,
5983 as well as out of range values for constrained types. Note that this means
5984 that standard IEEE infinity mode is not allowed. The exact contexts
5985 in which floating-point values are checked depends on the setting of other
5986 options. For example,
5987 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5988 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5989 (the order does not matter) specifies that floating-point parameters of mode
5990 @code{in} should be validity checked.
5993 @emph{Validity checks for @code{in} mode parameters}
5994 @cindex @option{-gnatVi} (@command{gcc})
5995 Arguments for parameters of mode @code{in} are validity checked in function
5996 and procedure calls at the point of call.
5999 @emph{Validity checks for @code{in out} mode parameters.}
6000 @cindex @option{-gnatVm} (@command{gcc})
6001 Arguments for parameters of mode @code{in out} are validity checked in
6002 procedure calls at the point of call. The @code{'m'} here stands for
6003 modify, since this concerns parameters that can be modified by the call.
6004 Note that there is no specific option to test @code{out} parameters,
6005 but any reference within the subprogram will be tested in the usual
6006 manner, and if an invalid value is copied back, any reference to it
6007 will be subject to validity checking.
6010 @emph{No validity checks.}
6011 @cindex @option{-gnatVn} (@command{gcc})
6012 This switch turns off all validity checking, including the default checking
6013 for case statements and left hand side subscripts. Note that the use of
6014 the switch @option{-gnatp} suppresses all run-time checks, including
6015 validity checks, and thus implies @option{-gnatVn}. When this switch
6016 is used, it cancels any other @option{-gnatV} previously issued.
6019 @emph{Validity checks for operator and attribute operands.}
6020 @cindex @option{-gnatVo} (@command{gcc})
6021 Arguments for predefined operators and attributes are validity checked.
6022 This includes all operators in package @code{Standard},
6023 the shift operators defined as intrinsic in package @code{Interfaces}
6024 and operands for attributes such as @code{Pos}. Checks are also made
6025 on individual component values for composite comparisons, and on the
6026 expressions in type conversions and qualified expressions. Checks are
6027 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6030 @emph{Validity checks for parameters.}
6031 @cindex @option{-gnatVp} (@command{gcc})
6032 This controls the treatment of parameters within a subprogram (as opposed
6033 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6034 of parameters on a call. If either of these call options is used, then
6035 normally an assumption is made within a subprogram that the input arguments
6036 have been validity checking at the point of call, and do not need checking
6037 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6038 is not made, and parameters are not assumed to be valid, so their validity
6039 will be checked (or rechecked) within the subprogram.
6042 @emph{Validity checks for function returns.}
6043 @cindex @option{-gnatVr} (@command{gcc})
6044 The expression in @code{return} statements in functions is validity
6048 @emph{Validity checks for subscripts.}
6049 @cindex @option{-gnatVs} (@command{gcc})
6050 All subscripts expressions are checked for validity, whether they appear
6051 on the right side or left side (in default mode only left side subscripts
6052 are validity checked).
6055 @emph{Validity checks for tests.}
6056 @cindex @option{-gnatVt} (@command{gcc})
6057 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6058 statements are checked, as well as guard expressions in entry calls.
6063 The @option{-gnatV} switch may be followed by
6064 ^a string of letters^a list of options^
6065 to turn on a series of validity checking options.
6067 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6068 specifies that in addition to the default validity checking, copies and
6069 function return expressions are to be validity checked.
6070 In order to make it easier
6071 to specify the desired combination of effects,
6073 the upper case letters @code{CDFIMORST} may
6074 be used to turn off the corresponding lower case option.
6077 the prefix @code{NO} on an option turns off the corresponding validity
6080 @item @code{NOCOPIES}
6081 @item @code{NODEFAULT}
6082 @item @code{NOFLOATS}
6083 @item @code{NOIN_PARAMS}
6084 @item @code{NOMOD_PARAMS}
6085 @item @code{NOOPERANDS}
6086 @item @code{NORETURNS}
6087 @item @code{NOSUBSCRIPTS}
6088 @item @code{NOTESTS}
6092 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6093 turns on all validity checking options except for
6094 checking of @code{@b{in out}} procedure arguments.
6096 The specification of additional validity checking generates extra code (and
6097 in the case of @option{-gnatVa} the code expansion can be substantial).
6098 However, these additional checks can be very useful in detecting
6099 uninitialized variables, incorrect use of unchecked conversion, and other
6100 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6101 is useful in conjunction with the extra validity checking, since this
6102 ensures that wherever possible uninitialized variables have invalid values.
6104 See also the pragma @code{Validity_Checks} which allows modification of
6105 the validity checking mode at the program source level, and also allows for
6106 temporary disabling of validity checks.
6108 @node Style Checking
6109 @subsection Style Checking
6110 @findex Style checking
6113 The @option{-gnaty^x^(option,option,@dots{})^} switch
6114 @cindex @option{-gnaty} (@command{gcc})
6115 causes the compiler to
6116 enforce specified style rules. A limited set of style rules has been used
6117 in writing the GNAT sources themselves. This switch allows user programs
6118 to activate all or some of these checks. If the source program fails a
6119 specified style check, an appropriate warning message is given, preceded by
6120 the character sequence ``(style)''.
6122 @code{(option,option,@dots{})} is a sequence of keywords
6125 The string @var{x} is a sequence of letters or digits
6127 indicating the particular style
6128 checks to be performed. The following checks are defined:
6133 @emph{Specify indentation level.}
6134 If a digit from 1-9 appears
6135 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6136 then proper indentation is checked, with the digit indicating the
6137 indentation level required. A value of zero turns off this style check.
6138 The general style of required indentation is as specified by
6139 the examples in the Ada Reference Manual. Full line comments must be
6140 aligned with the @code{--} starting on a column that is a multiple of
6141 the alignment level, or they may be aligned the same way as the following
6142 non-blank line (this is useful when full line comments appear in the middle
6146 @emph{Check attribute casing.}
6147 Attribute names, including the case of keywords such as @code{digits}
6148 used as attributes names, must be written in mixed case, that is, the
6149 initial letter and any letter following an underscore must be uppercase.
6150 All other letters must be lowercase.
6152 @item ^A^ARRAY_INDEXES^
6153 @emph{Use of array index numbers in array attributes.}
6154 When using the array attributes First, Last, Range,
6155 or Length, the index number must be omitted for one-dimensional arrays
6156 and is required for multi-dimensional arrays.
6159 @emph{Blanks not allowed at statement end.}
6160 Trailing blanks are not allowed at the end of statements. The purpose of this
6161 rule, together with h (no horizontal tabs), is to enforce a canonical format
6162 for the use of blanks to separate source tokens.
6164 @item ^B^BOOLEAN_OPERATORS^
6165 @emph{Check Boolean operators.}
6166 The use of AND/OR operators is not permitted except in the cases of modular
6167 operands, array operands, and simple stand-alone boolean variables or
6168 boolean constants. In all other cases AND THEN/OR ELSE are required.
6171 @emph{Check comments.}
6172 Comments must meet the following set of rules:
6177 The ``@code{--}'' that starts the column must either start in column one,
6178 or else at least one blank must precede this sequence.
6181 Comments that follow other tokens on a line must have at least one blank
6182 following the ``@code{--}'' at the start of the comment.
6185 Full line comments must have two blanks following the ``@code{--}'' that
6186 starts the comment, with the following exceptions.
6189 A line consisting only of the ``@code{--}'' characters, possibly preceded
6190 by blanks is permitted.
6193 A comment starting with ``@code{--x}'' where @code{x} is a special character
6195 This allows proper processing of the output generated by specialized tools
6196 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6198 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6199 special character is defined as being in one of the ASCII ranges
6200 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6201 Note that this usage is not permitted
6202 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6205 A line consisting entirely of minus signs, possibly preceded by blanks, is
6206 permitted. This allows the construction of box comments where lines of minus
6207 signs are used to form the top and bottom of the box.
6210 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6211 least one blank follows the initial ``@code{--}''. Together with the preceding
6212 rule, this allows the construction of box comments, as shown in the following
6215 ---------------------------
6216 -- This is a box comment --
6217 -- with two text lines. --
6218 ---------------------------
6222 @item ^d^DOS_LINE_ENDINGS^
6223 @emph{Check no DOS line terminators present.}
6224 All lines must be terminated by a single ASCII.LF
6225 character (in particular the DOS line terminator sequence CR/LF is not
6229 @emph{Check end/exit labels.}
6230 Optional labels on @code{end} statements ending subprograms and on
6231 @code{exit} statements exiting named loops, are required to be present.
6234 @emph{No form feeds or vertical tabs.}
6235 Neither form feeds nor vertical tab characters are permitted
6239 @emph{GNAT style mode}
6240 The set of style check switches is set to match that used by the GNAT sources.
6241 This may be useful when developing code that is eventually intended to be
6242 incorporated into GNAT. For further details, see GNAT sources.
6245 @emph{No horizontal tabs.}
6246 Horizontal tab characters are not permitted in the source text.
6247 Together with the b (no blanks at end of line) check, this
6248 enforces a canonical form for the use of blanks to separate
6252 @emph{Check if-then layout.}
6253 The keyword @code{then} must appear either on the same
6254 line as corresponding @code{if}, or on a line on its own, lined
6255 up under the @code{if} with at least one non-blank line in between
6256 containing all or part of the condition to be tested.
6259 @emph{check mode IN keywords}
6260 Mode @code{in} (the default mode) is not
6261 allowed to be given explicitly. @code{in out} is fine,
6262 but not @code{in} on its own.
6265 @emph{Check keyword casing.}
6266 All keywords must be in lower case (with the exception of keywords
6267 such as @code{digits} used as attribute names to which this check
6271 @emph{Check layout.}
6272 Layout of statement and declaration constructs must follow the
6273 recommendations in the Ada Reference Manual, as indicated by the
6274 form of the syntax rules. For example an @code{else} keyword must
6275 be lined up with the corresponding @code{if} keyword.
6277 There are two respects in which the style rule enforced by this check
6278 option are more liberal than those in the Ada Reference Manual. First
6279 in the case of record declarations, it is permissible to put the
6280 @code{record} keyword on the same line as the @code{type} keyword, and
6281 then the @code{end} in @code{end record} must line up under @code{type}.
6282 This is also permitted when the type declaration is split on two lines.
6283 For example, any of the following three layouts is acceptable:
6285 @smallexample @c ada
6308 Second, in the case of a block statement, a permitted alternative
6309 is to put the block label on the same line as the @code{declare} or
6310 @code{begin} keyword, and then line the @code{end} keyword up under
6311 the block label. For example both the following are permitted:
6313 @smallexample @c ada
6331 The same alternative format is allowed for loops. For example, both of
6332 the following are permitted:
6334 @smallexample @c ada
6336 Clear : while J < 10 loop
6347 @item ^Lnnn^MAX_NESTING=nnn^
6348 @emph{Set maximum nesting level}
6349 The maximum level of nesting of constructs (including subprograms, loops,
6350 blocks, packages, and conditionals) may not exceed the given value
6351 @option{nnn}. A value of zero disconnects this style check.
6353 @item ^m^LINE_LENGTH^
6354 @emph{Check maximum line length.}
6355 The length of source lines must not exceed 79 characters, including
6356 any trailing blanks. The value of 79 allows convenient display on an
6357 80 character wide device or window, allowing for possible special
6358 treatment of 80 character lines. Note that this count is of
6359 characters in the source text. This means that a tab character counts
6360 as one character in this count but a wide character sequence counts as
6361 a single character (however many bytes are needed in the encoding).
6363 @item ^Mnnn^MAX_LENGTH=nnn^
6364 @emph{Set maximum line length.}
6365 The length of lines must not exceed the
6366 given value @option{nnn}. The maximum value that can be specified is 32767.
6368 @item ^n^STANDARD_CASING^
6369 @emph{Check casing of entities in Standard.}
6370 Any identifier from Standard must be cased
6371 to match the presentation in the Ada Reference Manual (for example,
6372 @code{Integer} and @code{ASCII.NUL}).
6375 @emph{Turn off all style checks}
6376 All style check options are turned off.
6378 @item ^o^ORDERED_SUBPROGRAMS^
6379 @emph{Check order of subprogram bodies.}
6380 All subprogram bodies in a given scope
6381 (e.g.@: a package body) must be in alphabetical order. The ordering
6382 rule uses normal Ada rules for comparing strings, ignoring casing
6383 of letters, except that if there is a trailing numeric suffix, then
6384 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6387 @item ^O^OVERRIDING_INDICATORS^
6388 @emph{Check that overriding subprograms are explicitly marked as such.}
6389 The declaration of a primitive operation of a type extension that overrides
6390 an inherited operation must carry an overriding indicator.
6393 @emph{Check pragma casing.}
6394 Pragma names must be written in mixed case, that is, the
6395 initial letter and any letter following an underscore must be uppercase.
6396 All other letters must be lowercase.
6398 @item ^r^REFERENCES^
6399 @emph{Check references.}
6400 All identifier references must be cased in the same way as the
6401 corresponding declaration. No specific casing style is imposed on
6402 identifiers. The only requirement is for consistency of references
6405 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6406 @emph{Check no statements after THEN/ELSE.}
6407 No statements are allowed
6408 on the same line as a THEN or ELSE keyword following the
6409 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6410 and a special exception allows a pragma to appear after ELSE.
6413 @emph{Check separate specs.}
6414 Separate declarations (``specs'') are required for subprograms (a
6415 body is not allowed to serve as its own declaration). The only
6416 exception is that parameterless library level procedures are
6417 not required to have a separate declaration. This exception covers
6418 the most frequent form of main program procedures.
6421 @emph{Check token spacing.}
6422 The following token spacing rules are enforced:
6427 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6430 The token @code{=>} must be surrounded by spaces.
6433 The token @code{<>} must be preceded by a space or a left parenthesis.
6436 Binary operators other than @code{**} must be surrounded by spaces.
6437 There is no restriction on the layout of the @code{**} binary operator.
6440 Colon must be surrounded by spaces.
6443 Colon-equal (assignment, initialization) must be surrounded by spaces.
6446 Comma must be the first non-blank character on the line, or be
6447 immediately preceded by a non-blank character, and must be followed
6451 If the token preceding a left parenthesis ends with a letter or digit, then
6452 a space must separate the two tokens.
6455 if the token following a right parenthesis starts with a letter or digit, then
6456 a space must separate the two tokens.
6459 A right parenthesis must either be the first non-blank character on
6460 a line, or it must be preceded by a non-blank character.
6463 A semicolon must not be preceded by a space, and must not be followed by
6464 a non-blank character.
6467 A unary plus or minus may not be followed by a space.
6470 A vertical bar must be surrounded by spaces.
6473 @item ^u^UNNECESSARY_BLANK_LINES^
6474 @emph{Check unnecessary blank lines.}
6475 Unnecessary blank lines are not allowed. A blank line is considered
6476 unnecessary if it appears at the end of the file, or if more than
6477 one blank line occurs in sequence.
6479 @item ^x^XTRA_PARENS^
6480 @emph{Check extra parentheses.}
6481 Unnecessary extra level of parentheses (C-style) are not allowed
6482 around conditions in @code{if} statements, @code{while} statements and
6483 @code{exit} statements.
6485 @item ^y^ALL_BUILTIN^
6486 @emph{Set all standard style check options}
6487 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6488 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6489 @option{-gnatyS}, @option{-gnatyLnnn},
6490 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6494 @emph{Remove style check options}
6495 This causes any subsequent options in the string to act as canceling the
6496 corresponding style check option. To cancel maximum nesting level control,
6497 use @option{L} parameter witout any integer value after that, because any
6498 digit following @option{-} in the parameter string of the @option{-gnaty}
6499 option will be threated as canceling indentation check. The same is true
6500 for @option{M} parameter. @option{y} and @option{N} parameters are not
6501 allowed after @option{-}.
6504 This causes any subsequent options in the string to enable the corresponding
6505 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6511 @emph{Removing style check options}
6512 If the name of a style check is preceded by @option{NO} then the corresponding
6513 style check is turned off. For example @option{NOCOMMENTS} turns off style
6514 checking for comments.
6519 In the above rules, appearing in column one is always permitted, that is,
6520 counts as meeting either a requirement for a required preceding space,
6521 or as meeting a requirement for no preceding space.
6523 Appearing at the end of a line is also always permitted, that is, counts
6524 as meeting either a requirement for a following space, or as meeting
6525 a requirement for no following space.
6528 If any of these style rules is violated, a message is generated giving
6529 details on the violation. The initial characters of such messages are
6530 always ``@code{(style)}''. Note that these messages are treated as warning
6531 messages, so they normally do not prevent the generation of an object
6532 file. The @option{-gnatwe} switch can be used to treat warning messages,
6533 including style messages, as fatal errors.
6537 @option{-gnaty} on its own (that is not
6538 followed by any letters or digits), then the effect is equivalent
6539 to the use of @option{-gnatyy}, as described above, that is all
6540 built-in standard style check options are enabled.
6544 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6545 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6546 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6556 clears any previously set style checks.
6558 @node Run-Time Checks
6559 @subsection Run-Time Checks
6560 @cindex Division by zero
6561 @cindex Access before elaboration
6562 @cindex Checks, division by zero
6563 @cindex Checks, access before elaboration
6564 @cindex Checks, stack overflow checking
6567 By default, the following checks are suppressed: integer overflow
6568 checks, stack overflow checks, and checks for access before
6569 elaboration on subprogram calls. All other checks, including range
6570 checks and array bounds checks, are turned on by default. The
6571 following @command{gcc} switches refine this default behavior.
6576 @cindex @option{-gnatp} (@command{gcc})
6577 @cindex Suppressing checks
6578 @cindex Checks, suppressing
6580 This switch causes the unit to be compiled
6581 as though @code{pragma Suppress (All_checks)}
6582 had been present in the source. Validity checks are also eliminated (in
6583 other words @option{-gnatp} also implies @option{-gnatVn}.
6584 Use this switch to improve the performance
6585 of the code at the expense of safety in the presence of invalid data or
6588 Note that when checks are suppressed, the compiler is allowed, but not
6589 required, to omit the checking code. If the run-time cost of the
6590 checking code is zero or near-zero, the compiler will generate it even
6591 if checks are suppressed. In particular, if the compiler can prove
6592 that a certain check will necessarily fail, it will generate code to
6593 do an unconditional ``raise'', even if checks are suppressed. The
6594 compiler warns in this case. Another case in which checks may not be
6595 eliminated is when they are embedded in certain run time routines such
6596 as math library routines.
6598 Of course, run-time checks are omitted whenever the compiler can prove
6599 that they will not fail, whether or not checks are suppressed.
6601 Note that if you suppress a check that would have failed, program
6602 execution is erroneous, which means the behavior is totally
6603 unpredictable. The program might crash, or print wrong answers, or
6604 do anything else. It might even do exactly what you wanted it to do
6605 (and then it might start failing mysteriously next week or next
6606 year). The compiler will generate code based on the assumption that
6607 the condition being checked is true, which can result in disaster if
6608 that assumption is wrong.
6611 @cindex @option{-gnato} (@command{gcc})
6612 @cindex Overflow checks
6613 @cindex Check, overflow
6614 Enables overflow checking for integer operations.
6615 This causes GNAT to generate slower and larger executable
6616 programs by adding code to check for overflow (resulting in raising
6617 @code{Constraint_Error} as required by standard Ada
6618 semantics). These overflow checks correspond to situations in which
6619 the true value of the result of an operation may be outside the base
6620 range of the result type. The following example shows the distinction:
6622 @smallexample @c ada
6623 X1 : Integer := "Integer'Last";
6624 X2 : Integer range 1 .. 5 := "5";
6625 X3 : Integer := "Integer'Last";
6626 X4 : Integer range 1 .. 5 := "5";
6627 F : Float := "2.0E+20";
6636 Note that if explicit values are assigned at compile time, the
6637 compiler may be able to detect overflow at compile time, in which case
6638 no actual run-time checking code is required, and Constraint_Error
6639 will be raised unconditionally, with or without
6640 @option{-gnato}. That's why the assigned values in the above fragment
6641 are in quotes, the meaning is "assign a value not known to the
6642 compiler that happens to be equal to ...". The remaining discussion
6643 assumes that the compiler cannot detect the values at compile time.
6645 Here the first addition results in a value that is outside the base range
6646 of Integer, and hence requires an overflow check for detection of the
6647 constraint error. Thus the first assignment to @code{X1} raises a
6648 @code{Constraint_Error} exception only if @option{-gnato} is set.
6650 The second increment operation results in a violation of the explicit
6651 range constraint; such range checks are performed by default, and are
6652 unaffected by @option{-gnato}.
6654 The two conversions of @code{F} both result in values that are outside
6655 the base range of type @code{Integer} and thus will raise
6656 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6657 The fact that the result of the second conversion is assigned to
6658 variable @code{X4} with a restricted range is irrelevant, since the problem
6659 is in the conversion, not the assignment.
6661 Basically the rule is that in the default mode (@option{-gnato} not
6662 used), the generated code assures that all integer variables stay
6663 within their declared ranges, or within the base range if there is
6664 no declared range. This prevents any serious problems like indexes
6665 out of range for array operations.
6667 What is not checked in default mode is an overflow that results in
6668 an in-range, but incorrect value. In the above example, the assignments
6669 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6670 range of the target variable, but the result is wrong in the sense that
6671 it is too large to be represented correctly. Typically the assignment
6672 to @code{X1} will result in wrap around to the largest negative number.
6673 The conversions of @code{F} will result in some @code{Integer} value
6674 and if that integer value is out of the @code{X4} range then the
6675 subsequent assignment would generate an exception.
6677 @findex Machine_Overflows
6678 Note that the @option{-gnato} switch does not affect the code generated
6679 for any floating-point operations; it applies only to integer
6681 For floating-point, GNAT has the @code{Machine_Overflows}
6682 attribute set to @code{False} and the normal mode of operation is to
6683 generate IEEE NaN and infinite values on overflow or invalid operations
6684 (such as dividing 0.0 by 0.0).
6686 The reason that we distinguish overflow checking from other kinds of
6687 range constraint checking is that a failure of an overflow check, unlike
6688 for example the failure of a range check, can result in an incorrect
6689 value, but cannot cause random memory destruction (like an out of range
6690 subscript), or a wild jump (from an out of range case value). Overflow
6691 checking is also quite expensive in time and space, since in general it
6692 requires the use of double length arithmetic.
6694 Note again that @option{-gnato} is off by default, so overflow checking is
6695 not performed in default mode. This means that out of the box, with the
6696 default settings, GNAT does not do all the checks expected from the
6697 language description in the Ada Reference Manual. If you want all constraint
6698 checks to be performed, as described in this Manual, then you must
6699 explicitly use the -gnato switch either on the @command{gnatmake} or
6700 @command{gcc} command.
6703 @cindex @option{-gnatE} (@command{gcc})
6704 @cindex Elaboration checks
6705 @cindex Check, elaboration
6706 Enables dynamic checks for access-before-elaboration
6707 on subprogram calls and generic instantiations.
6708 Note that @option{-gnatE} is not necessary for safety, because in the
6709 default mode, GNAT ensures statically that the checks would not fail.
6710 For full details of the effect and use of this switch,
6711 @xref{Compiling Using gcc}.
6714 @cindex @option{-fstack-check} (@command{gcc})
6715 @cindex Stack Overflow Checking
6716 @cindex Checks, stack overflow checking
6717 Activates stack overflow checking. For full details of the effect and use of
6718 this switch see @ref{Stack Overflow Checking}.
6723 The setting of these switches only controls the default setting of the
6724 checks. You may modify them using either @code{Suppress} (to remove
6725 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6728 @node Using gcc for Syntax Checking
6729 @subsection Using @command{gcc} for Syntax Checking
6732 @cindex @option{-gnats} (@command{gcc})
6736 The @code{s} stands for ``syntax''.
6739 Run GNAT in syntax checking only mode. For
6740 example, the command
6743 $ gcc -c -gnats x.adb
6747 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6748 series of files in a single command
6750 , and can use wild cards to specify such a group of files.
6751 Note that you must specify the @option{-c} (compile
6752 only) flag in addition to the @option{-gnats} flag.
6755 You may use other switches in conjunction with @option{-gnats}. In
6756 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6757 format of any generated error messages.
6759 When the source file is empty or contains only empty lines and/or comments,
6760 the output is a warning:
6763 $ gcc -c -gnats -x ada toto.txt
6764 toto.txt:1:01: warning: empty file, contains no compilation units
6768 Otherwise, the output is simply the error messages, if any. No object file or
6769 ALI file is generated by a syntax-only compilation. Also, no units other
6770 than the one specified are accessed. For example, if a unit @code{X}
6771 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6772 check only mode does not access the source file containing unit
6775 @cindex Multiple units, syntax checking
6776 Normally, GNAT allows only a single unit in a source file. However, this
6777 restriction does not apply in syntax-check-only mode, and it is possible
6778 to check a file containing multiple compilation units concatenated
6779 together. This is primarily used by the @code{gnatchop} utility
6780 (@pxref{Renaming Files Using gnatchop}).
6783 @node Using gcc for Semantic Checking
6784 @subsection Using @command{gcc} for Semantic Checking
6787 @cindex @option{-gnatc} (@command{gcc})
6791 The @code{c} stands for ``check''.
6793 Causes the compiler to operate in semantic check mode,
6794 with full checking for all illegalities specified in the
6795 Ada Reference Manual, but without generation of any object code
6796 (no object file is generated).
6798 Because dependent files must be accessed, you must follow the GNAT
6799 semantic restrictions on file structuring to operate in this mode:
6803 The needed source files must be accessible
6804 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6807 Each file must contain only one compilation unit.
6810 The file name and unit name must match (@pxref{File Naming Rules}).
6813 The output consists of error messages as appropriate. No object file is
6814 generated. An @file{ALI} file is generated for use in the context of
6815 cross-reference tools, but this file is marked as not being suitable
6816 for binding (since no object file is generated).
6817 The checking corresponds exactly to the notion of
6818 legality in the Ada Reference Manual.
6820 Any unit can be compiled in semantics-checking-only mode, including
6821 units that would not normally be compiled (subunits,
6822 and specifications where a separate body is present).
6825 @node Compiling Different Versions of Ada
6826 @subsection Compiling Different Versions of Ada
6829 The switches described in this section allow you to explicitly specify
6830 the version of the Ada language that your programs are written in.
6831 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6832 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6833 indicate Ada 83 compatibility mode.
6836 @cindex Compatibility with Ada 83
6838 @item -gnat83 (Ada 83 Compatibility Mode)
6839 @cindex @option{-gnat83} (@command{gcc})
6840 @cindex ACVC, Ada 83 tests
6844 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6845 specifies that the program is to be compiled in Ada 83 mode. With
6846 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6847 semantics where this can be done easily.
6848 It is not possible to guarantee this switch does a perfect
6849 job; some subtle tests, such as are
6850 found in earlier ACVC tests (and that have been removed from the ACATS suite
6851 for Ada 95), might not compile correctly.
6852 Nevertheless, this switch may be useful in some circumstances, for example
6853 where, due to contractual reasons, existing code needs to be maintained
6854 using only Ada 83 features.
6856 With few exceptions (most notably the need to use @code{<>} on
6857 @cindex Generic formal parameters
6858 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6859 reserved words, and the use of packages
6860 with optional bodies), it is not necessary to specify the
6861 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6862 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6863 a correct Ada 83 program is usually also a correct program
6864 in these later versions of the language standard.
6865 For further information, please refer to @ref{Compatibility and Porting Guide}.
6867 @item -gnat95 (Ada 95 mode)
6868 @cindex @option{-gnat95} (@command{gcc})
6872 This switch directs the compiler to implement the Ada 95 version of the
6874 Since Ada 95 is almost completely upwards
6875 compatible with Ada 83, Ada 83 programs may generally be compiled using
6876 this switch (see the description of the @option{-gnat83} switch for further
6877 information about Ada 83 mode).
6878 If an Ada 2005 program is compiled in Ada 95 mode,
6879 uses of the new Ada 2005 features will cause error
6880 messages or warnings.
6882 This switch also can be used to cancel the effect of a previous
6883 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6885 @item -gnat05 (Ada 2005 mode)
6886 @cindex @option{-gnat05} (@command{gcc})
6887 @cindex Ada 2005 mode
6890 This switch directs the compiler to implement the Ada 2005 version of the
6892 Since Ada 2005 is almost completely upwards
6893 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6894 may generally be compiled using this switch (see the description of the
6895 @option{-gnat83} and @option{-gnat95} switches for further
6898 For information about the approved ``Ada Issues'' that have been incorporated
6899 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6900 Included with GNAT releases is a file @file{features-ada0y} that describes
6901 the set of implemented Ada 2005 features.
6905 @node Character Set Control
6906 @subsection Character Set Control
6908 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6909 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6912 Normally GNAT recognizes the Latin-1 character set in source program
6913 identifiers, as described in the Ada Reference Manual.
6915 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6916 single character ^^or word^ indicating the character set, as follows:
6920 ISO 8859-1 (Latin-1) identifiers
6923 ISO 8859-2 (Latin-2) letters allowed in identifiers
6926 ISO 8859-3 (Latin-3) letters allowed in identifiers
6929 ISO 8859-4 (Latin-4) letters allowed in identifiers
6932 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6935 ISO 8859-15 (Latin-9) letters allowed in identifiers
6938 IBM PC letters (code page 437) allowed in identifiers
6941 IBM PC letters (code page 850) allowed in identifiers
6943 @item ^f^FULL_UPPER^
6944 Full upper-half codes allowed in identifiers
6947 No upper-half codes allowed in identifiers
6950 Wide-character codes (that is, codes greater than 255)
6951 allowed in identifiers
6954 @xref{Foreign Language Representation}, for full details on the
6955 implementation of these character sets.
6957 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6958 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6959 Specify the method of encoding for wide characters.
6960 @var{e} is one of the following:
6965 Hex encoding (brackets coding also recognized)
6968 Upper half encoding (brackets encoding also recognized)
6971 Shift/JIS encoding (brackets encoding also recognized)
6974 EUC encoding (brackets encoding also recognized)
6977 UTF-8 encoding (brackets encoding also recognized)
6980 Brackets encoding only (default value)
6982 For full details on these encoding
6983 methods see @ref{Wide Character Encodings}.
6984 Note that brackets coding is always accepted, even if one of the other
6985 options is specified, so for example @option{-gnatW8} specifies that both
6986 brackets and UTF-8 encodings will be recognized. The units that are
6987 with'ed directly or indirectly will be scanned using the specified
6988 representation scheme, and so if one of the non-brackets scheme is
6989 used, it must be used consistently throughout the program. However,
6990 since brackets encoding is always recognized, it may be conveniently
6991 used in standard libraries, allowing these libraries to be used with
6992 any of the available coding schemes.
6995 If no @option{-gnatW?} parameter is present, then the default
6996 representation is normally Brackets encoding only. However, if the
6997 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6998 byte order mark or BOM for UTF-8), then these three characters are
6999 skipped and the default representation for the file is set to UTF-8.
7001 Note that the wide character representation that is specified (explicitly
7002 or by default) for the main program also acts as the default encoding used
7003 for Wide_Text_IO files if not specifically overridden by a WCEM form
7007 @node File Naming Control
7008 @subsection File Naming Control
7011 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
7012 @cindex @option{-gnatk} (@command{gcc})
7013 Activates file name ``krunching''. @var{n}, a decimal integer in the range
7014 1-999, indicates the maximum allowable length of a file name (not
7015 including the @file{.ads} or @file{.adb} extension). The default is not
7016 to enable file name krunching.
7018 For the source file naming rules, @xref{File Naming Rules}.
7021 @node Subprogram Inlining Control
7022 @subsection Subprogram Inlining Control
7027 @cindex @option{-gnatn} (@command{gcc})
7029 The @code{n} here is intended to suggest the first syllable of the
7032 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7033 inlining to actually occur, optimization must be enabled. To enable
7034 inlining of subprograms specified by pragma @code{Inline},
7035 you must also specify this switch.
7036 In the absence of this switch, GNAT does not attempt
7037 inlining and does not need to access the bodies of
7038 subprograms for which @code{pragma Inline} is specified if they are not
7039 in the current unit.
7041 If you specify this switch the compiler will access these bodies,
7042 creating an extra source dependency for the resulting object file, and
7043 where possible, the call will be inlined.
7044 For further details on when inlining is possible
7045 see @ref{Inlining of Subprograms}.
7048 @cindex @option{-gnatN} (@command{gcc})
7049 This switch activates front-end inlining which also
7050 generates additional dependencies.
7052 When using a gcc-based back end (in practice this means using any version
7053 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7054 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7055 Historically front end inlining was more extensive than the gcc back end
7056 inlining, but that is no longer the case.
7059 @node Auxiliary Output Control
7060 @subsection Auxiliary Output Control
7064 @cindex @option{-gnatt} (@command{gcc})
7065 @cindex Writing internal trees
7066 @cindex Internal trees, writing to file
7067 Causes GNAT to write the internal tree for a unit to a file (with the
7068 extension @file{.adt}.
7069 This not normally required, but is used by separate analysis tools.
7071 these tools do the necessary compilations automatically, so you should
7072 not have to specify this switch in normal operation.
7073 Note that the combination of switches @option{-gnatct}
7074 generates a tree in the form required by ASIS applications.
7077 @cindex @option{-gnatu} (@command{gcc})
7078 Print a list of units required by this compilation on @file{stdout}.
7079 The listing includes all units on which the unit being compiled depends
7080 either directly or indirectly.
7083 @item -pass-exit-codes
7084 @cindex @option{-pass-exit-codes} (@command{gcc})
7085 If this switch is not used, the exit code returned by @command{gcc} when
7086 compiling multiple files indicates whether all source files have
7087 been successfully used to generate object files or not.
7089 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7090 exit status and allows an integrated development environment to better
7091 react to a compilation failure. Those exit status are:
7095 There was an error in at least one source file.
7097 At least one source file did not generate an object file.
7099 The compiler died unexpectedly (internal error for example).
7101 An object file has been generated for every source file.
7106 @node Debugging Control
7107 @subsection Debugging Control
7111 @cindex Debugging options
7114 @cindex @option{-gnatd} (@command{gcc})
7115 Activate internal debugging switches. @var{x} is a letter or digit, or
7116 string of letters or digits, which specifies the type of debugging
7117 outputs desired. Normally these are used only for internal development
7118 or system debugging purposes. You can find full documentation for these
7119 switches in the body of the @code{Debug} unit in the compiler source
7120 file @file{debug.adb}.
7124 @cindex @option{-gnatG} (@command{gcc})
7125 This switch causes the compiler to generate auxiliary output containing
7126 a pseudo-source listing of the generated expanded code. Like most Ada
7127 compilers, GNAT works by first transforming the high level Ada code into
7128 lower level constructs. For example, tasking operations are transformed
7129 into calls to the tasking run-time routines. A unique capability of GNAT
7130 is to list this expanded code in a form very close to normal Ada source.
7131 This is very useful in understanding the implications of various Ada
7132 usage on the efficiency of the generated code. There are many cases in
7133 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7134 generate a lot of run-time code. By using @option{-gnatG} you can identify
7135 these cases, and consider whether it may be desirable to modify the coding
7136 approach to improve efficiency.
7138 The optional parameter @code{nn} if present after -gnatG specifies an
7139 alternative maximum line length that overrides the normal default of 72.
7140 This value is in the range 40-999999, values less than 40 being silently
7141 reset to 40. The equal sign is optional.
7143 The format of the output is very similar to standard Ada source, and is
7144 easily understood by an Ada programmer. The following special syntactic
7145 additions correspond to low level features used in the generated code that
7146 do not have any exact analogies in pure Ada source form. The following
7147 is a partial list of these special constructions. See the spec
7148 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7150 If the switch @option{-gnatL} is used in conjunction with
7151 @cindex @option{-gnatL} (@command{gcc})
7152 @option{-gnatG}, then the original source lines are interspersed
7153 in the expanded source (as comment lines with the original line number).
7156 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7157 Shows the storage pool being used for an allocator.
7159 @item at end @var{procedure-name};
7160 Shows the finalization (cleanup) procedure for a scope.
7162 @item (if @var{expr} then @var{expr} else @var{expr})
7163 Conditional expression equivalent to the @code{x?y:z} construction in C.
7165 @item @var{target}^^^(@var{source})
7166 A conversion with floating-point truncation instead of rounding.
7168 @item @var{target}?(@var{source})
7169 A conversion that bypasses normal Ada semantic checking. In particular
7170 enumeration types and fixed-point types are treated simply as integers.
7172 @item @var{target}?^^^(@var{source})
7173 Combines the above two cases.
7175 @item @var{x} #/ @var{y}
7176 @itemx @var{x} #mod @var{y}
7177 @itemx @var{x} #* @var{y}
7178 @itemx @var{x} #rem @var{y}
7179 A division or multiplication of fixed-point values which are treated as
7180 integers without any kind of scaling.
7182 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7183 Shows the storage pool associated with a @code{free} statement.
7185 @item [subtype or type declaration]
7186 Used to list an equivalent declaration for an internally generated
7187 type that is referenced elsewhere in the listing.
7189 @item freeze @var{type-name} @ovar{actions}
7190 Shows the point at which @var{type-name} is frozen, with possible
7191 associated actions to be performed at the freeze point.
7193 @item reference @var{itype}
7194 Reference (and hence definition) to internal type @var{itype}.
7196 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7197 Intrinsic function call.
7199 @item @var{label-name} : label
7200 Declaration of label @var{labelname}.
7202 @item #$ @var{subprogram-name}
7203 An implicit call to a run-time support routine
7204 (to meet the requirement of H.3.1(9) in a
7207 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7208 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7209 @var{expr}, but handled more efficiently).
7211 @item [constraint_error]
7212 Raise the @code{Constraint_Error} exception.
7214 @item @var{expression}'reference
7215 A pointer to the result of evaluating @var{expression}.
7217 @item @var{target-type}!(@var{source-expression})
7218 An unchecked conversion of @var{source-expression} to @var{target-type}.
7220 @item [@var{numerator}/@var{denominator}]
7221 Used to represent internal real literals (that) have no exact
7222 representation in base 2-16 (for example, the result of compile time
7223 evaluation of the expression 1.0/27.0).
7227 @cindex @option{-gnatD} (@command{gcc})
7228 When used in conjunction with @option{-gnatG}, this switch causes
7229 the expanded source, as described above for
7230 @option{-gnatG} to be written to files with names
7231 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7232 instead of to the standard output file. For
7233 example, if the source file name is @file{hello.adb}, then a file
7234 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7235 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7236 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7237 you to do source level debugging using the generated code which is
7238 sometimes useful for complex code, for example to find out exactly
7239 which part of a complex construction raised an exception. This switch
7240 also suppress generation of cross-reference information (see
7241 @option{-gnatx}) since otherwise the cross-reference information
7242 would refer to the @file{^.dg^.DG^} file, which would cause
7243 confusion since this is not the original source file.
7245 Note that @option{-gnatD} actually implies @option{-gnatG}
7246 automatically, so it is not necessary to give both options.
7247 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7249 If the switch @option{-gnatL} is used in conjunction with
7250 @cindex @option{-gnatL} (@command{gcc})
7251 @option{-gnatDG}, then the original source lines are interspersed
7252 in the expanded source (as comment lines with the original line number).
7254 The optional parameter @code{nn} if present after -gnatD specifies an
7255 alternative maximum line length that overrides the normal default of 72.
7256 This value is in the range 40-999999, values less than 40 being silently
7257 reset to 40. The equal sign is optional.
7260 @cindex @option{-gnatr} (@command{gcc})
7261 @cindex pragma Restrictions
7262 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7263 so that violation of restrictions causes warnings rather than illegalities.
7264 This is useful during the development process when new restrictions are added
7265 or investigated. The switch also causes pragma Profile to be treated as
7266 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7267 restriction warnings rather than restrictions.
7270 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7271 @cindex @option{-gnatR} (@command{gcc})
7272 This switch controls output from the compiler of a listing showing
7273 representation information for declared types and objects. For
7274 @option{-gnatR0}, no information is output (equivalent to omitting
7275 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7276 so @option{-gnatR} with no parameter has the same effect), size and alignment
7277 information is listed for declared array and record types. For
7278 @option{-gnatR2}, size and alignment information is listed for all
7279 declared types and objects. Finally @option{-gnatR3} includes symbolic
7280 expressions for values that are computed at run time for
7281 variant records. These symbolic expressions have a mostly obvious
7282 format with #n being used to represent the value of the n'th
7283 discriminant. See source files @file{repinfo.ads/adb} in the
7284 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7285 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7286 the output is to a file with the name @file{^file.rep^file_REP^} where
7287 file is the name of the corresponding source file.
7290 @item /REPRESENTATION_INFO
7291 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7292 This qualifier controls output from the compiler of a listing showing
7293 representation information for declared types and objects. For
7294 @option{/REPRESENTATION_INFO=NONE}, no information is output
7295 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7296 @option{/REPRESENTATION_INFO} without option is equivalent to
7297 @option{/REPRESENTATION_INFO=ARRAYS}.
7298 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7299 information is listed for declared array and record types. For
7300 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7301 is listed for all expression information for values that are computed
7302 at run time for variant records. These symbolic expressions have a mostly
7303 obvious format with #n being used to represent the value of the n'th
7304 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7305 @code{GNAT} sources for full details on the format of
7306 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7307 If _FILE is added at the end of an option
7308 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7309 then the output is to a file with the name @file{file_REP} where
7310 file is the name of the corresponding source file.
7312 Note that it is possible for record components to have zero size. In
7313 this case, the component clause uses an obvious extension of permitted
7314 Ada syntax, for example @code{at 0 range 0 .. -1}.
7316 Representation information requires that code be generated (since it is the
7317 code generator that lays out complex data structures). If an attempt is made
7318 to output representation information when no code is generated, for example
7319 when a subunit is compiled on its own, then no information can be generated
7320 and the compiler outputs a message to this effect.
7323 @cindex @option{-gnatS} (@command{gcc})
7324 The use of the switch @option{-gnatS} for an
7325 Ada compilation will cause the compiler to output a
7326 representation of package Standard in a form very
7327 close to standard Ada. It is not quite possible to
7328 do this entirely in standard Ada (since new
7329 numeric base types cannot be created in standard
7330 Ada), but the output is easily
7331 readable to any Ada programmer, and is useful to
7332 determine the characteristics of target dependent
7333 types in package Standard.
7336 @cindex @option{-gnatx} (@command{gcc})
7337 Normally the compiler generates full cross-referencing information in
7338 the @file{ALI} file. This information is used by a number of tools,
7339 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7340 suppresses this information. This saves some space and may slightly
7341 speed up compilation, but means that these tools cannot be used.
7344 @node Exception Handling Control
7345 @subsection Exception Handling Control
7348 GNAT uses two methods for handling exceptions at run-time. The
7349 @code{setjmp/longjmp} method saves the context when entering
7350 a frame with an exception handler. Then when an exception is
7351 raised, the context can be restored immediately, without the
7352 need for tracing stack frames. This method provides very fast
7353 exception propagation, but introduces significant overhead for
7354 the use of exception handlers, even if no exception is raised.
7356 The other approach is called ``zero cost'' exception handling.
7357 With this method, the compiler builds static tables to describe
7358 the exception ranges. No dynamic code is required when entering
7359 a frame containing an exception handler. When an exception is
7360 raised, the tables are used to control a back trace of the
7361 subprogram invocation stack to locate the required exception
7362 handler. This method has considerably poorer performance for
7363 the propagation of exceptions, but there is no overhead for
7364 exception handlers if no exception is raised. Note that in this
7365 mode and in the context of mixed Ada and C/C++ programming,
7366 to propagate an exception through a C/C++ code, the C/C++ code
7367 must be compiled with the @option{-funwind-tables} GCC's
7370 The following switches may be used to control which of the
7371 two exception handling methods is used.
7377 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7378 This switch causes the setjmp/longjmp run-time (when available) to be used
7379 for exception handling. If the default
7380 mechanism for the target is zero cost exceptions, then
7381 this switch can be used to modify this default, and must be
7382 used for all units in the partition.
7383 This option is rarely used. One case in which it may be
7384 advantageous is if you have an application where exception
7385 raising is common and the overall performance of the
7386 application is improved by favoring exception propagation.
7389 @cindex @option{--RTS=zcx} (@command{gnatmake})
7390 @cindex Zero Cost Exceptions
7391 This switch causes the zero cost approach to be used
7392 for exception handling. If this is the default mechanism for the
7393 target (see below), then this switch is unneeded. If the default
7394 mechanism for the target is setjmp/longjmp exceptions, then
7395 this switch can be used to modify this default, and must be
7396 used for all units in the partition.
7397 This option can only be used if the zero cost approach
7398 is available for the target in use, otherwise it will generate an error.
7402 The same option @option{--RTS} must be used both for @command{gcc}
7403 and @command{gnatbind}. Passing this option to @command{gnatmake}
7404 (@pxref{Switches for gnatmake}) will ensure the required consistency
7405 through the compilation and binding steps.
7407 @node Units to Sources Mapping Files
7408 @subsection Units to Sources Mapping Files
7412 @item -gnatem=@var{path}
7413 @cindex @option{-gnatem} (@command{gcc})
7414 A mapping file is a way to communicate to the compiler two mappings:
7415 from unit names to file names (without any directory information) and from
7416 file names to path names (with full directory information). These mappings
7417 are used by the compiler to short-circuit the path search.
7419 The use of mapping files is not required for correct operation of the
7420 compiler, but mapping files can improve efficiency, particularly when
7421 sources are read over a slow network connection. In normal operation,
7422 you need not be concerned with the format or use of mapping files,
7423 and the @option{-gnatem} switch is not a switch that you would use
7424 explicitly. It is intended primarily for use by automatic tools such as
7425 @command{gnatmake} running under the project file facility. The
7426 description here of the format of mapping files is provided
7427 for completeness and for possible use by other tools.
7429 A mapping file is a sequence of sets of three lines. In each set, the
7430 first line is the unit name, in lower case, with @code{%s} appended
7431 for specs and @code{%b} appended for bodies; the second line is the
7432 file name; and the third line is the path name.
7438 /gnat/project1/sources/main.2.ada
7441 When the switch @option{-gnatem} is specified, the compiler will
7442 create in memory the two mappings from the specified file. If there is
7443 any problem (nonexistent file, truncated file or duplicate entries),
7444 no mapping will be created.
7446 Several @option{-gnatem} switches may be specified; however, only the
7447 last one on the command line will be taken into account.
7449 When using a project file, @command{gnatmake} creates a temporary
7450 mapping file and communicates it to the compiler using this switch.
7454 @node Integrated Preprocessing
7455 @subsection Integrated Preprocessing
7458 GNAT sources may be preprocessed immediately before compilation.
7459 In this case, the actual
7460 text of the source is not the text of the source file, but is derived from it
7461 through a process called preprocessing. Integrated preprocessing is specified
7462 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7463 indicates, through a text file, the preprocessing data to be used.
7464 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7467 Note that when integrated preprocessing is used, the output from the
7468 preprocessor is not written to any external file. Instead it is passed
7469 internally to the compiler. If you need to preserve the result of
7470 preprocessing in a file, then you should use @command{gnatprep}
7471 to perform the desired preprocessing in stand-alone mode.
7474 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7475 used when Integrated Preprocessing is used. The reason is that preprocessing
7476 with another Preprocessing Data file without changing the sources will
7477 not trigger recompilation without this switch.
7480 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7481 always trigger recompilation for sources that are preprocessed,
7482 because @command{gnatmake} cannot compute the checksum of the source after
7486 The actual preprocessing function is described in details in section
7487 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7488 preprocessing is triggered and parameterized.
7492 @item -gnatep=@var{file}
7493 @cindex @option{-gnatep} (@command{gcc})
7494 This switch indicates to the compiler the file name (without directory
7495 information) of the preprocessor data file to use. The preprocessor data file
7496 should be found in the source directories.
7499 A preprocessing data file is a text file with significant lines indicating
7500 how should be preprocessed either a specific source or all sources not
7501 mentioned in other lines. A significant line is a nonempty, non-comment line.
7502 Comments are similar to Ada comments.
7505 Each significant line starts with either a literal string or the character '*'.
7506 A literal string is the file name (without directory information) of the source
7507 to preprocess. A character '*' indicates the preprocessing for all the sources
7508 that are not specified explicitly on other lines (order of the lines is not
7509 significant). It is an error to have two lines with the same file name or two
7510 lines starting with the character '*'.
7513 After the file name or the character '*', another optional literal string
7514 indicating the file name of the definition file to be used for preprocessing
7515 (@pxref{Form of Definitions File}). The definition files are found by the
7516 compiler in one of the source directories. In some cases, when compiling
7517 a source in a directory other than the current directory, if the definition
7518 file is in the current directory, it may be necessary to add the current
7519 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7520 the compiler would not find the definition file.
7523 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7524 be found. Those ^switches^switches^ are:
7529 Causes both preprocessor lines and the lines deleted by
7530 preprocessing to be replaced by blank lines, preserving the line number.
7531 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7532 it cancels the effect of @option{-c}.
7535 Causes both preprocessor lines and the lines deleted
7536 by preprocessing to be retained as comments marked
7537 with the special string ``@code{--! }''.
7539 @item -Dsymbol=value
7540 Define or redefine a symbol, associated with value. A symbol is an Ada
7541 identifier, or an Ada reserved word, with the exception of @code{if},
7542 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7543 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7544 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7545 same name defined in a definition file.
7548 Causes a sorted list of symbol names and values to be
7549 listed on the standard output file.
7552 Causes undefined symbols to be treated as having the value @code{FALSE}
7554 of a preprocessor test. In the absence of this option, an undefined symbol in
7555 a @code{#if} or @code{#elsif} test will be treated as an error.
7560 Examples of valid lines in a preprocessor data file:
7563 "toto.adb" "prep.def" -u
7564 -- preprocess "toto.adb", using definition file "prep.def",
7565 -- undefined symbol are False.
7568 -- preprocess all other sources without a definition file;
7569 -- suppressed lined are commented; symbol VERSION has the value V101.
7571 "titi.adb" "prep2.def" -s
7572 -- preprocess "titi.adb", using definition file "prep2.def";
7573 -- list all symbols with their values.
7576 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7577 @cindex @option{-gnateD} (@command{gcc})
7578 Define or redefine a preprocessing symbol, associated with value. If no value
7579 is given on the command line, then the value of the symbol is @code{True}.
7580 A symbol is an identifier, following normal Ada (case-insensitive)
7581 rules for its syntax, and value is any sequence (including an empty sequence)
7582 of characters from the set (letters, digits, period, underline).
7583 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7584 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7587 A symbol declared with this ^switch^switch^ on the command line replaces a
7588 symbol with the same name either in a definition file or specified with a
7589 ^switch^switch^ -D in the preprocessor data file.
7592 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7595 When integrated preprocessing is performed and the preprocessor modifies
7596 the source text, write the result of this preprocessing into a file
7597 <source>^.prep^_prep^.
7601 @node Code Generation Control
7602 @subsection Code Generation Control
7606 The GCC technology provides a wide range of target dependent
7607 @option{-m} switches for controlling
7608 details of code generation with respect to different versions of
7609 architectures. This includes variations in instruction sets (e.g.@:
7610 different members of the power pc family), and different requirements
7611 for optimal arrangement of instructions (e.g.@: different members of
7612 the x86 family). The list of available @option{-m} switches may be
7613 found in the GCC documentation.
7615 Use of these @option{-m} switches may in some cases result in improved
7618 The GNAT Pro technology is tested and qualified without any
7619 @option{-m} switches,
7620 so generally the most reliable approach is to avoid the use of these
7621 switches. However, we generally expect most of these switches to work
7622 successfully with GNAT Pro, and many customers have reported successful
7623 use of these options.
7625 Our general advice is to avoid the use of @option{-m} switches unless
7626 special needs lead to requirements in this area. In particular,
7627 there is no point in using @option{-m} switches to improve performance
7628 unless you actually see a performance improvement.
7632 @subsection Return Codes
7633 @cindex Return Codes
7634 @cindex @option{/RETURN_CODES=VMS}
7637 On VMS, GNAT compiled programs return POSIX-style codes by default,
7638 e.g.@: @option{/RETURN_CODES=POSIX}.
7640 To enable VMS style return codes, use GNAT BIND and LINK with the option
7641 @option{/RETURN_CODES=VMS}. For example:
7644 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7645 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7649 Programs built with /RETURN_CODES=VMS are suitable to be called in
7650 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7651 are suitable for spawning with appropriate GNAT RTL routines.
7655 @node Search Paths and the Run-Time Library (RTL)
7656 @section Search Paths and the Run-Time Library (RTL)
7659 With the GNAT source-based library system, the compiler must be able to
7660 find source files for units that are needed by the unit being compiled.
7661 Search paths are used to guide this process.
7663 The compiler compiles one source file whose name must be given
7664 explicitly on the command line. In other words, no searching is done
7665 for this file. To find all other source files that are needed (the most
7666 common being the specs of units), the compiler examines the following
7667 directories, in the following order:
7671 The directory containing the source file of the main unit being compiled
7672 (the file name on the command line).
7675 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7676 @command{gcc} command line, in the order given.
7679 @findex ADA_PRJ_INCLUDE_FILE
7680 Each of the directories listed in the text file whose name is given
7681 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7684 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7685 driver when project files are used. It should not normally be set
7689 @findex ADA_INCLUDE_PATH
7690 Each of the directories listed in the value of the
7691 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7693 Construct this value
7694 exactly as the @env{PATH} environment variable: a list of directory
7695 names separated by colons (semicolons when working with the NT version).
7698 Normally, define this value as a logical name containing a comma separated
7699 list of directory names.
7701 This variable can also be defined by means of an environment string
7702 (an argument to the HP C exec* set of functions).
7706 DEFINE ANOTHER_PATH FOO:[BAG]
7707 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7710 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7711 first, followed by the standard Ada
7712 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7713 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7714 (Text_IO, Sequential_IO, etc)
7715 instead of the standard Ada packages. Thus, in order to get the standard Ada
7716 packages by default, ADA_INCLUDE_PATH must be redefined.
7720 The content of the @file{ada_source_path} file which is part of the GNAT
7721 installation tree and is used to store standard libraries such as the
7722 GNAT Run Time Library (RTL) source files.
7724 @ref{Installing a library}
7729 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7730 inhibits the use of the directory
7731 containing the source file named in the command line. You can still
7732 have this directory on your search path, but in this case it must be
7733 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7735 Specifying the switch @option{-nostdinc}
7736 inhibits the search of the default location for the GNAT Run Time
7737 Library (RTL) source files.
7739 The compiler outputs its object files and ALI files in the current
7742 Caution: The object file can be redirected with the @option{-o} switch;
7743 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7744 so the @file{ALI} file will not go to the right place. Therefore, you should
7745 avoid using the @option{-o} switch.
7749 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7750 children make up the GNAT RTL, together with the simple @code{System.IO}
7751 package used in the @code{"Hello World"} example. The sources for these units
7752 are needed by the compiler and are kept together in one directory. Not
7753 all of the bodies are needed, but all of the sources are kept together
7754 anyway. In a normal installation, you need not specify these directory
7755 names when compiling or binding. Either the environment variables or
7756 the built-in defaults cause these files to be found.
7758 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7759 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7760 consisting of child units of @code{GNAT}. This is a collection of generally
7761 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7762 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7764 Besides simplifying access to the RTL, a major use of search paths is
7765 in compiling sources from multiple directories. This can make
7766 development environments much more flexible.
7768 @node Order of Compilation Issues
7769 @section Order of Compilation Issues
7772 If, in our earlier example, there was a spec for the @code{hello}
7773 procedure, it would be contained in the file @file{hello.ads}; yet this
7774 file would not have to be explicitly compiled. This is the result of the
7775 model we chose to implement library management. Some of the consequences
7776 of this model are as follows:
7780 There is no point in compiling specs (except for package
7781 specs with no bodies) because these are compiled as needed by clients. If
7782 you attempt a useless compilation, you will receive an error message.
7783 It is also useless to compile subunits because they are compiled as needed
7787 There are no order of compilation requirements: performing a
7788 compilation never obsoletes anything. The only way you can obsolete
7789 something and require recompilations is to modify one of the
7790 source files on which it depends.
7793 There is no library as such, apart from the ALI files
7794 (@pxref{The Ada Library Information Files}, for information on the format
7795 of these files). For now we find it convenient to create separate ALI files,
7796 but eventually the information therein may be incorporated into the object
7800 When you compile a unit, the source files for the specs of all units
7801 that it @code{with}'s, all its subunits, and the bodies of any generics it
7802 instantiates must be available (reachable by the search-paths mechanism
7803 described above), or you will receive a fatal error message.
7810 The following are some typical Ada compilation command line examples:
7813 @item $ gcc -c xyz.adb
7814 Compile body in file @file{xyz.adb} with all default options.
7817 @item $ gcc -c -O2 -gnata xyz-def.adb
7820 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7823 Compile the child unit package in file @file{xyz-def.adb} with extensive
7824 optimizations, and pragma @code{Assert}/@code{Debug} statements
7827 @item $ gcc -c -gnatc abc-def.adb
7828 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7832 @node Binding Using gnatbind
7833 @chapter Binding Using @code{gnatbind}
7837 * Running gnatbind::
7838 * Switches for gnatbind::
7839 * Command-Line Access::
7840 * Search Paths for gnatbind::
7841 * Examples of gnatbind Usage::
7845 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7846 to bind compiled GNAT objects.
7848 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7849 driver (see @ref{The GNAT Driver and Project Files}).
7851 The @code{gnatbind} program performs four separate functions:
7855 Checks that a program is consistent, in accordance with the rules in
7856 Chapter 10 of the Ada Reference Manual. In particular, error
7857 messages are generated if a program uses inconsistent versions of a
7861 Checks that an acceptable order of elaboration exists for the program
7862 and issues an error message if it cannot find an order of elaboration
7863 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7866 Generates a main program incorporating the given elaboration order.
7867 This program is a small Ada package (body and spec) that
7868 must be subsequently compiled
7869 using the GNAT compiler. The necessary compilation step is usually
7870 performed automatically by @command{gnatlink}. The two most important
7871 functions of this program
7872 are to call the elaboration routines of units in an appropriate order
7873 and to call the main program.
7876 Determines the set of object files required by the given main program.
7877 This information is output in the forms of comments in the generated program,
7878 to be read by the @command{gnatlink} utility used to link the Ada application.
7881 @node Running gnatbind
7882 @section Running @code{gnatbind}
7885 The form of the @code{gnatbind} command is
7888 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7892 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7893 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7894 package in two files whose names are
7895 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7896 For example, if given the
7897 parameter @file{hello.ali}, for a main program contained in file
7898 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7899 and @file{b~hello.adb}.
7901 When doing consistency checking, the binder takes into consideration
7902 any source files it can locate. For example, if the binder determines
7903 that the given main program requires the package @code{Pack}, whose
7905 file is @file{pack.ali} and whose corresponding source spec file is
7906 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7907 (using the same search path conventions as previously described for the
7908 @command{gcc} command). If it can locate this source file, it checks that
7910 or source checksums of the source and its references to in @file{ALI} files
7911 match. In other words, any @file{ALI} files that mentions this spec must have
7912 resulted from compiling this version of the source file (or in the case
7913 where the source checksums match, a version close enough that the
7914 difference does not matter).
7916 @cindex Source files, use by binder
7917 The effect of this consistency checking, which includes source files, is
7918 that the binder ensures that the program is consistent with the latest
7919 version of the source files that can be located at bind time. Editing a
7920 source file without compiling files that depend on the source file cause
7921 error messages to be generated by the binder.
7923 For example, suppose you have a main program @file{hello.adb} and a
7924 package @code{P}, from file @file{p.ads} and you perform the following
7929 Enter @code{gcc -c hello.adb} to compile the main program.
7932 Enter @code{gcc -c p.ads} to compile package @code{P}.
7935 Edit file @file{p.ads}.
7938 Enter @code{gnatbind hello}.
7942 At this point, the file @file{p.ali} contains an out-of-date time stamp
7943 because the file @file{p.ads} has been edited. The attempt at binding
7944 fails, and the binder generates the following error messages:
7947 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7948 error: "p.ads" has been modified and must be recompiled
7952 Now both files must be recompiled as indicated, and then the bind can
7953 succeed, generating a main program. You need not normally be concerned
7954 with the contents of this file, but for reference purposes a sample
7955 binder output file is given in @ref{Example of Binder Output File}.
7957 In most normal usage, the default mode of @command{gnatbind} which is to
7958 generate the main package in Ada, as described in the previous section.
7959 In particular, this means that any Ada programmer can read and understand
7960 the generated main program. It can also be debugged just like any other
7961 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7962 @command{gnatbind} and @command{gnatlink}.
7964 However for some purposes it may be convenient to generate the main
7965 program in C rather than Ada. This may for example be helpful when you
7966 are generating a mixed language program with the main program in C. The
7967 GNAT compiler itself is an example.
7968 The use of the @option{^-C^/BIND_FILE=C^} switch
7969 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7970 be generated in C (and compiled using the gnu C compiler).
7972 @node Switches for gnatbind
7973 @section Switches for @command{gnatbind}
7976 The following switches are available with @code{gnatbind}; details will
7977 be presented in subsequent sections.
7980 * Consistency-Checking Modes::
7981 * Binder Error Message Control::
7982 * Elaboration Control::
7984 * Binding with Non-Ada Main Programs::
7985 * Binding Programs with No Main Subprogram::
7992 @cindex @option{--version} @command{gnatbind}
7993 Display Copyright and version, then exit disregarding all other options.
7996 @cindex @option{--help} @command{gnatbind}
7997 If @option{--version} was not used, display usage, then exit disregarding
8001 @cindex @option{-a} @command{gnatbind}
8002 Indicates that, if supported by the platform, the adainit procedure should
8003 be treated as an initialisation routine by the linker (a constructor). This
8004 is intended to be used by the Project Manager to automatically initialize
8005 shared Stand-Alone Libraries.
8007 @item ^-aO^/OBJECT_SEARCH^
8008 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
8009 Specify directory to be searched for ALI files.
8011 @item ^-aI^/SOURCE_SEARCH^
8012 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8013 Specify directory to be searched for source file.
8015 @item ^-A^/BIND_FILE=ADA^
8016 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
8017 Generate binder program in Ada (default)
8019 @item ^-b^/REPORT_ERRORS=BRIEF^
8020 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
8021 Generate brief messages to @file{stderr} even if verbose mode set.
8023 @item ^-c^/NOOUTPUT^
8024 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
8025 Check only, no generation of binder output file.
8027 @item ^-C^/BIND_FILE=C^
8028 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
8029 Generate binder program in C
8031 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8032 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8033 This switch can be used to change the default task stack size value
8034 to a specified size @var{nn}, which is expressed in bytes by default, or
8035 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8037 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8038 in effect, to completing all task specs with
8039 @smallexample @c ada
8040 pragma Storage_Size (nn);
8042 When they do not already have such a pragma.
8044 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8045 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8046 This switch can be used to change the default secondary stack size value
8047 to a specified size @var{nn}, which is expressed in bytes by default, or
8048 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8051 The secondary stack is used to deal with functions that return a variable
8052 sized result, for example a function returning an unconstrained
8053 String. There are two ways in which this secondary stack is allocated.
8055 For most targets, the secondary stack is growing on demand and is allocated
8056 as a chain of blocks in the heap. The -D option is not very
8057 relevant. It only give some control over the size of the allocated
8058 blocks (whose size is the minimum of the default secondary stack size value,
8059 and the actual size needed for the current allocation request).
8061 For certain targets, notably VxWorks 653,
8062 the secondary stack is allocated by carving off a fixed ratio chunk of the
8063 primary task stack. The -D option is used to define the
8064 size of the environment task's secondary stack.
8066 @item ^-e^/ELABORATION_DEPENDENCIES^
8067 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8068 Output complete list of elaboration-order dependencies.
8070 @item ^-E^/STORE_TRACEBACKS^
8071 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8072 Store tracebacks in exception occurrences when the target supports it.
8073 This is the default with the zero cost exception mechanism.
8075 @c The following may get moved to an appendix
8076 This option is currently supported on the following targets:
8077 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8079 See also the packages @code{GNAT.Traceback} and
8080 @code{GNAT.Traceback.Symbolic} for more information.
8082 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8083 @command{gcc} option.
8086 @item ^-F^/FORCE_ELABS_FLAGS^
8087 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8088 Force the checks of elaboration flags. @command{gnatbind} does not normally
8089 generate checks of elaboration flags for the main executable, except when
8090 a Stand-Alone Library is used. However, there are cases when this cannot be
8091 detected by gnatbind. An example is importing an interface of a Stand-Alone
8092 Library through a pragma Import and only specifying through a linker switch
8093 this Stand-Alone Library. This switch is used to guarantee that elaboration
8094 flag checks are generated.
8097 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8098 Output usage (help) information
8101 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8102 Specify directory to be searched for source and ALI files.
8104 @item ^-I-^/NOCURRENT_DIRECTORY^
8105 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8106 Do not look for sources in the current directory where @code{gnatbind} was
8107 invoked, and do not look for ALI files in the directory containing the
8108 ALI file named in the @code{gnatbind} command line.
8110 @item ^-l^/ORDER_OF_ELABORATION^
8111 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8112 Output chosen elaboration order.
8114 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8115 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8116 Bind the units for library building. In this case the adainit and
8117 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8118 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8119 ^@var{xxx}final^@var{XXX}FINAL^.
8120 Implies ^-n^/NOCOMPILE^.
8122 (@xref{GNAT and Libraries}, for more details.)
8125 On OpenVMS, these init and final procedures are exported in uppercase
8126 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8127 the init procedure will be "TOTOINIT" and the exported name of the final
8128 procedure will be "TOTOFINAL".
8131 @item ^-Mxyz^/RENAME_MAIN=xyz^
8132 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8133 Rename generated main program from main to xyz. This option is
8134 supported on cross environments only.
8136 @item ^-m^/ERROR_LIMIT=^@var{n}
8137 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8138 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8139 in the range 1..999999. The default value if no switch is
8140 given is 9999. If the number of warnings reaches this limit, then a
8141 message is output and further warnings are suppressed, the bind
8142 continues in this case. If the number of errors reaches this
8143 limit, then a message is output and the bind is abandoned.
8144 A value of zero means that no limit is enforced. The equal
8148 Furthermore, under Windows, the sources pointed to by the libraries path
8149 set in the registry are not searched for.
8153 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8157 @cindex @option{-nostdinc} (@command{gnatbind})
8158 Do not look for sources in the system default directory.
8161 @cindex @option{-nostdlib} (@command{gnatbind})
8162 Do not look for library files in the system default directory.
8164 @item --RTS=@var{rts-path}
8165 @cindex @option{--RTS} (@code{gnatbind})
8166 Specifies the default location of the runtime library. Same meaning as the
8167 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8169 @item ^-o ^/OUTPUT=^@var{file}
8170 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8171 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8172 Note that if this option is used, then linking must be done manually,
8173 gnatlink cannot be used.
8175 @item ^-O^/OBJECT_LIST^
8176 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8179 @item ^-p^/PESSIMISTIC_ELABORATION^
8180 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8181 Pessimistic (worst-case) elaboration order
8184 @cindex @option{^-R^-R^} (@command{gnatbind})
8185 Output closure source list.
8187 @item ^-s^/READ_SOURCES=ALL^
8188 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8189 Require all source files to be present.
8191 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8192 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8193 Specifies the value to be used when detecting uninitialized scalar
8194 objects with pragma Initialize_Scalars.
8195 The @var{xxx} ^string specified with the switch^option^ may be either
8197 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8198 @item ``@option{^lo^LOW^}'' for the lowest possible value
8199 @item ``@option{^hi^HIGH^}'' for the highest possible value
8200 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8201 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8204 In addition, you can specify @option{-Sev} to indicate that the value is
8205 to be set at run time. In this case, the program will look for an environment
8206 @cindex GNAT_INIT_SCALARS
8207 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8208 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8209 If no environment variable is found, or if it does not have a valid value,
8210 then the default is @option{in} (invalid values).
8214 @cindex @option{-static} (@code{gnatbind})
8215 Link against a static GNAT run time.
8218 @cindex @option{-shared} (@code{gnatbind})
8219 Link against a shared GNAT run time when available.
8222 @item ^-t^/NOTIME_STAMP_CHECK^
8223 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8224 Tolerate time stamp and other consistency errors
8226 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8227 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8228 Set the time slice value to @var{n} milliseconds. If the system supports
8229 the specification of a specific time slice value, then the indicated value
8230 is used. If the system does not support specific time slice values, but
8231 does support some general notion of round-robin scheduling, then any
8232 nonzero value will activate round-robin scheduling.
8234 A value of zero is treated specially. It turns off time
8235 slicing, and in addition, indicates to the tasking run time that the
8236 semantics should match as closely as possible the Annex D
8237 requirements of the Ada RM, and in particular sets the default
8238 scheduling policy to @code{FIFO_Within_Priorities}.
8240 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8241 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8242 Enable dynamic stack usage, with @var{n} results stored and displayed
8243 at program termination. A result is generated when a task
8244 terminates. Results that can't be stored are displayed on the fly, at
8245 task termination. This option is currently not supported on Itanium
8246 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8248 @item ^-v^/REPORT_ERRORS=VERBOSE^
8249 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8250 Verbose mode. Write error messages, header, summary output to
8255 @cindex @option{-w} (@code{gnatbind})
8256 Warning mode (@var{x}=s/e for suppress/treat as error)
8260 @item /WARNINGS=NORMAL
8261 @cindex @option{/WARNINGS} (@code{gnatbind})
8262 Normal warnings mode. Warnings are issued but ignored
8264 @item /WARNINGS=SUPPRESS
8265 @cindex @option{/WARNINGS} (@code{gnatbind})
8266 All warning messages are suppressed
8268 @item /WARNINGS=ERROR
8269 @cindex @option{/WARNINGS} (@code{gnatbind})
8270 Warning messages are treated as fatal errors
8273 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8274 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8275 Override default wide character encoding for standard Text_IO files.
8277 @item ^-x^/READ_SOURCES=NONE^
8278 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8279 Exclude source files (check object consistency only).
8282 @item /READ_SOURCES=AVAILABLE
8283 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8284 Default mode, in which sources are checked for consistency only if
8288 @item ^-y^/ENABLE_LEAP_SECONDS^
8289 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8290 Enable leap seconds support in @code{Ada.Calendar} and its children.
8292 @item ^-z^/ZERO_MAIN^
8293 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8299 You may obtain this listing of switches by running @code{gnatbind} with
8303 @node Consistency-Checking Modes
8304 @subsection Consistency-Checking Modes
8307 As described earlier, by default @code{gnatbind} checks
8308 that object files are consistent with one another and are consistent
8309 with any source files it can locate. The following switches control binder
8314 @item ^-s^/READ_SOURCES=ALL^
8315 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8316 Require source files to be present. In this mode, the binder must be
8317 able to locate all source files that are referenced, in order to check
8318 their consistency. In normal mode, if a source file cannot be located it
8319 is simply ignored. If you specify this switch, a missing source
8322 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8323 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8324 Override default wide character encoding for standard Text_IO files.
8325 Normally the default wide character encoding method used for standard
8326 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8327 the main source input (see description of switch
8328 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8329 use of this switch for the binder (which has the same set of
8330 possible arguments) overrides this default as specified.
8332 @item ^-x^/READ_SOURCES=NONE^
8333 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8334 Exclude source files. In this mode, the binder only checks that ALI
8335 files are consistent with one another. Source files are not accessed.
8336 The binder runs faster in this mode, and there is still a guarantee that
8337 the resulting program is self-consistent.
8338 If a source file has been edited since it was last compiled, and you
8339 specify this switch, the binder will not detect that the object
8340 file is out of date with respect to the source file. Note that this is the
8341 mode that is automatically used by @command{gnatmake} because in this
8342 case the checking against sources has already been performed by
8343 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8346 @item /READ_SOURCES=AVAILABLE
8347 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8348 This is the default mode in which source files are checked if they are
8349 available, and ignored if they are not available.
8353 @node Binder Error Message Control
8354 @subsection Binder Error Message Control
8357 The following switches provide control over the generation of error
8358 messages from the binder:
8362 @item ^-v^/REPORT_ERRORS=VERBOSE^
8363 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8364 Verbose mode. In the normal mode, brief error messages are generated to
8365 @file{stderr}. If this switch is present, a header is written
8366 to @file{stdout} and any error messages are directed to @file{stdout}.
8367 All that is written to @file{stderr} is a brief summary message.
8369 @item ^-b^/REPORT_ERRORS=BRIEF^
8370 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8371 Generate brief error messages to @file{stderr} even if verbose mode is
8372 specified. This is relevant only when used with the
8373 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8377 @cindex @option{-m} (@code{gnatbind})
8378 Limits the number of error messages to @var{n}, a decimal integer in the
8379 range 1-999. The binder terminates immediately if this limit is reached.
8382 @cindex @option{-M} (@code{gnatbind})
8383 Renames the generated main program from @code{main} to @code{xxx}.
8384 This is useful in the case of some cross-building environments, where
8385 the actual main program is separate from the one generated
8389 @item ^-ws^/WARNINGS=SUPPRESS^
8390 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8392 Suppress all warning messages.
8394 @item ^-we^/WARNINGS=ERROR^
8395 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8396 Treat any warning messages as fatal errors.
8399 @item /WARNINGS=NORMAL
8400 Standard mode with warnings generated, but warnings do not get treated
8404 @item ^-t^/NOTIME_STAMP_CHECK^
8405 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8406 @cindex Time stamp checks, in binder
8407 @cindex Binder consistency checks
8408 @cindex Consistency checks, in binder
8409 The binder performs a number of consistency checks including:
8413 Check that time stamps of a given source unit are consistent
8415 Check that checksums of a given source unit are consistent
8417 Check that consistent versions of @code{GNAT} were used for compilation
8419 Check consistency of configuration pragmas as required
8423 Normally failure of such checks, in accordance with the consistency
8424 requirements of the Ada Reference Manual, causes error messages to be
8425 generated which abort the binder and prevent the output of a binder
8426 file and subsequent link to obtain an executable.
8428 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8429 into warnings, so that
8430 binding and linking can continue to completion even in the presence of such
8431 errors. The result may be a failed link (due to missing symbols), or a
8432 non-functional executable which has undefined semantics.
8433 @emph{This means that
8434 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8438 @node Elaboration Control
8439 @subsection Elaboration Control
8442 The following switches provide additional control over the elaboration
8443 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8446 @item ^-p^/PESSIMISTIC_ELABORATION^
8447 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8448 Normally the binder attempts to choose an elaboration order that is
8449 likely to minimize the likelihood of an elaboration order error resulting
8450 in raising a @code{Program_Error} exception. This switch reverses the
8451 action of the binder, and requests that it deliberately choose an order
8452 that is likely to maximize the likelihood of an elaboration error.
8453 This is useful in ensuring portability and avoiding dependence on
8454 accidental fortuitous elaboration ordering.
8456 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8458 elaboration checking is used (@option{-gnatE} switch used for compilation).
8459 This is because in the default static elaboration mode, all necessary
8460 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8461 These implicit pragmas are still respected by the binder in
8462 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8463 safe elaboration order is assured.
8466 @node Output Control
8467 @subsection Output Control
8470 The following switches allow additional control over the output
8471 generated by the binder.
8476 @item ^-A^/BIND_FILE=ADA^
8477 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8478 Generate binder program in Ada (default). The binder program is named
8479 @file{b~@var{mainprog}.adb} by default. This can be changed with
8480 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8482 @item ^-c^/NOOUTPUT^
8483 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8484 Check only. Do not generate the binder output file. In this mode the
8485 binder performs all error checks but does not generate an output file.
8487 @item ^-C^/BIND_FILE=C^
8488 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8489 Generate binder program in C. The binder program is named
8490 @file{b_@var{mainprog}.c}.
8491 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8494 @item ^-e^/ELABORATION_DEPENDENCIES^
8495 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8496 Output complete list of elaboration-order dependencies, showing the
8497 reason for each dependency. This output can be rather extensive but may
8498 be useful in diagnosing problems with elaboration order. The output is
8499 written to @file{stdout}.
8502 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8503 Output usage information. The output is written to @file{stdout}.
8505 @item ^-K^/LINKER_OPTION_LIST^
8506 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8507 Output linker options to @file{stdout}. Includes library search paths,
8508 contents of pragmas Ident and Linker_Options, and libraries added
8511 @item ^-l^/ORDER_OF_ELABORATION^
8512 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8513 Output chosen elaboration order. The output is written to @file{stdout}.
8515 @item ^-O^/OBJECT_LIST^
8516 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8517 Output full names of all the object files that must be linked to provide
8518 the Ada component of the program. The output is written to @file{stdout}.
8519 This list includes the files explicitly supplied and referenced by the user
8520 as well as implicitly referenced run-time unit files. The latter are
8521 omitted if the corresponding units reside in shared libraries. The
8522 directory names for the run-time units depend on the system configuration.
8524 @item ^-o ^/OUTPUT=^@var{file}
8525 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8526 Set name of output file to @var{file} instead of the normal
8527 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8528 binder generated body filename. In C mode you would normally give
8529 @var{file} an extension of @file{.c} because it will be a C source program.
8530 Note that if this option is used, then linking must be done manually.
8531 It is not possible to use gnatlink in this case, since it cannot locate
8534 @item ^-r^/RESTRICTION_LIST^
8535 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8536 Generate list of @code{pragma Restrictions} that could be applied to
8537 the current unit. This is useful for code audit purposes, and also may
8538 be used to improve code generation in some cases.
8542 @node Binding with Non-Ada Main Programs
8543 @subsection Binding with Non-Ada Main Programs
8546 In our description so far we have assumed that the main
8547 program is in Ada, and that the task of the binder is to generate a
8548 corresponding function @code{main} that invokes this Ada main
8549 program. GNAT also supports the building of executable programs where
8550 the main program is not in Ada, but some of the called routines are
8551 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8552 The following switch is used in this situation:
8556 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8557 No main program. The main program is not in Ada.
8561 In this case, most of the functions of the binder are still required,
8562 but instead of generating a main program, the binder generates a file
8563 containing the following callable routines:
8568 You must call this routine to initialize the Ada part of the program by
8569 calling the necessary elaboration routines. A call to @code{adainit} is
8570 required before the first call to an Ada subprogram.
8572 Note that it is assumed that the basic execution environment must be setup
8573 to be appropriate for Ada execution at the point where the first Ada
8574 subprogram is called. In particular, if the Ada code will do any
8575 floating-point operations, then the FPU must be setup in an appropriate
8576 manner. For the case of the x86, for example, full precision mode is
8577 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8578 that the FPU is in the right state.
8582 You must call this routine to perform any library-level finalization
8583 required by the Ada subprograms. A call to @code{adafinal} is required
8584 after the last call to an Ada subprogram, and before the program
8589 If the @option{^-n^/NOMAIN^} switch
8590 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8591 @cindex Binder, multiple input files
8592 is given, more than one ALI file may appear on
8593 the command line for @code{gnatbind}. The normal @dfn{closure}
8594 calculation is performed for each of the specified units. Calculating
8595 the closure means finding out the set of units involved by tracing
8596 @code{with} references. The reason it is necessary to be able to
8597 specify more than one ALI file is that a given program may invoke two or
8598 more quite separate groups of Ada units.
8600 The binder takes the name of its output file from the last specified ALI
8601 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8602 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8603 The output is an Ada unit in source form that can
8604 be compiled with GNAT unless the -C switch is used in which case the
8605 output is a C source file, which must be compiled using the C compiler.
8606 This compilation occurs automatically as part of the @command{gnatlink}
8609 Currently the GNAT run time requires a FPU using 80 bits mode
8610 precision. Under targets where this is not the default it is required to
8611 call GNAT.Float_Control.Reset before using floating point numbers (this
8612 include float computation, float input and output) in the Ada code. A
8613 side effect is that this could be the wrong mode for the foreign code
8614 where floating point computation could be broken after this call.
8616 @node Binding Programs with No Main Subprogram
8617 @subsection Binding Programs with No Main Subprogram
8620 It is possible to have an Ada program which does not have a main
8621 subprogram. This program will call the elaboration routines of all the
8622 packages, then the finalization routines.
8624 The following switch is used to bind programs organized in this manner:
8627 @item ^-z^/ZERO_MAIN^
8628 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8629 Normally the binder checks that the unit name given on the command line
8630 corresponds to a suitable main subprogram. When this switch is used,
8631 a list of ALI files can be given, and the execution of the program
8632 consists of elaboration of these units in an appropriate order. Note
8633 that the default wide character encoding method for standard Text_IO
8634 files is always set to Brackets if this switch is set (you can use
8636 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8639 @node Command-Line Access
8640 @section Command-Line Access
8643 The package @code{Ada.Command_Line} provides access to the command-line
8644 arguments and program name. In order for this interface to operate
8645 correctly, the two variables
8657 are declared in one of the GNAT library routines. These variables must
8658 be set from the actual @code{argc} and @code{argv} values passed to the
8659 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8660 generates the C main program to automatically set these variables.
8661 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8662 set these variables. If they are not set, the procedures in
8663 @code{Ada.Command_Line} will not be available, and any attempt to use
8664 them will raise @code{Constraint_Error}. If command line access is
8665 required, your main program must set @code{gnat_argc} and
8666 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8669 @node Search Paths for gnatbind
8670 @section Search Paths for @code{gnatbind}
8673 The binder takes the name of an ALI file as its argument and needs to
8674 locate source files as well as other ALI files to verify object consistency.
8676 For source files, it follows exactly the same search rules as @command{gcc}
8677 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8678 directories searched are:
8682 The directory containing the ALI file named in the command line, unless
8683 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8686 All directories specified by @option{^-I^/SEARCH^}
8687 switches on the @code{gnatbind}
8688 command line, in the order given.
8691 @findex ADA_PRJ_OBJECTS_FILE
8692 Each of the directories listed in the text file whose name is given
8693 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8696 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8697 driver when project files are used. It should not normally be set
8701 @findex ADA_OBJECTS_PATH
8702 Each of the directories listed in the value of the
8703 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8705 Construct this value
8706 exactly as the @env{PATH} environment variable: a list of directory
8707 names separated by colons (semicolons when working with the NT version
8711 Normally, define this value as a logical name containing a comma separated
8712 list of directory names.
8714 This variable can also be defined by means of an environment string
8715 (an argument to the HP C exec* set of functions).
8719 DEFINE ANOTHER_PATH FOO:[BAG]
8720 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8723 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8724 first, followed by the standard Ada
8725 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8726 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8727 (Text_IO, Sequential_IO, etc)
8728 instead of the standard Ada packages. Thus, in order to get the standard Ada
8729 packages by default, ADA_OBJECTS_PATH must be redefined.
8733 The content of the @file{ada_object_path} file which is part of the GNAT
8734 installation tree and is used to store standard libraries such as the
8735 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8738 @ref{Installing a library}
8743 In the binder the switch @option{^-I^/SEARCH^}
8744 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8745 is used to specify both source and
8746 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8747 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8748 instead if you want to specify
8749 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8750 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8751 if you want to specify library paths
8752 only. This means that for the binder
8753 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8754 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8755 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8756 The binder generates the bind file (a C language source file) in the
8757 current working directory.
8763 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8764 children make up the GNAT Run-Time Library, together with the package
8765 GNAT and its children, which contain a set of useful additional
8766 library functions provided by GNAT. The sources for these units are
8767 needed by the compiler and are kept together in one directory. The ALI
8768 files and object files generated by compiling the RTL are needed by the
8769 binder and the linker and are kept together in one directory, typically
8770 different from the directory containing the sources. In a normal
8771 installation, you need not specify these directory names when compiling
8772 or binding. Either the environment variables or the built-in defaults
8773 cause these files to be found.
8775 Besides simplifying access to the RTL, a major use of search paths is
8776 in compiling sources from multiple directories. This can make
8777 development environments much more flexible.
8779 @node Examples of gnatbind Usage
8780 @section Examples of @code{gnatbind} Usage
8783 This section contains a number of examples of using the GNAT binding
8784 utility @code{gnatbind}.
8787 @item gnatbind hello
8788 The main program @code{Hello} (source program in @file{hello.adb}) is
8789 bound using the standard switch settings. The generated main program is
8790 @file{b~hello.adb}. This is the normal, default use of the binder.
8793 @item gnatbind hello -o mainprog.adb
8796 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8798 The main program @code{Hello} (source program in @file{hello.adb}) is
8799 bound using the standard switch settings. The generated main program is
8800 @file{mainprog.adb} with the associated spec in
8801 @file{mainprog.ads}. Note that you must specify the body here not the
8802 spec, in the case where the output is in Ada. Note that if this option
8803 is used, then linking must be done manually, since gnatlink will not
8804 be able to find the generated file.
8807 @item gnatbind main -C -o mainprog.c -x
8810 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8812 The main program @code{Main} (source program in
8813 @file{main.adb}) is bound, excluding source files from the
8814 consistency checking, generating
8815 the file @file{mainprog.c}.
8818 @item gnatbind -x main_program -C -o mainprog.c
8819 This command is exactly the same as the previous example. Switches may
8820 appear anywhere in the command line, and single letter switches may be
8821 combined into a single switch.
8825 @item gnatbind -n math dbase -C -o ada-control.c
8828 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8830 The main program is in a language other than Ada, but calls to
8831 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8832 to @code{gnatbind} generates the file @file{ada-control.c} containing
8833 the @code{adainit} and @code{adafinal} routines to be called before and
8834 after accessing the Ada units.
8837 @c ------------------------------------
8838 @node Linking Using gnatlink
8839 @chapter Linking Using @command{gnatlink}
8840 @c ------------------------------------
8844 This chapter discusses @command{gnatlink}, a tool that links
8845 an Ada program and builds an executable file. This utility
8846 invokes the system linker ^(via the @command{gcc} command)^^
8847 with a correct list of object files and library references.
8848 @command{gnatlink} automatically determines the list of files and
8849 references for the Ada part of a program. It uses the binder file
8850 generated by the @command{gnatbind} to determine this list.
8852 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8853 driver (see @ref{The GNAT Driver and Project Files}).
8856 * Running gnatlink::
8857 * Switches for gnatlink::
8860 @node Running gnatlink
8861 @section Running @command{gnatlink}
8864 The form of the @command{gnatlink} command is
8867 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8868 @ovar{non-Ada objects} @ovar{linker options}
8872 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8874 or linker options) may be in any order, provided that no non-Ada object may
8875 be mistaken for a main @file{ALI} file.
8876 Any file name @file{F} without the @file{.ali}
8877 extension will be taken as the main @file{ALI} file if a file exists
8878 whose name is the concatenation of @file{F} and @file{.ali}.
8881 @file{@var{mainprog}.ali} references the ALI file of the main program.
8882 The @file{.ali} extension of this file can be omitted. From this
8883 reference, @command{gnatlink} locates the corresponding binder file
8884 @file{b~@var{mainprog}.adb} and, using the information in this file along
8885 with the list of non-Ada objects and linker options, constructs a
8886 linker command file to create the executable.
8888 The arguments other than the @command{gnatlink} switches and the main
8889 @file{ALI} file are passed to the linker uninterpreted.
8890 They typically include the names of
8891 object files for units written in other languages than Ada and any library
8892 references required to resolve references in any of these foreign language
8893 units, or in @code{Import} pragmas in any Ada units.
8895 @var{linker options} is an optional list of linker specific
8897 The default linker called by gnatlink is @command{gcc} which in
8898 turn calls the appropriate system linker.
8899 Standard options for the linker such as @option{-lmy_lib} or
8900 @option{-Ldir} can be added as is.
8901 For options that are not recognized by
8902 @command{gcc} as linker options, use the @command{gcc} switches
8903 @option{-Xlinker} or @option{-Wl,}.
8904 Refer to the GCC documentation for
8905 details. Here is an example showing how to generate a linker map:
8908 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8911 Using @var{linker options} it is possible to set the program stack and
8914 See @ref{Setting Stack Size from gnatlink} and
8915 @ref{Setting Heap Size from gnatlink}.
8918 @command{gnatlink} determines the list of objects required by the Ada
8919 program and prepends them to the list of objects passed to the linker.
8920 @command{gnatlink} also gathers any arguments set by the use of
8921 @code{pragma Linker_Options} and adds them to the list of arguments
8922 presented to the linker.
8925 @command{gnatlink} accepts the following types of extra files on the command
8926 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8927 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8928 handled according to their extension.
8931 @node Switches for gnatlink
8932 @section Switches for @command{gnatlink}
8935 The following switches are available with the @command{gnatlink} utility:
8941 @cindex @option{--version} @command{gnatlink}
8942 Display Copyright and version, then exit disregarding all other options.
8945 @cindex @option{--help} @command{gnatlink}
8946 If @option{--version} was not used, display usage, then exit disregarding
8949 @item ^-A^/BIND_FILE=ADA^
8950 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8951 The binder has generated code in Ada. This is the default.
8953 @item ^-C^/BIND_FILE=C^
8954 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8955 If instead of generating a file in Ada, the binder has generated one in
8956 C, then the linker needs to know about it. Use this switch to signal
8957 to @command{gnatlink} that the binder has generated C code rather than
8960 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8961 @cindex Command line length
8962 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8963 On some targets, the command line length is limited, and @command{gnatlink}
8964 will generate a separate file for the linker if the list of object files
8966 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8967 to be generated even if
8968 the limit is not exceeded. This is useful in some cases to deal with
8969 special situations where the command line length is exceeded.
8972 @cindex Debugging information, including
8973 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8974 The option to include debugging information causes the Ada bind file (in
8975 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8976 @option{^-g^/DEBUG^}.
8977 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8978 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8979 Without @option{^-g^/DEBUG^}, the binder removes these files by
8980 default. The same procedure apply if a C bind file was generated using
8981 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8982 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8984 @item ^-n^/NOCOMPILE^
8985 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8986 Do not compile the file generated by the binder. This may be used when
8987 a link is rerun with different options, but there is no need to recompile
8991 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8992 Causes additional information to be output, including a full list of the
8993 included object files. This switch option is most useful when you want
8994 to see what set of object files are being used in the link step.
8996 @item ^-v -v^/VERBOSE/VERBOSE^
8997 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8998 Very verbose mode. Requests that the compiler operate in verbose mode when
8999 it compiles the binder file, and that the system linker run in verbose mode.
9001 @item ^-o ^/EXECUTABLE=^@var{exec-name}
9002 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
9003 @var{exec-name} specifies an alternate name for the generated
9004 executable program. If this switch is omitted, the executable has the same
9005 name as the main unit. For example, @code{gnatlink try.ali} creates
9006 an executable called @file{^try^TRY.EXE^}.
9009 @item -b @var{target}
9010 @cindex @option{-b} (@command{gnatlink})
9011 Compile your program to run on @var{target}, which is the name of a
9012 system configuration. You must have a GNAT cross-compiler built if
9013 @var{target} is not the same as your host system.
9016 @cindex @option{-B} (@command{gnatlink})
9017 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
9018 from @var{dir} instead of the default location. Only use this switch
9019 when multiple versions of the GNAT compiler are available.
9020 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
9021 for further details. You would normally use the @option{-b} or
9022 @option{-V} switch instead.
9024 @item --GCC=@var{compiler_name}
9025 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
9026 Program used for compiling the binder file. The default is
9027 @command{gcc}. You need to use quotes around @var{compiler_name} if
9028 @code{compiler_name} contains spaces or other separator characters.
9029 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
9030 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
9031 inserted after your command name. Thus in the above example the compiler
9032 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
9033 A limitation of this syntax is that the name and path name of the executable
9034 itself must not include any embedded spaces. If the compiler executable is
9035 different from the default one (gcc or <prefix>-gcc), then the back-end
9036 switches in the ALI file are not used to compile the binder generated source.
9037 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
9038 switches will be used for @option{--GCC="gcc -gnatv"}. If several
9039 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
9040 is taken into account. However, all the additional switches are also taken
9042 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9043 @option{--GCC="bar -x -y -z -t"}.
9045 @item --LINK=@var{name}
9046 @cindex @option{--LINK=} (@command{gnatlink})
9047 @var{name} is the name of the linker to be invoked. This is especially
9048 useful in mixed language programs since languages such as C++ require
9049 their own linker to be used. When this switch is omitted, the default
9050 name for the linker is @command{gcc}. When this switch is used, the
9051 specified linker is called instead of @command{gcc} with exactly the same
9052 parameters that would have been passed to @command{gcc} so if the desired
9053 linker requires different parameters it is necessary to use a wrapper
9054 script that massages the parameters before invoking the real linker. It
9055 may be useful to control the exact invocation by using the verbose
9061 @item /DEBUG=TRACEBACK
9062 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9063 This qualifier causes sufficient information to be included in the
9064 executable file to allow a traceback, but does not include the full
9065 symbol information needed by the debugger.
9067 @item /IDENTIFICATION="<string>"
9068 @code{"<string>"} specifies the string to be stored in the image file
9069 identification field in the image header.
9070 It overrides any pragma @code{Ident} specified string.
9072 @item /NOINHIBIT-EXEC
9073 Generate the executable file even if there are linker warnings.
9075 @item /NOSTART_FILES
9076 Don't link in the object file containing the ``main'' transfer address.
9077 Used when linking with a foreign language main program compiled with an
9081 Prefer linking with object libraries over sharable images, even without
9087 @node The GNAT Make Program gnatmake
9088 @chapter The GNAT Make Program @command{gnatmake}
9092 * Running gnatmake::
9093 * Switches for gnatmake::
9094 * Mode Switches for gnatmake::
9095 * Notes on the Command Line::
9096 * How gnatmake Works::
9097 * Examples of gnatmake Usage::
9100 A typical development cycle when working on an Ada program consists of
9101 the following steps:
9105 Edit some sources to fix bugs.
9111 Compile all sources affected.
9121 The third step can be tricky, because not only do the modified files
9122 @cindex Dependency rules
9123 have to be compiled, but any files depending on these files must also be
9124 recompiled. The dependency rules in Ada can be quite complex, especially
9125 in the presence of overloading, @code{use} clauses, generics and inlined
9128 @command{gnatmake} automatically takes care of the third and fourth steps
9129 of this process. It determines which sources need to be compiled,
9130 compiles them, and binds and links the resulting object files.
9132 Unlike some other Ada make programs, the dependencies are always
9133 accurately recomputed from the new sources. The source based approach of
9134 the GNAT compilation model makes this possible. This means that if
9135 changes to the source program cause corresponding changes in
9136 dependencies, they will always be tracked exactly correctly by
9139 @node Running gnatmake
9140 @section Running @command{gnatmake}
9143 The usual form of the @command{gnatmake} command is
9146 $ gnatmake @ovar{switches} @var{file_name}
9147 @ovar{file_names} @ovar{mode_switches}
9151 The only required argument is one @var{file_name}, which specifies
9152 a compilation unit that is a main program. Several @var{file_names} can be
9153 specified: this will result in several executables being built.
9154 If @code{switches} are present, they can be placed before the first
9155 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9156 If @var{mode_switches} are present, they must always be placed after
9157 the last @var{file_name} and all @code{switches}.
9159 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9160 extension may be omitted from the @var{file_name} arguments. However, if
9161 you are using non-standard extensions, then it is required that the
9162 extension be given. A relative or absolute directory path can be
9163 specified in a @var{file_name}, in which case, the input source file will
9164 be searched for in the specified directory only. Otherwise, the input
9165 source file will first be searched in the directory where
9166 @command{gnatmake} was invoked and if it is not found, it will be search on
9167 the source path of the compiler as described in
9168 @ref{Search Paths and the Run-Time Library (RTL)}.
9170 All @command{gnatmake} output (except when you specify
9171 @option{^-M^/DEPENDENCIES_LIST^}) is to
9172 @file{stderr}. The output produced by the
9173 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9176 @node Switches for gnatmake
9177 @section Switches for @command{gnatmake}
9180 You may specify any of the following switches to @command{gnatmake}:
9186 @cindex @option{--version} @command{gnatmake}
9187 Display Copyright and version, then exit disregarding all other options.
9190 @cindex @option{--help} @command{gnatmake}
9191 If @option{--version} was not used, display usage, then exit disregarding
9195 @item --GCC=@var{compiler_name}
9196 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9197 Program used for compiling. The default is `@command{gcc}'. You need to use
9198 quotes around @var{compiler_name} if @code{compiler_name} contains
9199 spaces or other separator characters. As an example @option{--GCC="foo -x
9200 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9201 compiler. A limitation of this syntax is that the name and path name of
9202 the executable itself must not include any embedded spaces. Note that
9203 switch @option{-c} is always inserted after your command name. Thus in the
9204 above example the compiler command that will be used by @command{gnatmake}
9205 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9206 used, only the last @var{compiler_name} is taken into account. However,
9207 all the additional switches are also taken into account. Thus,
9208 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9209 @option{--GCC="bar -x -y -z -t"}.
9211 @item --GNATBIND=@var{binder_name}
9212 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9213 Program used for binding. The default is `@code{gnatbind}'. You need to
9214 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9215 or other separator characters. As an example @option{--GNATBIND="bar -x
9216 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9217 binder. Binder switches that are normally appended by @command{gnatmake}
9218 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9219 A limitation of this syntax is that the name and path name of the executable
9220 itself must not include any embedded spaces.
9222 @item --GNATLINK=@var{linker_name}
9223 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9224 Program used for linking. The default is `@command{gnatlink}'. You need to
9225 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9226 or other separator characters. As an example @option{--GNATLINK="lan -x
9227 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9228 linker. Linker switches that are normally appended by @command{gnatmake} to
9229 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9230 A limitation of this syntax is that the name and path name of the executable
9231 itself must not include any embedded spaces.
9235 @item ^-a^/ALL_FILES^
9236 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9237 Consider all files in the make process, even the GNAT internal system
9238 files (for example, the predefined Ada library files), as well as any
9239 locked files. Locked files are files whose ALI file is write-protected.
9241 @command{gnatmake} does not check these files,
9242 because the assumption is that the GNAT internal files are properly up
9243 to date, and also that any write protected ALI files have been properly
9244 installed. Note that if there is an installation problem, such that one
9245 of these files is not up to date, it will be properly caught by the
9247 You may have to specify this switch if you are working on GNAT
9248 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9249 in conjunction with @option{^-f^/FORCE_COMPILE^}
9250 if you need to recompile an entire application,
9251 including run-time files, using special configuration pragmas,
9252 such as a @code{Normalize_Scalars} pragma.
9255 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9258 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9261 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9264 @item ^-b^/ACTIONS=BIND^
9265 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9266 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9267 compilation and binding, but no link.
9268 Can be combined with @option{^-l^/ACTIONS=LINK^}
9269 to do binding and linking. When not combined with
9270 @option{^-c^/ACTIONS=COMPILE^}
9271 all the units in the closure of the main program must have been previously
9272 compiled and must be up to date. The root unit specified by @var{file_name}
9273 may be given without extension, with the source extension or, if no GNAT
9274 Project File is specified, with the ALI file extension.
9276 @item ^-c^/ACTIONS=COMPILE^
9277 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9278 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9279 is also specified. Do not perform linking, except if both
9280 @option{^-b^/ACTIONS=BIND^} and
9281 @option{^-l^/ACTIONS=LINK^} are also specified.
9282 If the root unit specified by @var{file_name} is not a main unit, this is the
9283 default. Otherwise @command{gnatmake} will attempt binding and linking
9284 unless all objects are up to date and the executable is more recent than
9288 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9289 Use a temporary mapping file. A mapping file is a way to communicate
9290 to the compiler two mappings: from unit names to file names (without
9291 any directory information) and from file names to path names (with
9292 full directory information). A mapping file can make the compiler's
9293 file searches faster, especially if there are many source directories,
9294 or the sources are read over a slow network connection. If
9295 @option{^-P^/PROJECT_FILE^} is used, a mapping file is always used, so
9296 @option{^-C^/MAPPING^} is unnecessary; in this case the mapping file
9297 is initially populated based on the project file. If
9298 @option{^-C^/MAPPING^} is used without
9299 @option{^-P^/PROJECT_FILE^},
9300 the mapping file is initially empty. Each invocation of the compiler
9301 will add any newly accessed sources to the mapping file.
9303 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9304 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9305 Use a specific mapping file. The file, specified as a path name (absolute or
9306 relative) by this switch, should already exist, otherwise the switch is
9307 ineffective. The specified mapping file will be communicated to the compiler.
9308 This switch is not compatible with a project file
9309 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9310 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9312 @item ^-d^/DISPLAY_PROGRESS^
9313 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9314 Display progress for each source, up to date or not, as a single line
9317 completed x out of y (zz%)
9320 If the file needs to be compiled this is displayed after the invocation of
9321 the compiler. These lines are displayed even in quiet output mode.
9323 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9324 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9325 Put all object files and ALI file in directory @var{dir}.
9326 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9327 and ALI files go in the current working directory.
9329 This switch cannot be used when using a project file.
9333 @cindex @option{-eL} (@command{gnatmake})
9334 @cindex symbolic links
9335 Follow all symbolic links when processing project files.
9336 This should be used if your project uses symbolic links for files or
9337 directories, but is not needed in other cases.
9339 @cindex naming scheme
9340 This also assumes that no directory matches the naming scheme for files (for
9341 instance that you do not have a directory called "sources.ads" when using the
9342 default GNAT naming scheme).
9344 When you do not have to use this switch (ie by default), gnatmake is able to
9345 save a lot of system calls (several per source file and object file), which
9346 can result in a significant speed up to load and manipulate a project file,
9347 especially when using source files from a remote system.
9351 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9352 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9353 Output the commands for the compiler, the binder and the linker
9354 on ^standard output^SYS$OUTPUT^,
9355 instead of ^standard error^SYS$ERROR^.
9357 @item ^-f^/FORCE_COMPILE^
9358 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9359 Force recompilations. Recompile all sources, even though some object
9360 files may be up to date, but don't recompile predefined or GNAT internal
9361 files or locked files (files with a write-protected ALI file),
9362 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9364 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9365 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9366 When using project files, if some errors or warnings are detected during
9367 parsing and verbose mode is not in effect (no use of switch
9368 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9369 file, rather than its simple file name.
9372 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9373 Enable debugging. This switch is simply passed to the compiler and to the
9376 @item ^-i^/IN_PLACE^
9377 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9378 In normal mode, @command{gnatmake} compiles all object files and ALI files
9379 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9380 then instead object files and ALI files that already exist are overwritten
9381 in place. This means that once a large project is organized into separate
9382 directories in the desired manner, then @command{gnatmake} will automatically
9383 maintain and update this organization. If no ALI files are found on the
9384 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9385 the new object and ALI files are created in the
9386 directory containing the source being compiled. If another organization
9387 is desired, where objects and sources are kept in different directories,
9388 a useful technique is to create dummy ALI files in the desired directories.
9389 When detecting such a dummy file, @command{gnatmake} will be forced to
9390 recompile the corresponding source file, and it will be put the resulting
9391 object and ALI files in the directory where it found the dummy file.
9393 @item ^-j^/PROCESSES=^@var{n}
9394 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9395 @cindex Parallel make
9396 Use @var{n} processes to carry out the (re)compilations. On a
9397 multiprocessor machine compilations will occur in parallel. In the
9398 event of compilation errors, messages from various compilations might
9399 get interspersed (but @command{gnatmake} will give you the full ordered
9400 list of failing compiles at the end). If this is problematic, rerun
9401 the make process with n set to 1 to get a clean list of messages.
9403 @item ^-k^/CONTINUE_ON_ERROR^
9404 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9405 Keep going. Continue as much as possible after a compilation error. To
9406 ease the programmer's task in case of compilation errors, the list of
9407 sources for which the compile fails is given when @command{gnatmake}
9410 If @command{gnatmake} is invoked with several @file{file_names} and with this
9411 switch, if there are compilation errors when building an executable,
9412 @command{gnatmake} will not attempt to build the following executables.
9414 @item ^-l^/ACTIONS=LINK^
9415 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9416 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9417 and linking. Linking will not be performed if combined with
9418 @option{^-c^/ACTIONS=COMPILE^}
9419 but not with @option{^-b^/ACTIONS=BIND^}.
9420 When not combined with @option{^-b^/ACTIONS=BIND^}
9421 all the units in the closure of the main program must have been previously
9422 compiled and must be up to date, and the main program needs to have been bound.
9423 The root unit specified by @var{file_name}
9424 may be given without extension, with the source extension or, if no GNAT
9425 Project File is specified, with the ALI file extension.
9427 @item ^-m^/MINIMAL_RECOMPILATION^
9428 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9429 Specify that the minimum necessary amount of recompilations
9430 be performed. In this mode @command{gnatmake} ignores time
9431 stamp differences when the only
9432 modifications to a source file consist in adding/removing comments,
9433 empty lines, spaces or tabs. This means that if you have changed the
9434 comments in a source file or have simply reformatted it, using this
9435 switch will tell @command{gnatmake} not to recompile files that depend on it
9436 (provided other sources on which these files depend have undergone no
9437 semantic modifications). Note that the debugging information may be
9438 out of date with respect to the sources if the @option{-m} switch causes
9439 a compilation to be switched, so the use of this switch represents a
9440 trade-off between compilation time and accurate debugging information.
9442 @item ^-M^/DEPENDENCIES_LIST^
9443 @cindex Dependencies, producing list
9444 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9445 Check if all objects are up to date. If they are, output the object
9446 dependences to @file{stdout} in a form that can be directly exploited in
9447 a @file{Makefile}. By default, each source file is prefixed with its
9448 (relative or absolute) directory name. This name is whatever you
9449 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9450 and @option{^-I^/SEARCH^} switches. If you use
9451 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9452 @option{^-q^/QUIET^}
9453 (see below), only the source file names,
9454 without relative paths, are output. If you just specify the
9455 @option{^-M^/DEPENDENCIES_LIST^}
9456 switch, dependencies of the GNAT internal system files are omitted. This
9457 is typically what you want. If you also specify
9458 the @option{^-a^/ALL_FILES^} switch,
9459 dependencies of the GNAT internal files are also listed. Note that
9460 dependencies of the objects in external Ada libraries (see switch
9461 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9464 @item ^-n^/DO_OBJECT_CHECK^
9465 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9466 Don't compile, bind, or link. Checks if all objects are up to date.
9467 If they are not, the full name of the first file that needs to be
9468 recompiled is printed.
9469 Repeated use of this option, followed by compiling the indicated source
9470 file, will eventually result in recompiling all required units.
9472 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9473 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9474 Output executable name. The name of the final executable program will be
9475 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9476 name for the executable will be the name of the input file in appropriate form
9477 for an executable file on the host system.
9479 This switch cannot be used when invoking @command{gnatmake} with several
9482 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9483 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9484 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9485 automatically missing object directories, library directories and exec
9488 @item ^-P^/PROJECT_FILE=^@var{project}
9489 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9490 Use project file @var{project}. Only one such switch can be used.
9491 @xref{gnatmake and Project Files}.
9494 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9495 Quiet. When this flag is not set, the commands carried out by
9496 @command{gnatmake} are displayed.
9498 @item ^-s^/SWITCH_CHECK/^
9499 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9500 Recompile if compiler switches have changed since last compilation.
9501 All compiler switches but -I and -o are taken into account in the
9503 orders between different ``first letter'' switches are ignored, but
9504 orders between same switches are taken into account. For example,
9505 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9506 is equivalent to @option{-O -g}.
9508 This switch is recommended when Integrated Preprocessing is used.
9511 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9512 Unique. Recompile at most the main files. It implies -c. Combined with
9513 -f, it is equivalent to calling the compiler directly. Note that using
9514 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9515 (@pxref{Project Files and Main Subprograms}).
9517 @item ^-U^/ALL_PROJECTS^
9518 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9519 When used without a project file or with one or several mains on the command
9520 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9521 on the command line, all sources of all project files are checked and compiled
9522 if not up to date, and libraries are rebuilt, if necessary.
9525 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9526 Verbose. Display the reason for all recompilations @command{gnatmake}
9527 decides are necessary, with the highest verbosity level.
9529 @item ^-vl^/LOW_VERBOSITY^
9530 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9531 Verbosity level Low. Display fewer lines than in verbosity Medium.
9533 @item ^-vm^/MEDIUM_VERBOSITY^
9534 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9535 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9537 @item ^-vh^/HIGH_VERBOSITY^
9538 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9539 Verbosity level High. Equivalent to ^-v^/REASONS^.
9541 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9542 Indicate the verbosity of the parsing of GNAT project files.
9543 @xref{Switches Related to Project Files}.
9545 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9546 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9547 Indicate that sources that are not part of any Project File may be compiled.
9548 Normally, when using Project Files, only sources that are part of a Project
9549 File may be compile. When this switch is used, a source outside of all Project
9550 Files may be compiled. The ALI file and the object file will be put in the
9551 object directory of the main Project. The compilation switches used will only
9552 be those specified on the command line. Even when
9553 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9554 command line need to be sources of a project file.
9556 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9557 Indicate that external variable @var{name} has the value @var{value}.
9558 The Project Manager will use this value for occurrences of
9559 @code{external(name)} when parsing the project file.
9560 @xref{Switches Related to Project Files}.
9563 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9564 No main subprogram. Bind and link the program even if the unit name
9565 given on the command line is a package name. The resulting executable
9566 will execute the elaboration routines of the package and its closure,
9567 then the finalization routines.
9572 @item @command{gcc} @asis{switches}
9574 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9575 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9578 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9579 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9580 automatically treated as a compiler switch, and passed on to all
9581 compilations that are carried out.
9586 Source and library search path switches:
9590 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9591 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9592 When looking for source files also look in directory @var{dir}.
9593 The order in which source files search is undertaken is
9594 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9596 @item ^-aL^/SKIP_MISSING=^@var{dir}
9597 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9598 Consider @var{dir} as being an externally provided Ada library.
9599 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9600 files have been located in directory @var{dir}. This allows you to have
9601 missing bodies for the units in @var{dir} and to ignore out of date bodies
9602 for the same units. You still need to specify
9603 the location of the specs for these units by using the switches
9604 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9605 or @option{^-I^/SEARCH=^@var{dir}}.
9606 Note: this switch is provided for compatibility with previous versions
9607 of @command{gnatmake}. The easier method of causing standard libraries
9608 to be excluded from consideration is to write-protect the corresponding
9611 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9612 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9613 When searching for library and object files, look in directory
9614 @var{dir}. The order in which library files are searched is described in
9615 @ref{Search Paths for gnatbind}.
9617 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9618 @cindex Search paths, for @command{gnatmake}
9619 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9620 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9621 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9623 @item ^-I^/SEARCH=^@var{dir}
9624 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9625 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9626 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9628 @item ^-I-^/NOCURRENT_DIRECTORY^
9629 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9630 @cindex Source files, suppressing search
9631 Do not look for source files in the directory containing the source
9632 file named in the command line.
9633 Do not look for ALI or object files in the directory
9634 where @command{gnatmake} was invoked.
9636 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9637 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9638 @cindex Linker libraries
9639 Add directory @var{dir} to the list of directories in which the linker
9640 will search for libraries. This is equivalent to
9641 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9643 Furthermore, under Windows, the sources pointed to by the libraries path
9644 set in the registry are not searched for.
9648 @cindex @option{-nostdinc} (@command{gnatmake})
9649 Do not look for source files in the system default directory.
9652 @cindex @option{-nostdlib} (@command{gnatmake})
9653 Do not look for library files in the system default directory.
9655 @item --RTS=@var{rts-path}
9656 @cindex @option{--RTS} (@command{gnatmake})
9657 Specifies the default location of the runtime library. GNAT looks for the
9659 in the following directories, and stops as soon as a valid runtime is found
9660 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9661 @file{ada_object_path} present):
9664 @item <current directory>/$rts_path
9666 @item <default-search-dir>/$rts_path
9668 @item <default-search-dir>/rts-$rts_path
9672 The selected path is handled like a normal RTS path.
9676 @node Mode Switches for gnatmake
9677 @section Mode Switches for @command{gnatmake}
9680 The mode switches (referred to as @code{mode_switches}) allow the
9681 inclusion of switches that are to be passed to the compiler itself, the
9682 binder or the linker. The effect of a mode switch is to cause all
9683 subsequent switches up to the end of the switch list, or up to the next
9684 mode switch, to be interpreted as switches to be passed on to the
9685 designated component of GNAT.
9689 @item -cargs @var{switches}
9690 @cindex @option{-cargs} (@command{gnatmake})
9691 Compiler switches. Here @var{switches} is a list of switches
9692 that are valid switches for @command{gcc}. They will be passed on to
9693 all compile steps performed by @command{gnatmake}.
9695 @item -bargs @var{switches}
9696 @cindex @option{-bargs} (@command{gnatmake})
9697 Binder switches. Here @var{switches} is a list of switches
9698 that are valid switches for @code{gnatbind}. They will be passed on to
9699 all bind steps performed by @command{gnatmake}.
9701 @item -largs @var{switches}
9702 @cindex @option{-largs} (@command{gnatmake})
9703 Linker switches. Here @var{switches} is a list of switches
9704 that are valid switches for @command{gnatlink}. They will be passed on to
9705 all link steps performed by @command{gnatmake}.
9707 @item -margs @var{switches}
9708 @cindex @option{-margs} (@command{gnatmake})
9709 Make switches. The switches are directly interpreted by @command{gnatmake},
9710 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9714 @node Notes on the Command Line
9715 @section Notes on the Command Line
9718 This section contains some additional useful notes on the operation
9719 of the @command{gnatmake} command.
9723 @cindex Recompilation, by @command{gnatmake}
9724 If @command{gnatmake} finds no ALI files, it recompiles the main program
9725 and all other units required by the main program.
9726 This means that @command{gnatmake}
9727 can be used for the initial compile, as well as during subsequent steps of
9728 the development cycle.
9731 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9732 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9733 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9737 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9738 is used to specify both source and
9739 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9740 instead if you just want to specify
9741 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9742 if you want to specify library paths
9746 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9747 This may conveniently be used to exclude standard libraries from
9748 consideration and in particular it means that the use of the
9749 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9750 unless @option{^-a^/ALL_FILES^} is also specified.
9753 @command{gnatmake} has been designed to make the use of Ada libraries
9754 particularly convenient. Assume you have an Ada library organized
9755 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9756 of your Ada compilation units,
9757 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9758 specs of these units, but no bodies. Then to compile a unit
9759 stored in @code{main.adb}, which uses this Ada library you would just type
9763 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9766 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9767 /SKIP_MISSING=@i{[OBJ_DIR]} main
9772 Using @command{gnatmake} along with the
9773 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9774 switch provides a mechanism for avoiding unnecessary recompilations. Using
9776 you can update the comments/format of your
9777 source files without having to recompile everything. Note, however, that
9778 adding or deleting lines in a source files may render its debugging
9779 info obsolete. If the file in question is a spec, the impact is rather
9780 limited, as that debugging info will only be useful during the
9781 elaboration phase of your program. For bodies the impact can be more
9782 significant. In all events, your debugger will warn you if a source file
9783 is more recent than the corresponding object, and alert you to the fact
9784 that the debugging information may be out of date.
9787 @node How gnatmake Works
9788 @section How @command{gnatmake} Works
9791 Generally @command{gnatmake} automatically performs all necessary
9792 recompilations and you don't need to worry about how it works. However,
9793 it may be useful to have some basic understanding of the @command{gnatmake}
9794 approach and in particular to understand how it uses the results of
9795 previous compilations without incorrectly depending on them.
9797 First a definition: an object file is considered @dfn{up to date} if the
9798 corresponding ALI file exists and if all the source files listed in the
9799 dependency section of this ALI file have time stamps matching those in
9800 the ALI file. This means that neither the source file itself nor any
9801 files that it depends on have been modified, and hence there is no need
9802 to recompile this file.
9804 @command{gnatmake} works by first checking if the specified main unit is up
9805 to date. If so, no compilations are required for the main unit. If not,
9806 @command{gnatmake} compiles the main program to build a new ALI file that
9807 reflects the latest sources. Then the ALI file of the main unit is
9808 examined to find all the source files on which the main program depends,
9809 and @command{gnatmake} recursively applies the above procedure on all these
9812 This process ensures that @command{gnatmake} only trusts the dependencies
9813 in an existing ALI file if they are known to be correct. Otherwise it
9814 always recompiles to determine a new, guaranteed accurate set of
9815 dependencies. As a result the program is compiled ``upside down'' from what may
9816 be more familiar as the required order of compilation in some other Ada
9817 systems. In particular, clients are compiled before the units on which
9818 they depend. The ability of GNAT to compile in any order is critical in
9819 allowing an order of compilation to be chosen that guarantees that
9820 @command{gnatmake} will recompute a correct set of new dependencies if
9823 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9824 imported by several of the executables, it will be recompiled at most once.
9826 Note: when using non-standard naming conventions
9827 (@pxref{Using Other File Names}), changing through a configuration pragmas
9828 file the version of a source and invoking @command{gnatmake} to recompile may
9829 have no effect, if the previous version of the source is still accessible
9830 by @command{gnatmake}. It may be necessary to use the switch
9831 ^-f^/FORCE_COMPILE^.
9833 @node Examples of gnatmake Usage
9834 @section Examples of @command{gnatmake} Usage
9837 @item gnatmake hello.adb
9838 Compile all files necessary to bind and link the main program
9839 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9840 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9842 @item gnatmake main1 main2 main3
9843 Compile all files necessary to bind and link the main programs
9844 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9845 (containing unit @code{Main2}) and @file{main3.adb}
9846 (containing unit @code{Main3}) and bind and link the resulting object files
9847 to generate three executable files @file{^main1^MAIN1.EXE^},
9848 @file{^main2^MAIN2.EXE^}
9849 and @file{^main3^MAIN3.EXE^}.
9852 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9856 @item gnatmake Main_Unit /QUIET
9857 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9858 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9860 Compile all files necessary to bind and link the main program unit
9861 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9862 be done with optimization level 2 and the order of elaboration will be
9863 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9864 displaying commands it is executing.
9867 @c *************************
9868 @node Improving Performance
9869 @chapter Improving Performance
9870 @cindex Improving performance
9873 This chapter presents several topics related to program performance.
9874 It first describes some of the tradeoffs that need to be considered
9875 and some of the techniques for making your program run faster.
9876 It then documents the @command{gnatelim} tool and unused subprogram/data
9877 elimination feature, which can reduce the size of program executables.
9879 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9880 driver (see @ref{The GNAT Driver and Project Files}).
9884 * Performance Considerations::
9885 * Text_IO Suggestions::
9886 * Reducing Size of Ada Executables with gnatelim::
9887 * Reducing Size of Executables with unused subprogram/data elimination::
9891 @c *****************************
9892 @node Performance Considerations
9893 @section Performance Considerations
9896 The GNAT system provides a number of options that allow a trade-off
9901 performance of the generated code
9904 speed of compilation
9907 minimization of dependences and recompilation
9910 the degree of run-time checking.
9914 The defaults (if no options are selected) aim at improving the speed
9915 of compilation and minimizing dependences, at the expense of performance
9916 of the generated code:
9923 no inlining of subprogram calls
9926 all run-time checks enabled except overflow and elaboration checks
9930 These options are suitable for most program development purposes. This
9931 chapter describes how you can modify these choices, and also provides
9932 some guidelines on debugging optimized code.
9935 * Controlling Run-Time Checks::
9936 * Use of Restrictions::
9937 * Optimization Levels::
9938 * Debugging Optimized Code::
9939 * Inlining of Subprograms::
9940 * Other Optimization Switches::
9941 * Optimization and Strict Aliasing::
9944 * Coverage Analysis::
9948 @node Controlling Run-Time Checks
9949 @subsection Controlling Run-Time Checks
9952 By default, GNAT generates all run-time checks, except integer overflow
9953 checks, stack overflow checks, and checks for access before elaboration on
9954 subprogram calls. The latter are not required in default mode, because all
9955 necessary checking is done at compile time.
9956 @cindex @option{-gnatp} (@command{gcc})
9957 @cindex @option{-gnato} (@command{gcc})
9958 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9959 be modified. @xref{Run-Time Checks}.
9961 Our experience is that the default is suitable for most development
9964 We treat integer overflow specially because these
9965 are quite expensive and in our experience are not as important as other
9966 run-time checks in the development process. Note that division by zero
9967 is not considered an overflow check, and divide by zero checks are
9968 generated where required by default.
9970 Elaboration checks are off by default, and also not needed by default, since
9971 GNAT uses a static elaboration analysis approach that avoids the need for
9972 run-time checking. This manual contains a full chapter discussing the issue
9973 of elaboration checks, and if the default is not satisfactory for your use,
9974 you should read this chapter.
9976 For validity checks, the minimal checks required by the Ada Reference
9977 Manual (for case statements and assignments to array elements) are on
9978 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9979 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9980 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9981 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9982 are also suppressed entirely if @option{-gnatp} is used.
9984 @cindex Overflow checks
9985 @cindex Checks, overflow
9988 @cindex pragma Suppress
9989 @cindex pragma Unsuppress
9990 Note that the setting of the switches controls the default setting of
9991 the checks. They may be modified using either @code{pragma Suppress} (to
9992 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9993 checks) in the program source.
9995 @node Use of Restrictions
9996 @subsection Use of Restrictions
9999 The use of pragma Restrictions allows you to control which features are
10000 permitted in your program. Apart from the obvious point that if you avoid
10001 relatively expensive features like finalization (enforceable by the use
10002 of pragma Restrictions (No_Finalization), the use of this pragma does not
10003 affect the generated code in most cases.
10005 One notable exception to this rule is that the possibility of task abort
10006 results in some distributed overhead, particularly if finalization or
10007 exception handlers are used. The reason is that certain sections of code
10008 have to be marked as non-abortable.
10010 If you use neither the @code{abort} statement, nor asynchronous transfer
10011 of control (@code{select @dots{} then abort}), then this distributed overhead
10012 is removed, which may have a general positive effect in improving
10013 overall performance. Especially code involving frequent use of tasking
10014 constructs and controlled types will show much improved performance.
10015 The relevant restrictions pragmas are
10017 @smallexample @c ada
10018 pragma Restrictions (No_Abort_Statements);
10019 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
10023 It is recommended that these restriction pragmas be used if possible. Note
10024 that this also means that you can write code without worrying about the
10025 possibility of an immediate abort at any point.
10027 @node Optimization Levels
10028 @subsection Optimization Levels
10029 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
10032 Without any optimization ^option,^qualifier,^
10033 the compiler's goal is to reduce the cost of
10034 compilation and to make debugging produce the expected results.
10035 Statements are independent: if you stop the program with a breakpoint between
10036 statements, you can then assign a new value to any variable or change
10037 the program counter to any other statement in the subprogram and get exactly
10038 the results you would expect from the source code.
10040 Turning on optimization makes the compiler attempt to improve the
10041 performance and/or code size at the expense of compilation time and
10042 possibly the ability to debug the program.
10044 If you use multiple
10045 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10046 the last such option is the one that is effective.
10049 The default is optimization off. This results in the fastest compile
10050 times, but GNAT makes absolutely no attempt to optimize, and the
10051 generated programs are considerably larger and slower than when
10052 optimization is enabled. You can use the
10054 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10055 @option{-O2}, @option{-O3}, and @option{-Os})
10058 @code{OPTIMIZE} qualifier
10060 to @command{gcc} to control the optimization level:
10063 @item ^-O0^/OPTIMIZE=NONE^
10064 No optimization (the default);
10065 generates unoptimized code but has
10066 the fastest compilation time.
10068 Note that many other compilers do fairly extensive optimization
10069 even if ``no optimization'' is specified. With gcc, it is
10070 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10071 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10072 really does mean no optimization at all. This difference between
10073 gcc and other compilers should be kept in mind when doing
10074 performance comparisons.
10076 @item ^-O1^/OPTIMIZE=SOME^
10077 Moderate optimization;
10078 optimizes reasonably well but does not
10079 degrade compilation time significantly.
10081 @item ^-O2^/OPTIMIZE=ALL^
10083 @itemx /OPTIMIZE=DEVELOPMENT
10086 generates highly optimized code and has
10087 the slowest compilation time.
10089 @item ^-O3^/OPTIMIZE=INLINING^
10090 Full optimization as in @option{-O2},
10091 and also attempts automatic inlining of small
10092 subprograms within a unit (@pxref{Inlining of Subprograms}).
10094 @item ^-Os^/OPTIMIZE=SPACE^
10095 Optimize space usage of resulting program.
10099 Higher optimization levels perform more global transformations on the
10100 program and apply more expensive analysis algorithms in order to generate
10101 faster and more compact code. The price in compilation time, and the
10102 resulting improvement in execution time,
10103 both depend on the particular application and the hardware environment.
10104 You should experiment to find the best level for your application.
10106 Since the precise set of optimizations done at each level will vary from
10107 release to release (and sometime from target to target), it is best to think
10108 of the optimization settings in general terms.
10109 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10110 the GNU Compiler Collection (GCC)}, for details about
10111 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10112 individually enable or disable specific optimizations.
10114 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10115 been tested extensively at all optimization levels. There are some bugs
10116 which appear only with optimization turned on, but there have also been
10117 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10118 level of optimization does not improve the reliability of the code
10119 generator, which in practice is highly reliable at all optimization
10122 Note regarding the use of @option{-O3}: The use of this optimization level
10123 is generally discouraged with GNAT, since it often results in larger
10124 executables which run more slowly. See further discussion of this point
10125 in @ref{Inlining of Subprograms}.
10127 @node Debugging Optimized Code
10128 @subsection Debugging Optimized Code
10129 @cindex Debugging optimized code
10130 @cindex Optimization and debugging
10133 Although it is possible to do a reasonable amount of debugging at
10135 nonzero optimization levels,
10136 the higher the level the more likely that
10139 @option{/OPTIMIZE} settings other than @code{NONE},
10140 such settings will make it more likely that
10142 source-level constructs will have been eliminated by optimization.
10143 For example, if a loop is strength-reduced, the loop
10144 control variable may be completely eliminated and thus cannot be
10145 displayed in the debugger.
10146 This can only happen at @option{-O2} or @option{-O3}.
10147 Explicit temporary variables that you code might be eliminated at
10148 ^level^setting^ @option{-O1} or higher.
10150 The use of the @option{^-g^/DEBUG^} switch,
10151 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10152 which is needed for source-level debugging,
10153 affects the size of the program executable on disk,
10154 and indeed the debugging information can be quite large.
10155 However, it has no effect on the generated code (and thus does not
10156 degrade performance)
10158 Since the compiler generates debugging tables for a compilation unit before
10159 it performs optimizations, the optimizing transformations may invalidate some
10160 of the debugging data. You therefore need to anticipate certain
10161 anomalous situations that may arise while debugging optimized code.
10162 These are the most common cases:
10166 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10168 the PC bouncing back and forth in the code. This may result from any of
10169 the following optimizations:
10173 @i{Common subexpression elimination:} using a single instance of code for a
10174 quantity that the source computes several times. As a result you
10175 may not be able to stop on what looks like a statement.
10178 @i{Invariant code motion:} moving an expression that does not change within a
10179 loop, to the beginning of the loop.
10182 @i{Instruction scheduling:} moving instructions so as to
10183 overlap loads and stores (typically) with other code, or in
10184 general to move computations of values closer to their uses. Often
10185 this causes you to pass an assignment statement without the assignment
10186 happening and then later bounce back to the statement when the
10187 value is actually needed. Placing a breakpoint on a line of code
10188 and then stepping over it may, therefore, not always cause all the
10189 expected side-effects.
10193 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10194 two identical pieces of code are merged and the program counter suddenly
10195 jumps to a statement that is not supposed to be executed, simply because
10196 it (and the code following) translates to the same thing as the code
10197 that @emph{was} supposed to be executed. This effect is typically seen in
10198 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10199 a @code{break} in a C @code{^switch^switch^} statement.
10202 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10203 There are various reasons for this effect:
10207 In a subprogram prologue, a parameter may not yet have been moved to its
10211 A variable may be dead, and its register re-used. This is
10212 probably the most common cause.
10215 As mentioned above, the assignment of a value to a variable may
10219 A variable may be eliminated entirely by value propagation or
10220 other means. In this case, GCC may incorrectly generate debugging
10221 information for the variable
10225 In general, when an unexpected value appears for a local variable or parameter
10226 you should first ascertain if that value was actually computed by
10227 your program, as opposed to being incorrectly reported by the debugger.
10229 array elements in an object designated by an access value
10230 are generally less of a problem, once you have ascertained that the access
10232 Typically, this means checking variables in the preceding code and in the
10233 calling subprogram to verify that the value observed is explainable from other
10234 values (one must apply the procedure recursively to those
10235 other values); or re-running the code and stopping a little earlier
10236 (perhaps before the call) and stepping to better see how the variable obtained
10237 the value in question; or continuing to step @emph{from} the point of the
10238 strange value to see if code motion had simply moved the variable's
10243 In light of such anomalies, a recommended technique is to use @option{-O0}
10244 early in the software development cycle, when extensive debugging capabilities
10245 are most needed, and then move to @option{-O1} and later @option{-O2} as
10246 the debugger becomes less critical.
10247 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10248 a release management issue.
10250 Note that if you use @option{-g} you can then use the @command{strip} program
10251 on the resulting executable,
10252 which removes both debugging information and global symbols.
10255 @node Inlining of Subprograms
10256 @subsection Inlining of Subprograms
10259 A call to a subprogram in the current unit is inlined if all the
10260 following conditions are met:
10264 The optimization level is at least @option{-O1}.
10267 The called subprogram is suitable for inlining: It must be small enough
10268 and not contain something that @command{gcc} cannot support in inlined
10272 @cindex pragma Inline
10274 Either @code{pragma Inline} applies to the subprogram, or it is local
10275 to the unit and called once from within it, or it is small and automatic
10276 inlining (optimization level @option{-O3}) is specified.
10280 Calls to subprograms in @code{with}'ed units are normally not inlined.
10281 To achieve actual inlining (that is, replacement of the call by the code
10282 in the body of the subprogram), the following conditions must all be true.
10286 The optimization level is at least @option{-O1}.
10289 The called subprogram is suitable for inlining: It must be small enough
10290 and not contain something that @command{gcc} cannot support in inlined
10294 The call appears in a body (not in a package spec).
10297 There is a @code{pragma Inline} for the subprogram.
10300 @cindex @option{-gnatn} (@command{gcc})
10301 The @option{^-gnatn^/INLINE^} switch
10302 is used in the @command{gcc} command line
10305 Even if all these conditions are met, it may not be possible for
10306 the compiler to inline the call, due to the length of the body,
10307 or features in the body that make it impossible for the compiler
10308 to do the inlining.
10310 Note that specifying the @option{-gnatn} switch causes additional
10311 compilation dependencies. Consider the following:
10313 @smallexample @c ada
10333 With the default behavior (no @option{-gnatn} switch specified), the
10334 compilation of the @code{Main} procedure depends only on its own source,
10335 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10336 means that editing the body of @code{R} does not require recompiling
10339 On the other hand, the call @code{R.Q} is not inlined under these
10340 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10341 is compiled, the call will be inlined if the body of @code{Q} is small
10342 enough, but now @code{Main} depends on the body of @code{R} in
10343 @file{r.adb} as well as on the spec. This means that if this body is edited,
10344 the main program must be recompiled. Note that this extra dependency
10345 occurs whether or not the call is in fact inlined by @command{gcc}.
10347 The use of front end inlining with @option{-gnatN} generates similar
10348 additional dependencies.
10350 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10351 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10352 can be used to prevent
10353 all inlining. This switch overrides all other conditions and ensures
10354 that no inlining occurs. The extra dependences resulting from
10355 @option{-gnatn} will still be active, even if
10356 this switch is used to suppress the resulting inlining actions.
10358 @cindex @option{-fno-inline-functions} (@command{gcc})
10359 Note: The @option{-fno-inline-functions} switch can be used to prevent
10360 automatic inlining of small subprograms if @option{-O3} is used.
10362 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10363 Note: The @option{-fno-inline-functions-called-once} switch
10364 can be used to prevent inlining of subprograms local to the unit
10365 and called once from within it if @option{-O1} is used.
10367 Note regarding the use of @option{-O3}: There is no difference in inlining
10368 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10369 pragma @code{Inline} assuming the use of @option{-gnatn}
10370 or @option{-gnatN} (the switches that activate inlining). If you have used
10371 pragma @code{Inline} in appropriate cases, then it is usually much better
10372 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10373 in this case only has the effect of inlining subprograms you did not
10374 think should be inlined. We often find that the use of @option{-O3} slows
10375 down code by performing excessive inlining, leading to increased instruction
10376 cache pressure from the increased code size. So the bottom line here is
10377 that you should not automatically assume that @option{-O3} is better than
10378 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10379 it actually improves performance.
10381 @node Other Optimization Switches
10382 @subsection Other Optimization Switches
10383 @cindex Optimization Switches
10385 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10386 @command{gcc} optimization switches are potentially usable. These switches
10387 have not been extensively tested with GNAT but can generally be expected
10388 to work. Examples of switches in this category are
10389 @option{-funroll-loops} and
10390 the various target-specific @option{-m} options (in particular, it has been
10391 observed that @option{-march=pentium4} can significantly improve performance
10392 on appropriate machines). For full details of these switches, see
10393 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10394 the GNU Compiler Collection (GCC)}.
10396 @node Optimization and Strict Aliasing
10397 @subsection Optimization and Strict Aliasing
10399 @cindex Strict Aliasing
10400 @cindex No_Strict_Aliasing
10403 The strong typing capabilities of Ada allow an optimizer to generate
10404 efficient code in situations where other languages would be forced to
10405 make worst case assumptions preventing such optimizations. Consider
10406 the following example:
10408 @smallexample @c ada
10411 type Int1 is new Integer;
10412 type Int2 is new Integer;
10413 type Int1A is access Int1;
10414 type Int2A is access Int2;
10421 for J in Data'Range loop
10422 if Data (J) = Int1V.all then
10423 Int2V.all := Int2V.all + 1;
10432 In this example, since the variable @code{Int1V} can only access objects
10433 of type @code{Int1}, and @code{Int2V} can only access objects of type
10434 @code{Int2}, there is no possibility that the assignment to
10435 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10436 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10437 for all iterations of the loop and avoid the extra memory reference
10438 required to dereference it each time through the loop.
10440 This kind of optimization, called strict aliasing analysis, is
10441 triggered by specifying an optimization level of @option{-O2} or
10442 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10443 when access values are involved.
10445 However, although this optimization is always correct in terms of
10446 the formal semantics of the Ada Reference Manual, difficulties can
10447 arise if features like @code{Unchecked_Conversion} are used to break
10448 the typing system. Consider the following complete program example:
10450 @smallexample @c ada
10453 type int1 is new integer;
10454 type int2 is new integer;
10455 type a1 is access int1;
10456 type a2 is access int2;
10461 function to_a2 (Input : a1) return a2;
10464 with Unchecked_Conversion;
10466 function to_a2 (Input : a1) return a2 is
10468 new Unchecked_Conversion (a1, a2);
10470 return to_a2u (Input);
10476 with Text_IO; use Text_IO;
10478 v1 : a1 := new int1;
10479 v2 : a2 := to_a2 (v1);
10483 put_line (int1'image (v1.all));
10489 This program prints out 0 in @option{-O0} or @option{-O1}
10490 mode, but it prints out 1 in @option{-O2} mode. That's
10491 because in strict aliasing mode, the compiler can and
10492 does assume that the assignment to @code{v2.all} could not
10493 affect the value of @code{v1.all}, since different types
10496 This behavior is not a case of non-conformance with the standard, since
10497 the Ada RM specifies that an unchecked conversion where the resulting
10498 bit pattern is not a correct value of the target type can result in an
10499 abnormal value and attempting to reference an abnormal value makes the
10500 execution of a program erroneous. That's the case here since the result
10501 does not point to an object of type @code{int2}. This means that the
10502 effect is entirely unpredictable.
10504 However, although that explanation may satisfy a language
10505 lawyer, in practice an applications programmer expects an
10506 unchecked conversion involving pointers to create true
10507 aliases and the behavior of printing 1 seems plain wrong.
10508 In this case, the strict aliasing optimization is unwelcome.
10510 Indeed the compiler recognizes this possibility, and the
10511 unchecked conversion generates a warning:
10514 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10515 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10516 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10520 Unfortunately the problem is recognized when compiling the body of
10521 package @code{p2}, but the actual "bad" code is generated while
10522 compiling the body of @code{m} and this latter compilation does not see
10523 the suspicious @code{Unchecked_Conversion}.
10525 As implied by the warning message, there are approaches you can use to
10526 avoid the unwanted strict aliasing optimization in a case like this.
10528 One possibility is to simply avoid the use of @option{-O2}, but
10529 that is a bit drastic, since it throws away a number of useful
10530 optimizations that do not involve strict aliasing assumptions.
10532 A less drastic approach is to compile the program using the
10533 option @option{-fno-strict-aliasing}. Actually it is only the
10534 unit containing the dereferencing of the suspicious pointer
10535 that needs to be compiled. So in this case, if we compile
10536 unit @code{m} with this switch, then we get the expected
10537 value of zero printed. Analyzing which units might need
10538 the switch can be painful, so a more reasonable approach
10539 is to compile the entire program with options @option{-O2}
10540 and @option{-fno-strict-aliasing}. If the performance is
10541 satisfactory with this combination of options, then the
10542 advantage is that the entire issue of possible "wrong"
10543 optimization due to strict aliasing is avoided.
10545 To avoid the use of compiler switches, the configuration
10546 pragma @code{No_Strict_Aliasing} with no parameters may be
10547 used to specify that for all access types, the strict
10548 aliasing optimization should be suppressed.
10550 However, these approaches are still overkill, in that they causes
10551 all manipulations of all access values to be deoptimized. A more
10552 refined approach is to concentrate attention on the specific
10553 access type identified as problematic.
10555 First, if a careful analysis of uses of the pointer shows
10556 that there are no possible problematic references, then
10557 the warning can be suppressed by bracketing the
10558 instantiation of @code{Unchecked_Conversion} to turn
10561 @smallexample @c ada
10562 pragma Warnings (Off);
10564 new Unchecked_Conversion (a1, a2);
10565 pragma Warnings (On);
10569 Of course that approach is not appropriate for this particular
10570 example, since indeed there is a problematic reference. In this
10571 case we can take one of two other approaches.
10573 The first possibility is to move the instantiation of unchecked
10574 conversion to the unit in which the type is declared. In
10575 this example, we would move the instantiation of
10576 @code{Unchecked_Conversion} from the body of package
10577 @code{p2} to the spec of package @code{p1}. Now the
10578 warning disappears. That's because any use of the
10579 access type knows there is a suspicious unchecked
10580 conversion, and the strict aliasing optimization
10581 is automatically suppressed for the type.
10583 If it is not practical to move the unchecked conversion to the same unit
10584 in which the destination access type is declared (perhaps because the
10585 source type is not visible in that unit), you may use pragma
10586 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10587 same declarative sequence as the declaration of the access type:
10589 @smallexample @c ada
10590 type a2 is access int2;
10591 pragma No_Strict_Aliasing (a2);
10595 Here again, the compiler now knows that the strict aliasing optimization
10596 should be suppressed for any reference to type @code{a2} and the
10597 expected behavior is obtained.
10599 Finally, note that although the compiler can generate warnings for
10600 simple cases of unchecked conversions, there are tricker and more
10601 indirect ways of creating type incorrect aliases which the compiler
10602 cannot detect. Examples are the use of address overlays and unchecked
10603 conversions involving composite types containing access types as
10604 components. In such cases, no warnings are generated, but there can
10605 still be aliasing problems. One safe coding practice is to forbid the
10606 use of address clauses for type overlaying, and to allow unchecked
10607 conversion only for primitive types. This is not really a significant
10608 restriction since any possible desired effect can be achieved by
10609 unchecked conversion of access values.
10611 The aliasing analysis done in strict aliasing mode can certainly
10612 have significant benefits. We have seen cases of large scale
10613 application code where the time is increased by up to 5% by turning
10614 this optimization off. If you have code that includes significant
10615 usage of unchecked conversion, you might want to just stick with
10616 @option{-O1} and avoid the entire issue. If you get adequate
10617 performance at this level of optimization level, that's probably
10618 the safest approach. If tests show that you really need higher
10619 levels of optimization, then you can experiment with @option{-O2}
10620 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10621 has on size and speed of the code. If you really need to use
10622 @option{-O2} with strict aliasing in effect, then you should
10623 review any uses of unchecked conversion of access types,
10624 particularly if you are getting the warnings described above.
10627 @node Coverage Analysis
10628 @subsection Coverage Analysis
10631 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10632 the user to determine the distribution of execution time across a program,
10633 @pxref{Profiling} for details of usage.
10637 @node Text_IO Suggestions
10638 @section @code{Text_IO} Suggestions
10639 @cindex @code{Text_IO} and performance
10642 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10643 the requirement of maintaining page and line counts. If performance
10644 is critical, a recommendation is to use @code{Stream_IO} instead of
10645 @code{Text_IO} for volume output, since this package has less overhead.
10647 If @code{Text_IO} must be used, note that by default output to the standard
10648 output and standard error files is unbuffered (this provides better
10649 behavior when output statements are used for debugging, or if the
10650 progress of a program is observed by tracking the output, e.g. by
10651 using the Unix @command{tail -f} command to watch redirected output.
10653 If you are generating large volumes of output with @code{Text_IO} and
10654 performance is an important factor, use a designated file instead
10655 of the standard output file, or change the standard output file to
10656 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10660 @node Reducing Size of Ada Executables with gnatelim
10661 @section Reducing Size of Ada Executables with @code{gnatelim}
10665 This section describes @command{gnatelim}, a tool which detects unused
10666 subprograms and helps the compiler to create a smaller executable for your
10671 * Running gnatelim::
10672 * Correcting the List of Eliminate Pragmas::
10673 * Making Your Executables Smaller::
10674 * Summary of the gnatelim Usage Cycle::
10677 @node About gnatelim
10678 @subsection About @code{gnatelim}
10681 When a program shares a set of Ada
10682 packages with other programs, it may happen that this program uses
10683 only a fraction of the subprograms defined in these packages. The code
10684 created for these unused subprograms increases the size of the executable.
10686 @code{gnatelim} tracks unused subprograms in an Ada program and
10687 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10688 subprograms that are declared but never called. By placing the list of
10689 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10690 recompiling your program, you may decrease the size of its executable,
10691 because the compiler will not generate the code for 'eliminated' subprograms.
10692 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10693 information about this pragma.
10695 @code{gnatelim} needs as its input data the name of the main subprogram
10696 and a bind file for a main subprogram.
10698 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10699 the main subprogram. @code{gnatelim} can work with both Ada and C
10700 bind files; when both are present, it uses the Ada bind file.
10701 The following commands will build the program and create the bind file:
10704 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10705 $ gnatbind main_prog
10708 Note that @code{gnatelim} needs neither object nor ALI files.
10710 @node Running gnatelim
10711 @subsection Running @code{gnatelim}
10714 @code{gnatelim} has the following command-line interface:
10717 $ gnatelim @ovar{options} name
10721 @code{name} should be a name of a source file that contains the main subprogram
10722 of a program (partition).
10724 @code{gnatelim} has the following switches:
10729 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10730 Quiet mode: by default @code{gnatelim} outputs to the standard error
10731 stream the number of program units left to be processed. This option turns
10734 @item ^-v^/VERBOSE^
10735 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10736 Verbose mode: @code{gnatelim} version information is printed as Ada
10737 comments to the standard output stream. Also, in addition to the number of
10738 program units left @code{gnatelim} will output the name of the current unit
10742 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10743 Also look for subprograms from the GNAT run time that can be eliminated. Note
10744 that when @file{gnat.adc} is produced using this switch, the entire program
10745 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10747 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10748 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10749 When looking for source files also look in directory @var{dir}. Specifying
10750 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10751 sources in the current directory.
10753 @item ^-b^/BIND_FILE=^@var{bind_file}
10754 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10755 Specifies @var{bind_file} as the bind file to process. If not set, the name
10756 of the bind file is computed from the full expanded Ada name
10757 of a main subprogram.
10759 @item ^-C^/CONFIG_FILE=^@var{config_file}
10760 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10761 Specifies a file @var{config_file} that contains configuration pragmas. The
10762 file must be specified with full path.
10764 @item ^--GCC^/COMPILER^=@var{compiler_name}
10765 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10766 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10767 available on the path.
10769 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10770 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10771 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10772 available on the path.
10776 @code{gnatelim} sends its output to the standard output stream, and all the
10777 tracing and debug information is sent to the standard error stream.
10778 In order to produce a proper GNAT configuration file
10779 @file{gnat.adc}, redirection must be used:
10783 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10786 $ gnatelim main_prog.adb > gnat.adc
10795 $ gnatelim main_prog.adb >> gnat.adc
10799 in order to append the @code{gnatelim} output to the existing contents of
10803 @node Correcting the List of Eliminate Pragmas
10804 @subsection Correcting the List of Eliminate Pragmas
10807 In some rare cases @code{gnatelim} may try to eliminate
10808 subprograms that are actually called in the program. In this case, the
10809 compiler will generate an error message of the form:
10812 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10816 You will need to manually remove the wrong @code{Eliminate} pragmas from
10817 the @file{gnat.adc} file. You should recompile your program
10818 from scratch after that, because you need a consistent @file{gnat.adc} file
10819 during the entire compilation.
10821 @node Making Your Executables Smaller
10822 @subsection Making Your Executables Smaller
10825 In order to get a smaller executable for your program you now have to
10826 recompile the program completely with the new @file{gnat.adc} file
10827 created by @code{gnatelim} in your current directory:
10830 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10834 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10835 recompile everything
10836 with the set of pragmas @code{Eliminate} that you have obtained with
10837 @command{gnatelim}).
10839 Be aware that the set of @code{Eliminate} pragmas is specific to each
10840 program. It is not recommended to merge sets of @code{Eliminate}
10841 pragmas created for different programs in one @file{gnat.adc} file.
10843 @node Summary of the gnatelim Usage Cycle
10844 @subsection Summary of the gnatelim Usage Cycle
10847 Here is a quick summary of the steps to be taken in order to reduce
10848 the size of your executables with @code{gnatelim}. You may use
10849 other GNAT options to control the optimization level,
10850 to produce the debugging information, to set search path, etc.
10854 Produce a bind file
10857 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10858 $ gnatbind main_prog
10862 Generate a list of @code{Eliminate} pragmas
10865 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10868 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10873 Recompile the application
10876 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10881 @node Reducing Size of Executables with unused subprogram/data elimination
10882 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10883 @findex unused subprogram/data elimination
10886 This section describes how you can eliminate unused subprograms and data from
10887 your executable just by setting options at compilation time.
10890 * About unused subprogram/data elimination::
10891 * Compilation options::
10892 * Example of unused subprogram/data elimination::
10895 @node About unused subprogram/data elimination
10896 @subsection About unused subprogram/data elimination
10899 By default, an executable contains all code and data of its composing objects
10900 (directly linked or coming from statically linked libraries), even data or code
10901 never used by this executable.
10903 This feature will allow you to eliminate such unused code from your
10904 executable, making it smaller (in disk and in memory).
10906 This functionality is available on all Linux platforms except for the IA-64
10907 architecture and on all cross platforms using the ELF binary file format.
10908 In both cases GNU binutils version 2.16 or later are required to enable it.
10910 @node Compilation options
10911 @subsection Compilation options
10914 The operation of eliminating the unused code and data from the final executable
10915 is directly performed by the linker.
10917 In order to do this, it has to work with objects compiled with the
10919 @option{-ffunction-sections} @option{-fdata-sections}.
10920 @cindex @option{-ffunction-sections} (@command{gcc})
10921 @cindex @option{-fdata-sections} (@command{gcc})
10922 These options are usable with C and Ada files.
10923 They will place respectively each
10924 function or data in a separate section in the resulting object file.
10926 Once the objects and static libraries are created with these options, the
10927 linker can perform the dead code elimination. You can do this by setting
10928 the @option{-Wl,--gc-sections} option to gcc command or in the
10929 @option{-largs} section of @command{gnatmake}. This will perform a
10930 garbage collection of code and data never referenced.
10932 If the linker performs a partial link (@option{-r} ld linker option), then you
10933 will need to provide one or several entry point using the
10934 @option{-e} / @option{--entry} ld option.
10936 Note that objects compiled without the @option{-ffunction-sections} and
10937 @option{-fdata-sections} options can still be linked with the executable.
10938 However, no dead code elimination will be performed on those objects (they will
10941 The GNAT static library is now compiled with -ffunction-sections and
10942 -fdata-sections on some platforms. This allows you to eliminate the unused code
10943 and data of the GNAT library from your executable.
10945 @node Example of unused subprogram/data elimination
10946 @subsection Example of unused subprogram/data elimination
10949 Here is a simple example:
10951 @smallexample @c ada
10960 Used_Data : Integer;
10961 Unused_Data : Integer;
10963 procedure Used (Data : Integer);
10964 procedure Unused (Data : Integer);
10967 package body Aux is
10968 procedure Used (Data : Integer) is
10973 procedure Unused (Data : Integer) is
10975 Unused_Data := Data;
10981 @code{Unused} and @code{Unused_Data} are never referenced in this code
10982 excerpt, and hence they may be safely removed from the final executable.
10987 $ nm test | grep used
10988 020015f0 T aux__unused
10989 02005d88 B aux__unused_data
10990 020015cc T aux__used
10991 02005d84 B aux__used_data
10993 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10994 -largs -Wl,--gc-sections
10996 $ nm test | grep used
10997 02005350 T aux__used
10998 0201ffe0 B aux__used_data
11002 It can be observed that the procedure @code{Unused} and the object
11003 @code{Unused_Data} are removed by the linker when using the
11004 appropriate options.
11006 @c ********************************
11007 @node Renaming Files Using gnatchop
11008 @chapter Renaming Files Using @code{gnatchop}
11012 This chapter discusses how to handle files with multiple units by using
11013 the @code{gnatchop} utility. This utility is also useful in renaming
11014 files to meet the standard GNAT default file naming conventions.
11017 * Handling Files with Multiple Units::
11018 * Operating gnatchop in Compilation Mode::
11019 * Command Line for gnatchop::
11020 * Switches for gnatchop::
11021 * Examples of gnatchop Usage::
11024 @node Handling Files with Multiple Units
11025 @section Handling Files with Multiple Units
11028 The basic compilation model of GNAT requires that a file submitted to the
11029 compiler have only one unit and there be a strict correspondence
11030 between the file name and the unit name.
11032 The @code{gnatchop} utility allows both of these rules to be relaxed,
11033 allowing GNAT to process files which contain multiple compilation units
11034 and files with arbitrary file names. @code{gnatchop}
11035 reads the specified file and generates one or more output files,
11036 containing one unit per file. The unit and the file name correspond,
11037 as required by GNAT.
11039 If you want to permanently restructure a set of ``foreign'' files so that
11040 they match the GNAT rules, and do the remaining development using the
11041 GNAT structure, you can simply use @command{gnatchop} once, generate the
11042 new set of files and work with them from that point on.
11044 Alternatively, if you want to keep your files in the ``foreign'' format,
11045 perhaps to maintain compatibility with some other Ada compilation
11046 system, you can set up a procedure where you use @command{gnatchop} each
11047 time you compile, regarding the source files that it writes as temporary
11048 files that you throw away.
11050 Note that if your file containing multiple units starts with a byte order
11051 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11052 will each start with a copy of this BOM, meaning that they can be compiled
11053 automatically in UTF-8 mode without needing to specify an explicit encoding.
11055 @node Operating gnatchop in Compilation Mode
11056 @section Operating gnatchop in Compilation Mode
11059 The basic function of @code{gnatchop} is to take a file with multiple units
11060 and split it into separate files. The boundary between files is reasonably
11061 clear, except for the issue of comments and pragmas. In default mode, the
11062 rule is that any pragmas between units belong to the previous unit, except
11063 that configuration pragmas always belong to the following unit. Any comments
11064 belong to the following unit. These rules
11065 almost always result in the right choice of
11066 the split point without needing to mark it explicitly and most users will
11067 find this default to be what they want. In this default mode it is incorrect to
11068 submit a file containing only configuration pragmas, or one that ends in
11069 configuration pragmas, to @code{gnatchop}.
11071 However, using a special option to activate ``compilation mode'',
11073 can perform another function, which is to provide exactly the semantics
11074 required by the RM for handling of configuration pragmas in a compilation.
11075 In the absence of configuration pragmas (at the main file level), this
11076 option has no effect, but it causes such configuration pragmas to be handled
11077 in a quite different manner.
11079 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11080 only configuration pragmas, then this file is appended to the
11081 @file{gnat.adc} file in the current directory. This behavior provides
11082 the required behavior described in the RM for the actions to be taken
11083 on submitting such a file to the compiler, namely that these pragmas
11084 should apply to all subsequent compilations in the same compilation
11085 environment. Using GNAT, the current directory, possibly containing a
11086 @file{gnat.adc} file is the representation
11087 of a compilation environment. For more information on the
11088 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11090 Second, in compilation mode, if @code{gnatchop}
11091 is given a file that starts with
11092 configuration pragmas, and contains one or more units, then these
11093 configuration pragmas are prepended to each of the chopped files. This
11094 behavior provides the required behavior described in the RM for the
11095 actions to be taken on compiling such a file, namely that the pragmas
11096 apply to all units in the compilation, but not to subsequently compiled
11099 Finally, if configuration pragmas appear between units, they are appended
11100 to the previous unit. This results in the previous unit being illegal,
11101 since the compiler does not accept configuration pragmas that follow
11102 a unit. This provides the required RM behavior that forbids configuration
11103 pragmas other than those preceding the first compilation unit of a
11106 For most purposes, @code{gnatchop} will be used in default mode. The
11107 compilation mode described above is used only if you need exactly
11108 accurate behavior with respect to compilations, and you have files
11109 that contain multiple units and configuration pragmas. In this
11110 circumstance the use of @code{gnatchop} with the compilation mode
11111 switch provides the required behavior, and is for example the mode
11112 in which GNAT processes the ACVC tests.
11114 @node Command Line for gnatchop
11115 @section Command Line for @code{gnatchop}
11118 The @code{gnatchop} command has the form:
11121 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11126 The only required argument is the file name of the file to be chopped.
11127 There are no restrictions on the form of this file name. The file itself
11128 contains one or more Ada units, in normal GNAT format, concatenated
11129 together. As shown, more than one file may be presented to be chopped.
11131 When run in default mode, @code{gnatchop} generates one output file in
11132 the current directory for each unit in each of the files.
11134 @var{directory}, if specified, gives the name of the directory to which
11135 the output files will be written. If it is not specified, all files are
11136 written to the current directory.
11138 For example, given a
11139 file called @file{hellofiles} containing
11141 @smallexample @c ada
11146 with Text_IO; use Text_IO;
11149 Put_Line ("Hello");
11159 $ gnatchop ^hellofiles^HELLOFILES.^
11163 generates two files in the current directory, one called
11164 @file{hello.ads} containing the single line that is the procedure spec,
11165 and the other called @file{hello.adb} containing the remaining text. The
11166 original file is not affected. The generated files can be compiled in
11170 When gnatchop is invoked on a file that is empty or that contains only empty
11171 lines and/or comments, gnatchop will not fail, but will not produce any
11174 For example, given a
11175 file called @file{toto.txt} containing
11177 @smallexample @c ada
11189 $ gnatchop ^toto.txt^TOT.TXT^
11193 will not produce any new file and will result in the following warnings:
11196 toto.txt:1:01: warning: empty file, contains no compilation units
11197 no compilation units found
11198 no source files written
11201 @node Switches for gnatchop
11202 @section Switches for @code{gnatchop}
11205 @command{gnatchop} recognizes the following switches:
11211 @cindex @option{--version} @command{gnatchop}
11212 Display Copyright and version, then exit disregarding all other options.
11215 @cindex @option{--help} @command{gnatchop}
11216 If @option{--version} was not used, display usage, then exit disregarding
11219 @item ^-c^/COMPILATION^
11220 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11221 Causes @code{gnatchop} to operate in compilation mode, in which
11222 configuration pragmas are handled according to strict RM rules. See
11223 previous section for a full description of this mode.
11226 @item -gnat@var{xxx}
11227 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11228 used to parse the given file. Not all @var{xxx} options make sense,
11229 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11230 process a source file that uses Latin-2 coding for identifiers.
11234 Causes @code{gnatchop} to generate a brief help summary to the standard
11235 output file showing usage information.
11237 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11238 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11239 Limit generated file names to the specified number @code{mm}
11241 This is useful if the
11242 resulting set of files is required to be interoperable with systems
11243 which limit the length of file names.
11245 If no value is given, or
11246 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11247 a default of 39, suitable for OpenVMS Alpha
11248 Systems, is assumed
11251 No space is allowed between the @option{-k} and the numeric value. The numeric
11252 value may be omitted in which case a default of @option{-k8},
11254 with DOS-like file systems, is used. If no @option{-k} switch
11256 there is no limit on the length of file names.
11259 @item ^-p^/PRESERVE^
11260 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11261 Causes the file ^modification^creation^ time stamp of the input file to be
11262 preserved and used for the time stamp of the output file(s). This may be
11263 useful for preserving coherency of time stamps in an environment where
11264 @code{gnatchop} is used as part of a standard build process.
11267 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11268 Causes output of informational messages indicating the set of generated
11269 files to be suppressed. Warnings and error messages are unaffected.
11271 @item ^-r^/REFERENCE^
11272 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11273 @findex Source_Reference
11274 Generate @code{Source_Reference} pragmas. Use this switch if the output
11275 files are regarded as temporary and development is to be done in terms
11276 of the original unchopped file. This switch causes
11277 @code{Source_Reference} pragmas to be inserted into each of the
11278 generated files to refers back to the original file name and line number.
11279 The result is that all error messages refer back to the original
11281 In addition, the debugging information placed into the object file (when
11282 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11284 also refers back to this original file so that tools like profilers and
11285 debuggers will give information in terms of the original unchopped file.
11287 If the original file to be chopped itself contains
11288 a @code{Source_Reference}
11289 pragma referencing a third file, then gnatchop respects
11290 this pragma, and the generated @code{Source_Reference} pragmas
11291 in the chopped file refer to the original file, with appropriate
11292 line numbers. This is particularly useful when @code{gnatchop}
11293 is used in conjunction with @code{gnatprep} to compile files that
11294 contain preprocessing statements and multiple units.
11296 @item ^-v^/VERBOSE^
11297 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11298 Causes @code{gnatchop} to operate in verbose mode. The version
11299 number and copyright notice are output, as well as exact copies of
11300 the gnat1 commands spawned to obtain the chop control information.
11302 @item ^-w^/OVERWRITE^
11303 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11304 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11305 fatal error if there is already a file with the same name as a
11306 file it would otherwise output, in other words if the files to be
11307 chopped contain duplicated units. This switch bypasses this
11308 check, and causes all but the last instance of such duplicated
11309 units to be skipped.
11312 @item --GCC=@var{xxxx}
11313 @cindex @option{--GCC=} (@code{gnatchop})
11314 Specify the path of the GNAT parser to be used. When this switch is used,
11315 no attempt is made to add the prefix to the GNAT parser executable.
11319 @node Examples of gnatchop Usage
11320 @section Examples of @code{gnatchop} Usage
11324 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11327 @item gnatchop -w hello_s.ada prerelease/files
11330 Chops the source file @file{hello_s.ada}. The output files will be
11331 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11333 files with matching names in that directory (no files in the current
11334 directory are modified).
11336 @item gnatchop ^archive^ARCHIVE.^
11337 Chops the source file @file{^archive^ARCHIVE.^}
11338 into the current directory. One
11339 useful application of @code{gnatchop} is in sending sets of sources
11340 around, for example in email messages. The required sources are simply
11341 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11343 @command{gnatchop} is used at the other end to reconstitute the original
11346 @item gnatchop file1 file2 file3 direc
11347 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11348 the resulting files in the directory @file{direc}. Note that if any units
11349 occur more than once anywhere within this set of files, an error message
11350 is generated, and no files are written. To override this check, use the
11351 @option{^-w^/OVERWRITE^} switch,
11352 in which case the last occurrence in the last file will
11353 be the one that is output, and earlier duplicate occurrences for a given
11354 unit will be skipped.
11357 @node Configuration Pragmas
11358 @chapter Configuration Pragmas
11359 @cindex Configuration pragmas
11360 @cindex Pragmas, configuration
11363 Configuration pragmas include those pragmas described as
11364 such in the Ada Reference Manual, as well as
11365 implementation-dependent pragmas that are configuration pragmas.
11366 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11367 for details on these additional GNAT-specific configuration pragmas.
11368 Most notably, the pragma @code{Source_File_Name}, which allows
11369 specifying non-default names for source files, is a configuration
11370 pragma. The following is a complete list of configuration pragmas
11371 recognized by GNAT:
11379 Assume_No_Invalid_Values
11384 Compile_Time_Warning
11386 Component_Alignment
11387 Convention_Identifier
11395 External_Name_Casing
11398 Float_Representation
11411 Priority_Specific_Dispatching
11414 Propagate_Exceptions
11417 Restricted_Run_Time
11419 Restrictions_Warnings
11422 Source_File_Name_Project
11425 Suppress_Exception_Locations
11426 Task_Dispatching_Policy
11432 Wide_Character_Encoding
11437 * Handling of Configuration Pragmas::
11438 * The Configuration Pragmas Files::
11441 @node Handling of Configuration Pragmas
11442 @section Handling of Configuration Pragmas
11444 Configuration pragmas may either appear at the start of a compilation
11445 unit, in which case they apply only to that unit, or they may apply to
11446 all compilations performed in a given compilation environment.
11448 GNAT also provides the @code{gnatchop} utility to provide an automatic
11449 way to handle configuration pragmas following the semantics for
11450 compilations (that is, files with multiple units), described in the RM.
11451 See @ref{Operating gnatchop in Compilation Mode} for details.
11452 However, for most purposes, it will be more convenient to edit the
11453 @file{gnat.adc} file that contains configuration pragmas directly,
11454 as described in the following section.
11456 @node The Configuration Pragmas Files
11457 @section The Configuration Pragmas Files
11458 @cindex @file{gnat.adc}
11461 In GNAT a compilation environment is defined by the current
11462 directory at the time that a compile command is given. This current
11463 directory is searched for a file whose name is @file{gnat.adc}. If
11464 this file is present, it is expected to contain one or more
11465 configuration pragmas that will be applied to the current compilation.
11466 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11469 Configuration pragmas may be entered into the @file{gnat.adc} file
11470 either by running @code{gnatchop} on a source file that consists only of
11471 configuration pragmas, or more conveniently by
11472 direct editing of the @file{gnat.adc} file, which is a standard format
11475 In addition to @file{gnat.adc}, additional files containing configuration
11476 pragmas may be applied to the current compilation using the switch
11477 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11478 contains only configuration pragmas. These configuration pragmas are
11479 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11480 is present and switch @option{-gnatA} is not used).
11482 It is allowed to specify several switches @option{-gnatec}, all of which
11483 will be taken into account.
11485 If you are using project file, a separate mechanism is provided using
11486 project attributes, see @ref{Specifying Configuration Pragmas} for more
11490 Of special interest to GNAT OpenVMS Alpha is the following
11491 configuration pragma:
11493 @smallexample @c ada
11495 pragma Extend_System (Aux_DEC);
11500 In the presence of this pragma, GNAT adds to the definition of the
11501 predefined package SYSTEM all the additional types and subprograms that are
11502 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11505 @node Handling Arbitrary File Naming Conventions Using gnatname
11506 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11507 @cindex Arbitrary File Naming Conventions
11510 * Arbitrary File Naming Conventions::
11511 * Running gnatname::
11512 * Switches for gnatname::
11513 * Examples of gnatname Usage::
11516 @node Arbitrary File Naming Conventions
11517 @section Arbitrary File Naming Conventions
11520 The GNAT compiler must be able to know the source file name of a compilation
11521 unit. When using the standard GNAT default file naming conventions
11522 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11523 does not need additional information.
11526 When the source file names do not follow the standard GNAT default file naming
11527 conventions, the GNAT compiler must be given additional information through
11528 a configuration pragmas file (@pxref{Configuration Pragmas})
11530 When the non-standard file naming conventions are well-defined,
11531 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11532 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11533 if the file naming conventions are irregular or arbitrary, a number
11534 of pragma @code{Source_File_Name} for individual compilation units
11536 To help maintain the correspondence between compilation unit names and
11537 source file names within the compiler,
11538 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11541 @node Running gnatname
11542 @section Running @code{gnatname}
11545 The usual form of the @code{gnatname} command is
11548 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11549 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11553 All of the arguments are optional. If invoked without any argument,
11554 @code{gnatname} will display its usage.
11557 When used with at least one naming pattern, @code{gnatname} will attempt to
11558 find all the compilation units in files that follow at least one of the
11559 naming patterns. To find these compilation units,
11560 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11564 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11565 Each Naming Pattern is enclosed between double quotes.
11566 A Naming Pattern is a regular expression similar to the wildcard patterns
11567 used in file names by the Unix shells or the DOS prompt.
11570 @code{gnatname} may be called with several sections of directories/patterns.
11571 Sections are separated by switch @code{--and}. In each section, there must be
11572 at least one pattern. If no directory is specified in a section, the current
11573 directory (or the project directory is @code{-P} is used) is implied.
11574 The options other that the directory switches and the patterns apply globally
11575 even if they are in different sections.
11578 Examples of Naming Patterns are
11587 For a more complete description of the syntax of Naming Patterns,
11588 see the second kind of regular expressions described in @file{g-regexp.ads}
11589 (the ``Glob'' regular expressions).
11592 When invoked with no switch @code{-P}, @code{gnatname} will create a
11593 configuration pragmas file @file{gnat.adc} in the current working directory,
11594 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11597 @node Switches for gnatname
11598 @section Switches for @code{gnatname}
11601 Switches for @code{gnatname} must precede any specified Naming Pattern.
11604 You may specify any of the following switches to @code{gnatname}:
11610 @cindex @option{--version} @command{gnatname}
11611 Display Copyright and version, then exit disregarding all other options.
11614 @cindex @option{--help} @command{gnatname}
11615 If @option{--version} was not used, display usage, then exit disregarding
11619 Start another section of directories/patterns.
11621 @item ^-c^/CONFIG_FILE=^@file{file}
11622 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11623 Create a configuration pragmas file @file{file} (instead of the default
11626 There may be zero, one or more space between @option{-c} and
11629 @file{file} may include directory information. @file{file} must be
11630 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11631 When a switch @option{^-c^/CONFIG_FILE^} is
11632 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11634 @item ^-d^/SOURCE_DIRS=^@file{dir}
11635 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11636 Look for source files in directory @file{dir}. There may be zero, one or more
11637 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11638 When a switch @option{^-d^/SOURCE_DIRS^}
11639 is specified, the current working directory will not be searched for source
11640 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11641 or @option{^-D^/DIR_FILES^} switch.
11642 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11643 If @file{dir} is a relative path, it is relative to the directory of
11644 the configuration pragmas file specified with switch
11645 @option{^-c^/CONFIG_FILE^},
11646 or to the directory of the project file specified with switch
11647 @option{^-P^/PROJECT_FILE^} or,
11648 if neither switch @option{^-c^/CONFIG_FILE^}
11649 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11650 current working directory. The directory
11651 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11653 @item ^-D^/DIRS_FILE=^@file{file}
11654 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11655 Look for source files in all directories listed in text file @file{file}.
11656 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11658 @file{file} must be an existing, readable text file.
11659 Each nonempty line in @file{file} must be a directory.
11660 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11661 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11664 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11665 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11666 Foreign patterns. Using this switch, it is possible to add sources of languages
11667 other than Ada to the list of sources of a project file.
11668 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11671 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11674 will look for Ada units in all files with the @file{.ada} extension,
11675 and will add to the list of file for project @file{prj.gpr} the C files
11676 with extension @file{.^c^C^}.
11679 @cindex @option{^-h^/HELP^} (@code{gnatname})
11680 Output usage (help) information. The output is written to @file{stdout}.
11682 @item ^-P^/PROJECT_FILE=^@file{proj}
11683 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11684 Create or update project file @file{proj}. There may be zero, one or more space
11685 between @option{-P} and @file{proj}. @file{proj} may include directory
11686 information. @file{proj} must be writable.
11687 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11688 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11689 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11691 @item ^-v^/VERBOSE^
11692 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11693 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11694 This includes name of the file written, the name of the directories to search
11695 and, for each file in those directories whose name matches at least one of
11696 the Naming Patterns, an indication of whether the file contains a unit,
11697 and if so the name of the unit.
11699 @item ^-v -v^/VERBOSE /VERBOSE^
11700 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11701 Very Verbose mode. In addition to the output produced in verbose mode,
11702 for each file in the searched directories whose name matches none of
11703 the Naming Patterns, an indication is given that there is no match.
11705 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11706 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11707 Excluded patterns. Using this switch, it is possible to exclude some files
11708 that would match the name patterns. For example,
11710 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11713 will look for Ada units in all files with the @file{.ada} extension,
11714 except those whose names end with @file{_nt.ada}.
11718 @node Examples of gnatname Usage
11719 @section Examples of @code{gnatname} Usage
11723 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11729 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11734 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11735 and be writable. In addition, the directory
11736 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11737 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11740 Note the optional spaces after @option{-c} and @option{-d}.
11745 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11746 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11749 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11750 /EXCLUDED_PATTERN=*_nt_body.ada
11751 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11752 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11756 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11757 even in conjunction with one or several switches
11758 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11759 are used in this example.
11761 @c *****************************************
11762 @c * G N A T P r o j e c t M a n a g e r *
11763 @c *****************************************
11764 @node GNAT Project Manager
11765 @chapter GNAT Project Manager
11769 * Examples of Project Files::
11770 * Project File Syntax::
11771 * Objects and Sources in Project Files::
11772 * Importing Projects::
11773 * Project Extension::
11774 * Project Hierarchy Extension::
11775 * External References in Project Files::
11776 * Packages in Project Files::
11777 * Variables from Imported Projects::
11779 * Library Projects::
11780 * Stand-alone Library Projects::
11781 * Switches Related to Project Files::
11782 * Tools Supporting Project Files::
11783 * An Extended Example::
11784 * Project File Complete Syntax::
11787 @c ****************
11788 @c * Introduction *
11789 @c ****************
11792 @section Introduction
11795 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11796 you to manage complex builds involving a number of source files, directories,
11797 and compilation options for different system configurations. In particular,
11798 project files allow you to specify:
11801 The directory or set of directories containing the source files, and/or the
11802 names of the specific source files themselves
11804 The directory in which the compiler's output
11805 (@file{ALI} files, object files, tree files) is to be placed
11807 The directory in which the executable programs is to be placed
11809 ^Switch^Switch^ settings for any of the project-enabled tools
11810 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11811 @code{gnatfind}); you can apply these settings either globally or to individual
11814 The source files containing the main subprogram(s) to be built
11816 The source programming language(s) (currently Ada and/or C)
11818 Source file naming conventions; you can specify these either globally or for
11819 individual compilation units
11826 @node Project Files
11827 @subsection Project Files
11830 Project files are written in a syntax close to that of Ada, using familiar
11831 notions such as packages, context clauses, declarations, default values,
11832 assignments, and inheritance. Finally, project files can be built
11833 hierarchically from other project files, simplifying complex system
11834 integration and project reuse.
11836 A @dfn{project} is a specific set of values for various compilation properties.
11837 The settings for a given project are described by means of
11838 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11839 Property values in project files are either strings or lists of strings.
11840 Properties that are not explicitly set receive default values. A project
11841 file may interrogate the values of @dfn{external variables} (user-defined
11842 command-line switches or environment variables), and it may specify property
11843 settings conditionally, based on the value of such variables.
11845 In simple cases, a project's source files depend only on other source files
11846 in the same project, or on the predefined libraries. (@emph{Dependence} is
11848 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11849 the Project Manager also allows more sophisticated arrangements,
11850 where the source files in one project depend on source files in other
11854 One project can @emph{import} other projects containing needed source files.
11856 You can organize GNAT projects in a hierarchy: a @emph{child} project
11857 can extend a @emph{parent} project, inheriting the parent's source files and
11858 optionally overriding any of them with alternative versions
11862 More generally, the Project Manager lets you structure large development
11863 efforts into hierarchical subsystems, where build decisions are delegated
11864 to the subsystem level, and thus different compilation environments
11865 (^switch^switch^ settings) used for different subsystems.
11867 The Project Manager is invoked through the
11868 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11869 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11871 There may be zero, one or more spaces between @option{-P} and
11872 @option{@emph{projectfile}}.
11874 If you want to define (on the command line) an external variable that is
11875 queried by the project file, you must use the
11876 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11877 The Project Manager parses and interprets the project file, and drives the
11878 invoked tool based on the project settings.
11880 The Project Manager supports a wide range of development strategies,
11881 for systems of all sizes. Here are some typical practices that are
11885 Using a common set of source files, but generating object files in different
11886 directories via different ^switch^switch^ settings
11888 Using a mostly-shared set of source files, but with different versions of
11893 The destination of an executable can be controlled inside a project file
11894 using the @option{^-o^-o^}
11896 In the absence of such a ^switch^switch^ either inside
11897 the project file or on the command line, any executable files generated by
11898 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11899 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11900 in the object directory of the project.
11902 You can use project files to achieve some of the effects of a source
11903 versioning system (for example, defining separate projects for
11904 the different sets of sources that comprise different releases) but the
11905 Project Manager is independent of any source configuration management tools
11906 that might be used by the developers.
11908 The next section introduces the main features of GNAT's project facility
11909 through a sequence of examples; subsequent sections will present the syntax
11910 and semantics in more detail. A more formal description of the project
11911 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11914 @c *****************************
11915 @c * Examples of Project Files *
11916 @c *****************************
11918 @node Examples of Project Files
11919 @section Examples of Project Files
11921 This section illustrates some of the typical uses of project files and
11922 explains their basic structure and behavior.
11925 * Common Sources with Different ^Switches^Switches^ and Directories::
11926 * Using External Variables::
11927 * Importing Other Projects::
11928 * Extending a Project::
11931 @node Common Sources with Different ^Switches^Switches^ and Directories
11932 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11936 * Specifying the Object Directory::
11937 * Specifying the Exec Directory::
11938 * Project File Packages::
11939 * Specifying ^Switch^Switch^ Settings::
11940 * Main Subprograms::
11941 * Executable File Names::
11942 * Source File Naming Conventions::
11943 * Source Language(s)::
11947 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11948 @file{proc.adb} are in the @file{/common} directory. The file
11949 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11950 package @code{Pack}. We want to compile these source files under two sets
11951 of ^switches^switches^:
11954 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11955 and the @option{^-gnata^-gnata^},
11956 @option{^-gnato^-gnato^},
11957 and @option{^-gnatE^-gnatE^} switches to the
11958 compiler; the compiler's output is to appear in @file{/common/debug}
11960 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11961 to the compiler; the compiler's output is to appear in @file{/common/release}
11965 The GNAT project files shown below, respectively @file{debug.gpr} and
11966 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11979 ^/common/debug^[COMMON.DEBUG]^
11984 ^/common/release^[COMMON.RELEASE]^
11989 Here are the corresponding project files:
11991 @smallexample @c projectfile
11994 for Object_Dir use "debug";
11995 for Main use ("proc");
11998 for ^Default_Switches^Default_Switches^ ("Ada")
12000 for Executable ("proc.adb") use "proc1";
12005 package Compiler is
12006 for ^Default_Switches^Default_Switches^ ("Ada")
12007 use ("-fstack-check",
12010 "^-gnatE^-gnatE^");
12016 @smallexample @c projectfile
12019 for Object_Dir use "release";
12020 for Exec_Dir use ".";
12021 for Main use ("proc");
12023 package Compiler is
12024 for ^Default_Switches^Default_Switches^ ("Ada")
12032 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
12033 insensitive), and analogously the project defined by @file{release.gpr} is
12034 @code{"Release"}. For consistency the file should have the same name as the
12035 project, and the project file's extension should be @code{"gpr"}. These
12036 conventions are not required, but a warning is issued if they are not followed.
12038 If the current directory is @file{^/temp^[TEMP]^}, then the command
12040 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
12044 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
12045 as well as the @code{^proc1^PROC1.EXE^} executable,
12046 using the ^switch^switch^ settings defined in the project file.
12048 Likewise, the command
12050 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
12054 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
12055 and the @code{^proc^PROC.EXE^}
12056 executable in @file{^/common^[COMMON]^},
12057 using the ^switch^switch^ settings from the project file.
12060 @unnumberedsubsubsec Source Files
12063 If a project file does not explicitly specify a set of source directories or
12064 a set of source files, then by default the project's source files are the
12065 Ada source files in the project file directory. Thus @file{pack.ads},
12066 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
12068 @node Specifying the Object Directory
12069 @unnumberedsubsubsec Specifying the Object Directory
12072 Several project properties are modeled by Ada-style @emph{attributes};
12073 a property is defined by supplying the equivalent of an Ada attribute
12074 definition clause in the project file.
12075 A project's object directory is another such a property; the corresponding
12076 attribute is @code{Object_Dir}, and its value is also a string expression,
12077 specified either as absolute or relative. In the later case,
12078 it is relative to the project file directory. Thus the compiler's
12079 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
12080 (for the @code{Debug} project)
12081 and to @file{^/common/release^[COMMON.RELEASE]^}
12082 (for the @code{Release} project).
12083 If @code{Object_Dir} is not specified, then the default is the project file
12086 @node Specifying the Exec Directory
12087 @unnumberedsubsubsec Specifying the Exec Directory
12090 A project's exec directory is another property; the corresponding
12091 attribute is @code{Exec_Dir}, and its value is also a string expression,
12092 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12093 then the default is the object directory (which may also be the project file
12094 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12095 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12096 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12097 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12099 @node Project File Packages
12100 @unnumberedsubsubsec Project File Packages
12103 A GNAT tool that is integrated with the Project Manager is modeled by a
12104 corresponding package in the project file. In the example above,
12105 The @code{Debug} project defines the packages @code{Builder}
12106 (for @command{gnatmake}) and @code{Compiler};
12107 the @code{Release} project defines only the @code{Compiler} package.
12109 The Ada-like package syntax is not to be taken literally. Although packages in
12110 project files bear a surface resemblance to packages in Ada source code, the
12111 notation is simply a way to convey a grouping of properties for a named
12112 entity. Indeed, the package names permitted in project files are restricted
12113 to a predefined set, corresponding to the project-aware tools, and the contents
12114 of packages are limited to a small set of constructs.
12115 The packages in the example above contain attribute definitions.
12117 @node Specifying ^Switch^Switch^ Settings
12118 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12121 ^Switch^Switch^ settings for a project-aware tool can be specified through
12122 attributes in the package that corresponds to the tool.
12123 The example above illustrates one of the relevant attributes,
12124 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12125 in both project files.
12126 Unlike simple attributes like @code{Source_Dirs},
12127 @code{^Default_Switches^Default_Switches^} is
12128 known as an @emph{associative array}. When you define this attribute, you must
12129 supply an ``index'' (a literal string), and the effect of the attribute
12130 definition is to set the value of the array at the specified index.
12131 For the @code{^Default_Switches^Default_Switches^} attribute,
12132 the index is a programming language (in our case, Ada),
12133 and the value specified (after @code{use}) must be a list
12134 of string expressions.
12136 The attributes permitted in project files are restricted to a predefined set.
12137 Some may appear at project level, others in packages.
12138 For any attribute that is an associative array, the index must always be a
12139 literal string, but the restrictions on this string (e.g., a file name or a
12140 language name) depend on the individual attribute.
12141 Also depending on the attribute, its specified value will need to be either a
12142 string or a string list.
12144 In the @code{Debug} project, we set the switches for two tools,
12145 @command{gnatmake} and the compiler, and thus we include the two corresponding
12146 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12147 attribute with index @code{"Ada"}.
12148 Note that the package corresponding to
12149 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12150 similar, but only includes the @code{Compiler} package.
12152 In project @code{Debug} above, the ^switches^switches^ starting with
12153 @option{-gnat} that are specified in package @code{Compiler}
12154 could have been placed in package @code{Builder}, since @command{gnatmake}
12155 transmits all such ^switches^switches^ to the compiler.
12157 @node Main Subprograms
12158 @unnumberedsubsubsec Main Subprograms
12161 One of the specifiable properties of a project is a list of files that contain
12162 main subprograms. This property is captured in the @code{Main} attribute,
12163 whose value is a list of strings. If a project defines the @code{Main}
12164 attribute, it is not necessary to identify the main subprogram(s) when
12165 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12167 @node Executable File Names
12168 @unnumberedsubsubsec Executable File Names
12171 By default, the executable file name corresponding to a main source is
12172 deduced from the main source file name. Through the attributes
12173 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12174 it is possible to change this default.
12175 In project @code{Debug} above, the executable file name
12176 for main source @file{^proc.adb^PROC.ADB^} is
12177 @file{^proc1^PROC1.EXE^}.
12178 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12179 of the executable files, when no attribute @code{Executable} applies:
12180 its value replace the platform-specific executable suffix.
12181 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12182 specify a non-default executable file name when several mains are built at once
12183 in a single @command{gnatmake} command.
12185 @node Source File Naming Conventions
12186 @unnumberedsubsubsec Source File Naming Conventions
12189 Since the project files above do not specify any source file naming
12190 conventions, the GNAT defaults are used. The mechanism for defining source
12191 file naming conventions -- a package named @code{Naming} --
12192 is described below (@pxref{Naming Schemes}).
12194 @node Source Language(s)
12195 @unnumberedsubsubsec Source Language(s)
12198 Since the project files do not specify a @code{Languages} attribute, by
12199 default the GNAT tools assume that the language of the project file is Ada.
12200 More generally, a project can comprise source files
12201 in Ada, C, and/or other languages.
12203 @node Using External Variables
12204 @subsection Using External Variables
12207 Instead of supplying different project files for debug and release, we can
12208 define a single project file that queries an external variable (set either
12209 on the command line or via an ^environment variable^logical name^) in order to
12210 conditionally define the appropriate settings. Again, assume that the
12211 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12212 located in directory @file{^/common^[COMMON]^}. The following project file,
12213 @file{build.gpr}, queries the external variable named @code{STYLE} and
12214 defines an object directory and ^switch^switch^ settings based on whether
12215 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12216 the default is @code{"deb"}.
12218 @smallexample @c projectfile
12221 for Main use ("proc");
12223 type Style_Type is ("deb", "rel");
12224 Style : Style_Type := external ("STYLE", "deb");
12228 for Object_Dir use "debug";
12231 for Object_Dir use "release";
12232 for Exec_Dir use ".";
12241 for ^Default_Switches^Default_Switches^ ("Ada")
12243 for Executable ("proc") use "proc1";
12252 package Compiler is
12256 for ^Default_Switches^Default_Switches^ ("Ada")
12257 use ("^-gnata^-gnata^",
12259 "^-gnatE^-gnatE^");
12262 for ^Default_Switches^Default_Switches^ ("Ada")
12273 @code{Style_Type} is an example of a @emph{string type}, which is the project
12274 file analog of an Ada enumeration type but whose components are string literals
12275 rather than identifiers. @code{Style} is declared as a variable of this type.
12277 The form @code{external("STYLE", "deb")} is known as an
12278 @emph{external reference}; its first argument is the name of an
12279 @emph{external variable}, and the second argument is a default value to be
12280 used if the external variable doesn't exist. You can define an external
12281 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12282 or you can use ^an environment variable^a logical name^
12283 as an external variable.
12285 Each @code{case} construct is expanded by the Project Manager based on the
12286 value of @code{Style}. Thus the command
12289 gnatmake -P/common/build.gpr -XSTYLE=deb
12295 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12300 is equivalent to the @command{gnatmake} invocation using the project file
12301 @file{debug.gpr} in the earlier example. So is the command
12303 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12307 since @code{"deb"} is the default for @code{STYLE}.
12313 gnatmake -P/common/build.gpr -XSTYLE=rel
12319 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12324 is equivalent to the @command{gnatmake} invocation using the project file
12325 @file{release.gpr} in the earlier example.
12327 @node Importing Other Projects
12328 @subsection Importing Other Projects
12329 @cindex @code{ADA_PROJECT_PATH}
12330 @cindex @code{GPR_PROJECT_PATH}
12333 A compilation unit in a source file in one project may depend on compilation
12334 units in source files in other projects. To compile this unit under
12335 control of a project file, the
12336 dependent project must @emph{import} the projects containing the needed source
12338 This effect is obtained using syntax similar to an Ada @code{with} clause,
12339 but where @code{with}ed entities are strings that denote project files.
12341 As an example, suppose that the two projects @code{GUI_Proj} and
12342 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12343 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12344 and @file{^/comm^[COMM]^}, respectively.
12345 Suppose that the source files for @code{GUI_Proj} are
12346 @file{gui.ads} and @file{gui.adb}, and that the source files for
12347 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12348 files is located in its respective project file directory. Schematically:
12367 We want to develop an application in directory @file{^/app^[APP]^} that
12368 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12369 the corresponding project files (e.g.@: the ^switch^switch^ settings
12370 and object directory).
12371 Skeletal code for a main procedure might be something like the following:
12373 @smallexample @c ada
12376 procedure App_Main is
12385 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12388 @smallexample @c projectfile
12390 with "/gui/gui_proj", "/comm/comm_proj";
12391 project App_Proj is
12392 for Main use ("app_main");
12398 Building an executable is achieved through the command:
12400 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12403 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12404 in the directory where @file{app_proj.gpr} resides.
12406 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12407 (as illustrated above) the @code{with} clause can omit the extension.
12409 Our example specified an absolute path for each imported project file.
12410 Alternatively, the directory name of an imported object can be omitted
12414 The imported project file is in the same directory as the importing project
12417 You have defined one or two ^environment variables^logical names^
12418 that includes the directory containing
12419 the needed project file. The syntax of @code{GPR_PROJECT_PATH} and
12420 @code{ADA_PROJECT_PATH} is the same as
12421 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12422 directory names separated by colons (semicolons on Windows).
12426 Thus, if we define @code{ADA_PROJECT_PATH} or @code{GPR_PROJECT_PATH}
12427 to include @file{^/gui^[GUI]^} and
12428 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12431 @smallexample @c projectfile
12433 with "gui_proj", "comm_proj";
12434 project App_Proj is
12435 for Main use ("app_main");
12441 Importing other projects can create ambiguities.
12442 For example, the same unit might be present in different imported projects, or
12443 it might be present in both the importing project and in an imported project.
12444 Both of these conditions are errors. Note that in the current version of
12445 the Project Manager, it is illegal to have an ambiguous unit even if the
12446 unit is never referenced by the importing project. This restriction may be
12447 relaxed in a future release.
12449 @node Extending a Project
12450 @subsection Extending a Project
12453 In large software systems it is common to have multiple
12454 implementations of a common interface; in Ada terms, multiple versions of a
12455 package body for the same spec. For example, one implementation
12456 might be safe for use in tasking programs, while another might only be used
12457 in sequential applications. This can be modeled in GNAT using the concept
12458 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12459 another project (the ``parent'') then by default all source files of the
12460 parent project are inherited by the child, but the child project can
12461 override any of the parent's source files with new versions, and can also
12462 add new files. This facility is the project analog of a type extension in
12463 Object-Oriented Programming. Project hierarchies are permitted (a child
12464 project may be the parent of yet another project), and a project that
12465 inherits one project can also import other projects.
12467 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12468 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12469 @file{pack.adb}, and @file{proc.adb}:
12482 Note that the project file can simply be empty (that is, no attribute or
12483 package is defined):
12485 @smallexample @c projectfile
12487 project Seq_Proj is
12493 implying that its source files are all the Ada source files in the project
12496 Suppose we want to supply an alternate version of @file{pack.adb}, in
12497 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12498 @file{pack.ads} and @file{proc.adb}. We can define a project
12499 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12503 ^/tasking^[TASKING]^
12509 project Tasking_Proj extends "/seq/seq_proj" is
12515 The version of @file{pack.adb} used in a build depends on which project file
12518 Note that we could have obtained the desired behavior using project import
12519 rather than project inheritance; a @code{base} project would contain the
12520 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12521 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12522 would import @code{base} and add a different version of @file{pack.adb}. The
12523 choice depends on whether other sources in the original project need to be
12524 overridden. If they do, then project extension is necessary, otherwise,
12525 importing is sufficient.
12528 In a project file that extends another project file, it is possible to
12529 indicate that an inherited source is not part of the sources of the extending
12530 project. This is necessary sometimes when a package spec has been overloaded
12531 and no longer requires a body: in this case, it is necessary to indicate that
12532 the inherited body is not part of the sources of the project, otherwise there
12533 will be a compilation error when compiling the spec.
12535 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12536 Its value is a string list: a list of file names. It is also possible to use
12537 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12538 the file name of a text file containing a list of file names, one per line.
12540 @smallexample @c @projectfile
12541 project B extends "a" is
12542 for Source_Files use ("pkg.ads");
12543 -- New spec of Pkg does not need a completion
12544 for Excluded_Source_Files use ("pkg.adb");
12548 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12549 is still needed: if it is possible to build using @command{gnatmake} when such
12550 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12551 it is possible to remove the source completely from a system that includes
12554 @c ***********************
12555 @c * Project File Syntax *
12556 @c ***********************
12558 @node Project File Syntax
12559 @section Project File Syntax
12563 * Qualified Projects::
12569 * Associative Array Attributes::
12570 * case Constructions::
12574 This section describes the structure of project files.
12576 A project may be an @emph{independent project}, entirely defined by a single
12577 project file. Any Ada source file in an independent project depends only
12578 on the predefined library and other Ada source files in the same project.
12581 A project may also @dfn{depend on} other projects, in either or both of
12582 the following ways:
12584 @item It may import any number of projects
12585 @item It may extend at most one other project
12589 The dependence relation is a directed acyclic graph (the subgraph reflecting
12590 the ``extends'' relation is a tree).
12592 A project's @dfn{immediate sources} are the source files directly defined by
12593 that project, either implicitly by residing in the project file's directory,
12594 or explicitly through any of the source-related attributes described below.
12595 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12596 of @var{proj} together with the immediate sources (unless overridden) of any
12597 project on which @var{proj} depends (either directly or indirectly).
12600 @subsection Basic Syntax
12603 As seen in the earlier examples, project files have an Ada-like syntax.
12604 The minimal project file is:
12605 @smallexample @c projectfile
12614 The identifier @code{Empty} is the name of the project.
12615 This project name must be present after the reserved
12616 word @code{end} at the end of the project file, followed by a semi-colon.
12618 Any name in a project file, such as the project name or a variable name,
12619 has the same syntax as an Ada identifier.
12621 The reserved words of project files are the Ada 95 reserved words plus
12622 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12623 reserved words currently used in project file syntax are:
12659 Comments in project files have the same syntax as in Ada, two consecutive
12660 hyphens through the end of the line.
12662 @node Qualified Projects
12663 @subsection Qualified Projects
12666 Before the reserved @code{project}, there may be one or two "qualifiers", that
12667 is identifiers or other reserved words, to qualify the project.
12669 The current list of qualifiers is:
12673 @code{abstract}: qualify a project with no sources. A qualified abstract
12674 project must either have no declaration of attributes @code{Source_Dirs},
12675 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12676 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12677 as empty. If it extends another project, the project it extends must also be a
12678 qualified abstract project.
12681 @code{standard}: a standard project is a non library project with sources.
12684 @code{aggregate}: for future extension
12687 @code{aggregate library}: for future extension
12690 @code{library}: a library project must declare both attributes
12691 @code{Library_Name} and @code{Library_Dir}.
12694 @code{configuration}: a configuration project cannot be in a project tree.
12698 @subsection Packages
12701 A project file may contain @emph{packages}. The name of a package must be one
12702 of the identifiers from the following list. A package
12703 with a given name may only appear once in a project file. Package names are
12704 case insensitive. The following package names are legal:
12720 @code{Cross_Reference}
12724 @code{Pretty_Printer}
12734 @code{Language_Processing}
12738 In its simplest form, a package may be empty:
12740 @smallexample @c projectfile
12750 A package may contain @emph{attribute declarations},
12751 @emph{variable declarations} and @emph{case constructions}, as will be
12754 When there is ambiguity between a project name and a package name,
12755 the name always designates the project. To avoid possible confusion, it is
12756 always a good idea to avoid naming a project with one of the
12757 names allowed for packages or any name that starts with @code{gnat}.
12760 @subsection Expressions
12763 An @emph{expression} is either a @emph{string expression} or a
12764 @emph{string list expression}.
12766 A @emph{string expression} is either a @emph{simple string expression} or a
12767 @emph{compound string expression}.
12769 A @emph{simple string expression} is one of the following:
12771 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12772 @item A string-valued variable reference (@pxref{Variables})
12773 @item A string-valued attribute reference (@pxref{Attributes})
12774 @item An external reference (@pxref{External References in Project Files})
12778 A @emph{compound string expression} is a concatenation of string expressions,
12779 using the operator @code{"&"}
12781 Path & "/" & File_Name & ".ads"
12785 A @emph{string list expression} is either a
12786 @emph{simple string list expression} or a
12787 @emph{compound string list expression}.
12789 A @emph{simple string list expression} is one of the following:
12791 @item A parenthesized list of zero or more string expressions,
12792 separated by commas
12794 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12797 @item A string list-valued variable reference
12798 @item A string list-valued attribute reference
12802 A @emph{compound string list expression} is the concatenation (using
12803 @code{"&"}) of a simple string list expression and an expression. Note that
12804 each term in a compound string list expression, except the first, may be
12805 either a string expression or a string list expression.
12807 @smallexample @c projectfile
12809 File_Name_List := () & File_Name; -- One string in this list
12810 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12812 Big_List := File_Name_List & Extended_File_Name_List;
12813 -- Concatenation of two string lists: three strings
12814 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12815 -- Illegal: must start with a string list
12820 @subsection String Types
12823 A @emph{string type declaration} introduces a discrete set of string literals.
12824 If a string variable is declared to have this type, its value
12825 is restricted to the given set of literals.
12827 Here is an example of a string type declaration:
12829 @smallexample @c projectfile
12830 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12834 Variables of a string type are called @emph{typed variables}; all other
12835 variables are called @emph{untyped variables}. Typed variables are
12836 particularly useful in @code{case} constructions, to support conditional
12837 attribute declarations.
12838 (@pxref{case Constructions}).
12840 The string literals in the list are case sensitive and must all be different.
12841 They may include any graphic characters allowed in Ada, including spaces.
12843 A string type may only be declared at the project level, not inside a package.
12845 A string type may be referenced by its name if it has been declared in the same
12846 project file, or by an expanded name whose prefix is the name of the project
12847 in which it is declared.
12850 @subsection Variables
12853 A variable may be declared at the project file level, or within a package.
12854 Here are some examples of variable declarations:
12856 @smallexample @c projectfile
12858 This_OS : OS := external ("OS"); -- a typed variable declaration
12859 That_OS := "GNU/Linux"; -- an untyped variable declaration
12864 The syntax of a @emph{typed variable declaration} is identical to the Ada
12865 syntax for an object declaration. By contrast, the syntax of an untyped
12866 variable declaration is identical to an Ada assignment statement. In fact,
12867 variable declarations in project files have some of the characteristics of
12868 an assignment, in that successive declarations for the same variable are
12869 allowed. Untyped variable declarations do establish the expected kind of the
12870 variable (string or string list), and successive declarations for it must
12871 respect the initial kind.
12874 A string variable declaration (typed or untyped) declares a variable
12875 whose value is a string. This variable may be used as a string expression.
12876 @smallexample @c projectfile
12877 File_Name := "readme.txt";
12878 Saved_File_Name := File_Name & ".saved";
12882 A string list variable declaration declares a variable whose value is a list
12883 of strings. The list may contain any number (zero or more) of strings.
12885 @smallexample @c projectfile
12887 List_With_One_Element := ("^-gnaty^-gnaty^");
12888 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12889 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12890 "pack2.ada", "util_.ada", "util.ada");
12894 The same typed variable may not be declared more than once at project level,
12895 and it may not be declared more than once in any package; it is in effect
12898 The same untyped variable may be declared several times. Declarations are
12899 elaborated in the order in which they appear, so the new value replaces
12900 the old one, and any subsequent reference to the variable uses the new value.
12901 However, as noted above, if a variable has been declared as a string, all
12903 declarations must give it a string value. Similarly, if a variable has
12904 been declared as a string list, all subsequent declarations
12905 must give it a string list value.
12907 A @emph{variable reference} may take several forms:
12910 @item The simple variable name, for a variable in the current package (if any)
12911 or in the current project
12912 @item An expanded name, whose prefix is a context name.
12916 A @emph{context} may be one of the following:
12919 @item The name of an existing package in the current project
12920 @item The name of an imported project of the current project
12921 @item The name of an ancestor project (i.e., a project extended by the current
12922 project, either directly or indirectly)
12923 @item An expanded name whose prefix is an imported/parent project name, and
12924 whose selector is a package name in that project.
12928 A variable reference may be used in an expression.
12931 @subsection Attributes
12934 A project (and its packages) may have @emph{attributes} that define
12935 the project's properties. Some attributes have values that are strings;
12936 others have values that are string lists.
12938 There are two categories of attributes: @emph{simple attributes}
12939 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12941 Legal project attribute names, and attribute names for each legal package are
12942 listed below. Attributes names are case-insensitive.
12944 The following attributes are defined on projects (all are simple attributes):
12946 @multitable @columnfractions .4 .3
12947 @item @emph{Attribute Name}
12949 @item @code{Source_Files}
12951 @item @code{Source_Dirs}
12953 @item @code{Source_List_File}
12955 @item @code{Object_Dir}
12957 @item @code{Exec_Dir}
12959 @item @code{Excluded_Source_Dirs}
12961 @item @code{Excluded_Source_Files}
12963 @item @code{Excluded_Source_List_File}
12965 @item @code{Languages}
12969 @item @code{Library_Dir}
12971 @item @code{Library_Name}
12973 @item @code{Library_Kind}
12975 @item @code{Library_Version}
12977 @item @code{Library_Interface}
12979 @item @code{Library_Auto_Init}
12981 @item @code{Library_Options}
12983 @item @code{Library_Src_Dir}
12985 @item @code{Library_ALI_Dir}
12987 @item @code{Library_GCC}
12989 @item @code{Library_Symbol_File}
12991 @item @code{Library_Symbol_Policy}
12993 @item @code{Library_Reference_Symbol_File}
12995 @item @code{Externally_Built}
13000 The following attributes are defined for package @code{Naming}
13001 (@pxref{Naming Schemes}):
13003 @multitable @columnfractions .4 .2 .2 .2
13004 @item Attribute Name @tab Category @tab Index @tab Value
13005 @item @code{Spec_Suffix}
13006 @tab associative array
13009 @item @code{Body_Suffix}
13010 @tab associative array
13013 @item @code{Separate_Suffix}
13014 @tab simple attribute
13017 @item @code{Casing}
13018 @tab simple attribute
13021 @item @code{Dot_Replacement}
13022 @tab simple attribute
13026 @tab associative array
13030 @tab associative array
13033 @item @code{Specification_Exceptions}
13034 @tab associative array
13037 @item @code{Implementation_Exceptions}
13038 @tab associative array
13044 The following attributes are defined for packages @code{Builder},
13045 @code{Compiler}, @code{Binder},
13046 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
13047 (@pxref{^Switches^Switches^ and Project Files}).
13049 @multitable @columnfractions .4 .2 .2 .2
13050 @item Attribute Name @tab Category @tab Index @tab Value
13051 @item @code{^Default_Switches^Default_Switches^}
13052 @tab associative array
13055 @item @code{^Switches^Switches^}
13056 @tab associative array
13062 In addition, package @code{Compiler} has a single string attribute
13063 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
13064 string attribute @code{Global_Configuration_Pragmas}.
13067 Each simple attribute has a default value: the empty string (for string-valued
13068 attributes) and the empty list (for string list-valued attributes).
13070 An attribute declaration defines a new value for an attribute.
13072 Examples of simple attribute declarations:
13074 @smallexample @c projectfile
13075 for Object_Dir use "objects";
13076 for Source_Dirs use ("units", "test/drivers");
13080 The syntax of a @dfn{simple attribute declaration} is similar to that of an
13081 attribute definition clause in Ada.
13083 Attributes references may be appear in expressions.
13084 The general form for such a reference is @code{<entity>'<attribute>}:
13085 Associative array attributes are functions. Associative
13086 array attribute references must have an argument that is a string literal.
13090 @smallexample @c projectfile
13092 Naming'Dot_Replacement
13093 Imported_Project'Source_Dirs
13094 Imported_Project.Naming'Casing
13095 Builder'^Default_Switches^Default_Switches^("Ada")
13099 The prefix of an attribute may be:
13101 @item @code{project} for an attribute of the current project
13102 @item The name of an existing package of the current project
13103 @item The name of an imported project
13104 @item The name of a parent project that is extended by the current project
13105 @item An expanded name whose prefix is imported/parent project name,
13106 and whose selector is a package name
13111 @smallexample @c projectfile
13114 for Source_Dirs use project'Source_Dirs & "units";
13115 for Source_Dirs use project'Source_Dirs & "test/drivers"
13121 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13122 has the default value: an empty string list. After this declaration,
13123 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13124 After the second attribute declaration @code{Source_Dirs} is a string list of
13125 two elements: @code{"units"} and @code{"test/drivers"}.
13127 Note: this example is for illustration only. In practice,
13128 the project file would contain only one attribute declaration:
13130 @smallexample @c projectfile
13131 for Source_Dirs use ("units", "test/drivers");
13134 @node Associative Array Attributes
13135 @subsection Associative Array Attributes
13138 Some attributes are defined as @emph{associative arrays}. An associative
13139 array may be regarded as a function that takes a string as a parameter
13140 and delivers a string or string list value as its result.
13142 Here are some examples of single associative array attribute associations:
13144 @smallexample @c projectfile
13145 for Body ("main") use "Main.ada";
13146 for ^Switches^Switches^ ("main.ada")
13148 "^-gnatv^-gnatv^");
13149 for ^Switches^Switches^ ("main.ada")
13150 use Builder'^Switches^Switches^ ("main.ada")
13155 Like untyped variables and simple attributes, associative array attributes
13156 may be declared several times. Each declaration supplies a new value for the
13157 attribute, and replaces the previous setting.
13160 An associative array attribute may be declared as a full associative array
13161 declaration, with the value of the same attribute in an imported or extended
13164 @smallexample @c projectfile
13166 for Default_Switches use Default.Builder'Default_Switches;
13171 In this example, @code{Default} must be either a project imported by the
13172 current project, or the project that the current project extends. If the
13173 attribute is in a package (in this case, in package @code{Builder}), the same
13174 package needs to be specified.
13177 A full associative array declaration replaces any other declaration for the
13178 attribute, including other full associative array declaration. Single
13179 associative array associations may be declare after a full associative
13180 declaration, modifying the value for a single association of the attribute.
13182 @node case Constructions
13183 @subsection @code{case} Constructions
13186 A @code{case} construction is used in a project file to effect conditional
13188 Here is a typical example:
13190 @smallexample @c projectfile
13193 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13195 OS : OS_Type := external ("OS", "GNU/Linux");
13199 package Compiler is
13201 when "GNU/Linux" | "Unix" =>
13202 for ^Default_Switches^Default_Switches^ ("Ada")
13203 use ("^-gnath^-gnath^");
13205 for ^Default_Switches^Default_Switches^ ("Ada")
13206 use ("^-gnatP^-gnatP^");
13215 The syntax of a @code{case} construction is based on the Ada case statement
13216 (although there is no @code{null} construction for empty alternatives).
13218 The case expression must be a typed string variable.
13219 Each alternative comprises the reserved word @code{when}, either a list of
13220 literal strings separated by the @code{"|"} character or the reserved word
13221 @code{others}, and the @code{"=>"} token.
13222 Each literal string must belong to the string type that is the type of the
13224 An @code{others} alternative, if present, must occur last.
13226 After each @code{=>}, there are zero or more constructions. The only
13227 constructions allowed in a case construction are other case constructions,
13228 attribute declarations and variable declarations. String type declarations and
13229 package declarations are not allowed. Variable declarations are restricted to
13230 variables that have already been declared before the case construction.
13232 The value of the case variable is often given by an external reference
13233 (@pxref{External References in Project Files}).
13235 @c ****************************************
13236 @c * Objects and Sources in Project Files *
13237 @c ****************************************
13239 @node Objects and Sources in Project Files
13240 @section Objects and Sources in Project Files
13243 * Object Directory::
13245 * Source Directories::
13246 * Source File Names::
13250 Each project has exactly one object directory and one or more source
13251 directories. The source directories must contain at least one source file,
13252 unless the project file explicitly specifies that no source files are present
13253 (@pxref{Source File Names}).
13255 @node Object Directory
13256 @subsection Object Directory
13259 The object directory for a project is the directory containing the compiler's
13260 output (such as @file{ALI} files and object files) for the project's immediate
13263 The object directory is given by the value of the attribute @code{Object_Dir}
13264 in the project file.
13266 @smallexample @c projectfile
13267 for Object_Dir use "objects";
13271 The attribute @code{Object_Dir} has a string value, the path name of the object
13272 directory. The path name may be absolute or relative to the directory of the
13273 project file. This directory must already exist, and be readable and writable.
13275 By default, when the attribute @code{Object_Dir} is not given an explicit value
13276 or when its value is the empty string, the object directory is the same as the
13277 directory containing the project file.
13279 @node Exec Directory
13280 @subsection Exec Directory
13283 The exec directory for a project is the directory containing the executables
13284 for the project's main subprograms.
13286 The exec directory is given by the value of the attribute @code{Exec_Dir}
13287 in the project file.
13289 @smallexample @c projectfile
13290 for Exec_Dir use "executables";
13294 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13295 directory. The path name may be absolute or relative to the directory of the
13296 project file. This directory must already exist, and be writable.
13298 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13299 or when its value is the empty string, the exec directory is the same as the
13300 object directory of the project file.
13302 @node Source Directories
13303 @subsection Source Directories
13306 The source directories of a project are specified by the project file
13307 attribute @code{Source_Dirs}.
13309 This attribute's value is a string list. If the attribute is not given an
13310 explicit value, then there is only one source directory, the one where the
13311 project file resides.
13313 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13316 @smallexample @c projectfile
13317 for Source_Dirs use ();
13321 indicates that the project contains no source files.
13323 Otherwise, each string in the string list designates one or more
13324 source directories.
13326 @smallexample @c projectfile
13327 for Source_Dirs use ("sources", "test/drivers");
13331 If a string in the list ends with @code{"/**"}, then the directory whose path
13332 name precedes the two asterisks, as well as all its subdirectories
13333 (recursively), are source directories.
13335 @smallexample @c projectfile
13336 for Source_Dirs use ("/system/sources/**");
13340 Here the directory @code{/system/sources} and all of its subdirectories
13341 (recursively) are source directories.
13343 To specify that the source directories are the directory of the project file
13344 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13345 @smallexample @c projectfile
13346 for Source_Dirs use ("./**");
13350 Each of the source directories must exist and be readable.
13352 @node Source File Names
13353 @subsection Source File Names
13356 In a project that contains source files, their names may be specified by the
13357 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13358 (a string). Source file names never include any directory information.
13360 If the attribute @code{Source_Files} is given an explicit value, then each
13361 element of the list is a source file name.
13363 @smallexample @c projectfile
13364 for Source_Files use ("main.adb");
13365 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13369 If the attribute @code{Source_Files} is not given an explicit value,
13370 but the attribute @code{Source_List_File} is given a string value,
13371 then the source file names are contained in the text file whose path name
13372 (absolute or relative to the directory of the project file) is the
13373 value of the attribute @code{Source_List_File}.
13375 Each line in the file that is not empty or is not a comment
13376 contains a source file name.
13378 @smallexample @c projectfile
13379 for Source_List_File use "source_list.txt";
13383 By default, if neither the attribute @code{Source_Files} nor the attribute
13384 @code{Source_List_File} is given an explicit value, then each file in the
13385 source directories that conforms to the project's naming scheme
13386 (@pxref{Naming Schemes}) is an immediate source of the project.
13388 A warning is issued if both attributes @code{Source_Files} and
13389 @code{Source_List_File} are given explicit values. In this case, the attribute
13390 @code{Source_Files} prevails.
13392 Each source file name must be the name of one existing source file
13393 in one of the source directories.
13395 A @code{Source_Files} attribute whose value is an empty list
13396 indicates that there are no source files in the project.
13398 If the order of the source directories is known statically, that is if
13399 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13400 be several files with the same source file name. In this case, only the file
13401 in the first directory is considered as an immediate source of the project
13402 file. If the order of the source directories is not known statically, it is
13403 an error to have several files with the same source file name.
13405 Projects can be specified to have no Ada source
13406 files: the value of @code{Source_Dirs} or @code{Source_Files} may be an empty
13407 list, or the @code{"Ada"} may be absent from @code{Languages}:
13409 @smallexample @c projectfile
13410 for Source_Dirs use ();
13411 for Source_Files use ();
13412 for Languages use ("C", "C++");
13416 Otherwise, a project must contain at least one immediate source.
13418 Projects with no source files are useful as template packages
13419 (@pxref{Packages in Project Files}) for other projects; in particular to
13420 define a package @code{Naming} (@pxref{Naming Schemes}).
13422 @c ****************************
13423 @c * Importing Projects *
13424 @c ****************************
13426 @node Importing Projects
13427 @section Importing Projects
13428 @cindex @code{ADA_PROJECT_PATH}
13429 @cindex @code{GPR_PROJECT_PATH}
13432 An immediate source of a project P may depend on source files that
13433 are neither immediate sources of P nor in the predefined library.
13434 To get this effect, P must @emph{import} the projects that contain the needed
13437 @smallexample @c projectfile
13439 with "project1", "utilities.gpr";
13440 with "/namings/apex.gpr";
13447 As can be seen in this example, the syntax for importing projects is similar
13448 to the syntax for importing compilation units in Ada. However, project files
13449 use literal strings instead of names, and the @code{with} clause identifies
13450 project files rather than packages.
13452 Each literal string is the file name or path name (absolute or relative) of a
13453 project file. If a string corresponds to a file name, with no path or a
13454 relative path, then its location is determined by the @emph{project path}. The
13455 latter can be queried using @code{gnatls -v}. It contains:
13459 In first position, the directory containing the current project file.
13461 In last position, the default project directory. This default project directory
13462 is part of the GNAT installation and is the standard place to install project
13463 files giving access to standard support libraries.
13465 @ref{Installing a library}
13469 In between, all the directories referenced in the
13470 ^environment variables^logical names^ @env{GPR_PROJECT_PATH}
13471 and @env{ADA_PROJECT_PATH} if they exist, and in that order.
13475 If a relative pathname is used, as in
13477 @smallexample @c projectfile
13482 then the full path for the project is constructed by concatenating this
13483 relative path to those in the project path, in order, until a matching file is
13484 found. Any symbolic link will be fully resolved in the directory of the
13485 importing project file before the imported project file is examined.
13487 If the @code{with}'ed project file name does not have an extension,
13488 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13489 then the file name as specified in the @code{with} clause (no extension) will
13490 be used. In the above example, if a file @code{project1.gpr} is found, then it
13491 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13492 then it will be used; if neither file exists, this is an error.
13494 A warning is issued if the name of the project file does not match the
13495 name of the project; this check is case insensitive.
13497 Any source file that is an immediate source of the imported project can be
13498 used by the immediate sources of the importing project, transitively. Thus
13499 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13500 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13501 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13502 because if and when @code{B} ceases to import @code{C}, some sources in
13503 @code{A} will no longer compile.
13505 A side effect of this capability is that normally cyclic dependencies are not
13506 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13507 is not allowed to import @code{A}. However, there are cases when cyclic
13508 dependencies would be beneficial. For these cases, another form of import
13509 between projects exists, the @code{limited with}: a project @code{A} that
13510 imports a project @code{B} with a straight @code{with} may also be imported,
13511 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13512 to @code{A} include at least one @code{limited with}.
13514 @smallexample @c 0projectfile
13520 limited with "../a/a.gpr";
13528 limited with "../a/a.gpr";
13534 In the above legal example, there are two project cycles:
13537 @item A -> C -> D -> A
13541 In each of these cycle there is one @code{limited with}: import of @code{A}
13542 from @code{B} and import of @code{A} from @code{D}.
13544 The difference between straight @code{with} and @code{limited with} is that
13545 the name of a project imported with a @code{limited with} cannot be used in the
13546 project that imports it. In particular, its packages cannot be renamed and
13547 its variables cannot be referred to.
13549 An exception to the above rules for @code{limited with} is that for the main
13550 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13551 @code{limited with} is equivalent to a straight @code{with}. For example,
13552 in the example above, projects @code{B} and @code{D} could not be main
13553 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13554 each have a @code{limited with} that is the only one in a cycle of importing
13557 @c *********************
13558 @c * Project Extension *
13559 @c *********************
13561 @node Project Extension
13562 @section Project Extension
13565 During development of a large system, it is sometimes necessary to use
13566 modified versions of some of the source files, without changing the original
13567 sources. This can be achieved through the @emph{project extension} facility.
13569 @smallexample @c projectfile
13570 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13574 A project extension declaration introduces an extending project
13575 (the @emph{child}) and a project being extended (the @emph{parent}).
13577 By default, a child project inherits all the sources of its parent.
13578 However, inherited sources can be overridden: a unit in a parent is hidden
13579 by a unit of the same name in the child.
13581 Inherited sources are considered to be sources (but not immediate sources)
13582 of the child project; see @ref{Project File Syntax}.
13584 An inherited source file retains any switches specified in the parent project.
13586 For example if the project @code{Utilities} contains the spec and the
13587 body of an Ada package @code{Util_IO}, then the project
13588 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13589 The original body of @code{Util_IO} will not be considered in program builds.
13590 However, the package spec will still be found in the project
13593 A child project can have only one parent, except when it is qualified as
13594 abstract. But it may import any number of other projects.
13596 A project is not allowed to import directly or indirectly at the same time a
13597 child project and any of its ancestors.
13599 @c *******************************
13600 @c * Project Hierarchy Extension *
13601 @c *******************************
13603 @node Project Hierarchy Extension
13604 @section Project Hierarchy Extension
13607 When extending a large system spanning multiple projects, it is often
13608 inconvenient to extend every project in the hierarchy that is impacted by a
13609 small change introduced. In such cases, it is possible to create a virtual
13610 extension of entire hierarchy using @code{extends all} relationship.
13612 When the project is extended using @code{extends all} inheritance, all projects
13613 that are imported by it, both directly and indirectly, are considered virtually
13614 extended. That is, the Project Manager creates "virtual projects"
13615 that extend every project in the hierarchy; all these virtual projects have
13616 no sources of their own and have as object directory the object directory of
13617 the root of "extending all" project.
13619 It is possible to explicitly extend one or more projects in the hierarchy
13620 in order to modify the sources. These extending projects must be imported by
13621 the "extending all" project, which will replace the corresponding virtual
13622 projects with the explicit ones.
13624 When building such a project hierarchy extension, the Project Manager will
13625 ensure that both modified sources and sources in virtual extending projects
13626 that depend on them, are recompiled.
13628 By means of example, consider the following hierarchy of projects.
13632 project A, containing package P1
13634 project B importing A and containing package P2 which depends on P1
13636 project C importing B and containing package P3 which depends on P2
13640 We want to modify packages P1 and P3.
13642 This project hierarchy will need to be extended as follows:
13646 Create project A1 that extends A, placing modified P1 there:
13648 @smallexample @c 0projectfile
13649 project A1 extends "(@dots{})/A" is
13654 Create project C1 that "extends all" C and imports A1, placing modified
13657 @smallexample @c 0projectfile
13658 with "(@dots{})/A1";
13659 project C1 extends all "(@dots{})/C" is
13664 When you build project C1, your entire modified project space will be
13665 recompiled, including the virtual project B1 that has been impacted by the
13666 "extending all" inheritance of project C.
13668 Note that if a Library Project in the hierarchy is virtually extended,
13669 the virtual project that extends the Library Project is not a Library Project.
13671 @c ****************************************
13672 @c * External References in Project Files *
13673 @c ****************************************
13675 @node External References in Project Files
13676 @section External References in Project Files
13679 A project file may contain references to external variables; such references
13680 are called @emph{external references}.
13682 An external variable is either defined as part of the environment (an
13683 environment variable in Unix, for example) or else specified on the command
13684 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13685 If both, then the command line value is used.
13687 The value of an external reference is obtained by means of the built-in
13688 function @code{external}, which returns a string value.
13689 This function has two forms:
13691 @item @code{external (external_variable_name)}
13692 @item @code{external (external_variable_name, default_value)}
13696 Each parameter must be a string literal. For example:
13698 @smallexample @c projectfile
13700 external ("OS", "GNU/Linux")
13704 In the form with one parameter, the function returns the value of
13705 the external variable given as parameter. If this name is not present in the
13706 environment, the function returns an empty string.
13708 In the form with two string parameters, the second argument is
13709 the value returned when the variable given as the first argument is not
13710 present in the environment. In the example above, if @code{"OS"} is not
13711 the name of ^an environment variable^a logical name^ and is not passed on
13712 the command line, then the returned value is @code{"GNU/Linux"}.
13714 An external reference may be part of a string expression or of a string
13715 list expression, and can therefore appear in a variable declaration or
13716 an attribute declaration.
13718 @smallexample @c projectfile
13720 type Mode_Type is ("Debug", "Release");
13721 Mode : Mode_Type := external ("MODE");
13728 @c *****************************
13729 @c * Packages in Project Files *
13730 @c *****************************
13732 @node Packages in Project Files
13733 @section Packages in Project Files
13736 A @emph{package} defines the settings for project-aware tools within a
13738 For each such tool one can declare a package; the names for these
13739 packages are preset (@pxref{Packages}).
13740 A package may contain variable declarations, attribute declarations, and case
13743 @smallexample @c projectfile
13746 package Builder is -- used by gnatmake
13747 for ^Default_Switches^Default_Switches^ ("Ada")
13756 The syntax of package declarations mimics that of package in Ada.
13758 Most of the packages have an attribute
13759 @code{^Default_Switches^Default_Switches^}.
13760 This attribute is an associative array, and its value is a string list.
13761 The index of the associative array is the name of a programming language (case
13762 insensitive). This attribute indicates the ^switch^switch^
13763 or ^switches^switches^ to be used
13764 with the corresponding tool.
13766 Some packages also have another attribute, @code{^Switches^Switches^},
13767 an associative array whose value is a string list.
13768 The index is the name of a source file.
13769 This attribute indicates the ^switch^switch^
13770 or ^switches^switches^ to be used by the corresponding
13771 tool when dealing with this specific file.
13773 Further information on these ^switch^switch^-related attributes is found in
13774 @ref{^Switches^Switches^ and Project Files}.
13776 A package may be declared as a @emph{renaming} of another package; e.g., from
13777 the project file for an imported project.
13779 @smallexample @c projectfile
13781 with "/global/apex.gpr";
13783 package Naming renames Apex.Naming;
13790 Packages that are renamed in other project files often come from project files
13791 that have no sources: they are just used as templates. Any modification in the
13792 template will be reflected automatically in all the project files that rename
13793 a package from the template.
13795 In addition to the tool-oriented packages, you can also declare a package
13796 named @code{Naming} to establish specialized source file naming conventions
13797 (@pxref{Naming Schemes}).
13799 @c ************************************
13800 @c * Variables from Imported Projects *
13801 @c ************************************
13803 @node Variables from Imported Projects
13804 @section Variables from Imported Projects
13807 An attribute or variable defined in an imported or parent project can
13808 be used in expressions in the importing / extending project.
13809 Such an attribute or variable is denoted by an expanded name whose prefix
13810 is either the name of the project or the expanded name of a package within
13813 @smallexample @c projectfile
13816 project Main extends "base" is
13817 Var1 := Imported.Var;
13818 Var2 := Base.Var & ".new";
13823 for ^Default_Switches^Default_Switches^ ("Ada")
13824 use Imported.Builder'Ada_^Switches^Switches^ &
13825 "^-gnatg^-gnatg^" &
13831 package Compiler is
13832 for ^Default_Switches^Default_Switches^ ("Ada")
13833 use Base.Compiler'Ada_^Switches^Switches^;
13844 The value of @code{Var1} is a copy of the variable @code{Var} defined
13845 in the project file @file{"imported.gpr"}
13847 the value of @code{Var2} is a copy of the value of variable @code{Var}
13848 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13850 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13851 @code{Builder} is a string list that includes in its value a copy of the value
13852 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13853 in project file @file{imported.gpr} plus two new elements:
13854 @option{"^-gnatg^-gnatg^"}
13855 and @option{"^-v^-v^"};
13857 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13858 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13859 defined in the @code{Compiler} package in project file @file{base.gpr},
13860 the project being extended.
13863 @c ******************
13864 @c * Naming Schemes *
13865 @c ******************
13867 @node Naming Schemes
13868 @section Naming Schemes
13871 Sometimes an Ada software system is ported from a foreign compilation
13872 environment to GNAT, and the file names do not use the default GNAT
13873 conventions. Instead of changing all the file names (which for a variety
13874 of reasons might not be possible), you can define the relevant file
13875 naming scheme in the @code{Naming} package in your project file.
13878 Note that the use of pragmas described in
13879 @ref{Alternative File Naming Schemes} by mean of a configuration
13880 pragmas file is not supported when using project files. You must use
13881 the features described in this paragraph. You can however use specify
13882 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13885 For example, the following
13886 package models the Apex file naming rules:
13888 @smallexample @c projectfile
13891 for Casing use "lowercase";
13892 for Dot_Replacement use ".";
13893 for Spec_Suffix ("Ada") use ".1.ada";
13894 for Body_Suffix ("Ada") use ".2.ada";
13901 For example, the following package models the HP Ada file naming rules:
13903 @smallexample @c projectfile
13906 for Casing use "lowercase";
13907 for Dot_Replacement use "__";
13908 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13909 for Body_Suffix ("Ada") use ".^ada^ada^";
13915 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13916 names in lower case)
13920 You can define the following attributes in package @code{Naming}:
13924 @item @code{Casing}
13925 This must be a string with one of the three values @code{"lowercase"},
13926 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13929 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13931 @item @code{Dot_Replacement}
13932 This must be a string whose value satisfies the following conditions:
13935 @item It must not be empty
13936 @item It cannot start or end with an alphanumeric character
13937 @item It cannot be a single underscore
13938 @item It cannot start with an underscore followed by an alphanumeric
13939 @item It cannot contain a dot @code{'.'} except if the entire string
13944 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13946 @item @code{Spec_Suffix}
13947 This is an associative array (indexed by the programming language name, case
13948 insensitive) whose value is a string that must satisfy the following
13952 @item It must not be empty
13953 @item It must include at least one dot
13956 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13957 @code{"^.ads^.ADS^"}.
13959 @item @code{Body_Suffix}
13960 This is an associative array (indexed by the programming language name, case
13961 insensitive) whose value is a string that must satisfy the following
13965 @item It must not be empty
13966 @item It must include at least one dot
13967 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13970 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13971 same string, then a file name that ends with the longest of these two suffixes
13972 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13973 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13975 If the suffix does not start with a '.', a file with a name exactly equal
13976 to the suffix will also be part of the project (for instance if you define
13977 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13978 of the project. This is not interesting in general when using projects to
13979 compile. However, it might become useful when a project is also used to
13980 find the list of source files in an editor, like the GNAT Programming System
13983 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13984 @code{"^.adb^.ADB^"}.
13986 @item @code{Separate_Suffix}
13987 This must be a string whose value satisfies the same conditions as
13988 @code{Body_Suffix}. The same "longest suffix" rules apply.
13991 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13992 value as @code{Body_Suffix ("Ada")}.
13996 You can use the associative array attribute @code{Spec} to define
13997 the source file name for an individual Ada compilation unit's spec. The array
13998 index must be a string literal that identifies the Ada unit (case insensitive).
13999 The value of this attribute must be a string that identifies the file that
14000 contains this unit's spec (case sensitive or insensitive depending on the
14003 @smallexample @c projectfile
14004 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
14007 When the source file contains several units, you can indicate at what
14008 position the unit occurs in the file, with the following. The first unit
14009 in the file has index 1
14011 @smallexample @c projectfile
14012 for Body ("top") use "foo.a" at 1;
14013 for Body ("foo") use "foo.a" at 2;
14018 You can use the associative array attribute @code{Body} to
14019 define the source file name for an individual Ada compilation unit's body
14020 (possibly a subunit). The array index must be a string literal that identifies
14021 the Ada unit (case insensitive). The value of this attribute must be a string
14022 that identifies the file that contains this unit's body or subunit (case
14023 sensitive or insensitive depending on the operating system).
14025 @smallexample @c projectfile
14026 for Body ("MyPack.MyChild") use "mypack.mychild.body";
14030 @c ********************
14031 @c * Library Projects *
14032 @c ********************
14034 @node Library Projects
14035 @section Library Projects
14038 @emph{Library projects} are projects whose object code is placed in a library.
14039 (Note that this facility is not yet supported on all platforms).
14041 @code{gnatmake} or @code{gprbuild} will collect all object files into a
14042 single archive, which might either be a shared or a static library. This
14043 library can later on be linked with multiple executables, potentially
14044 reducing their sizes.
14046 If your project file specifies languages other than Ada, but you are still
14047 using @code{gnatmake} to compile and link, the latter will not try to
14048 compile your sources other than Ada (you should use @code{gprbuild} if that
14049 is your intent). However, @code{gnatmake} will automatically link all object
14050 files found in the object directory, whether or not they were compiled from
14051 an Ada source file. This specific behavior only applies when multiple
14052 languages are specified.
14054 To create a library project, you need to define in its project file
14055 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
14056 Additionally, you may define other library-related attributes such as
14057 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
14058 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
14060 The @code{Library_Name} attribute has a string value. There is no restriction
14061 on the name of a library. It is the responsibility of the developer to
14062 choose a name that will be accepted by the platform. It is recommended to
14063 choose names that could be Ada identifiers; such names are almost guaranteed
14064 to be acceptable on all platforms.
14066 The @code{Library_Dir} attribute has a string value that designates the path
14067 (absolute or relative) of the directory where the library will reside.
14068 It must designate an existing directory, and this directory must be writable,
14069 different from the project's object directory and from any source directory
14070 in the project tree.
14072 If both @code{Library_Name} and @code{Library_Dir} are specified and
14073 are legal, then the project file defines a library project. The optional
14074 library-related attributes are checked only for such project files.
14076 The @code{Library_Kind} attribute has a string value that must be one of the
14077 following (case insensitive): @code{"static"}, @code{"dynamic"} or
14078 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
14079 attribute is not specified, the library is a static library, that is
14080 an archive of object files that can be potentially linked into a
14081 static executable. Otherwise, the library may be dynamic or
14082 relocatable, that is a library that is loaded only at the start of execution.
14084 If you need to build both a static and a dynamic library, you should use two
14085 different object directories, since in some cases some extra code needs to
14086 be generated for the latter. For such cases, it is recommended to either use
14087 two different project files, or a single one which uses external variables
14088 to indicate what kind of library should be build.
14090 The @code{Library_ALI_Dir} attribute may be specified to indicate the
14091 directory where the ALI files of the library will be copied. When it is
14092 not specified, the ALI files are copied to the directory specified in
14093 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
14094 must be writable and different from the project's object directory and from
14095 any source directory in the project tree.
14097 The @code{Library_Version} attribute has a string value whose interpretation
14098 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14099 used only for dynamic/relocatable libraries as the internal name of the
14100 library (the @code{"soname"}). If the library file name (built from the
14101 @code{Library_Name}) is different from the @code{Library_Version}, then the
14102 library file will be a symbolic link to the actual file whose name will be
14103 @code{Library_Version}.
14107 @smallexample @c projectfile
14113 for Library_Dir use "lib_dir";
14114 for Library_Name use "dummy";
14115 for Library_Kind use "relocatable";
14116 for Library_Version use "libdummy.so." & Version;
14123 Directory @file{lib_dir} will contain the internal library file whose name
14124 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14125 @file{libdummy.so.1}.
14127 When @command{gnatmake} detects that a project file
14128 is a library project file, it will check all immediate sources of the project
14129 and rebuild the library if any of the sources have been recompiled.
14131 Standard project files can import library project files. In such cases,
14132 the libraries will only be rebuilt if some of its sources are recompiled
14133 because they are in the closure of some other source in an importing project.
14134 Sources of the library project files that are not in such a closure will
14135 not be checked, unless the full library is checked, because one of its sources
14136 needs to be recompiled.
14138 For instance, assume the project file @code{A} imports the library project file
14139 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14140 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14141 @file{l2.ads}, @file{l2.adb}.
14143 If @file{l1.adb} has been modified, then the library associated with @code{L}
14144 will be rebuilt when compiling all the immediate sources of @code{A} only
14145 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14148 To be sure that all the sources in the library associated with @code{L} are
14149 up to date, and that all the sources of project @code{A} are also up to date,
14150 the following two commands needs to be used:
14157 When a library is built or rebuilt, an attempt is made first to delete all
14158 files in the library directory.
14159 All @file{ALI} files will also be copied from the object directory to the
14160 library directory. To build executables, @command{gnatmake} will use the
14161 library rather than the individual object files.
14164 It is also possible to create library project files for third-party libraries
14165 that are precompiled and cannot be compiled locally thanks to the
14166 @code{externally_built} attribute. (See @ref{Installing a library}).
14169 @c *******************************
14170 @c * Stand-alone Library Projects *
14171 @c *******************************
14173 @node Stand-alone Library Projects
14174 @section Stand-alone Library Projects
14177 A Stand-alone Library is a library that contains the necessary code to
14178 elaborate the Ada units that are included in the library. A Stand-alone
14179 Library is suitable to be used in an executable when the main is not
14180 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14183 A Stand-alone Library Project is a Library Project where the library is
14184 a Stand-alone Library.
14186 To be a Stand-alone Library Project, in addition to the two attributes
14187 that make a project a Library Project (@code{Library_Name} and
14188 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14189 @code{Library_Interface} must be defined.
14191 @smallexample @c projectfile
14193 for Library_Dir use "lib_dir";
14194 for Library_Name use "dummy";
14195 for Library_Interface use ("int1", "int1.child");
14199 Attribute @code{Library_Interface} has a nonempty string list value,
14200 each string in the list designating a unit contained in an immediate source
14201 of the project file.
14203 When a Stand-alone Library is built, first the binder is invoked to build
14204 a package whose name depends on the library name
14205 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14206 This binder-generated package includes initialization and
14207 finalization procedures whose
14208 names depend on the library name (dummyinit and dummyfinal in the example
14209 above). The object corresponding to this package is included in the library.
14211 A dynamic or relocatable Stand-alone Library is automatically initialized
14212 if automatic initialization of Stand-alone Libraries is supported on the
14213 platform and if attribute @code{Library_Auto_Init} is not specified or
14214 is specified with the value "true". A static Stand-alone Library is never
14215 automatically initialized.
14217 Single string attribute @code{Library_Auto_Init} may be specified with only
14218 two possible values: "false" or "true" (case-insensitive). Specifying
14219 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14220 initialization of dynamic or relocatable libraries.
14222 When a non-automatically initialized Stand-alone Library is used
14223 in an executable, its initialization procedure must be called before
14224 any service of the library is used.
14225 When the main subprogram is in Ada, it may mean that the initialization
14226 procedure has to be called during elaboration of another package.
14228 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14229 (those that are listed in attribute @code{Library_Interface}) are copied to
14230 the Library Directory. As a consequence, only the Interface Units may be
14231 imported from Ada units outside of the library. If other units are imported,
14232 the binding phase will fail.
14234 When a Stand-Alone Library is bound, the switches that are specified in
14235 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14236 used in the call to @command{gnatbind}.
14238 The string list attribute @code{Library_Options} may be used to specified
14239 additional switches to the call to @command{gcc} to link the library.
14241 The attribute @code{Library_Src_Dir}, may be specified for a
14242 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14243 single string value. Its value must be the path (absolute or relative to the
14244 project directory) of an existing directory. This directory cannot be the
14245 object directory or one of the source directories, but it can be the same as
14246 the library directory. The sources of the Interface
14247 Units of the library, necessary to an Ada client of the library, will be
14248 copied to the designated directory, called Interface Copy directory.
14249 These sources includes the specs of the Interface Units, but they may also
14250 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14251 are used, or when there is a generic units in the spec. Before the sources
14252 are copied to the Interface Copy directory, an attempt is made to delete all
14253 files in the Interface Copy directory.
14255 @c *************************************
14256 @c * Switches Related to Project Files *
14257 @c *************************************
14258 @node Switches Related to Project Files
14259 @section Switches Related to Project Files
14262 The following switches are used by GNAT tools that support project files:
14266 @item ^-P^/PROJECT_FILE=^@var{project}
14267 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14268 Indicates the name of a project file. This project file will be parsed with
14269 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14270 if any, and using the external references indicated
14271 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14273 There may zero, one or more spaces between @option{-P} and @var{project}.
14277 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14280 Since the Project Manager parses the project file only after all the switches
14281 on the command line are checked, the order of the switches
14282 @option{^-P^/PROJECT_FILE^},
14283 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14284 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14286 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14287 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14288 Indicates that external variable @var{name} has the value @var{value}.
14289 The Project Manager will use this value for occurrences of
14290 @code{external(name)} when parsing the project file.
14294 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14295 put between quotes.
14303 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14304 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14305 @var{name}, only the last one is used.
14308 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14309 takes precedence over the value of the same name in the environment.
14311 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14312 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14313 Indicates the verbosity of the parsing of GNAT project files.
14316 @option{-vP0} means Default;
14317 @option{-vP1} means Medium;
14318 @option{-vP2} means High.
14322 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14327 The default is ^Default^DEFAULT^: no output for syntactically correct
14330 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14331 only the last one is used.
14333 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14334 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14335 Add directory <dir> at the beginning of the project search path, in order,
14336 after the current working directory.
14340 @cindex @option{-eL} (any project-aware tool)
14341 Follow all symbolic links when processing project files.
14344 @item ^--subdirs^/SUBDIRS^=<subdir>
14345 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14346 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14347 directories (except the source directories) are the subdirectories <subdir>
14348 of the directories specified in the project files. This applies in particular
14349 to object directories, library directories and exec directories. If the
14350 subdirectories do not exist, they are created automatically.
14354 @c **********************************
14355 @c * Tools Supporting Project Files *
14356 @c **********************************
14358 @node Tools Supporting Project Files
14359 @section Tools Supporting Project Files
14362 * gnatmake and Project Files::
14363 * The GNAT Driver and Project Files::
14366 @node gnatmake and Project Files
14367 @subsection gnatmake and Project Files
14370 This section covers several topics related to @command{gnatmake} and
14371 project files: defining ^switches^switches^ for @command{gnatmake}
14372 and for the tools that it invokes; specifying configuration pragmas;
14373 the use of the @code{Main} attribute; building and rebuilding library project
14377 * ^Switches^Switches^ and Project Files::
14378 * Specifying Configuration Pragmas::
14379 * Project Files and Main Subprograms::
14380 * Library Project Files::
14383 @node ^Switches^Switches^ and Project Files
14384 @subsubsection ^Switches^Switches^ and Project Files
14387 It is not currently possible to specify VMS style qualifiers in the project
14388 files; only Unix style ^switches^switches^ may be specified.
14392 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14393 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14394 attribute, a @code{^Switches^Switches^} attribute, or both;
14395 as their names imply, these ^switch^switch^-related
14396 attributes affect the ^switches^switches^ that are used for each of these GNAT
14398 @command{gnatmake} is invoked. As will be explained below, these
14399 component-specific ^switches^switches^ precede
14400 the ^switches^switches^ provided on the @command{gnatmake} command line.
14402 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14403 array indexed by language name (case insensitive) whose value is a string list.
14406 @smallexample @c projectfile
14408 package Compiler is
14409 for ^Default_Switches^Default_Switches^ ("Ada")
14410 use ("^-gnaty^-gnaty^",
14417 The @code{^Switches^Switches^} attribute is also an associative array,
14418 indexed by a file name (which may or may not be case sensitive, depending
14419 on the operating system) whose value is a string list. For example:
14421 @smallexample @c projectfile
14424 for ^Switches^Switches^ ("main1.adb")
14426 for ^Switches^Switches^ ("main2.adb")
14433 For the @code{Builder} package, the file names must designate source files
14434 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14435 file names must designate @file{ALI} or source files for main subprograms.
14436 In each case just the file name without an explicit extension is acceptable.
14438 For each tool used in a program build (@command{gnatmake}, the compiler, the
14439 binder, and the linker), the corresponding package @dfn{contributes} a set of
14440 ^switches^switches^ for each file on which the tool is invoked, based on the
14441 ^switch^switch^-related attributes defined in the package.
14442 In particular, the ^switches^switches^
14443 that each of these packages contributes for a given file @var{f} comprise:
14447 the value of attribute @code{^Switches^Switches^ (@var{f})},
14448 if it is specified in the package for the given file,
14450 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14451 if it is specified in the package.
14455 If neither of these attributes is defined in the package, then the package does
14456 not contribute any ^switches^switches^ for the given file.
14458 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14459 two sets, in the following order: those contributed for the file
14460 by the @code{Builder} package;
14461 and the switches passed on the command line.
14463 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14464 the ^switches^switches^ passed to the tool comprise three sets,
14465 in the following order:
14469 the applicable ^switches^switches^ contributed for the file
14470 by the @code{Builder} package in the project file supplied on the command line;
14473 those contributed for the file by the package (in the relevant project file --
14474 see below) corresponding to the tool; and
14477 the applicable switches passed on the command line.
14481 The term @emph{applicable ^switches^switches^} reflects the fact that
14482 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14483 tools, depending on the individual ^switch^switch^.
14485 @command{gnatmake} may invoke the compiler on source files from different
14486 projects. The Project Manager will use the appropriate project file to
14487 determine the @code{Compiler} package for each source file being compiled.
14488 Likewise for the @code{Binder} and @code{Linker} packages.
14490 As an example, consider the following package in a project file:
14492 @smallexample @c projectfile
14495 package Compiler is
14496 for ^Default_Switches^Default_Switches^ ("Ada")
14498 for ^Switches^Switches^ ("a.adb")
14500 for ^Switches^Switches^ ("b.adb")
14502 "^-gnaty^-gnaty^");
14509 If @command{gnatmake} is invoked with this project file, and it needs to
14510 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14511 @file{a.adb} will be compiled with the ^switch^switch^
14512 @option{^-O1^-O1^},
14513 @file{b.adb} with ^switches^switches^
14515 and @option{^-gnaty^-gnaty^},
14516 and @file{c.adb} with @option{^-g^-g^}.
14518 The following example illustrates the ordering of the ^switches^switches^
14519 contributed by different packages:
14521 @smallexample @c projectfile
14525 for ^Switches^Switches^ ("main.adb")
14533 package Compiler is
14534 for ^Switches^Switches^ ("main.adb")
14542 If you issue the command:
14545 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14549 then the compiler will be invoked on @file{main.adb} with the following
14550 sequence of ^switches^switches^
14553 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14556 with the last @option{^-O^-O^}
14557 ^switch^switch^ having precedence over the earlier ones;
14558 several other ^switches^switches^
14559 (such as @option{^-c^-c^}) are added implicitly.
14561 The ^switches^switches^
14563 and @option{^-O1^-O1^} are contributed by package
14564 @code{Builder}, @option{^-O2^-O2^} is contributed
14565 by the package @code{Compiler}
14566 and @option{^-O0^-O0^} comes from the command line.
14568 The @option{^-g^-g^}
14569 ^switch^switch^ will also be passed in the invocation of
14570 @command{Gnatlink.}
14572 A final example illustrates switch contributions from packages in different
14575 @smallexample @c projectfile
14578 for Source_Files use ("pack.ads", "pack.adb");
14579 package Compiler is
14580 for ^Default_Switches^Default_Switches^ ("Ada")
14581 use ("^-gnata^-gnata^");
14589 for Source_Files use ("foo_main.adb", "bar_main.adb");
14591 for ^Switches^Switches^ ("foo_main.adb")
14599 -- Ada source file:
14601 procedure Foo_Main is
14609 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14613 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14614 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14615 @option{^-gnato^-gnato^} (passed on the command line).
14616 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14617 are @option{^-g^-g^} from @code{Proj4.Builder},
14618 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14619 and @option{^-gnato^-gnato^} from the command line.
14622 When using @command{gnatmake} with project files, some ^switches^switches^ or
14623 arguments may be expressed as relative paths. As the working directory where
14624 compilation occurs may change, these relative paths are converted to absolute
14625 paths. For the ^switches^switches^ found in a project file, the relative paths
14626 are relative to the project file directory, for the switches on the command
14627 line, they are relative to the directory where @command{gnatmake} is invoked.
14628 The ^switches^switches^ for which this occurs are:
14634 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14636 ^-o^-o^, object files specified in package @code{Linker} or after
14637 -largs on the command line). The exception to this rule is the ^switch^switch^
14638 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14640 @node Specifying Configuration Pragmas
14641 @subsubsection Specifying Configuration Pragmas
14643 When using @command{gnatmake} with project files, if there exists a file
14644 @file{gnat.adc} that contains configuration pragmas, this file will be
14647 Configuration pragmas can be defined by means of the following attributes in
14648 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14649 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14651 Both these attributes are single string attributes. Their values is the path
14652 name of a file containing configuration pragmas. If a path name is relative,
14653 then it is relative to the project directory of the project file where the
14654 attribute is defined.
14656 When compiling a source, the configuration pragmas used are, in order,
14657 those listed in the file designated by attribute
14658 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14659 project file, if it is specified, and those listed in the file designated by
14660 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14661 the project file of the source, if it exists.
14663 @node Project Files and Main Subprograms
14664 @subsubsection Project Files and Main Subprograms
14667 When using a project file, you can invoke @command{gnatmake}
14668 with one or several main subprograms, by specifying their source files on the
14672 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14676 Each of these needs to be a source file of the same project, except
14677 when the switch ^-u^/UNIQUE^ is used.
14680 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14681 same project, one of the project in the tree rooted at the project specified
14682 on the command line. The package @code{Builder} of this common project, the
14683 "main project" is the one that is considered by @command{gnatmake}.
14686 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14687 imported directly or indirectly by the project specified on the command line.
14688 Note that if such a source file is not part of the project specified on the
14689 command line, the ^switches^switches^ found in package @code{Builder} of the
14690 project specified on the command line, if any, that are transmitted
14691 to the compiler will still be used, not those found in the project file of
14695 When using a project file, you can also invoke @command{gnatmake} without
14696 explicitly specifying any main, and the effect depends on whether you have
14697 defined the @code{Main} attribute. This attribute has a string list value,
14698 where each element in the list is the name of a source file (the file
14699 extension is optional) that contains a unit that can be a main subprogram.
14701 If the @code{Main} attribute is defined in a project file as a non-empty
14702 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14703 line, then invoking @command{gnatmake} with this project file but without any
14704 main on the command line is equivalent to invoking @command{gnatmake} with all
14705 the file names in the @code{Main} attribute on the command line.
14708 @smallexample @c projectfile
14711 for Main use ("main1", "main2", "main3");
14717 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14719 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14721 When the project attribute @code{Main} is not specified, or is specified
14722 as an empty string list, or when the switch @option{-u} is used on the command
14723 line, then invoking @command{gnatmake} with no main on the command line will
14724 result in all immediate sources of the project file being checked, and
14725 potentially recompiled. Depending on the presence of the switch @option{-u},
14726 sources from other project files on which the immediate sources of the main
14727 project file depend are also checked and potentially recompiled. In other
14728 words, the @option{-u} switch is applied to all of the immediate sources of the
14731 When no main is specified on the command line and attribute @code{Main} exists
14732 and includes several mains, or when several mains are specified on the
14733 command line, the default ^switches^switches^ in package @code{Builder} will
14734 be used for all mains, even if there are specific ^switches^switches^
14735 specified for one or several mains.
14737 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14738 the specific ^switches^switches^ for each main, if they are specified.
14740 @node Library Project Files
14741 @subsubsection Library Project Files
14744 When @command{gnatmake} is invoked with a main project file that is a library
14745 project file, it is not allowed to specify one or more mains on the command
14749 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14750 ^-l^/ACTION=LINK^ have special meanings.
14753 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14754 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14757 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14758 to @command{gnatmake} that the binder generated file should be compiled
14759 (in the case of a stand-alone library) and that the library should be built.
14763 @node The GNAT Driver and Project Files
14764 @subsection The GNAT Driver and Project Files
14767 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14768 can benefit from project files:
14769 @command{^gnatbind^gnatbind^},
14770 @command{^gnatcheck^gnatcheck^}),
14771 @command{^gnatclean^gnatclean^}),
14772 @command{^gnatelim^gnatelim^},
14773 @command{^gnatfind^gnatfind^},
14774 @command{^gnatlink^gnatlink^},
14775 @command{^gnatls^gnatls^},
14776 @command{^gnatmetric^gnatmetric^},
14777 @command{^gnatpp^gnatpp^},
14778 @command{^gnatstub^gnatstub^},
14779 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14780 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14781 They must be invoked through the @command{gnat} driver.
14783 The @command{gnat} driver is a wrapper that accepts a number of commands and
14784 calls the corresponding tool. It was designed initially for VMS platforms (to
14785 convert VMS qualifiers to Unix-style switches), but it is now available on all
14788 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14789 (case insensitive):
14793 BIND to invoke @command{^gnatbind^gnatbind^}
14795 CHOP to invoke @command{^gnatchop^gnatchop^}
14797 CLEAN to invoke @command{^gnatclean^gnatclean^}
14799 COMP or COMPILE to invoke the compiler
14801 ELIM to invoke @command{^gnatelim^gnatelim^}
14803 FIND to invoke @command{^gnatfind^gnatfind^}
14805 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14807 LINK to invoke @command{^gnatlink^gnatlink^}
14809 LS or LIST to invoke @command{^gnatls^gnatls^}
14811 MAKE to invoke @command{^gnatmake^gnatmake^}
14813 NAME to invoke @command{^gnatname^gnatname^}
14815 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14817 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14819 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14821 STUB to invoke @command{^gnatstub^gnatstub^}
14823 XREF to invoke @command{^gnatxref^gnatxref^}
14827 (note that the compiler is invoked using the command
14828 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14831 On non-VMS platforms, between @command{gnat} and the command, two
14832 special switches may be used:
14836 @command{-v} to display the invocation of the tool.
14838 @command{-dn} to prevent the @command{gnat} driver from removing
14839 the temporary files it has created. These temporary files are
14840 configuration files and temporary file list files.
14844 The command may be followed by switches and arguments for the invoked
14848 gnat bind -C main.ali
14854 Switches may also be put in text files, one switch per line, and the text
14855 files may be specified with their path name preceded by '@@'.
14858 gnat bind @@args.txt main.ali
14862 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14863 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14864 (@option{^-P^/PROJECT_FILE^},
14865 @option{^-X^/EXTERNAL_REFERENCE^} and
14866 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14867 the switches of the invoking tool.
14870 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14871 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14872 the immediate sources of the specified project file.
14875 When GNAT METRIC is used with a project file, but with no source
14876 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14877 with all the immediate sources of the specified project file and with
14878 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14882 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14883 a project file, no source is specified on the command line and
14884 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14885 the underlying tool (^gnatpp^gnatpp^ or
14886 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14887 not only for the immediate sources of the main project.
14889 (-U stands for Universal or Union of the project files of the project tree)
14893 For each of the following commands, there is optionally a corresponding
14894 package in the main project.
14898 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14901 package @code{Check} for command CHECK (invoking
14902 @code{^gnatcheck^gnatcheck^})
14905 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14908 package @code{Cross_Reference} for command XREF (invoking
14909 @code{^gnatxref^gnatxref^})
14912 package @code{Eliminate} for command ELIM (invoking
14913 @code{^gnatelim^gnatelim^})
14916 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14919 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14922 package @code{Gnatstub} for command STUB
14923 (invoking @code{^gnatstub^gnatstub^})
14926 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14929 package @code{Metrics} for command METRIC
14930 (invoking @code{^gnatmetric^gnatmetric^})
14933 package @code{Pretty_Printer} for command PP or PRETTY
14934 (invoking @code{^gnatpp^gnatpp^})
14939 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14940 a simple variable with a string list value. It contains ^switches^switches^
14941 for the invocation of @code{^gnatls^gnatls^}.
14943 @smallexample @c projectfile
14947 for ^Switches^Switches^
14956 All other packages have two attribute @code{^Switches^Switches^} and
14957 @code{^Default_Switches^Default_Switches^}.
14960 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14961 source file name, that has a string list value: the ^switches^switches^ to be
14962 used when the tool corresponding to the package is invoked for the specific
14966 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14967 indexed by the programming language that has a string list value.
14968 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14969 ^switches^switches^ for the invocation of the tool corresponding
14970 to the package, except if a specific @code{^Switches^Switches^} attribute
14971 is specified for the source file.
14973 @smallexample @c projectfile
14977 for Source_Dirs use ("./**");
14980 for ^Switches^Switches^ use
14987 package Compiler is
14988 for ^Default_Switches^Default_Switches^ ("Ada")
14989 use ("^-gnatv^-gnatv^",
14990 "^-gnatwa^-gnatwa^");
14996 for ^Default_Switches^Default_Switches^ ("Ada")
15004 for ^Default_Switches^Default_Switches^ ("Ada")
15006 for ^Switches^Switches^ ("main.adb")
15015 for ^Default_Switches^Default_Switches^ ("Ada")
15022 package Cross_Reference is
15023 for ^Default_Switches^Default_Switches^ ("Ada")
15028 end Cross_Reference;
15034 With the above project file, commands such as
15037 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
15038 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
15039 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
15040 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
15041 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
15045 will set up the environment properly and invoke the tool with the switches
15046 found in the package corresponding to the tool:
15047 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
15048 except @code{^Switches^Switches^ ("main.adb")}
15049 for @code{^gnatlink^gnatlink^}.
15050 It is also possible to invoke some of the tools,
15051 @code{^gnatcheck^gnatcheck^}),
15052 @code{^gnatmetric^gnatmetric^}),
15053 and @code{^gnatpp^gnatpp^})
15054 on a set of project units thanks to the combination of the switches
15055 @option{-P}, @option{-U} and possibly the main unit when one is interested
15056 in its closure. For instance,
15060 will compute the metrics for all the immediate units of project
15063 gnat metric -Pproj -U
15065 will compute the metrics for all the units of the closure of projects
15066 rooted at @code{proj}.
15068 gnat metric -Pproj -U main_unit
15070 will compute the metrics for the closure of units rooted at
15071 @code{main_unit}. This last possibility relies implicitly
15072 on @command{gnatbind}'s option @option{-R}.
15074 @c **********************
15075 @node An Extended Example
15076 @section An Extended Example
15079 Suppose that we have two programs, @var{prog1} and @var{prog2},
15080 whose sources are in corresponding directories. We would like
15081 to build them with a single @command{gnatmake} command, and we want to place
15082 their object files into @file{build} subdirectories of the source directories.
15083 Furthermore, we want to have to have two separate subdirectories
15084 in @file{build} -- @file{release} and @file{debug} -- which will contain
15085 the object files compiled with different set of compilation flags.
15087 In other words, we have the following structure:
15104 Here are the project files that we must place in a directory @file{main}
15105 to maintain this structure:
15109 @item We create a @code{Common} project with a package @code{Compiler} that
15110 specifies the compilation ^switches^switches^:
15115 @b{project} Common @b{is}
15117 @b{for} Source_Dirs @b{use} (); -- No source files
15121 @b{type} Build_Type @b{is} ("release", "debug");
15122 Build : Build_Type := External ("BUILD", "debug");
15125 @b{package} Compiler @b{is}
15126 @b{case} Build @b{is}
15127 @b{when} "release" =>
15128 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15129 @b{use} ("^-O2^-O2^");
15130 @b{when} "debug" =>
15131 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15132 @b{use} ("^-g^-g^");
15140 @item We create separate projects for the two programs:
15147 @b{project} Prog1 @b{is}
15149 @b{for} Source_Dirs @b{use} ("prog1");
15150 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15152 @b{package} Compiler @b{renames} Common.Compiler;
15163 @b{project} Prog2 @b{is}
15165 @b{for} Source_Dirs @b{use} ("prog2");
15166 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15168 @b{package} Compiler @b{renames} Common.Compiler;
15174 @item We create a wrapping project @code{Main}:
15183 @b{project} Main @b{is}
15185 @b{package} Compiler @b{renames} Common.Compiler;
15191 @item Finally we need to create a dummy procedure that @code{with}s (either
15192 explicitly or implicitly) all the sources of our two programs.
15197 Now we can build the programs using the command
15200 gnatmake ^-P^/PROJECT_FILE=^main dummy
15204 for the Debug mode, or
15208 gnatmake -Pmain -XBUILD=release
15214 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15219 for the Release mode.
15221 @c ********************************
15222 @c * Project File Complete Syntax *
15223 @c ********************************
15225 @node Project File Complete Syntax
15226 @section Project File Complete Syntax
15230 context_clause project_declaration
15236 @b{with} path_name @{ , path_name @} ;
15241 project_declaration ::=
15242 simple_project_declaration | project_extension
15244 simple_project_declaration ::=
15245 @b{project} <project_>simple_name @b{is}
15246 @{declarative_item@}
15247 @b{end} <project_>simple_name;
15249 project_extension ::=
15250 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15251 @{declarative_item@}
15252 @b{end} <project_>simple_name;
15254 declarative_item ::=
15255 package_declaration |
15256 typed_string_declaration |
15257 other_declarative_item
15259 package_declaration ::=
15260 package_spec | package_renaming
15263 @b{package} package_identifier @b{is}
15264 @{simple_declarative_item@}
15265 @b{end} package_identifier ;
15267 package_identifier ::=
15268 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15269 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15270 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15272 package_renaming ::==
15273 @b{package} package_identifier @b{renames}
15274 <project_>simple_name.package_identifier ;
15276 typed_string_declaration ::=
15277 @b{type} <typed_string_>_simple_name @b{is}
15278 ( string_literal @{, string_literal@} );
15280 other_declarative_item ::=
15281 attribute_declaration |
15282 typed_variable_declaration |
15283 variable_declaration |
15286 attribute_declaration ::=
15287 full_associative_array_declaration |
15288 @b{for} attribute_designator @b{use} expression ;
15290 full_associative_array_declaration ::=
15291 @b{for} <associative_array_attribute_>simple_name @b{use}
15292 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15294 attribute_designator ::=
15295 <simple_attribute_>simple_name |
15296 <associative_array_attribute_>simple_name ( string_literal )
15298 typed_variable_declaration ::=
15299 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15301 variable_declaration ::=
15302 <variable_>simple_name := expression;
15312 attribute_reference
15318 ( <string_>expression @{ , <string_>expression @} )
15321 @b{external} ( string_literal [, string_literal] )
15323 attribute_reference ::=
15324 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15326 attribute_prefix ::=
15328 <project_>simple_name | package_identifier |
15329 <project_>simple_name . package_identifier
15331 case_construction ::=
15332 @b{case} <typed_variable_>name @b{is}
15337 @b{when} discrete_choice_list =>
15338 @{case_construction | attribute_declaration@}
15340 discrete_choice_list ::=
15341 string_literal @{| string_literal@} |
15345 simple_name @{. simple_name@}
15348 identifier (same as Ada)
15352 @node The Cross-Referencing Tools gnatxref and gnatfind
15353 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15358 The compiler generates cross-referencing information (unless
15359 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15360 This information indicates where in the source each entity is declared and
15361 referenced. Note that entities in package Standard are not included, but
15362 entities in all other predefined units are included in the output.
15364 Before using any of these two tools, you need to compile successfully your
15365 application, so that GNAT gets a chance to generate the cross-referencing
15368 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15369 information to provide the user with the capability to easily locate the
15370 declaration and references to an entity. These tools are quite similar,
15371 the difference being that @code{gnatfind} is intended for locating
15372 definitions and/or references to a specified entity or entities, whereas
15373 @code{gnatxref} is oriented to generating a full report of all
15376 To use these tools, you must not compile your application using the
15377 @option{-gnatx} switch on the @command{gnatmake} command line
15378 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15379 information will not be generated.
15381 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15382 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15385 * Switches for gnatxref::
15386 * Switches for gnatfind::
15387 * Project Files for gnatxref and gnatfind::
15388 * Regular Expressions in gnatfind and gnatxref::
15389 * Examples of gnatxref Usage::
15390 * Examples of gnatfind Usage::
15393 @node Switches for gnatxref
15394 @section @code{gnatxref} Switches
15397 The command invocation for @code{gnatxref} is:
15399 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15408 identifies the source files for which a report is to be generated. The
15409 ``with''ed units will be processed too. You must provide at least one file.
15411 These file names are considered to be regular expressions, so for instance
15412 specifying @file{source*.adb} is the same as giving every file in the current
15413 directory whose name starts with @file{source} and whose extension is
15416 You shouldn't specify any directory name, just base names. @command{gnatxref}
15417 and @command{gnatfind} will be able to locate these files by themselves using
15418 the source path. If you specify directories, no result is produced.
15423 The switches can be:
15427 @cindex @option{--version} @command{gnatxref}
15428 Display Copyright and version, then exit disregarding all other options.
15431 @cindex @option{--help} @command{gnatxref}
15432 If @option{--version} was not used, display usage, then exit disregarding
15435 @item ^-a^/ALL_FILES^
15436 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15437 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15438 the read-only files found in the library search path. Otherwise, these files
15439 will be ignored. This option can be used to protect Gnat sources or your own
15440 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15441 much faster, and their output much smaller. Read-only here refers to access
15442 or permissions status in the file system for the current user.
15445 @cindex @option{-aIDIR} (@command{gnatxref})
15446 When looking for source files also look in directory DIR. The order in which
15447 source file search is undertaken is the same as for @command{gnatmake}.
15450 @cindex @option{-aODIR} (@command{gnatxref})
15451 When searching for library and object files, look in directory
15452 DIR. The order in which library files are searched is the same as for
15453 @command{gnatmake}.
15456 @cindex @option{-nostdinc} (@command{gnatxref})
15457 Do not look for sources in the system default directory.
15460 @cindex @option{-nostdlib} (@command{gnatxref})
15461 Do not look for library files in the system default directory.
15463 @item --RTS=@var{rts-path}
15464 @cindex @option{--RTS} (@command{gnatxref})
15465 Specifies the default location of the runtime library. Same meaning as the
15466 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15468 @item ^-d^/DERIVED_TYPES^
15469 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15470 If this switch is set @code{gnatxref} will output the parent type
15471 reference for each matching derived types.
15473 @item ^-f^/FULL_PATHNAME^
15474 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15475 If this switch is set, the output file names will be preceded by their
15476 directory (if the file was found in the search path). If this switch is
15477 not set, the directory will not be printed.
15479 @item ^-g^/IGNORE_LOCALS^
15480 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15481 If this switch is set, information is output only for library-level
15482 entities, ignoring local entities. The use of this switch may accelerate
15483 @code{gnatfind} and @code{gnatxref}.
15486 @cindex @option{-IDIR} (@command{gnatxref})
15487 Equivalent to @samp{-aODIR -aIDIR}.
15490 @cindex @option{-pFILE} (@command{gnatxref})
15491 Specify a project file to use @xref{Project Files}.
15492 If you need to use the @file{.gpr}
15493 project files, you should use gnatxref through the GNAT driver
15494 (@command{gnat xref -Pproject}).
15496 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15497 project file in the current directory.
15499 If a project file is either specified or found by the tools, then the content
15500 of the source directory and object directory lines are added as if they
15501 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15502 and @samp{^-aO^OBJECT_SEARCH^}.
15504 Output only unused symbols. This may be really useful if you give your
15505 main compilation unit on the command line, as @code{gnatxref} will then
15506 display every unused entity and 'with'ed package.
15510 Instead of producing the default output, @code{gnatxref} will generate a
15511 @file{tags} file that can be used by vi. For examples how to use this
15512 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15513 to the standard output, thus you will have to redirect it to a file.
15519 All these switches may be in any order on the command line, and may even
15520 appear after the file names. They need not be separated by spaces, thus
15521 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15522 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15524 @node Switches for gnatfind
15525 @section @code{gnatfind} Switches
15528 The command line for @code{gnatfind} is:
15531 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15532 @r{[}@var{file1} @var{file2} @dots{}]
15540 An entity will be output only if it matches the regular expression found
15541 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15543 Omitting the pattern is equivalent to specifying @samp{*}, which
15544 will match any entity. Note that if you do not provide a pattern, you
15545 have to provide both a sourcefile and a line.
15547 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15548 for matching purposes. At the current time there is no support for
15549 8-bit codes other than Latin-1, or for wide characters in identifiers.
15552 @code{gnatfind} will look for references, bodies or declarations
15553 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15554 and column @var{column}. See @ref{Examples of gnatfind Usage}
15555 for syntax examples.
15558 is a decimal integer identifying the line number containing
15559 the reference to the entity (or entities) to be located.
15562 is a decimal integer identifying the exact location on the
15563 line of the first character of the identifier for the
15564 entity reference. Columns are numbered from 1.
15566 @item file1 file2 @dots{}
15567 The search will be restricted to these source files. If none are given, then
15568 the search will be done for every library file in the search path.
15569 These file must appear only after the pattern or sourcefile.
15571 These file names are considered to be regular expressions, so for instance
15572 specifying @file{source*.adb} is the same as giving every file in the current
15573 directory whose name starts with @file{source} and whose extension is
15576 The location of the spec of the entity will always be displayed, even if it
15577 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15578 occurrences of the entity in the separate units of the ones given on the
15579 command line will also be displayed.
15581 Note that if you specify at least one file in this part, @code{gnatfind} may
15582 sometimes not be able to find the body of the subprograms.
15587 At least one of 'sourcefile' or 'pattern' has to be present on
15590 The following switches are available:
15594 @cindex @option{--version} @command{gnatfind}
15595 Display Copyright and version, then exit disregarding all other options.
15598 @cindex @option{--help} @command{gnatfind}
15599 If @option{--version} was not used, display usage, then exit disregarding
15602 @item ^-a^/ALL_FILES^
15603 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15604 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15605 the read-only files found in the library search path. Otherwise, these files
15606 will be ignored. This option can be used to protect Gnat sources or your own
15607 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15608 much faster, and their output much smaller. Read-only here refers to access
15609 or permission status in the file system for the current user.
15612 @cindex @option{-aIDIR} (@command{gnatfind})
15613 When looking for source files also look in directory DIR. The order in which
15614 source file search is undertaken is the same as for @command{gnatmake}.
15617 @cindex @option{-aODIR} (@command{gnatfind})
15618 When searching for library and object files, look in directory
15619 DIR. The order in which library files are searched is the same as for
15620 @command{gnatmake}.
15623 @cindex @option{-nostdinc} (@command{gnatfind})
15624 Do not look for sources in the system default directory.
15627 @cindex @option{-nostdlib} (@command{gnatfind})
15628 Do not look for library files in the system default directory.
15630 @item --ext=@var{extension}
15631 @cindex @option{--ext} (@command{gnatfind})
15632 Specify an alternate ali file extension. The default is @code{ali} and other
15633 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
15634 switch. Note that if this switch overrides the default, which means that only
15635 the new extension will be considered.
15637 @item --RTS=@var{rts-path}
15638 @cindex @option{--RTS} (@command{gnatfind})
15639 Specifies the default location of the runtime library. Same meaning as the
15640 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15642 @item ^-d^/DERIVED_TYPE_INFORMATION^
15643 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15644 If this switch is set, then @code{gnatfind} will output the parent type
15645 reference for each matching derived types.
15647 @item ^-e^/EXPRESSIONS^
15648 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15649 By default, @code{gnatfind} accept the simple regular expression set for
15650 @samp{pattern}. If this switch is set, then the pattern will be
15651 considered as full Unix-style regular expression.
15653 @item ^-f^/FULL_PATHNAME^
15654 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15655 If this switch is set, the output file names will be preceded by their
15656 directory (if the file was found in the search path). If this switch is
15657 not set, the directory will not be printed.
15659 @item ^-g^/IGNORE_LOCALS^
15660 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15661 If this switch is set, information is output only for library-level
15662 entities, ignoring local entities. The use of this switch may accelerate
15663 @code{gnatfind} and @code{gnatxref}.
15666 @cindex @option{-IDIR} (@command{gnatfind})
15667 Equivalent to @samp{-aODIR -aIDIR}.
15670 @cindex @option{-pFILE} (@command{gnatfind})
15671 Specify a project file (@pxref{Project Files}) to use.
15672 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15673 project file in the current directory.
15675 If a project file is either specified or found by the tools, then the content
15676 of the source directory and object directory lines are added as if they
15677 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15678 @samp{^-aO^/OBJECT_SEARCH^}.
15680 @item ^-r^/REFERENCES^
15681 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15682 By default, @code{gnatfind} will output only the information about the
15683 declaration, body or type completion of the entities. If this switch is
15684 set, the @code{gnatfind} will locate every reference to the entities in
15685 the files specified on the command line (or in every file in the search
15686 path if no file is given on the command line).
15688 @item ^-s^/PRINT_LINES^
15689 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15690 If this switch is set, then @code{gnatfind} will output the content
15691 of the Ada source file lines were the entity was found.
15693 @item ^-t^/TYPE_HIERARCHY^
15694 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15695 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15696 the specified type. It act like -d option but recursively from parent
15697 type to parent type. When this switch is set it is not possible to
15698 specify more than one file.
15703 All these switches may be in any order on the command line, and may even
15704 appear after the file names. They need not be separated by spaces, thus
15705 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15706 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15708 As stated previously, gnatfind will search in every directory in the
15709 search path. You can force it to look only in the current directory if
15710 you specify @code{*} at the end of the command line.
15712 @node Project Files for gnatxref and gnatfind
15713 @section Project Files for @command{gnatxref} and @command{gnatfind}
15716 Project files allow a programmer to specify how to compile its
15717 application, where to find sources, etc. These files are used
15719 primarily by GPS, but they can also be used
15722 @code{gnatxref} and @code{gnatfind}.
15724 A project file name must end with @file{.gpr}. If a single one is
15725 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15726 extract the information from it. If multiple project files are found, none of
15727 them is read, and you have to use the @samp{-p} switch to specify the one
15730 The following lines can be included, even though most of them have default
15731 values which can be used in most cases.
15732 The lines can be entered in any order in the file.
15733 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15734 each line. If you have multiple instances, only the last one is taken into
15739 [default: @code{"^./^[]^"}]
15740 specifies a directory where to look for source files. Multiple @code{src_dir}
15741 lines can be specified and they will be searched in the order they
15745 [default: @code{"^./^[]^"}]
15746 specifies a directory where to look for object and library files. Multiple
15747 @code{obj_dir} lines can be specified, and they will be searched in the order
15750 @item comp_opt=SWITCHES
15751 [default: @code{""}]
15752 creates a variable which can be referred to subsequently by using
15753 the @code{$@{comp_opt@}} notation. This is intended to store the default
15754 switches given to @command{gnatmake} and @command{gcc}.
15756 @item bind_opt=SWITCHES
15757 [default: @code{""}]
15758 creates a variable which can be referred to subsequently by using
15759 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15760 switches given to @command{gnatbind}.
15762 @item link_opt=SWITCHES
15763 [default: @code{""}]
15764 creates a variable which can be referred to subsequently by using
15765 the @samp{$@{link_opt@}} notation. This is intended to store the default
15766 switches given to @command{gnatlink}.
15768 @item main=EXECUTABLE
15769 [default: @code{""}]
15770 specifies the name of the executable for the application. This variable can
15771 be referred to in the following lines by using the @samp{$@{main@}} notation.
15774 @item comp_cmd=COMMAND
15775 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15778 @item comp_cmd=COMMAND
15779 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15781 specifies the command used to compile a single file in the application.
15784 @item make_cmd=COMMAND
15785 [default: @code{"GNAT MAKE $@{main@}
15786 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15787 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15788 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15791 @item make_cmd=COMMAND
15792 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15793 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15794 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15796 specifies the command used to recompile the whole application.
15798 @item run_cmd=COMMAND
15799 [default: @code{"$@{main@}"}]
15800 specifies the command used to run the application.
15802 @item debug_cmd=COMMAND
15803 [default: @code{"gdb $@{main@}"}]
15804 specifies the command used to debug the application
15809 @command{gnatxref} and @command{gnatfind} only take into account the
15810 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15812 @node Regular Expressions in gnatfind and gnatxref
15813 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15816 As specified in the section about @command{gnatfind}, the pattern can be a
15817 regular expression. Actually, there are to set of regular expressions
15818 which are recognized by the program:
15821 @item globbing patterns
15822 These are the most usual regular expression. They are the same that you
15823 generally used in a Unix shell command line, or in a DOS session.
15825 Here is a more formal grammar:
15832 term ::= elmt -- matches elmt
15833 term ::= elmt elmt -- concatenation (elmt then elmt)
15834 term ::= * -- any string of 0 or more characters
15835 term ::= ? -- matches any character
15836 term ::= [char @{char@}] -- matches any character listed
15837 term ::= [char - char] -- matches any character in range
15841 @item full regular expression
15842 The second set of regular expressions is much more powerful. This is the
15843 type of regular expressions recognized by utilities such a @file{grep}.
15845 The following is the form of a regular expression, expressed in Ada
15846 reference manual style BNF is as follows
15853 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15855 term ::= item @{item@} -- concatenation (item then item)
15857 item ::= elmt -- match elmt
15858 item ::= elmt * -- zero or more elmt's
15859 item ::= elmt + -- one or more elmt's
15860 item ::= elmt ? -- matches elmt or nothing
15863 elmt ::= nschar -- matches given character
15864 elmt ::= [nschar @{nschar@}] -- matches any character listed
15865 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15866 elmt ::= [char - char] -- matches chars in given range
15867 elmt ::= \ char -- matches given character
15868 elmt ::= . -- matches any single character
15869 elmt ::= ( regexp ) -- parens used for grouping
15871 char ::= any character, including special characters
15872 nschar ::= any character except ()[].*+?^^^
15876 Following are a few examples:
15880 will match any of the two strings @samp{abcde} and @samp{fghi},
15883 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15884 @samp{abcccd}, and so on,
15887 will match any string which has only lowercase characters in it (and at
15888 least one character.
15893 @node Examples of gnatxref Usage
15894 @section Examples of @code{gnatxref} Usage
15896 @subsection General Usage
15899 For the following examples, we will consider the following units:
15901 @smallexample @c ada
15907 3: procedure Foo (B : in Integer);
15914 1: package body Main is
15915 2: procedure Foo (B : in Integer) is
15926 2: procedure Print (B : Integer);
15935 The first thing to do is to recompile your application (for instance, in
15936 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15937 the cross-referencing information.
15938 You can then issue any of the following commands:
15940 @item gnatxref main.adb
15941 @code{gnatxref} generates cross-reference information for main.adb
15942 and every unit 'with'ed by main.adb.
15944 The output would be:
15952 Decl: main.ads 3:20
15953 Body: main.adb 2:20
15954 Ref: main.adb 4:13 5:13 6:19
15957 Ref: main.adb 6:8 7:8
15967 Decl: main.ads 3:15
15968 Body: main.adb 2:15
15971 Body: main.adb 1:14
15974 Ref: main.adb 6:12 7:12
15978 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15979 its body is in main.adb, line 1, column 14 and is not referenced any where.
15981 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15982 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15984 @item gnatxref package1.adb package2.ads
15985 @code{gnatxref} will generates cross-reference information for
15986 package1.adb, package2.ads and any other package 'with'ed by any
15992 @subsection Using gnatxref with vi
15994 @code{gnatxref} can generate a tags file output, which can be used
15995 directly from @command{vi}. Note that the standard version of @command{vi}
15996 will not work properly with overloaded symbols. Consider using another
15997 free implementation of @command{vi}, such as @command{vim}.
16000 $ gnatxref -v gnatfind.adb > tags
16004 will generate the tags file for @code{gnatfind} itself (if the sources
16005 are in the search path!).
16007 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
16008 (replacing @var{entity} by whatever you are looking for), and vi will
16009 display a new file with the corresponding declaration of entity.
16012 @node Examples of gnatfind Usage
16013 @section Examples of @code{gnatfind} Usage
16017 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
16018 Find declarations for all entities xyz referenced at least once in
16019 main.adb. The references are search in every library file in the search
16022 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
16025 The output will look like:
16027 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
16028 ^directory/^[directory]^main.adb:24:10: xyz <= body
16029 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
16033 that is to say, one of the entities xyz found in main.adb is declared at
16034 line 12 of main.ads (and its body is in main.adb), and another one is
16035 declared at line 45 of foo.ads
16037 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
16038 This is the same command as the previous one, instead @code{gnatfind} will
16039 display the content of the Ada source file lines.
16041 The output will look like:
16044 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
16046 ^directory/^[directory]^main.adb:24:10: xyz <= body
16048 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
16053 This can make it easier to find exactly the location your are looking
16056 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
16057 Find references to all entities containing an x that are
16058 referenced on line 123 of main.ads.
16059 The references will be searched only in main.ads and foo.adb.
16061 @item gnatfind main.ads:123
16062 Find declarations and bodies for all entities that are referenced on
16063 line 123 of main.ads.
16065 This is the same as @code{gnatfind "*":main.adb:123}.
16067 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
16068 Find the declaration for the entity referenced at column 45 in
16069 line 123 of file main.adb in directory mydir. Note that it
16070 is usual to omit the identifier name when the column is given,
16071 since the column position identifies a unique reference.
16073 The column has to be the beginning of the identifier, and should not
16074 point to any character in the middle of the identifier.
16078 @c *********************************
16079 @node The GNAT Pretty-Printer gnatpp
16080 @chapter The GNAT Pretty-Printer @command{gnatpp}
16082 @cindex Pretty-Printer
16085 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
16086 for source reformatting / pretty-printing.
16087 It takes an Ada source file as input and generates a reformatted
16089 You can specify various style directives via switches; e.g.,
16090 identifier case conventions, rules of indentation, and comment layout.
16092 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
16093 tree for the input source and thus requires the input to be syntactically and
16094 semantically legal.
16095 If this condition is not met, @command{gnatpp} will terminate with an
16096 error message; no output file will be generated.
16098 If the source files presented to @command{gnatpp} contain
16099 preprocessing directives, then the output file will
16100 correspond to the generated source after all
16101 preprocessing is carried out. There is no way
16102 using @command{gnatpp} to obtain pretty printed files that
16103 include the preprocessing directives.
16105 If the compilation unit
16106 contained in the input source depends semantically upon units located
16107 outside the current directory, you have to provide the source search path
16108 when invoking @command{gnatpp}, if these units are contained in files with
16109 names that do not follow the GNAT file naming rules, you have to provide
16110 the configuration file describing the corresponding naming scheme;
16111 see the description of the @command{gnatpp}
16112 switches below. Another possibility is to use a project file and to
16113 call @command{gnatpp} through the @command{gnat} driver
16115 The @command{gnatpp} command has the form
16118 $ gnatpp @ovar{switches} @var{filename}
16125 @var{switches} is an optional sequence of switches defining such properties as
16126 the formatting rules, the source search path, and the destination for the
16130 @var{filename} is the name (including the extension) of the source file to
16131 reformat; ``wildcards'' or several file names on the same gnatpp command are
16132 allowed. The file name may contain path information; it does not have to
16133 follow the GNAT file naming rules
16137 * Switches for gnatpp::
16138 * Formatting Rules::
16141 @node Switches for gnatpp
16142 @section Switches for @command{gnatpp}
16145 The following subsections describe the various switches accepted by
16146 @command{gnatpp}, organized by category.
16149 You specify a switch by supplying a name and generally also a value.
16150 In many cases the values for a switch with a given name are incompatible with
16152 (for example the switch that controls the casing of a reserved word may have
16153 exactly one value: upper case, lower case, or
16154 mixed case) and thus exactly one such switch can be in effect for an
16155 invocation of @command{gnatpp}.
16156 If more than one is supplied, the last one is used.
16157 However, some values for the same switch are mutually compatible.
16158 You may supply several such switches to @command{gnatpp}, but then
16159 each must be specified in full, with both the name and the value.
16160 Abbreviated forms (the name appearing once, followed by each value) are
16162 For example, to set
16163 the alignment of the assignment delimiter both in declarations and in
16164 assignment statements, you must write @option{-A2A3}
16165 (or @option{-A2 -A3}), but not @option{-A23}.
16169 In many cases the set of options for a given qualifier are incompatible with
16170 each other (for example the qualifier that controls the casing of a reserved
16171 word may have exactly one option, which specifies either upper case, lower
16172 case, or mixed case), and thus exactly one such option can be in effect for
16173 an invocation of @command{gnatpp}.
16174 If more than one is supplied, the last one is used.
16175 However, some qualifiers have options that are mutually compatible,
16176 and then you may then supply several such options when invoking
16180 In most cases, it is obvious whether or not the
16181 ^values for a switch with a given name^options for a given qualifier^
16182 are compatible with each other.
16183 When the semantics might not be evident, the summaries below explicitly
16184 indicate the effect.
16187 * Alignment Control::
16189 * Construct Layout Control::
16190 * General Text Layout Control::
16191 * Other Formatting Options::
16192 * Setting the Source Search Path::
16193 * Output File Control::
16194 * Other gnatpp Switches::
16197 @node Alignment Control
16198 @subsection Alignment Control
16199 @cindex Alignment control in @command{gnatpp}
16202 Programs can be easier to read if certain constructs are vertically aligned.
16203 By default all alignments are set ON.
16204 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16205 OFF, and then use one or more of the other
16206 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16207 to activate alignment for specific constructs.
16210 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16214 Set all alignments to ON
16217 @item ^-A0^/ALIGN=OFF^
16218 Set all alignments to OFF
16220 @item ^-A1^/ALIGN=COLONS^
16221 Align @code{:} in declarations
16223 @item ^-A2^/ALIGN=DECLARATIONS^
16224 Align @code{:=} in initializations in declarations
16226 @item ^-A3^/ALIGN=STATEMENTS^
16227 Align @code{:=} in assignment statements
16229 @item ^-A4^/ALIGN=ARROWS^
16230 Align @code{=>} in associations
16232 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16233 Align @code{at} keywords in the component clauses in record
16234 representation clauses
16238 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16241 @node Casing Control
16242 @subsection Casing Control
16243 @cindex Casing control in @command{gnatpp}
16246 @command{gnatpp} allows you to specify the casing for reserved words,
16247 pragma names, attribute designators and identifiers.
16248 For identifiers you may define a
16249 general rule for name casing but also override this rule
16250 via a set of dictionary files.
16252 Three types of casing are supported: lower case, upper case, and mixed case.
16253 Lower and upper case are self-explanatory (but since some letters in
16254 Latin1 and other GNAT-supported character sets
16255 exist only in lower-case form, an upper case conversion will have no
16257 ``Mixed case'' means that the first letter, and also each letter immediately
16258 following an underscore, are converted to their uppercase forms;
16259 all the other letters are converted to their lowercase forms.
16262 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16263 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16264 Attribute designators are lower case
16266 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16267 Attribute designators are upper case
16269 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16270 Attribute designators are mixed case (this is the default)
16272 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16273 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16274 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16275 lower case (this is the default)
16277 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16278 Keywords are upper case
16280 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16281 @item ^-nD^/NAME_CASING=AS_DECLARED^
16282 Name casing for defining occurrences are as they appear in the source file
16283 (this is the default)
16285 @item ^-nU^/NAME_CASING=UPPER_CASE^
16286 Names are in upper case
16288 @item ^-nL^/NAME_CASING=LOWER_CASE^
16289 Names are in lower case
16291 @item ^-nM^/NAME_CASING=MIXED_CASE^
16292 Names are in mixed case
16294 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16295 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16296 Pragma names are lower case
16298 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16299 Pragma names are upper case
16301 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16302 Pragma names are mixed case (this is the default)
16304 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16305 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16306 Use @var{file} as a @emph{dictionary file} that defines
16307 the casing for a set of specified names,
16308 thereby overriding the effect on these names by
16309 any explicit or implicit
16310 ^-n^/NAME_CASING^ switch.
16311 To supply more than one dictionary file,
16312 use ^several @option{-D} switches^a list of files as options^.
16315 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16316 to define the casing for the Ada predefined names and
16317 the names declared in the GNAT libraries.
16319 @item ^-D-^/SPECIFIC_CASING^
16320 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16321 Do not use the default dictionary file;
16322 instead, use the casing
16323 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16328 The structure of a dictionary file, and details on the conventions
16329 used in the default dictionary file, are defined in @ref{Name Casing}.
16331 The @option{^-D-^/SPECIFIC_CASING^} and
16332 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16335 @node Construct Layout Control
16336 @subsection Construct Layout Control
16337 @cindex Layout control in @command{gnatpp}
16340 This group of @command{gnatpp} switches controls the layout of comments and
16341 complex syntactic constructs. See @ref{Formatting Comments} for details
16345 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16346 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16347 All the comments remain unchanged
16349 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16350 GNAT-style comment line indentation (this is the default).
16352 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16353 Reference-manual comment line indentation.
16355 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16356 GNAT-style comment beginning
16358 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16359 Reformat comment blocks
16361 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16362 Keep unchanged special form comments
16364 Reformat comment blocks
16366 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16367 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16368 GNAT-style layout (this is the default)
16370 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16373 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16376 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16378 All the VT characters are removed from the comment text. All the HT characters
16379 are expanded with the sequences of space characters to get to the next tab
16382 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16383 @item ^--no-separate-is^/NO_SEPARATE_IS^
16384 Do not place the keyword @code{is} on a separate line in a subprogram body in
16385 case if the spec occupies more then one line.
16387 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
16388 @item ^--separate-label^/SEPARATE_LABEL^
16389 Place statement label(s) on a separate line, with the following statement
16392 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16393 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16394 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16395 keyword @code{then} in IF statements on a separate line.
16397 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16398 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16399 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16400 keyword @code{then} in IF statements on a separate line. This option is
16401 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16403 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16404 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16405 Start each USE clause in a context clause from a separate line.
16407 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16408 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16409 Use a separate line for a loop or block statement name, but do not use an extra
16410 indentation level for the statement itself.
16416 The @option{-c1} and @option{-c2} switches are incompatible.
16417 The @option{-c3} and @option{-c4} switches are compatible with each other and
16418 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16419 the other comment formatting switches.
16421 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16426 For the @option{/COMMENTS_LAYOUT} qualifier:
16429 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16431 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16432 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16436 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16437 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16440 @node General Text Layout Control
16441 @subsection General Text Layout Control
16444 These switches allow control over line length and indentation.
16447 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16448 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16449 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16451 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16452 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16453 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16455 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16456 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16457 Indentation level for continuation lines (relative to the line being
16458 continued), @var{nnn} from 1@dots{}9.
16460 value is one less then the (normal) indentation level, unless the
16461 indentation is set to 1 (in which case the default value for continuation
16462 line indentation is also 1)
16465 @node Other Formatting Options
16466 @subsection Other Formatting Options
16469 These switches control the inclusion of missing end/exit labels, and
16470 the indentation level in @b{case} statements.
16473 @item ^-e^/NO_MISSED_LABELS^
16474 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16475 Do not insert missing end/exit labels. An end label is the name of
16476 a construct that may optionally be repeated at the end of the
16477 construct's declaration;
16478 e.g., the names of packages, subprograms, and tasks.
16479 An exit label is the name of a loop that may appear as target
16480 of an exit statement within the loop.
16481 By default, @command{gnatpp} inserts these end/exit labels when
16482 they are absent from the original source. This option suppresses such
16483 insertion, so that the formatted source reflects the original.
16485 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16486 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16487 Insert a Form Feed character after a pragma Page.
16489 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16490 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16491 Do not use an additional indentation level for @b{case} alternatives
16492 and variants if there are @var{nnn} or more (the default
16494 If @var{nnn} is 0, an additional indentation level is
16495 used for @b{case} alternatives and variants regardless of their number.
16498 @node Setting the Source Search Path
16499 @subsection Setting the Source Search Path
16502 To define the search path for the input source file, @command{gnatpp}
16503 uses the same switches as the GNAT compiler, with the same effects.
16506 @item ^-I^/SEARCH=^@var{dir}
16507 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16508 The same as the corresponding gcc switch
16510 @item ^-I-^/NOCURRENT_DIRECTORY^
16511 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16512 The same as the corresponding gcc switch
16514 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16515 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16516 The same as the corresponding gcc switch
16518 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16519 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16520 The same as the corresponding gcc switch
16524 @node Output File Control
16525 @subsection Output File Control
16528 By default the output is sent to the file whose name is obtained by appending
16529 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16530 (if the file with this name already exists, it is unconditionally overwritten).
16531 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16532 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16534 The output may be redirected by the following switches:
16537 @item ^-pipe^/STANDARD_OUTPUT^
16538 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16539 Send the output to @code{Standard_Output}
16541 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16542 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16543 Write the output into @var{output_file}.
16544 If @var{output_file} already exists, @command{gnatpp} terminates without
16545 reading or processing the input file.
16547 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16548 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16549 Write the output into @var{output_file}, overwriting the existing file
16550 (if one is present).
16552 @item ^-r^/REPLACE^
16553 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16554 Replace the input source file with the reformatted output, and copy the
16555 original input source into the file whose name is obtained by appending the
16556 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16557 If a file with this name already exists, @command{gnatpp} terminates without
16558 reading or processing the input file.
16560 @item ^-rf^/OVERRIDING_REPLACE^
16561 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16562 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16563 already exists, it is overwritten.
16565 @item ^-rnb^/REPLACE_NO_BACKUP^
16566 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16567 Replace the input source file with the reformatted output without
16568 creating any backup copy of the input source.
16570 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16571 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16572 Specifies the format of the reformatted output file. The @var{xxx}
16573 ^string specified with the switch^option^ may be either
16575 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16576 @item ``@option{^crlf^CRLF^}''
16577 the same as @option{^crlf^CRLF^}
16578 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16579 @item ``@option{^lf^LF^}''
16580 the same as @option{^unix^UNIX^}
16583 @item ^-W^/RESULT_ENCODING=^@var{e}
16584 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16585 Specify the wide character encoding method used to write the code in the
16587 @var{e} is one of the following:
16595 Upper half encoding
16597 @item ^s^SHIFT_JIS^
16607 Brackets encoding (default value)
16613 Options @option{^-pipe^/STANDARD_OUTPUT^},
16614 @option{^-o^/OUTPUT^} and
16615 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16616 contains only one file to reformat.
16618 @option{^--eol^/END_OF_LINE^}
16620 @option{^-W^/RESULT_ENCODING^}
16621 cannot be used together
16622 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16624 @node Other gnatpp Switches
16625 @subsection Other @code{gnatpp} Switches
16628 The additional @command{gnatpp} switches are defined in this subsection.
16631 @item ^-files @var{filename}^/FILES=@var{output_file}^
16632 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16633 Take the argument source files from the specified file. This file should be an
16634 ordinary textual file containing file names separated by spaces or
16635 line breaks. You can use this switch more then once in the same call to
16636 @command{gnatpp}. You also can combine this switch with explicit list of
16639 @item ^-v^/VERBOSE^
16640 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16642 @command{gnatpp} generates version information and then
16643 a trace of the actions it takes to produce or obtain the ASIS tree.
16645 @item ^-w^/WARNINGS^
16646 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16648 @command{gnatpp} generates a warning whenever it cannot provide
16649 a required layout in the result source.
16652 @node Formatting Rules
16653 @section Formatting Rules
16656 The following subsections show how @command{gnatpp} treats ``white space'',
16657 comments, program layout, and name casing.
16658 They provide the detailed descriptions of the switches shown above.
16661 * White Space and Empty Lines::
16662 * Formatting Comments::
16663 * Construct Layout::
16667 @node White Space and Empty Lines
16668 @subsection White Space and Empty Lines
16671 @command{gnatpp} does not have an option to control space characters.
16672 It will add or remove spaces according to the style illustrated by the
16673 examples in the @cite{Ada Reference Manual}.
16675 The only format effectors
16676 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16677 that will appear in the output file are platform-specific line breaks,
16678 and also format effectors within (but not at the end of) comments.
16679 In particular, each horizontal tab character that is not inside
16680 a comment will be treated as a space and thus will appear in the
16681 output file as zero or more spaces depending on
16682 the reformatting of the line in which it appears.
16683 The only exception is a Form Feed character, which is inserted after a
16684 pragma @code{Page} when @option{-ff} is set.
16686 The output file will contain no lines with trailing ``white space'' (spaces,
16689 Empty lines in the original source are preserved
16690 only if they separate declarations or statements.
16691 In such contexts, a
16692 sequence of two or more empty lines is replaced by exactly one empty line.
16693 Note that a blank line will be removed if it separates two ``comment blocks''
16694 (a comment block is a sequence of whole-line comments).
16695 In order to preserve a visual separation between comment blocks, use an
16696 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16697 Likewise, if for some reason you wish to have a sequence of empty lines,
16698 use a sequence of empty comments instead.
16700 @node Formatting Comments
16701 @subsection Formatting Comments
16704 Comments in Ada code are of two kinds:
16707 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16708 ``white space'') on a line
16711 an @emph{end-of-line comment}, which follows some other Ada lexical element
16716 The indentation of a whole-line comment is that of either
16717 the preceding or following line in
16718 the formatted source, depending on switch settings as will be described below.
16720 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16721 between the end of the preceding Ada lexical element and the beginning
16722 of the comment as appear in the original source,
16723 unless either the comment has to be split to
16724 satisfy the line length limitation, or else the next line contains a
16725 whole line comment that is considered a continuation of this end-of-line
16726 comment (because it starts at the same position).
16728 cases, the start of the end-of-line comment is moved right to the nearest
16729 multiple of the indentation level.
16730 This may result in a ``line overflow'' (the right-shifted comment extending
16731 beyond the maximum line length), in which case the comment is split as
16734 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16735 (GNAT-style comment line indentation)
16736 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16737 (reference-manual comment line indentation).
16738 With reference-manual style, a whole-line comment is indented as if it
16739 were a declaration or statement at the same place
16740 (i.e., according to the indentation of the preceding line(s)).
16741 With GNAT style, a whole-line comment that is immediately followed by an
16742 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16743 word @b{begin}, is indented based on the construct that follows it.
16746 @smallexample @c ada
16758 Reference-manual indentation produces:
16760 @smallexample @c ada
16772 while GNAT-style indentation produces:
16774 @smallexample @c ada
16786 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16787 (GNAT style comment beginning) has the following
16792 For each whole-line comment that does not end with two hyphens,
16793 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16794 to ensure that there are at least two spaces between these hyphens and the
16795 first non-blank character of the comment.
16799 For an end-of-line comment, if in the original source the next line is a
16800 whole-line comment that starts at the same position
16801 as the end-of-line comment,
16802 then the whole-line comment (and all whole-line comments
16803 that follow it and that start at the same position)
16804 will start at this position in the output file.
16807 That is, if in the original source we have:
16809 @smallexample @c ada
16812 A := B + C; -- B must be in the range Low1..High1
16813 -- C must be in the range Low2..High2
16814 --B+C will be in the range Low1+Low2..High1+High2
16820 Then in the formatted source we get
16822 @smallexample @c ada
16825 A := B + C; -- B must be in the range Low1..High1
16826 -- C must be in the range Low2..High2
16827 -- B+C will be in the range Low1+Low2..High1+High2
16833 A comment that exceeds the line length limit will be split.
16835 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16836 the line belongs to a reformattable block, splitting the line generates a
16837 @command{gnatpp} warning.
16838 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16839 comments may be reformatted in typical
16840 word processor style (that is, moving words between lines and putting as
16841 many words in a line as possible).
16844 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16845 that has a special format (that is, a character that is neither a letter nor digit
16846 not white space nor line break immediately following the leading @code{--} of
16847 the comment) should be without any change moved from the argument source
16848 into reformatted source. This switch allows to preserve comments that are used
16849 as a special marks in the code (e.g.@: SPARK annotation).
16851 @node Construct Layout
16852 @subsection Construct Layout
16855 In several cases the suggested layout in the Ada Reference Manual includes
16856 an extra level of indentation that many programmers prefer to avoid. The
16857 affected cases include:
16861 @item Record type declaration (RM 3.8)
16863 @item Record representation clause (RM 13.5.1)
16865 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16867 @item Block statement in case if a block has a statement identifier (RM 5.6)
16871 In compact mode (when GNAT style layout or compact layout is set),
16872 the pretty printer uses one level of indentation instead
16873 of two. This is achieved in the record definition and record representation
16874 clause cases by putting the @code{record} keyword on the same line as the
16875 start of the declaration or representation clause, and in the block and loop
16876 case by putting the block or loop header on the same line as the statement
16880 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16881 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16882 layout on the one hand, and uncompact layout
16883 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16884 can be illustrated by the following examples:
16888 @multitable @columnfractions .5 .5
16889 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16892 @smallexample @c ada
16899 @smallexample @c ada
16908 @smallexample @c ada
16910 a at 0 range 0 .. 31;
16911 b at 4 range 0 .. 31;
16915 @smallexample @c ada
16918 a at 0 range 0 .. 31;
16919 b at 4 range 0 .. 31;
16924 @smallexample @c ada
16932 @smallexample @c ada
16942 @smallexample @c ada
16943 Clear : for J in 1 .. 10 loop
16948 @smallexample @c ada
16950 for J in 1 .. 10 loop
16961 GNAT style, compact layout Uncompact layout
16963 type q is record type q is
16964 a : integer; record
16965 b : integer; a : integer;
16966 end record; b : integer;
16969 for q use record for q use
16970 a at 0 range 0 .. 31; record
16971 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16972 end record; b at 4 range 0 .. 31;
16975 Block : declare Block :
16976 A : Integer := 3; declare
16977 begin A : Integer := 3;
16979 end Block; Proc (A, A);
16982 Clear : for J in 1 .. 10 loop Clear :
16983 A (J) := 0; for J in 1 .. 10 loop
16984 end loop Clear; A (J) := 0;
16991 A further difference between GNAT style layout and compact layout is that
16992 GNAT style layout inserts empty lines as separation for
16993 compound statements, return statements and bodies.
16995 Note that the layout specified by
16996 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16997 for named block and loop statements overrides the layout defined by these
16998 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16999 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
17000 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
17003 @subsection Name Casing
17006 @command{gnatpp} always converts the usage occurrence of a (simple) name to
17007 the same casing as the corresponding defining identifier.
17009 You control the casing for defining occurrences via the
17010 @option{^-n^/NAME_CASING^} switch.
17012 With @option{-nD} (``as declared'', which is the default),
17015 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
17017 defining occurrences appear exactly as in the source file
17018 where they are declared.
17019 The other ^values for this switch^options for this qualifier^ ---
17020 @option{^-nU^UPPER_CASE^},
17021 @option{^-nL^LOWER_CASE^},
17022 @option{^-nM^MIXED_CASE^} ---
17024 ^upper, lower, or mixed case, respectively^the corresponding casing^.
17025 If @command{gnatpp} changes the casing of a defining
17026 occurrence, it analogously changes the casing of all the
17027 usage occurrences of this name.
17029 If the defining occurrence of a name is not in the source compilation unit
17030 currently being processed by @command{gnatpp}, the casing of each reference to
17031 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
17032 switch (subject to the dictionary file mechanism described below).
17033 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
17035 casing for the defining occurrence of the name.
17037 Some names may need to be spelled with casing conventions that are not
17038 covered by the upper-, lower-, and mixed-case transformations.
17039 You can arrange correct casing by placing such names in a
17040 @emph{dictionary file},
17041 and then supplying a @option{^-D^/DICTIONARY^} switch.
17042 The casing of names from dictionary files overrides
17043 any @option{^-n^/NAME_CASING^} switch.
17045 To handle the casing of Ada predefined names and the names from GNAT libraries,
17046 @command{gnatpp} assumes a default dictionary file.
17047 The name of each predefined entity is spelled with the same casing as is used
17048 for the entity in the @cite{Ada Reference Manual}.
17049 The name of each entity in the GNAT libraries is spelled with the same casing
17050 as is used in the declaration of that entity.
17052 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
17053 default dictionary file.
17054 Instead, the casing for predefined and GNAT-defined names will be established
17055 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
17056 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
17057 will appear as just shown,
17058 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
17059 To ensure that even such names are rendered in uppercase,
17060 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
17061 (or else, less conveniently, place these names in upper case in a dictionary
17064 A dictionary file is
17065 a plain text file; each line in this file can be either a blank line
17066 (containing only space characters and ASCII.HT characters), an Ada comment
17067 line, or the specification of exactly one @emph{casing schema}.
17069 A casing schema is a string that has the following syntax:
17073 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
17075 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
17080 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
17081 @var{identifier} lexical element and the @var{letter_or_digit} category.)
17083 The casing schema string can be followed by white space and/or an Ada-style
17084 comment; any amount of white space is allowed before the string.
17086 If a dictionary file is passed as
17088 the value of a @option{-D@var{file}} switch
17091 an option to the @option{/DICTIONARY} qualifier
17094 simple name and every identifier, @command{gnatpp} checks if the dictionary
17095 defines the casing for the name or for some of its parts (the term ``subword''
17096 is used below to denote the part of a name which is delimited by ``_'' or by
17097 the beginning or end of the word and which does not contain any ``_'' inside):
17101 if the whole name is in the dictionary, @command{gnatpp} uses for this name
17102 the casing defined by the dictionary; no subwords are checked for this word
17105 for every subword @command{gnatpp} checks if the dictionary contains the
17106 corresponding string of the form @code{*@var{simple_identifier}*},
17107 and if it does, the casing of this @var{simple_identifier} is used
17111 if the whole name does not contain any ``_'' inside, and if for this name
17112 the dictionary contains two entries - one of the form @var{identifier},
17113 and another - of the form *@var{simple_identifier}*, then the first one
17114 is applied to define the casing of this name
17117 if more than one dictionary file is passed as @command{gnatpp} switches, each
17118 dictionary adds new casing exceptions and overrides all the existing casing
17119 exceptions set by the previous dictionaries
17122 when @command{gnatpp} checks if the word or subword is in the dictionary,
17123 this check is not case sensitive
17127 For example, suppose we have the following source to reformat:
17129 @smallexample @c ada
17132 name1 : integer := 1;
17133 name4_name3_name2 : integer := 2;
17134 name2_name3_name4 : Boolean;
17137 name2_name3_name4 := name4_name3_name2 > name1;
17143 And suppose we have two dictionaries:
17160 If @command{gnatpp} is called with the following switches:
17164 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17167 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17172 then we will get the following name casing in the @command{gnatpp} output:
17174 @smallexample @c ada
17177 NAME1 : Integer := 1;
17178 Name4_NAME3_Name2 : Integer := 2;
17179 Name2_NAME3_Name4 : Boolean;
17182 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17187 @c *********************************
17188 @node The GNAT Metric Tool gnatmetric
17189 @chapter The GNAT Metric Tool @command{gnatmetric}
17191 @cindex Metric tool
17194 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17195 for computing various program metrics.
17196 It takes an Ada source file as input and generates a file containing the
17197 metrics data as output. Various switches control which
17198 metrics are computed and output.
17200 @command{gnatmetric} generates and uses the ASIS
17201 tree for the input source and thus requires the input to be syntactically and
17202 semantically legal.
17203 If this condition is not met, @command{gnatmetric} will generate
17204 an error message; no metric information for this file will be
17205 computed and reported.
17207 If the compilation unit contained in the input source depends semantically
17208 upon units in files located outside the current directory, you have to provide
17209 the source search path when invoking @command{gnatmetric}.
17210 If it depends semantically upon units that are contained
17211 in files with names that do not follow the GNAT file naming rules, you have to
17212 provide the configuration file describing the corresponding naming scheme (see
17213 the description of the @command{gnatmetric} switches below.)
17214 Alternatively, you may use a project file and invoke @command{gnatmetric}
17215 through the @command{gnat} driver.
17217 The @command{gnatmetric} command has the form
17220 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17227 @var{switches} specify the metrics to compute and define the destination for
17231 Each @var{filename} is the name (including the extension) of a source
17232 file to process. ``Wildcards'' are allowed, and
17233 the file name may contain path information.
17234 If no @var{filename} is supplied, then the @var{switches} list must contain
17236 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17237 Including both a @option{-files} switch and one or more
17238 @var{filename} arguments is permitted.
17241 @samp{-cargs @var{gcc_switches}} is a list of switches for
17242 @command{gcc}. They will be passed on to all compiler invocations made by
17243 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17244 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17245 and use the @option{-gnatec} switch to set the configuration file.
17249 * Switches for gnatmetric::
17252 @node Switches for gnatmetric
17253 @section Switches for @command{gnatmetric}
17256 The following subsections describe the various switches accepted by
17257 @command{gnatmetric}, organized by category.
17260 * Output Files Control::
17261 * Disable Metrics For Local Units::
17262 * Specifying a set of metrics to compute::
17263 * Other gnatmetric Switches::
17264 * Generate project-wide metrics::
17267 @node Output Files Control
17268 @subsection Output File Control
17269 @cindex Output file control in @command{gnatmetric}
17272 @command{gnatmetric} has two output formats. It can generate a
17273 textual (human-readable) form, and also XML. By default only textual
17274 output is generated.
17276 When generating the output in textual form, @command{gnatmetric} creates
17277 for each Ada source file a corresponding text file
17278 containing the computed metrics, except for the case when the set of metrics
17279 specified by gnatmetric parameters consists only of metrics that are computed
17280 for the whole set of analyzed sources, but not for each Ada source.
17281 By default, this file is placed in the same directory as where the source
17282 file is located, and its name is obtained
17283 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17286 All the output information generated in XML format is placed in a single
17287 file. By default this file is placed in the current directory and has the
17288 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17290 Some of the computed metrics are summed over the units passed to
17291 @command{gnatmetric}; for example, the total number of lines of code.
17292 By default this information is sent to @file{stdout}, but a file
17293 can be specified with the @option{-og} switch.
17295 The following switches control the @command{gnatmetric} output:
17298 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17300 Generate the XML output
17302 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17304 Generate the XML output and the XML schema file that describes the structure
17305 of the XML metric report, this schema is assigned to the XML file. The schema
17306 file has the same name as the XML output file with @file{.xml} suffix replaced
17309 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17310 @item ^-nt^/NO_TEXT^
17311 Do not generate the output in text form (implies @option{^-x^/XML^})
17313 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17314 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17315 Put textual files with detailed metrics into @var{output_dir}
17317 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17318 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17319 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17320 in the name of the output file.
17322 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17323 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17324 Put global metrics into @var{file_name}
17326 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17327 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17328 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17330 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17331 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17332 Use ``short'' source file names in the output. (The @command{gnatmetric}
17333 output includes the name(s) of the Ada source file(s) from which the metrics
17334 are computed. By default each name includes the absolute path. The
17335 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17336 to exclude all directory information from the file names that are output.)
17340 @node Disable Metrics For Local Units
17341 @subsection Disable Metrics For Local Units
17342 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17345 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17347 unit per one source file. It computes line metrics for the whole source
17348 file, and it also computes syntax
17349 and complexity metrics for the file's outermost unit.
17351 By default, @command{gnatmetric} will also compute all metrics for certain
17352 kinds of locally declared program units:
17356 subprogram (and generic subprogram) bodies;
17359 package (and generic package) specs and bodies;
17362 task object and type specifications and bodies;
17365 protected object and type specifications and bodies.
17369 These kinds of entities will be referred to as
17370 @emph{eligible local program units}, or simply @emph{eligible local units},
17371 @cindex Eligible local unit (for @command{gnatmetric})
17372 in the discussion below.
17374 Note that a subprogram declaration, generic instantiation,
17375 or renaming declaration only receives metrics
17376 computation when it appear as the outermost entity
17379 Suppression of metrics computation for eligible local units can be
17380 obtained via the following switch:
17383 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17384 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17385 Do not compute detailed metrics for eligible local program units
17389 @node Specifying a set of metrics to compute
17390 @subsection Specifying a set of metrics to compute
17393 By default all the metrics are computed and reported. The switches
17394 described in this subsection allow you to control, on an individual
17395 basis, whether metrics are computed and
17396 reported. If at least one positive metric
17397 switch is specified (that is, a switch that defines that a given
17398 metric or set of metrics is to be computed), then only
17399 explicitly specified metrics are reported.
17402 * Line Metrics Control::
17403 * Syntax Metrics Control::
17404 * Complexity Metrics Control::
17405 * Object-Oriented Metrics Control::
17408 @node Line Metrics Control
17409 @subsubsection Line Metrics Control
17410 @cindex Line metrics control in @command{gnatmetric}
17413 For any (legal) source file, and for each of its
17414 eligible local program units, @command{gnatmetric} computes the following
17419 the total number of lines;
17422 the total number of code lines (i.e., non-blank lines that are not comments)
17425 the number of comment lines
17428 the number of code lines containing end-of-line comments;
17431 the comment percentage: the ratio between the number of lines that contain
17432 comments and the number of all non-blank lines, expressed as a percentage;
17435 the number of empty lines and lines containing only space characters and/or
17436 format effectors (blank lines)
17439 the average number of code lines in subprogram bodies, task bodies, entry
17440 bodies and statement sequences in package bodies (this metric is only computed
17441 across the whole set of the analyzed units)
17446 @command{gnatmetric} sums the values of the line metrics for all the
17447 files being processed and then generates the cumulative results. The tool
17448 also computes for all the files being processed the average number of code
17451 You can use the following switches to select the specific line metrics
17452 to be computed and reported.
17455 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17458 @cindex @option{--no-lines@var{x}}
17461 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17462 Report all the line metrics
17464 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17465 Do not report any of line metrics
17467 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17468 Report the number of all lines
17470 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17471 Do not report the number of all lines
17473 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17474 Report the number of code lines
17476 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17477 Do not report the number of code lines
17479 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17480 Report the number of comment lines
17482 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17483 Do not report the number of comment lines
17485 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17486 Report the number of code lines containing
17487 end-of-line comments
17489 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17490 Do not report the number of code lines containing
17491 end-of-line comments
17493 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17494 Report the comment percentage in the program text
17496 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17497 Do not report the comment percentage in the program text
17499 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17500 Report the number of blank lines
17502 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17503 Do not report the number of blank lines
17505 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17506 Report the average number of code lines in subprogram bodies, task bodies,
17507 entry bodies and statement sequences in package bodies. The metric is computed
17508 and reported for the whole set of processed Ada sources only.
17510 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17511 Do not report the average number of code lines in subprogram bodies,
17512 task bodies, entry bodies and statement sequences in package bodies.
17516 @node Syntax Metrics Control
17517 @subsubsection Syntax Metrics Control
17518 @cindex Syntax metrics control in @command{gnatmetric}
17521 @command{gnatmetric} computes various syntactic metrics for the
17522 outermost unit and for each eligible local unit:
17525 @item LSLOC (``Logical Source Lines Of Code'')
17526 The total number of declarations and the total number of statements
17528 @item Maximal static nesting level of inner program units
17530 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17531 package, a task unit, a protected unit, a
17532 protected entry, a generic unit, or an explicitly declared subprogram other
17533 than an enumeration literal.''
17535 @item Maximal nesting level of composite syntactic constructs
17536 This corresponds to the notion of the
17537 maximum nesting level in the GNAT built-in style checks
17538 (@pxref{Style Checking})
17542 For the outermost unit in the file, @command{gnatmetric} additionally computes
17543 the following metrics:
17546 @item Public subprograms
17547 This metric is computed for package specs. It is the
17548 number of subprograms and generic subprograms declared in the visible
17549 part (including the visible part of nested packages, protected objects, and
17552 @item All subprograms
17553 This metric is computed for bodies and subunits. The
17554 metric is equal to a total number of subprogram bodies in the compilation
17556 Neither generic instantiations nor renamings-as-a-body nor body stubs
17557 are counted. Any subprogram body is counted, independently of its nesting
17558 level and enclosing constructs. Generic bodies and bodies of protected
17559 subprograms are counted in the same way as ``usual'' subprogram bodies.
17562 This metric is computed for package specs and
17563 generic package declarations. It is the total number of types
17564 that can be referenced from outside this compilation unit, plus the
17565 number of types from all the visible parts of all the visible generic
17566 packages. Generic formal types are not counted. Only types, not subtypes,
17570 Along with the total number of public types, the following
17571 types are counted and reported separately:
17578 Root tagged types (abstract, non-abstract, private, non-private). Type
17579 extensions are @emph{not} counted
17582 Private types (including private extensions)
17593 This metric is computed for any compilation unit. It is equal to the total
17594 number of the declarations of different types given in the compilation unit.
17595 The private and the corresponding full type declaration are counted as one
17596 type declaration. Incomplete type declarations and generic formal types
17598 No distinction is made among different kinds of types (abstract,
17599 private etc.); the total number of types is computed and reported.
17604 By default, all the syntax metrics are computed and reported. You can use the
17605 following switches to select specific syntax metrics.
17609 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17612 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17615 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17616 Report all the syntax metrics
17618 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17619 Do not report any of syntax metrics
17621 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17622 Report the total number of declarations
17624 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17625 Do not report the total number of declarations
17627 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17628 Report the total number of statements
17630 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17631 Do not report the total number of statements
17633 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17634 Report the number of public subprograms in a compilation unit
17636 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17637 Do not report the number of public subprograms in a compilation unit
17639 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17640 Report the number of all the subprograms in a compilation unit
17642 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17643 Do not report the number of all the subprograms in a compilation unit
17645 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17646 Report the number of public types in a compilation unit
17648 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17649 Do not report the number of public types in a compilation unit
17651 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17652 Report the number of all the types in a compilation unit
17654 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17655 Do not report the number of all the types in a compilation unit
17657 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17658 Report the maximal program unit nesting level
17660 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17661 Do not report the maximal program unit nesting level
17663 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17664 Report the maximal construct nesting level
17666 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17667 Do not report the maximal construct nesting level
17671 @node Complexity Metrics Control
17672 @subsubsection Complexity Metrics Control
17673 @cindex Complexity metrics control in @command{gnatmetric}
17676 For a program unit that is an executable body (a subprogram body (including
17677 generic bodies), task body, entry body or a package body containing
17678 its own statement sequence) @command{gnatmetric} computes the following
17679 complexity metrics:
17683 McCabe cyclomatic complexity;
17686 McCabe essential complexity;
17689 maximal loop nesting level
17694 The McCabe complexity metrics are defined
17695 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17697 According to McCabe, both control statements and short-circuit control forms
17698 should be taken into account when computing cyclomatic complexity. For each
17699 body, we compute three metric values:
17703 the complexity introduced by control
17704 statements only, without taking into account short-circuit forms,
17707 the complexity introduced by short-circuit control forms only, and
17711 cyclomatic complexity, which is the sum of these two values.
17715 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17716 the code in the exception handlers and in all the nested program units.
17718 By default, all the complexity metrics are computed and reported.
17719 For more fine-grained control you can use
17720 the following switches:
17723 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17726 @cindex @option{--no-complexity@var{x}}
17729 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17730 Report all the complexity metrics
17732 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17733 Do not report any of complexity metrics
17735 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17736 Report the McCabe Cyclomatic Complexity
17738 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17739 Do not report the McCabe Cyclomatic Complexity
17741 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17742 Report the Essential Complexity
17744 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17745 Do not report the Essential Complexity
17747 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17748 Report maximal loop nesting level
17750 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17751 Do not report maximal loop nesting level
17753 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17754 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17755 task bodies, entry bodies and statement sequences in package bodies.
17756 The metric is computed and reported for whole set of processed Ada sources
17759 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17760 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17761 bodies, task bodies, entry bodies and statement sequences in package bodies
17763 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17764 @item ^-ne^/NO_EXITS_AS_GOTOS^
17765 Do not consider @code{exit} statements as @code{goto}s when
17766 computing Essential Complexity
17768 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17769 Report the extra exit points for subprogram bodies. As an exit point, this
17770 metric counts @code{return} statements and raise statements in case when the
17771 raised exception is not handled in the same body. In case of a function this
17772 metric subtracts 1 from the number of exit points, because a function body
17773 must contain at least one @code{return} statement.
17775 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17776 Do not report the extra exit points for subprogram bodies
17780 @node Object-Oriented Metrics Control
17781 @subsubsection Object-Oriented Metrics Control
17782 @cindex Object-Oriented metrics control in @command{gnatmetric}
17785 @cindex Coupling metrics (in in @command{gnatmetric})
17786 Coupling metrics are object-oriented metrics that measure the
17787 dependencies between a given class (or a group of classes) and the
17788 ``external world'' (that is, the other classes in the program). In this
17789 subsection the term ``class'' is used in its
17790 traditional object-oriented programming sense
17791 (an instantiable module that contains data and/or method members).
17792 A @emph{category} (of classes)
17793 is a group of closely related classes that are reused and/or
17796 A class @code{K}'s @emph{efferent coupling} is the number of classes
17797 that @code{K} depends upon.
17798 A category's efferent coupling is the number of classes outside the
17799 category that the classes inside the category depend upon.
17801 A class @code{K}'s @emph{afferent coupling} is the number of classes
17802 that depend upon @code{K}.
17803 A category's afferent coupling is the number of classes outside the
17804 category that depend on classes belonging to the category.
17806 Ada's implementation of the object-oriented paradigm does not use the
17807 traditional class notion, so the definition of the coupling
17808 metrics for Ada maps the class and class category notions
17809 onto Ada constructs.
17811 For the coupling metrics, several kinds of modules -- a library package,
17812 a library generic package, and a library generic package instantiation --
17813 that define a tagged type or an interface type are
17814 considered to be a class. A category consists of a library package (or
17815 a library generic package) that defines a tagged or an interface type,
17816 together with all its descendant (generic) packages that define tagged
17817 or interface types. For any package counted as a class,
17818 its body and subunits (if any) are considered
17819 together with its spec when counting the dependencies, and coupling
17820 metrics are reported for spec units only. For dependencies
17821 between classes, the Ada semantic dependencies are considered.
17822 For coupling metrics, only dependencies on units that are considered as
17823 classes, are considered.
17825 When computing coupling metrics, @command{gnatmetric} counts only
17826 dependencies between units that are arguments of the gnatmetric call.
17827 Coupling metrics are program-wide (or project-wide) metrics, so to
17828 get a valid result, you should call @command{gnatmetric} for
17829 the whole set of sources that make up your program. It can be done
17830 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17831 option (see See @ref{The GNAT Driver and Project Files} for details.
17833 By default, all the coupling metrics are disabled. You can use the following
17834 switches to specify the coupling metrics to be computed and reported:
17839 @cindex @option{--package@var{x}} (@command{gnatmetric})
17840 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17841 @cindex @option{--category@var{x}} (@command{gnatmetric})
17842 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17846 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17849 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17850 Report all the coupling metrics
17852 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17853 Do not report any of metrics
17855 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17856 Report package efferent coupling
17858 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17859 Do not report package efferent coupling
17861 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17862 Report package afferent coupling
17864 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17865 Do not report package afferent coupling
17867 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17868 Report category efferent coupling
17870 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17871 Do not report category efferent coupling
17873 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17874 Report category afferent coupling
17876 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17877 Do not report category afferent coupling
17881 @node Other gnatmetric Switches
17882 @subsection Other @code{gnatmetric} Switches
17885 Additional @command{gnatmetric} switches are as follows:
17888 @item ^-files @var{filename}^/FILES=@var{filename}^
17889 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17890 Take the argument source files from the specified file. This file should be an
17891 ordinary text file containing file names separated by spaces or
17892 line breaks. You can use this switch more then once in the same call to
17893 @command{gnatmetric}. You also can combine this switch with
17894 an explicit list of files.
17896 @item ^-v^/VERBOSE^
17897 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17899 @command{gnatmetric} generates version information and then
17900 a trace of sources being processed.
17902 @item ^-dv^/DEBUG_OUTPUT^
17903 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17905 @command{gnatmetric} generates various messages useful to understand what
17906 happens during the metrics computation
17909 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17913 @node Generate project-wide metrics
17914 @subsection Generate project-wide metrics
17916 In order to compute metrics on all units of a given project, you can use
17917 the @command{gnat} driver along with the @option{-P} option:
17923 If the project @code{proj} depends upon other projects, you can compute
17924 the metrics on the project closure using the @option{-U} option:
17926 gnat metric -Pproj -U
17930 Finally, if not all the units are relevant to a particular main
17931 program in the project closure, you can generate metrics for the set
17932 of units needed to create a given main program (unit closure) using
17933 the @option{-U} option followed by the name of the main unit:
17935 gnat metric -Pproj -U main
17939 @c ***********************************
17940 @node File Name Krunching Using gnatkr
17941 @chapter File Name Krunching Using @code{gnatkr}
17945 This chapter discusses the method used by the compiler to shorten
17946 the default file names chosen for Ada units so that they do not
17947 exceed the maximum length permitted. It also describes the
17948 @code{gnatkr} utility that can be used to determine the result of
17949 applying this shortening.
17953 * Krunching Method::
17954 * Examples of gnatkr Usage::
17958 @section About @code{gnatkr}
17961 The default file naming rule in GNAT
17962 is that the file name must be derived from
17963 the unit name. The exact default rule is as follows:
17966 Take the unit name and replace all dots by hyphens.
17968 If such a replacement occurs in the
17969 second character position of a name, and the first character is
17970 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17971 then replace the dot by the character
17972 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17973 instead of a minus.
17975 The reason for this exception is to avoid clashes
17976 with the standard names for children of System, Ada, Interfaces,
17977 and GNAT, which use the prefixes
17978 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17981 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17982 switch of the compiler activates a ``krunching''
17983 circuit that limits file names to nn characters (where nn is a decimal
17984 integer). For example, using OpenVMS,
17985 where the maximum file name length is
17986 39, the value of nn is usually set to 39, but if you want to generate
17987 a set of files that would be usable if ported to a system with some
17988 different maximum file length, then a different value can be specified.
17989 The default value of 39 for OpenVMS need not be specified.
17991 The @code{gnatkr} utility can be used to determine the krunched name for
17992 a given file, when krunched to a specified maximum length.
17995 @section Using @code{gnatkr}
17998 The @code{gnatkr} command has the form
18002 $ gnatkr @var{name} @ovar{length}
18008 $ gnatkr @var{name} /COUNT=nn
18013 @var{name} is the uncrunched file name, derived from the name of the unit
18014 in the standard manner described in the previous section (i.e., in particular
18015 all dots are replaced by hyphens). The file name may or may not have an
18016 extension (defined as a suffix of the form period followed by arbitrary
18017 characters other than period). If an extension is present then it will
18018 be preserved in the output. For example, when krunching @file{hellofile.ads}
18019 to eight characters, the result will be hellofil.ads.
18021 Note: for compatibility with previous versions of @code{gnatkr} dots may
18022 appear in the name instead of hyphens, but the last dot will always be
18023 taken as the start of an extension. So if @code{gnatkr} is given an argument
18024 such as @file{Hello.World.adb} it will be treated exactly as if the first
18025 period had been a hyphen, and for example krunching to eight characters
18026 gives the result @file{hellworl.adb}.
18028 Note that the result is always all lower case (except on OpenVMS where it is
18029 all upper case). Characters of the other case are folded as required.
18031 @var{length} represents the length of the krunched name. The default
18032 when no argument is given is ^8^39^ characters. A length of zero stands for
18033 unlimited, in other words do not chop except for system files where the
18034 implied crunching length is always eight characters.
18037 The output is the krunched name. The output has an extension only if the
18038 original argument was a file name with an extension.
18040 @node Krunching Method
18041 @section Krunching Method
18044 The initial file name is determined by the name of the unit that the file
18045 contains. The name is formed by taking the full expanded name of the
18046 unit and replacing the separating dots with hyphens and
18047 using ^lowercase^uppercase^
18048 for all letters, except that a hyphen in the second character position is
18049 replaced by a ^tilde^dollar sign^ if the first character is
18050 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
18051 The extension is @code{.ads} for a
18052 spec and @code{.adb} for a body.
18053 Krunching does not affect the extension, but the file name is shortened to
18054 the specified length by following these rules:
18058 The name is divided into segments separated by hyphens, tildes or
18059 underscores and all hyphens, tildes, and underscores are
18060 eliminated. If this leaves the name short enough, we are done.
18063 If the name is too long, the longest segment is located (left-most
18064 if there are two of equal length), and shortened by dropping
18065 its last character. This is repeated until the name is short enough.
18067 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
18068 to fit the name into 8 characters as required by some operating systems.
18071 our-strings-wide_fixed 22
18072 our strings wide fixed 19
18073 our string wide fixed 18
18074 our strin wide fixed 17
18075 our stri wide fixed 16
18076 our stri wide fixe 15
18077 our str wide fixe 14
18078 our str wid fixe 13
18084 Final file name: oustwifi.adb
18088 The file names for all predefined units are always krunched to eight
18089 characters. The krunching of these predefined units uses the following
18090 special prefix replacements:
18094 replaced by @file{^a^A^-}
18097 replaced by @file{^g^G^-}
18100 replaced by @file{^i^I^-}
18103 replaced by @file{^s^S^-}
18106 These system files have a hyphen in the second character position. That
18107 is why normal user files replace such a character with a
18108 ^tilde^dollar sign^, to
18109 avoid confusion with system file names.
18111 As an example of this special rule, consider
18112 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18115 ada-strings-wide_fixed 22
18116 a- strings wide fixed 18
18117 a- string wide fixed 17
18118 a- strin wide fixed 16
18119 a- stri wide fixed 15
18120 a- stri wide fixe 14
18121 a- str wide fixe 13
18127 Final file name: a-stwifi.adb
18131 Of course no file shortening algorithm can guarantee uniqueness over all
18132 possible unit names, and if file name krunching is used then it is your
18133 responsibility to ensure that no name clashes occur. The utility
18134 program @code{gnatkr} is supplied for conveniently determining the
18135 krunched name of a file.
18137 @node Examples of gnatkr Usage
18138 @section Examples of @code{gnatkr} Usage
18145 $ gnatkr very_long_unit_name.ads --> velounna.ads
18146 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18147 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18148 $ gnatkr grandparent-parent-child --> grparchi
18150 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18151 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18154 @node Preprocessing Using gnatprep
18155 @chapter Preprocessing Using @code{gnatprep}
18159 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18161 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18162 special GNAT features.
18163 For further discussion of conditional compilation in general, see
18164 @ref{Conditional Compilation}.
18167 * Preprocessing Symbols::
18169 * Switches for gnatprep::
18170 * Form of Definitions File::
18171 * Form of Input Text for gnatprep::
18174 @node Preprocessing Symbols
18175 @section Preprocessing Symbols
18178 Preprocessing symbols are defined in definition files and referred to in
18179 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18180 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18181 all characters need to be in the ASCII set (no accented letters).
18183 @node Using gnatprep
18184 @section Using @code{gnatprep}
18187 To call @code{gnatprep} use
18190 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18197 is an optional sequence of switches as described in the next section.
18200 is the full name of the input file, which is an Ada source
18201 file containing preprocessor directives.
18204 is the full name of the output file, which is an Ada source
18205 in standard Ada form. When used with GNAT, this file name will
18206 normally have an ads or adb suffix.
18209 is the full name of a text file containing definitions of
18210 preprocessing symbols to be referenced by the preprocessor. This argument is
18211 optional, and can be replaced by the use of the @option{-D} switch.
18215 @node Switches for gnatprep
18216 @section Switches for @code{gnatprep}
18221 @item ^-b^/BLANK_LINES^
18222 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18223 Causes both preprocessor lines and the lines deleted by
18224 preprocessing to be replaced by blank lines in the output source file,
18225 preserving line numbers in the output file.
18227 @item ^-c^/COMMENTS^
18228 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18229 Causes both preprocessor lines and the lines deleted
18230 by preprocessing to be retained in the output source as comments marked
18231 with the special string @code{"--! "}. This option will result in line numbers
18232 being preserved in the output file.
18234 @item ^-C^/REPLACE_IN_COMMENTS^
18235 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18236 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18237 If this option is specified, then comments are scanned and any $symbol
18238 substitutions performed as in program text. This is particularly useful
18239 when structured comments are used (e.g., when writing programs in the
18240 SPARK dialect of Ada). Note that this switch is not available when
18241 doing integrated preprocessing (it would be useless in this context
18242 since comments are ignored by the compiler in any case).
18244 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18245 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18246 Defines a new preprocessing symbol, associated with value. If no value is given
18247 on the command line, then symbol is considered to be @code{True}. This switch
18248 can be used in place of a definition file.
18252 @cindex @option{/REMOVE} (@command{gnatprep})
18253 This is the default setting which causes lines deleted by preprocessing
18254 to be entirely removed from the output file.
18257 @item ^-r^/REFERENCE^
18258 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18259 Causes a @code{Source_Reference} pragma to be generated that
18260 references the original input file, so that error messages will use
18261 the file name of this original file. The use of this switch implies
18262 that preprocessor lines are not to be removed from the file, so its
18263 use will force @option{^-b^/BLANK_LINES^} mode if
18264 @option{^-c^/COMMENTS^}
18265 has not been specified explicitly.
18267 Note that if the file to be preprocessed contains multiple units, then
18268 it will be necessary to @code{gnatchop} the output file from
18269 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18270 in the preprocessed file, it will be respected by
18271 @code{gnatchop ^-r^/REFERENCE^}
18272 so that the final chopped files will correctly refer to the original
18273 input source file for @code{gnatprep}.
18275 @item ^-s^/SYMBOLS^
18276 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18277 Causes a sorted list of symbol names and values to be
18278 listed on the standard output file.
18280 @item ^-u^/UNDEFINED^
18281 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18282 Causes undefined symbols to be treated as having the value FALSE in the context
18283 of a preprocessor test. In the absence of this option, an undefined symbol in
18284 a @code{#if} or @code{#elsif} test will be treated as an error.
18290 Note: if neither @option{-b} nor @option{-c} is present,
18291 then preprocessor lines and
18292 deleted lines are completely removed from the output, unless -r is
18293 specified, in which case -b is assumed.
18296 @node Form of Definitions File
18297 @section Form of Definitions File
18300 The definitions file contains lines of the form
18307 where symbol is a preprocessing symbol, and value is one of the following:
18311 Empty, corresponding to a null substitution
18313 A string literal using normal Ada syntax
18315 Any sequence of characters from the set
18316 (letters, digits, period, underline).
18320 Comment lines may also appear in the definitions file, starting with
18321 the usual @code{--},
18322 and comments may be added to the definitions lines.
18324 @node Form of Input Text for gnatprep
18325 @section Form of Input Text for @code{gnatprep}
18328 The input text may contain preprocessor conditional inclusion lines,
18329 as well as general symbol substitution sequences.
18331 The preprocessor conditional inclusion commands have the form
18336 #if @i{expression} @r{[}then@r{]}
18338 #elsif @i{expression} @r{[}then@r{]}
18340 #elsif @i{expression} @r{[}then@r{]}
18351 In this example, @i{expression} is defined by the following grammar:
18353 @i{expression} ::= <symbol>
18354 @i{expression} ::= <symbol> = "<value>"
18355 @i{expression} ::= <symbol> = <symbol>
18356 @i{expression} ::= <symbol> 'Defined
18357 @i{expression} ::= not @i{expression}
18358 @i{expression} ::= @i{expression} and @i{expression}
18359 @i{expression} ::= @i{expression} or @i{expression}
18360 @i{expression} ::= @i{expression} and then @i{expression}
18361 @i{expression} ::= @i{expression} or else @i{expression}
18362 @i{expression} ::= ( @i{expression} )
18365 The following restriction exists: it is not allowed to have "and" or "or"
18366 following "not" in the same expression without parentheses. For example, this
18373 This should be one of the following:
18381 For the first test (@i{expression} ::= <symbol>) the symbol must have
18382 either the value true or false, that is to say the right-hand of the
18383 symbol definition must be one of the (case-insensitive) literals
18384 @code{True} or @code{False}. If the value is true, then the
18385 corresponding lines are included, and if the value is false, they are
18388 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18389 the symbol has been defined in the definition file or by a @option{-D}
18390 switch on the command line. Otherwise, the test is false.
18392 The equality tests are case insensitive, as are all the preprocessor lines.
18394 If the symbol referenced is not defined in the symbol definitions file,
18395 then the effect depends on whether or not switch @option{-u}
18396 is specified. If so, then the symbol is treated as if it had the value
18397 false and the test fails. If this switch is not specified, then
18398 it is an error to reference an undefined symbol. It is also an error to
18399 reference a symbol that is defined with a value other than @code{True}
18402 The use of the @code{not} operator inverts the sense of this logical test.
18403 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18404 operators, without parentheses. For example, "if not X or Y then" is not
18405 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18407 The @code{then} keyword is optional as shown
18409 The @code{#} must be the first non-blank character on a line, but
18410 otherwise the format is free form. Spaces or tabs may appear between
18411 the @code{#} and the keyword. The keywords and the symbols are case
18412 insensitive as in normal Ada code. Comments may be used on a
18413 preprocessor line, but other than that, no other tokens may appear on a
18414 preprocessor line. Any number of @code{elsif} clauses can be present,
18415 including none at all. The @code{else} is optional, as in Ada.
18417 The @code{#} marking the start of a preprocessor line must be the first
18418 non-blank character on the line, i.e., it must be preceded only by
18419 spaces or horizontal tabs.
18421 Symbol substitution outside of preprocessor lines is obtained by using
18429 anywhere within a source line, except in a comment or within a
18430 string literal. The identifier
18431 following the @code{$} must match one of the symbols defined in the symbol
18432 definition file, and the result is to substitute the value of the
18433 symbol in place of @code{$symbol} in the output file.
18435 Note that although the substitution of strings within a string literal
18436 is not possible, it is possible to have a symbol whose defined value is
18437 a string literal. So instead of setting XYZ to @code{hello} and writing:
18440 Header : String := "$XYZ";
18444 you should set XYZ to @code{"hello"} and write:
18447 Header : String := $XYZ;
18451 and then the substitution will occur as desired.
18454 @node The GNAT Run-Time Library Builder gnatlbr
18455 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18457 @cindex Library builder
18460 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18461 supplied configuration pragmas.
18464 * Running gnatlbr::
18465 * Switches for gnatlbr::
18466 * Examples of gnatlbr Usage::
18469 @node Running gnatlbr
18470 @section Running @code{gnatlbr}
18473 The @code{gnatlbr} command has the form
18476 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18479 @node Switches for gnatlbr
18480 @section Switches for @code{gnatlbr}
18483 @code{gnatlbr} recognizes the following switches:
18487 @item /CREATE=directory
18488 @cindex @code{/CREATE} (@code{gnatlbr})
18489 Create the new run-time library in the specified directory.
18491 @item /SET=directory
18492 @cindex @code{/SET} (@code{gnatlbr})
18493 Make the library in the specified directory the current run-time library.
18495 @item /DELETE=directory
18496 @cindex @code{/DELETE} (@code{gnatlbr})
18497 Delete the run-time library in the specified directory.
18500 @cindex @code{/CONFIG} (@code{gnatlbr})
18501 With /CREATE: Use the configuration pragmas in the specified file when
18502 building the library.
18504 With /SET: Use the configuration pragmas in the specified file when
18509 @node Examples of gnatlbr Usage
18510 @section Example of @code{gnatlbr} Usage
18513 Contents of VAXFLOAT.ADC:
18514 pragma Float_Representation (VAX_Float);
18516 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18518 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18523 @node The GNAT Library Browser gnatls
18524 @chapter The GNAT Library Browser @code{gnatls}
18526 @cindex Library browser
18529 @code{gnatls} is a tool that outputs information about compiled
18530 units. It gives the relationship between objects, unit names and source
18531 files. It can also be used to check the source dependencies of a unit
18532 as well as various characteristics.
18534 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18535 driver (see @ref{The GNAT Driver and Project Files}).
18539 * Switches for gnatls::
18540 * Examples of gnatls Usage::
18543 @node Running gnatls
18544 @section Running @code{gnatls}
18547 The @code{gnatls} command has the form
18550 $ gnatls switches @var{object_or_ali_file}
18554 The main argument is the list of object or @file{ali} files
18555 (@pxref{The Ada Library Information Files})
18556 for which information is requested.
18558 In normal mode, without additional option, @code{gnatls} produces a
18559 four-column listing. Each line represents information for a specific
18560 object. The first column gives the full path of the object, the second
18561 column gives the name of the principal unit in this object, the third
18562 column gives the status of the source and the fourth column gives the
18563 full path of the source representing this unit.
18564 Here is a simple example of use:
18568 ^./^[]^demo1.o demo1 DIF demo1.adb
18569 ^./^[]^demo2.o demo2 OK demo2.adb
18570 ^./^[]^hello.o h1 OK hello.adb
18571 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18572 ^./^[]^instr.o instr OK instr.adb
18573 ^./^[]^tef.o tef DIF tef.adb
18574 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18575 ^./^[]^tgef.o tgef DIF tgef.adb
18579 The first line can be interpreted as follows: the main unit which is
18581 object file @file{demo1.o} is demo1, whose main source is in
18582 @file{demo1.adb}. Furthermore, the version of the source used for the
18583 compilation of demo1 has been modified (DIF). Each source file has a status
18584 qualifier which can be:
18587 @item OK (unchanged)
18588 The version of the source file used for the compilation of the
18589 specified unit corresponds exactly to the actual source file.
18591 @item MOK (slightly modified)
18592 The version of the source file used for the compilation of the
18593 specified unit differs from the actual source file but not enough to
18594 require recompilation. If you use gnatmake with the qualifier
18595 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18596 MOK will not be recompiled.
18598 @item DIF (modified)
18599 No version of the source found on the path corresponds to the source
18600 used to build this object.
18602 @item ??? (file not found)
18603 No source file was found for this unit.
18605 @item HID (hidden, unchanged version not first on PATH)
18606 The version of the source that corresponds exactly to the source used
18607 for compilation has been found on the path but it is hidden by another
18608 version of the same source that has been modified.
18612 @node Switches for gnatls
18613 @section Switches for @code{gnatls}
18616 @code{gnatls} recognizes the following switches:
18620 @cindex @option{--version} @command{gnatls}
18621 Display Copyright and version, then exit disregarding all other options.
18624 @cindex @option{--help} @command{gnatls}
18625 If @option{--version} was not used, display usage, then exit disregarding
18628 @item ^-a^/ALL_UNITS^
18629 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18630 Consider all units, including those of the predefined Ada library.
18631 Especially useful with @option{^-d^/DEPENDENCIES^}.
18633 @item ^-d^/DEPENDENCIES^
18634 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18635 List sources from which specified units depend on.
18637 @item ^-h^/OUTPUT=OPTIONS^
18638 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18639 Output the list of options.
18641 @item ^-o^/OUTPUT=OBJECTS^
18642 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18643 Only output information about object files.
18645 @item ^-s^/OUTPUT=SOURCES^
18646 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18647 Only output information about source files.
18649 @item ^-u^/OUTPUT=UNITS^
18650 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18651 Only output information about compilation units.
18653 @item ^-files^/FILES^=@var{file}
18654 @cindex @option{^-files^/FILES^} (@code{gnatls})
18655 Take as arguments the files listed in text file @var{file}.
18656 Text file @var{file} may contain empty lines that are ignored.
18657 Each nonempty line should contain the name of an existing file.
18658 Several such switches may be specified simultaneously.
18660 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18661 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18662 @itemx ^-I^/SEARCH=^@var{dir}
18663 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18665 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18666 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18667 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18668 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18669 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18670 flags (@pxref{Switches for gnatmake}).
18672 @item --RTS=@var{rts-path}
18673 @cindex @option{--RTS} (@code{gnatls})
18674 Specifies the default location of the runtime library. Same meaning as the
18675 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18677 @item ^-v^/OUTPUT=VERBOSE^
18678 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18679 Verbose mode. Output the complete source, object and project paths. Do not use
18680 the default column layout but instead use long format giving as much as
18681 information possible on each requested units, including special
18682 characteristics such as:
18685 @item Preelaborable
18686 The unit is preelaborable in the Ada sense.
18689 No elaboration code has been produced by the compiler for this unit.
18692 The unit is pure in the Ada sense.
18694 @item Elaborate_Body
18695 The unit contains a pragma Elaborate_Body.
18698 The unit contains a pragma Remote_Types.
18700 @item Shared_Passive
18701 The unit contains a pragma Shared_Passive.
18704 This unit is part of the predefined environment and cannot be modified
18707 @item Remote_Call_Interface
18708 The unit contains a pragma Remote_Call_Interface.
18714 @node Examples of gnatls Usage
18715 @section Example of @code{gnatls} Usage
18719 Example of using the verbose switch. Note how the source and
18720 object paths are affected by the -I switch.
18723 $ gnatls -v -I.. demo1.o
18725 GNATLS 5.03w (20041123-34)
18726 Copyright 1997-2004 Free Software Foundation, Inc.
18728 Source Search Path:
18729 <Current_Directory>
18731 /home/comar/local/adainclude/
18733 Object Search Path:
18734 <Current_Directory>
18736 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18738 Project Search Path:
18739 <Current_Directory>
18740 /home/comar/local/lib/gnat/
18745 Kind => subprogram body
18746 Flags => No_Elab_Code
18747 Source => demo1.adb modified
18751 The following is an example of use of the dependency list.
18752 Note the use of the -s switch
18753 which gives a straight list of source files. This can be useful for
18754 building specialized scripts.
18757 $ gnatls -d demo2.o
18758 ./demo2.o demo2 OK demo2.adb
18764 $ gnatls -d -s -a demo1.o
18766 /home/comar/local/adainclude/ada.ads
18767 /home/comar/local/adainclude/a-finali.ads
18768 /home/comar/local/adainclude/a-filico.ads
18769 /home/comar/local/adainclude/a-stream.ads
18770 /home/comar/local/adainclude/a-tags.ads
18773 /home/comar/local/adainclude/gnat.ads
18774 /home/comar/local/adainclude/g-io.ads
18776 /home/comar/local/adainclude/system.ads
18777 /home/comar/local/adainclude/s-exctab.ads
18778 /home/comar/local/adainclude/s-finimp.ads
18779 /home/comar/local/adainclude/s-finroo.ads
18780 /home/comar/local/adainclude/s-secsta.ads
18781 /home/comar/local/adainclude/s-stalib.ads
18782 /home/comar/local/adainclude/s-stoele.ads
18783 /home/comar/local/adainclude/s-stratt.ads
18784 /home/comar/local/adainclude/s-tasoli.ads
18785 /home/comar/local/adainclude/s-unstyp.ads
18786 /home/comar/local/adainclude/unchconv.ads
18792 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18794 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18795 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18796 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18797 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18798 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18802 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18803 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18805 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18806 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18807 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18808 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18809 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18810 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18811 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18812 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18813 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18814 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18815 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18819 @node Cleaning Up Using gnatclean
18820 @chapter Cleaning Up Using @code{gnatclean}
18822 @cindex Cleaning tool
18825 @code{gnatclean} is a tool that allows the deletion of files produced by the
18826 compiler, binder and linker, including ALI files, object files, tree files,
18827 expanded source files, library files, interface copy source files, binder
18828 generated files and executable files.
18831 * Running gnatclean::
18832 * Switches for gnatclean::
18833 @c * Examples of gnatclean Usage::
18836 @node Running gnatclean
18837 @section Running @code{gnatclean}
18840 The @code{gnatclean} command has the form:
18843 $ gnatclean switches @var{names}
18847 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18848 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18849 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18852 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18853 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18854 the linker. In informative-only mode, specified by switch
18855 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18856 normal mode is listed, but no file is actually deleted.
18858 @node Switches for gnatclean
18859 @section Switches for @code{gnatclean}
18862 @code{gnatclean} recognizes the following switches:
18866 @cindex @option{--version} @command{gnatclean}
18867 Display Copyright and version, then exit disregarding all other options.
18870 @cindex @option{--help} @command{gnatclean}
18871 If @option{--version} was not used, display usage, then exit disregarding
18874 @item ^-c^/COMPILER_FILES_ONLY^
18875 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18876 Only attempt to delete the files produced by the compiler, not those produced
18877 by the binder or the linker. The files that are not to be deleted are library
18878 files, interface copy files, binder generated files and executable files.
18880 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18881 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18882 Indicate that ALI and object files should normally be found in directory
18885 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18886 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18887 When using project files, if some errors or warnings are detected during
18888 parsing and verbose mode is not in effect (no use of switch
18889 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18890 file, rather than its simple file name.
18893 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18894 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18896 @item ^-n^/NODELETE^
18897 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18898 Informative-only mode. Do not delete any files. Output the list of the files
18899 that would have been deleted if this switch was not specified.
18901 @item ^-P^/PROJECT_FILE=^@var{project}
18902 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18903 Use project file @var{project}. Only one such switch can be used.
18904 When cleaning a project file, the files produced by the compilation of the
18905 immediate sources or inherited sources of the project files are to be
18906 deleted. This is not depending on the presence or not of executable names
18907 on the command line.
18910 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18911 Quiet output. If there are no errors, do not output anything, except in
18912 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18913 (switch ^-n^/NODELETE^).
18915 @item ^-r^/RECURSIVE^
18916 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18917 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18918 clean all imported and extended project files, recursively. If this switch
18919 is not specified, only the files related to the main project file are to be
18920 deleted. This switch has no effect if no project file is specified.
18922 @item ^-v^/VERBOSE^
18923 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18926 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18927 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18928 Indicates the verbosity of the parsing of GNAT project files.
18929 @xref{Switches Related to Project Files}.
18931 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18932 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18933 Indicates that external variable @var{name} has the value @var{value}.
18934 The Project Manager will use this value for occurrences of
18935 @code{external(name)} when parsing the project file.
18936 @xref{Switches Related to Project Files}.
18938 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18939 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18940 When searching for ALI and object files, look in directory
18943 @item ^-I^/SEARCH=^@var{dir}
18944 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18945 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18947 @item ^-I-^/NOCURRENT_DIRECTORY^
18948 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18949 @cindex Source files, suppressing search
18950 Do not look for ALI or object files in the directory
18951 where @code{gnatclean} was invoked.
18955 @c @node Examples of gnatclean Usage
18956 @c @section Examples of @code{gnatclean} Usage
18959 @node GNAT and Libraries
18960 @chapter GNAT and Libraries
18961 @cindex Library, building, installing, using
18964 This chapter describes how to build and use libraries with GNAT, and also shows
18965 how to recompile the GNAT run-time library. You should be familiar with the
18966 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18970 * Introduction to Libraries in GNAT::
18971 * General Ada Libraries::
18972 * Stand-alone Ada Libraries::
18973 * Rebuilding the GNAT Run-Time Library::
18976 @node Introduction to Libraries in GNAT
18977 @section Introduction to Libraries in GNAT
18980 A library is, conceptually, a collection of objects which does not have its
18981 own main thread of execution, but rather provides certain services to the
18982 applications that use it. A library can be either statically linked with the
18983 application, in which case its code is directly included in the application,
18984 or, on platforms that support it, be dynamically linked, in which case
18985 its code is shared by all applications making use of this library.
18987 GNAT supports both types of libraries.
18988 In the static case, the compiled code can be provided in different ways. The
18989 simplest approach is to provide directly the set of objects resulting from
18990 compilation of the library source files. Alternatively, you can group the
18991 objects into an archive using whatever commands are provided by the operating
18992 system. For the latter case, the objects are grouped into a shared library.
18994 In the GNAT environment, a library has three types of components:
19000 @xref{The Ada Library Information Files}.
19002 Object files, an archive or a shared library.
19006 A GNAT library may expose all its source files, which is useful for
19007 documentation purposes. Alternatively, it may expose only the units needed by
19008 an external user to make use of the library. That is to say, the specs
19009 reflecting the library services along with all the units needed to compile
19010 those specs, which can include generic bodies or any body implementing an
19011 inlined routine. In the case of @emph{stand-alone libraries} those exposed
19012 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
19014 All compilation units comprising an application, including those in a library,
19015 need to be elaborated in an order partially defined by Ada's semantics. GNAT
19016 computes the elaboration order from the @file{ALI} files and this is why they
19017 constitute a mandatory part of GNAT libraries.
19018 @emph{Stand-alone libraries} are the exception to this rule because a specific
19019 library elaboration routine is produced independently of the application(s)
19022 @node General Ada Libraries
19023 @section General Ada Libraries
19026 * Building a library::
19027 * Installing a library::
19028 * Using a library::
19031 @node Building a library
19032 @subsection Building a library
19035 The easiest way to build a library is to use the Project Manager,
19036 which supports a special type of project called a @emph{Library Project}
19037 (@pxref{Library Projects}).
19039 A project is considered a library project, when two project-level attributes
19040 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
19041 control different aspects of library configuration, additional optional
19042 project-level attributes can be specified:
19045 This attribute controls whether the library is to be static or dynamic
19047 @item Library_Version
19048 This attribute specifies the library version; this value is used
19049 during dynamic linking of shared libraries to determine if the currently
19050 installed versions of the binaries are compatible.
19052 @item Library_Options
19054 These attributes specify additional low-level options to be used during
19055 library generation, and redefine the actual application used to generate
19060 The GNAT Project Manager takes full care of the library maintenance task,
19061 including recompilation of the source files for which objects do not exist
19062 or are not up to date, assembly of the library archive, and installation of
19063 the library (i.e., copying associated source, object and @file{ALI} files
19064 to the specified location).
19066 Here is a simple library project file:
19067 @smallexample @c ada
19069 for Source_Dirs use ("src1", "src2");
19070 for Object_Dir use "obj";
19071 for Library_Name use "mylib";
19072 for Library_Dir use "lib";
19073 for Library_Kind use "dynamic";
19078 and the compilation command to build and install the library:
19080 @smallexample @c ada
19081 $ gnatmake -Pmy_lib
19085 It is not entirely trivial to perform manually all the steps required to
19086 produce a library. We recommend that you use the GNAT Project Manager
19087 for this task. In special cases where this is not desired, the necessary
19088 steps are discussed below.
19090 There are various possibilities for compiling the units that make up the
19091 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
19092 with a conventional script. For simple libraries, it is also possible to create
19093 a dummy main program which depends upon all the packages that comprise the
19094 interface of the library. This dummy main program can then be given to
19095 @command{gnatmake}, which will ensure that all necessary objects are built.
19097 After this task is accomplished, you should follow the standard procedure
19098 of the underlying operating system to produce the static or shared library.
19100 Here is an example of such a dummy program:
19101 @smallexample @c ada
19103 with My_Lib.Service1;
19104 with My_Lib.Service2;
19105 with My_Lib.Service3;
19106 procedure My_Lib_Dummy is
19114 Here are the generic commands that will build an archive or a shared library.
19117 # compiling the library
19118 $ gnatmake -c my_lib_dummy.adb
19120 # we don't need the dummy object itself
19121 $ rm my_lib_dummy.o my_lib_dummy.ali
19123 # create an archive with the remaining objects
19124 $ ar rc libmy_lib.a *.o
19125 # some systems may require "ranlib" to be run as well
19127 # or create a shared library
19128 $ gcc -shared -o libmy_lib.so *.o
19129 # some systems may require the code to have been compiled with -fPIC
19131 # remove the object files that are now in the library
19134 # Make the ALI files read-only so that gnatmake will not try to
19135 # regenerate the objects that are in the library
19140 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19141 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19142 be accessed by the directive @option{-l@var{xxx}} at link time.
19144 @node Installing a library
19145 @subsection Installing a library
19146 @cindex @code{ADA_PROJECT_PATH}
19147 @cindex @code{GPR_PROJECT_PATH}
19150 If you use project files, library installation is part of the library build
19151 process. Thus no further action is needed in order to make use of the
19152 libraries that are built as part of the general application build. A usable
19153 version of the library is installed in the directory specified by the
19154 @code{Library_Dir} attribute of the library project file.
19156 You may want to install a library in a context different from where the library
19157 is built. This situation arises with third party suppliers, who may want
19158 to distribute a library in binary form where the user is not expected to be
19159 able to recompile the library. The simplest option in this case is to provide
19160 a project file slightly different from the one used to build the library, by
19161 using the @code{externally_built} attribute. For instance, the project
19162 file used to build the library in the previous section can be changed into the
19163 following one when the library is installed:
19165 @smallexample @c projectfile
19167 for Source_Dirs use ("src1", "src2");
19168 for Library_Name use "mylib";
19169 for Library_Dir use "lib";
19170 for Library_Kind use "dynamic";
19171 for Externally_Built use "true";
19176 This project file assumes that the directories @file{src1},
19177 @file{src2}, and @file{lib} exist in
19178 the directory containing the project file. The @code{externally_built}
19179 attribute makes it clear to the GNAT builder that it should not attempt to
19180 recompile any of the units from this library. It allows the library provider to
19181 restrict the source set to the minimum necessary for clients to make use of the
19182 library as described in the first section of this chapter. It is the
19183 responsibility of the library provider to install the necessary sources, ALI
19184 files and libraries in the directories mentioned in the project file. For
19185 convenience, the user's library project file should be installed in a location
19186 that will be searched automatically by the GNAT
19187 builder. These are the directories referenced in the @env{GPR_PROJECT_PATH}
19188 environment variable (@pxref{Importing Projects}), and also the default GNAT
19189 library location that can be queried with @command{gnatls -v} and is usually of
19190 the form $gnat_install_root/lib/gnat.
19192 When project files are not an option, it is also possible, but not recommended,
19193 to install the library so that the sources needed to use the library are on the
19194 Ada source path and the ALI files & libraries be on the Ada Object path (see
19195 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19196 administrator can place general-purpose libraries in the default compiler
19197 paths, by specifying the libraries' location in the configuration files
19198 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19199 must be located in the GNAT installation tree at the same place as the gcc spec
19200 file. The location of the gcc spec file can be determined as follows:
19206 The configuration files mentioned above have a simple format: each line
19207 must contain one unique directory name.
19208 Those names are added to the corresponding path
19209 in their order of appearance in the file. The names can be either absolute
19210 or relative; in the latter case, they are relative to where theses files
19213 The files @file{ada_source_path} and @file{ada_object_path} might not be
19215 GNAT installation, in which case, GNAT will look for its run-time library in
19216 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19217 objects and @file{ALI} files). When the files exist, the compiler does not
19218 look in @file{adainclude} and @file{adalib}, and thus the
19219 @file{ada_source_path} file
19220 must contain the location for the GNAT run-time sources (which can simply
19221 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19222 contain the location for the GNAT run-time objects (which can simply
19225 You can also specify a new default path to the run-time library at compilation
19226 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19227 the run-time library you want your program to be compiled with. This switch is
19228 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19229 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19231 It is possible to install a library before or after the standard GNAT
19232 library, by reordering the lines in the configuration files. In general, a
19233 library must be installed before the GNAT library if it redefines
19236 @node Using a library
19237 @subsection Using a library
19239 @noindent Once again, the project facility greatly simplifies the use of
19240 libraries. In this context, using a library is just a matter of adding a
19241 @code{with} clause in the user project. For instance, to make use of the
19242 library @code{My_Lib} shown in examples in earlier sections, you can
19245 @smallexample @c projectfile
19252 Even if you have a third-party, non-Ada library, you can still use GNAT's
19253 Project Manager facility to provide a wrapper for it. For example, the
19254 following project, when @code{with}ed by your main project, will link with the
19255 third-party library @file{liba.a}:
19257 @smallexample @c projectfile
19260 for Externally_Built use "true";
19261 for Source_Files use ();
19262 for Library_Dir use "lib";
19263 for Library_Name use "a";
19264 for Library_Kind use "static";
19268 This is an alternative to the use of @code{pragma Linker_Options}. It is
19269 especially interesting in the context of systems with several interdependent
19270 static libraries where finding a proper linker order is not easy and best be
19271 left to the tools having visibility over project dependence information.
19274 In order to use an Ada library manually, you need to make sure that this
19275 library is on both your source and object path
19276 (see @ref{Search Paths and the Run-Time Library (RTL)}
19277 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19278 in an archive or a shared library, you need to specify the desired
19279 library at link time.
19281 For example, you can use the library @file{mylib} installed in
19282 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19285 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19290 This can be expressed more simply:
19295 when the following conditions are met:
19298 @file{/dir/my_lib_src} has been added by the user to the environment
19299 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19300 @file{ada_source_path}
19302 @file{/dir/my_lib_obj} has been added by the user to the environment
19303 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19304 @file{ada_object_path}
19306 a pragma @code{Linker_Options} has been added to one of the sources.
19309 @smallexample @c ada
19310 pragma Linker_Options ("-lmy_lib");
19314 @node Stand-alone Ada Libraries
19315 @section Stand-alone Ada Libraries
19316 @cindex Stand-alone library, building, using
19319 * Introduction to Stand-alone Libraries::
19320 * Building a Stand-alone Library::
19321 * Creating a Stand-alone Library to be used in a non-Ada context::
19322 * Restrictions in Stand-alone Libraries::
19325 @node Introduction to Stand-alone Libraries
19326 @subsection Introduction to Stand-alone Libraries
19329 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19331 elaborate the Ada units that are included in the library. In contrast with
19332 an ordinary library, which consists of all sources, objects and @file{ALI}
19334 library, a SAL may specify a restricted subset of compilation units
19335 to serve as a library interface. In this case, the fully
19336 self-sufficient set of files will normally consist of an objects
19337 archive, the sources of interface units' specs, and the @file{ALI}
19338 files of interface units.
19339 If an interface spec contains a generic unit or an inlined subprogram,
19341 source must also be provided; if the units that must be provided in the source
19342 form depend on other units, the source and @file{ALI} files of those must
19345 The main purpose of a SAL is to minimize the recompilation overhead of client
19346 applications when a new version of the library is installed. Specifically,
19347 if the interface sources have not changed, client applications do not need to
19348 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19349 version, controlled by @code{Library_Version} attribute, is not changed,
19350 then the clients do not need to be relinked.
19352 SALs also allow the library providers to minimize the amount of library source
19353 text exposed to the clients. Such ``information hiding'' might be useful or
19354 necessary for various reasons.
19356 Stand-alone libraries are also well suited to be used in an executable whose
19357 main routine is not written in Ada.
19359 @node Building a Stand-alone Library
19360 @subsection Building a Stand-alone Library
19363 GNAT's Project facility provides a simple way of building and installing
19364 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19365 To be a Stand-alone Library Project, in addition to the two attributes
19366 that make a project a Library Project (@code{Library_Name} and
19367 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19368 @code{Library_Interface} must be defined. For example:
19370 @smallexample @c projectfile
19372 for Library_Dir use "lib_dir";
19373 for Library_Name use "dummy";
19374 for Library_Interface use ("int1", "int1.child");
19379 Attribute @code{Library_Interface} has a non-empty string list value,
19380 each string in the list designating a unit contained in an immediate source
19381 of the project file.
19383 When a Stand-alone Library is built, first the binder is invoked to build
19384 a package whose name depends on the library name
19385 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19386 This binder-generated package includes initialization and
19387 finalization procedures whose
19388 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19390 above). The object corresponding to this package is included in the library.
19392 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19393 calling of these procedures if a static SAL is built, or if a shared SAL
19395 with the project-level attribute @code{Library_Auto_Init} set to
19398 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19399 (those that are listed in attribute @code{Library_Interface}) are copied to
19400 the Library Directory. As a consequence, only the Interface Units may be
19401 imported from Ada units outside of the library. If other units are imported,
19402 the binding phase will fail.
19404 The attribute @code{Library_Src_Dir} may be specified for a
19405 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19406 single string value. Its value must be the path (absolute or relative to the
19407 project directory) of an existing directory. This directory cannot be the
19408 object directory or one of the source directories, but it can be the same as
19409 the library directory. The sources of the Interface
19410 Units of the library that are needed by an Ada client of the library will be
19411 copied to the designated directory, called the Interface Copy directory.
19412 These sources include the specs of the Interface Units, but they may also
19413 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19414 are used, or when there is a generic unit in the spec. Before the sources
19415 are copied to the Interface Copy directory, an attempt is made to delete all
19416 files in the Interface Copy directory.
19418 Building stand-alone libraries by hand is somewhat tedious, but for those
19419 occasions when it is necessary here are the steps that you need to perform:
19422 Compile all library sources.
19425 Invoke the binder with the switch @option{-n} (No Ada main program),
19426 with all the @file{ALI} files of the interfaces, and
19427 with the switch @option{-L} to give specific names to the @code{init}
19428 and @code{final} procedures. For example:
19430 gnatbind -n int1.ali int2.ali -Lsal1
19434 Compile the binder generated file:
19440 Link the dynamic library with all the necessary object files,
19441 indicating to the linker the names of the @code{init} (and possibly
19442 @code{final}) procedures for automatic initialization (and finalization).
19443 The built library should be placed in a directory different from
19444 the object directory.
19447 Copy the @code{ALI} files of the interface to the library directory,
19448 add in this copy an indication that it is an interface to a SAL
19449 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19450 with letter ``P'') and make the modified copy of the @file{ALI} file
19455 Using SALs is not different from using other libraries
19456 (see @ref{Using a library}).
19458 @node Creating a Stand-alone Library to be used in a non-Ada context
19459 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19462 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19465 The only extra step required is to ensure that library interface subprograms
19466 are compatible with the main program, by means of @code{pragma Export}
19467 or @code{pragma Convention}.
19469 Here is an example of simple library interface for use with C main program:
19471 @smallexample @c ada
19472 package My_Package is
19474 procedure Do_Something;
19475 pragma Export (C, Do_Something, "do_something");
19477 procedure Do_Something_Else;
19478 pragma Export (C, Do_Something_Else, "do_something_else");
19484 On the foreign language side, you must provide a ``foreign'' view of the
19485 library interface; remember that it should contain elaboration routines in
19486 addition to interface subprograms.
19488 The example below shows the content of @code{mylib_interface.h} (note
19489 that there is no rule for the naming of this file, any name can be used)
19491 /* the library elaboration procedure */
19492 extern void mylibinit (void);
19494 /* the library finalization procedure */
19495 extern void mylibfinal (void);
19497 /* the interface exported by the library */
19498 extern void do_something (void);
19499 extern void do_something_else (void);
19503 Libraries built as explained above can be used from any program, provided
19504 that the elaboration procedures (named @code{mylibinit} in the previous
19505 example) are called before the library services are used. Any number of
19506 libraries can be used simultaneously, as long as the elaboration
19507 procedure of each library is called.
19509 Below is an example of a C program that uses the @code{mylib} library.
19512 #include "mylib_interface.h"
19517 /* First, elaborate the library before using it */
19520 /* Main program, using the library exported entities */
19522 do_something_else ();
19524 /* Library finalization at the end of the program */
19531 Note that invoking any library finalization procedure generated by
19532 @code{gnatbind} shuts down the Ada run-time environment.
19534 finalization of all Ada libraries must be performed at the end of the program.
19535 No call to these libraries or to the Ada run-time library should be made
19536 after the finalization phase.
19538 @node Restrictions in Stand-alone Libraries
19539 @subsection Restrictions in Stand-alone Libraries
19542 The pragmas listed below should be used with caution inside libraries,
19543 as they can create incompatibilities with other Ada libraries:
19545 @item pragma @code{Locking_Policy}
19546 @item pragma @code{Queuing_Policy}
19547 @item pragma @code{Task_Dispatching_Policy}
19548 @item pragma @code{Unreserve_All_Interrupts}
19552 When using a library that contains such pragmas, the user must make sure
19553 that all libraries use the same pragmas with the same values. Otherwise,
19554 @code{Program_Error} will
19555 be raised during the elaboration of the conflicting
19556 libraries. The usage of these pragmas and its consequences for the user
19557 should therefore be well documented.
19559 Similarly, the traceback in the exception occurrence mechanism should be
19560 enabled or disabled in a consistent manner across all libraries.
19561 Otherwise, Program_Error will be raised during the elaboration of the
19562 conflicting libraries.
19564 If the @code{Version} or @code{Body_Version}
19565 attributes are used inside a library, then you need to
19566 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19567 libraries, so that version identifiers can be properly computed.
19568 In practice these attributes are rarely used, so this is unlikely
19569 to be a consideration.
19571 @node Rebuilding the GNAT Run-Time Library
19572 @section Rebuilding the GNAT Run-Time Library
19573 @cindex GNAT Run-Time Library, rebuilding
19574 @cindex Building the GNAT Run-Time Library
19575 @cindex Rebuilding the GNAT Run-Time Library
19576 @cindex Run-Time Library, rebuilding
19579 It may be useful to recompile the GNAT library in various contexts, the
19580 most important one being the use of partition-wide configuration pragmas
19581 such as @code{Normalize_Scalars}. A special Makefile called
19582 @code{Makefile.adalib} is provided to that effect and can be found in
19583 the directory containing the GNAT library. The location of this
19584 directory depends on the way the GNAT environment has been installed and can
19585 be determined by means of the command:
19592 The last entry in the object search path usually contains the
19593 gnat library. This Makefile contains its own documentation and in
19594 particular the set of instructions needed to rebuild a new library and
19597 @node Using the GNU make Utility
19598 @chapter Using the GNU @code{make} Utility
19602 This chapter offers some examples of makefiles that solve specific
19603 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19604 make, make, GNU @code{make}}), nor does it try to replace the
19605 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19607 All the examples in this section are specific to the GNU version of
19608 make. Although @command{make} is a standard utility, and the basic language
19609 is the same, these examples use some advanced features found only in
19613 * Using gnatmake in a Makefile::
19614 * Automatically Creating a List of Directories::
19615 * Generating the Command Line Switches::
19616 * Overcoming Command Line Length Limits::
19619 @node Using gnatmake in a Makefile
19620 @section Using gnatmake in a Makefile
19625 Complex project organizations can be handled in a very powerful way by
19626 using GNU make combined with gnatmake. For instance, here is a Makefile
19627 which allows you to build each subsystem of a big project into a separate
19628 shared library. Such a makefile allows you to significantly reduce the link
19629 time of very big applications while maintaining full coherence at
19630 each step of the build process.
19632 The list of dependencies are handled automatically by
19633 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19634 the appropriate directories.
19636 Note that you should also read the example on how to automatically
19637 create the list of directories
19638 (@pxref{Automatically Creating a List of Directories})
19639 which might help you in case your project has a lot of subdirectories.
19644 @font@heightrm=cmr8
19647 ## This Makefile is intended to be used with the following directory
19649 ## - The sources are split into a series of csc (computer software components)
19650 ## Each of these csc is put in its own directory.
19651 ## Their name are referenced by the directory names.
19652 ## They will be compiled into shared library (although this would also work
19653 ## with static libraries
19654 ## - The main program (and possibly other packages that do not belong to any
19655 ## csc is put in the top level directory (where the Makefile is).
19656 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19657 ## \_ second_csc (sources) __ lib (will contain the library)
19659 ## Although this Makefile is build for shared library, it is easy to modify
19660 ## to build partial link objects instead (modify the lines with -shared and
19663 ## With this makefile, you can change any file in the system or add any new
19664 ## file, and everything will be recompiled correctly (only the relevant shared
19665 ## objects will be recompiled, and the main program will be re-linked).
19667 # The list of computer software component for your project. This might be
19668 # generated automatically.
19671 # Name of the main program (no extension)
19674 # If we need to build objects with -fPIC, uncomment the following line
19677 # The following variable should give the directory containing libgnat.so
19678 # You can get this directory through 'gnatls -v'. This is usually the last
19679 # directory in the Object_Path.
19682 # The directories for the libraries
19683 # (This macro expands the list of CSC to the list of shared libraries, you
19684 # could simply use the expanded form:
19685 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19686 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19688 $@{MAIN@}: objects $@{LIB_DIR@}
19689 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19690 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19693 # recompile the sources
19694 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19696 # Note: In a future version of GNAT, the following commands will be simplified
19697 # by a new tool, gnatmlib
19699 mkdir -p $@{dir $@@ @}
19700 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19701 cd $@{dir $@@ @} && cp -f ../*.ali .
19703 # The dependencies for the modules
19704 # Note that we have to force the expansion of *.o, since in some cases
19705 # make won't be able to do it itself.
19706 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19707 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19708 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19710 # Make sure all of the shared libraries are in the path before starting the
19713 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19716 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19717 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19718 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19719 $@{RM@} *.o *.ali $@{MAIN@}
19722 @node Automatically Creating a List of Directories
19723 @section Automatically Creating a List of Directories
19726 In most makefiles, you will have to specify a list of directories, and
19727 store it in a variable. For small projects, it is often easier to
19728 specify each of them by hand, since you then have full control over what
19729 is the proper order for these directories, which ones should be
19732 However, in larger projects, which might involve hundreds of
19733 subdirectories, it might be more convenient to generate this list
19736 The example below presents two methods. The first one, although less
19737 general, gives you more control over the list. It involves wildcard
19738 characters, that are automatically expanded by @command{make}. Its
19739 shortcoming is that you need to explicitly specify some of the
19740 organization of your project, such as for instance the directory tree
19741 depth, whether some directories are found in a separate tree, @enddots{}
19743 The second method is the most general one. It requires an external
19744 program, called @command{find}, which is standard on all Unix systems. All
19745 the directories found under a given root directory will be added to the
19751 @font@heightrm=cmr8
19754 # The examples below are based on the following directory hierarchy:
19755 # All the directories can contain any number of files
19756 # ROOT_DIRECTORY -> a -> aa -> aaa
19759 # -> b -> ba -> baa
19762 # This Makefile creates a variable called DIRS, that can be reused any time
19763 # you need this list (see the other examples in this section)
19765 # The root of your project's directory hierarchy
19769 # First method: specify explicitly the list of directories
19770 # This allows you to specify any subset of all the directories you need.
19773 DIRS := a/aa/ a/ab/ b/ba/
19776 # Second method: use wildcards
19777 # Note that the argument(s) to wildcard below should end with a '/'.
19778 # Since wildcards also return file names, we have to filter them out
19779 # to avoid duplicate directory names.
19780 # We thus use make's @code{dir} and @code{sort} functions.
19781 # It sets DIRs to the following value (note that the directories aaa and baa
19782 # are not given, unless you change the arguments to wildcard).
19783 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19786 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19787 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19790 # Third method: use an external program
19791 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19792 # This is the most complete command: it sets DIRs to the following value:
19793 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19796 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19800 @node Generating the Command Line Switches
19801 @section Generating the Command Line Switches
19804 Once you have created the list of directories as explained in the
19805 previous section (@pxref{Automatically Creating a List of Directories}),
19806 you can easily generate the command line arguments to pass to gnatmake.
19808 For the sake of completeness, this example assumes that the source path
19809 is not the same as the object path, and that you have two separate lists
19813 # see "Automatically creating a list of directories" to create
19818 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19819 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19822 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19825 @node Overcoming Command Line Length Limits
19826 @section Overcoming Command Line Length Limits
19829 One problem that might be encountered on big projects is that many
19830 operating systems limit the length of the command line. It is thus hard to give
19831 gnatmake the list of source and object directories.
19833 This example shows how you can set up environment variables, which will
19834 make @command{gnatmake} behave exactly as if the directories had been
19835 specified on the command line, but have a much higher length limit (or
19836 even none on most systems).
19838 It assumes that you have created a list of directories in your Makefile,
19839 using one of the methods presented in
19840 @ref{Automatically Creating a List of Directories}.
19841 For the sake of completeness, we assume that the object
19842 path (where the ALI files are found) is different from the sources patch.
19844 Note a small trick in the Makefile below: for efficiency reasons, we
19845 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19846 expanded immediately by @code{make}. This way we overcome the standard
19847 make behavior which is to expand the variables only when they are
19850 On Windows, if you are using the standard Windows command shell, you must
19851 replace colons with semicolons in the assignments to these variables.
19856 @font@heightrm=cmr8
19859 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19860 # This is the same thing as putting the -I arguments on the command line.
19861 # (the equivalent of using -aI on the command line would be to define
19862 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19863 # You can of course have different values for these variables.
19865 # Note also that we need to keep the previous values of these variables, since
19866 # they might have been set before running 'make' to specify where the GNAT
19867 # library is installed.
19869 # see "Automatically creating a list of directories" to create these
19875 space:=$@{empty@} $@{empty@}
19876 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19877 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19878 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19879 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19880 export ADA_INCLUDE_PATH
19881 export ADA_OBJECT_PATH
19888 @node Memory Management Issues
19889 @chapter Memory Management Issues
19892 This chapter describes some useful memory pools provided in the GNAT library
19893 and in particular the GNAT Debug Pool facility, which can be used to detect
19894 incorrect uses of access values (including ``dangling references'').
19896 It also describes the @command{gnatmem} tool, which can be used to track down
19901 * Some Useful Memory Pools::
19902 * The GNAT Debug Pool Facility::
19904 * The gnatmem Tool::
19908 @node Some Useful Memory Pools
19909 @section Some Useful Memory Pools
19910 @findex Memory Pool
19911 @cindex storage, pool
19914 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19915 storage pool. Allocations use the standard system call @code{malloc} while
19916 deallocations use the standard system call @code{free}. No reclamation is
19917 performed when the pool goes out of scope. For performance reasons, the
19918 standard default Ada allocators/deallocators do not use any explicit storage
19919 pools but if they did, they could use this storage pool without any change in
19920 behavior. That is why this storage pool is used when the user
19921 manages to make the default implicit allocator explicit as in this example:
19922 @smallexample @c ada
19923 type T1 is access Something;
19924 -- no Storage pool is defined for T2
19925 type T2 is access Something_Else;
19926 for T2'Storage_Pool use T1'Storage_Pool;
19927 -- the above is equivalent to
19928 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19932 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19933 pool. The allocation strategy is similar to @code{Pool_Local}'s
19934 except that the all
19935 storage allocated with this pool is reclaimed when the pool object goes out of
19936 scope. This pool provides a explicit mechanism similar to the implicit one
19937 provided by several Ada 83 compilers for allocations performed through a local
19938 access type and whose purpose was to reclaim memory when exiting the
19939 scope of a given local access. As an example, the following program does not
19940 leak memory even though it does not perform explicit deallocation:
19942 @smallexample @c ada
19943 with System.Pool_Local;
19944 procedure Pooloc1 is
19945 procedure Internal is
19946 type A is access Integer;
19947 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19948 for A'Storage_Pool use X;
19951 for I in 1 .. 50 loop
19956 for I in 1 .. 100 loop
19963 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19964 @code{Storage_Size} is specified for an access type.
19965 The whole storage for the pool is
19966 allocated at once, usually on the stack at the point where the access type is
19967 elaborated. It is automatically reclaimed when exiting the scope where the
19968 access type is defined. This package is not intended to be used directly by the
19969 user and it is implicitly used for each such declaration:
19971 @smallexample @c ada
19972 type T1 is access Something;
19973 for T1'Storage_Size use 10_000;
19976 @node The GNAT Debug Pool Facility
19977 @section The GNAT Debug Pool Facility
19979 @cindex storage, pool, memory corruption
19982 The use of unchecked deallocation and unchecked conversion can easily
19983 lead to incorrect memory references. The problems generated by such
19984 references are usually difficult to tackle because the symptoms can be
19985 very remote from the origin of the problem. In such cases, it is
19986 very helpful to detect the problem as early as possible. This is the
19987 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19989 In order to use the GNAT specific debugging pool, the user must
19990 associate a debug pool object with each of the access types that may be
19991 related to suspected memory problems. See Ada Reference Manual 13.11.
19992 @smallexample @c ada
19993 type Ptr is access Some_Type;
19994 Pool : GNAT.Debug_Pools.Debug_Pool;
19995 for Ptr'Storage_Pool use Pool;
19999 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
20000 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
20001 allow the user to redefine allocation and deallocation strategies. They
20002 also provide a checkpoint for each dereference, through the use of
20003 the primitive operation @code{Dereference} which is implicitly called at
20004 each dereference of an access value.
20006 Once an access type has been associated with a debug pool, operations on
20007 values of the type may raise four distinct exceptions,
20008 which correspond to four potential kinds of memory corruption:
20011 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
20013 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
20015 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
20017 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
20021 For types associated with a Debug_Pool, dynamic allocation is performed using
20022 the standard GNAT allocation routine. References to all allocated chunks of
20023 memory are kept in an internal dictionary. Several deallocation strategies are
20024 provided, whereupon the user can choose to release the memory to the system,
20025 keep it allocated for further invalid access checks, or fill it with an easily
20026 recognizable pattern for debug sessions. The memory pattern is the old IBM
20027 hexadecimal convention: @code{16#DEADBEEF#}.
20029 See the documentation in the file g-debpoo.ads for more information on the
20030 various strategies.
20032 Upon each dereference, a check is made that the access value denotes a
20033 properly allocated memory location. Here is a complete example of use of
20034 @code{Debug_Pools}, that includes typical instances of memory corruption:
20035 @smallexample @c ada
20039 with Gnat.Io; use Gnat.Io;
20040 with Unchecked_Deallocation;
20041 with Unchecked_Conversion;
20042 with GNAT.Debug_Pools;
20043 with System.Storage_Elements;
20044 with Ada.Exceptions; use Ada.Exceptions;
20045 procedure Debug_Pool_Test is
20047 type T is access Integer;
20048 type U is access all T;
20050 P : GNAT.Debug_Pools.Debug_Pool;
20051 for T'Storage_Pool use P;
20053 procedure Free is new Unchecked_Deallocation (Integer, T);
20054 function UC is new Unchecked_Conversion (U, T);
20057 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
20067 Put_Line (Integer'Image(B.all));
20069 when E : others => Put_Line ("raised: " & Exception_Name (E));
20074 when E : others => Put_Line ("raised: " & Exception_Name (E));
20078 Put_Line (Integer'Image(B.all));
20080 when E : others => Put_Line ("raised: " & Exception_Name (E));
20085 when E : others => Put_Line ("raised: " & Exception_Name (E));
20088 end Debug_Pool_Test;
20092 The debug pool mechanism provides the following precise diagnostics on the
20093 execution of this erroneous program:
20096 Total allocated bytes : 0
20097 Total deallocated bytes : 0
20098 Current Water Mark: 0
20102 Total allocated bytes : 8
20103 Total deallocated bytes : 0
20104 Current Water Mark: 8
20107 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
20108 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
20109 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
20110 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20112 Total allocated bytes : 8
20113 Total deallocated bytes : 4
20114 Current Water Mark: 4
20119 @node The gnatmem Tool
20120 @section The @command{gnatmem} Tool
20124 The @code{gnatmem} utility monitors dynamic allocation and
20125 deallocation activity in a program, and displays information about
20126 incorrect deallocations and possible sources of memory leaks.
20127 It is designed to work in association with a static runtime library
20128 only and in this context provides three types of information:
20131 General information concerning memory management, such as the total
20132 number of allocations and deallocations, the amount of allocated
20133 memory and the high water mark, i.e.@: the largest amount of allocated
20134 memory in the course of program execution.
20137 Backtraces for all incorrect deallocations, that is to say deallocations
20138 which do not correspond to a valid allocation.
20141 Information on each allocation that is potentially the origin of a memory
20146 * Running gnatmem::
20147 * Switches for gnatmem::
20148 * Example of gnatmem Usage::
20151 @node Running gnatmem
20152 @subsection Running @code{gnatmem}
20155 @code{gnatmem} makes use of the output created by the special version of
20156 allocation and deallocation routines that record call information. This
20157 allows to obtain accurate dynamic memory usage history at a minimal cost to
20158 the execution speed. Note however, that @code{gnatmem} is not supported on
20159 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20160 Solaris and Windows NT/2000/XP (x86).
20163 The @code{gnatmem} command has the form
20166 $ gnatmem @ovar{switches} user_program
20170 The program must have been linked with the instrumented version of the
20171 allocation and deallocation routines. This is done by linking with the
20172 @file{libgmem.a} library. For correct symbolic backtrace information,
20173 the user program should be compiled with debugging options
20174 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20177 $ gnatmake -g my_program -largs -lgmem
20181 As library @file{libgmem.a} contains an alternate body for package
20182 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20183 when an executable is linked with library @file{libgmem.a}. It is then not
20184 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20187 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20188 This file contains information about all allocations and deallocations
20189 performed by the program. It is produced by the instrumented allocations and
20190 deallocations routines and will be used by @code{gnatmem}.
20192 In order to produce symbolic backtrace information for allocations and
20193 deallocations performed by the GNAT run-time library, you need to use a
20194 version of that library that has been compiled with the @option{-g} switch
20195 (see @ref{Rebuilding the GNAT Run-Time Library}).
20197 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20198 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20199 @option{-i} switch, gnatmem will assume that this file can be found in the
20200 current directory. For example, after you have executed @file{my_program},
20201 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20204 $ gnatmem my_program
20208 This will produce the output with the following format:
20210 *************** debut cc
20212 $ gnatmem my_program
20216 Total number of allocations : 45
20217 Total number of deallocations : 6
20218 Final Water Mark (non freed mem) : 11.29 Kilobytes
20219 High Water Mark : 11.40 Kilobytes
20224 Allocation Root # 2
20225 -------------------
20226 Number of non freed allocations : 11
20227 Final Water Mark (non freed mem) : 1.16 Kilobytes
20228 High Water Mark : 1.27 Kilobytes
20230 my_program.adb:23 my_program.alloc
20236 The first block of output gives general information. In this case, the
20237 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20238 Unchecked_Deallocation routine occurred.
20241 Subsequent paragraphs display information on all allocation roots.
20242 An allocation root is a specific point in the execution of the program
20243 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20244 construct. This root is represented by an execution backtrace (or subprogram
20245 call stack). By default the backtrace depth for allocations roots is 1, so
20246 that a root corresponds exactly to a source location. The backtrace can
20247 be made deeper, to make the root more specific.
20249 @node Switches for gnatmem
20250 @subsection Switches for @code{gnatmem}
20253 @code{gnatmem} recognizes the following switches:
20258 @cindex @option{-q} (@code{gnatmem})
20259 Quiet. Gives the minimum output needed to identify the origin of the
20260 memory leaks. Omits statistical information.
20263 @cindex @var{N} (@code{gnatmem})
20264 N is an integer literal (usually between 1 and 10) which controls the
20265 depth of the backtraces defining allocation root. The default value for
20266 N is 1. The deeper the backtrace, the more precise the localization of
20267 the root. Note that the total number of roots can depend on this
20268 parameter. This parameter must be specified @emph{before} the name of the
20269 executable to be analyzed, to avoid ambiguity.
20272 @cindex @option{-b} (@code{gnatmem})
20273 This switch has the same effect as just depth parameter.
20275 @item -i @var{file}
20276 @cindex @option{-i} (@code{gnatmem})
20277 Do the @code{gnatmem} processing starting from @file{file}, rather than
20278 @file{gmem.out} in the current directory.
20281 @cindex @option{-m} (@code{gnatmem})
20282 This switch causes @code{gnatmem} to mask the allocation roots that have less
20283 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20284 examine even the roots that didn't result in leaks.
20287 @cindex @option{-s} (@code{gnatmem})
20288 This switch causes @code{gnatmem} to sort the allocation roots according to the
20289 specified order of sort criteria, each identified by a single letter. The
20290 currently supported criteria are @code{n, h, w} standing respectively for
20291 number of unfreed allocations, high watermark, and final watermark
20292 corresponding to a specific root. The default order is @code{nwh}.
20296 @node Example of gnatmem Usage
20297 @subsection Example of @code{gnatmem} Usage
20300 The following example shows the use of @code{gnatmem}
20301 on a simple memory-leaking program.
20302 Suppose that we have the following Ada program:
20304 @smallexample @c ada
20307 with Unchecked_Deallocation;
20308 procedure Test_Gm is
20310 type T is array (1..1000) of Integer;
20311 type Ptr is access T;
20312 procedure Free is new Unchecked_Deallocation (T, Ptr);
20315 procedure My_Alloc is
20320 procedure My_DeAlloc is
20328 for I in 1 .. 5 loop
20329 for J in I .. 5 loop
20340 The program needs to be compiled with debugging option and linked with
20341 @code{gmem} library:
20344 $ gnatmake -g test_gm -largs -lgmem
20348 Then we execute the program as usual:
20355 Then @code{gnatmem} is invoked simply with
20361 which produces the following output (result may vary on different platforms):
20366 Total number of allocations : 18
20367 Total number of deallocations : 5
20368 Final Water Mark (non freed mem) : 53.00 Kilobytes
20369 High Water Mark : 56.90 Kilobytes
20371 Allocation Root # 1
20372 -------------------
20373 Number of non freed allocations : 11
20374 Final Water Mark (non freed mem) : 42.97 Kilobytes
20375 High Water Mark : 46.88 Kilobytes
20377 test_gm.adb:11 test_gm.my_alloc
20379 Allocation Root # 2
20380 -------------------
20381 Number of non freed allocations : 1
20382 Final Water Mark (non freed mem) : 10.02 Kilobytes
20383 High Water Mark : 10.02 Kilobytes
20385 s-secsta.adb:81 system.secondary_stack.ss_init
20387 Allocation Root # 3
20388 -------------------
20389 Number of non freed allocations : 1
20390 Final Water Mark (non freed mem) : 12 Bytes
20391 High Water Mark : 12 Bytes
20393 s-secsta.adb:181 system.secondary_stack.ss_init
20397 Note that the GNAT run time contains itself a certain number of
20398 allocations that have no corresponding deallocation,
20399 as shown here for root #2 and root
20400 #3. This is a normal behavior when the number of non-freed allocations
20401 is one, it allocates dynamic data structures that the run time needs for
20402 the complete lifetime of the program. Note also that there is only one
20403 allocation root in the user program with a single line back trace:
20404 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20405 program shows that 'My_Alloc' is called at 2 different points in the
20406 source (line 21 and line 24). If those two allocation roots need to be
20407 distinguished, the backtrace depth parameter can be used:
20410 $ gnatmem 3 test_gm
20414 which will give the following output:
20419 Total number of allocations : 18
20420 Total number of deallocations : 5
20421 Final Water Mark (non freed mem) : 53.00 Kilobytes
20422 High Water Mark : 56.90 Kilobytes
20424 Allocation Root # 1
20425 -------------------
20426 Number of non freed allocations : 10
20427 Final Water Mark (non freed mem) : 39.06 Kilobytes
20428 High Water Mark : 42.97 Kilobytes
20430 test_gm.adb:11 test_gm.my_alloc
20431 test_gm.adb:24 test_gm
20432 b_test_gm.c:52 main
20434 Allocation Root # 2
20435 -------------------
20436 Number of non freed allocations : 1
20437 Final Water Mark (non freed mem) : 10.02 Kilobytes
20438 High Water Mark : 10.02 Kilobytes
20440 s-secsta.adb:81 system.secondary_stack.ss_init
20441 s-secsta.adb:283 <system__secondary_stack___elabb>
20442 b_test_gm.c:33 adainit
20444 Allocation Root # 3
20445 -------------------
20446 Number of non freed allocations : 1
20447 Final Water Mark (non freed mem) : 3.91 Kilobytes
20448 High Water Mark : 3.91 Kilobytes
20450 test_gm.adb:11 test_gm.my_alloc
20451 test_gm.adb:21 test_gm
20452 b_test_gm.c:52 main
20454 Allocation Root # 4
20455 -------------------
20456 Number of non freed allocations : 1
20457 Final Water Mark (non freed mem) : 12 Bytes
20458 High Water Mark : 12 Bytes
20460 s-secsta.adb:181 system.secondary_stack.ss_init
20461 s-secsta.adb:283 <system__secondary_stack___elabb>
20462 b_test_gm.c:33 adainit
20466 The allocation root #1 of the first example has been split in 2 roots #1
20467 and #3 thanks to the more precise associated backtrace.
20471 @node Stack Related Facilities
20472 @chapter Stack Related Facilities
20475 This chapter describes some useful tools associated with stack
20476 checking and analysis. In
20477 particular, it deals with dynamic and static stack usage measurements.
20480 * Stack Overflow Checking::
20481 * Static Stack Usage Analysis::
20482 * Dynamic Stack Usage Analysis::
20485 @node Stack Overflow Checking
20486 @section Stack Overflow Checking
20487 @cindex Stack Overflow Checking
20488 @cindex -fstack-check
20491 For most operating systems, @command{gcc} does not perform stack overflow
20492 checking by default. This means that if the main environment task or
20493 some other task exceeds the available stack space, then unpredictable
20494 behavior will occur. Most native systems offer some level of protection by
20495 adding a guard page at the end of each task stack. This mechanism is usually
20496 not enough for dealing properly with stack overflow situations because
20497 a large local variable could ``jump'' above the guard page.
20498 Furthermore, when the
20499 guard page is hit, there may not be any space left on the stack for executing
20500 the exception propagation code. Enabling stack checking avoids
20503 To activate stack checking, compile all units with the gcc option
20504 @option{-fstack-check}. For example:
20507 gcc -c -fstack-check package1.adb
20511 Units compiled with this option will generate extra instructions to check
20512 that any use of the stack (for procedure calls or for declaring local
20513 variables in declare blocks) does not exceed the available stack space.
20514 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20516 For declared tasks, the stack size is controlled by the size
20517 given in an applicable @code{Storage_Size} pragma or by the value specified
20518 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20519 the default size as defined in the GNAT runtime otherwise.
20521 For the environment task, the stack size depends on
20522 system defaults and is unknown to the compiler. Stack checking
20523 may still work correctly if a fixed
20524 size stack is allocated, but this cannot be guaranteed.
20526 To ensure that a clean exception is signalled for stack
20527 overflow, set the environment variable
20528 @env{GNAT_STACK_LIMIT} to indicate the maximum
20529 stack area that can be used, as in:
20530 @cindex GNAT_STACK_LIMIT
20533 SET GNAT_STACK_LIMIT 1600
20537 The limit is given in kilobytes, so the above declaration would
20538 set the stack limit of the environment task to 1.6 megabytes.
20539 Note that the only purpose of this usage is to limit the amount
20540 of stack used by the environment task. If it is necessary to
20541 increase the amount of stack for the environment task, then this
20542 is an operating systems issue, and must be addressed with the
20543 appropriate operating systems commands.
20546 To have a fixed size stack in the environment task, the stack must be put
20547 in the P0 address space and its size specified. Use these switches to
20551 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20555 The quotes are required to keep case. The number after @samp{STACK=} is the
20556 size of the environmental task stack in pagelets (512 bytes). In this example
20557 the stack size is about 2 megabytes.
20560 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20561 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20562 more details about the @option{/p0image} qualifier and the @option{stack}
20566 @node Static Stack Usage Analysis
20567 @section Static Stack Usage Analysis
20568 @cindex Static Stack Usage Analysis
20569 @cindex -fstack-usage
20572 A unit compiled with @option{-fstack-usage} will generate an extra file
20574 the maximum amount of stack used, on a per-function basis.
20575 The file has the same
20576 basename as the target object file with a @file{.su} extension.
20577 Each line of this file is made up of three fields:
20581 The name of the function.
20585 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20588 The second field corresponds to the size of the known part of the function
20591 The qualifier @code{static} means that the function frame size
20593 It usually means that all local variables have a static size.
20594 In this case, the second field is a reliable measure of the function stack
20597 The qualifier @code{dynamic} means that the function frame size is not static.
20598 It happens mainly when some local variables have a dynamic size. When this
20599 qualifier appears alone, the second field is not a reliable measure
20600 of the function stack analysis. When it is qualified with @code{bounded}, it
20601 means that the second field is a reliable maximum of the function stack
20604 @node Dynamic Stack Usage Analysis
20605 @section Dynamic Stack Usage Analysis
20608 It is possible to measure the maximum amount of stack used by a task, by
20609 adding a switch to @command{gnatbind}, as:
20612 $ gnatbind -u0 file
20616 With this option, at each task termination, its stack usage is output on
20618 It is not always convenient to output the stack usage when the program
20619 is still running. Hence, it is possible to delay this output until program
20620 termination. for a given number of tasks specified as the argument of the
20621 @option{-u} option. For instance:
20624 $ gnatbind -u100 file
20628 will buffer the stack usage information of the first 100 tasks to terminate and
20629 output this info at program termination. Results are displayed in four
20633 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20640 is a number associated with each task.
20643 is the name of the task analyzed.
20646 is the maximum size for the stack.
20649 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20650 is not entirely analyzed, and it's not possible to know exactly how
20651 much has actually been used. The report thus contains the theoretical stack usage
20652 (Value) and the possible variation (Variation) around this value.
20657 The environment task stack, e.g., the stack that contains the main unit, is
20658 only processed when the environment variable GNAT_STACK_LIMIT is set.
20661 @c *********************************
20663 @c *********************************
20664 @node Verifying Properties Using gnatcheck
20665 @chapter Verifying Properties Using @command{gnatcheck}
20667 @cindex @command{gnatcheck}
20670 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20671 of Ada source files according to a given set of semantic rules.
20674 In order to check compliance with a given rule, @command{gnatcheck} has to
20675 semantically analyze the Ada sources.
20676 Therefore, checks can only be performed on
20677 legal Ada units. Moreover, when a unit depends semantically upon units located
20678 outside the current directory, the source search path has to be provided when
20679 calling @command{gnatcheck}, either through a specified project file or
20680 through @command{gnatcheck} switches as described below.
20682 A number of rules are predefined in @command{gnatcheck} and are described
20683 later in this chapter.
20684 You can also add new rules, by modifying the @command{gnatcheck} code and
20685 rebuilding the tool. In order to add a simple rule making some local checks,
20686 a small amount of straightforward ASIS-based programming is usually needed.
20688 Project support for @command{gnatcheck} is provided by the GNAT
20689 driver (see @ref{The GNAT Driver and Project Files}).
20691 Invoking @command{gnatcheck} on the command line has the form:
20694 $ gnatcheck @ovar{switches} @{@var{filename}@}
20695 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20696 @r{[}-cargs @var{gcc_switches}@r{]} -rules @var{rule_options}
20703 @var{switches} specify the general tool options
20706 Each @var{filename} is the name (including the extension) of a source
20707 file to process. ``Wildcards'' are allowed, and
20708 the file name may contain path information.
20711 Each @var{arg_list_filename} is the name (including the extension) of a text
20712 file containing the names of the source files to process, separated by spaces
20716 @var{gcc_switches} is a list of switches for
20717 @command{gcc}. They will be passed on to all compiler invocations made by
20718 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20719 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20720 and use the @option{-gnatec} switch to set the configuration file.
20723 @var{rule_options} is a list of options for controlling a set of
20724 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20728 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be
20732 * Format of the Report File::
20733 * General gnatcheck Switches::
20734 * gnatcheck Rule Options::
20735 * Adding the Results of Compiler Checks to gnatcheck Output::
20736 * Project-Wide Checks::
20738 * Predefined Rules::
20741 @node Format of the Report File
20742 @section Format of the Report File
20743 @cindex Report file (for @code{gnatcheck})
20746 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20748 It also creates a text file that
20749 contains the complete report of the last gnatcheck run. By default this file
20750 is named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the
20751 current directory; the @option{^-o^/OUTPUT^} option can be used to change the
20752 name and/or location of the report file. This report contains:
20754 @item date and time of @command{gnatcheck} run, the version of
20755 the tool that has generated this report and the full parameters
20756 of the @command{gnatcheck} invocation;
20757 @item list of enabled rules;
20758 @item total number of detected violations;
20759 @item list of source files where rule violations have been detected;
20760 @item list of source files where no violations have been detected.
20763 @node General gnatcheck Switches
20764 @section General @command{gnatcheck} Switches
20767 The following switches control the general @command{gnatcheck} behavior
20771 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20773 Process all units including those with read-only ALI files such as
20774 those from the GNAT Run-Time library.
20778 @cindex @option{-d} (@command{gnatcheck})
20783 @cindex @option{-dd} (@command{gnatcheck})
20785 Progress indicator mode (for use in GPS).
20788 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20790 List the predefined and user-defined rules. For more details see
20791 @ref{Predefined Rules}.
20793 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20795 Use full source locations references in the report file. For a construct from
20796 a generic instantiation a full source location is a chain from the location
20797 of this construct in the generic unit to the place where this unit is
20800 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20802 Duplicate all the output sent to @file{stderr} into a log file. The log file
20803 is named @file{gnatcheck.log} and is located in the current directory.
20805 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20806 @item ^-m@i{nnnn}^/DIAGNOSTIC_LIMIT=@i{nnnn}^
20807 Maximum number of diagnostics to be sent to @file{stdout}, where @i{nnnn} is in
20808 the range 0@dots{}1000;
20809 the default value is 500. Zero means that there is no limitation on
20810 the number of diagnostic messages to be output.
20812 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20814 Quiet mode. All the diagnostics about rule violations are placed in the
20815 @command{gnatcheck} report file only, without duplication on @file{stdout}.
20817 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20819 Short format of the report file (no version information, no list of applied
20820 rules, no list of checked sources is included)
20822 @cindex @option{^--include-file=@var{file}^/INCLUDE_FILE=@var{file}^} (@command{gnatcheck})
20823 @item ^--include-file^/INCLUDE_FILE^
20824 Append the content of the specified text file to the report file
20826 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20828 Print out execution time.
20830 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20831 @item ^-v^/VERBOSE^
20832 Verbose mode; @command{gnatcheck} generates version information and then
20833 a trace of sources being processed.
20835 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20836 @item ^-o ^/OUTPUT=^@var{report_file}
20837 Set name of report file file to @var{report_file} .
20842 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20843 @option{^-s2^/BY_RULES^} or
20844 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20845 then the @command{gnatcheck} report file will only contain sections
20846 explicitly denoted by these options.
20848 @node gnatcheck Rule Options
20849 @section @command{gnatcheck} Rule Options
20852 The following options control the processing performed by
20853 @command{gnatcheck}.
20856 @cindex @option{+ALL} (@command{gnatcheck})
20858 Turn all the rule checks ON.
20860 @cindex @option{-ALL} (@command{gnatcheck})
20862 Turn all the rule checks OFF.
20864 @cindex @option{+R} (@command{gnatcheck})
20865 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20866 Turn on the check for a specified rule with the specified parameter, if any.
20867 @var{rule_id} must be the identifier of one of the currently implemented rules
20868 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20869 are not case-sensitive. The @var{param} item must
20870 be a string representing a valid parameter(s) for the specified rule.
20871 If it contains any space characters then this string must be enclosed in
20874 @cindex @option{-R} (@command{gnatcheck})
20875 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20876 Turn off the check for a specified rule with the specified parameter, if any.
20878 @cindex @option{-from} (@command{gnatcheck})
20879 @item -from=@var{rule_option_filename}
20880 Read the rule options from the text file @var{rule_option_filename}, referred
20881 to as a ``coding standard file'' below.
20886 The default behavior is that all the rule checks are disabled.
20888 A coding standard file is a text file that contains a set of rule options
20890 @cindex Coding standard file (for @code{gnatcheck})
20891 The file may contain empty lines and Ada-style comments (comment
20892 lines and end-of-line comments). There can be several rule options on a
20893 single line (separated by a space).
20895 A coding standard file may reference other coding standard files by including
20896 more @option{-from=@var{rule_option_filename}}
20897 options, each such option being replaced with the content of the
20898 corresponding coding standard file during processing. In case a
20899 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20900 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20901 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20902 processing fails with an error message.
20905 @node Adding the Results of Compiler Checks to gnatcheck Output
20906 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20909 The @command{gnatcheck} tool can include in the generated diagnostic messages
20911 the report file the results of the checks performed by the compiler. Though
20912 disabled by default, this effect may be obtained by using @option{+R} with
20913 the following rule identifiers and parameters:
20917 To record restrictions violations (which are performed by the compiler if the
20918 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20919 use the @code{Restrictions} rule
20920 with the same parameters as pragma
20921 @code{Restrictions} or @code{Restriction_Warnings}.
20924 To record compiler style checks (@pxref{Style Checking}), use the
20925 @code{Style_Checks} rule.
20926 This rule takes a parameter in one of the following forms:
20930 which enables the standard style checks corresponding to the @option{-gnatyy}
20931 GNAT style check option, or
20934 a string with the same
20935 structure and semantics as the @code{string_LITERAL} parameter of the
20936 GNAT pragma @code{Style_Checks}
20937 (for further information about this pragma,
20938 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
20943 @code{+RStyle_Checks:O} rule option activates
20944 the compiler style check that corresponds to
20945 @code{-gnatyO} style check option.
20948 To record compiler warnings (@pxref{Warning Message Control}), use the
20949 @code{Warnings} rule with a parameter that is a valid
20950 @i{static_string_expression} argument of the GNAT pragma @code{Warnings}
20951 (for further information about this pragma,
20952 @pxref{Pragma Warnings,,,gnat_rm, GNAT Reference Manual}).
20953 Note that in case of gnatcheck
20954 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20955 all the specific warnings, but not suppresses the warning mode,
20956 and 'e' parameter, corresponding to @option{-gnatwe} that means
20957 "treat warnings as errors", does not have any effect.
20961 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20962 option with the corresponding restriction name as a parameter. @code{-R} is
20963 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20964 warnings and style checks, use the corresponding warning and style options.
20966 @node Project-Wide Checks
20967 @section Project-Wide Checks
20968 @cindex Project-wide checks (for @command{gnatcheck})
20971 In order to perform checks on all units of a given project, you can use
20972 the GNAT driver along with the @option{-P} option:
20974 gnat check -Pproj -rules -from=my_rules
20978 If the project @code{proj} depends upon other projects, you can perform
20979 checks on the project closure using the @option{-U} option:
20981 gnat check -Pproj -U -rules -from=my_rules
20985 Finally, if not all the units are relevant to a particular main
20986 program in the project closure, you can perform checks for the set
20987 of units needed to create a given main program (unit closure) using
20988 the @option{-U} option followed by the name of the main unit:
20990 gnat check -Pproj -U main -rules -from=my_rules
20994 @node Rule exemption
20995 @section Rule exemption
20996 @cindex Rule exemption (for @command{gnatcheck})
20999 One of the most useful applications of @command{gnatcheck} is to
21000 automate the enforcement of project-specific coding standards,
21001 for example in safety-critical systems where particular features
21002 must be restricted in order to simplify the certification effort.
21003 However, it may sometimes be appropriate to violate a coding standard rule,
21004 and in such cases the rationale for the violation should be provided
21005 in the source program itself so that the individuals
21006 reviewing or maintaining the program can immediately understand the intent.
21008 The @command{gnatcheck} tool supports this practice with the notion of
21009 a ``rule exemption'' covering a specific source code section. Normally
21010 rule violation messages are issued both on @file{stderr}
21011 and in a report file. In contrast, exempted violations are not listed on
21012 @file{stderr}; thus users invoking @command{gnatcheck} interactively
21013 (e.g. in its GPS interface) do not need to pay attention to known and
21014 justified violations. However, exempted violations along with their
21015 justification are documented in a special section of the report file that
21016 @command{gnatcheck} generates.
21019 * Using pragma Annotate to Control Rule Exemption::
21020 * gnatcheck Annotations Rules::
21023 @node Using pragma Annotate to Control Rule Exemption
21024 @subsection Using pragma @code{Annotate} to Control Rule Exemption
21025 @cindex Using pragma Annotate to control rule exemption
21028 Rule exemption is controlled by pragma @code{Annotate} when its first
21029 argument is ``gnatcheck''. The syntax of @command{gnatcheck}'s
21030 exemption control annotations is as follows:
21032 @smallexample @c ada
21034 pragma Annotate (gnatcheck, @i{exemption_control}, @i{Rule_Name}, [@i{justification}]);
21036 @i{exemption_control} ::= Exempt_On | Exempt_Off
21038 @i{Rule_Name} ::= string_literal
21040 @i{justification} ::= string_literal
21045 When a @command{gnatcheck} annotation has more then four arguments,
21046 @command{gnatcheck} issues a warning and ignores the additional arguments.
21047 If the additional arguments do not follow the syntax above,
21048 @command{gnatcheck} emits a warning and ignores the annotation.
21050 The @i{@code{Rule_Name}} argument should be the name of some existing
21051 @command{gnatcheck} rule.
21052 Otherwise a warning message is generated and the pragma is
21053 ignored. If @code{Rule_Name} denotes a rule that is not activated by the given
21054 @command{gnatcheck} call, the pragma is ignored and no warning is issued.
21056 A source code section where an exemption is active for a given rule is
21057 delimited by an @code{exempt_on} and @code{exempt_off} annotation pair:
21059 @smallexample @c ada
21060 pragma Annotate (gnatcheck, Exempt_On, Rule_Name, "justification");
21061 -- source code section
21062 pragma Annotate (gnatcheck, Exempt_Off, Rule_Name);
21066 @node gnatcheck Annotations Rules
21067 @subsection @command{gnatcheck} Annotations Rules
21068 @cindex @command{gnatcheck} annotations rules
21073 An ``Exempt_Off'' annotation can only appear after a corresponding
21074 ``Exempt_On'' annotation.
21077 Exempted source code sections are only based on the source location of the
21078 annotations. Any source construct between the two
21079 annotations is part of the exempted source code section.
21082 Exempted source code sections for different rules are independent. They can
21083 be nested or intersect with one another without limitation.
21084 Creating nested or intersecting source code sections for the same rule is
21088 Malformed exempted source code sections are reported by a warning, and
21089 the corresponding rule exemptions are ignored.
21092 When an exempted source code section does not contain at least one violation
21093 of the exempted rule, a warning is emitted on @file{stderr}.
21096 If an ``Exempt_On'' annotation pragma does not have a matching
21097 ``Exempt_Off'' annotation pragma in the same compilation unit, then the
21098 exemption for the given rule is ignored and a warning is issued.
21102 @node Predefined Rules
21103 @section Predefined Rules
21104 @cindex Predefined rules (for @command{gnatcheck})
21107 @c (Jan 2007) Since the global rules are still under development and are not
21108 @c documented, there is no point in explaining the difference between
21109 @c global and local rules
21111 A rule in @command{gnatcheck} is either local or global.
21112 A @emph{local rule} is a rule that applies to a well-defined section
21113 of a program and that can be checked by analyzing only this section.
21114 A @emph{global rule} requires analysis of some global properties of the
21115 whole program (mostly related to the program call graph).
21116 As of @value{NOW}, the implementation of global rules should be
21117 considered to be at a preliminary stage. You can use the
21118 @option{+GLOBAL} option to enable all the global rules, and the
21119 @option{-GLOBAL} rule option to disable all the global rules.
21121 All the global rules in the list below are
21122 so indicated by marking them ``GLOBAL''.
21123 This +GLOBAL and -GLOBAL options are not
21124 included in the list of gnatcheck options above, because at the moment they
21125 are considered as a temporary debug options.
21127 @command{gnatcheck} performs rule checks for generic
21128 instances only for global rules. This limitation may be relaxed in a later
21133 The following subsections document the rules implemented in
21134 @command{gnatcheck}.
21135 The subsection title is the same as the rule identifier, which may be
21136 used as a parameter of the @option{+R} or @option{-R} options.
21140 * Abstract_Type_Declarations::
21141 * Anonymous_Arrays::
21142 * Anonymous_Subtypes::
21144 * Boolean_Relational_Operators::
21146 * Ceiling_Violations::
21148 * Complex_Inlined_Subprograms::
21149 * Controlled_Type_Declarations::
21150 * Declarations_In_Blocks::
21151 * Deep_Inheritance_Hierarchies::
21152 * Deeply_Nested_Generics::
21153 * Deeply_Nested_Inlining::
21155 * Deeply_Nested_Local_Inlining::
21157 * Default_Parameters::
21158 * Direct_Calls_To_Primitives::
21159 * Discriminated_Records::
21160 * Enumeration_Ranges_In_CASE_Statements::
21161 * Exceptions_As_Control_Flow::
21162 * Exits_From_Conditional_Loops::
21163 * EXIT_Statements_With_No_Loop_Name::
21164 * Expanded_Loop_Exit_Names::
21165 * Explicit_Full_Discrete_Ranges::
21166 * Float_Equality_Checks::
21167 * Forbidden_Attributes::
21168 * Forbidden_Pragmas::
21169 * Function_Style_Procedures::
21170 * Generics_In_Subprograms::
21171 * GOTO_Statements::
21172 * Implicit_IN_Mode_Parameters::
21173 * Implicit_SMALL_For_Fixed_Point_Types::
21174 * Improperly_Located_Instantiations::
21175 * Improper_Returns::
21176 * Library_Level_Subprograms::
21179 * Improperly_Called_Protected_Entries::
21182 * Misnamed_Controlling_Parameters::
21183 * Misnamed_Identifiers::
21184 * Multiple_Entries_In_Protected_Definitions::
21186 * Non_Qualified_Aggregates::
21187 * Non_Short_Circuit_Operators::
21188 * Non_SPARK_Attributes::
21189 * Non_Tagged_Derived_Types::
21190 * Non_Visible_Exceptions::
21191 * Numeric_Literals::
21192 * OTHERS_In_Aggregates::
21193 * OTHERS_In_CASE_Statements::
21194 * OTHERS_In_Exception_Handlers::
21195 * Outer_Loop_Exits::
21196 * Overloaded_Operators::
21197 * Overly_Nested_Control_Structures::
21198 * Parameters_Out_Of_Order::
21199 * Positional_Actuals_For_Defaulted_Generic_Parameters::
21200 * Positional_Actuals_For_Defaulted_Parameters::
21201 * Positional_Components::
21202 * Positional_Generic_Parameters::
21203 * Positional_Parameters::
21204 * Predefined_Numeric_Types::
21205 * Raising_External_Exceptions::
21206 * Raising_Predefined_Exceptions::
21207 * Separate_Numeric_Error_Handlers::
21210 * Side_Effect_Functions::
21213 * Too_Many_Parents::
21214 * Unassigned_OUT_Parameters::
21215 * Uncommented_BEGIN_In_Package_Bodies::
21216 * Unconditional_Exits::
21217 * Unconstrained_Array_Returns::
21218 * Universal_Ranges::
21219 * Unnamed_Blocks_And_Loops::
21221 * Unused_Subprograms::
21223 * USE_PACKAGE_Clauses::
21224 * Visible_Components::
21225 * Volatile_Objects_Without_Address_Clauses::
21229 @node Abstract_Type_Declarations
21230 @subsection @code{Abstract_Type_Declarations}
21231 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
21234 Flag all declarations of abstract types. For an abstract private
21235 type, both the private and full type declarations are flagged.
21237 This rule has no parameters.
21240 @node Anonymous_Arrays
21241 @subsection @code{Anonymous_Arrays}
21242 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21245 Flag all anonymous array type definitions (by Ada semantics these can only
21246 occur in object declarations).
21248 This rule has no parameters.
21250 @node Anonymous_Subtypes
21251 @subsection @code{Anonymous_Subtypes}
21252 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21255 Flag all uses of anonymous subtypes (except cases when subtype indication
21256 is a part of a record component definition, and this subtype indication
21257 depends on a discriminant). A use of an anonymous subtype is
21258 any instance of a subtype indication with a constraint, other than one
21259 that occurs immediately within a subtype declaration. Any use of a range
21260 other than as a constraint used immediately within a subtype declaration
21261 is considered as an anonymous subtype.
21263 An effect of this rule is that @code{for} loops such as the following are
21264 flagged (since @code{1..N} is formally a ``range''):
21266 @smallexample @c ada
21267 for I in 1 .. N loop
21273 Declaring an explicit subtype solves the problem:
21275 @smallexample @c ada
21276 subtype S is Integer range 1..N;
21284 This rule has no parameters.
21287 @subsection @code{Blocks}
21288 @cindex @code{Blocks} rule (for @command{gnatcheck})
21291 Flag each block statement.
21293 This rule has no parameters.
21295 @node Boolean_Relational_Operators
21296 @subsection @code{Boolean_Relational_Operators}
21297 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21300 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21301 ``>='', ``='' and ``/='') for the predefined Boolean type.
21302 (This rule is useful in enforcing the SPARK language restrictions.)
21304 Calls to predefined relational operators of any type derived from
21305 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21306 with these designators, and uses of operators that are renamings
21307 of the predefined relational operators for @code{Standard.Boolean},
21308 are likewise not detected.
21310 This rule has no parameters.
21313 @node Ceiling_Violations
21314 @subsection @code{Ceiling5_Violations} (under construction, GLOBAL)
21315 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21318 Flag invocations of a protected operation by a task whose priority exceeds
21319 the protected object's ceiling.
21321 As of @value{NOW}, this rule has the following limitations:
21326 We consider only pragmas Priority and Interrupt_Priority as means to define
21327 a task/protected operation priority. We do not consider the effect of using
21328 Ada.Dynamic_Priorities.Set_Priority procedure;
21331 We consider only base task priorities, and no priority inheritance. That is,
21332 we do not make a difference between calls issued during task activation and
21333 execution of the sequence of statements from task body;
21336 Any situation when the priority of protected operation caller is set by a
21337 dynamic expression (that is, the corresponding Priority or
21338 Interrupt_Priority pragma has a non-static expression as an argument) we
21339 treat as a priority inconsistency (and, therefore, detect this situation).
21343 At the moment the notion of the main subprogram is not implemented in
21344 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21345 if this subprogram can be a main subprogram of a partition) changes the
21346 priority of an environment task. So if we have more then one such pragma in
21347 the set of processed sources, the pragma that is processed last, defines the
21348 priority of an environment task.
21350 This rule has no parameters.
21353 @node Controlled_Type_Declarations
21354 @subsection @code{Controlled_Type_Declarations}
21355 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21358 Flag all declarations of controlled types. A declaration of a private type
21359 is flagged if its full declaration declares a controlled type. A declaration
21360 of a derived type is flagged if its ancestor type is controlled. Subtype
21361 declarations are not checked. A declaration of a type that itself is not a
21362 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21363 component is not checked.
21365 This rule has no parameters.
21368 @node Complex_Inlined_Subprograms
21369 @subsection @code{Complex_Inlined_Subprograms}
21370 @cindex @code{Complex_Inlined_Subprograms} rule (for @command{gnatcheck})
21373 Flags a subprogram (or generic subprogram) if
21374 pragma Inline is applied to the subprogram and at least one of the following
21379 it contains at least one complex declaration such as a subprogram body,
21380 package, task, protected declaration, or a generic instantiation
21381 (except instantiation of @code{Ada.Unchecked_Conversion});
21384 it contains at least one complex statement such as a loop, a case
21385 or a if statement, or a short circuit control form;
21388 the number of statements exceeds
21389 a value specified by the @option{N} rule parameter;
21393 This rule has the following (mandatory) parameter for the @option{+R} option:
21397 Positive integer specifying the maximum allowed total number of statements
21398 in the subprogram body.
21402 @node Declarations_In_Blocks
21403 @subsection @code{Declarations_In_Blocks}
21404 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21407 Flag all block statements containing local declarations. A @code{declare}
21408 block with an empty @i{declarative_part} or with a @i{declarative part}
21409 containing only pragmas and/or @code{use} clauses is not flagged.
21411 This rule has no parameters.
21414 @node Deep_Inheritance_Hierarchies
21415 @subsection @code{Deep_Inheritance_Hierarchies}
21416 @cindex @code{Deep_Inheritance_Hierarchies} rule (for @command{gnatcheck})
21419 Flags a tagged derived type declaration or an interface type declaration if
21420 its depth (in its inheritance
21421 hierarchy) exceeds the value specified by the @option{N} rule parameter.
21423 The inheritance depth of a tagged type or interface type is defined as 0 for
21424 a type with no parent and no progenitor, and otherwise as 1 + max of the
21425 depths of the immediate parent and immediate progenitors.
21427 This rule does not flag private extension
21428 declarations. In the case of a private extension, the corresponding full
21429 declaration is checked.
21431 This rule has the following (mandatory) parameter for the @option{+R} option:
21435 Integer not less than -1 specifying the maximal allowed depth of any inheritance
21436 hierarchy. If the rule parameter is set to -1, the rule flags all the declarations
21437 of tagged and interface types.
21441 @node Deeply_Nested_Generics
21442 @subsection @code{Deeply_Nested_Generics}
21443 @cindex @code{Deeply_Nested_Generics} rule (for @command{gnatcheck})
21446 Flags a generic declaration nested in another generic declaration if
21447 the nesting level of the inner generic exceeds
21448 a value specified by the @option{N} rule parameter.
21449 The nesting level is the number of generic declaratons that enclose the given
21450 (generic) declaration. Formal packages are not flagged by this rule.
21452 This rule has the following (mandatory) parameters for the @option{+R} option:
21456 Positive integer specifying the maximal allowed nesting level
21457 for a generic declaration.
21460 @node Deeply_Nested_Inlining
21461 @subsection @code{Deeply_Nested_Inlining}
21462 @cindex @code{Deeply_Nested_Inlining} rule (for @command{gnatcheck})
21465 Flags a subprogram (or generic subprogram) if
21466 pragma Inline has been applied to the subprogram but the subprogram
21467 calls to another inlined subprogram that results in nested inlining
21468 with nesting depth exceeding the value specified by the
21469 @option{N} rule parameter.
21471 This rule requires the global analysis of all the compilation units that
21472 are @command{gnatcheck} arguments; such analysis may affect the tool's
21475 This rule has the following (mandatory) parameter for the @option{+R} option:
21479 Positive integer specifying the maximal allowed level of nested inlining.
21484 @node Deeply_Nested_Local_Inlining
21485 @subsection @code{Deeply_Nested_Local_Inlining}
21486 @cindex @code{Deeply_Nested_Local_Inlining} rule (for @command{gnatcheck})
21489 Flags a subprogram body if a pragma @code{Inline} is applied to the
21490 corresponding subprogram (or generic subprogram) and the body contains a call
21491 to another inlined subprogram that results in nested inlining with nesting
21492 depth more then a value specified by the @option{N} rule parameter.
21493 This rule is similar to @code{Deeply_Nested_Inlining} rule, but it
21494 assumes that calls to subprograms in
21495 with'ed units are not inlided, so all the analysis of the depth of inlining is
21496 limited by the compilation unit where the subprogram body is located and the
21497 units it depends semantically upon. Such analysis may be usefull for the case
21498 when neiter @option{-gnatn} nor @option{-gnatN} option is used when building
21501 This rule has the following (mandatory) parameters for the @option{+R} option:
21505 Positive integer specifying the maximal allowed level of nested inlining.
21510 @node Default_Parameters
21511 @subsection @code{Default_Parameters}
21512 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21515 Flag all default expressions for subprogram parameters. Parameter
21516 declarations of formal and generic subprograms are also checked.
21518 This rule has no parameters.
21521 @node Direct_Calls_To_Primitives
21522 @subsection @code{Direct_Calls_To_Primitives}
21523 @cindex @code{Direct_Calls_To_Primitives} rule (for @command{gnatcheck})
21526 Flags any non-dispatching call to a dispatching primitive operation, except
21527 for the common idiom where a primitive subprogram for a tagged type
21528 directly calls the same primitive subprogram of the type's immediate ancestor.
21530 This rule has no parameters.
21533 @node Discriminated_Records
21534 @subsection @code{Discriminated_Records}
21535 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21538 Flag all declarations of record types with discriminants. Only the
21539 declarations of record and record extension types are checked. Incomplete,
21540 formal, private, derived and private extension type declarations are not
21541 checked. Task and protected type declarations also are not checked.
21543 This rule has no parameters.
21546 @node Enumeration_Ranges_In_CASE_Statements
21547 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21548 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21551 Flag each use of a range of enumeration literals as a choice in a
21552 @code{case} statement.
21553 All forms for specifying a range (explicit ranges
21554 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21555 An enumeration range is
21556 flagged even if contains exactly one enumeration value or no values at all. A
21557 type derived from an enumeration type is considered as an enumeration type.
21559 This rule helps prevent maintenance problems arising from adding an
21560 enumeration value to a type and having it implicitly handled by an existing
21561 @code{case} statement with an enumeration range that includes the new literal.
21563 This rule has no parameters.
21566 @node Exceptions_As_Control_Flow
21567 @subsection @code{Exceptions_As_Control_Flow}
21568 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21571 Flag each place where an exception is explicitly raised and handled in the
21572 same subprogram body. A @code{raise} statement in an exception handler,
21573 package body, task body or entry body is not flagged.
21575 The rule has no parameters.
21577 @node Exits_From_Conditional_Loops
21578 @subsection @code{Exits_From_Conditional_Loops}
21579 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21582 Flag any exit statement if it transfers the control out of a @code{for} loop
21583 or a @code{while} loop. This includes cases when the @code{exit} statement
21584 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21585 in some @code{for} or @code{while} loop, but transfers the control from some
21586 outer (inconditional) @code{loop} statement.
21588 The rule has no parameters.
21591 @node EXIT_Statements_With_No_Loop_Name
21592 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21593 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21596 Flag each @code{exit} statement that does not specify the name of the loop
21599 The rule has no parameters.
21602 @node Expanded_Loop_Exit_Names
21603 @subsection @code{Expanded_Loop_Exit_Names}
21604 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21607 Flag all expanded loop names in @code{exit} statements.
21609 This rule has no parameters.
21611 @node Explicit_Full_Discrete_Ranges
21612 @subsection @code{Explicit_Full_Discrete_Ranges}
21613 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21616 Flag each discrete range that has the form @code{A'First .. A'Last}.
21618 This rule has no parameters.
21620 @node Float_Equality_Checks
21621 @subsection @code{Float_Equality_Checks}
21622 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21625 Flag all calls to the predefined equality operations for floating-point types.
21626 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21627 User-defined equality operations are not flagged, nor are ``@code{=}''
21628 and ``@code{/=}'' operations for fixed-point types.
21630 This rule has no parameters.
21633 @node Forbidden_Attributes
21634 @subsection @code{Forbidden_Attributes}
21635 @cindex @code{Forbidden_Attributes} rule (for @command{gnatcheck})
21638 Flag each use of the specified attributes. The attributes to be detected are
21639 named in the rule's parameters.
21641 This rule has the following parameters:
21644 @item For the @option{+R} option
21647 @item @emph{Attribute_Designator}
21648 Adds the specified attribute to the set of attributes to be detected and sets
21649 the detection checks for all the specified attributes ON.
21650 If @emph{Attribute_Designator}
21651 does not denote any attribute defined in the Ada standard
21653 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
21654 Manual}, it is treated as the name of unknown attribute.
21657 All the GNAT-specific attributes are detected; this sets
21658 the detection checks for all the specified attributes ON.
21661 All attributes are detected; this sets the rule ON.
21664 @item For the @option{-R} option
21666 @item @emph{Attribute_Designator}
21667 Removes the specified attribute from the set of attributes to be
21668 detected without affecting detection checks for
21669 other attributes. If @emph{Attribute_Designator} does not correspond to any
21670 attribute defined in the Ada standard or in
21671 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference Manual},
21672 this option is treated as turning OFF detection of all unknown attributes.
21675 Turn OFF detection of all GNAT-specific attributes
21678 Clear the list of the attributes to be detected and
21684 Parameters are not case sensitive. If @emph{Attribute_Designator} does not
21685 have the syntax of an Ada identifier and therefore can not be considered as a
21686 (part of an) attribute designator, a diagnostic message is generated and the
21687 corresponding parameter is ignored. (If an attribute allows a static
21688 expression to be a part of the attribute designator, this expression is
21689 ignored by this rule.)
21691 When more then one parameter is given in the same rule option, the parameters
21692 must be separated by commas.
21694 If more then one option for this rule is specified for the gnatcheck call, a
21695 new option overrides the previous one(s).
21697 The @option{+R} option with no parameters turns the rule ON, with the set of
21698 attributes to be detected defined by the previous rule options.
21699 (By default this set is empty, so if the only option specified for the rule is
21700 @option{+RForbidden_Attributes} (with
21701 no parameter), then the rule is enabled, but it does not detect anything).
21702 The @option{-R} option with no parameter turns the rule OFF, but it does not
21703 affect the set of attributes to be detected.
21706 @node Forbidden_Pragmas
21707 @subsection @code{Forbidden_Pragmas}
21708 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21711 Flag each use of the specified pragmas. The pragmas to be detected
21712 are named in the rule's parameters.
21714 This rule has the following parameters:
21717 @item For the @option{+R} option
21720 @item @emph{Pragma_Name}
21721 Adds the specified pragma to the set of pragmas to be
21722 checked and sets the checks for all the specified pragmas
21723 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21724 does not correspond to any pragma name defined in the Ada
21725 standard or to the name of a GNAT-specific pragma defined
21726 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21727 Manual}, it is treated as the name of unknown pragma.
21730 All the GNAT-specific pragmas are detected; this sets
21731 the checks for all the specified pragmas ON.
21734 All pragmas are detected; this sets the rule ON.
21737 @item For the @option{-R} option
21739 @item @emph{Pragma_Name}
21740 Removes the specified pragma from the set of pragmas to be
21741 checked without affecting checks for
21742 other pragmas. @emph{Pragma_Name} is treated as a name
21743 of a pragma. If it does not correspond to any pragma
21744 defined in the Ada standard or to any name defined in
21745 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21746 this option is treated as turning OFF detection of all unknown pragmas.
21749 Turn OFF detection of all GNAT-specific pragmas
21752 Clear the list of the pragmas to be detected and
21758 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21759 the syntax of an Ada identifier and therefore can not be considered
21760 as a pragma name, a diagnostic message is generated and the corresponding
21761 parameter is ignored.
21763 When more then one parameter is given in the same rule option, the parameters
21764 must be separated by a comma.
21766 If more then one option for this rule is specified for the @command{gnatcheck}
21767 call, a new option overrides the previous one(s).
21769 The @option{+R} option with no parameters turns the rule ON with the set of
21770 pragmas to be detected defined by the previous rule options.
21771 (By default this set is empty, so if the only option specified for the rule is
21772 @option{+RForbidden_Pragmas} (with
21773 no parameter), then the rule is enabled, but it does not detect anything).
21774 The @option{-R} option with no parameter turns the rule OFF, but it does not
21775 affect the set of pragmas to be detected.
21780 @node Function_Style_Procedures
21781 @subsection @code{Function_Style_Procedures}
21782 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21785 Flag each procedure that can be rewritten as a function. A procedure can be
21786 converted into a function if it has exactly one parameter of mode @code{out}
21787 and no parameters of mode @code{in out}. Procedure declarations,
21788 formal procedure declarations, and generic procedure declarations are always
21790 bodies and body stubs are flagged only if they do not have corresponding
21791 separate declarations. Procedure renamings and procedure instantiations are
21794 If a procedure can be rewritten as a function, but its @code{out} parameter is
21795 of a limited type, it is not flagged.
21797 Protected procedures are not flagged. Null procedures also are not flagged.
21799 This rule has no parameters.
21802 @node Generics_In_Subprograms
21803 @subsection @code{Generics_In_Subprograms}
21804 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21807 Flag each declaration of a generic unit in a subprogram. Generic
21808 declarations in the bodies of generic subprograms are also flagged.
21809 A generic unit nested in another generic unit is not flagged.
21810 If a generic unit is
21811 declared in a local package that is declared in a subprogram body, the
21812 generic unit is flagged.
21814 This rule has no parameters.
21817 @node GOTO_Statements
21818 @subsection @code{GOTO_Statements}
21819 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21822 Flag each occurrence of a @code{goto} statement.
21824 This rule has no parameters.
21827 @node Implicit_IN_Mode_Parameters
21828 @subsection @code{Implicit_IN_Mode_Parameters}
21829 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21832 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21833 Note that @code{access} parameters, although they technically behave
21834 like @code{in} parameters, are not flagged.
21836 This rule has no parameters.
21839 @node Implicit_SMALL_For_Fixed_Point_Types
21840 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21841 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21844 Flag each fixed point type declaration that lacks an explicit
21845 representation clause to define its @code{'Small} value.
21846 Since @code{'Small} can be defined only for ordinary fixed point types,
21847 decimal fixed point type declarations are not checked.
21849 This rule has no parameters.
21852 @node Improperly_Located_Instantiations
21853 @subsection @code{Improperly_Located_Instantiations}
21854 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21857 Flag all generic instantiations in library-level package specs
21858 (including library generic packages) and in all subprogram bodies.
21860 Instantiations in task and entry bodies are not flagged. Instantiations in the
21861 bodies of protected subprograms are flagged.
21863 This rule has no parameters.
21867 @node Improper_Returns
21868 @subsection @code{Improper_Returns}
21869 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21872 Flag each explicit @code{return} statement in procedures, and
21873 multiple @code{return} statements in functions.
21874 Diagnostic messages are generated for all @code{return} statements
21875 in a procedure (thus each procedure must be written so that it
21876 returns implicitly at the end of its statement part),
21877 and for all @code{return} statements in a function after the first one.
21878 This rule supports the stylistic convention that each subprogram
21879 should have no more than one point of normal return.
21881 This rule has no parameters.
21884 @node Library_Level_Subprograms
21885 @subsection @code{Library_Level_Subprograms}
21886 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21889 Flag all library-level subprograms (including generic subprogram instantiations).
21891 This rule has no parameters.
21894 @node Local_Packages
21895 @subsection @code{Local_Packages}
21896 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21899 Flag all local packages declared in package and generic package
21901 Local packages in bodies are not flagged.
21903 This rule has no parameters.
21906 @node Improperly_Called_Protected_Entries
21907 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21908 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21911 Flag each protected entry that can be called from more than one task.
21913 This rule has no parameters.
21917 @subsection @code{Metrics}
21918 @cindex @code{Metrics} rule (for @command{gnatcheck})
21921 There is a set of checks based on computing a metric value and comparing the
21922 result with the specified upper (or lower, depending on a specific metric)
21923 value specified for a given metric. A construct is flagged if a given metric
21924 is applicable (can be computed) for it and the computed value is greater
21925 then (lover then) the specified upper (lower) bound.
21927 The name of any metric-based rule consists of the prefix @code{Metrics_}
21928 followed by the name of the corresponding metric (see the table below).
21929 For @option{+R} option, each metric-based rule has a numeric parameter
21930 specifying the bound (integer or real, depending on a metric), @option{-R}
21931 option for metric rules does not have a parameter.
21933 The following table shows the metric names for that the corresponding
21934 metrics-based checks are supported by gnatcheck, including the
21935 constraint that must be satisfied by the bound that is specified for the check
21936 and what bound - upper (U) or lower (L) - should be specified.
21938 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21940 @headitem Check Name @tab Description @tab Bounds Value
21943 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21945 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21946 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21947 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21948 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21952 The meaning and the computed values for all these metrics are exactly
21953 the same as for the corresponding metrics in @command{gnatmetric}.
21955 @emph{Example:} the rule
21957 +RMetrics_Cyclomatic_Complexity : 7
21960 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21962 To turn OFF the check for cyclomatic complexity metric, use the following option:
21964 -RMetrics_Cyclomatic_Complexity
21968 @node Misnamed_Controlling_Parameters
21969 @subsection @code{Misnamed_Controlling_Parameters}
21970 @cindex @code{Misnamed_Controlling_Parameters} rule (for @command{gnatcheck})
21973 Flags a declaration of a dispatching operation, if the first parameter is
21974 not a controlling one and its name is not @code{This} (the check for
21975 parameter name is not case-sensitive). Declarations of dispatching functions
21976 with controlling result and no controlling parameter are never flagged.
21978 A subprogram body declaration, subprogram renaming declaration or subprogram
21979 body stub is flagged only if it is not a completion of a prior subprogram
21982 This rule has no parameters.
21986 @node Misnamed_Identifiers
21987 @subsection @code{Misnamed_Identifiers}
21988 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21991 Flag the declaration of each identifier that does not have a suffix
21992 corresponding to the kind of entity being declared.
21993 The following declarations are checked:
22000 subtype declarations
22003 constant declarations (but not number declarations)
22006 package renaming declarations (but not generic package renaming
22011 This rule may have parameters. When used without parameters, the rule enforces
22012 the following checks:
22016 type-defining names end with @code{_T}, unless the type is an access type,
22017 in which case the suffix must be @code{_A}
22019 constant names end with @code{_C}
22021 names defining package renamings end with @code{_R}
22025 Defining identifiers from incomplete type declarations are never flagged.
22027 For a private type declaration (including private extensions), the defining
22028 identifier from the private type declaration is checked against the type
22029 suffix (even if the corresponding full declaration is an access type
22030 declaration), and the defining identifier from the corresponding full type
22031 declaration is not checked.
22034 For a deferred constant, the defining name in the corresponding full constant
22035 declaration is not checked.
22037 Defining names of formal types are not checked.
22039 The rule may have the following parameters:
22043 For the @option{+R} option:
22046 Sets the default listed above for all the names to be checked.
22048 @item Type_Suffix=@emph{string}
22049 Specifies the suffix for a type name.
22051 @item Access_Suffix=@emph{string}
22052 Specifies the suffix for an access type name. If
22053 this parameter is set, it overrides for access
22054 types the suffix set by the @code{Type_Suffix} parameter.
22055 For access types, @emph{string} may have the following format:
22056 @emph{suffix1(suffix2)}. That means that an access type name
22057 should have the @emph{suffix1} suffix except for the case when
22058 the designated type is also an access type, in this case the
22059 type name should have the @emph{suffix1 & suffix2} suffix.
22061 @item Class_Access_Suffix=@emph{string}
22062 Specifies the suffix for the name of an access type that points to some class-wide
22063 type. If this parameter is set, it overrides for such access
22064 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
22067 @item Class_Subtype_Suffix=@emph{string}
22068 Specifies the suffix for the name of a subtype that denotes a class-wide type.
22070 @item Constant_Suffix=@emph{string}
22071 Specifies the suffix for a constant name.
22073 @item Renaming_Suffix=@emph{string}
22074 Specifies the suffix for a package renaming name.
22078 For the @option{-R} option:
22081 Remove all the suffixes specified for the
22082 identifier suffix checks, whether by default or
22083 as specified by other rule parameters. All the
22084 checks for this rule are disabled as a result.
22087 Removes the suffix specified for types. This
22088 disables checks for types but does not disable
22089 any other checks for this rule (including the
22090 check for access type names if @code{Access_Suffix} is
22093 @item Access_Suffix
22094 Removes the suffix specified for access types.
22095 This disables checks for access type names but
22096 does not disable any other checks for this rule.
22097 If @code{Type_Suffix} is set, access type names are
22098 checked as ordinary type names.
22100 @item Class_Access_Suffix
22101 Removes the suffix specified for access types pointing to class-wide
22102 type. This disables specific checks for names of access types pointing to
22103 class-wide types but does not disable any other checks for this rule.
22104 If @code{Type_Suffix} is set, access type names are
22105 checked as ordinary type names. If @code{Access_Suffix} is set, these
22106 access types are checked as any other access type name.
22108 @item Class_Subtype_Suffix=@emph{string}
22109 Removes the suffix specified for subtype names.
22110 This disables checks for subtype names but
22111 does not disable any other checks for this rule.
22113 @item Constant_Suffix
22114 Removes the suffix specified for constants. This
22115 disables checks for constant names but does not
22116 disable any other checks for this rule.
22118 @item Renaming_Suffix
22119 Removes the suffix specified for package
22120 renamings. This disables checks for package
22121 renamings but does not disable any other checks
22127 If more than one parameter is used, parameters must be separated by commas.
22129 If more than one option is specified for the @command{gnatcheck} invocation,
22130 a new option overrides the previous one(s).
22132 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
22134 name suffixes specified by previous options used for this rule.
22136 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
22137 all the checks but keeps
22138 all the suffixes specified by previous options used for this rule.
22140 The @emph{string} value must be a valid suffix for an Ada identifier (after
22141 trimming all the leading and trailing space characters, if any).
22142 Parameters are not case sensitive, except the @emph{string} part.
22144 If any error is detected in a rule parameter, the parameter is ignored.
22145 In such a case the options that are set for the rule are not
22150 @node Multiple_Entries_In_Protected_Definitions
22151 @subsection @code{Multiple_Entries_In_Protected_Definitions}
22152 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
22155 Flag each protected definition (i.e., each protected object/type declaration)
22156 that defines more than one entry.
22157 Diagnostic messages are generated for all the entry declarations
22158 except the first one. An entry family is counted as one entry. Entries from
22159 the private part of the protected definition are also checked.
22161 This rule has no parameters.
22164 @subsection @code{Name_Clashes}
22165 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
22168 Check that certain names are not used as defining identifiers. To activate
22169 this rule, you need to supply a reference to the dictionary file(s) as a rule
22170 parameter(s) (more then one dictionary file can be specified). If no
22171 dictionary file is set, this rule will not cause anything to be flagged.
22172 Only defining occurrences, not references, are checked.
22173 The check is not case-sensitive.
22175 This rule is enabled by default, but without setting any corresponding
22176 dictionary file(s); thus the default effect is to do no checks.
22178 A dictionary file is a plain text file. The maximum line length for this file
22179 is 1024 characters. If the line is longer then this limit, extra characters
22182 Each line can be either an empty line, a comment line, or a line containing
22183 a list of identifiers separated by space or HT characters.
22184 A comment is an Ada-style comment (from @code{--} to end-of-line).
22185 Identifiers must follow the Ada syntax for identifiers.
22186 A line containing one or more identifiers may end with a comment.
22188 @node Non_Qualified_Aggregates
22189 @subsection @code{Non_Qualified_Aggregates}
22190 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
22193 Flag each non-qualified aggregate.
22194 A non-qualified aggregate is an
22195 aggregate that is not the expression of a qualified expression. A
22196 string literal is not considered an aggregate, but an array
22197 aggregate of a string type is considered as a normal aggregate.
22198 Aggregates of anonymous array types are not flagged.
22200 This rule has no parameters.
22203 @node Non_Short_Circuit_Operators
22204 @subsection @code{Non_Short_Circuit_Operators}
22205 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
22208 Flag all calls to predefined @code{and} and @code{or} operators for
22209 any boolean type. Calls to
22210 user-defined @code{and} and @code{or} and to operators defined by renaming
22211 declarations are not flagged. Calls to predefined @code{and} and @code{or}
22212 operators for modular types or boolean array types are not flagged.
22214 This rule has no parameters.
22218 @node Non_SPARK_Attributes
22219 @subsection @code{Non_SPARK_Attributes}
22220 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
22223 The SPARK language defines the following subset of Ada 95 attribute
22224 designators as those that can be used in SPARK programs. The use of
22225 any other attribute is flagged.
22228 @item @code{'Adjacent}
22231 @item @code{'Ceiling}
22232 @item @code{'Component_Size}
22233 @item @code{'Compose}
22234 @item @code{'Copy_Sign}
22235 @item @code{'Delta}
22236 @item @code{'Denorm}
22237 @item @code{'Digits}
22238 @item @code{'Exponent}
22239 @item @code{'First}
22240 @item @code{'Floor}
22242 @item @code{'Fraction}
22244 @item @code{'Leading_Part}
22245 @item @code{'Length}
22246 @item @code{'Machine}
22247 @item @code{'Machine_Emax}
22248 @item @code{'Machine_Emin}
22249 @item @code{'Machine_Mantissa}
22250 @item @code{'Machine_Overflows}
22251 @item @code{'Machine_Radix}
22252 @item @code{'Machine_Rounds}
22255 @item @code{'Model}
22256 @item @code{'Model_Emin}
22257 @item @code{'Model_Epsilon}
22258 @item @code{'Model_Mantissa}
22259 @item @code{'Model_Small}
22260 @item @code{'Modulus}
22263 @item @code{'Range}
22264 @item @code{'Remainder}
22265 @item @code{'Rounding}
22266 @item @code{'Safe_First}
22267 @item @code{'Safe_Last}
22268 @item @code{'Scaling}
22269 @item @code{'Signed_Zeros}
22271 @item @code{'Small}
22273 @item @code{'Truncation}
22274 @item @code{'Unbiased_Rounding}
22276 @item @code{'Valid}
22280 This rule has no parameters.
22283 @node Non_Tagged_Derived_Types
22284 @subsection @code{Non_Tagged_Derived_Types}
22285 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
22288 Flag all derived type declarations that do not have a record extension part.
22290 This rule has no parameters.
22294 @node Non_Visible_Exceptions
22295 @subsection @code{Non_Visible_Exceptions}
22296 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
22299 Flag constructs leading to the possibility of propagating an exception
22300 out of the scope in which the exception is declared.
22301 Two cases are detected:
22305 An exception declaration in a subprogram body, task body or block
22306 statement is flagged if the body or statement does not contain a handler for
22307 that exception or a handler with an @code{others} choice.
22310 A @code{raise} statement in an exception handler of a subprogram body,
22311 task body or block statement is flagged if it (re)raises a locally
22312 declared exception. This may occur under the following circumstances:
22315 it explicitly raises a locally declared exception, or
22317 it does not specify an exception name (i.e., it is simply @code{raise;})
22318 and the enclosing handler contains a locally declared exception in its
22324 Renamings of local exceptions are not flagged.
22326 This rule has no parameters.
22329 @node Numeric_Literals
22330 @subsection @code{Numeric_Literals}
22331 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
22334 Flag each use of a numeric literal in an index expression, and in any
22335 circumstance except for the following:
22339 a literal occurring in the initialization expression for a constant
22340 declaration or a named number declaration, or
22343 an integer literal that is less than or equal to a value
22344 specified by the @option{N} rule parameter.
22348 This rule may have the following parameters for the @option{+R} option:
22352 @emph{N} is an integer literal used as the maximal value that is not flagged
22353 (i.e., integer literals not exceeding this value are allowed)
22356 All integer literals are flagged
22360 If no parameters are set, the maximum unflagged value is 1.
22362 The last specified check limit (or the fact that there is no limit at
22363 all) is used when multiple @option{+R} options appear.
22365 The @option{-R} option for this rule has no parameters.
22366 It disables the rule but retains the last specified maximum unflagged value.
22367 If the @option{+R} option subsequently appears, this value is used as the
22368 threshold for the check.
22371 @node OTHERS_In_Aggregates
22372 @subsection @code{OTHERS_In_Aggregates}
22373 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
22376 Flag each use of an @code{others} choice in extension aggregates.
22377 In record and array aggregates, an @code{others} choice is flagged unless
22378 it is used to refer to all components, or to all but one component.
22380 If, in case of a named array aggregate, there are two associations, one
22381 with an @code{others} choice and another with a discrete range, the
22382 @code{others} choice is flagged even if the discrete range specifies
22383 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
22385 This rule has no parameters.
22387 @node OTHERS_In_CASE_Statements
22388 @subsection @code{OTHERS_In_CASE_Statements}
22389 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
22392 Flag any use of an @code{others} choice in a @code{case} statement.
22394 This rule has no parameters.
22396 @node OTHERS_In_Exception_Handlers
22397 @subsection @code{OTHERS_In_Exception_Handlers}
22398 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
22401 Flag any use of an @code{others} choice in an exception handler.
22403 This rule has no parameters.
22406 @node Outer_Loop_Exits
22407 @subsection @code{Outer_Loop_Exits}
22408 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
22411 Flag each @code{exit} statement containing a loop name that is not the name
22412 of the immediately enclosing @code{loop} statement.
22414 This rule has no parameters.
22417 @node Overloaded_Operators
22418 @subsection @code{Overloaded_Operators}
22419 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
22422 Flag each function declaration that overloads an operator symbol.
22423 A function body is checked only if the body does not have a
22424 separate spec. Formal functions are also checked. For a
22425 renaming declaration, only renaming-as-declaration is checked
22427 This rule has no parameters.
22430 @node Overly_Nested_Control_Structures
22431 @subsection @code{Overly_Nested_Control_Structures}
22432 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
22435 Flag each control structure whose nesting level exceeds the value provided
22436 in the rule parameter.
22438 The control structures checked are the following:
22441 @item @code{if} statement
22442 @item @code{case} statement
22443 @item @code{loop} statement
22444 @item Selective accept statement
22445 @item Timed entry call statement
22446 @item Conditional entry call
22447 @item Asynchronous select statement
22451 The rule has the following parameter for the @option{+R} option:
22455 Positive integer specifying the maximal control structure nesting
22456 level that is not flagged
22460 If the parameter for the @option{+R} option is not specified or
22461 if it is not a positive integer, @option{+R} option is ignored.
22463 If more then one option is specified for the gnatcheck call, the later option and
22464 new parameter override the previous one(s).
22467 @node Parameters_Out_Of_Order
22468 @subsection @code{Parameters_Out_Of_Order}
22469 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22472 Flag each subprogram and entry declaration whose formal parameters are not
22473 ordered according to the following scheme:
22477 @item @code{in} and @code{access} parameters first,
22478 then @code{in out} parameters,
22479 and then @code{out} parameters;
22481 @item for @code{in} mode, parameters with default initialization expressions
22486 Only the first violation of the described order is flagged.
22488 The following constructs are checked:
22491 @item subprogram declarations (including null procedures);
22492 @item generic subprogram declarations;
22493 @item formal subprogram declarations;
22494 @item entry declarations;
22495 @item subprogram bodies and subprogram body stubs that do not
22496 have separate specifications
22500 Subprogram renamings are not checked.
22502 This rule has no parameters.
22505 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22506 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22507 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22510 Flag each generic actual parameter corresponding to a generic formal
22511 parameter with a default initialization, if positional notation is used.
22513 This rule has no parameters.
22515 @node Positional_Actuals_For_Defaulted_Parameters
22516 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22517 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22520 Flag each actual parameter to a subprogram or entry call where the
22521 corresponding formal parameter has a default expression, if positional
22524 This rule has no parameters.
22526 @node Positional_Components
22527 @subsection @code{Positional_Components}
22528 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22531 Flag each array, record and extension aggregate that includes positional
22534 This rule has no parameters.
22537 @node Positional_Generic_Parameters
22538 @subsection @code{Positional_Generic_Parameters}
22539 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22542 Flag each positional actual generic parameter except for the case when
22543 the generic unit being iinstantiated has exactly one generic formal
22546 This rule has no parameters.
22549 @node Positional_Parameters
22550 @subsection @code{Positional_Parameters}
22551 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22554 Flag each positional parameter notation in a subprogram or entry call,
22555 except for the following:
22559 Parameters of calls to of prefix or infix operators are not flagged
22561 If the called subprogram or entry has only one formal parameter,
22562 the parameter of the call is not flagged;
22564 If a subprogram call uses the @emph{Object.Operation} notation, then
22567 the first parameter (that is, @emph{Object}) is not flagged;
22569 if the called subprogram has only two parameters, the second parameter
22570 of the call is not flagged;
22575 This rule has no parameters.
22580 @node Predefined_Numeric_Types
22581 @subsection @code{Predefined_Numeric_Types}
22582 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22585 Flag each explicit use of the name of any numeric type or subtype defined
22586 in package @code{Standard}.
22588 The rationale for this rule is to detect when the
22589 program may depend on platform-specific characteristics of the implementation
22590 of the predefined numeric types. Note that this rule is over-pessimistic;
22591 for example, a program that uses @code{String} indexing
22592 likely needs a variable of type @code{Integer}.
22593 Another example is the flagging of predefined numeric types with explicit
22596 @smallexample @c ada
22597 subtype My_Integer is Integer range Left .. Right;
22598 Vy_Var : My_Integer;
22602 This rule detects only numeric types and subtypes defined in
22603 @code{Standard}. The use of numeric types and subtypes defined in other
22604 predefined packages (such as @code{System.Any_Priority} or
22605 @code{Ada.Text_IO.Count}) is not flagged
22607 This rule has no parameters.
22611 @node Raising_External_Exceptions
22612 @subsection @code{Raising_External_Exceptions}
22613 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22616 Flag any @code{raise} statement, in a program unit declared in a library
22617 package or in a generic library package, for an exception that is
22618 neither a predefined exception nor an exception that is also declared (or
22619 renamed) in the visible part of the package.
22621 This rule has no parameters.
22625 @node Raising_Predefined_Exceptions
22626 @subsection @code{Raising_Predefined_Exceptions}
22627 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22630 Flag each @code{raise} statement that raises a predefined exception
22631 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22632 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22634 This rule has no parameters.
22636 @node Separate_Numeric_Error_Handlers
22637 @subsection @code{Separate_Numeric_Error_Handlers}
22638 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22641 Flags each exception handler that contains a choice for
22642 the predefined @code{Constraint_Error} exception, but does not contain
22643 the choice for the predefined @code{Numeric_Error} exception, or
22644 that contains the choice for @code{Numeric_Error}, but does not contain the
22645 choice for @code{Constraint_Error}.
22647 This rule has no parameters.
22651 @subsection @code{Recursion} (under construction, GLOBAL)
22652 @cindex @code{Recursion} rule (for @command{gnatcheck})
22655 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22656 calls, of recursive subprograms are detected.
22658 This rule has no parameters.
22662 @node Side_Effect_Functions
22663 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22664 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22667 Flag functions with side effects.
22669 We define a side effect as changing any data object that is not local for the
22670 body of this function.
22672 At the moment, we do NOT consider a side effect any input-output operations
22673 (changing a state or a content of any file).
22675 We do not consider protected functions for this rule (???)
22677 There are the following sources of side effect:
22680 @item Explicit (or direct) side-effect:
22684 direct assignment to a non-local variable;
22687 direct call to an entity that is known to change some data object that is
22688 not local for the body of this function (Note, that if F1 calls F2 and F2
22689 does have a side effect, this does not automatically mean that F1 also
22690 have a side effect, because it may be the case that F2 is declared in
22691 F1's body and it changes some data object that is global for F2, but
22695 @item Indirect side-effect:
22698 Subprogram calls implicitly issued by:
22701 computing initialization expressions from type declarations as a part
22702 of object elaboration or allocator evaluation;
22704 computing implicit parameters of subprogram or entry calls or generic
22709 activation of a task that change some non-local data object (directly or
22713 elaboration code of a package that is a result of a package instantiation;
22716 controlled objects;
22719 @item Situations when we can suspect a side-effect, but the full static check
22720 is either impossible or too hard:
22723 assignment to access variables or to the objects pointed by access
22727 call to a subprogram pointed by access-to-subprogram value
22735 This rule has no parameters.
22739 @subsection @code{Slices}
22740 @cindex @code{Slices} rule (for @command{gnatcheck})
22743 Flag all uses of array slicing
22745 This rule has no parameters.
22748 @node Too_Many_Parents
22749 @subsection @code{Too_Many_Parents}
22750 @cindex @code{Too_Many_Parents} rule (for @command{gnatcheck})
22753 Flags any type declaration, single task declaration or single protected
22754 declaration that has more then @option{N} parents, @option{N} is a parameter
22756 A parent here is either a (sub)type denoted by the subtype mark from the
22757 parent_subtype_indication (in case of a derived type declaration), or
22758 any of the progenitors from the interface list, if any.
22760 This rule has the following (mandatory) parameters for the @option{+R} option:
22764 Positive integer specifying the maximal allowed number of parents.
22768 @node Unassigned_OUT_Parameters
22769 @subsection @code{Unassigned_OUT_Parameters}
22770 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22773 Flags procedures' @code{out} parameters that are not assigned, and
22774 identifies the contexts in which the assignments are missing.
22776 An @code{out} parameter is flagged in the statements in the procedure
22777 body's handled sequence of statements (before the procedure body's
22778 @code{exception} part, if any) if this sequence of statements contains
22779 no assignments to the parameter.
22781 An @code{out} parameter is flagged in an exception handler in the exception
22782 part of the procedure body's handled sequence of statements if the handler
22783 contains no assignment to the parameter.
22785 Bodies of generic procedures are also considered.
22787 The following are treated as assignments to an @code{out} parameter:
22791 an assignment statement, with the parameter or some component as the target;
22794 passing the parameter (or one of its components) as an @code{out} or
22795 @code{in out} parameter.
22799 This rule does not have any parameters.
22803 @node Uncommented_BEGIN_In_Package_Bodies
22804 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22805 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22808 Flags each package body with declarations and a statement part that does not
22809 include a trailing comment on the line containing the @code{begin} keyword;
22810 this trailing comment needs to specify the package name and nothing else.
22811 The @code{begin} is not flagged if the package body does not
22812 contain any declarations.
22814 If the @code{begin} keyword is placed on the
22815 same line as the last declaration or the first statement, it is flagged
22816 independently of whether the line contains a trailing comment. The
22817 diagnostic message is attached to the line containing the first statement.
22819 This rule has no parameters.
22821 @node Unconditional_Exits
22822 @subsection @code{Unconditional_Exits}
22823 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22826 Flag unconditional @code{exit} statements.
22828 This rule has no parameters.
22830 @node Unconstrained_Array_Returns
22831 @subsection @code{Unconstrained_Array_Returns}
22832 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22835 Flag each function returning an unconstrained array. Function declarations,
22836 function bodies (and body stubs) having no separate specifications,
22837 and generic function instantiations are checked.
22838 Function calls and function renamings are
22841 Generic function declarations, and function declarations in generic
22842 packages are not checked, instead this rule checks the results of
22843 generic instantiations (that is, expanded specification and expanded
22844 body corresponding to an instantiation).
22846 This rule has no parameters.
22848 @node Universal_Ranges
22849 @subsection @code{Universal_Ranges}
22850 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22853 Flag discrete ranges that are a part of an index constraint, constrained
22854 array definition, or @code{for}-loop parameter specification, and whose bounds
22855 are both of type @i{universal_integer}. Ranges that have at least one
22856 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22857 or an expression of non-universal type) are not flagged.
22859 This rule has no parameters.
22862 @node Unnamed_Blocks_And_Loops
22863 @subsection @code{Unnamed_Blocks_And_Loops}
22864 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22867 Flag each unnamed block statement and loop statement.
22869 The rule has no parameters.
22874 @node Unused_Subprograms
22875 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22876 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22879 Flag all unused subprograms.
22881 This rule has no parameters.
22887 @node USE_PACKAGE_Clauses
22888 @subsection @code{USE_PACKAGE_Clauses}
22889 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22892 Flag all @code{use} clauses for packages; @code{use type} clauses are
22895 This rule has no parameters.
22898 @node Visible_Components
22899 @subsection @code{Visible_Components}
22900 @cindex @code{Visible_Components} rule (for @command{gnatcheck})
22903 Flags all the type declarations located in the visible part of a library
22904 package or a library generic package that can declare a visible component. A
22905 type is considered as declaring a visible component if it contains a record
22906 definition by its own or as a part of a record extension. Type declaration is
22907 flagged even if it contains a record definition that defines no components.
22909 Declarations located in private parts of local (generic) packages are not
22910 flagged. Declarations in private packages are not flagged.
22912 This rule has no parameters.
22915 @node Volatile_Objects_Without_Address_Clauses
22916 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22917 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22920 Flag each volatile object that does not have an address clause.
22922 The following check is made: if the pragma @code{Volatile} is applied to a
22923 data object or to its type, then an address clause must
22924 be supplied for this object.
22926 This rule does not check the components of data objects,
22927 array components that are volatile as a result of the pragma
22928 @code{Volatile_Components}, or objects that are volatile because
22929 they are atomic as a result of pragmas @code{Atomic} or
22930 @code{Atomic_Components}.
22932 Only variable declarations, and not constant declarations, are checked.
22934 This rule has no parameters.
22937 @c *********************************
22938 @node Creating Sample Bodies Using gnatstub
22939 @chapter Creating Sample Bodies Using @command{gnatstub}
22943 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22944 for library unit declarations.
22946 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22947 driver (see @ref{The GNAT Driver and Project Files}).
22949 To create a body stub, @command{gnatstub} has to compile the library
22950 unit declaration. Therefore, bodies can be created only for legal
22951 library units. Moreover, if a library unit depends semantically upon
22952 units located outside the current directory, you have to provide
22953 the source search path when calling @command{gnatstub}, see the description
22954 of @command{gnatstub} switches below.
22956 By default, all the program unit body stubs generated by @code{gnatstub}
22957 raise the predefined @code{Program_Error} exception, which will catch
22958 accidental calls of generated stubs. This behavior can be changed with
22959 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22962 * Running gnatstub::
22963 * Switches for gnatstub::
22966 @node Running gnatstub
22967 @section Running @command{gnatstub}
22970 @command{gnatstub} has the command-line interface of the form
22973 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22980 is the name of the source file that contains a library unit declaration
22981 for which a body must be created. The file name may contain the path
22983 The file name does not have to follow the GNAT file name conventions. If the
22985 does not follow GNAT file naming conventions, the name of the body file must
22987 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22988 If the file name follows the GNAT file naming
22989 conventions and the name of the body file is not provided,
22992 of the body file from the argument file name by replacing the @file{.ads}
22994 with the @file{.adb} suffix.
22997 indicates the directory in which the body stub is to be placed (the default
23002 is an optional sequence of switches as described in the next section
23005 @node Switches for gnatstub
23006 @section Switches for @command{gnatstub}
23012 @cindex @option{^-f^/FULL^} (@command{gnatstub})
23013 If the destination directory already contains a file with the name of the
23015 for the argument spec file, replace it with the generated body stub.
23017 @item ^-hs^/HEADER=SPEC^
23018 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
23019 Put the comment header (i.e., all the comments preceding the
23020 compilation unit) from the source of the library unit declaration
23021 into the body stub.
23023 @item ^-hg^/HEADER=GENERAL^
23024 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
23025 Put a sample comment header into the body stub.
23027 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
23028 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
23029 Use the content of the file as the comment header for a generated body stub.
23033 @cindex @option{-IDIR} (@command{gnatstub})
23035 @cindex @option{-I-} (@command{gnatstub})
23038 @item /NOCURRENT_DIRECTORY
23039 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
23041 ^These switches have ^This switch has^ the same meaning as in calls to
23043 ^They define ^It defines ^ the source search path in the call to
23044 @command{gcc} issued
23045 by @command{gnatstub} to compile an argument source file.
23047 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
23048 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
23049 This switch has the same meaning as in calls to @command{gcc}.
23050 It defines the additional configuration file to be passed to the call to
23051 @command{gcc} issued
23052 by @command{gnatstub} to compile an argument source file.
23054 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
23055 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
23056 (@var{n} is a non-negative integer). Set the maximum line length in the
23057 body stub to @var{n}; the default is 79. The maximum value that can be
23058 specified is 32767. Note that in the special case of configuration
23059 pragma files, the maximum is always 32767 regardless of whether or
23060 not this switch appears.
23062 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
23063 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
23064 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
23065 the generated body sample to @var{n}.
23066 The default indentation is 3.
23068 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
23069 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
23070 Order local bodies alphabetically. (By default local bodies are ordered
23071 in the same way as the corresponding local specs in the argument spec file.)
23073 @item ^-i^/INDENTATION=^@var{n}
23074 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
23075 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
23077 @item ^-k^/TREE_FILE=SAVE^
23078 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
23079 Do not remove the tree file (i.e., the snapshot of the compiler internal
23080 structures used by @command{gnatstub}) after creating the body stub.
23082 @item ^-l^/LINE_LENGTH=^@var{n}
23083 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
23084 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
23086 @item ^--no-exception^/NO_EXCEPTION^
23087 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
23088 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
23089 This is not always possible for function stubs.
23091 @item ^--no-local-header^/NO_LOCAL_HEADER^
23092 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
23093 Do not place local comment header with unit name before body stub for a
23096 @item ^-o ^/BODY=^@var{body-name}
23097 @cindex @option{^-o^/BODY^} (@command{gnatstub})
23098 Body file name. This should be set if the argument file name does not
23100 the GNAT file naming
23101 conventions. If this switch is omitted the default name for the body will be
23103 from the argument file name according to the GNAT file naming conventions.
23106 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
23107 Quiet mode: do not generate a confirmation when a body is
23108 successfully created, and do not generate a message when a body is not
23112 @item ^-r^/TREE_FILE=REUSE^
23113 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
23114 Reuse the tree file (if it exists) instead of creating it. Instead of
23115 creating the tree file for the library unit declaration, @command{gnatstub}
23116 tries to find it in the current directory and use it for creating
23117 a body. If the tree file is not found, no body is created. This option
23118 also implies @option{^-k^/SAVE^}, whether or not
23119 the latter is set explicitly.
23121 @item ^-t^/TREE_FILE=OVERWRITE^
23122 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
23123 Overwrite the existing tree file. If the current directory already
23124 contains the file which, according to the GNAT file naming rules should
23125 be considered as a tree file for the argument source file,
23127 will refuse to create the tree file needed to create a sample body
23128 unless this option is set.
23130 @item ^-v^/VERBOSE^
23131 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
23132 Verbose mode: generate version information.
23136 @c *********************************
23137 @node Generating Ada Bindings for C and C++ headers
23138 @chapter Generating Ada Bindings for C and C++ headers
23142 GNAT now comes with a new experimental binding generator for C and C++
23143 headers which is intended to do 95% of the tedious work of generating
23144 Ada specs from C or C++ header files. Note that this still is a work in
23145 progress, not designed to generate 100% correct Ada specs.
23147 The code generated is using the Ada 2005 syntax, which makes it
23148 easier to interface with other languages than previous versions of Ada.
23151 * Running the binding generator::
23152 * Generating bindings for C++ headers::
23156 @node Running the binding generator
23157 @section Running the binding generator
23160 The binding generator is part of the @command{gcc} compiler and can be
23161 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
23162 spec files for the header files specified on the command line, and all
23163 header files needed by these files transitivitely. For example:
23166 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
23167 $ gcc -c -gnat05 *.ads
23170 will generate, under GNU/Linux, the following files: @file{time_h.ads},
23171 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
23172 correspond to the files @file{/usr/include/time.h},
23173 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
23174 mode these Ada specs.
23176 The @code{-C} switch tells @command{gcc} to extract comments from headers,
23177 and will attempt to generate corresponding Ada comments.
23179 If you want to generate a single Ada file and not the transitive closure, you
23180 can use instead the @option{-fdump-ada-spec-slim} switch.
23182 Note that we recommend when possible to use the @command{g++} driver to
23183 generate bindings, even for most C headers, since this will in general
23184 generate better Ada specs. For generating bindings for C++ headers, it is
23185 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
23186 is equivalent in this case. If @command{g++} cannot work on your C headers
23187 because of incompatibilities between C and C++, then you can fallback to
23188 @command{gcc} instead.
23190 For an example of better bindings generated from the C++ front-end,
23191 the name of the parameters (when available) are actually ignored by the C
23192 front-end. Consider the following C header:
23195 extern void foo (int variable);
23198 with the C front-end, @code{variable} is ignored, and the above is handled as:
23201 extern void foo (int);
23204 generating a generic:
23207 procedure foo (param1 : int);
23210 with the C++ front-end, the name is available, and we generate:
23213 procedure foo (variable : int);
23216 In some cases, the generated bindings will be more complete or more meaningful
23217 when defining some macros, which you can do via the @option{-D} switch. This
23218 is for example the case with @file{Xlib.h} under GNU/Linux:
23221 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
23224 The above will generate more complete bindings than a straight call without
23225 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
23227 In other cases, it is not possible to parse a header file in a stand alone
23228 manner, because other include files need to be included first. In this
23229 case, the solution is to create a small header file including the needed
23230 @code{#include} and possible @code{#define} directives. For example, to
23231 generate Ada bindings for @file{readline/readline.h}, you need to first
23232 include @file{stdio.h}, so you can create a file with the following two
23233 lines in e.g. @file{readline1.h}:
23237 #include <readline/readline.h>
23240 and then generate Ada bindings from this file:
23243 $ g++ -c -fdump-ada-spec readline1.h
23246 @node Generating bindings for C++ headers
23247 @section Generating bindings for C++ headers
23250 Generating bindings for C++ headers is done using the same options, always
23251 with the @command{g++} compiler.
23253 In this mode, C++ classes will be mapped to Ada tagged types, constructors
23254 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
23255 multiple inheritance of abstract classes will be mapped to Ada interfaces
23256 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
23257 information on interfacing to C++).
23259 For example, given the following C++ header file:
23266 virtual int Number_Of_Teeth () = 0;
23271 virtual void Set_Owner (char* Name) = 0;
23277 virtual void Set_Age (int New_Age);
23280 class Dog : Animal, Carnivore, Domestic @{
23285 virtual int Number_Of_Teeth ();
23286 virtual void Set_Owner (char* Name);
23294 The corresponding Ada code is generated:
23296 @smallexample @c ada
23299 package Class_Carnivore is
23300 type Carnivore is limited interface;
23301 pragma Import (CPP, Carnivore);
23303 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
23305 use Class_Carnivore;
23307 package Class_Domestic is
23308 type Domestic is limited interface;
23309 pragma Import (CPP, Domestic);
23311 procedure Set_Owner
23312 (this : access Domestic;
23313 Name : Interfaces.C.Strings.chars_ptr) is abstract;
23315 use Class_Domestic;
23317 package Class_Animal is
23318 type Animal is tagged limited record
23319 Age_Count : aliased int;
23321 pragma Import (CPP, Animal);
23323 procedure Set_Age (this : access Animal; New_Age : int);
23324 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
23328 package Class_Dog is
23329 type Dog is new Animal and Carnivore and Domestic with record
23330 Tooth_Count : aliased int;
23331 Owner : Interfaces.C.Strings.chars_ptr;
23333 pragma Import (CPP, Dog);
23335 function Number_Of_Teeth (this : access Dog) return int;
23336 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
23338 procedure Set_Owner
23339 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
23340 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
23342 function New_Dog return Dog;
23343 pragma CPP_Constructor (New_Dog);
23344 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
23355 @item -fdump-ada-spec
23356 @cindex @option{-fdump-ada-spec} (@command{gcc})
23357 Generate Ada spec files for the given header files transitively (including
23358 all header files that these headers depend upon).
23360 @item -fdump-ada-spec-slim
23361 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
23362 Generate Ada spec files for the header files specified on the command line
23366 @cindex @option{-C} (@command{gcc})
23367 Extract comments from headers and generate Ada comments in the Ada spec files.
23370 @node Other Utility Programs
23371 @chapter Other Utility Programs
23374 This chapter discusses some other utility programs available in the Ada
23378 * Using Other Utility Programs with GNAT::
23379 * The External Symbol Naming Scheme of GNAT::
23380 * Converting Ada Files to html with gnathtml::
23381 * Installing gnathtml::
23388 @node Using Other Utility Programs with GNAT
23389 @section Using Other Utility Programs with GNAT
23392 The object files generated by GNAT are in standard system format and in
23393 particular the debugging information uses this format. This means
23394 programs generated by GNAT can be used with existing utilities that
23395 depend on these formats.
23398 In general, any utility program that works with C will also often work with
23399 Ada programs generated by GNAT. This includes software utilities such as
23400 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
23404 @node The External Symbol Naming Scheme of GNAT
23405 @section The External Symbol Naming Scheme of GNAT
23408 In order to interpret the output from GNAT, when using tools that are
23409 originally intended for use with other languages, it is useful to
23410 understand the conventions used to generate link names from the Ada
23413 All link names are in all lowercase letters. With the exception of library
23414 procedure names, the mechanism used is simply to use the full expanded
23415 Ada name with dots replaced by double underscores. For example, suppose
23416 we have the following package spec:
23418 @smallexample @c ada
23429 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
23430 the corresponding link name is @code{qrs__mn}.
23432 Of course if a @code{pragma Export} is used this may be overridden:
23434 @smallexample @c ada
23439 pragma Export (Var1, C, External_Name => "var1_name");
23441 pragma Export (Var2, C, Link_Name => "var2_link_name");
23448 In this case, the link name for @var{Var1} is whatever link name the
23449 C compiler would assign for the C function @var{var1_name}. This typically
23450 would be either @var{var1_name} or @var{_var1_name}, depending on operating
23451 system conventions, but other possibilities exist. The link name for
23452 @var{Var2} is @var{var2_link_name}, and this is not operating system
23456 One exception occurs for library level procedures. A potential ambiguity
23457 arises between the required name @code{_main} for the C main program,
23458 and the name we would otherwise assign to an Ada library level procedure
23459 called @code{Main} (which might well not be the main program).
23461 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
23462 names. So if we have a library level procedure such as
23464 @smallexample @c ada
23467 procedure Hello (S : String);
23473 the external name of this procedure will be @var{_ada_hello}.
23476 @node Converting Ada Files to html with gnathtml
23477 @section Converting Ada Files to HTML with @code{gnathtml}
23480 This @code{Perl} script allows Ada source files to be browsed using
23481 standard Web browsers. For installation procedure, see the section
23482 @xref{Installing gnathtml}.
23484 Ada reserved keywords are highlighted in a bold font and Ada comments in
23485 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
23486 switch to suppress the generation of cross-referencing information, user
23487 defined variables and types will appear in a different color; you will
23488 be able to click on any identifier and go to its declaration.
23490 The command line is as follow:
23492 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
23496 You can pass it as many Ada files as you want. @code{gnathtml} will generate
23497 an html file for every ada file, and a global file called @file{index.htm}.
23498 This file is an index of every identifier defined in the files.
23500 The available ^switches^options^ are the following ones:
23504 @cindex @option{-83} (@code{gnathtml})
23505 Only the Ada 83 subset of keywords will be highlighted.
23507 @item -cc @var{color}
23508 @cindex @option{-cc} (@code{gnathtml})
23509 This option allows you to change the color used for comments. The default
23510 value is green. The color argument can be any name accepted by html.
23513 @cindex @option{-d} (@code{gnathtml})
23514 If the Ada files depend on some other files (for instance through
23515 @code{with} clauses, the latter files will also be converted to html.
23516 Only the files in the user project will be converted to html, not the files
23517 in the run-time library itself.
23520 @cindex @option{-D} (@code{gnathtml})
23521 This command is the same as @option{-d} above, but @command{gnathtml} will
23522 also look for files in the run-time library, and generate html files for them.
23524 @item -ext @var{extension}
23525 @cindex @option{-ext} (@code{gnathtml})
23526 This option allows you to change the extension of the generated HTML files.
23527 If you do not specify an extension, it will default to @file{htm}.
23530 @cindex @option{-f} (@code{gnathtml})
23531 By default, gnathtml will generate html links only for global entities
23532 ('with'ed units, global variables and types,@dots{}). If you specify
23533 @option{-f} on the command line, then links will be generated for local
23536 @item -l @var{number}
23537 @cindex @option{-l} (@code{gnathtml})
23538 If this ^switch^option^ is provided and @var{number} is not 0, then
23539 @code{gnathtml} will number the html files every @var{number} line.
23542 @cindex @option{-I} (@code{gnathtml})
23543 Specify a directory to search for library files (@file{.ALI} files) and
23544 source files. You can provide several -I switches on the command line,
23545 and the directories will be parsed in the order of the command line.
23548 @cindex @option{-o} (@code{gnathtml})
23549 Specify the output directory for html files. By default, gnathtml will
23550 saved the generated html files in a subdirectory named @file{html/}.
23552 @item -p @var{file}
23553 @cindex @option{-p} (@code{gnathtml})
23554 If you are using Emacs and the most recent Emacs Ada mode, which provides
23555 a full Integrated Development Environment for compiling, checking,
23556 running and debugging applications, you may use @file{.gpr} files
23557 to give the directories where Emacs can find sources and object files.
23559 Using this ^switch^option^, you can tell gnathtml to use these files.
23560 This allows you to get an html version of your application, even if it
23561 is spread over multiple directories.
23563 @item -sc @var{color}
23564 @cindex @option{-sc} (@code{gnathtml})
23565 This ^switch^option^ allows you to change the color used for symbol
23567 The default value is red. The color argument can be any name accepted by html.
23569 @item -t @var{file}
23570 @cindex @option{-t} (@code{gnathtml})
23571 This ^switch^option^ provides the name of a file. This file contains a list of
23572 file names to be converted, and the effect is exactly as though they had
23573 appeared explicitly on the command line. This
23574 is the recommended way to work around the command line length limit on some
23579 @node Installing gnathtml
23580 @section Installing @code{gnathtml}
23583 @code{Perl} needs to be installed on your machine to run this script.
23584 @code{Perl} is freely available for almost every architecture and
23585 Operating System via the Internet.
23587 On Unix systems, you may want to modify the first line of the script
23588 @code{gnathtml}, to explicitly tell the Operating system where Perl
23589 is. The syntax of this line is:
23591 #!full_path_name_to_perl
23595 Alternatively, you may run the script using the following command line:
23598 $ perl gnathtml.pl @ovar{switches} @var{files}
23607 The GNAT distribution provides an Ada 95 template for the HP Language
23608 Sensitive Editor (LSE), a component of DECset. In order to
23609 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23616 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23617 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23618 the collection phase with the /DEBUG qualifier.
23621 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23622 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23623 $ RUN/DEBUG <PROGRAM_NAME>
23629 @c ******************************
23630 @node Code Coverage and Profiling
23631 @chapter Code Coverage and Profiling
23632 @cindex Code Coverage
23636 This chapter describes how to use @code{gcov} - coverage testing tool - and
23637 @code{gprof} - profiler tool - on your Ada programs.
23640 * Code Coverage of Ada Programs using gcov::
23641 * Profiling an Ada Program using gprof::
23644 @node Code Coverage of Ada Programs using gcov
23645 @section Code Coverage of Ada Programs using gcov
23647 @cindex -fprofile-arcs
23648 @cindex -ftest-coverage
23650 @cindex Code Coverage
23653 @code{gcov} is a test coverage program: it analyzes the execution of a given
23654 program on selected tests, to help you determine the portions of the program
23655 that are still untested.
23657 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23658 User's Guide. You can refer to this documentation for a more complete
23661 This chapter provides a quick startup guide, and
23662 details some Gnat-specific features.
23665 * Quick startup guide::
23669 @node Quick startup guide
23670 @subsection Quick startup guide
23672 In order to perform coverage analysis of a program using @code{gcov}, 3
23677 Code instrumentation during the compilation process
23679 Execution of the instrumented program
23681 Execution of the @code{gcov} tool to generate the result.
23684 The code instrumentation needed by gcov is created at the object level:
23685 The source code is not modified in any way, because the instrumentation code is
23686 inserted by gcc during the compilation process. To compile your code with code
23687 coverage activated, you need to recompile your whole project using the
23689 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23690 @code{-fprofile-arcs}.
23693 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23694 -largs -fprofile-arcs
23697 This compilation process will create @file{.gcno} files together with
23698 the usual object files.
23700 Once the program is compiled with coverage instrumentation, you can
23701 run it as many times as needed - on portions of a test suite for
23702 example. The first execution will produce @file{.gcda} files at the
23703 same location as the @file{.gcno} files. The following executions
23704 will update those files, so that a cumulative result of the covered
23705 portions of the program is generated.
23707 Finally, you need to call the @code{gcov} tool. The different options of
23708 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23710 This will create annotated source files with a @file{.gcov} extension:
23711 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23713 @node Gnat specifics
23714 @subsection Gnat specifics
23716 Because Ada semantics, portions of the source code may be shared among
23717 several object files. This is the case for example when generics are
23718 involved, when inlining is active or when declarations generate initialisation
23719 calls. In order to take
23720 into account this shared code, you need to call @code{gcov} on all
23721 source files of the tested program at once.
23723 The list of source files might exceed the system's maximum command line
23724 length. In order to bypass this limitation, a new mechanism has been
23725 implemented in @code{gcov}: you can now list all your project's files into a
23726 text file, and provide this file to gcov as a parameter, preceded by a @@
23727 (e.g. @samp{gcov @@mysrclist.txt}).
23729 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23730 not supported as there can be unresolved symbols during the final link.
23732 @node Profiling an Ada Program using gprof
23733 @section Profiling an Ada Program using gprof
23739 This section is not meant to be an exhaustive documentation of @code{gprof}.
23740 Full documentation for it can be found in the GNU Profiler User's Guide
23741 documentation that is part of this GNAT distribution.
23743 Profiling a program helps determine the parts of a program that are executed
23744 most often, and are therefore the most time-consuming.
23746 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23747 better handle Ada programs and multitasking.
23748 It is currently supported on the following platforms
23753 solaris sparc/sparc64/x86
23759 In order to profile a program using @code{gprof}, 3 steps are needed:
23763 Code instrumentation, requiring a full recompilation of the project with the
23766 Execution of the program under the analysis conditions, i.e. with the desired
23769 Analysis of the results using the @code{gprof} tool.
23773 The following sections detail the different steps, and indicate how
23774 to interpret the results:
23776 * Compilation for profiling::
23777 * Program execution::
23779 * Interpretation of profiling results::
23782 @node Compilation for profiling
23783 @subsection Compilation for profiling
23787 In order to profile a program the first step is to tell the compiler
23788 to generate the necessary profiling information. The compiler switch to be used
23789 is @code{-pg}, which must be added to other compilation switches. This
23790 switch needs to be specified both during compilation and link stages, and can
23791 be specified once when using gnatmake:
23794 gnatmake -f -pg -P my_project
23798 Note that only the objects that were compiled with the @samp{-pg} switch will be
23799 profiled; if you need to profile your whole project, use the
23800 @samp{-f} gnatmake switch to force full recompilation.
23802 @node Program execution
23803 @subsection Program execution
23806 Once the program has been compiled for profiling, you can run it as usual.
23808 The only constraint imposed by profiling is that the program must terminate
23809 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23812 Once the program completes execution, a data file called @file{gmon.out} is
23813 generated in the directory where the program was launched from. If this file
23814 already exists, it will be overwritten.
23816 @node Running gprof
23817 @subsection Running gprof
23820 The @code{gprof} tool is called as follow:
23823 gprof my_prog gmon.out
23834 The complete form of the gprof command line is the following:
23837 gprof [^switches^options^] [executable [data-file]]
23841 @code{gprof} supports numerous ^switch^options^. The order of these
23842 ^switch^options^ does not matter. The full list of options can be found in
23843 the GNU Profiler User's Guide documentation that comes with this documentation.
23845 The following is the subset of those switches that is most relevant:
23849 @item --demangle[=@var{style}]
23850 @itemx --no-demangle
23851 @cindex @option{--demangle} (@code{gprof})
23852 These options control whether symbol names should be demangled when
23853 printing output. The default is to demangle C++ symbols. The
23854 @code{--no-demangle} option may be used to turn off demangling. Different
23855 compilers have different mangling styles. The optional demangling style
23856 argument can be used to choose an appropriate demangling style for your
23857 compiler, in particular Ada symbols generated by GNAT can be demangled using
23858 @code{--demangle=gnat}.
23860 @item -e @var{function_name}
23861 @cindex @option{-e} (@code{gprof})
23862 The @samp{-e @var{function}} option tells @code{gprof} not to print
23863 information about the function @var{function_name} (and its
23864 children@dots{}) in the call graph. The function will still be listed
23865 as a child of any functions that call it, but its index number will be
23866 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23867 given; only one @var{function_name} may be indicated with each @samp{-e}
23870 @item -E @var{function_name}
23871 @cindex @option{-E} (@code{gprof})
23872 The @code{-E @var{function}} option works like the @code{-e} option, but
23873 execution time spent in the function (and children who were not called from
23874 anywhere else), will not be used to compute the percentages-of-time for
23875 the call graph. More than one @samp{-E} option may be given; only one
23876 @var{function_name} may be indicated with each @samp{-E} option.
23878 @item -f @var{function_name}
23879 @cindex @option{-f} (@code{gprof})
23880 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23881 call graph to the function @var{function_name} and its children (and
23882 their children@dots{}). More than one @samp{-f} option may be given;
23883 only one @var{function_name} may be indicated with each @samp{-f}
23886 @item -F @var{function_name}
23887 @cindex @option{-F} (@code{gprof})
23888 The @samp{-F @var{function}} option works like the @code{-f} option, but
23889 only time spent in the function and its children (and their
23890 children@dots{}) will be used to determine total-time and
23891 percentages-of-time for the call graph. More than one @samp{-F} option
23892 may be given; only one @var{function_name} may be indicated with each
23893 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23897 @node Interpretation of profiling results
23898 @subsection Interpretation of profiling results
23902 The results of the profiling analysis are represented by two arrays: the
23903 'flat profile' and the 'call graph'. Full documentation of those outputs
23904 can be found in the GNU Profiler User's Guide.
23906 The flat profile shows the time spent in each function of the program, and how
23907 many time it has been called. This allows you to locate easily the most
23908 time-consuming functions.
23910 The call graph shows, for each subprogram, the subprograms that call it,
23911 and the subprograms that it calls. It also provides an estimate of the time
23912 spent in each of those callers/called subprograms.
23915 @c ******************************
23916 @node Running and Debugging Ada Programs
23917 @chapter Running and Debugging Ada Programs
23921 This chapter discusses how to debug Ada programs.
23923 It applies to GNAT on the Alpha OpenVMS platform;
23924 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23925 since HP has implemented Ada support in the OpenVMS debugger on I64.
23928 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23932 The illegality may be a violation of the static semantics of Ada. In
23933 that case GNAT diagnoses the constructs in the program that are illegal.
23934 It is then a straightforward matter for the user to modify those parts of
23938 The illegality may be a violation of the dynamic semantics of Ada. In
23939 that case the program compiles and executes, but may generate incorrect
23940 results, or may terminate abnormally with some exception.
23943 When presented with a program that contains convoluted errors, GNAT
23944 itself may terminate abnormally without providing full diagnostics on
23945 the incorrect user program.
23949 * The GNAT Debugger GDB::
23951 * Introduction to GDB Commands::
23952 * Using Ada Expressions::
23953 * Calling User-Defined Subprograms::
23954 * Using the Next Command in a Function::
23957 * Debugging Generic Units::
23958 * GNAT Abnormal Termination or Failure to Terminate::
23959 * Naming Conventions for GNAT Source Files::
23960 * Getting Internal Debugging Information::
23961 * Stack Traceback::
23967 @node The GNAT Debugger GDB
23968 @section The GNAT Debugger GDB
23971 @code{GDB} is a general purpose, platform-independent debugger that
23972 can be used to debug mixed-language programs compiled with @command{gcc},
23973 and in particular is capable of debugging Ada programs compiled with
23974 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23975 complex Ada data structures.
23977 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23979 located in the GNU:[DOCS] directory,
23981 for full details on the usage of @code{GDB}, including a section on
23982 its usage on programs. This manual should be consulted for full
23983 details. The section that follows is a brief introduction to the
23984 philosophy and use of @code{GDB}.
23986 When GNAT programs are compiled, the compiler optionally writes debugging
23987 information into the generated object file, including information on
23988 line numbers, and on declared types and variables. This information is
23989 separate from the generated code. It makes the object files considerably
23990 larger, but it does not add to the size of the actual executable that
23991 will be loaded into memory, and has no impact on run-time performance. The
23992 generation of debug information is triggered by the use of the
23993 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23994 used to carry out the compilations. It is important to emphasize that
23995 the use of these options does not change the generated code.
23997 The debugging information is written in standard system formats that
23998 are used by many tools, including debuggers and profilers. The format
23999 of the information is typically designed to describe C types and
24000 semantics, but GNAT implements a translation scheme which allows full
24001 details about Ada types and variables to be encoded into these
24002 standard C formats. Details of this encoding scheme may be found in
24003 the file exp_dbug.ads in the GNAT source distribution. However, the
24004 details of this encoding are, in general, of no interest to a user,
24005 since @code{GDB} automatically performs the necessary decoding.
24007 When a program is bound and linked, the debugging information is
24008 collected from the object files, and stored in the executable image of
24009 the program. Again, this process significantly increases the size of
24010 the generated executable file, but it does not increase the size of
24011 the executable program itself. Furthermore, if this program is run in
24012 the normal manner, it runs exactly as if the debug information were
24013 not present, and takes no more actual memory.
24015 However, if the program is run under control of @code{GDB}, the
24016 debugger is activated. The image of the program is loaded, at which
24017 point it is ready to run. If a run command is given, then the program
24018 will run exactly as it would have if @code{GDB} were not present. This
24019 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
24020 entirely non-intrusive until a breakpoint is encountered. If no
24021 breakpoint is ever hit, the program will run exactly as it would if no
24022 debugger were present. When a breakpoint is hit, @code{GDB} accesses
24023 the debugging information and can respond to user commands to inspect
24024 variables, and more generally to report on the state of execution.
24028 @section Running GDB
24031 This section describes how to initiate the debugger.
24032 @c The above sentence is really just filler, but it was otherwise
24033 @c clumsy to get the first paragraph nonindented given the conditional
24034 @c nature of the description
24037 The debugger can be launched from a @code{GPS} menu or
24038 directly from the command line. The description below covers the latter use.
24039 All the commands shown can be used in the @code{GPS} debug console window,
24040 but there are usually more GUI-based ways to achieve the same effect.
24043 The command to run @code{GDB} is
24046 $ ^gdb program^GDB PROGRAM^
24050 where @code{^program^PROGRAM^} is the name of the executable file. This
24051 activates the debugger and results in a prompt for debugger commands.
24052 The simplest command is simply @code{run}, which causes the program to run
24053 exactly as if the debugger were not present. The following section
24054 describes some of the additional commands that can be given to @code{GDB}.
24056 @c *******************************
24057 @node Introduction to GDB Commands
24058 @section Introduction to GDB Commands
24061 @code{GDB} contains a large repertoire of commands. @xref{Top,,
24062 Debugging with GDB, gdb, Debugging with GDB},
24064 located in the GNU:[DOCS] directory,
24066 for extensive documentation on the use
24067 of these commands, together with examples of their use. Furthermore,
24068 the command @command{help} invoked from within GDB activates a simple help
24069 facility which summarizes the available commands and their options.
24070 In this section we summarize a few of the most commonly
24071 used commands to give an idea of what @code{GDB} is about. You should create
24072 a simple program with debugging information and experiment with the use of
24073 these @code{GDB} commands on the program as you read through the
24077 @item set args @var{arguments}
24078 The @var{arguments} list above is a list of arguments to be passed to
24079 the program on a subsequent run command, just as though the arguments
24080 had been entered on a normal invocation of the program. The @code{set args}
24081 command is not needed if the program does not require arguments.
24084 The @code{run} command causes execution of the program to start from
24085 the beginning. If the program is already running, that is to say if
24086 you are currently positioned at a breakpoint, then a prompt will ask
24087 for confirmation that you want to abandon the current execution and
24090 @item breakpoint @var{location}
24091 The breakpoint command sets a breakpoint, that is to say a point at which
24092 execution will halt and @code{GDB} will await further
24093 commands. @var{location} is
24094 either a line number within a file, given in the format @code{file:linenumber},
24095 or it is the name of a subprogram. If you request that a breakpoint be set on
24096 a subprogram that is overloaded, a prompt will ask you to specify on which of
24097 those subprograms you want to breakpoint. You can also
24098 specify that all of them should be breakpointed. If the program is run
24099 and execution encounters the breakpoint, then the program
24100 stops and @code{GDB} signals that the breakpoint was encountered by
24101 printing the line of code before which the program is halted.
24103 @item breakpoint exception @var{name}
24104 A special form of the breakpoint command which breakpoints whenever
24105 exception @var{name} is raised.
24106 If @var{name} is omitted,
24107 then a breakpoint will occur when any exception is raised.
24109 @item print @var{expression}
24110 This will print the value of the given expression. Most simple
24111 Ada expression formats are properly handled by @code{GDB}, so the expression
24112 can contain function calls, variables, operators, and attribute references.
24115 Continues execution following a breakpoint, until the next breakpoint or the
24116 termination of the program.
24119 Executes a single line after a breakpoint. If the next statement
24120 is a subprogram call, execution continues into (the first statement of)
24121 the called subprogram.
24124 Executes a single line. If this line is a subprogram call, executes and
24125 returns from the call.
24128 Lists a few lines around the current source location. In practice, it
24129 is usually more convenient to have a separate edit window open with the
24130 relevant source file displayed. Successive applications of this command
24131 print subsequent lines. The command can be given an argument which is a
24132 line number, in which case it displays a few lines around the specified one.
24135 Displays a backtrace of the call chain. This command is typically
24136 used after a breakpoint has occurred, to examine the sequence of calls that
24137 leads to the current breakpoint. The display includes one line for each
24138 activation record (frame) corresponding to an active subprogram.
24141 At a breakpoint, @code{GDB} can display the values of variables local
24142 to the current frame. The command @code{up} can be used to
24143 examine the contents of other active frames, by moving the focus up
24144 the stack, that is to say from callee to caller, one frame at a time.
24147 Moves the focus of @code{GDB} down from the frame currently being
24148 examined to the frame of its callee (the reverse of the previous command),
24150 @item frame @var{n}
24151 Inspect the frame with the given number. The value 0 denotes the frame
24152 of the current breakpoint, that is to say the top of the call stack.
24157 The above list is a very short introduction to the commands that
24158 @code{GDB} provides. Important additional capabilities, including conditional
24159 breakpoints, the ability to execute command sequences on a breakpoint,
24160 the ability to debug at the machine instruction level and many other
24161 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
24162 Debugging with GDB}. Note that most commands can be abbreviated
24163 (for example, c for continue, bt for backtrace).
24165 @node Using Ada Expressions
24166 @section Using Ada Expressions
24167 @cindex Ada expressions
24170 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
24171 extensions. The philosophy behind the design of this subset is
24175 That @code{GDB} should provide basic literals and access to operations for
24176 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
24177 leaving more sophisticated computations to subprograms written into the
24178 program (which therefore may be called from @code{GDB}).
24181 That type safety and strict adherence to Ada language restrictions
24182 are not particularly important to the @code{GDB} user.
24185 That brevity is important to the @code{GDB} user.
24189 Thus, for brevity, the debugger acts as if there were
24190 implicit @code{with} and @code{use} clauses in effect for all user-written
24191 packages, thus making it unnecessary to fully qualify most names with
24192 their packages, regardless of context. Where this causes ambiguity,
24193 @code{GDB} asks the user's intent.
24195 For details on the supported Ada syntax, see @ref{Top,, Debugging with
24196 GDB, gdb, Debugging with GDB}.
24198 @node Calling User-Defined Subprograms
24199 @section Calling User-Defined Subprograms
24202 An important capability of @code{GDB} is the ability to call user-defined
24203 subprograms while debugging. This is achieved simply by entering
24204 a subprogram call statement in the form:
24207 call subprogram-name (parameters)
24211 The keyword @code{call} can be omitted in the normal case where the
24212 @code{subprogram-name} does not coincide with any of the predefined
24213 @code{GDB} commands.
24215 The effect is to invoke the given subprogram, passing it the
24216 list of parameters that is supplied. The parameters can be expressions and
24217 can include variables from the program being debugged. The
24218 subprogram must be defined
24219 at the library level within your program, and @code{GDB} will call the
24220 subprogram within the environment of your program execution (which
24221 means that the subprogram is free to access or even modify variables
24222 within your program).
24224 The most important use of this facility is in allowing the inclusion of
24225 debugging routines that are tailored to particular data structures
24226 in your program. Such debugging routines can be written to provide a suitably
24227 high-level description of an abstract type, rather than a low-level dump
24228 of its physical layout. After all, the standard
24229 @code{GDB print} command only knows the physical layout of your
24230 types, not their abstract meaning. Debugging routines can provide information
24231 at the desired semantic level and are thus enormously useful.
24233 For example, when debugging GNAT itself, it is crucial to have access to
24234 the contents of the tree nodes used to represent the program internally.
24235 But tree nodes are represented simply by an integer value (which in turn
24236 is an index into a table of nodes).
24237 Using the @code{print} command on a tree node would simply print this integer
24238 value, which is not very useful. But the PN routine (defined in file
24239 treepr.adb in the GNAT sources) takes a tree node as input, and displays
24240 a useful high level representation of the tree node, which includes the
24241 syntactic category of the node, its position in the source, the integers
24242 that denote descendant nodes and parent node, as well as varied
24243 semantic information. To study this example in more detail, you might want to
24244 look at the body of the PN procedure in the stated file.
24246 @node Using the Next Command in a Function
24247 @section Using the Next Command in a Function
24250 When you use the @code{next} command in a function, the current source
24251 location will advance to the next statement as usual. A special case
24252 arises in the case of a @code{return} statement.
24254 Part of the code for a return statement is the ``epilog'' of the function.
24255 This is the code that returns to the caller. There is only one copy of
24256 this epilog code, and it is typically associated with the last return
24257 statement in the function if there is more than one return. In some
24258 implementations, this epilog is associated with the first statement
24261 The result is that if you use the @code{next} command from a return
24262 statement that is not the last return statement of the function you
24263 may see a strange apparent jump to the last return statement or to
24264 the start of the function. You should simply ignore this odd jump.
24265 The value returned is always that from the first return statement
24266 that was stepped through.
24268 @node Ada Exceptions
24269 @section Breaking on Ada Exceptions
24273 You can set breakpoints that trip when your program raises
24274 selected exceptions.
24277 @item break exception
24278 Set a breakpoint that trips whenever (any task in the) program raises
24281 @item break exception @var{name}
24282 Set a breakpoint that trips whenever (any task in the) program raises
24283 the exception @var{name}.
24285 @item break exception unhandled
24286 Set a breakpoint that trips whenever (any task in the) program raises an
24287 exception for which there is no handler.
24289 @item info exceptions
24290 @itemx info exceptions @var{regexp}
24291 The @code{info exceptions} command permits the user to examine all defined
24292 exceptions within Ada programs. With a regular expression, @var{regexp}, as
24293 argument, prints out only those exceptions whose name matches @var{regexp}.
24301 @code{GDB} allows the following task-related commands:
24305 This command shows a list of current Ada tasks, as in the following example:
24312 ID TID P-ID Thread Pri State Name
24313 1 8088000 0 807e000 15 Child Activation Wait main_task
24314 2 80a4000 1 80ae000 15 Accept/Select Wait b
24315 3 809a800 1 80a4800 15 Child Activation Wait a
24316 * 4 80ae800 3 80b8000 15 Running c
24320 In this listing, the asterisk before the first task indicates it to be the
24321 currently running task. The first column lists the task ID that is used
24322 to refer to tasks in the following commands.
24324 @item break @var{linespec} task @var{taskid}
24325 @itemx break @var{linespec} task @var{taskid} if @dots{}
24326 @cindex Breakpoints and tasks
24327 These commands are like the @code{break @dots{} thread @dots{}}.
24328 @var{linespec} specifies source lines.
24330 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
24331 to specify that you only want @code{GDB} to stop the program when a
24332 particular Ada task reaches this breakpoint. @var{taskid} is one of the
24333 numeric task identifiers assigned by @code{GDB}, shown in the first
24334 column of the @samp{info tasks} display.
24336 If you do not specify @samp{task @var{taskid}} when you set a
24337 breakpoint, the breakpoint applies to @emph{all} tasks of your
24340 You can use the @code{task} qualifier on conditional breakpoints as
24341 well; in this case, place @samp{task @var{taskid}} before the
24342 breakpoint condition (before the @code{if}).
24344 @item task @var{taskno}
24345 @cindex Task switching
24347 This command allows to switch to the task referred by @var{taskno}. In
24348 particular, This allows to browse the backtrace of the specified
24349 task. It is advised to switch back to the original task before
24350 continuing execution otherwise the scheduling of the program may be
24355 For more detailed information on the tasking support,
24356 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
24358 @node Debugging Generic Units
24359 @section Debugging Generic Units
24360 @cindex Debugging Generic Units
24364 GNAT always uses code expansion for generic instantiation. This means that
24365 each time an instantiation occurs, a complete copy of the original code is
24366 made, with appropriate substitutions of formals by actuals.
24368 It is not possible to refer to the original generic entities in
24369 @code{GDB}, but it is always possible to debug a particular instance of
24370 a generic, by using the appropriate expanded names. For example, if we have
24372 @smallexample @c ada
24377 generic package k is
24378 procedure kp (v1 : in out integer);
24382 procedure kp (v1 : in out integer) is
24388 package k1 is new k;
24389 package k2 is new k;
24391 var : integer := 1;
24404 Then to break on a call to procedure kp in the k2 instance, simply
24408 (gdb) break g.k2.kp
24412 When the breakpoint occurs, you can step through the code of the
24413 instance in the normal manner and examine the values of local variables, as for
24416 @node GNAT Abnormal Termination or Failure to Terminate
24417 @section GNAT Abnormal Termination or Failure to Terminate
24418 @cindex GNAT Abnormal Termination or Failure to Terminate
24421 When presented with programs that contain serious errors in syntax
24423 GNAT may on rare occasions experience problems in operation, such
24425 segmentation fault or illegal memory access, raising an internal
24426 exception, terminating abnormally, or failing to terminate at all.
24427 In such cases, you can activate
24428 various features of GNAT that can help you pinpoint the construct in your
24429 program that is the likely source of the problem.
24431 The following strategies are presented in increasing order of
24432 difficulty, corresponding to your experience in using GNAT and your
24433 familiarity with compiler internals.
24437 Run @command{gcc} with the @option{-gnatf}. This first
24438 switch causes all errors on a given line to be reported. In its absence,
24439 only the first error on a line is displayed.
24441 The @option{-gnatdO} switch causes errors to be displayed as soon as they
24442 are encountered, rather than after compilation is terminated. If GNAT
24443 terminates prematurely or goes into an infinite loop, the last error
24444 message displayed may help to pinpoint the culprit.
24447 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
24448 mode, @command{gcc} produces ongoing information about the progress of the
24449 compilation and provides the name of each procedure as code is
24450 generated. This switch allows you to find which Ada procedure was being
24451 compiled when it encountered a code generation problem.
24454 @cindex @option{-gnatdc} switch
24455 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
24456 switch that does for the front-end what @option{^-v^VERBOSE^} does
24457 for the back end. The system prints the name of each unit,
24458 either a compilation unit or nested unit, as it is being analyzed.
24460 Finally, you can start
24461 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
24462 front-end of GNAT, and can be run independently (normally it is just
24463 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
24464 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
24465 @code{where} command is the first line of attack; the variable
24466 @code{lineno} (seen by @code{print lineno}), used by the second phase of
24467 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
24468 which the execution stopped, and @code{input_file name} indicates the name of
24472 @node Naming Conventions for GNAT Source Files
24473 @section Naming Conventions for GNAT Source Files
24476 In order to examine the workings of the GNAT system, the following
24477 brief description of its organization may be helpful:
24481 Files with prefix @file{^sc^SC^} contain the lexical scanner.
24484 All files prefixed with @file{^par^PAR^} are components of the parser. The
24485 numbers correspond to chapters of the Ada Reference Manual. For example,
24486 parsing of select statements can be found in @file{par-ch9.adb}.
24489 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
24490 numbers correspond to chapters of the Ada standard. For example, all
24491 issues involving context clauses can be found in @file{sem_ch10.adb}. In
24492 addition, some features of the language require sufficient special processing
24493 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
24494 dynamic dispatching, etc.
24497 All files prefixed with @file{^exp^EXP^} perform normalization and
24498 expansion of the intermediate representation (abstract syntax tree, or AST).
24499 these files use the same numbering scheme as the parser and semantics files.
24500 For example, the construction of record initialization procedures is done in
24501 @file{exp_ch3.adb}.
24504 The files prefixed with @file{^bind^BIND^} implement the binder, which
24505 verifies the consistency of the compilation, determines an order of
24506 elaboration, and generates the bind file.
24509 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24510 data structures used by the front-end.
24513 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24514 the abstract syntax tree as produced by the parser.
24517 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24518 all entities, computed during semantic analysis.
24521 Library management issues are dealt with in files with prefix
24527 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24528 defined in Annex A.
24533 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24534 defined in Annex B.
24538 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24539 both language-defined children and GNAT run-time routines.
24543 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24544 general-purpose packages, fully documented in their specs. All
24545 the other @file{.c} files are modifications of common @command{gcc} files.
24548 @node Getting Internal Debugging Information
24549 @section Getting Internal Debugging Information
24552 Most compilers have internal debugging switches and modes. GNAT
24553 does also, except GNAT internal debugging switches and modes are not
24554 secret. A summary and full description of all the compiler and binder
24555 debug flags are in the file @file{debug.adb}. You must obtain the
24556 sources of the compiler to see the full detailed effects of these flags.
24558 The switches that print the source of the program (reconstructed from
24559 the internal tree) are of general interest for user programs, as are the
24561 the full internal tree, and the entity table (the symbol table
24562 information). The reconstructed source provides a readable version of the
24563 program after the front-end has completed analysis and expansion,
24564 and is useful when studying the performance of specific constructs.
24565 For example, constraint checks are indicated, complex aggregates
24566 are replaced with loops and assignments, and tasking primitives
24567 are replaced with run-time calls.
24569 @node Stack Traceback
24570 @section Stack Traceback
24572 @cindex stack traceback
24573 @cindex stack unwinding
24576 Traceback is a mechanism to display the sequence of subprogram calls that
24577 leads to a specified execution point in a program. Often (but not always)
24578 the execution point is an instruction at which an exception has been raised.
24579 This mechanism is also known as @i{stack unwinding} because it obtains
24580 its information by scanning the run-time stack and recovering the activation
24581 records of all active subprograms. Stack unwinding is one of the most
24582 important tools for program debugging.
24584 The first entry stored in traceback corresponds to the deepest calling level,
24585 that is to say the subprogram currently executing the instruction
24586 from which we want to obtain the traceback.
24588 Note that there is no runtime performance penalty when stack traceback
24589 is enabled, and no exception is raised during program execution.
24592 * Non-Symbolic Traceback::
24593 * Symbolic Traceback::
24596 @node Non-Symbolic Traceback
24597 @subsection Non-Symbolic Traceback
24598 @cindex traceback, non-symbolic
24601 Note: this feature is not supported on all platforms. See
24602 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24606 * Tracebacks From an Unhandled Exception::
24607 * Tracebacks From Exception Occurrences (non-symbolic)::
24608 * Tracebacks From Anywhere in a Program (non-symbolic)::
24611 @node Tracebacks From an Unhandled Exception
24612 @subsubsection Tracebacks From an Unhandled Exception
24615 A runtime non-symbolic traceback is a list of addresses of call instructions.
24616 To enable this feature you must use the @option{-E}
24617 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24618 of exception information. You can retrieve this information using the
24619 @code{addr2line} tool.
24621 Here is a simple example:
24623 @smallexample @c ada
24629 raise Constraint_Error;
24644 $ gnatmake stb -bargs -E
24647 Execution terminated by unhandled exception
24648 Exception name: CONSTRAINT_ERROR
24650 Call stack traceback locations:
24651 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24655 As we see the traceback lists a sequence of addresses for the unhandled
24656 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24657 guess that this exception come from procedure P1. To translate these
24658 addresses into the source lines where the calls appear, the
24659 @code{addr2line} tool, described below, is invaluable. The use of this tool
24660 requires the program to be compiled with debug information.
24663 $ gnatmake -g stb -bargs -E
24666 Execution terminated by unhandled exception
24667 Exception name: CONSTRAINT_ERROR
24669 Call stack traceback locations:
24670 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24672 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24673 0x4011f1 0x77e892a4
24675 00401373 at d:/stb/stb.adb:5
24676 0040138B at d:/stb/stb.adb:10
24677 0040139C at d:/stb/stb.adb:14
24678 00401335 at d:/stb/b~stb.adb:104
24679 004011C4 at /build/@dots{}/crt1.c:200
24680 004011F1 at /build/@dots{}/crt1.c:222
24681 77E892A4 in ?? at ??:0
24685 The @code{addr2line} tool has several other useful options:
24689 to get the function name corresponding to any location
24691 @item --demangle=gnat
24692 to use the gnat decoding mode for the function names. Note that
24693 for binutils version 2.9.x the option is simply @option{--demangle}.
24697 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24698 0x40139c 0x401335 0x4011c4 0x4011f1
24700 00401373 in stb.p1 at d:/stb/stb.adb:5
24701 0040138B in stb.p2 at d:/stb/stb.adb:10
24702 0040139C in stb at d:/stb/stb.adb:14
24703 00401335 in main at d:/stb/b~stb.adb:104
24704 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24705 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24709 From this traceback we can see that the exception was raised in
24710 @file{stb.adb} at line 5, which was reached from a procedure call in
24711 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24712 which contains the call to the main program.
24713 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24714 and the output will vary from platform to platform.
24716 It is also possible to use @code{GDB} with these traceback addresses to debug
24717 the program. For example, we can break at a given code location, as reported
24718 in the stack traceback:
24724 Furthermore, this feature is not implemented inside Windows DLL. Only
24725 the non-symbolic traceback is reported in this case.
24728 (gdb) break *0x401373
24729 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24733 It is important to note that the stack traceback addresses
24734 do not change when debug information is included. This is particularly useful
24735 because it makes it possible to release software without debug information (to
24736 minimize object size), get a field report that includes a stack traceback
24737 whenever an internal bug occurs, and then be able to retrieve the sequence
24738 of calls with the same program compiled with debug information.
24740 @node Tracebacks From Exception Occurrences (non-symbolic)
24741 @subsubsection Tracebacks From Exception Occurrences
24744 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24745 The stack traceback is attached to the exception information string, and can
24746 be retrieved in an exception handler within the Ada program, by means of the
24747 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24749 @smallexample @c ada
24751 with Ada.Exceptions;
24756 use Ada.Exceptions;
24764 Text_IO.Put_Line (Exception_Information (E));
24778 This program will output:
24783 Exception name: CONSTRAINT_ERROR
24784 Message: stb.adb:12
24785 Call stack traceback locations:
24786 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24789 @node Tracebacks From Anywhere in a Program (non-symbolic)
24790 @subsubsection Tracebacks From Anywhere in a Program
24793 It is also possible to retrieve a stack traceback from anywhere in a
24794 program. For this you need to
24795 use the @code{GNAT.Traceback} API. This package includes a procedure called
24796 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24797 display procedures described below. It is not necessary to use the
24798 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24799 is invoked explicitly.
24802 In the following example we compute a traceback at a specific location in
24803 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24804 convert addresses to strings:
24806 @smallexample @c ada
24808 with GNAT.Traceback;
24809 with GNAT.Debug_Utilities;
24815 use GNAT.Traceback;
24818 TB : Tracebacks_Array (1 .. 10);
24819 -- We are asking for a maximum of 10 stack frames.
24821 -- Len will receive the actual number of stack frames returned.
24823 Call_Chain (TB, Len);
24825 Text_IO.Put ("In STB.P1 : ");
24827 for K in 1 .. Len loop
24828 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24849 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24850 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24854 You can then get further information by invoking the @code{addr2line}
24855 tool as described earlier (note that the hexadecimal addresses
24856 need to be specified in C format, with a leading ``0x'').
24858 @node Symbolic Traceback
24859 @subsection Symbolic Traceback
24860 @cindex traceback, symbolic
24863 A symbolic traceback is a stack traceback in which procedure names are
24864 associated with each code location.
24867 Note that this feature is not supported on all platforms. See
24868 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24869 list of currently supported platforms.
24872 Note that the symbolic traceback requires that the program be compiled
24873 with debug information. If it is not compiled with debug information
24874 only the non-symbolic information will be valid.
24877 * Tracebacks From Exception Occurrences (symbolic)::
24878 * Tracebacks From Anywhere in a Program (symbolic)::
24881 @node Tracebacks From Exception Occurrences (symbolic)
24882 @subsubsection Tracebacks From Exception Occurrences
24884 @smallexample @c ada
24886 with GNAT.Traceback.Symbolic;
24892 raise Constraint_Error;
24909 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24914 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24917 0040149F in stb.p1 at stb.adb:8
24918 004014B7 in stb.p2 at stb.adb:13
24919 004014CF in stb.p3 at stb.adb:18
24920 004015DD in ada.stb at stb.adb:22
24921 00401461 in main at b~stb.adb:168
24922 004011C4 in __mingw_CRTStartup at crt1.c:200
24923 004011F1 in mainCRTStartup at crt1.c:222
24924 77E892A4 in ?? at ??:0
24928 In the above example the ``.\'' syntax in the @command{gnatmake} command
24929 is currently required by @command{addr2line} for files that are in
24930 the current working directory.
24931 Moreover, the exact sequence of linker options may vary from platform
24933 The above @option{-largs} section is for Windows platforms. By contrast,
24934 under Unix there is no need for the @option{-largs} section.
24935 Differences across platforms are due to details of linker implementation.
24937 @node Tracebacks From Anywhere in a Program (symbolic)
24938 @subsubsection Tracebacks From Anywhere in a Program
24941 It is possible to get a symbolic stack traceback
24942 from anywhere in a program, just as for non-symbolic tracebacks.
24943 The first step is to obtain a non-symbolic
24944 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24945 information. Here is an example:
24947 @smallexample @c ada
24949 with GNAT.Traceback;
24950 with GNAT.Traceback.Symbolic;
24955 use GNAT.Traceback;
24956 use GNAT.Traceback.Symbolic;
24959 TB : Tracebacks_Array (1 .. 10);
24960 -- We are asking for a maximum of 10 stack frames.
24962 -- Len will receive the actual number of stack frames returned.
24964 Call_Chain (TB, Len);
24965 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24978 @c ******************************
24980 @node Compatibility with HP Ada
24981 @chapter Compatibility with HP Ada
24982 @cindex Compatibility
24987 @cindex Compatibility between GNAT and HP Ada
24988 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24989 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24990 GNAT is highly compatible
24991 with HP Ada, and it should generally be straightforward to port code
24992 from the HP Ada environment to GNAT. However, there are a few language
24993 and implementation differences of which the user must be aware. These
24994 differences are discussed in this chapter. In
24995 addition, the operating environment and command structure for the
24996 compiler are different, and these differences are also discussed.
24998 For further details on these and other compatibility issues,
24999 see Appendix E of the HP publication
25000 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
25002 Except where otherwise indicated, the description of GNAT for OpenVMS
25003 applies to both the Alpha and I64 platforms.
25005 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
25006 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
25008 The discussion in this chapter addresses specifically the implementation
25009 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
25010 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
25011 GNAT always follows the Alpha implementation.
25013 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
25014 attributes are recognized, although only a subset of them can sensibly
25015 be implemented. The description of pragmas in
25016 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
25017 indicates whether or not they are applicable to non-VMS systems.
25020 * Ada Language Compatibility::
25021 * Differences in the Definition of Package System::
25022 * Language-Related Features::
25023 * The Package STANDARD::
25024 * The Package SYSTEM::
25025 * Tasking and Task-Related Features::
25026 * Pragmas and Pragma-Related Features::
25027 * Library of Predefined Units::
25029 * Main Program Definition::
25030 * Implementation-Defined Attributes::
25031 * Compiler and Run-Time Interfacing::
25032 * Program Compilation and Library Management::
25034 * Implementation Limits::
25035 * Tools and Utilities::
25038 @node Ada Language Compatibility
25039 @section Ada Language Compatibility
25042 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
25043 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
25044 with Ada 83, and therefore Ada 83 programs will compile
25045 and run under GNAT with
25046 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
25047 provides details on specific incompatibilities.
25049 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
25050 as well as the pragma @code{ADA_83}, to force the compiler to
25051 operate in Ada 83 mode. This mode does not guarantee complete
25052 conformance to Ada 83, but in practice is sufficient to
25053 eliminate most sources of incompatibilities.
25054 In particular, it eliminates the recognition of the
25055 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
25056 in Ada 83 programs is legal, and handles the cases of packages
25057 with optional bodies, and generics that instantiate unconstrained
25058 types without the use of @code{(<>)}.
25060 @node Differences in the Definition of Package System
25061 @section Differences in the Definition of Package @code{System}
25064 An Ada compiler is allowed to add
25065 implementation-dependent declarations to package @code{System}.
25067 GNAT does not take advantage of this permission, and the version of
25068 @code{System} provided by GNAT exactly matches that defined in the Ada
25071 However, HP Ada adds an extensive set of declarations to package
25073 as fully documented in the HP Ada manuals. To minimize changes required
25074 for programs that make use of these extensions, GNAT provides the pragma
25075 @code{Extend_System} for extending the definition of package System. By using:
25076 @cindex pragma @code{Extend_System}
25077 @cindex @code{Extend_System} pragma
25079 @smallexample @c ada
25082 pragma Extend_System (Aux_DEC);
25088 the set of definitions in @code{System} is extended to include those in
25089 package @code{System.Aux_DEC}.
25090 @cindex @code{System.Aux_DEC} package
25091 @cindex @code{Aux_DEC} package (child of @code{System})
25092 These definitions are incorporated directly into package @code{System},
25093 as though they had been declared there. For a
25094 list of the declarations added, see the spec of this package,
25095 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
25096 @cindex @file{s-auxdec.ads} file
25097 The pragma @code{Extend_System} is a configuration pragma, which means that
25098 it can be placed in the file @file{gnat.adc}, so that it will automatically
25099 apply to all subsequent compilations. See @ref{Configuration Pragmas},
25100 for further details.
25102 An alternative approach that avoids the use of the non-standard
25103 @code{Extend_System} pragma is to add a context clause to the unit that
25104 references these facilities:
25106 @smallexample @c ada
25108 with System.Aux_DEC;
25109 use System.Aux_DEC;
25114 The effect is not quite semantically identical to incorporating
25115 the declarations directly into package @code{System},
25116 but most programs will not notice a difference
25117 unless they use prefix notation (e.g.@: @code{System.Integer_8})
25118 to reference the entities directly in package @code{System}.
25119 For units containing such references,
25120 the prefixes must either be removed, or the pragma @code{Extend_System}
25123 @node Language-Related Features
25124 @section Language-Related Features
25127 The following sections highlight differences in types,
25128 representations of types, operations, alignment, and
25132 * Integer Types and Representations::
25133 * Floating-Point Types and Representations::
25134 * Pragmas Float_Representation and Long_Float::
25135 * Fixed-Point Types and Representations::
25136 * Record and Array Component Alignment::
25137 * Address Clauses::
25138 * Other Representation Clauses::
25141 @node Integer Types and Representations
25142 @subsection Integer Types and Representations
25145 The set of predefined integer types is identical in HP Ada and GNAT.
25146 Furthermore the representation of these integer types is also identical,
25147 including the capability of size clauses forcing biased representation.
25150 HP Ada for OpenVMS Alpha systems has defined the
25151 following additional integer types in package @code{System}:
25168 @code{LARGEST_INTEGER}
25172 In GNAT, the first four of these types may be obtained from the
25173 standard Ada package @code{Interfaces}.
25174 Alternatively, by use of the pragma @code{Extend_System}, identical
25175 declarations can be referenced directly in package @code{System}.
25176 On both GNAT and HP Ada, the maximum integer size is 64 bits.
25178 @node Floating-Point Types and Representations
25179 @subsection Floating-Point Types and Representations
25180 @cindex Floating-Point types
25183 The set of predefined floating-point types is identical in HP Ada and GNAT.
25184 Furthermore the representation of these floating-point
25185 types is also identical. One important difference is that the default
25186 representation for HP Ada is @code{VAX_Float}, but the default representation
25189 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
25190 pragma @code{Float_Representation} as described in the HP Ada
25192 For example, the declarations:
25194 @smallexample @c ada
25196 type F_Float is digits 6;
25197 pragma Float_Representation (VAX_Float, F_Float);
25202 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
25204 This set of declarations actually appears in @code{System.Aux_DEC},
25206 the full set of additional floating-point declarations provided in
25207 the HP Ada version of package @code{System}.
25208 This and similar declarations may be accessed in a user program
25209 by using pragma @code{Extend_System}. The use of this
25210 pragma, and the related pragma @code{Long_Float} is described in further
25211 detail in the following section.
25213 @node Pragmas Float_Representation and Long_Float
25214 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
25217 HP Ada provides the pragma @code{Float_Representation}, which
25218 acts as a program library switch to allow control over
25219 the internal representation chosen for the predefined
25220 floating-point types declared in the package @code{Standard}.
25221 The format of this pragma is as follows:
25223 @smallexample @c ada
25225 pragma Float_Representation(VAX_Float | IEEE_Float);
25230 This pragma controls the representation of floating-point
25235 @code{VAX_Float} specifies that floating-point
25236 types are represented by default with the VAX system hardware types
25237 @code{F-floating}, @code{D-floating}, @code{G-floating}.
25238 Note that the @code{H-floating}
25239 type was available only on VAX systems, and is not available
25240 in either HP Ada or GNAT.
25243 @code{IEEE_Float} specifies that floating-point
25244 types are represented by default with the IEEE single and
25245 double floating-point types.
25249 GNAT provides an identical implementation of the pragma
25250 @code{Float_Representation}, except that it functions as a
25251 configuration pragma. Note that the
25252 notion of configuration pragma corresponds closely to the
25253 HP Ada notion of a program library switch.
25255 When no pragma is used in GNAT, the default is @code{IEEE_Float},
25257 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
25258 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
25259 advisable to change the format of numbers passed to standard library
25260 routines, and if necessary explicit type conversions may be needed.
25262 The use of @code{IEEE_Float} is recommended in GNAT since it is more
25263 efficient, and (given that it conforms to an international standard)
25264 potentially more portable.
25265 The situation in which @code{VAX_Float} may be useful is in interfacing
25266 to existing code and data that expect the use of @code{VAX_Float}.
25267 In such a situation use the predefined @code{VAX_Float}
25268 types in package @code{System}, as extended by
25269 @code{Extend_System}. For example, use @code{System.F_Float}
25270 to specify the 32-bit @code{F-Float} format.
25273 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
25274 to allow control over the internal representation chosen
25275 for the predefined type @code{Long_Float} and for floating-point
25276 type declarations with digits specified in the range 7 .. 15.
25277 The format of this pragma is as follows:
25279 @smallexample @c ada
25281 pragma Long_Float (D_FLOAT | G_FLOAT);
25285 @node Fixed-Point Types and Representations
25286 @subsection Fixed-Point Types and Representations
25289 On HP Ada for OpenVMS Alpha systems, rounding is
25290 away from zero for both positive and negative numbers.
25291 Therefore, @code{+0.5} rounds to @code{1},
25292 and @code{-0.5} rounds to @code{-1}.
25294 On GNAT the results of operations
25295 on fixed-point types are in accordance with the Ada
25296 rules. In particular, results of operations on decimal
25297 fixed-point types are truncated.
25299 @node Record and Array Component Alignment
25300 @subsection Record and Array Component Alignment
25303 On HP Ada for OpenVMS Alpha, all non-composite components
25304 are aligned on natural boundaries. For example, 1-byte
25305 components are aligned on byte boundaries, 2-byte
25306 components on 2-byte boundaries, 4-byte components on 4-byte
25307 byte boundaries, and so on. The OpenVMS Alpha hardware
25308 runs more efficiently with naturally aligned data.
25310 On GNAT, alignment rules are compatible
25311 with HP Ada for OpenVMS Alpha.
25313 @node Address Clauses
25314 @subsection Address Clauses
25317 In HP Ada and GNAT, address clauses are supported for
25318 objects and imported subprograms.
25319 The predefined type @code{System.Address} is a private type
25320 in both compilers on Alpha OpenVMS, with the same representation
25321 (it is simply a machine pointer). Addition, subtraction, and comparison
25322 operations are available in the standard Ada package
25323 @code{System.Storage_Elements}, or in package @code{System}
25324 if it is extended to include @code{System.Aux_DEC} using a
25325 pragma @code{Extend_System} as previously described.
25327 Note that code that @code{with}'s both this extended package @code{System}
25328 and the package @code{System.Storage_Elements} should not @code{use}
25329 both packages, or ambiguities will result. In general it is better
25330 not to mix these two sets of facilities. The Ada package was
25331 designed specifically to provide the kind of features that HP Ada
25332 adds directly to package @code{System}.
25334 The type @code{System.Address} is a 64-bit integer type in GNAT for
25335 I64 OpenVMS. For more information,
25336 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
25338 GNAT is compatible with HP Ada in its handling of address
25339 clauses, except for some limitations in
25340 the form of address clauses for composite objects with
25341 initialization. Such address clauses are easily replaced
25342 by the use of an explicitly-defined constant as described
25343 in the Ada Reference Manual (13.1(22)). For example, the sequence
25346 @smallexample @c ada
25348 X, Y : Integer := Init_Func;
25349 Q : String (X .. Y) := "abc";
25351 for Q'Address use Compute_Address;
25356 will be rejected by GNAT, since the address cannot be computed at the time
25357 that @code{Q} is declared. To achieve the intended effect, write instead:
25359 @smallexample @c ada
25362 X, Y : Integer := Init_Func;
25363 Q_Address : constant Address := Compute_Address;
25364 Q : String (X .. Y) := "abc";
25366 for Q'Address use Q_Address;
25372 which will be accepted by GNAT (and other Ada compilers), and is also
25373 compatible with Ada 83. A fuller description of the restrictions
25374 on address specifications is found in @ref{Top, GNAT Reference Manual,
25375 About This Guide, gnat_rm, GNAT Reference Manual}.
25377 @node Other Representation Clauses
25378 @subsection Other Representation Clauses
25381 GNAT implements in a compatible manner all the representation
25382 clauses supported by HP Ada. In addition, GNAT
25383 implements the representation clause forms that were introduced in Ada 95,
25384 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
25386 @node The Package STANDARD
25387 @section The Package @code{STANDARD}
25390 The package @code{STANDARD}, as implemented by HP Ada, is fully
25391 described in the @cite{Ada Reference Manual} and in the
25392 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
25393 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
25395 In addition, HP Ada supports the Latin-1 character set in
25396 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
25397 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
25398 the type @code{WIDE_CHARACTER}.
25400 The floating-point types supported by GNAT are those
25401 supported by HP Ada, but the defaults are different, and are controlled by
25402 pragmas. See @ref{Floating-Point Types and Representations}, for details.
25404 @node The Package SYSTEM
25405 @section The Package @code{SYSTEM}
25408 HP Ada provides a specific version of the package
25409 @code{SYSTEM} for each platform on which the language is implemented.
25410 For the complete spec of the package @code{SYSTEM}, see
25411 Appendix F of the @cite{HP Ada Language Reference Manual}.
25413 On HP Ada, the package @code{SYSTEM} includes the following conversion
25416 @item @code{TO_ADDRESS(INTEGER)}
25418 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
25420 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
25422 @item @code{TO_INTEGER(ADDRESS)}
25424 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
25426 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
25427 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
25431 By default, GNAT supplies a version of @code{SYSTEM} that matches
25432 the definition given in the @cite{Ada Reference Manual}.
25434 is a subset of the HP system definitions, which is as
25435 close as possible to the original definitions. The only difference
25436 is that the definition of @code{SYSTEM_NAME} is different:
25438 @smallexample @c ada
25440 type Name is (SYSTEM_NAME_GNAT);
25441 System_Name : constant Name := SYSTEM_NAME_GNAT;
25446 Also, GNAT adds the Ada declarations for
25447 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
25449 However, the use of the following pragma causes GNAT
25450 to extend the definition of package @code{SYSTEM} so that it
25451 encompasses the full set of HP-specific extensions,
25452 including the functions listed above:
25454 @smallexample @c ada
25456 pragma Extend_System (Aux_DEC);
25461 The pragma @code{Extend_System} is a configuration pragma that
25462 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
25463 Extend_System,,, gnat_rm, GNAT Reference Manual}, for further details.
25465 HP Ada does not allow the recompilation of the package
25466 @code{SYSTEM}. Instead HP Ada provides several pragmas
25467 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
25468 to modify values in the package @code{SYSTEM}.
25469 On OpenVMS Alpha systems, the pragma
25470 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
25471 its single argument.
25473 GNAT does permit the recompilation of package @code{SYSTEM} using
25474 the special switch @option{-gnatg}, and this switch can be used if
25475 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
25476 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
25477 or @code{MEMORY_SIZE} by any other means.
25479 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
25480 enumeration literal @code{SYSTEM_NAME_GNAT}.
25482 The definitions provided by the use of
25484 @smallexample @c ada
25485 pragma Extend_System (AUX_Dec);
25489 are virtually identical to those provided by the HP Ada 83 package
25490 @code{SYSTEM}. One important difference is that the name of the
25492 function for type @code{UNSIGNED_LONGWORD} is changed to
25493 @code{TO_ADDRESS_LONG}.
25494 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual}, for a
25495 discussion of why this change was necessary.
25498 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
25500 an extension to Ada 83 not strictly compatible with the reference manual.
25501 GNAT, in order to be exactly compatible with the standard,
25502 does not provide this capability. In HP Ada 83, the
25503 point of this definition is to deal with a call like:
25505 @smallexample @c ada
25506 TO_ADDRESS (16#12777#);
25510 Normally, according to Ada 83 semantics, one would expect this to be
25511 ambiguous, since it matches both the @code{INTEGER} and
25512 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25513 However, in HP Ada 83, there is no ambiguity, since the
25514 definition using @i{universal_integer} takes precedence.
25516 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25518 not possible to be 100% compatible. Since there are many programs using
25519 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25521 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25522 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25524 @smallexample @c ada
25525 function To_Address (X : Integer) return Address;
25526 pragma Pure_Function (To_Address);
25528 function To_Address_Long (X : Unsigned_Longword) return Address;
25529 pragma Pure_Function (To_Address_Long);
25533 This means that programs using @code{TO_ADDRESS} for
25534 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25536 @node Tasking and Task-Related Features
25537 @section Tasking and Task-Related Features
25540 This section compares the treatment of tasking in GNAT
25541 and in HP Ada for OpenVMS Alpha.
25542 The GNAT description applies to both Alpha and I64 OpenVMS.
25543 For detailed information on tasking in
25544 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25545 relevant run-time reference manual.
25548 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25549 * Assigning Task IDs::
25550 * Task IDs and Delays::
25551 * Task-Related Pragmas::
25552 * Scheduling and Task Priority::
25554 * External Interrupts::
25557 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25558 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25561 On OpenVMS Alpha systems, each Ada task (except a passive
25562 task) is implemented as a single stream of execution
25563 that is created and managed by the kernel. On these
25564 systems, HP Ada tasking support is based on DECthreads,
25565 an implementation of the POSIX standard for threads.
25567 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25568 code that calls DECthreads routines can be used together.
25569 The interaction between Ada tasks and DECthreads routines
25570 can have some benefits. For example when on OpenVMS Alpha,
25571 HP Ada can call C code that is already threaded.
25573 GNAT uses the facilities of DECthreads,
25574 and Ada tasks are mapped to threads.
25576 @node Assigning Task IDs
25577 @subsection Assigning Task IDs
25580 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25581 the environment task that executes the main program. On
25582 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25583 that have been created but are not yet activated.
25585 On OpenVMS Alpha systems, task IDs are assigned at
25586 activation. On GNAT systems, task IDs are also assigned at
25587 task creation but do not have the same form or values as
25588 task ID values in HP Ada. There is no null task, and the
25589 environment task does not have a specific task ID value.
25591 @node Task IDs and Delays
25592 @subsection Task IDs and Delays
25595 On OpenVMS Alpha systems, tasking delays are implemented
25596 using Timer System Services. The Task ID is used for the
25597 identification of the timer request (the @code{REQIDT} parameter).
25598 If Timers are used in the application take care not to use
25599 @code{0} for the identification, because cancelling such a timer
25600 will cancel all timers and may lead to unpredictable results.
25602 @node Task-Related Pragmas
25603 @subsection Task-Related Pragmas
25606 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25607 specification of the size of the guard area for a task
25608 stack. (The guard area forms an area of memory that has no
25609 read or write access and thus helps in the detection of
25610 stack overflow.) On OpenVMS Alpha systems, if the pragma
25611 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25612 area is created. In the absence of a pragma @code{TASK_STORAGE},
25613 a default guard area is created.
25615 GNAT supplies the following task-related pragmas:
25618 @item @code{TASK_INFO}
25620 This pragma appears within a task definition and
25621 applies to the task in which it appears. The argument
25622 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25624 @item @code{TASK_STORAGE}
25626 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25627 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25628 @code{SUPPRESS}, and @code{VOLATILE}.
25630 @node Scheduling and Task Priority
25631 @subsection Scheduling and Task Priority
25634 HP Ada implements the Ada language requirement that
25635 when two tasks are eligible for execution and they have
25636 different priorities, the lower priority task does not
25637 execute while the higher priority task is waiting. The HP
25638 Ada Run-Time Library keeps a task running until either the
25639 task is suspended or a higher priority task becomes ready.
25641 On OpenVMS Alpha systems, the default strategy is round-
25642 robin with preemption. Tasks of equal priority take turns
25643 at the processor. A task is run for a certain period of
25644 time and then placed at the tail of the ready queue for
25645 its priority level.
25647 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25648 which can be used to enable or disable round-robin
25649 scheduling of tasks with the same priority.
25650 See the relevant HP Ada run-time reference manual for
25651 information on using the pragmas to control HP Ada task
25654 GNAT follows the scheduling rules of Annex D (Real-Time
25655 Annex) of the @cite{Ada Reference Manual}. In general, this
25656 scheduling strategy is fully compatible with HP Ada
25657 although it provides some additional constraints (as
25658 fully documented in Annex D).
25659 GNAT implements time slicing control in a manner compatible with
25660 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25661 are identical to the HP Ada 83 pragma of the same name.
25662 Note that it is not possible to mix GNAT tasking and
25663 HP Ada 83 tasking in the same program, since the two run-time
25664 libraries are not compatible.
25666 @node The Task Stack
25667 @subsection The Task Stack
25670 In HP Ada, a task stack is allocated each time a
25671 non-passive task is activated. As soon as the task is
25672 terminated, the storage for the task stack is deallocated.
25673 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25674 a default stack size is used. Also, regardless of the size
25675 specified, some additional space is allocated for task
25676 management purposes. On OpenVMS Alpha systems, at least
25677 one page is allocated.
25679 GNAT handles task stacks in a similar manner. In accordance with
25680 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25681 an alternative method for controlling the task stack size.
25682 The specification of the attribute @code{T'STORAGE_SIZE} is also
25683 supported in a manner compatible with HP Ada.
25685 @node External Interrupts
25686 @subsection External Interrupts
25689 On HP Ada, external interrupts can be associated with task entries.
25690 GNAT is compatible with HP Ada in its handling of external interrupts.
25692 @node Pragmas and Pragma-Related Features
25693 @section Pragmas and Pragma-Related Features
25696 Both HP Ada and GNAT supply all language-defined pragmas
25697 as specified by the Ada 83 standard. GNAT also supplies all
25698 language-defined pragmas introduced by Ada 95 and Ada 2005.
25699 In addition, GNAT implements the implementation-defined pragmas
25703 @item @code{AST_ENTRY}
25705 @item @code{COMMON_OBJECT}
25707 @item @code{COMPONENT_ALIGNMENT}
25709 @item @code{EXPORT_EXCEPTION}
25711 @item @code{EXPORT_FUNCTION}
25713 @item @code{EXPORT_OBJECT}
25715 @item @code{EXPORT_PROCEDURE}
25717 @item @code{EXPORT_VALUED_PROCEDURE}
25719 @item @code{FLOAT_REPRESENTATION}
25723 @item @code{IMPORT_EXCEPTION}
25725 @item @code{IMPORT_FUNCTION}
25727 @item @code{IMPORT_OBJECT}
25729 @item @code{IMPORT_PROCEDURE}
25731 @item @code{IMPORT_VALUED_PROCEDURE}
25733 @item @code{INLINE_GENERIC}
25735 @item @code{INTERFACE_NAME}
25737 @item @code{LONG_FLOAT}
25739 @item @code{MAIN_STORAGE}
25741 @item @code{PASSIVE}
25743 @item @code{PSECT_OBJECT}
25745 @item @code{SHARE_GENERIC}
25747 @item @code{SUPPRESS_ALL}
25749 @item @code{TASK_STORAGE}
25751 @item @code{TIME_SLICE}
25757 These pragmas are all fully implemented, with the exception of @code{TITLE},
25758 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25759 recognized, but which have no
25760 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25761 use of Ada protected objects. In GNAT, all generics are inlined.
25763 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25764 a separate subprogram specification which must appear before the
25767 GNAT also supplies a number of implementation-defined pragmas as follows:
25769 @item @code{ABORT_DEFER}
25771 @item @code{ADA_83}
25773 @item @code{ADA_95}
25775 @item @code{ADA_05}
25777 @item @code{ANNOTATE}
25779 @item @code{ASSERT}
25781 @item @code{C_PASS_BY_COPY}
25783 @item @code{CPP_CLASS}
25785 @item @code{CPP_CONSTRUCTOR}
25787 @item @code{CPP_DESTRUCTOR}
25791 @item @code{EXTEND_SYSTEM}
25793 @item @code{LINKER_ALIAS}
25795 @item @code{LINKER_SECTION}
25797 @item @code{MACHINE_ATTRIBUTE}
25799 @item @code{NO_RETURN}
25801 @item @code{PURE_FUNCTION}
25803 @item @code{SOURCE_FILE_NAME}
25805 @item @code{SOURCE_REFERENCE}
25807 @item @code{TASK_INFO}
25809 @item @code{UNCHECKED_UNION}
25811 @item @code{UNIMPLEMENTED_UNIT}
25813 @item @code{UNIVERSAL_DATA}
25815 @item @code{UNSUPPRESS}
25817 @item @code{WARNINGS}
25819 @item @code{WEAK_EXTERNAL}
25823 For full details on these GNAT implementation-defined pragmas,
25824 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25828 * Restrictions on the Pragma INLINE::
25829 * Restrictions on the Pragma INTERFACE::
25830 * Restrictions on the Pragma SYSTEM_NAME::
25833 @node Restrictions on the Pragma INLINE
25834 @subsection Restrictions on Pragma @code{INLINE}
25837 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25839 @item Parameters cannot have a task type.
25841 @item Function results cannot be task types, unconstrained
25842 array types, or unconstrained types with discriminants.
25844 @item Bodies cannot declare the following:
25846 @item Subprogram body or stub (imported subprogram is allowed)
25850 @item Generic declarations
25852 @item Instantiations
25856 @item Access types (types derived from access types allowed)
25858 @item Array or record types
25860 @item Dependent tasks
25862 @item Direct recursive calls of subprogram or containing
25863 subprogram, directly or via a renaming
25869 In GNAT, the only restriction on pragma @code{INLINE} is that the
25870 body must occur before the call if both are in the same
25871 unit, and the size must be appropriately small. There are
25872 no other specific restrictions which cause subprograms to
25873 be incapable of being inlined.
25875 @node Restrictions on the Pragma INTERFACE
25876 @subsection Restrictions on Pragma @code{INTERFACE}
25879 The following restrictions on pragma @code{INTERFACE}
25880 are enforced by both HP Ada and GNAT:
25882 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25883 Default is the default on OpenVMS Alpha systems.
25885 @item Parameter passing: Language specifies default
25886 mechanisms but can be overridden with an @code{EXPORT} pragma.
25889 @item Ada: Use internal Ada rules.
25891 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25892 record or task type. Result cannot be a string, an
25893 array, or a record.
25895 @item Fortran: Parameters cannot have a task type. Result cannot
25896 be a string, an array, or a record.
25901 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25902 record parameters for all languages.
25904 @node Restrictions on the Pragma SYSTEM_NAME
25905 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25908 For HP Ada for OpenVMS Alpha, the enumeration literal
25909 for the type @code{NAME} is @code{OPENVMS_AXP}.
25910 In GNAT, the enumeration
25911 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25913 @node Library of Predefined Units
25914 @section Library of Predefined Units
25917 A library of predefined units is provided as part of the
25918 HP Ada and GNAT implementations. HP Ada does not provide
25919 the package @code{MACHINE_CODE} but instead recommends importing
25922 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25923 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25925 The HP Ada Predefined Library units are modified to remove post-Ada 83
25926 incompatibilities and to make them interoperable with GNAT
25927 (@pxref{Changes to DECLIB}, for details).
25928 The units are located in the @file{DECLIB} directory.
25930 The GNAT RTL is contained in
25931 the @file{ADALIB} directory, and
25932 the default search path is set up to find @code{DECLIB} units in preference
25933 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25934 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25937 * Changes to DECLIB::
25940 @node Changes to DECLIB
25941 @subsection Changes to @code{DECLIB}
25944 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25945 compatibility are minor and include the following:
25948 @item Adjusting the location of pragmas and record representation
25949 clauses to obey Ada 95 (and thus Ada 2005) rules
25951 @item Adding the proper notation to generic formal parameters
25952 that take unconstrained types in instantiation
25954 @item Adding pragma @code{ELABORATE_BODY} to package specs
25955 that have package bodies not otherwise allowed
25957 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25958 ``@code{PROTECTD}''.
25959 Currently these are found only in the @code{STARLET} package spec.
25961 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25962 where the address size is constrained to 32 bits.
25966 None of the above changes is visible to users.
25972 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25975 @item Command Language Interpreter (CLI interface)
25977 @item DECtalk Run-Time Library (DTK interface)
25979 @item Librarian utility routines (LBR interface)
25981 @item General Purpose Run-Time Library (LIB interface)
25983 @item Math Run-Time Library (MTH interface)
25985 @item National Character Set Run-Time Library (NCS interface)
25987 @item Compiled Code Support Run-Time Library (OTS interface)
25989 @item Parallel Processing Run-Time Library (PPL interface)
25991 @item Screen Management Run-Time Library (SMG interface)
25993 @item Sort Run-Time Library (SOR interface)
25995 @item String Run-Time Library (STR interface)
25997 @item STARLET System Library
26000 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
26002 @item X Windows Toolkit (XT interface)
26004 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
26008 GNAT provides implementations of these HP bindings in the @code{DECLIB}
26009 directory, on both the Alpha and I64 OpenVMS platforms.
26011 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
26013 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
26014 A pragma @code{Linker_Options} has been added to packages @code{Xm},
26015 @code{Xt}, and @code{X_Lib}
26016 causing the default X/Motif sharable image libraries to be linked in. This
26017 is done via options files named @file{xm.opt}, @file{xt.opt}, and
26018 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
26020 It may be necessary to edit these options files to update or correct the
26021 library names if, for example, the newer X/Motif bindings from
26022 @file{ADA$EXAMPLES}
26023 had been (previous to installing GNAT) copied and renamed to supersede the
26024 default @file{ADA$PREDEFINED} versions.
26027 * Shared Libraries and Options Files::
26028 * Interfaces to C::
26031 @node Shared Libraries and Options Files
26032 @subsection Shared Libraries and Options Files
26035 When using the HP Ada
26036 predefined X and Motif bindings, the linking with their sharable images is
26037 done automatically by @command{GNAT LINK}.
26038 When using other X and Motif bindings, you need
26039 to add the corresponding sharable images to the command line for
26040 @code{GNAT LINK}. When linking with shared libraries, or with
26041 @file{.OPT} files, you must
26042 also add them to the command line for @command{GNAT LINK}.
26044 A shared library to be used with GNAT is built in the same way as other
26045 libraries under VMS. The VMS Link command can be used in standard fashion.
26047 @node Interfaces to C
26048 @subsection Interfaces to C
26052 provides the following Ada types and operations:
26055 @item C types package (@code{C_TYPES})
26057 @item C strings (@code{C_TYPES.NULL_TERMINATED})
26059 @item Other_types (@code{SHORT_INT})
26063 Interfacing to C with GNAT, you can use the above approach
26064 described for HP Ada or the facilities of Annex B of
26065 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
26066 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
26067 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
26069 The @option{-gnatF} qualifier forces default and explicit
26070 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
26071 to be uppercased for compatibility with the default behavior
26072 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
26074 @node Main Program Definition
26075 @section Main Program Definition
26078 The following section discusses differences in the
26079 definition of main programs on HP Ada and GNAT.
26080 On HP Ada, main programs are defined to meet the
26081 following conditions:
26083 @item Procedure with no formal parameters (returns @code{0} upon
26086 @item Procedure with no formal parameters (returns @code{42} when
26087 an unhandled exception is raised)
26089 @item Function with no formal parameters whose returned value
26090 is of a discrete type
26092 @item Procedure with one @code{out} formal of a discrete type for
26093 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
26098 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
26099 a main function or main procedure returns a discrete
26100 value whose size is less than 64 bits (32 on VAX systems),
26101 the value is zero- or sign-extended as appropriate.
26102 On GNAT, main programs are defined as follows:
26104 @item Must be a non-generic, parameterless subprogram that
26105 is either a procedure or function returning an Ada
26106 @code{STANDARD.INTEGER} (the predefined type)
26108 @item Cannot be a generic subprogram or an instantiation of a
26112 @node Implementation-Defined Attributes
26113 @section Implementation-Defined Attributes
26116 GNAT provides all HP Ada implementation-defined
26119 @node Compiler and Run-Time Interfacing
26120 @section Compiler and Run-Time Interfacing
26123 HP Ada provides the following qualifiers to pass options to the linker
26126 @item @option{/WAIT} and @option{/SUBMIT}
26128 @item @option{/COMMAND}
26130 @item @option{/@r{[}NO@r{]}MAP}
26132 @item @option{/OUTPUT=@var{file-spec}}
26134 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
26138 To pass options to the linker, GNAT provides the following
26142 @item @option{/EXECUTABLE=@var{exec-name}}
26144 @item @option{/VERBOSE}
26146 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
26150 For more information on these switches, see
26151 @ref{Switches for gnatlink}.
26152 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
26153 to control optimization. HP Ada also supplies the
26156 @item @code{OPTIMIZE}
26158 @item @code{INLINE}
26160 @item @code{INLINE_GENERIC}
26162 @item @code{SUPPRESS_ALL}
26164 @item @code{PASSIVE}
26168 In GNAT, optimization is controlled strictly by command
26169 line parameters, as described in the corresponding section of this guide.
26170 The HP pragmas for control of optimization are
26171 recognized but ignored.
26173 Note that in GNAT, the default is optimization off, whereas in HP Ada
26174 the default is that optimization is turned on.
26176 @node Program Compilation and Library Management
26177 @section Program Compilation and Library Management
26180 HP Ada and GNAT provide a comparable set of commands to
26181 build programs. HP Ada also provides a program library,
26182 which is a concept that does not exist on GNAT. Instead,
26183 GNAT provides directories of sources that are compiled as
26186 The following table summarizes
26187 the HP Ada commands and provides
26188 equivalent GNAT commands. In this table, some GNAT
26189 equivalents reflect the fact that GNAT does not use the
26190 concept of a program library. Instead, it uses a model
26191 in which collections of source and object files are used
26192 in a manner consistent with other languages like C and
26193 Fortran. Therefore, standard system file commands are used
26194 to manipulate these elements. Those GNAT commands are marked with
26196 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
26199 @multitable @columnfractions .35 .65
26201 @item @emph{HP Ada Command}
26202 @tab @emph{GNAT Equivalent / Description}
26204 @item @command{ADA}
26205 @tab @command{GNAT COMPILE}@*
26206 Invokes the compiler to compile one or more Ada source files.
26208 @item @command{ACS ATTACH}@*
26209 @tab [No equivalent]@*
26210 Switches control of terminal from current process running the program
26213 @item @command{ACS CHECK}
26214 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
26215 Forms the execution closure of one
26216 or more compiled units and checks completeness and currency.
26218 @item @command{ACS COMPILE}
26219 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26220 Forms the execution closure of one or
26221 more specified units, checks completeness and currency,
26222 identifies units that have revised source files, compiles same,
26223 and recompiles units that are or will become obsolete.
26224 Also completes incomplete generic instantiations.
26226 @item @command{ACS COPY FOREIGN}
26228 Copies a foreign object file into the program library as a
26231 @item @command{ACS COPY UNIT}
26233 Copies a compiled unit from one program library to another.
26235 @item @command{ACS CREATE LIBRARY}
26236 @tab Create /directory (*)@*
26237 Creates a program library.
26239 @item @command{ACS CREATE SUBLIBRARY}
26240 @tab Create /directory (*)@*
26241 Creates a program sublibrary.
26243 @item @command{ACS DELETE LIBRARY}
26245 Deletes a program library and its contents.
26247 @item @command{ACS DELETE SUBLIBRARY}
26249 Deletes a program sublibrary and its contents.
26251 @item @command{ACS DELETE UNIT}
26252 @tab Delete file (*)@*
26253 On OpenVMS systems, deletes one or more compiled units from
26254 the current program library.
26256 @item @command{ACS DIRECTORY}
26257 @tab Directory (*)@*
26258 On OpenVMS systems, lists units contained in the current
26261 @item @command{ACS ENTER FOREIGN}
26263 Allows the import of a foreign body as an Ada library
26264 spec and enters a reference to a pointer.
26266 @item @command{ACS ENTER UNIT}
26268 Enters a reference (pointer) from the current program library to
26269 a unit compiled into another program library.
26271 @item @command{ACS EXIT}
26272 @tab [No equivalent]@*
26273 Exits from the program library manager.
26275 @item @command{ACS EXPORT}
26277 Creates an object file that contains system-specific object code
26278 for one or more units. With GNAT, object files can simply be copied
26279 into the desired directory.
26281 @item @command{ACS EXTRACT SOURCE}
26283 Allows access to the copied source file for each Ada compilation unit
26285 @item @command{ACS HELP}
26286 @tab @command{HELP GNAT}@*
26287 Provides online help.
26289 @item @command{ACS LINK}
26290 @tab @command{GNAT LINK}@*
26291 Links an object file containing Ada units into an executable file.
26293 @item @command{ACS LOAD}
26295 Loads (partially compiles) Ada units into the program library.
26296 Allows loading a program from a collection of files into a library
26297 without knowing the relationship among units.
26299 @item @command{ACS MERGE}
26301 Merges into the current program library, one or more units from
26302 another library where they were modified.
26304 @item @command{ACS RECOMPILE}
26305 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26306 Recompiles from external or copied source files any obsolete
26307 unit in the closure. Also, completes any incomplete generic
26310 @item @command{ACS REENTER}
26311 @tab @command{GNAT MAKE}@*
26312 Reenters current references to units compiled after last entered
26313 with the @command{ACS ENTER UNIT} command.
26315 @item @command{ACS SET LIBRARY}
26316 @tab Set default (*)@*
26317 Defines a program library to be the compilation context as well
26318 as the target library for compiler output and commands in general.
26320 @item @command{ACS SET PRAGMA}
26321 @tab Edit @file{gnat.adc} (*)@*
26322 Redefines specified values of the library characteristics
26323 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
26324 and @code{Float_Representation}.
26326 @item @command{ACS SET SOURCE}
26327 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
26328 Defines the source file search list for the @command{ACS COMPILE} command.
26330 @item @command{ACS SHOW LIBRARY}
26331 @tab Directory (*)@*
26332 Lists information about one or more program libraries.
26334 @item @command{ACS SHOW PROGRAM}
26335 @tab [No equivalent]@*
26336 Lists information about the execution closure of one or
26337 more units in the program library.
26339 @item @command{ACS SHOW SOURCE}
26340 @tab Show logical @code{ADA_INCLUDE_PATH}@*
26341 Shows the source file search used when compiling units.
26343 @item @command{ACS SHOW VERSION}
26344 @tab Compile with @option{VERBOSE} option
26345 Displays the version number of the compiler and program library
26348 @item @command{ACS SPAWN}
26349 @tab [No equivalent]@*
26350 Creates a subprocess of the current process (same as @command{DCL SPAWN}
26353 @item @command{ACS VERIFY}
26354 @tab [No equivalent]@*
26355 Performs a series of consistency checks on a program library to
26356 determine whether the library structure and library files are in
26363 @section Input-Output
26366 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
26367 Management Services (RMS) to perform operations on
26371 HP Ada and GNAT predefine an identical set of input-
26372 output packages. To make the use of the
26373 generic @code{TEXT_IO} operations more convenient, HP Ada
26374 provides predefined library packages that instantiate the
26375 integer and floating-point operations for the predefined
26376 integer and floating-point types as shown in the following table.
26378 @multitable @columnfractions .45 .55
26379 @item @emph{Package Name} @tab Instantiation
26381 @item @code{INTEGER_TEXT_IO}
26382 @tab @code{INTEGER_IO(INTEGER)}
26384 @item @code{SHORT_INTEGER_TEXT_IO}
26385 @tab @code{INTEGER_IO(SHORT_INTEGER)}
26387 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
26388 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
26390 @item @code{FLOAT_TEXT_IO}
26391 @tab @code{FLOAT_IO(FLOAT)}
26393 @item @code{LONG_FLOAT_TEXT_IO}
26394 @tab @code{FLOAT_IO(LONG_FLOAT)}
26398 The HP Ada predefined packages and their operations
26399 are implemented using OpenVMS Alpha files and input-output
26400 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
26401 Familiarity with the following is recommended:
26403 @item RMS file organizations and access methods
26405 @item OpenVMS file specifications and directories
26407 @item OpenVMS File Definition Language (FDL)
26411 GNAT provides I/O facilities that are completely
26412 compatible with HP Ada. The distribution includes the
26413 standard HP Ada versions of all I/O packages, operating
26414 in a manner compatible with HP Ada. In particular, the
26415 following packages are by default the HP Ada (Ada 83)
26416 versions of these packages rather than the renamings
26417 suggested in Annex J of the Ada Reference Manual:
26419 @item @code{TEXT_IO}
26421 @item @code{SEQUENTIAL_IO}
26423 @item @code{DIRECT_IO}
26427 The use of the standard child package syntax (for
26428 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
26430 GNAT provides HP-compatible predefined instantiations
26431 of the @code{TEXT_IO} packages, and also
26432 provides the standard predefined instantiations required
26433 by the @cite{Ada Reference Manual}.
26435 For further information on how GNAT interfaces to the file
26436 system or how I/O is implemented in programs written in
26437 mixed languages, see @ref{Implementation of the Standard I/O,,,
26438 gnat_rm, GNAT Reference Manual}.
26439 This chapter covers the following:
26441 @item Standard I/O packages
26443 @item @code{FORM} strings
26445 @item @code{ADA.DIRECT_IO}
26447 @item @code{ADA.SEQUENTIAL_IO}
26449 @item @code{ADA.TEXT_IO}
26451 @item Stream pointer positioning
26453 @item Reading and writing non-regular files
26455 @item @code{GET_IMMEDIATE}
26457 @item Treating @code{TEXT_IO} files as streams
26464 @node Implementation Limits
26465 @section Implementation Limits
26468 The following table lists implementation limits for HP Ada
26470 @multitable @columnfractions .60 .20 .20
26472 @item @emph{Compilation Parameter}
26477 @item In a subprogram or entry declaration, maximum number of
26478 formal parameters that are of an unconstrained record type
26483 @item Maximum identifier length (number of characters)
26488 @item Maximum number of characters in a source line
26493 @item Maximum collection size (number of bytes)
26498 @item Maximum number of discriminants for a record type
26503 @item Maximum number of formal parameters in an entry or
26504 subprogram declaration
26509 @item Maximum number of dimensions in an array type
26514 @item Maximum number of library units and subunits in a compilation.
26519 @item Maximum number of library units and subunits in an execution.
26524 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26525 or @code{PSECT_OBJECT}
26530 @item Maximum number of enumeration literals in an enumeration type
26536 @item Maximum number of lines in a source file
26541 @item Maximum number of bits in any object
26546 @item Maximum size of the static portion of a stack frame (approximate)
26551 @node Tools and Utilities
26552 @section Tools and Utilities
26555 The following table lists some of the OpenVMS development tools
26556 available for HP Ada, and the corresponding tools for
26557 use with @value{EDITION} on Alpha and I64 platforms.
26558 Aside from the debugger, all the OpenVMS tools identified are part
26559 of the DECset package.
26562 @c Specify table in TeX since Texinfo does a poor job
26566 \settabs\+Language-Sensitive Editor\quad
26567 &Product with HP Ada\quad
26570 &\it Product with HP Ada
26571 & \it Product with GNAT Pro\cr
26573 \+Code Management System
26577 \+Language-Sensitive Editor
26579 & emacs or HP LSE (Alpha)\cr
26589 & OpenVMS Debug (I64)\cr
26591 \+Source Code Analyzer /
26608 \+Coverage Analyzer
26612 \+Module Management
26614 & Not applicable\cr
26624 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26625 @c the TeX version above for the printed version
26627 @c @multitable @columnfractions .3 .4 .4
26628 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26630 @tab @i{Tool with HP Ada}
26631 @tab @i{Tool with @value{EDITION}}
26632 @item Code Management@*System
26635 @item Language-Sensitive@*Editor
26637 @tab emacs or HP LSE (Alpha)
26646 @tab OpenVMS Debug (I64)
26647 @item Source Code Analyzer /@*Cross Referencer
26651 @tab HP Digital Test@*Manager (DTM)
26653 @item Performance and@*Coverage Analyzer
26656 @item Module Management@*System
26658 @tab Not applicable
26665 @c **************************************
26666 @node Platform-Specific Information for the Run-Time Libraries
26667 @appendix Platform-Specific Information for the Run-Time Libraries
26668 @cindex Tasking and threads libraries
26669 @cindex Threads libraries and tasking
26670 @cindex Run-time libraries (platform-specific information)
26673 The GNAT run-time implementation may vary with respect to both the
26674 underlying threads library and the exception handling scheme.
26675 For threads support, one or more of the following are supplied:
26677 @item @b{native threads library}, a binding to the thread package from
26678 the underlying operating system
26680 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26681 POSIX thread package
26685 For exception handling, either or both of two models are supplied:
26687 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26688 Most programs should experience a substantial speed improvement by
26689 being compiled with a ZCX run-time.
26690 This is especially true for
26691 tasking applications or applications with many exception handlers.}
26692 @cindex Zero-Cost Exceptions
26693 @cindex ZCX (Zero-Cost Exceptions)
26694 which uses binder-generated tables that
26695 are interrogated at run time to locate a handler
26697 @item @b{setjmp / longjmp} (``SJLJ''),
26698 @cindex setjmp/longjmp Exception Model
26699 @cindex SJLJ (setjmp/longjmp Exception Model)
26700 which uses dynamically-set data to establish
26701 the set of handlers
26705 This appendix summarizes which combinations of threads and exception support
26706 are supplied on various GNAT platforms.
26707 It then shows how to select a particular library either
26708 permanently or temporarily,
26709 explains the properties of (and tradeoffs among) the various threads
26710 libraries, and provides some additional
26711 information about several specific platforms.
26714 * Summary of Run-Time Configurations::
26715 * Specifying a Run-Time Library::
26716 * Choosing the Scheduling Policy::
26717 * Solaris-Specific Considerations::
26718 * Linux-Specific Considerations::
26719 * AIX-Specific Considerations::
26720 * Irix-Specific Considerations::
26721 * RTX-Specific Considerations::
26724 @node Summary of Run-Time Configurations
26725 @section Summary of Run-Time Configurations
26727 @multitable @columnfractions .30 .70
26728 @item @b{alpha-openvms}
26729 @item @code{@ @ }@i{rts-native (default)}
26730 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26731 @item @code{@ @ @ @ }Exceptions @tab ZCX
26733 @item @b{alpha-tru64}
26734 @item @code{@ @ }@i{rts-native (default)}
26735 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26736 @item @code{@ @ @ @ }Exceptions @tab ZCX
26738 @item @code{@ @ }@i{rts-sjlj}
26739 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26740 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26742 @item @b{ia64-hp_linux}
26743 @item @code{@ @ }@i{rts-native (default)}
26744 @item @code{@ @ @ @ }Tasking @tab pthread library
26745 @item @code{@ @ @ @ }Exceptions @tab ZCX
26747 @item @b{ia64-hpux}
26748 @item @code{@ @ }@i{rts-native (default)}
26749 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26750 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26752 @item @b{ia64-openvms}
26753 @item @code{@ @ }@i{rts-native (default)}
26754 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26755 @item @code{@ @ @ @ }Exceptions @tab ZCX
26757 @item @b{ia64-sgi_linux}
26758 @item @code{@ @ }@i{rts-native (default)}
26759 @item @code{@ @ @ @ }Tasking @tab pthread library
26760 @item @code{@ @ @ @ }Exceptions @tab ZCX
26762 @item @b{mips-irix}
26763 @item @code{@ @ }@i{rts-native (default)}
26764 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26765 @item @code{@ @ @ @ }Exceptions @tab ZCX
26768 @item @code{@ @ }@i{rts-native (default)}
26769 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26770 @item @code{@ @ @ @ }Exceptions @tab ZCX
26772 @item @code{@ @ }@i{rts-sjlj}
26773 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26774 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26777 @item @code{@ @ }@i{rts-native (default)}
26778 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26779 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26781 @item @b{ppc-darwin}
26782 @item @code{@ @ }@i{rts-native (default)}
26783 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26784 @item @code{@ @ @ @ }Exceptions @tab ZCX
26786 @item @b{sparc-solaris} @tab
26787 @item @code{@ @ }@i{rts-native (default)}
26788 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26789 @item @code{@ @ @ @ }Exceptions @tab ZCX
26791 @item @code{@ @ }@i{rts-pthread}
26792 @item @code{@ @ @ @ }Tasking @tab pthread library
26793 @item @code{@ @ @ @ }Exceptions @tab ZCX
26795 @item @code{@ @ }@i{rts-sjlj}
26796 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26797 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26799 @item @b{sparc64-solaris} @tab
26800 @item @code{@ @ }@i{rts-native (default)}
26801 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26802 @item @code{@ @ @ @ }Exceptions @tab ZCX
26804 @item @b{x86-linux}
26805 @item @code{@ @ }@i{rts-native (default)}
26806 @item @code{@ @ @ @ }Tasking @tab pthread library
26807 @item @code{@ @ @ @ }Exceptions @tab ZCX
26809 @item @code{@ @ }@i{rts-sjlj}
26810 @item @code{@ @ @ @ }Tasking @tab pthread library
26811 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26814 @item @code{@ @ }@i{rts-native (default)}
26815 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26816 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26818 @item @b{x86-solaris}
26819 @item @code{@ @ }@i{rts-native (default)}
26820 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26821 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26823 @item @b{x86-windows}
26824 @item @code{@ @ }@i{rts-native (default)}
26825 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26826 @item @code{@ @ @ @ }Exceptions @tab ZCX
26828 @item @code{@ @ }@i{rts-sjlj (default)}
26829 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26830 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26832 @item @b{x86-windows-rtx}
26833 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26834 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26835 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26837 @item @code{@ @ }@i{rts-rtx-w32}
26838 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26839 @item @code{@ @ @ @ }Exceptions @tab ZCX
26841 @item @b{x86_64-linux}
26842 @item @code{@ @ }@i{rts-native (default)}
26843 @item @code{@ @ @ @ }Tasking @tab pthread library
26844 @item @code{@ @ @ @ }Exceptions @tab ZCX
26846 @item @code{@ @ }@i{rts-sjlj}
26847 @item @code{@ @ @ @ }Tasking @tab pthread library
26848 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26852 @node Specifying a Run-Time Library
26853 @section Specifying a Run-Time Library
26856 The @file{adainclude} subdirectory containing the sources of the GNAT
26857 run-time library, and the @file{adalib} subdirectory containing the
26858 @file{ALI} files and the static and/or shared GNAT library, are located
26859 in the gcc target-dependent area:
26862 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26866 As indicated above, on some platforms several run-time libraries are supplied.
26867 These libraries are installed in the target dependent area and
26868 contain a complete source and binary subdirectory. The detailed description
26869 below explains the differences between the different libraries in terms of
26870 their thread support.
26872 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26873 This default run time is selected by the means of soft links.
26874 For example on x86-linux:
26880 +--- adainclude----------+
26882 +--- adalib-----------+ |
26884 +--- rts-native | |
26886 | +--- adainclude <---+
26888 | +--- adalib <----+
26899 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26900 these soft links can be modified with the following commands:
26904 $ rm -f adainclude adalib
26905 $ ln -s rts-sjlj/adainclude adainclude
26906 $ ln -s rts-sjlj/adalib adalib
26910 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26911 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26912 @file{$target/ada_object_path}.
26914 Selecting another run-time library temporarily can be
26915 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26916 @cindex @option{--RTS} option
26918 @node Choosing the Scheduling Policy
26919 @section Choosing the Scheduling Policy
26922 When using a POSIX threads implementation, you have a choice of several
26923 scheduling policies: @code{SCHED_FIFO},
26924 @cindex @code{SCHED_FIFO} scheduling policy
26926 @cindex @code{SCHED_RR} scheduling policy
26927 and @code{SCHED_OTHER}.
26928 @cindex @code{SCHED_OTHER} scheduling policy
26929 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26930 or @code{SCHED_RR} requires special (e.g., root) privileges.
26932 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26934 @cindex @code{SCHED_FIFO} scheduling policy
26935 you can use one of the following:
26939 @code{pragma Time_Slice (0.0)}
26940 @cindex pragma Time_Slice
26942 the corresponding binder option @option{-T0}
26943 @cindex @option{-T0} option
26945 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26946 @cindex pragma Task_Dispatching_Policy
26950 To specify @code{SCHED_RR},
26951 @cindex @code{SCHED_RR} scheduling policy
26952 you should use @code{pragma Time_Slice} with a
26953 value greater than @code{0.0}, or else use the corresponding @option{-T}
26956 @node Solaris-Specific Considerations
26957 @section Solaris-Specific Considerations
26958 @cindex Solaris Sparc threads libraries
26961 This section addresses some topics related to the various threads libraries
26965 * Solaris Threads Issues::
26968 @node Solaris Threads Issues
26969 @subsection Solaris Threads Issues
26972 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26973 library based on POSIX threads --- @emph{rts-pthread}.
26974 @cindex rts-pthread threads library
26975 This run-time library has the advantage of being mostly shared across all
26976 POSIX-compliant thread implementations, and it also provides under
26977 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26978 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26979 and @code{PTHREAD_PRIO_PROTECT}
26980 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26981 semantics that can be selected using the predefined pragma
26982 @code{Locking_Policy}
26983 @cindex pragma Locking_Policy (under rts-pthread)
26985 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26986 @cindex @code{Inheritance_Locking} (under rts-pthread)
26987 @cindex @code{Ceiling_Locking} (under rts-pthread)
26989 As explained above, the native run-time library is based on the Solaris thread
26990 library (@code{libthread}) and is the default library.
26992 When the Solaris threads library is used (this is the default), programs
26993 compiled with GNAT can automatically take advantage of
26994 and can thus execute on multiple processors.
26995 The user can alternatively specify a processor on which the program should run
26996 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26998 setting the environment variable @env{GNAT_PROCESSOR}
26999 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
27000 to one of the following:
27004 Use the default configuration (run the program on all
27005 available processors) - this is the same as having @code{GNAT_PROCESSOR}
27009 Let the run-time implementation choose one processor and run the program on
27012 @item 0 .. Last_Proc
27013 Run the program on the specified processor.
27014 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
27015 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
27018 @node Linux-Specific Considerations
27019 @section Linux-Specific Considerations
27020 @cindex Linux threads libraries
27023 On GNU/Linux without NPTL support (usually system with GNU C Library
27024 older than 2.3), the signal model is not POSIX compliant, which means
27025 that to send a signal to the process, you need to send the signal to all
27026 threads, e.g.@: by using @code{killpg()}.
27028 @node AIX-Specific Considerations
27029 @section AIX-Specific Considerations
27030 @cindex AIX resolver library
27033 On AIX, the resolver library initializes some internal structure on
27034 the first call to @code{get*by*} functions, which are used to implement
27035 @code{GNAT.Sockets.Get_Host_By_Name} and
27036 @code{GNAT.Sockets.Get_Host_By_Address}.
27037 If such initialization occurs within an Ada task, and the stack size for
27038 the task is the default size, a stack overflow may occur.
27040 To avoid this overflow, the user should either ensure that the first call
27041 to @code{GNAT.Sockets.Get_Host_By_Name} or
27042 @code{GNAT.Sockets.Get_Host_By_Addrss}
27043 occurs in the environment task, or use @code{pragma Storage_Size} to
27044 specify a sufficiently large size for the stack of the task that contains
27047 @node Irix-Specific Considerations
27048 @section Irix-Specific Considerations
27049 @cindex Irix libraries
27052 The GCC support libraries coming with the Irix compiler have moved to
27053 their canonical place with respect to the general Irix ABI related
27054 conventions. Running applications built with the default shared GNAT
27055 run-time now requires the LD_LIBRARY_PATH environment variable to
27056 include this location. A possible way to achieve this is to issue the
27057 following command line on a bash prompt:
27061 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
27065 @node RTX-Specific Considerations
27066 @section RTX-Specific Considerations
27067 @cindex RTX libraries
27070 The Real-time Extension (RTX) to Windows is based on the Windows Win32
27071 API. Applications can be built to work in two different modes:
27075 Windows executables that run in Ring 3 to utilize memory protection
27076 (@emph{rts-rtx-w32}).
27079 Real-time subsystem (RTSS) executables that run in Ring 0, where
27080 performance can be optimized with RTSS applications taking precedent
27081 over all Windows applications (@emph{rts-rtx-rtss}).
27085 @c *******************************
27086 @node Example of Binder Output File
27087 @appendix Example of Binder Output File
27090 This Appendix displays the source code for @command{gnatbind}'s output
27091 file generated for a simple ``Hello World'' program.
27092 Comments have been added for clarification purposes.
27094 @smallexample @c adanocomment
27098 -- The package is called Ada_Main unless this name is actually used
27099 -- as a unit name in the partition, in which case some other unique
27103 package ada_main is
27105 Elab_Final_Code : Integer;
27106 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
27108 -- The main program saves the parameters (argument count,
27109 -- argument values, environment pointer) in global variables
27110 -- for later access by other units including
27111 -- Ada.Command_Line.
27113 gnat_argc : Integer;
27114 gnat_argv : System.Address;
27115 gnat_envp : System.Address;
27117 -- The actual variables are stored in a library routine. This
27118 -- is useful for some shared library situations, where there
27119 -- are problems if variables are not in the library.
27121 pragma Import (C, gnat_argc);
27122 pragma Import (C, gnat_argv);
27123 pragma Import (C, gnat_envp);
27125 -- The exit status is similarly an external location
27127 gnat_exit_status : Integer;
27128 pragma Import (C, gnat_exit_status);
27130 GNAT_Version : constant String :=
27131 "GNAT Version: 6.0.0w (20061115)";
27132 pragma Export (C, GNAT_Version, "__gnat_version");
27134 -- This is the generated adafinal routine that performs
27135 -- finalization at the end of execution. In the case where
27136 -- Ada is the main program, this main program makes a call
27137 -- to adafinal at program termination.
27139 procedure adafinal;
27140 pragma Export (C, adafinal, "adafinal");
27142 -- This is the generated adainit routine that performs
27143 -- initialization at the start of execution. In the case
27144 -- where Ada is the main program, this main program makes
27145 -- a call to adainit at program startup.
27148 pragma Export (C, adainit, "adainit");
27150 -- This routine is called at the start of execution. It is
27151 -- a dummy routine that is used by the debugger to breakpoint
27152 -- at the start of execution.
27154 procedure Break_Start;
27155 pragma Import (C, Break_Start, "__gnat_break_start");
27157 -- This is the actual generated main program (it would be
27158 -- suppressed if the no main program switch were used). As
27159 -- required by standard system conventions, this program has
27160 -- the external name main.
27164 argv : System.Address;
27165 envp : System.Address)
27167 pragma Export (C, main, "main");
27169 -- The following set of constants give the version
27170 -- identification values for every unit in the bound
27171 -- partition. This identification is computed from all
27172 -- dependent semantic units, and corresponds to the
27173 -- string that would be returned by use of the
27174 -- Body_Version or Version attributes.
27176 type Version_32 is mod 2 ** 32;
27177 u00001 : constant Version_32 := 16#7880BEB3#;
27178 u00002 : constant Version_32 := 16#0D24CBD0#;
27179 u00003 : constant Version_32 := 16#3283DBEB#;
27180 u00004 : constant Version_32 := 16#2359F9ED#;
27181 u00005 : constant Version_32 := 16#664FB847#;
27182 u00006 : constant Version_32 := 16#68E803DF#;
27183 u00007 : constant Version_32 := 16#5572E604#;
27184 u00008 : constant Version_32 := 16#46B173D8#;
27185 u00009 : constant Version_32 := 16#156A40CF#;
27186 u00010 : constant Version_32 := 16#033DABE0#;
27187 u00011 : constant Version_32 := 16#6AB38FEA#;
27188 u00012 : constant Version_32 := 16#22B6217D#;
27189 u00013 : constant Version_32 := 16#68A22947#;
27190 u00014 : constant Version_32 := 16#18CC4A56#;
27191 u00015 : constant Version_32 := 16#08258E1B#;
27192 u00016 : constant Version_32 := 16#367D5222#;
27193 u00017 : constant Version_32 := 16#20C9ECA4#;
27194 u00018 : constant Version_32 := 16#50D32CB6#;
27195 u00019 : constant Version_32 := 16#39A8BB77#;
27196 u00020 : constant Version_32 := 16#5CF8FA2B#;
27197 u00021 : constant Version_32 := 16#2F1EB794#;
27198 u00022 : constant Version_32 := 16#31AB6444#;
27199 u00023 : constant Version_32 := 16#1574B6E9#;
27200 u00024 : constant Version_32 := 16#5109C189#;
27201 u00025 : constant Version_32 := 16#56D770CD#;
27202 u00026 : constant Version_32 := 16#02F9DE3D#;
27203 u00027 : constant Version_32 := 16#08AB6B2C#;
27204 u00028 : constant Version_32 := 16#3FA37670#;
27205 u00029 : constant Version_32 := 16#476457A0#;
27206 u00030 : constant Version_32 := 16#731E1B6E#;
27207 u00031 : constant Version_32 := 16#23C2E789#;
27208 u00032 : constant Version_32 := 16#0F1BD6A1#;
27209 u00033 : constant Version_32 := 16#7C25DE96#;
27210 u00034 : constant Version_32 := 16#39ADFFA2#;
27211 u00035 : constant Version_32 := 16#571DE3E7#;
27212 u00036 : constant Version_32 := 16#5EB646AB#;
27213 u00037 : constant Version_32 := 16#4249379B#;
27214 u00038 : constant Version_32 := 16#0357E00A#;
27215 u00039 : constant Version_32 := 16#3784FB72#;
27216 u00040 : constant Version_32 := 16#2E723019#;
27217 u00041 : constant Version_32 := 16#623358EA#;
27218 u00042 : constant Version_32 := 16#107F9465#;
27219 u00043 : constant Version_32 := 16#6843F68A#;
27220 u00044 : constant Version_32 := 16#63305874#;
27221 u00045 : constant Version_32 := 16#31E56CE1#;
27222 u00046 : constant Version_32 := 16#02917970#;
27223 u00047 : constant Version_32 := 16#6CCBA70E#;
27224 u00048 : constant Version_32 := 16#41CD4204#;
27225 u00049 : constant Version_32 := 16#572E3F58#;
27226 u00050 : constant Version_32 := 16#20729FF5#;
27227 u00051 : constant Version_32 := 16#1D4F93E8#;
27228 u00052 : constant Version_32 := 16#30B2EC3D#;
27229 u00053 : constant Version_32 := 16#34054F96#;
27230 u00054 : constant Version_32 := 16#5A199860#;
27231 u00055 : constant Version_32 := 16#0E7F912B#;
27232 u00056 : constant Version_32 := 16#5760634A#;
27233 u00057 : constant Version_32 := 16#5D851835#;
27235 -- The following Export pragmas export the version numbers
27236 -- with symbolic names ending in B (for body) or S
27237 -- (for spec) so that they can be located in a link. The
27238 -- information provided here is sufficient to track down
27239 -- the exact versions of units used in a given build.
27241 pragma Export (C, u00001, "helloB");
27242 pragma Export (C, u00002, "system__standard_libraryB");
27243 pragma Export (C, u00003, "system__standard_libraryS");
27244 pragma Export (C, u00004, "adaS");
27245 pragma Export (C, u00005, "ada__text_ioB");
27246 pragma Export (C, u00006, "ada__text_ioS");
27247 pragma Export (C, u00007, "ada__exceptionsB");
27248 pragma Export (C, u00008, "ada__exceptionsS");
27249 pragma Export (C, u00009, "gnatS");
27250 pragma Export (C, u00010, "gnat__heap_sort_aB");
27251 pragma Export (C, u00011, "gnat__heap_sort_aS");
27252 pragma Export (C, u00012, "systemS");
27253 pragma Export (C, u00013, "system__exception_tableB");
27254 pragma Export (C, u00014, "system__exception_tableS");
27255 pragma Export (C, u00015, "gnat__htableB");
27256 pragma Export (C, u00016, "gnat__htableS");
27257 pragma Export (C, u00017, "system__exceptionsS");
27258 pragma Export (C, u00018, "system__machine_state_operationsB");
27259 pragma Export (C, u00019, "system__machine_state_operationsS");
27260 pragma Export (C, u00020, "system__machine_codeS");
27261 pragma Export (C, u00021, "system__storage_elementsB");
27262 pragma Export (C, u00022, "system__storage_elementsS");
27263 pragma Export (C, u00023, "system__secondary_stackB");
27264 pragma Export (C, u00024, "system__secondary_stackS");
27265 pragma Export (C, u00025, "system__parametersB");
27266 pragma Export (C, u00026, "system__parametersS");
27267 pragma Export (C, u00027, "system__soft_linksB");
27268 pragma Export (C, u00028, "system__soft_linksS");
27269 pragma Export (C, u00029, "system__stack_checkingB");
27270 pragma Export (C, u00030, "system__stack_checkingS");
27271 pragma Export (C, u00031, "system__tracebackB");
27272 pragma Export (C, u00032, "system__tracebackS");
27273 pragma Export (C, u00033, "ada__streamsS");
27274 pragma Export (C, u00034, "ada__tagsB");
27275 pragma Export (C, u00035, "ada__tagsS");
27276 pragma Export (C, u00036, "system__string_opsB");
27277 pragma Export (C, u00037, "system__string_opsS");
27278 pragma Export (C, u00038, "interfacesS");
27279 pragma Export (C, u00039, "interfaces__c_streamsB");
27280 pragma Export (C, u00040, "interfaces__c_streamsS");
27281 pragma Export (C, u00041, "system__file_ioB");
27282 pragma Export (C, u00042, "system__file_ioS");
27283 pragma Export (C, u00043, "ada__finalizationB");
27284 pragma Export (C, u00044, "ada__finalizationS");
27285 pragma Export (C, u00045, "system__finalization_rootB");
27286 pragma Export (C, u00046, "system__finalization_rootS");
27287 pragma Export (C, u00047, "system__finalization_implementationB");
27288 pragma Export (C, u00048, "system__finalization_implementationS");
27289 pragma Export (C, u00049, "system__string_ops_concat_3B");
27290 pragma Export (C, u00050, "system__string_ops_concat_3S");
27291 pragma Export (C, u00051, "system__stream_attributesB");
27292 pragma Export (C, u00052, "system__stream_attributesS");
27293 pragma Export (C, u00053, "ada__io_exceptionsS");
27294 pragma Export (C, u00054, "system__unsigned_typesS");
27295 pragma Export (C, u00055, "system__file_control_blockS");
27296 pragma Export (C, u00056, "ada__finalization__list_controllerB");
27297 pragma Export (C, u00057, "ada__finalization__list_controllerS");
27299 -- BEGIN ELABORATION ORDER
27302 -- gnat.heap_sort_a (spec)
27303 -- gnat.heap_sort_a (body)
27304 -- gnat.htable (spec)
27305 -- gnat.htable (body)
27306 -- interfaces (spec)
27308 -- system.machine_code (spec)
27309 -- system.parameters (spec)
27310 -- system.parameters (body)
27311 -- interfaces.c_streams (spec)
27312 -- interfaces.c_streams (body)
27313 -- system.standard_library (spec)
27314 -- ada.exceptions (spec)
27315 -- system.exception_table (spec)
27316 -- system.exception_table (body)
27317 -- ada.io_exceptions (spec)
27318 -- system.exceptions (spec)
27319 -- system.storage_elements (spec)
27320 -- system.storage_elements (body)
27321 -- system.machine_state_operations (spec)
27322 -- system.machine_state_operations (body)
27323 -- system.secondary_stack (spec)
27324 -- system.stack_checking (spec)
27325 -- system.soft_links (spec)
27326 -- system.soft_links (body)
27327 -- system.stack_checking (body)
27328 -- system.secondary_stack (body)
27329 -- system.standard_library (body)
27330 -- system.string_ops (spec)
27331 -- system.string_ops (body)
27334 -- ada.streams (spec)
27335 -- system.finalization_root (spec)
27336 -- system.finalization_root (body)
27337 -- system.string_ops_concat_3 (spec)
27338 -- system.string_ops_concat_3 (body)
27339 -- system.traceback (spec)
27340 -- system.traceback (body)
27341 -- ada.exceptions (body)
27342 -- system.unsigned_types (spec)
27343 -- system.stream_attributes (spec)
27344 -- system.stream_attributes (body)
27345 -- system.finalization_implementation (spec)
27346 -- system.finalization_implementation (body)
27347 -- ada.finalization (spec)
27348 -- ada.finalization (body)
27349 -- ada.finalization.list_controller (spec)
27350 -- ada.finalization.list_controller (body)
27351 -- system.file_control_block (spec)
27352 -- system.file_io (spec)
27353 -- system.file_io (body)
27354 -- ada.text_io (spec)
27355 -- ada.text_io (body)
27357 -- END ELABORATION ORDER
27361 -- The following source file name pragmas allow the generated file
27362 -- names to be unique for different main programs. They are needed
27363 -- since the package name will always be Ada_Main.
27365 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
27366 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
27368 -- Generated package body for Ada_Main starts here
27370 package body ada_main is
27372 -- The actual finalization is performed by calling the
27373 -- library routine in System.Standard_Library.Adafinal
27375 procedure Do_Finalize;
27376 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
27383 procedure adainit is
27385 -- These booleans are set to True once the associated unit has
27386 -- been elaborated. It is also used to avoid elaborating the
27387 -- same unit twice.
27390 pragma Import (Ada, E040, "interfaces__c_streams_E");
27393 pragma Import (Ada, E008, "ada__exceptions_E");
27396 pragma Import (Ada, E014, "system__exception_table_E");
27399 pragma Import (Ada, E053, "ada__io_exceptions_E");
27402 pragma Import (Ada, E017, "system__exceptions_E");
27405 pragma Import (Ada, E024, "system__secondary_stack_E");
27408 pragma Import (Ada, E030, "system__stack_checking_E");
27411 pragma Import (Ada, E028, "system__soft_links_E");
27414 pragma Import (Ada, E035, "ada__tags_E");
27417 pragma Import (Ada, E033, "ada__streams_E");
27420 pragma Import (Ada, E046, "system__finalization_root_E");
27423 pragma Import (Ada, E048, "system__finalization_implementation_E");
27426 pragma Import (Ada, E044, "ada__finalization_E");
27429 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
27432 pragma Import (Ada, E055, "system__file_control_block_E");
27435 pragma Import (Ada, E042, "system__file_io_E");
27438 pragma Import (Ada, E006, "ada__text_io_E");
27440 -- Set_Globals is a library routine that stores away the
27441 -- value of the indicated set of global values in global
27442 -- variables within the library.
27444 procedure Set_Globals
27445 (Main_Priority : Integer;
27446 Time_Slice_Value : Integer;
27447 WC_Encoding : Character;
27448 Locking_Policy : Character;
27449 Queuing_Policy : Character;
27450 Task_Dispatching_Policy : Character;
27451 Adafinal : System.Address;
27452 Unreserve_All_Interrupts : Integer;
27453 Exception_Tracebacks : Integer);
27454 @findex __gnat_set_globals
27455 pragma Import (C, Set_Globals, "__gnat_set_globals");
27457 -- SDP_Table_Build is a library routine used to build the
27458 -- exception tables. See unit Ada.Exceptions in files
27459 -- a-except.ads/adb for full details of how zero cost
27460 -- exception handling works. This procedure, the call to
27461 -- it, and the two following tables are all omitted if the
27462 -- build is in longjmp/setjmp exception mode.
27464 @findex SDP_Table_Build
27465 @findex Zero Cost Exceptions
27466 procedure SDP_Table_Build
27467 (SDP_Addresses : System.Address;
27468 SDP_Count : Natural;
27469 Elab_Addresses : System.Address;
27470 Elab_Addr_Count : Natural);
27471 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
27473 -- Table of Unit_Exception_Table addresses. Used for zero
27474 -- cost exception handling to build the top level table.
27476 ST : aliased constant array (1 .. 23) of System.Address := (
27478 Ada.Text_Io'UET_Address,
27479 Ada.Exceptions'UET_Address,
27480 Gnat.Heap_Sort_A'UET_Address,
27481 System.Exception_Table'UET_Address,
27482 System.Machine_State_Operations'UET_Address,
27483 System.Secondary_Stack'UET_Address,
27484 System.Parameters'UET_Address,
27485 System.Soft_Links'UET_Address,
27486 System.Stack_Checking'UET_Address,
27487 System.Traceback'UET_Address,
27488 Ada.Streams'UET_Address,
27489 Ada.Tags'UET_Address,
27490 System.String_Ops'UET_Address,
27491 Interfaces.C_Streams'UET_Address,
27492 System.File_Io'UET_Address,
27493 Ada.Finalization'UET_Address,
27494 System.Finalization_Root'UET_Address,
27495 System.Finalization_Implementation'UET_Address,
27496 System.String_Ops_Concat_3'UET_Address,
27497 System.Stream_Attributes'UET_Address,
27498 System.File_Control_Block'UET_Address,
27499 Ada.Finalization.List_Controller'UET_Address);
27501 -- Table of addresses of elaboration routines. Used for
27502 -- zero cost exception handling to make sure these
27503 -- addresses are included in the top level procedure
27506 EA : aliased constant array (1 .. 23) of System.Address := (
27507 adainit'Code_Address,
27508 Do_Finalize'Code_Address,
27509 Ada.Exceptions'Elab_Spec'Address,
27510 System.Exceptions'Elab_Spec'Address,
27511 Interfaces.C_Streams'Elab_Spec'Address,
27512 System.Exception_Table'Elab_Body'Address,
27513 Ada.Io_Exceptions'Elab_Spec'Address,
27514 System.Stack_Checking'Elab_Spec'Address,
27515 System.Soft_Links'Elab_Body'Address,
27516 System.Secondary_Stack'Elab_Body'Address,
27517 Ada.Tags'Elab_Spec'Address,
27518 Ada.Tags'Elab_Body'Address,
27519 Ada.Streams'Elab_Spec'Address,
27520 System.Finalization_Root'Elab_Spec'Address,
27521 Ada.Exceptions'Elab_Body'Address,
27522 System.Finalization_Implementation'Elab_Spec'Address,
27523 System.Finalization_Implementation'Elab_Body'Address,
27524 Ada.Finalization'Elab_Spec'Address,
27525 Ada.Finalization.List_Controller'Elab_Spec'Address,
27526 System.File_Control_Block'Elab_Spec'Address,
27527 System.File_Io'Elab_Body'Address,
27528 Ada.Text_Io'Elab_Spec'Address,
27529 Ada.Text_Io'Elab_Body'Address);
27531 -- Start of processing for adainit
27535 -- Call SDP_Table_Build to build the top level procedure
27536 -- table for zero cost exception handling (omitted in
27537 -- longjmp/setjmp mode).
27539 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27541 -- Call Set_Globals to record various information for
27542 -- this partition. The values are derived by the binder
27543 -- from information stored in the ali files by the compiler.
27545 @findex __gnat_set_globals
27547 (Main_Priority => -1,
27548 -- Priority of main program, -1 if no pragma Priority used
27550 Time_Slice_Value => -1,
27551 -- Time slice from Time_Slice pragma, -1 if none used
27553 WC_Encoding => 'b',
27554 -- Wide_Character encoding used, default is brackets
27556 Locking_Policy => ' ',
27557 -- Locking_Policy used, default of space means not
27558 -- specified, otherwise it is the first character of
27559 -- the policy name.
27561 Queuing_Policy => ' ',
27562 -- Queuing_Policy used, default of space means not
27563 -- specified, otherwise it is the first character of
27564 -- the policy name.
27566 Task_Dispatching_Policy => ' ',
27567 -- Task_Dispatching_Policy used, default of space means
27568 -- not specified, otherwise first character of the
27571 Adafinal => System.Null_Address,
27572 -- Address of Adafinal routine, not used anymore
27574 Unreserve_All_Interrupts => 0,
27575 -- Set true if pragma Unreserve_All_Interrupts was used
27577 Exception_Tracebacks => 0);
27578 -- Indicates if exception tracebacks are enabled
27580 Elab_Final_Code := 1;
27582 -- Now we have the elaboration calls for all units in the partition.
27583 -- The Elab_Spec and Elab_Body attributes generate references to the
27584 -- implicit elaboration procedures generated by the compiler for
27585 -- each unit that requires elaboration.
27588 Interfaces.C_Streams'Elab_Spec;
27592 Ada.Exceptions'Elab_Spec;
27595 System.Exception_Table'Elab_Body;
27599 Ada.Io_Exceptions'Elab_Spec;
27603 System.Exceptions'Elab_Spec;
27607 System.Stack_Checking'Elab_Spec;
27610 System.Soft_Links'Elab_Body;
27615 System.Secondary_Stack'Elab_Body;
27619 Ada.Tags'Elab_Spec;
27622 Ada.Tags'Elab_Body;
27626 Ada.Streams'Elab_Spec;
27630 System.Finalization_Root'Elab_Spec;
27634 Ada.Exceptions'Elab_Body;
27638 System.Finalization_Implementation'Elab_Spec;
27641 System.Finalization_Implementation'Elab_Body;
27645 Ada.Finalization'Elab_Spec;
27649 Ada.Finalization.List_Controller'Elab_Spec;
27653 System.File_Control_Block'Elab_Spec;
27657 System.File_Io'Elab_Body;
27661 Ada.Text_Io'Elab_Spec;
27664 Ada.Text_Io'Elab_Body;
27668 Elab_Final_Code := 0;
27676 procedure adafinal is
27685 -- main is actually a function, as in the ANSI C standard,
27686 -- defined to return the exit status. The three parameters
27687 -- are the argument count, argument values and environment
27690 @findex Main Program
27693 argv : System.Address;
27694 envp : System.Address)
27697 -- The initialize routine performs low level system
27698 -- initialization using a standard library routine which
27699 -- sets up signal handling and performs any other
27700 -- required setup. The routine can be found in file
27703 @findex __gnat_initialize
27704 procedure initialize;
27705 pragma Import (C, initialize, "__gnat_initialize");
27707 -- The finalize routine performs low level system
27708 -- finalization using a standard library routine. The
27709 -- routine is found in file a-final.c and in the standard
27710 -- distribution is a dummy routine that does nothing, so
27711 -- really this is a hook for special user finalization.
27713 @findex __gnat_finalize
27714 procedure finalize;
27715 pragma Import (C, finalize, "__gnat_finalize");
27717 -- We get to the main program of the partition by using
27718 -- pragma Import because if we try to with the unit and
27719 -- call it Ada style, then not only do we waste time
27720 -- recompiling it, but also, we don't really know the right
27721 -- switches (e.g.@: identifier character set) to be used
27724 procedure Ada_Main_Program;
27725 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27727 -- Start of processing for main
27730 -- Save global variables
27736 -- Call low level system initialization
27740 -- Call our generated Ada initialization routine
27744 -- This is the point at which we want the debugger to get
27749 -- Now we call the main program of the partition
27753 -- Perform Ada finalization
27757 -- Perform low level system finalization
27761 -- Return the proper exit status
27762 return (gnat_exit_status);
27765 -- This section is entirely comments, so it has no effect on the
27766 -- compilation of the Ada_Main package. It provides the list of
27767 -- object files and linker options, as well as some standard
27768 -- libraries needed for the link. The gnatlink utility parses
27769 -- this b~hello.adb file to read these comment lines to generate
27770 -- the appropriate command line arguments for the call to the
27771 -- system linker. The BEGIN/END lines are used for sentinels for
27772 -- this parsing operation.
27774 -- The exact file names will of course depend on the environment,
27775 -- host/target and location of files on the host system.
27777 @findex Object file list
27778 -- BEGIN Object file/option list
27781 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27782 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27783 -- END Object file/option list
27789 The Ada code in the above example is exactly what is generated by the
27790 binder. We have added comments to more clearly indicate the function
27791 of each part of the generated @code{Ada_Main} package.
27793 The code is standard Ada in all respects, and can be processed by any
27794 tools that handle Ada. In particular, it is possible to use the debugger
27795 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27796 suppose that for reasons that you do not understand, your program is crashing
27797 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27798 you can place a breakpoint on the call:
27800 @smallexample @c ada
27801 Ada.Text_Io'Elab_Body;
27805 and trace the elaboration routine for this package to find out where
27806 the problem might be (more usually of course you would be debugging
27807 elaboration code in your own application).
27809 @node Elaboration Order Handling in GNAT
27810 @appendix Elaboration Order Handling in GNAT
27811 @cindex Order of elaboration
27812 @cindex Elaboration control
27815 * Elaboration Code::
27816 * Checking the Elaboration Order::
27817 * Controlling the Elaboration Order::
27818 * Controlling Elaboration in GNAT - Internal Calls::
27819 * Controlling Elaboration in GNAT - External Calls::
27820 * Default Behavior in GNAT - Ensuring Safety::
27821 * Treatment of Pragma Elaborate::
27822 * Elaboration Issues for Library Tasks::
27823 * Mixing Elaboration Models::
27824 * What to Do If the Default Elaboration Behavior Fails::
27825 * Elaboration for Access-to-Subprogram Values::
27826 * Summary of Procedures for Elaboration Control::
27827 * Other Elaboration Order Considerations::
27831 This chapter describes the handling of elaboration code in Ada and
27832 in GNAT, and discusses how the order of elaboration of program units can
27833 be controlled in GNAT, either automatically or with explicit programming
27836 @node Elaboration Code
27837 @section Elaboration Code
27840 Ada provides rather general mechanisms for executing code at elaboration
27841 time, that is to say before the main program starts executing. Such code arises
27845 @item Initializers for variables.
27846 Variables declared at the library level, in package specs or bodies, can
27847 require initialization that is performed at elaboration time, as in:
27848 @smallexample @c ada
27850 Sqrt_Half : Float := Sqrt (0.5);
27854 @item Package initialization code
27855 Code in a @code{BEGIN-END} section at the outer level of a package body is
27856 executed as part of the package body elaboration code.
27858 @item Library level task allocators
27859 Tasks that are declared using task allocators at the library level
27860 start executing immediately and hence can execute at elaboration time.
27864 Subprogram calls are possible in any of these contexts, which means that
27865 any arbitrary part of the program may be executed as part of the elaboration
27866 code. It is even possible to write a program which does all its work at
27867 elaboration time, with a null main program, although stylistically this
27868 would usually be considered an inappropriate way to structure
27871 An important concern arises in the context of elaboration code:
27872 we have to be sure that it is executed in an appropriate order. What we
27873 have is a series of elaboration code sections, potentially one section
27874 for each unit in the program. It is important that these execute
27875 in the correct order. Correctness here means that, taking the above
27876 example of the declaration of @code{Sqrt_Half},
27877 if some other piece of
27878 elaboration code references @code{Sqrt_Half},
27879 then it must run after the
27880 section of elaboration code that contains the declaration of
27883 There would never be any order of elaboration problem if we made a rule
27884 that whenever you @code{with} a unit, you must elaborate both the spec and body
27885 of that unit before elaborating the unit doing the @code{with}'ing:
27887 @smallexample @c ada
27891 package Unit_2 is @dots{}
27897 would require that both the body and spec of @code{Unit_1} be elaborated
27898 before the spec of @code{Unit_2}. However, a rule like that would be far too
27899 restrictive. In particular, it would make it impossible to have routines
27900 in separate packages that were mutually recursive.
27902 You might think that a clever enough compiler could look at the actual
27903 elaboration code and determine an appropriate correct order of elaboration,
27904 but in the general case, this is not possible. Consider the following
27907 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27909 the variable @code{Sqrt_1}, which is declared in the elaboration code
27910 of the body of @code{Unit_1}:
27912 @smallexample @c ada
27914 Sqrt_1 : Float := Sqrt (0.1);
27919 The elaboration code of the body of @code{Unit_1} also contains:
27921 @smallexample @c ada
27924 if expression_1 = 1 then
27925 Q := Unit_2.Func_2;
27932 @code{Unit_2} is exactly parallel,
27933 it has a procedure @code{Func_2} that references
27934 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27935 the body @code{Unit_2}:
27937 @smallexample @c ada
27939 Sqrt_2 : Float := Sqrt (0.1);
27944 The elaboration code of the body of @code{Unit_2} also contains:
27946 @smallexample @c ada
27949 if expression_2 = 2 then
27950 Q := Unit_1.Func_1;
27957 Now the question is, which of the following orders of elaboration is
27982 If you carefully analyze the flow here, you will see that you cannot tell
27983 at compile time the answer to this question.
27984 If @code{expression_1} is not equal to 1,
27985 and @code{expression_2} is not equal to 2,
27986 then either order is acceptable, because neither of the function calls is
27987 executed. If both tests evaluate to true, then neither order is acceptable
27988 and in fact there is no correct order.
27990 If one of the two expressions is true, and the other is false, then one
27991 of the above orders is correct, and the other is incorrect. For example,
27992 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27993 then the call to @code{Func_1}
27994 will occur, but not the call to @code{Func_2.}
27995 This means that it is essential
27996 to elaborate the body of @code{Unit_1} before
27997 the body of @code{Unit_2}, so the first
27998 order of elaboration is correct and the second is wrong.
28000 By making @code{expression_1} and @code{expression_2}
28001 depend on input data, or perhaps
28002 the time of day, we can make it impossible for the compiler or binder
28003 to figure out which of these expressions will be true, and hence it
28004 is impossible to guarantee a safe order of elaboration at run time.
28006 @node Checking the Elaboration Order
28007 @section Checking the Elaboration Order
28010 In some languages that involve the same kind of elaboration problems,
28011 e.g.@: Java and C++, the programmer is expected to worry about these
28012 ordering problems himself, and it is common to
28013 write a program in which an incorrect elaboration order gives
28014 surprising results, because it references variables before they
28016 Ada is designed to be a safe language, and a programmer-beware approach is
28017 clearly not sufficient. Consequently, the language provides three lines
28021 @item Standard rules
28022 Some standard rules restrict the possible choice of elaboration
28023 order. In particular, if you @code{with} a unit, then its spec is always
28024 elaborated before the unit doing the @code{with}. Similarly, a parent
28025 spec is always elaborated before the child spec, and finally
28026 a spec is always elaborated before its corresponding body.
28028 @item Dynamic elaboration checks
28029 @cindex Elaboration checks
28030 @cindex Checks, elaboration
28031 Dynamic checks are made at run time, so that if some entity is accessed
28032 before it is elaborated (typically by means of a subprogram call)
28033 then the exception (@code{Program_Error}) is raised.
28035 @item Elaboration control
28036 Facilities are provided for the programmer to specify the desired order
28040 Let's look at these facilities in more detail. First, the rules for
28041 dynamic checking. One possible rule would be simply to say that the
28042 exception is raised if you access a variable which has not yet been
28043 elaborated. The trouble with this approach is that it could require
28044 expensive checks on every variable reference. Instead Ada has two
28045 rules which are a little more restrictive, but easier to check, and
28049 @item Restrictions on calls
28050 A subprogram can only be called at elaboration time if its body
28051 has been elaborated. The rules for elaboration given above guarantee
28052 that the spec of the subprogram has been elaborated before the
28053 call, but not the body. If this rule is violated, then the
28054 exception @code{Program_Error} is raised.
28056 @item Restrictions on instantiations
28057 A generic unit can only be instantiated if the body of the generic
28058 unit has been elaborated. Again, the rules for elaboration given above
28059 guarantee that the spec of the generic unit has been elaborated
28060 before the instantiation, but not the body. If this rule is
28061 violated, then the exception @code{Program_Error} is raised.
28065 The idea is that if the body has been elaborated, then any variables
28066 it references must have been elaborated; by checking for the body being
28067 elaborated we guarantee that none of its references causes any
28068 trouble. As we noted above, this is a little too restrictive, because a
28069 subprogram that has no non-local references in its body may in fact be safe
28070 to call. However, it really would be unsafe to rely on this, because
28071 it would mean that the caller was aware of details of the implementation
28072 in the body. This goes against the basic tenets of Ada.
28074 A plausible implementation can be described as follows.
28075 A Boolean variable is associated with each subprogram
28076 and each generic unit. This variable is initialized to False, and is set to
28077 True at the point body is elaborated. Every call or instantiation checks the
28078 variable, and raises @code{Program_Error} if the variable is False.
28080 Note that one might think that it would be good enough to have one Boolean
28081 variable for each package, but that would not deal with cases of trying
28082 to call a body in the same package as the call
28083 that has not been elaborated yet.
28084 Of course a compiler may be able to do enough analysis to optimize away
28085 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
28086 does such optimizations, but still the easiest conceptual model is to
28087 think of there being one variable per subprogram.
28089 @node Controlling the Elaboration Order
28090 @section Controlling the Elaboration Order
28093 In the previous section we discussed the rules in Ada which ensure
28094 that @code{Program_Error} is raised if an incorrect elaboration order is
28095 chosen. This prevents erroneous executions, but we need mechanisms to
28096 specify a correct execution and avoid the exception altogether.
28097 To achieve this, Ada provides a number of features for controlling
28098 the order of elaboration. We discuss these features in this section.
28100 First, there are several ways of indicating to the compiler that a given
28101 unit has no elaboration problems:
28104 @item packages that do not require a body
28105 A library package that does not require a body does not permit
28106 a body (this rule was introduced in Ada 95).
28107 Thus if we have a such a package, as in:
28109 @smallexample @c ada
28112 package Definitions is
28114 type m is new integer;
28116 type a is array (1 .. 10) of m;
28117 type b is array (1 .. 20) of m;
28125 A package that @code{with}'s @code{Definitions} may safely instantiate
28126 @code{Definitions.Subp} because the compiler can determine that there
28127 definitely is no package body to worry about in this case
28130 @cindex pragma Pure
28132 Places sufficient restrictions on a unit to guarantee that
28133 no call to any subprogram in the unit can result in an
28134 elaboration problem. This means that the compiler does not need
28135 to worry about the point of elaboration of such units, and in
28136 particular, does not need to check any calls to any subprograms
28139 @item pragma Preelaborate
28140 @findex Preelaborate
28141 @cindex pragma Preelaborate
28142 This pragma places slightly less stringent restrictions on a unit than
28144 but these restrictions are still sufficient to ensure that there
28145 are no elaboration problems with any calls to the unit.
28147 @item pragma Elaborate_Body
28148 @findex Elaborate_Body
28149 @cindex pragma Elaborate_Body
28150 This pragma requires that the body of a unit be elaborated immediately
28151 after its spec. Suppose a unit @code{A} has such a pragma,
28152 and unit @code{B} does
28153 a @code{with} of unit @code{A}. Recall that the standard rules require
28154 the spec of unit @code{A}
28155 to be elaborated before the @code{with}'ing unit; given the pragma in
28156 @code{A}, we also know that the body of @code{A}
28157 will be elaborated before @code{B}, so
28158 that calls to @code{A} are safe and do not need a check.
28163 unlike pragma @code{Pure} and pragma @code{Preelaborate},
28165 @code{Elaborate_Body} does not guarantee that the program is
28166 free of elaboration problems, because it may not be possible
28167 to satisfy the requested elaboration order.
28168 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
28170 marks @code{Unit_1} as @code{Elaborate_Body},
28171 and not @code{Unit_2,} then the order of
28172 elaboration will be:
28184 Now that means that the call to @code{Func_1} in @code{Unit_2}
28185 need not be checked,
28186 it must be safe. But the call to @code{Func_2} in
28187 @code{Unit_1} may still fail if
28188 @code{Expression_1} is equal to 1,
28189 and the programmer must still take
28190 responsibility for this not being the case.
28192 If all units carry a pragma @code{Elaborate_Body}, then all problems are
28193 eliminated, except for calls entirely within a body, which are
28194 in any case fully under programmer control. However, using the pragma
28195 everywhere is not always possible.
28196 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
28197 we marked both of them as having pragma @code{Elaborate_Body}, then
28198 clearly there would be no possible elaboration order.
28200 The above pragmas allow a server to guarantee safe use by clients, and
28201 clearly this is the preferable approach. Consequently a good rule
28202 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
28203 and if this is not possible,
28204 mark them as @code{Elaborate_Body} if possible.
28205 As we have seen, there are situations where neither of these
28206 three pragmas can be used.
28207 So we also provide methods for clients to control the
28208 order of elaboration of the servers on which they depend:
28211 @item pragma Elaborate (unit)
28213 @cindex pragma Elaborate
28214 This pragma is placed in the context clause, after a @code{with} clause,
28215 and it requires that the body of the named unit be elaborated before
28216 the unit in which the pragma occurs. The idea is to use this pragma
28217 if the current unit calls at elaboration time, directly or indirectly,
28218 some subprogram in the named unit.
28220 @item pragma Elaborate_All (unit)
28221 @findex Elaborate_All
28222 @cindex pragma Elaborate_All
28223 This is a stronger version of the Elaborate pragma. Consider the
28227 Unit A @code{with}'s unit B and calls B.Func in elab code
28228 Unit B @code{with}'s unit C, and B.Func calls C.Func
28232 Now if we put a pragma @code{Elaborate (B)}
28233 in unit @code{A}, this ensures that the
28234 body of @code{B} is elaborated before the call, but not the
28235 body of @code{C}, so
28236 the call to @code{C.Func} could still cause @code{Program_Error} to
28239 The effect of a pragma @code{Elaborate_All} is stronger, it requires
28240 not only that the body of the named unit be elaborated before the
28241 unit doing the @code{with}, but also the bodies of all units that the
28242 named unit uses, following @code{with} links transitively. For example,
28243 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
28245 not only that the body of @code{B} be elaborated before @code{A},
28247 body of @code{C}, because @code{B} @code{with}'s @code{C}.
28251 We are now in a position to give a usage rule in Ada for avoiding
28252 elaboration problems, at least if dynamic dispatching and access to
28253 subprogram values are not used. We will handle these cases separately
28256 The rule is simple. If a unit has elaboration code that can directly or
28257 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
28258 a generic package in a @code{with}'ed unit,
28259 then if the @code{with}'ed unit does not have
28260 pragma @code{Pure} or @code{Preelaborate}, then the client should have
28261 a pragma @code{Elaborate_All}
28262 for the @code{with}'ed unit. By following this rule a client is
28263 assured that calls can be made without risk of an exception.
28265 For generic subprogram instantiations, the rule can be relaxed to
28266 require only a pragma @code{Elaborate} since elaborating the body
28267 of a subprogram cannot cause any transitive elaboration (we are
28268 not calling the subprogram in this case, just elaborating its
28271 If this rule is not followed, then a program may be in one of four
28275 @item No order exists
28276 No order of elaboration exists which follows the rules, taking into
28277 account any @code{Elaborate}, @code{Elaborate_All},
28278 or @code{Elaborate_Body} pragmas. In
28279 this case, an Ada compiler must diagnose the situation at bind
28280 time, and refuse to build an executable program.
28282 @item One or more orders exist, all incorrect
28283 One or more acceptable elaboration orders exist, and all of them
28284 generate an elaboration order problem. In this case, the binder
28285 can build an executable program, but @code{Program_Error} will be raised
28286 when the program is run.
28288 @item Several orders exist, some right, some incorrect
28289 One or more acceptable elaboration orders exists, and some of them
28290 work, and some do not. The programmer has not controlled
28291 the order of elaboration, so the binder may or may not pick one of
28292 the correct orders, and the program may or may not raise an
28293 exception when it is run. This is the worst case, because it means
28294 that the program may fail when moved to another compiler, or even
28295 another version of the same compiler.
28297 @item One or more orders exists, all correct
28298 One ore more acceptable elaboration orders exist, and all of them
28299 work. In this case the program runs successfully. This state of
28300 affairs can be guaranteed by following the rule we gave above, but
28301 may be true even if the rule is not followed.
28305 Note that one additional advantage of following our rules on the use
28306 of @code{Elaborate} and @code{Elaborate_All}
28307 is that the program continues to stay in the ideal (all orders OK) state
28308 even if maintenance
28309 changes some bodies of some units. Conversely, if a program that does
28310 not follow this rule happens to be safe at some point, this state of affairs
28311 may deteriorate silently as a result of maintenance changes.
28313 You may have noticed that the above discussion did not mention
28314 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
28315 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
28316 code in the body makes calls to some other unit, so it is still necessary
28317 to use @code{Elaborate_All} on such units.
28319 @node Controlling Elaboration in GNAT - Internal Calls
28320 @section Controlling Elaboration in GNAT - Internal Calls
28323 In the case of internal calls, i.e., calls within a single package, the
28324 programmer has full control over the order of elaboration, and it is up
28325 to the programmer to elaborate declarations in an appropriate order. For
28328 @smallexample @c ada
28331 function One return Float;
28335 function One return Float is
28344 will obviously raise @code{Program_Error} at run time, because function
28345 One will be called before its body is elaborated. In this case GNAT will
28346 generate a warning that the call will raise @code{Program_Error}:
28352 2. function One return Float;
28354 4. Q : Float := One;
28356 >>> warning: cannot call "One" before body is elaborated
28357 >>> warning: Program_Error will be raised at run time
28360 6. function One return Float is
28373 Note that in this particular case, it is likely that the call is safe, because
28374 the function @code{One} does not access any global variables.
28375 Nevertheless in Ada, we do not want the validity of the check to depend on
28376 the contents of the body (think about the separate compilation case), so this
28377 is still wrong, as we discussed in the previous sections.
28379 The error is easily corrected by rearranging the declarations so that the
28380 body of @code{One} appears before the declaration containing the call
28381 (note that in Ada 95 and Ada 2005,
28382 declarations can appear in any order, so there is no restriction that
28383 would prevent this reordering, and if we write:
28385 @smallexample @c ada
28388 function One return Float;
28390 function One return Float is
28401 then all is well, no warning is generated, and no
28402 @code{Program_Error} exception
28404 Things are more complicated when a chain of subprograms is executed:
28406 @smallexample @c ada
28409 function A return Integer;
28410 function B return Integer;
28411 function C return Integer;
28413 function B return Integer is begin return A; end;
28414 function C return Integer is begin return B; end;
28418 function A return Integer is begin return 1; end;
28424 Now the call to @code{C}
28425 at elaboration time in the declaration of @code{X} is correct, because
28426 the body of @code{C} is already elaborated,
28427 and the call to @code{B} within the body of
28428 @code{C} is correct, but the call
28429 to @code{A} within the body of @code{B} is incorrect, because the body
28430 of @code{A} has not been elaborated, so @code{Program_Error}
28431 will be raised on the call to @code{A}.
28432 In this case GNAT will generate a
28433 warning that @code{Program_Error} may be
28434 raised at the point of the call. Let's look at the warning:
28440 2. function A return Integer;
28441 3. function B return Integer;
28442 4. function C return Integer;
28444 6. function B return Integer is begin return A; end;
28446 >>> warning: call to "A" before body is elaborated may
28447 raise Program_Error
28448 >>> warning: "B" called at line 7
28449 >>> warning: "C" called at line 9
28451 7. function C return Integer is begin return B; end;
28453 9. X : Integer := C;
28455 11. function A return Integer is begin return 1; end;
28465 Note that the message here says ``may raise'', instead of the direct case,
28466 where the message says ``will be raised''. That's because whether
28468 actually called depends in general on run-time flow of control.
28469 For example, if the body of @code{B} said
28471 @smallexample @c ada
28474 function B return Integer is
28476 if some-condition-depending-on-input-data then
28487 then we could not know until run time whether the incorrect call to A would
28488 actually occur, so @code{Program_Error} might
28489 or might not be raised. It is possible for a compiler to
28490 do a better job of analyzing bodies, to
28491 determine whether or not @code{Program_Error}
28492 might be raised, but it certainly
28493 couldn't do a perfect job (that would require solving the halting problem
28494 and is provably impossible), and because this is a warning anyway, it does
28495 not seem worth the effort to do the analysis. Cases in which it
28496 would be relevant are rare.
28498 In practice, warnings of either of the forms given
28499 above will usually correspond to
28500 real errors, and should be examined carefully and eliminated.
28501 In the rare case where a warning is bogus, it can be suppressed by any of
28502 the following methods:
28506 Compile with the @option{-gnatws} switch set
28509 Suppress @code{Elaboration_Check} for the called subprogram
28512 Use pragma @code{Warnings_Off} to turn warnings off for the call
28516 For the internal elaboration check case,
28517 GNAT by default generates the
28518 necessary run-time checks to ensure
28519 that @code{Program_Error} is raised if any
28520 call fails an elaboration check. Of course this can only happen if a
28521 warning has been issued as described above. The use of pragma
28522 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28523 some of these checks, meaning that it may be possible (but is not
28524 guaranteed) for a program to be able to call a subprogram whose body
28525 is not yet elaborated, without raising a @code{Program_Error} exception.
28527 @node Controlling Elaboration in GNAT - External Calls
28528 @section Controlling Elaboration in GNAT - External Calls
28531 The previous section discussed the case in which the execution of a
28532 particular thread of elaboration code occurred entirely within a
28533 single unit. This is the easy case to handle, because a programmer
28534 has direct and total control over the order of elaboration, and
28535 furthermore, checks need only be generated in cases which are rare
28536 and which the compiler can easily detect.
28537 The situation is more complex when separate compilation is taken into account.
28538 Consider the following:
28540 @smallexample @c ada
28544 function Sqrt (Arg : Float) return Float;
28547 package body Math is
28548 function Sqrt (Arg : Float) return Float is
28557 X : Float := Math.Sqrt (0.5);
28570 where @code{Main} is the main program. When this program is executed, the
28571 elaboration code must first be executed, and one of the jobs of the
28572 binder is to determine the order in which the units of a program are
28573 to be elaborated. In this case we have four units: the spec and body
28575 the spec of @code{Stuff} and the body of @code{Main}).
28576 In what order should the four separate sections of elaboration code
28579 There are some restrictions in the order of elaboration that the binder
28580 can choose. In particular, if unit U has a @code{with}
28581 for a package @code{X}, then you
28582 are assured that the spec of @code{X}
28583 is elaborated before U , but you are
28584 not assured that the body of @code{X}
28585 is elaborated before U.
28586 This means that in the above case, the binder is allowed to choose the
28597 but that's not good, because now the call to @code{Math.Sqrt}
28598 that happens during
28599 the elaboration of the @code{Stuff}
28600 spec happens before the body of @code{Math.Sqrt} is
28601 elaborated, and hence causes @code{Program_Error} exception to be raised.
28602 At first glance, one might say that the binder is misbehaving, because
28603 obviously you want to elaborate the body of something you @code{with}
28605 that is not a general rule that can be followed in all cases. Consider
28607 @smallexample @c ada
28610 package X is @dots{}
28612 package Y is @dots{}
28615 package body Y is @dots{}
28618 package body X is @dots{}
28624 This is a common arrangement, and, apart from the order of elaboration
28625 problems that might arise in connection with elaboration code, this works fine.
28626 A rule that says that you must first elaborate the body of anything you
28627 @code{with} cannot work in this case:
28628 the body of @code{X} @code{with}'s @code{Y},
28629 which means you would have to
28630 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28632 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28633 loop that cannot be broken.
28635 It is true that the binder can in many cases guess an order of elaboration
28636 that is unlikely to cause a @code{Program_Error}
28637 exception to be raised, and it tries to do so (in the
28638 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28640 elaborate the body of @code{Math} right after its spec, so all will be well).
28642 However, a program that blindly relies on the binder to be helpful can
28643 get into trouble, as we discussed in the previous sections, so
28645 provides a number of facilities for assisting the programmer in
28646 developing programs that are robust with respect to elaboration order.
28648 @node Default Behavior in GNAT - Ensuring Safety
28649 @section Default Behavior in GNAT - Ensuring Safety
28652 The default behavior in GNAT ensures elaboration safety. In its
28653 default mode GNAT implements the
28654 rule we previously described as the right approach. Let's restate it:
28658 @emph{If a unit has elaboration code that can directly or indirectly make a
28659 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28660 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28661 does not have pragma @code{Pure} or
28662 @code{Preelaborate}, then the client should have an
28663 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28665 @emph{In the case of instantiating a generic subprogram, it is always
28666 sufficient to have only an @code{Elaborate} pragma for the
28667 @code{with}'ed unit.}
28671 By following this rule a client is assured that calls and instantiations
28672 can be made without risk of an exception.
28674 In this mode GNAT traces all calls that are potentially made from
28675 elaboration code, and puts in any missing implicit @code{Elaborate}
28676 and @code{Elaborate_All} pragmas.
28677 The advantage of this approach is that no elaboration problems
28678 are possible if the binder can find an elaboration order that is
28679 consistent with these implicit @code{Elaborate} and
28680 @code{Elaborate_All} pragmas. The
28681 disadvantage of this approach is that no such order may exist.
28683 If the binder does not generate any diagnostics, then it means that it has
28684 found an elaboration order that is guaranteed to be safe. However, the binder
28685 may still be relying on implicitly generated @code{Elaborate} and
28686 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28689 If it is important to guarantee portability, then the compilations should
28692 (warn on elaboration problems) switch. This will cause warning messages
28693 to be generated indicating the missing @code{Elaborate} and
28694 @code{Elaborate_All} pragmas.
28695 Consider the following source program:
28697 @smallexample @c ada
28702 m : integer := k.r;
28709 where it is clear that there
28710 should be a pragma @code{Elaborate_All}
28711 for unit @code{k}. An implicit pragma will be generated, and it is
28712 likely that the binder will be able to honor it. However, if you want
28713 to port this program to some other Ada compiler than GNAT.
28714 it is safer to include the pragma explicitly in the source. If this
28715 unit is compiled with the
28717 switch, then the compiler outputs a warning:
28724 3. m : integer := k.r;
28726 >>> warning: call to "r" may raise Program_Error
28727 >>> warning: missing pragma Elaborate_All for "k"
28735 and these warnings can be used as a guide for supplying manually
28736 the missing pragmas. It is usually a bad idea to use this warning
28737 option during development. That's because it will warn you when
28738 you need to put in a pragma, but cannot warn you when it is time
28739 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28740 unnecessary dependencies and even false circularities.
28742 This default mode is more restrictive than the Ada Reference
28743 Manual, and it is possible to construct programs which will compile
28744 using the dynamic model described there, but will run into a
28745 circularity using the safer static model we have described.
28747 Of course any Ada compiler must be able to operate in a mode
28748 consistent with the requirements of the Ada Reference Manual,
28749 and in particular must have the capability of implementing the
28750 standard dynamic model of elaboration with run-time checks.
28752 In GNAT, this standard mode can be achieved either by the use of
28753 the @option{-gnatE} switch on the compiler (@command{gcc} or
28754 @command{gnatmake}) command, or by the use of the configuration pragma:
28756 @smallexample @c ada
28757 pragma Elaboration_Checks (DYNAMIC);
28761 Either approach will cause the unit affected to be compiled using the
28762 standard dynamic run-time elaboration checks described in the Ada
28763 Reference Manual. The static model is generally preferable, since it
28764 is clearly safer to rely on compile and link time checks rather than
28765 run-time checks. However, in the case of legacy code, it may be
28766 difficult to meet the requirements of the static model. This
28767 issue is further discussed in
28768 @ref{What to Do If the Default Elaboration Behavior Fails}.
28770 Note that the static model provides a strict subset of the allowed
28771 behavior and programs of the Ada Reference Manual, so if you do
28772 adhere to the static model and no circularities exist,
28773 then you are assured that your program will
28774 work using the dynamic model, providing that you remove any
28775 pragma Elaborate statements from the source.
28777 @node Treatment of Pragma Elaborate
28778 @section Treatment of Pragma Elaborate
28779 @cindex Pragma Elaborate
28782 The use of @code{pragma Elaborate}
28783 should generally be avoided in Ada 95 and Ada 2005 programs,
28784 since there is no guarantee that transitive calls
28785 will be properly handled. Indeed at one point, this pragma was placed
28786 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28788 Now that's a bit restrictive. In practice, the case in which
28789 @code{pragma Elaborate} is useful is when the caller knows that there
28790 are no transitive calls, or that the called unit contains all necessary
28791 transitive @code{pragma Elaborate} statements, and legacy code often
28792 contains such uses.
28794 Strictly speaking the static mode in GNAT should ignore such pragmas,
28795 since there is no assurance at compile time that the necessary safety
28796 conditions are met. In practice, this would cause GNAT to be incompatible
28797 with correctly written Ada 83 code that had all necessary
28798 @code{pragma Elaborate} statements in place. Consequently, we made the
28799 decision that GNAT in its default mode will believe that if it encounters
28800 a @code{pragma Elaborate} then the programmer knows what they are doing,
28801 and it will trust that no elaboration errors can occur.
28803 The result of this decision is two-fold. First to be safe using the
28804 static mode, you should remove all @code{pragma Elaborate} statements.
28805 Second, when fixing circularities in existing code, you can selectively
28806 use @code{pragma Elaborate} statements to convince the static mode of
28807 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28810 When using the static mode with @option{-gnatwl}, any use of
28811 @code{pragma Elaborate} will generate a warning about possible
28814 @node Elaboration Issues for Library Tasks
28815 @section Elaboration Issues for Library Tasks
28816 @cindex Library tasks, elaboration issues
28817 @cindex Elaboration of library tasks
28820 In this section we examine special elaboration issues that arise for
28821 programs that declare library level tasks.
28823 Generally the model of execution of an Ada program is that all units are
28824 elaborated, and then execution of the program starts. However, the
28825 declaration of library tasks definitely does not fit this model. The
28826 reason for this is that library tasks start as soon as they are declared
28827 (more precisely, as soon as the statement part of the enclosing package
28828 body is reached), that is to say before elaboration
28829 of the program is complete. This means that if such a task calls a
28830 subprogram, or an entry in another task, the callee may or may not be
28831 elaborated yet, and in the standard
28832 Reference Manual model of dynamic elaboration checks, you can even
28833 get timing dependent Program_Error exceptions, since there can be
28834 a race between the elaboration code and the task code.
28836 The static model of elaboration in GNAT seeks to avoid all such
28837 dynamic behavior, by being conservative, and the conservative
28838 approach in this particular case is to assume that all the code
28839 in a task body is potentially executed at elaboration time if
28840 a task is declared at the library level.
28842 This can definitely result in unexpected circularities. Consider
28843 the following example
28845 @smallexample @c ada
28851 type My_Int is new Integer;
28853 function Ident (M : My_Int) return My_Int;
28857 package body Decls is
28858 task body Lib_Task is
28864 function Ident (M : My_Int) return My_Int is
28872 procedure Put_Val (Arg : Decls.My_Int);
28876 package body Utils is
28877 procedure Put_Val (Arg : Decls.My_Int) is
28879 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28886 Decls.Lib_Task.Start;
28891 If the above example is compiled in the default static elaboration
28892 mode, then a circularity occurs. The circularity comes from the call
28893 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28894 this call occurs in elaboration code, we need an implicit pragma
28895 @code{Elaborate_All} for @code{Utils}. This means that not only must
28896 the spec and body of @code{Utils} be elaborated before the body
28897 of @code{Decls}, but also the spec and body of any unit that is
28898 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28899 the body of @code{Decls}. This is the transitive implication of
28900 pragma @code{Elaborate_All} and it makes sense, because in general
28901 the body of @code{Put_Val} might have a call to something in a
28902 @code{with'ed} unit.
28904 In this case, the body of Utils (actually its spec) @code{with's}
28905 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28906 must be elaborated before itself, in case there is a call from the
28907 body of @code{Utils}.
28909 Here is the exact chain of events we are worrying about:
28913 In the body of @code{Decls} a call is made from within the body of a library
28914 task to a subprogram in the package @code{Utils}. Since this call may
28915 occur at elaboration time (given that the task is activated at elaboration
28916 time), we have to assume the worst, i.e., that the
28917 call does happen at elaboration time.
28920 This means that the body and spec of @code{Util} must be elaborated before
28921 the body of @code{Decls} so that this call does not cause an access before
28925 Within the body of @code{Util}, specifically within the body of
28926 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28930 One such @code{with}'ed package is package @code{Decls}, so there
28931 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28932 In fact there is such a call in this example, but we would have to
28933 assume that there was such a call even if it were not there, since
28934 we are not supposed to write the body of @code{Decls} knowing what
28935 is in the body of @code{Utils}; certainly in the case of the
28936 static elaboration model, the compiler does not know what is in
28937 other bodies and must assume the worst.
28940 This means that the spec and body of @code{Decls} must also be
28941 elaborated before we elaborate the unit containing the call, but
28942 that unit is @code{Decls}! This means that the body of @code{Decls}
28943 must be elaborated before itself, and that's a circularity.
28947 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28948 the body of @code{Decls} you will get a true Ada Reference Manual
28949 circularity that makes the program illegal.
28951 In practice, we have found that problems with the static model of
28952 elaboration in existing code often arise from library tasks, so
28953 we must address this particular situation.
28955 Note that if we compile and run the program above, using the dynamic model of
28956 elaboration (that is to say use the @option{-gnatE} switch),
28957 then it compiles, binds,
28958 links, and runs, printing the expected result of 2. Therefore in some sense
28959 the circularity here is only apparent, and we need to capture
28960 the properties of this program that distinguish it from other library-level
28961 tasks that have real elaboration problems.
28963 We have four possible answers to this question:
28968 Use the dynamic model of elaboration.
28970 If we use the @option{-gnatE} switch, then as noted above, the program works.
28971 Why is this? If we examine the task body, it is apparent that the task cannot
28973 @code{accept} statement until after elaboration has been completed, because
28974 the corresponding entry call comes from the main program, not earlier.
28975 This is why the dynamic model works here. But that's really giving
28976 up on a precise analysis, and we prefer to take this approach only if we cannot
28978 problem in any other manner. So let us examine two ways to reorganize
28979 the program to avoid the potential elaboration problem.
28982 Split library tasks into separate packages.
28984 Write separate packages, so that library tasks are isolated from
28985 other declarations as much as possible. Let us look at a variation on
28988 @smallexample @c ada
28996 package body Decls1 is
28997 task body Lib_Task is
29005 type My_Int is new Integer;
29006 function Ident (M : My_Int) return My_Int;
29010 package body Decls2 is
29011 function Ident (M : My_Int) return My_Int is
29019 procedure Put_Val (Arg : Decls2.My_Int);
29023 package body Utils is
29024 procedure Put_Val (Arg : Decls2.My_Int) is
29026 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
29033 Decls1.Lib_Task.Start;
29038 All we have done is to split @code{Decls} into two packages, one
29039 containing the library task, and one containing everything else. Now
29040 there is no cycle, and the program compiles, binds, links and executes
29041 using the default static model of elaboration.
29044 Declare separate task types.
29046 A significant part of the problem arises because of the use of the
29047 single task declaration form. This means that the elaboration of
29048 the task type, and the elaboration of the task itself (i.e.@: the
29049 creation of the task) happen at the same time. A good rule
29050 of style in Ada is to always create explicit task types. By
29051 following the additional step of placing task objects in separate
29052 packages from the task type declaration, many elaboration problems
29053 are avoided. Here is another modified example of the example program:
29055 @smallexample @c ada
29057 task type Lib_Task_Type is
29061 type My_Int is new Integer;
29063 function Ident (M : My_Int) return My_Int;
29067 package body Decls is
29068 task body Lib_Task_Type is
29074 function Ident (M : My_Int) return My_Int is
29082 procedure Put_Val (Arg : Decls.My_Int);
29086 package body Utils is
29087 procedure Put_Val (Arg : Decls.My_Int) is
29089 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
29095 Lib_Task : Decls.Lib_Task_Type;
29101 Declst.Lib_Task.Start;
29106 What we have done here is to replace the @code{task} declaration in
29107 package @code{Decls} with a @code{task type} declaration. Then we
29108 introduce a separate package @code{Declst} to contain the actual
29109 task object. This separates the elaboration issues for
29110 the @code{task type}
29111 declaration, which causes no trouble, from the elaboration issues
29112 of the task object, which is also unproblematic, since it is now independent
29113 of the elaboration of @code{Utils}.
29114 This separation of concerns also corresponds to
29115 a generally sound engineering principle of separating declarations
29116 from instances. This version of the program also compiles, binds, links,
29117 and executes, generating the expected output.
29120 Use No_Entry_Calls_In_Elaboration_Code restriction.
29121 @cindex No_Entry_Calls_In_Elaboration_Code
29123 The previous two approaches described how a program can be restructured
29124 to avoid the special problems caused by library task bodies. in practice,
29125 however, such restructuring may be difficult to apply to existing legacy code,
29126 so we must consider solutions that do not require massive rewriting.
29128 Let us consider more carefully why our original sample program works
29129 under the dynamic model of elaboration. The reason is that the code
29130 in the task body blocks immediately on the @code{accept}
29131 statement. Now of course there is nothing to prohibit elaboration
29132 code from making entry calls (for example from another library level task),
29133 so we cannot tell in isolation that
29134 the task will not execute the accept statement during elaboration.
29136 However, in practice it is very unusual to see elaboration code
29137 make any entry calls, and the pattern of tasks starting
29138 at elaboration time and then immediately blocking on @code{accept} or
29139 @code{select} statements is very common. What this means is that
29140 the compiler is being too pessimistic when it analyzes the
29141 whole package body as though it might be executed at elaboration
29144 If we know that the elaboration code contains no entry calls, (a very safe
29145 assumption most of the time, that could almost be made the default
29146 behavior), then we can compile all units of the program under control
29147 of the following configuration pragma:
29150 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
29154 This pragma can be placed in the @file{gnat.adc} file in the usual
29155 manner. If we take our original unmodified program and compile it
29156 in the presence of a @file{gnat.adc} containing the above pragma,
29157 then once again, we can compile, bind, link, and execute, obtaining
29158 the expected result. In the presence of this pragma, the compiler does
29159 not trace calls in a task body, that appear after the first @code{accept}
29160 or @code{select} statement, and therefore does not report a potential
29161 circularity in the original program.
29163 The compiler will check to the extent it can that the above
29164 restriction is not violated, but it is not always possible to do a
29165 complete check at compile time, so it is important to use this
29166 pragma only if the stated restriction is in fact met, that is to say
29167 no task receives an entry call before elaboration of all units is completed.
29171 @node Mixing Elaboration Models
29172 @section Mixing Elaboration Models
29174 So far, we have assumed that the entire program is either compiled
29175 using the dynamic model or static model, ensuring consistency. It
29176 is possible to mix the two models, but rules have to be followed
29177 if this mixing is done to ensure that elaboration checks are not
29180 The basic rule is that @emph{a unit compiled with the static model cannot
29181 be @code{with'ed} by a unit compiled with the dynamic model}. The
29182 reason for this is that in the static model, a unit assumes that
29183 its clients guarantee to use (the equivalent of) pragma
29184 @code{Elaborate_All} so that no elaboration checks are required
29185 in inner subprograms, and this assumption is violated if the
29186 client is compiled with dynamic checks.
29188 The precise rule is as follows. A unit that is compiled with dynamic
29189 checks can only @code{with} a unit that meets at least one of the
29190 following criteria:
29195 The @code{with'ed} unit is itself compiled with dynamic elaboration
29196 checks (that is with the @option{-gnatE} switch.
29199 The @code{with'ed} unit is an internal GNAT implementation unit from
29200 the System, Interfaces, Ada, or GNAT hierarchies.
29203 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
29206 The @code{with'ing} unit (that is the client) has an explicit pragma
29207 @code{Elaborate_All} for the @code{with'ed} unit.
29212 If this rule is violated, that is if a unit with dynamic elaboration
29213 checks @code{with's} a unit that does not meet one of the above four
29214 criteria, then the binder (@code{gnatbind}) will issue a warning
29215 similar to that in the following example:
29218 warning: "x.ads" has dynamic elaboration checks and with's
29219 warning: "y.ads" which has static elaboration checks
29223 These warnings indicate that the rule has been violated, and that as a result
29224 elaboration checks may be missed in the resulting executable file.
29225 This warning may be suppressed using the @option{-ws} binder switch
29226 in the usual manner.
29228 One useful application of this mixing rule is in the case of a subsystem
29229 which does not itself @code{with} units from the remainder of the
29230 application. In this case, the entire subsystem can be compiled with
29231 dynamic checks to resolve a circularity in the subsystem, while
29232 allowing the main application that uses this subsystem to be compiled
29233 using the more reliable default static model.
29235 @node What to Do If the Default Elaboration Behavior Fails
29236 @section What to Do If the Default Elaboration Behavior Fails
29239 If the binder cannot find an acceptable order, it outputs detailed
29240 diagnostics. For example:
29246 error: elaboration circularity detected
29247 info: "proc (body)" must be elaborated before "pack (body)"
29248 info: reason: Elaborate_All probably needed in unit "pack (body)"
29249 info: recompile "pack (body)" with -gnatwl
29250 info: for full details
29251 info: "proc (body)"
29252 info: is needed by its spec:
29253 info: "proc (spec)"
29254 info: which is withed by:
29255 info: "pack (body)"
29256 info: "pack (body)" must be elaborated before "proc (body)"
29257 info: reason: pragma Elaborate in unit "proc (body)"
29263 In this case we have a cycle that the binder cannot break. On the one
29264 hand, there is an explicit pragma Elaborate in @code{proc} for
29265 @code{pack}. This means that the body of @code{pack} must be elaborated
29266 before the body of @code{proc}. On the other hand, there is elaboration
29267 code in @code{pack} that calls a subprogram in @code{proc}. This means
29268 that for maximum safety, there should really be a pragma
29269 Elaborate_All in @code{pack} for @code{proc} which would require that
29270 the body of @code{proc} be elaborated before the body of
29271 @code{pack}. Clearly both requirements cannot be satisfied.
29272 Faced with a circularity of this kind, you have three different options.
29275 @item Fix the program
29276 The most desirable option from the point of view of long-term maintenance
29277 is to rearrange the program so that the elaboration problems are avoided.
29278 One useful technique is to place the elaboration code into separate
29279 child packages. Another is to move some of the initialization code to
29280 explicitly called subprograms, where the program controls the order
29281 of initialization explicitly. Although this is the most desirable option,
29282 it may be impractical and involve too much modification, especially in
29283 the case of complex legacy code.
29285 @item Perform dynamic checks
29286 If the compilations are done using the
29288 (dynamic elaboration check) switch, then GNAT behaves in a quite different
29289 manner. Dynamic checks are generated for all calls that could possibly result
29290 in raising an exception. With this switch, the compiler does not generate
29291 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
29292 exactly as specified in the @cite{Ada Reference Manual}.
29293 The binder will generate
29294 an executable program that may or may not raise @code{Program_Error}, and then
29295 it is the programmer's job to ensure that it does not raise an exception. Note
29296 that it is important to compile all units with the switch, it cannot be used
29299 @item Suppress checks
29300 The drawback of dynamic checks is that they generate a
29301 significant overhead at run time, both in space and time. If you
29302 are absolutely sure that your program cannot raise any elaboration
29303 exceptions, and you still want to use the dynamic elaboration model,
29304 then you can use the configuration pragma
29305 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
29306 example this pragma could be placed in the @file{gnat.adc} file.
29308 @item Suppress checks selectively
29309 When you know that certain calls or instantiations in elaboration code cannot
29310 possibly lead to an elaboration error, and the binder nevertheless complains
29311 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
29312 elaboration circularities, it is possible to remove those warnings locally and
29313 obtain a program that will bind. Clearly this can be unsafe, and it is the
29314 responsibility of the programmer to make sure that the resulting program has no
29315 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
29316 used with different granularity to suppress warnings and break elaboration
29321 Place the pragma that names the called subprogram in the declarative part
29322 that contains the call.
29325 Place the pragma in the declarative part, without naming an entity. This
29326 disables warnings on all calls in the corresponding declarative region.
29329 Place the pragma in the package spec that declares the called subprogram,
29330 and name the subprogram. This disables warnings on all elaboration calls to
29334 Place the pragma in the package spec that declares the called subprogram,
29335 without naming any entity. This disables warnings on all elaboration calls to
29336 all subprograms declared in this spec.
29338 @item Use Pragma Elaborate
29339 As previously described in section @xref{Treatment of Pragma Elaborate},
29340 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
29341 that no elaboration checks are required on calls to the designated unit.
29342 There may be cases in which the caller knows that no transitive calls
29343 can occur, so that a @code{pragma Elaborate} will be sufficient in a
29344 case where @code{pragma Elaborate_All} would cause a circularity.
29348 These five cases are listed in order of decreasing safety, and therefore
29349 require increasing programmer care in their application. Consider the
29352 @smallexample @c adanocomment
29354 function F1 return Integer;
29359 function F2 return Integer;
29360 function Pure (x : integer) return integer;
29361 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
29362 -- pragma Suppress (Elaboration_Check); -- (4)
29366 package body Pack1 is
29367 function F1 return Integer is
29371 Val : integer := Pack2.Pure (11); -- Elab. call (1)
29374 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
29375 -- pragma Suppress(Elaboration_Check); -- (2)
29377 X1 := Pack2.F2 + 1; -- Elab. call (2)
29382 package body Pack2 is
29383 function F2 return Integer is
29387 function Pure (x : integer) return integer is
29389 return x ** 3 - 3 * x;
29393 with Pack1, Ada.Text_IO;
29396 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
29399 In the absence of any pragmas, an attempt to bind this program produces
29400 the following diagnostics:
29406 error: elaboration circularity detected
29407 info: "pack1 (body)" must be elaborated before "pack1 (body)"
29408 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
29409 info: recompile "pack1 (body)" with -gnatwl for full details
29410 info: "pack1 (body)"
29411 info: must be elaborated along with its spec:
29412 info: "pack1 (spec)"
29413 info: which is withed by:
29414 info: "pack2 (body)"
29415 info: which must be elaborated along with its spec:
29416 info: "pack2 (spec)"
29417 info: which is withed by:
29418 info: "pack1 (body)"
29421 The sources of the circularity are the two calls to @code{Pack2.Pure} and
29422 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
29423 F2 is safe, even though F2 calls F1, because the call appears after the
29424 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
29425 remove the warning on the call. It is also possible to use pragma (2)
29426 because there are no other potentially unsafe calls in the block.
29429 The call to @code{Pure} is safe because this function does not depend on the
29430 state of @code{Pack2}. Therefore any call to this function is safe, and it
29431 is correct to place pragma (3) in the corresponding package spec.
29434 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
29435 warnings on all calls to functions declared therein. Note that this is not
29436 necessarily safe, and requires more detailed examination of the subprogram
29437 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
29438 be already elaborated.
29442 It is hard to generalize on which of these four approaches should be
29443 taken. Obviously if it is possible to fix the program so that the default
29444 treatment works, this is preferable, but this may not always be practical.
29445 It is certainly simple enough to use
29447 but the danger in this case is that, even if the GNAT binder
29448 finds a correct elaboration order, it may not always do so,
29449 and certainly a binder from another Ada compiler might not. A
29450 combination of testing and analysis (for which the warnings generated
29453 switch can be useful) must be used to ensure that the program is free
29454 of errors. One switch that is useful in this testing is the
29455 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
29458 Normally the binder tries to find an order that has the best chance
29459 of avoiding elaboration problems. However, if this switch is used, the binder
29460 plays a devil's advocate role, and tries to choose the order that
29461 has the best chance of failing. If your program works even with this
29462 switch, then it has a better chance of being error free, but this is still
29465 For an example of this approach in action, consider the C-tests (executable
29466 tests) from the ACVC suite. If these are compiled and run with the default
29467 treatment, then all but one of them succeed without generating any error
29468 diagnostics from the binder. However, there is one test that fails, and
29469 this is not surprising, because the whole point of this test is to ensure
29470 that the compiler can handle cases where it is impossible to determine
29471 a correct order statically, and it checks that an exception is indeed
29472 raised at run time.
29474 This one test must be compiled and run using the
29476 switch, and then it passes. Alternatively, the entire suite can
29477 be run using this switch. It is never wrong to run with the dynamic
29478 elaboration switch if your code is correct, and we assume that the
29479 C-tests are indeed correct (it is less efficient, but efficiency is
29480 not a factor in running the ACVC tests.)
29482 @node Elaboration for Access-to-Subprogram Values
29483 @section Elaboration for Access-to-Subprogram Values
29484 @cindex Access-to-subprogram
29487 Access-to-subprogram types (introduced in Ada 95) complicate
29488 the handling of elaboration. The trouble is that it becomes
29489 impossible to tell at compile time which procedure
29490 is being called. This means that it is not possible for the binder
29491 to analyze the elaboration requirements in this case.
29493 If at the point at which the access value is created
29494 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
29495 the body of the subprogram is
29496 known to have been elaborated, then the access value is safe, and its use
29497 does not require a check. This may be achieved by appropriate arrangement
29498 of the order of declarations if the subprogram is in the current unit,
29499 or, if the subprogram is in another unit, by using pragma
29500 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
29501 on the referenced unit.
29503 If the referenced body is not known to have been elaborated at the point
29504 the access value is created, then any use of the access value must do a
29505 dynamic check, and this dynamic check will fail and raise a
29506 @code{Program_Error} exception if the body has not been elaborated yet.
29507 GNAT will generate the necessary checks, and in addition, if the
29509 switch is set, will generate warnings that such checks are required.
29511 The use of dynamic dispatching for tagged types similarly generates
29512 a requirement for dynamic checks, and premature calls to any primitive
29513 operation of a tagged type before the body of the operation has been
29514 elaborated, will result in the raising of @code{Program_Error}.
29516 @node Summary of Procedures for Elaboration Control
29517 @section Summary of Procedures for Elaboration Control
29518 @cindex Elaboration control
29521 First, compile your program with the default options, using none of
29522 the special elaboration control switches. If the binder successfully
29523 binds your program, then you can be confident that, apart from issues
29524 raised by the use of access-to-subprogram types and dynamic dispatching,
29525 the program is free of elaboration errors. If it is important that the
29526 program be portable, then use the
29528 switch to generate warnings about missing @code{Elaborate} or
29529 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29531 If the program fails to bind using the default static elaboration
29532 handling, then you can fix the program to eliminate the binder
29533 message, or recompile the entire program with the
29534 @option{-gnatE} switch to generate dynamic elaboration checks,
29535 and, if you are sure there really are no elaboration problems,
29536 use a global pragma @code{Suppress (Elaboration_Check)}.
29538 @node Other Elaboration Order Considerations
29539 @section Other Elaboration Order Considerations
29541 This section has been entirely concerned with the issue of finding a valid
29542 elaboration order, as defined by the Ada Reference Manual. In a case
29543 where several elaboration orders are valid, the task is to find one
29544 of the possible valid elaboration orders (and the static model in GNAT
29545 will ensure that this is achieved).
29547 The purpose of the elaboration rules in the Ada Reference Manual is to
29548 make sure that no entity is accessed before it has been elaborated. For
29549 a subprogram, this means that the spec and body must have been elaborated
29550 before the subprogram is called. For an object, this means that the object
29551 must have been elaborated before its value is read or written. A violation
29552 of either of these two requirements is an access before elaboration order,
29553 and this section has been all about avoiding such errors.
29555 In the case where more than one order of elaboration is possible, in the
29556 sense that access before elaboration errors are avoided, then any one of
29557 the orders is ``correct'' in the sense that it meets the requirements of
29558 the Ada Reference Manual, and no such error occurs.
29560 However, it may be the case for a given program, that there are
29561 constraints on the order of elaboration that come not from consideration
29562 of avoiding elaboration errors, but rather from extra-lingual logic
29563 requirements. Consider this example:
29565 @smallexample @c ada
29566 with Init_Constants;
29567 package Constants is
29572 package Init_Constants is
29573 procedure P; -- require a body
29574 end Init_Constants;
29577 package body Init_Constants is
29578 procedure P is begin null; end;
29582 end Init_Constants;
29586 Z : Integer := Constants.X + Constants.Y;
29590 with Text_IO; use Text_IO;
29593 Put_Line (Calc.Z'Img);
29598 In this example, there is more than one valid order of elaboration. For
29599 example both the following are correct orders:
29602 Init_Constants spec
29605 Init_Constants body
29610 Init_Constants spec
29611 Init_Constants body
29618 There is no language rule to prefer one or the other, both are correct
29619 from an order of elaboration point of view. But the programmatic effects
29620 of the two orders are very different. In the first, the elaboration routine
29621 of @code{Calc} initializes @code{Z} to zero, and then the main program
29622 runs with this value of zero. But in the second order, the elaboration
29623 routine of @code{Calc} runs after the body of Init_Constants has set
29624 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29627 One could perhaps by applying pretty clever non-artificial intelligence
29628 to the situation guess that it is more likely that the second order of
29629 elaboration is the one desired, but there is no formal linguistic reason
29630 to prefer one over the other. In fact in this particular case, GNAT will
29631 prefer the second order, because of the rule that bodies are elaborated
29632 as soon as possible, but it's just luck that this is what was wanted
29633 (if indeed the second order was preferred).
29635 If the program cares about the order of elaboration routines in a case like
29636 this, it is important to specify the order required. In this particular
29637 case, that could have been achieved by adding to the spec of Calc:
29639 @smallexample @c ada
29640 pragma Elaborate_All (Constants);
29644 which requires that the body (if any) and spec of @code{Constants},
29645 as well as the body and spec of any unit @code{with}'ed by
29646 @code{Constants} be elaborated before @code{Calc} is elaborated.
29648 Clearly no automatic method can always guess which alternative you require,
29649 and if you are working with legacy code that had constraints of this kind
29650 which were not properly specified by adding @code{Elaborate} or
29651 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29652 compilers can choose different orders.
29654 However, GNAT does attempt to diagnose the common situation where there
29655 are uninitialized variables in the visible part of a package spec, and the
29656 corresponding package body has an elaboration block that directly or
29657 indirectly initialized one or more of these variables. This is the situation
29658 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29659 a warning that suggests this addition if it detects this situation.
29661 The @code{gnatbind}
29662 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29663 out problems. This switch causes bodies to be elaborated as late as possible
29664 instead of as early as possible. In the example above, it would have forced
29665 the choice of the first elaboration order. If you get different results
29666 when using this switch, and particularly if one set of results is right,
29667 and one is wrong as far as you are concerned, it shows that you have some
29668 missing @code{Elaborate} pragmas. For the example above, we have the
29672 gnatmake -f -q main
29675 gnatmake -f -q main -bargs -p
29681 It is of course quite unlikely that both these results are correct, so
29682 it is up to you in a case like this to investigate the source of the
29683 difference, by looking at the two elaboration orders that are chosen,
29684 and figuring out which is correct, and then adding the necessary
29685 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29689 @c *******************************
29690 @node Conditional Compilation
29691 @appendix Conditional Compilation
29692 @c *******************************
29693 @cindex Conditional compilation
29696 It is often necessary to arrange for a single source program
29697 to serve multiple purposes, where it is compiled in different
29698 ways to achieve these different goals. Some examples of the
29699 need for this feature are
29702 @item Adapting a program to a different hardware environment
29703 @item Adapting a program to a different target architecture
29704 @item Turning debugging features on and off
29705 @item Arranging for a program to compile with different compilers
29709 In C, or C++, the typical approach would be to use the preprocessor
29710 that is defined as part of the language. The Ada language does not
29711 contain such a feature. This is not an oversight, but rather a very
29712 deliberate design decision, based on the experience that overuse of
29713 the preprocessing features in C and C++ can result in programs that
29714 are extremely difficult to maintain. For example, if we have ten
29715 switches that can be on or off, this means that there are a thousand
29716 separate programs, any one of which might not even be syntactically
29717 correct, and even if syntactically correct, the resulting program
29718 might not work correctly. Testing all combinations can quickly become
29721 Nevertheless, the need to tailor programs certainly exists, and in
29722 this Appendix we will discuss how this can
29723 be achieved using Ada in general, and GNAT in particular.
29726 * Use of Boolean Constants::
29727 * Debugging - A Special Case::
29728 * Conditionalizing Declarations::
29729 * Use of Alternative Implementations::
29733 @node Use of Boolean Constants
29734 @section Use of Boolean Constants
29737 In the case where the difference is simply which code
29738 sequence is executed, the cleanest solution is to use Boolean
29739 constants to control which code is executed.
29741 @smallexample @c ada
29743 FP_Initialize_Required : constant Boolean := True;
29745 if FP_Initialize_Required then
29752 Not only will the code inside the @code{if} statement not be executed if
29753 the constant Boolean is @code{False}, but it will also be completely
29754 deleted from the program.
29755 However, the code is only deleted after the @code{if} statement
29756 has been checked for syntactic and semantic correctness.
29757 (In contrast, with preprocessors the code is deleted before the
29758 compiler ever gets to see it, so it is not checked until the switch
29760 @cindex Preprocessors (contrasted with conditional compilation)
29762 Typically the Boolean constants will be in a separate package,
29765 @smallexample @c ada
29768 FP_Initialize_Required : constant Boolean := True;
29769 Reset_Available : constant Boolean := False;
29776 The @code{Config} package exists in multiple forms for the various targets,
29777 with an appropriate script selecting the version of @code{Config} needed.
29778 Then any other unit requiring conditional compilation can do a @code{with}
29779 of @code{Config} to make the constants visible.
29782 @node Debugging - A Special Case
29783 @section Debugging - A Special Case
29786 A common use of conditional code is to execute statements (for example
29787 dynamic checks, or output of intermediate results) under control of a
29788 debug switch, so that the debugging behavior can be turned on and off.
29789 This can be done using a Boolean constant to control whether the code
29792 @smallexample @c ada
29795 Put_Line ("got to the first stage!");
29803 @smallexample @c ada
29805 if Debugging and then Temperature > 999.0 then
29806 raise Temperature_Crazy;
29812 Since this is a common case, there are special features to deal with
29813 this in a convenient manner. For the case of tests, Ada 2005 has added
29814 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29815 @cindex pragma @code{Assert}
29816 on the @code{Assert} pragma that has always been available in GNAT, so this
29817 feature may be used with GNAT even if you are not using Ada 2005 features.
29818 The use of pragma @code{Assert} is described in
29819 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29820 example, the last test could be written:
29822 @smallexample @c ada
29823 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29829 @smallexample @c ada
29830 pragma Assert (Temperature <= 999.0);
29834 In both cases, if assertions are active and the temperature is excessive,
29835 the exception @code{Assert_Failure} will be raised, with the given string in
29836 the first case or a string indicating the location of the pragma in the second
29837 case used as the exception message.
29839 You can turn assertions on and off by using the @code{Assertion_Policy}
29841 @cindex pragma @code{Assertion_Policy}
29842 This is an Ada 2005 pragma which is implemented in all modes by
29843 GNAT, but only in the latest versions of GNAT which include Ada 2005
29844 capability. Alternatively, you can use the @option{-gnata} switch
29845 @cindex @option{-gnata} switch
29846 to enable assertions from the command line (this is recognized by all versions
29849 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29850 @code{Debug} can be used:
29851 @cindex pragma @code{Debug}
29853 @smallexample @c ada
29854 pragma Debug (Put_Line ("got to the first stage!"));
29858 If debug pragmas are enabled, the argument, which must be of the form of
29859 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29860 Only one call can be present, but of course a special debugging procedure
29861 containing any code you like can be included in the program and then
29862 called in a pragma @code{Debug} argument as needed.
29864 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29865 construct is that pragma @code{Debug} can appear in declarative contexts,
29866 such as at the very beginning of a procedure, before local declarations have
29869 Debug pragmas are enabled using either the @option{-gnata} switch that also
29870 controls assertions, or with a separate Debug_Policy pragma.
29871 @cindex pragma @code{Debug_Policy}
29872 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29873 in Ada 95 and Ada 83 programs as well), and is analogous to
29874 pragma @code{Assertion_Policy} to control assertions.
29876 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29877 and thus they can appear in @file{gnat.adc} if you are not using a
29878 project file, or in the file designated to contain configuration pragmas
29880 They then apply to all subsequent compilations. In practice the use of
29881 the @option{-gnata} switch is often the most convenient method of controlling
29882 the status of these pragmas.
29884 Note that a pragma is not a statement, so in contexts where a statement
29885 sequence is required, you can't just write a pragma on its own. You have
29886 to add a @code{null} statement.
29888 @smallexample @c ada
29891 @dots{} -- some statements
29893 pragma Assert (Num_Cases < 10);
29900 @node Conditionalizing Declarations
29901 @section Conditionalizing Declarations
29904 In some cases, it may be necessary to conditionalize declarations to meet
29905 different requirements. For example we might want a bit string whose length
29906 is set to meet some hardware message requirement.
29908 In some cases, it may be possible to do this using declare blocks controlled
29909 by conditional constants:
29911 @smallexample @c ada
29913 if Small_Machine then
29915 X : Bit_String (1 .. 10);
29921 X : Large_Bit_String (1 .. 1000);
29930 Note that in this approach, both declarations are analyzed by the
29931 compiler so this can only be used where both declarations are legal,
29932 even though one of them will not be used.
29934 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29935 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29936 that are parameterized by these constants. For example
29938 @smallexample @c ada
29941 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29947 If @code{Bits_Per_Word} is set to 32, this generates either
29949 @smallexample @c ada
29952 Field1 at 0 range 0 .. 32;
29958 for the big endian case, or
29960 @smallexample @c ada
29963 Field1 at 0 range 10 .. 32;
29969 for the little endian case. Since a powerful subset of Ada expression
29970 notation is usable for creating static constants, clever use of this
29971 feature can often solve quite difficult problems in conditionalizing
29972 compilation (note incidentally that in Ada 95, the little endian
29973 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29974 need to define this one yourself).
29977 @node Use of Alternative Implementations
29978 @section Use of Alternative Implementations
29981 In some cases, none of the approaches described above are adequate. This
29982 can occur for example if the set of declarations required is radically
29983 different for two different configurations.
29985 In this situation, the official Ada way of dealing with conditionalizing
29986 such code is to write separate units for the different cases. As long as
29987 this does not result in excessive duplication of code, this can be done
29988 without creating maintenance problems. The approach is to share common
29989 code as far as possible, and then isolate the code and declarations
29990 that are different. Subunits are often a convenient method for breaking
29991 out a piece of a unit that is to be conditionalized, with separate files
29992 for different versions of the subunit for different targets, where the
29993 build script selects the right one to give to the compiler.
29994 @cindex Subunits (and conditional compilation)
29996 As an example, consider a situation where a new feature in Ada 2005
29997 allows something to be done in a really nice way. But your code must be able
29998 to compile with an Ada 95 compiler. Conceptually you want to say:
30000 @smallexample @c ada
30003 @dots{} neat Ada 2005 code
30005 @dots{} not quite as neat Ada 95 code
30011 where @code{Ada_2005} is a Boolean constant.
30013 But this won't work when @code{Ada_2005} is set to @code{False},
30014 since the @code{then} clause will be illegal for an Ada 95 compiler.
30015 (Recall that although such unreachable code would eventually be deleted
30016 by the compiler, it still needs to be legal. If it uses features
30017 introduced in Ada 2005, it will be illegal in Ada 95.)
30019 So instead we write
30021 @smallexample @c ada
30022 procedure Insert is separate;
30026 Then we have two files for the subunit @code{Insert}, with the two sets of
30028 If the package containing this is called @code{File_Queries}, then we might
30032 @item @file{file_queries-insert-2005.adb}
30033 @item @file{file_queries-insert-95.adb}
30037 and the build script renames the appropriate file to
30040 file_queries-insert.adb
30044 and then carries out the compilation.
30046 This can also be done with project files' naming schemes. For example:
30048 @smallexample @c project
30049 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
30053 Note also that with project files it is desirable to use a different extension
30054 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
30055 conflict may arise through another commonly used feature: to declare as part
30056 of the project a set of directories containing all the sources obeying the
30057 default naming scheme.
30059 The use of alternative units is certainly feasible in all situations,
30060 and for example the Ada part of the GNAT run-time is conditionalized
30061 based on the target architecture using this approach. As a specific example,
30062 consider the implementation of the AST feature in VMS. There is one
30070 which is the same for all architectures, and three bodies:
30074 used for all non-VMS operating systems
30075 @item s-asthan-vms-alpha.adb
30076 used for VMS on the Alpha
30077 @item s-asthan-vms-ia64.adb
30078 used for VMS on the ia64
30082 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
30083 this operating system feature is not available, and the two remaining
30084 versions interface with the corresponding versions of VMS to provide
30085 VMS-compatible AST handling. The GNAT build script knows the architecture
30086 and operating system, and automatically selects the right version,
30087 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
30089 Another style for arranging alternative implementations is through Ada's
30090 access-to-subprogram facility.
30091 In case some functionality is to be conditionally included,
30092 you can declare an access-to-procedure variable @code{Ref} that is initialized
30093 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
30095 In some library package, set @code{Ref} to @code{Proc'Access} for some
30096 procedure @code{Proc} that performs the relevant processing.
30097 The initialization only occurs if the library package is included in the
30099 The same idea can also be implemented using tagged types and dispatching
30103 @node Preprocessing
30104 @section Preprocessing
30105 @cindex Preprocessing
30108 Although it is quite possible to conditionalize code without the use of
30109 C-style preprocessing, as described earlier in this section, it is
30110 nevertheless convenient in some cases to use the C approach. Moreover,
30111 older Ada compilers have often provided some preprocessing capability,
30112 so legacy code may depend on this approach, even though it is not
30115 To accommodate such use, GNAT provides a preprocessor (modeled to a large
30116 extent on the various preprocessors that have been used
30117 with legacy code on other compilers, to enable easier transition).
30119 The preprocessor may be used in two separate modes. It can be used quite
30120 separately from the compiler, to generate a separate output source file
30121 that is then fed to the compiler as a separate step. This is the
30122 @code{gnatprep} utility, whose use is fully described in
30123 @ref{Preprocessing Using gnatprep}.
30124 @cindex @code{gnatprep}
30126 The preprocessing language allows such constructs as
30130 #if DEBUG or PRIORITY > 4 then
30131 bunch of declarations
30133 completely different bunch of declarations
30139 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
30140 defined either on the command line or in a separate file.
30142 The other way of running the preprocessor is even closer to the C style and
30143 often more convenient. In this approach the preprocessing is integrated into
30144 the compilation process. The compiler is fed the preprocessor input which
30145 includes @code{#if} lines etc, and then the compiler carries out the
30146 preprocessing internally and processes the resulting output.
30147 For more details on this approach, see @ref{Integrated Preprocessing}.
30150 @c *******************************
30151 @node Inline Assembler
30152 @appendix Inline Assembler
30153 @c *******************************
30156 If you need to write low-level software that interacts directly
30157 with the hardware, Ada provides two ways to incorporate assembly
30158 language code into your program. First, you can import and invoke
30159 external routines written in assembly language, an Ada feature fully
30160 supported by GNAT@. However, for small sections of code it may be simpler
30161 or more efficient to include assembly language statements directly
30162 in your Ada source program, using the facilities of the implementation-defined
30163 package @code{System.Machine_Code}, which incorporates the gcc
30164 Inline Assembler. The Inline Assembler approach offers a number of advantages,
30165 including the following:
30168 @item No need to use non-Ada tools
30169 @item Consistent interface over different targets
30170 @item Automatic usage of the proper calling conventions
30171 @item Access to Ada constants and variables
30172 @item Definition of intrinsic routines
30173 @item Possibility of inlining a subprogram comprising assembler code
30174 @item Code optimizer can take Inline Assembler code into account
30177 This chapter presents a series of examples to show you how to use
30178 the Inline Assembler. Although it focuses on the Intel x86,
30179 the general approach applies also to other processors.
30180 It is assumed that you are familiar with Ada
30181 and with assembly language programming.
30184 * Basic Assembler Syntax::
30185 * A Simple Example of Inline Assembler::
30186 * Output Variables in Inline Assembler::
30187 * Input Variables in Inline Assembler::
30188 * Inlining Inline Assembler Code::
30189 * Other Asm Functionality::
30192 @c ---------------------------------------------------------------------------
30193 @node Basic Assembler Syntax
30194 @section Basic Assembler Syntax
30197 The assembler used by GNAT and gcc is based not on the Intel assembly
30198 language, but rather on a language that descends from the AT&T Unix
30199 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
30200 The following table summarizes the main features of @emph{as} syntax
30201 and points out the differences from the Intel conventions.
30202 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
30203 pre-processor) documentation for further information.
30206 @item Register names
30207 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
30209 Intel: No extra punctuation; for example @code{eax}
30211 @item Immediate operand
30212 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
30214 Intel: No extra punctuation; for example @code{4}
30217 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
30219 Intel: No extra punctuation; for example @code{loc}
30221 @item Memory contents
30222 gcc / @emph{as}: No extra punctuation; for example @code{loc}
30224 Intel: Square brackets; for example @code{[loc]}
30226 @item Register contents
30227 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
30229 Intel: Square brackets; for example @code{[eax]}
30231 @item Hexadecimal numbers
30232 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
30234 Intel: Trailing ``h''; for example @code{A0h}
30237 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
30240 Intel: Implicit, deduced by assembler; for example @code{mov}
30242 @item Instruction repetition
30243 gcc / @emph{as}: Split into two lines; for example
30249 Intel: Keep on one line; for example @code{rep stosl}
30251 @item Order of operands
30252 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
30254 Intel: Destination first; for example @code{mov eax, 4}
30257 @c ---------------------------------------------------------------------------
30258 @node A Simple Example of Inline Assembler
30259 @section A Simple Example of Inline Assembler
30262 The following example will generate a single assembly language statement,
30263 @code{nop}, which does nothing. Despite its lack of run-time effect,
30264 the example will be useful in illustrating the basics of
30265 the Inline Assembler facility.
30267 @smallexample @c ada
30269 with System.Machine_Code; use System.Machine_Code;
30270 procedure Nothing is
30277 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
30278 here it takes one parameter, a @emph{template string} that must be a static
30279 expression and that will form the generated instruction.
30280 @code{Asm} may be regarded as a compile-time procedure that parses
30281 the template string and additional parameters (none here),
30282 from which it generates a sequence of assembly language instructions.
30284 The examples in this chapter will illustrate several of the forms
30285 for invoking @code{Asm}; a complete specification of the syntax
30286 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
30289 Under the standard GNAT conventions, the @code{Nothing} procedure
30290 should be in a file named @file{nothing.adb}.
30291 You can build the executable in the usual way:
30295 However, the interesting aspect of this example is not its run-time behavior
30296 but rather the generated assembly code.
30297 To see this output, invoke the compiler as follows:
30299 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
30301 where the options are:
30305 compile only (no bind or link)
30307 generate assembler listing
30308 @item -fomit-frame-pointer
30309 do not set up separate stack frames
30311 do not add runtime checks
30314 This gives a human-readable assembler version of the code. The resulting
30315 file will have the same name as the Ada source file, but with a @code{.s}
30316 extension. In our example, the file @file{nothing.s} has the following
30321 .file "nothing.adb"
30323 ___gnu_compiled_ada:
30326 .globl __ada_nothing
30338 The assembly code you included is clearly indicated by
30339 the compiler, between the @code{#APP} and @code{#NO_APP}
30340 delimiters. The character before the 'APP' and 'NOAPP'
30341 can differ on different targets. For example, GNU/Linux uses '#APP' while
30342 on NT you will see '/APP'.
30344 If you make a mistake in your assembler code (such as using the
30345 wrong size modifier, or using a wrong operand for the instruction) GNAT
30346 will report this error in a temporary file, which will be deleted when
30347 the compilation is finished. Generating an assembler file will help
30348 in such cases, since you can assemble this file separately using the
30349 @emph{as} assembler that comes with gcc.
30351 Assembling the file using the command
30354 as @file{nothing.s}
30357 will give you error messages whose lines correspond to the assembler
30358 input file, so you can easily find and correct any mistakes you made.
30359 If there are no errors, @emph{as} will generate an object file
30360 @file{nothing.out}.
30362 @c ---------------------------------------------------------------------------
30363 @node Output Variables in Inline Assembler
30364 @section Output Variables in Inline Assembler
30367 The examples in this section, showing how to access the processor flags,
30368 illustrate how to specify the destination operands for assembly language
30371 @smallexample @c ada
30373 with Interfaces; use Interfaces;
30374 with Ada.Text_IO; use Ada.Text_IO;
30375 with System.Machine_Code; use System.Machine_Code;
30376 procedure Get_Flags is
30377 Flags : Unsigned_32;
30380 Asm ("pushfl" & LF & HT & -- push flags on stack
30381 "popl %%eax" & LF & HT & -- load eax with flags
30382 "movl %%eax, %0", -- store flags in variable
30383 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30384 Put_Line ("Flags register:" & Flags'Img);
30389 In order to have a nicely aligned assembly listing, we have separated
30390 multiple assembler statements in the Asm template string with linefeed
30391 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
30392 The resulting section of the assembly output file is:
30399 movl %eax, -40(%ebp)
30404 It would have been legal to write the Asm invocation as:
30407 Asm ("pushfl popl %%eax movl %%eax, %0")
30410 but in the generated assembler file, this would come out as:
30414 pushfl popl %eax movl %eax, -40(%ebp)
30418 which is not so convenient for the human reader.
30420 We use Ada comments
30421 at the end of each line to explain what the assembler instructions
30422 actually do. This is a useful convention.
30424 When writing Inline Assembler instructions, you need to precede each register
30425 and variable name with a percent sign. Since the assembler already requires
30426 a percent sign at the beginning of a register name, you need two consecutive
30427 percent signs for such names in the Asm template string, thus @code{%%eax}.
30428 In the generated assembly code, one of the percent signs will be stripped off.
30430 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
30431 variables: operands you later define using @code{Input} or @code{Output}
30432 parameters to @code{Asm}.
30433 An output variable is illustrated in
30434 the third statement in the Asm template string:
30438 The intent is to store the contents of the eax register in a variable that can
30439 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
30440 necessarily work, since the compiler might optimize by using a register
30441 to hold Flags, and the expansion of the @code{movl} instruction would not be
30442 aware of this optimization. The solution is not to store the result directly
30443 but rather to advise the compiler to choose the correct operand form;
30444 that is the purpose of the @code{%0} output variable.
30446 Information about the output variable is supplied in the @code{Outputs}
30447 parameter to @code{Asm}:
30449 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30452 The output is defined by the @code{Asm_Output} attribute of the target type;
30453 the general format is
30455 Type'Asm_Output (constraint_string, variable_name)
30458 The constraint string directs the compiler how
30459 to store/access the associated variable. In the example
30461 Unsigned_32'Asm_Output ("=m", Flags);
30463 the @code{"m"} (memory) constraint tells the compiler that the variable
30464 @code{Flags} should be stored in a memory variable, thus preventing
30465 the optimizer from keeping it in a register. In contrast,
30467 Unsigned_32'Asm_Output ("=r", Flags);
30469 uses the @code{"r"} (register) constraint, telling the compiler to
30470 store the variable in a register.
30472 If the constraint is preceded by the equal character (@strong{=}), it tells
30473 the compiler that the variable will be used to store data into it.
30475 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
30476 allowing the optimizer to choose whatever it deems best.
30478 There are a fairly large number of constraints, but the ones that are
30479 most useful (for the Intel x86 processor) are the following:
30485 global (i.e.@: can be stored anywhere)
30503 use one of eax, ebx, ecx or edx
30505 use one of eax, ebx, ecx, edx, esi or edi
30508 The full set of constraints is described in the gcc and @emph{as}
30509 documentation; note that it is possible to combine certain constraints
30510 in one constraint string.
30512 You specify the association of an output variable with an assembler operand
30513 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30515 @smallexample @c ada
30517 Asm ("pushfl" & LF & HT & -- push flags on stack
30518 "popl %%eax" & LF & HT & -- load eax with flags
30519 "movl %%eax, %0", -- store flags in variable
30520 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30524 @code{%0} will be replaced in the expanded code by the appropriate operand,
30526 the compiler decided for the @code{Flags} variable.
30528 In general, you may have any number of output variables:
30531 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30533 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30534 of @code{Asm_Output} attributes
30538 @smallexample @c ada
30540 Asm ("movl %%eax, %0" & LF & HT &
30541 "movl %%ebx, %1" & LF & HT &
30543 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30544 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30545 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30549 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30550 in the Ada program.
30552 As a variation on the @code{Get_Flags} example, we can use the constraints
30553 string to direct the compiler to store the eax register into the @code{Flags}
30554 variable, instead of including the store instruction explicitly in the
30555 @code{Asm} template string:
30557 @smallexample @c ada
30559 with Interfaces; use Interfaces;
30560 with Ada.Text_IO; use Ada.Text_IO;
30561 with System.Machine_Code; use System.Machine_Code;
30562 procedure Get_Flags_2 is
30563 Flags : Unsigned_32;
30566 Asm ("pushfl" & LF & HT & -- push flags on stack
30567 "popl %%eax", -- save flags in eax
30568 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30569 Put_Line ("Flags register:" & Flags'Img);
30575 The @code{"a"} constraint tells the compiler that the @code{Flags}
30576 variable will come from the eax register. Here is the resulting code:
30584 movl %eax,-40(%ebp)
30589 The compiler generated the store of eax into Flags after
30590 expanding the assembler code.
30592 Actually, there was no need to pop the flags into the eax register;
30593 more simply, we could just pop the flags directly into the program variable:
30595 @smallexample @c ada
30597 with Interfaces; use Interfaces;
30598 with Ada.Text_IO; use Ada.Text_IO;
30599 with System.Machine_Code; use System.Machine_Code;
30600 procedure Get_Flags_3 is
30601 Flags : Unsigned_32;
30604 Asm ("pushfl" & LF & HT & -- push flags on stack
30605 "pop %0", -- save flags in Flags
30606 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30607 Put_Line ("Flags register:" & Flags'Img);
30612 @c ---------------------------------------------------------------------------
30613 @node Input Variables in Inline Assembler
30614 @section Input Variables in Inline Assembler
30617 The example in this section illustrates how to specify the source operands
30618 for assembly language statements.
30619 The program simply increments its input value by 1:
30621 @smallexample @c ada
30623 with Interfaces; use Interfaces;
30624 with Ada.Text_IO; use Ada.Text_IO;
30625 with System.Machine_Code; use System.Machine_Code;
30626 procedure Increment is
30628 function Incr (Value : Unsigned_32) return Unsigned_32 is
30629 Result : Unsigned_32;
30632 Inputs => Unsigned_32'Asm_Input ("a", Value),
30633 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30637 Value : Unsigned_32;
30641 Put_Line ("Value before is" & Value'Img);
30642 Value := Incr (Value);
30643 Put_Line ("Value after is" & Value'Img);
30648 The @code{Outputs} parameter to @code{Asm} specifies
30649 that the result will be in the eax register and that it is to be stored
30650 in the @code{Result} variable.
30652 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30653 but with an @code{Asm_Input} attribute.
30654 The @code{"="} constraint, indicating an output value, is not present.
30656 You can have multiple input variables, in the same way that you can have more
30657 than one output variable.
30659 The parameter count (%0, %1) etc, now starts at the first input
30660 statement, and continues with the output statements.
30661 When both parameters use the same variable, the
30662 compiler will treat them as the same %n operand, which is the case here.
30664 Just as the @code{Outputs} parameter causes the register to be stored into the
30665 target variable after execution of the assembler statements, so does the
30666 @code{Inputs} parameter cause its variable to be loaded into the register
30667 before execution of the assembler statements.
30669 Thus the effect of the @code{Asm} invocation is:
30671 @item load the 32-bit value of @code{Value} into eax
30672 @item execute the @code{incl %eax} instruction
30673 @item store the contents of eax into the @code{Result} variable
30676 The resulting assembler file (with @option{-O2} optimization) contains:
30679 _increment__incr.1:
30692 @c ---------------------------------------------------------------------------
30693 @node Inlining Inline Assembler Code
30694 @section Inlining Inline Assembler Code
30697 For a short subprogram such as the @code{Incr} function in the previous
30698 section, the overhead of the call and return (creating / deleting the stack
30699 frame) can be significant, compared to the amount of code in the subprogram
30700 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30701 which directs the compiler to expand invocations of the subprogram at the
30702 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30703 Here is the resulting program:
30705 @smallexample @c ada
30707 with Interfaces; use Interfaces;
30708 with Ada.Text_IO; use Ada.Text_IO;
30709 with System.Machine_Code; use System.Machine_Code;
30710 procedure Increment_2 is
30712 function Incr (Value : Unsigned_32) return Unsigned_32 is
30713 Result : Unsigned_32;
30716 Inputs => Unsigned_32'Asm_Input ("a", Value),
30717 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30720 pragma Inline (Increment);
30722 Value : Unsigned_32;
30726 Put_Line ("Value before is" & Value'Img);
30727 Value := Increment (Value);
30728 Put_Line ("Value after is" & Value'Img);
30733 Compile the program with both optimization (@option{-O2}) and inlining
30734 (@option{-gnatn}) enabled.
30736 The @code{Incr} function is still compiled as usual, but at the
30737 point in @code{Increment} where our function used to be called:
30742 call _increment__incr.1
30747 the code for the function body directly appears:
30760 thus saving the overhead of stack frame setup and an out-of-line call.
30762 @c ---------------------------------------------------------------------------
30763 @node Other Asm Functionality
30764 @section Other @code{Asm} Functionality
30767 This section describes two important parameters to the @code{Asm}
30768 procedure: @code{Clobber}, which identifies register usage;
30769 and @code{Volatile}, which inhibits unwanted optimizations.
30772 * The Clobber Parameter::
30773 * The Volatile Parameter::
30776 @c ---------------------------------------------------------------------------
30777 @node The Clobber Parameter
30778 @subsection The @code{Clobber} Parameter
30781 One of the dangers of intermixing assembly language and a compiled language
30782 such as Ada is that the compiler needs to be aware of which registers are
30783 being used by the assembly code. In some cases, such as the earlier examples,
30784 the constraint string is sufficient to indicate register usage (e.g.,
30786 the eax register). But more generally, the compiler needs an explicit
30787 identification of the registers that are used by the Inline Assembly
30790 Using a register that the compiler doesn't know about
30791 could be a side effect of an instruction (like @code{mull}
30792 storing its result in both eax and edx).
30793 It can also arise from explicit register usage in your
30794 assembly code; for example:
30797 Asm ("movl %0, %%ebx" & LF & HT &
30799 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30800 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30804 where the compiler (since it does not analyze the @code{Asm} template string)
30805 does not know you are using the ebx register.
30807 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30808 to identify the registers that will be used by your assembly code:
30812 Asm ("movl %0, %%ebx" & LF & HT &
30814 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30815 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30820 The Clobber parameter is a static string expression specifying the
30821 register(s) you are using. Note that register names are @emph{not} prefixed
30822 by a percent sign. Also, if more than one register is used then their names
30823 are separated by commas; e.g., @code{"eax, ebx"}
30825 The @code{Clobber} parameter has several additional uses:
30827 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30828 @item Use ``register'' name @code{memory} if you changed a memory location
30831 @c ---------------------------------------------------------------------------
30832 @node The Volatile Parameter
30833 @subsection The @code{Volatile} Parameter
30834 @cindex Volatile parameter
30837 Compiler optimizations in the presence of Inline Assembler may sometimes have
30838 unwanted effects. For example, when an @code{Asm} invocation with an input
30839 variable is inside a loop, the compiler might move the loading of the input
30840 variable outside the loop, regarding it as a one-time initialization.
30842 If this effect is not desired, you can disable such optimizations by setting
30843 the @code{Volatile} parameter to @code{True}; for example:
30845 @smallexample @c ada
30847 Asm ("movl %0, %%ebx" & LF & HT &
30849 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30850 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30856 By default, @code{Volatile} is set to @code{False} unless there is no
30857 @code{Outputs} parameter.
30859 Although setting @code{Volatile} to @code{True} prevents unwanted
30860 optimizations, it will also disable other optimizations that might be
30861 important for efficiency. In general, you should set @code{Volatile}
30862 to @code{True} only if the compiler's optimizations have created
30864 @c END OF INLINE ASSEMBLER CHAPTER
30865 @c ===============================
30867 @c ***********************************
30868 @c * Compatibility and Porting Guide *
30869 @c ***********************************
30870 @node Compatibility and Porting Guide
30871 @appendix Compatibility and Porting Guide
30874 This chapter describes the compatibility issues that may arise between
30875 GNAT and other Ada compilation systems (including those for Ada 83),
30876 and shows how GNAT can expedite porting
30877 applications developed in other Ada environments.
30880 * Compatibility with Ada 83::
30881 * Compatibility between Ada 95 and Ada 2005::
30882 * Implementation-dependent characteristics::
30883 * Compatibility with Other Ada Systems::
30884 * Representation Clauses::
30886 @c Brief section is only in non-VMS version
30887 @c Full chapter is in VMS version
30888 * Compatibility with HP Ada 83::
30891 * Transitioning to 64-Bit GNAT for OpenVMS::
30895 @node Compatibility with Ada 83
30896 @section Compatibility with Ada 83
30897 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30900 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30901 particular, the design intention was that the difficulties associated
30902 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30903 that occur when moving from one Ada 83 system to another.
30905 However, there are a number of points at which there are minor
30906 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30907 full details of these issues,
30908 and should be consulted for a complete treatment.
30910 following subsections treat the most likely issues to be encountered.
30913 * Legal Ada 83 programs that are illegal in Ada 95::
30914 * More deterministic semantics::
30915 * Changed semantics::
30916 * Other language compatibility issues::
30919 @node Legal Ada 83 programs that are illegal in Ada 95
30920 @subsection Legal Ada 83 programs that are illegal in Ada 95
30922 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30923 Ada 95 and thus also in Ada 2005:
30926 @item Character literals
30927 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30928 @code{Wide_Character} as a new predefined character type, some uses of
30929 character literals that were legal in Ada 83 are illegal in Ada 95.
30931 @smallexample @c ada
30932 for Char in 'A' .. 'Z' loop @dots{} end loop;
30936 The problem is that @code{'A'} and @code{'Z'} could be from either
30937 @code{Character} or @code{Wide_Character}. The simplest correction
30938 is to make the type explicit; e.g.:
30939 @smallexample @c ada
30940 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30943 @item New reserved words
30944 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30945 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30946 Existing Ada 83 code using any of these identifiers must be edited to
30947 use some alternative name.
30949 @item Freezing rules
30950 The rules in Ada 95 are slightly different with regard to the point at
30951 which entities are frozen, and representation pragmas and clauses are
30952 not permitted past the freeze point. This shows up most typically in
30953 the form of an error message complaining that a representation item
30954 appears too late, and the appropriate corrective action is to move
30955 the item nearer to the declaration of the entity to which it refers.
30957 A particular case is that representation pragmas
30960 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30962 cannot be applied to a subprogram body. If necessary, a separate subprogram
30963 declaration must be introduced to which the pragma can be applied.
30965 @item Optional bodies for library packages
30966 In Ada 83, a package that did not require a package body was nevertheless
30967 allowed to have one. This lead to certain surprises in compiling large
30968 systems (situations in which the body could be unexpectedly ignored by the
30969 binder). In Ada 95, if a package does not require a body then it is not
30970 permitted to have a body. To fix this problem, simply remove a redundant
30971 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30972 into the spec that makes the body required. One approach is to add a private
30973 part to the package declaration (if necessary), and define a parameterless
30974 procedure called @code{Requires_Body}, which must then be given a dummy
30975 procedure body in the package body, which then becomes required.
30976 Another approach (assuming that this does not introduce elaboration
30977 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30978 since one effect of this pragma is to require the presence of a package body.
30980 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30981 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30982 @code{Constraint_Error}.
30983 This means that it is illegal to have separate exception handlers for
30984 the two exceptions. The fix is simply to remove the handler for the
30985 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30986 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30988 @item Indefinite subtypes in generics
30989 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30990 as the actual for a generic formal private type, but then the instantiation
30991 would be illegal if there were any instances of declarations of variables
30992 of this type in the generic body. In Ada 95, to avoid this clear violation
30993 of the methodological principle known as the ``contract model'',
30994 the generic declaration explicitly indicates whether
30995 or not such instantiations are permitted. If a generic formal parameter
30996 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30997 type name, then it can be instantiated with indefinite types, but no
30998 stand-alone variables can be declared of this type. Any attempt to declare
30999 such a variable will result in an illegality at the time the generic is
31000 declared. If the @code{(<>)} notation is not used, then it is illegal
31001 to instantiate the generic with an indefinite type.
31002 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
31003 It will show up as a compile time error, and
31004 the fix is usually simply to add the @code{(<>)} to the generic declaration.
31007 @node More deterministic semantics
31008 @subsection More deterministic semantics
31012 Conversions from real types to integer types round away from 0. In Ada 83
31013 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
31014 implementation freedom was intended to support unbiased rounding in
31015 statistical applications, but in practice it interfered with portability.
31016 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
31017 is required. Numeric code may be affected by this change in semantics.
31018 Note, though, that this issue is no worse than already existed in Ada 83
31019 when porting code from one vendor to another.
31022 The Real-Time Annex introduces a set of policies that define the behavior of
31023 features that were implementation dependent in Ada 83, such as the order in
31024 which open select branches are executed.
31027 @node Changed semantics
31028 @subsection Changed semantics
31031 The worst kind of incompatibility is one where a program that is legal in
31032 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
31033 possible in Ada 83. Fortunately this is extremely rare, but the one
31034 situation that you should be alert to is the change in the predefined type
31035 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
31038 @item Range of type @code{Character}
31039 The range of @code{Standard.Character} is now the full 256 characters
31040 of Latin-1, whereas in most Ada 83 implementations it was restricted
31041 to 128 characters. Although some of the effects of
31042 this change will be manifest in compile-time rejection of legal
31043 Ada 83 programs it is possible for a working Ada 83 program to have
31044 a different effect in Ada 95, one that was not permitted in Ada 83.
31045 As an example, the expression
31046 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
31047 delivers @code{255} as its value.
31048 In general, you should look at the logic of any
31049 character-processing Ada 83 program and see whether it needs to be adapted
31050 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
31051 character handling package that may be relevant if code needs to be adapted
31052 to account for the additional Latin-1 elements.
31053 The desirable fix is to
31054 modify the program to accommodate the full character set, but in some cases
31055 it may be convenient to define a subtype or derived type of Character that
31056 covers only the restricted range.
31060 @node Other language compatibility issues
31061 @subsection Other language compatibility issues
31064 @item @option{-gnat83} switch
31065 All implementations of GNAT provide a switch that causes GNAT to operate
31066 in Ada 83 mode. In this mode, some but not all compatibility problems
31067 of the type described above are handled automatically. For example, the
31068 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
31069 as identifiers as in Ada 83.
31071 in practice, it is usually advisable to make the necessary modifications
31072 to the program to remove the need for using this switch.
31073 See @ref{Compiling Different Versions of Ada}.
31075 @item Support for removed Ada 83 pragmas and attributes
31076 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
31077 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
31078 compilers are allowed, but not required, to implement these missing
31079 elements. In contrast with some other compilers, GNAT implements all
31080 such pragmas and attributes, eliminating this compatibility concern. These
31081 include @code{pragma Interface} and the floating point type attributes
31082 (@code{Emax}, @code{Mantissa}, etc.), among other items.
31086 @node Compatibility between Ada 95 and Ada 2005
31087 @section Compatibility between Ada 95 and Ada 2005
31088 @cindex Compatibility between Ada 95 and Ada 2005
31091 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
31092 a number of incompatibilities. Several are enumerated below;
31093 for a complete description please see the
31094 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
31095 @cite{Rationale for Ada 2005}.
31098 @item New reserved words.
31099 The words @code{interface}, @code{overriding} and @code{synchronized} are
31100 reserved in Ada 2005.
31101 A pre-Ada 2005 program that uses any of these as an identifier will be
31104 @item New declarations in predefined packages.
31105 A number of packages in the predefined environment contain new declarations:
31106 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
31107 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
31108 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
31109 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
31110 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
31111 If an Ada 95 program does a @code{with} and @code{use} of any of these
31112 packages, the new declarations may cause name clashes.
31114 @item Access parameters.
31115 A nondispatching subprogram with an access parameter cannot be renamed
31116 as a dispatching operation. This was permitted in Ada 95.
31118 @item Access types, discriminants, and constraints.
31119 Rule changes in this area have led to some incompatibilities; for example,
31120 constrained subtypes of some access types are not permitted in Ada 2005.
31122 @item Aggregates for limited types.
31123 The allowance of aggregates for limited types in Ada 2005 raises the
31124 possibility of ambiguities in legal Ada 95 programs, since additional types
31125 now need to be considered in expression resolution.
31127 @item Fixed-point multiplication and division.
31128 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
31129 were legal in Ada 95 and invoked the predefined versions of these operations,
31131 The ambiguity may be resolved either by applying a type conversion to the
31132 expression, or by explicitly invoking the operation from package
31135 @item Return-by-reference types.
31136 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
31137 can declare a function returning a value from an anonymous access type.
31141 @node Implementation-dependent characteristics
31142 @section Implementation-dependent characteristics
31144 Although the Ada language defines the semantics of each construct as
31145 precisely as practical, in some situations (for example for reasons of
31146 efficiency, or where the effect is heavily dependent on the host or target
31147 platform) the implementation is allowed some freedom. In porting Ada 83
31148 code to GNAT, you need to be aware of whether / how the existing code
31149 exercised such implementation dependencies. Such characteristics fall into
31150 several categories, and GNAT offers specific support in assisting the
31151 transition from certain Ada 83 compilers.
31154 * Implementation-defined pragmas::
31155 * Implementation-defined attributes::
31157 * Elaboration order::
31158 * Target-specific aspects::
31161 @node Implementation-defined pragmas
31162 @subsection Implementation-defined pragmas
31165 Ada compilers are allowed to supplement the language-defined pragmas, and
31166 these are a potential source of non-portability. All GNAT-defined pragmas
31167 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
31168 Reference Manual}, and these include several that are specifically
31169 intended to correspond to other vendors' Ada 83 pragmas.
31170 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
31171 For compatibility with HP Ada 83, GNAT supplies the pragmas
31172 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
31173 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
31174 and @code{Volatile}.
31175 Other relevant pragmas include @code{External} and @code{Link_With}.
31176 Some vendor-specific
31177 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
31179 avoiding compiler rejection of units that contain such pragmas; they are not
31180 relevant in a GNAT context and hence are not otherwise implemented.
31182 @node Implementation-defined attributes
31183 @subsection Implementation-defined attributes
31185 Analogous to pragmas, the set of attributes may be extended by an
31186 implementation. All GNAT-defined attributes are described in
31187 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
31188 Manual}, and these include several that are specifically intended
31189 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
31190 the attribute @code{VADS_Size} may be useful. For compatibility with HP
31191 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
31195 @subsection Libraries
31197 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
31198 code uses vendor-specific libraries then there are several ways to manage
31199 this in Ada 95 or Ada 2005:
31202 If the source code for the libraries (specs and bodies) are
31203 available, then the libraries can be migrated in the same way as the
31206 If the source code for the specs but not the bodies are
31207 available, then you can reimplement the bodies.
31209 Some features introduced by Ada 95 obviate the need for library support. For
31210 example most Ada 83 vendors supplied a package for unsigned integers. The
31211 Ada 95 modular type feature is the preferred way to handle this need, so
31212 instead of migrating or reimplementing the unsigned integer package it may
31213 be preferable to retrofit the application using modular types.
31216 @node Elaboration order
31217 @subsection Elaboration order
31219 The implementation can choose any elaboration order consistent with the unit
31220 dependency relationship. This freedom means that some orders can result in
31221 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
31222 to invoke a subprogram its body has been elaborated, or to instantiate a
31223 generic before the generic body has been elaborated. By default GNAT
31224 attempts to choose a safe order (one that will not encounter access before
31225 elaboration problems) by implicitly inserting @code{Elaborate} or
31226 @code{Elaborate_All} pragmas where
31227 needed. However, this can lead to the creation of elaboration circularities
31228 and a resulting rejection of the program by gnatbind. This issue is
31229 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
31230 In brief, there are several
31231 ways to deal with this situation:
31235 Modify the program to eliminate the circularities, e.g.@: by moving
31236 elaboration-time code into explicitly-invoked procedures
31238 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
31239 @code{Elaborate} pragmas, and then inhibit the generation of implicit
31240 @code{Elaborate_All}
31241 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
31242 (by selectively suppressing elaboration checks via pragma
31243 @code{Suppress(Elaboration_Check)} when it is safe to do so).
31246 @node Target-specific aspects
31247 @subsection Target-specific aspects
31249 Low-level applications need to deal with machine addresses, data
31250 representations, interfacing with assembler code, and similar issues. If
31251 such an Ada 83 application is being ported to different target hardware (for
31252 example where the byte endianness has changed) then you will need to
31253 carefully examine the program logic; the porting effort will heavily depend
31254 on the robustness of the original design. Moreover, Ada 95 (and thus
31255 Ada 2005) are sometimes
31256 incompatible with typical Ada 83 compiler practices regarding implicit
31257 packing, the meaning of the Size attribute, and the size of access values.
31258 GNAT's approach to these issues is described in @ref{Representation Clauses}.
31260 @node Compatibility with Other Ada Systems
31261 @section Compatibility with Other Ada Systems
31264 If programs avoid the use of implementation dependent and
31265 implementation defined features, as documented in the @cite{Ada
31266 Reference Manual}, there should be a high degree of portability between
31267 GNAT and other Ada systems. The following are specific items which
31268 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
31269 compilers, but do not affect porting code to GNAT@.
31270 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
31271 the following issues may or may not arise for Ada 2005 programs
31272 when other compilers appear.)
31275 @item Ada 83 Pragmas and Attributes
31276 Ada 95 compilers are allowed, but not required, to implement the missing
31277 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
31278 GNAT implements all such pragmas and attributes, eliminating this as
31279 a compatibility concern, but some other Ada 95 compilers reject these
31280 pragmas and attributes.
31282 @item Specialized Needs Annexes
31283 GNAT implements the full set of special needs annexes. At the
31284 current time, it is the only Ada 95 compiler to do so. This means that
31285 programs making use of these features may not be portable to other Ada
31286 95 compilation systems.
31288 @item Representation Clauses
31289 Some other Ada 95 compilers implement only the minimal set of
31290 representation clauses required by the Ada 95 reference manual. GNAT goes
31291 far beyond this minimal set, as described in the next section.
31294 @node Representation Clauses
31295 @section Representation Clauses
31298 The Ada 83 reference manual was quite vague in describing both the minimal
31299 required implementation of representation clauses, and also their precise
31300 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
31301 minimal set of capabilities required is still quite limited.
31303 GNAT implements the full required set of capabilities in
31304 Ada 95 and Ada 2005, but also goes much further, and in particular
31305 an effort has been made to be compatible with existing Ada 83 usage to the
31306 greatest extent possible.
31308 A few cases exist in which Ada 83 compiler behavior is incompatible with
31309 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
31310 intentional or accidental dependence on specific implementation dependent
31311 characteristics of these Ada 83 compilers. The following is a list of
31312 the cases most likely to arise in existing Ada 83 code.
31315 @item Implicit Packing
31316 Some Ada 83 compilers allowed a Size specification to cause implicit
31317 packing of an array or record. This could cause expensive implicit
31318 conversions for change of representation in the presence of derived
31319 types, and the Ada design intends to avoid this possibility.
31320 Subsequent AI's were issued to make it clear that such implicit
31321 change of representation in response to a Size clause is inadvisable,
31322 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
31323 Reference Manuals as implementation advice that is followed by GNAT@.
31324 The problem will show up as an error
31325 message rejecting the size clause. The fix is simply to provide
31326 the explicit pragma @code{Pack}, or for more fine tuned control, provide
31327 a Component_Size clause.
31329 @item Meaning of Size Attribute
31330 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
31331 the minimal number of bits required to hold values of the type. For example,
31332 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
31333 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
31334 some 32 in this situation. This problem will usually show up as a compile
31335 time error, but not always. It is a good idea to check all uses of the
31336 'Size attribute when porting Ada 83 code. The GNAT specific attribute
31337 Object_Size can provide a useful way of duplicating the behavior of
31338 some Ada 83 compiler systems.
31340 @item Size of Access Types
31341 A common assumption in Ada 83 code is that an access type is in fact a pointer,
31342 and that therefore it will be the same size as a System.Address value. This
31343 assumption is true for GNAT in most cases with one exception. For the case of
31344 a pointer to an unconstrained array type (where the bounds may vary from one
31345 value of the access type to another), the default is to use a ``fat pointer'',
31346 which is represented as two separate pointers, one to the bounds, and one to
31347 the array. This representation has a number of advantages, including improved
31348 efficiency. However, it may cause some difficulties in porting existing Ada 83
31349 code which makes the assumption that, for example, pointers fit in 32 bits on
31350 a machine with 32-bit addressing.
31352 To get around this problem, GNAT also permits the use of ``thin pointers'' for
31353 access types in this case (where the designated type is an unconstrained array
31354 type). These thin pointers are indeed the same size as a System.Address value.
31355 To specify a thin pointer, use a size clause for the type, for example:
31357 @smallexample @c ada
31358 type X is access all String;
31359 for X'Size use Standard'Address_Size;
31363 which will cause the type X to be represented using a single pointer.
31364 When using this representation, the bounds are right behind the array.
31365 This representation is slightly less efficient, and does not allow quite
31366 such flexibility in the use of foreign pointers or in using the
31367 Unrestricted_Access attribute to create pointers to non-aliased objects.
31368 But for any standard portable use of the access type it will work in
31369 a functionally correct manner and allow porting of existing code.
31370 Note that another way of forcing a thin pointer representation
31371 is to use a component size clause for the element size in an array,
31372 or a record representation clause for an access field in a record.
31376 @c This brief section is only in the non-VMS version
31377 @c The complete chapter on HP Ada is in the VMS version
31378 @node Compatibility with HP Ada 83
31379 @section Compatibility with HP Ada 83
31382 The VMS version of GNAT fully implements all the pragmas and attributes
31383 provided by HP Ada 83, as well as providing the standard HP Ada 83
31384 libraries, including Starlet. In addition, data layouts and parameter
31385 passing conventions are highly compatible. This means that porting
31386 existing HP Ada 83 code to GNAT in VMS systems should be easier than
31387 most other porting efforts. The following are some of the most
31388 significant differences between GNAT and HP Ada 83.
31391 @item Default floating-point representation
31392 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
31393 it is VMS format. GNAT does implement the necessary pragmas
31394 (Long_Float, Float_Representation) for changing this default.
31397 The package System in GNAT exactly corresponds to the definition in the
31398 Ada 95 reference manual, which means that it excludes many of the
31399 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
31400 that contains the additional definitions, and a special pragma,
31401 Extend_System allows this package to be treated transparently as an
31402 extension of package System.
31405 The definitions provided by Aux_DEC are exactly compatible with those
31406 in the HP Ada 83 version of System, with one exception.
31407 HP Ada provides the following declarations:
31409 @smallexample @c ada
31410 TO_ADDRESS (INTEGER)
31411 TO_ADDRESS (UNSIGNED_LONGWORD)
31412 TO_ADDRESS (@i{universal_integer})
31416 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
31417 an extension to Ada 83 not strictly compatible with the reference manual.
31418 In GNAT, we are constrained to be exactly compatible with the standard,
31419 and this means we cannot provide this capability. In HP Ada 83, the
31420 point of this definition is to deal with a call like:
31422 @smallexample @c ada
31423 TO_ADDRESS (16#12777#);
31427 Normally, according to the Ada 83 standard, one would expect this to be
31428 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
31429 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
31430 definition using @i{universal_integer} takes precedence.
31432 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
31433 is not possible to be 100% compatible. Since there are many programs using
31434 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
31435 to change the name of the function in the UNSIGNED_LONGWORD case, so the
31436 declarations provided in the GNAT version of AUX_Dec are:
31438 @smallexample @c ada
31439 function To_Address (X : Integer) return Address;
31440 pragma Pure_Function (To_Address);
31442 function To_Address_Long (X : Unsigned_Longword)
31444 pragma Pure_Function (To_Address_Long);
31448 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
31449 change the name to TO_ADDRESS_LONG@.
31451 @item Task_Id values
31452 The Task_Id values assigned will be different in the two systems, and GNAT
31453 does not provide a specified value for the Task_Id of the environment task,
31454 which in GNAT is treated like any other declared task.
31458 For full details on these and other less significant compatibility issues,
31459 see appendix E of the HP publication entitled @cite{HP Ada, Technical
31460 Overview and Comparison on HP Platforms}.
31462 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
31463 attributes are recognized, although only a subset of them can sensibly
31464 be implemented. The description of pragmas in @ref{Implementation
31465 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
31466 indicates whether or not they are applicable to non-VMS systems.
31470 @node Transitioning to 64-Bit GNAT for OpenVMS
31471 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
31474 This section is meant to assist users of pre-2006 @value{EDITION}
31475 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
31476 the version of the GNAT technology supplied in 2006 and later for
31477 OpenVMS on both Alpha and I64.
31480 * Introduction to transitioning::
31481 * Migration of 32 bit code::
31482 * Taking advantage of 64 bit addressing::
31483 * Technical details::
31486 @node Introduction to transitioning
31487 @subsection Introduction
31490 64-bit @value{EDITION} for Open VMS has been designed to meet
31495 Providing a full conforming implementation of Ada 95 and Ada 2005
31498 Allowing maximum backward compatibility, thus easing migration of existing
31502 Supplying a path for exploiting the full 64-bit address range
31506 Ada's strong typing semantics has made it
31507 impractical to have different 32-bit and 64-bit modes. As soon as
31508 one object could possibly be outside the 32-bit address space, this
31509 would make it necessary for the @code{System.Address} type to be 64 bits.
31510 In particular, this would cause inconsistencies if 32-bit code is
31511 called from 64-bit code that raises an exception.
31513 This issue has been resolved by always using 64-bit addressing
31514 at the system level, but allowing for automatic conversions between
31515 32-bit and 64-bit addresses where required. Thus users who
31516 do not currently require 64-bit addressing capabilities, can
31517 recompile their code with only minimal changes (and indeed
31518 if the code is written in portable Ada, with no assumptions about
31519 the size of the @code{Address} type, then no changes at all are necessary).
31521 this approach provides a simple, gradual upgrade path to future
31522 use of larger memories than available for 32-bit systems.
31523 Also, newly written applications or libraries will by default
31524 be fully compatible with future systems exploiting 64-bit
31525 addressing capabilities.
31527 @ref{Migration of 32 bit code}, will focus on porting applications
31528 that do not require more than 2 GB of
31529 addressable memory. This code will be referred to as
31530 @emph{32-bit code}.
31531 For applications intending to exploit the full 64-bit address space,
31532 @ref{Taking advantage of 64 bit addressing},
31533 will consider further changes that may be required.
31534 Such code will be referred to below as @emph{64-bit code}.
31536 @node Migration of 32 bit code
31537 @subsection Migration of 32-bit code
31542 * Unchecked conversions::
31543 * Predefined constants::
31544 * Interfacing with C::
31545 * Experience with source compatibility::
31548 @node Address types
31549 @subsubsection Address types
31552 To solve the problem of mixing 64-bit and 32-bit addressing,
31553 while maintaining maximum backward compatibility, the following
31554 approach has been taken:
31558 @code{System.Address} always has a size of 64 bits
31561 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31565 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31566 a @code{Short_Address}
31567 may be used where an @code{Address} is required, and vice versa, without
31568 needing explicit type conversions.
31569 By virtue of the Open VMS parameter passing conventions,
31571 and exported subprograms that have 32-bit address parameters are
31572 compatible with those that have 64-bit address parameters.
31573 (See @ref{Making code 64 bit clean} for details.)
31575 The areas that may need attention are those where record types have
31576 been defined that contain components of the type @code{System.Address}, and
31577 where objects of this type are passed to code expecting a record layout with
31580 Different compilers on different platforms cannot be
31581 expected to represent the same type in the same way,
31582 since alignment constraints
31583 and other system-dependent properties affect the compiler's decision.
31584 For that reason, Ada code
31585 generally uses representation clauses to specify the expected
31586 layout where required.
31588 If such a representation clause uses 32 bits for a component having
31589 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31590 will detect that error and produce a specific diagnostic message.
31591 The developer should then determine whether the representation
31592 should be 64 bits or not and make either of two changes:
31593 change the size to 64 bits and leave the type as @code{System.Address}, or
31594 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31595 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31596 required in any code setting or accessing the field; the compiler will
31597 automatically perform any needed conversions between address
31601 @subsubsection Access types
31604 By default, objects designated by access values are always
31605 allocated in the 32-bit
31606 address space. Thus legacy code will never contain
31607 any objects that are not addressable with 32-bit addresses, and
31608 the compiler will never raise exceptions as result of mixing
31609 32-bit and 64-bit addresses.
31611 However, the access values themselves are represented in 64 bits, for optimum
31612 performance and future compatibility with 64-bit code. As was
31613 the case with @code{System.Address}, the compiler will give an error message
31614 if an object or record component has a representation clause that
31615 requires the access value to fit in 32 bits. In such a situation,
31616 an explicit size clause for the access type, specifying 32 bits,
31617 will have the desired effect.
31619 General access types (declared with @code{access all}) can never be
31620 32 bits, as values of such types must be able to refer to any object
31621 of the designated type,
31622 including objects residing outside the 32-bit address range.
31623 Existing Ada 83 code will not contain such type definitions,
31624 however, since general access types were introduced in Ada 95.
31626 @node Unchecked conversions
31627 @subsubsection Unchecked conversions
31630 In the case of an @code{Unchecked_Conversion} where the source type is a
31631 64-bit access type or the type @code{System.Address}, and the target
31632 type is a 32-bit type, the compiler will generate a warning.
31633 Even though the generated code will still perform the required
31634 conversions, it is highly recommended in these cases to use
31635 respectively a 32-bit access type or @code{System.Short_Address}
31636 as the source type.
31638 @node Predefined constants
31639 @subsubsection Predefined constants
31642 The following table shows the correspondence between pre-2006 versions of
31643 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31646 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31647 @item @b{Constant} @tab @b{Old} @tab @b{New}
31648 @item @code{System.Word_Size} @tab 32 @tab 64
31649 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31650 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31651 @item @code{System.Address_Size} @tab 32 @tab 64
31655 If you need to refer to the specific
31656 memory size of a 32-bit implementation, instead of the
31657 actual memory size, use @code{System.Short_Memory_Size}
31658 rather than @code{System.Memory_Size}.
31659 Similarly, references to @code{System.Address_Size} may need
31660 to be replaced by @code{System.Short_Address'Size}.
31661 The program @command{gnatfind} may be useful for locating
31662 references to the above constants, so that you can verify that they
31665 @node Interfacing with C
31666 @subsubsection Interfacing with C
31669 In order to minimize the impact of the transition to 64-bit addresses on
31670 legacy programs, some fundamental types in the @code{Interfaces.C}
31671 package hierarchy continue to be represented in 32 bits.
31672 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31673 This eases integration with the default HP C layout choices, for example
31674 as found in the system routines in @code{DECC$SHR.EXE}.
31675 Because of this implementation choice, the type fully compatible with
31676 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31677 Depending on the context the compiler will issue a
31678 warning or an error when type @code{Address} is used, alerting the user to a
31679 potential problem. Otherwise 32-bit programs that use
31680 @code{Interfaces.C} should normally not require code modifications
31682 The other issue arising with C interfacing concerns pragma @code{Convention}.
31683 For VMS 64-bit systems, there is an issue of the appropriate default size
31684 of C convention pointers in the absence of an explicit size clause. The HP
31685 C compiler can choose either 32 or 64 bits depending on compiler options.
31686 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31687 clause is given. This proves a better choice for porting 32-bit legacy
31688 applications. In order to have a 64-bit representation, it is necessary to
31689 specify a size representation clause. For example:
31691 @smallexample @c ada
31692 type int_star is access Interfaces.C.int;
31693 pragma Convention(C, int_star);
31694 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31697 @node Experience with source compatibility
31698 @subsubsection Experience with source compatibility
31701 The Security Server and STARLET on I64 provide an interesting ``test case''
31702 for source compatibility issues, since it is in such system code
31703 where assumptions about @code{Address} size might be expected to occur.
31704 Indeed, there were a small number of occasions in the Security Server
31705 file @file{jibdef.ads}
31706 where a representation clause for a record type specified
31707 32 bits for a component of type @code{Address}.
31708 All of these errors were detected by the compiler.
31709 The repair was obvious and immediate; to simply replace @code{Address} by
31710 @code{Short_Address}.
31712 In the case of STARLET, there were several record types that should
31713 have had representation clauses but did not. In these record types
31714 there was an implicit assumption that an @code{Address} value occupied
31716 These compiled without error, but their usage resulted in run-time error
31717 returns from STARLET system calls.
31718 Future GNAT technology enhancements may include a tool that detects and flags
31719 these sorts of potential source code porting problems.
31721 @c ****************************************
31722 @node Taking advantage of 64 bit addressing
31723 @subsection Taking advantage of 64-bit addressing
31726 * Making code 64 bit clean::
31727 * Allocating memory from the 64 bit storage pool::
31728 * Restrictions on use of 64 bit objects::
31729 * Using 64 bit storage pools by default::
31730 * General access types::
31731 * STARLET and other predefined libraries::
31734 @node Making code 64 bit clean
31735 @subsubsection Making code 64-bit clean
31738 In order to prevent problems that may occur when (parts of) a
31739 system start using memory outside the 32-bit address range,
31740 we recommend some additional guidelines:
31744 For imported subprograms that take parameters of the
31745 type @code{System.Address}, ensure that these subprograms can
31746 indeed handle 64-bit addresses. If not, or when in doubt,
31747 change the subprogram declaration to specify
31748 @code{System.Short_Address} instead.
31751 Resolve all warnings related to size mismatches in
31752 unchecked conversions. Failing to do so causes
31753 erroneous execution if the source object is outside
31754 the 32-bit address space.
31757 (optional) Explicitly use the 32-bit storage pool
31758 for access types used in a 32-bit context, or use
31759 generic access types where possible
31760 (@pxref{Restrictions on use of 64 bit objects}).
31764 If these rules are followed, the compiler will automatically insert
31765 any necessary checks to ensure that no addresses or access values
31766 passed to 32-bit code ever refer to objects outside the 32-bit
31768 Any attempt to do this will raise @code{Constraint_Error}.
31770 @node Allocating memory from the 64 bit storage pool
31771 @subsubsection Allocating memory from the 64-bit storage pool
31774 For any access type @code{T} that potentially requires memory allocations
31775 beyond the 32-bit address space,
31776 use the following representation clause:
31778 @smallexample @c ada
31779 for T'Storage_Pool use System.Pool_64;
31782 @node Restrictions on use of 64 bit objects
31783 @subsubsection Restrictions on use of 64-bit objects
31786 Taking the address of an object allocated from a 64-bit storage pool,
31787 and then passing this address to a subprogram expecting
31788 @code{System.Short_Address},
31789 or assigning it to a variable of type @code{Short_Address}, will cause
31790 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31791 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31792 no exception is raised and execution
31793 will become erroneous.
31795 @node Using 64 bit storage pools by default
31796 @subsubsection Using 64-bit storage pools by default
31799 In some cases it may be desirable to have the compiler allocate
31800 from 64-bit storage pools by default. This may be the case for
31801 libraries that are 64-bit clean, but may be used in both 32-bit
31802 and 64-bit contexts. For these cases the following configuration
31803 pragma may be specified:
31805 @smallexample @c ada
31806 pragma Pool_64_Default;
31810 Any code compiled in the context of this pragma will by default
31811 use the @code{System.Pool_64} storage pool. This default may be overridden
31812 for a specific access type @code{T} by the representation clause:
31814 @smallexample @c ada
31815 for T'Storage_Pool use System.Pool_32;
31819 Any object whose address may be passed to a subprogram with a
31820 @code{Short_Address} argument, or assigned to a variable of type
31821 @code{Short_Address}, needs to be allocated from this pool.
31823 @node General access types
31824 @subsubsection General access types
31827 Objects designated by access values from a
31828 general access type (declared with @code{access all}) are never allocated
31829 from a 64-bit storage pool. Code that uses general access types will
31830 accept objects allocated in either 32-bit or 64-bit address spaces,
31831 but never allocate objects outside the 32-bit address space.
31832 Using general access types ensures maximum compatibility with both
31833 32-bit and 64-bit code.
31835 @node STARLET and other predefined libraries
31836 @subsubsection STARLET and other predefined libraries
31839 All code that comes as part of GNAT is 64-bit clean, but the
31840 restrictions given in @ref{Restrictions on use of 64 bit objects},
31841 still apply. Look at the package
31842 specs to see in which contexts objects allocated
31843 in 64-bit address space are acceptable.
31845 @node Technical details
31846 @subsection Technical details
31849 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31850 Ada standard with respect to the type of @code{System.Address}. Previous
31851 versions of GNAT Pro have defined this type as private and implemented it as a
31854 In order to allow defining @code{System.Short_Address} as a proper subtype,
31855 and to match the implicit sign extension in parameter passing,
31856 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31857 visible (i.e., non-private) integer type.
31858 Standard operations on the type, such as the binary operators ``+'', ``-'',
31859 etc., that take @code{Address} operands and return an @code{Address} result,
31860 have been hidden by declaring these
31861 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31862 ambiguities that would otherwise result from overloading.
31863 (Note that, although @code{Address} is a visible integer type,
31864 good programming practice dictates against exploiting the type's
31865 integer properties such as literals, since this will compromise
31868 Defining @code{Address} as a visible integer type helps achieve
31869 maximum compatibility for existing Ada code,
31870 without sacrificing the capabilities of the 64-bit architecture.
31873 @c ************************************************
31875 @node Microsoft Windows Topics
31876 @appendix Microsoft Windows Topics
31882 This chapter describes topics that are specific to the Microsoft Windows
31883 platforms (NT, 2000, and XP Professional).
31886 * Using GNAT on Windows::
31887 * Using a network installation of GNAT::
31888 * CONSOLE and WINDOWS subsystems::
31889 * Temporary Files::
31890 * Mixed-Language Programming on Windows::
31891 * Windows Calling Conventions::
31892 * Introduction to Dynamic Link Libraries (DLLs)::
31893 * Using DLLs with GNAT::
31894 * Building DLLs with GNAT::
31895 * Building DLLs with GNAT Project files::
31896 * Building DLLs with gnatdll::
31897 * GNAT and Windows Resources::
31898 * Debugging a DLL::
31899 * Setting Stack Size from gnatlink::
31900 * Setting Heap Size from gnatlink::
31903 @node Using GNAT on Windows
31904 @section Using GNAT on Windows
31907 One of the strengths of the GNAT technology is that its tool set
31908 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31909 @code{gdb} debugger, etc.) is used in the same way regardless of the
31912 On Windows this tool set is complemented by a number of Microsoft-specific
31913 tools that have been provided to facilitate interoperability with Windows
31914 when this is required. With these tools:
31919 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31923 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31924 relocatable and non-relocatable DLLs are supported).
31927 You can build Ada DLLs for use in other applications. These applications
31928 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31929 relocatable and non-relocatable Ada DLLs are supported.
31932 You can include Windows resources in your Ada application.
31935 You can use or create COM/DCOM objects.
31939 Immediately below are listed all known general GNAT-for-Windows restrictions.
31940 Other restrictions about specific features like Windows Resources and DLLs
31941 are listed in separate sections below.
31946 It is not possible to use @code{GetLastError} and @code{SetLastError}
31947 when tasking, protected records, or exceptions are used. In these
31948 cases, in order to implement Ada semantics, the GNAT run-time system
31949 calls certain Win32 routines that set the last error variable to 0 upon
31950 success. It should be possible to use @code{GetLastError} and
31951 @code{SetLastError} when tasking, protected record, and exception
31952 features are not used, but it is not guaranteed to work.
31955 It is not possible to link against Microsoft libraries except for
31956 import libraries. The library must be built to be compatible with
31957 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31958 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31959 not be compatible with the GNAT runtime. Even if the library is
31960 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31963 When the compilation environment is located on FAT32 drives, users may
31964 experience recompilations of the source files that have not changed if
31965 Daylight Saving Time (DST) state has changed since the last time files
31966 were compiled. NTFS drives do not have this problem.
31969 No components of the GNAT toolset use any entries in the Windows
31970 registry. The only entries that can be created are file associations and
31971 PATH settings, provided the user has chosen to create them at installation
31972 time, as well as some minimal book-keeping information needed to correctly
31973 uninstall or integrate different GNAT products.
31976 @node Using a network installation of GNAT
31977 @section Using a network installation of GNAT
31980 Make sure the system on which GNAT is installed is accessible from the
31981 current machine, i.e., the install location is shared over the network.
31982 Shared resources are accessed on Windows by means of UNC paths, which
31983 have the format @code{\\server\sharename\path}
31985 In order to use such a network installation, simply add the UNC path of the
31986 @file{bin} directory of your GNAT installation in front of your PATH. For
31987 example, if GNAT is installed in @file{\GNAT} directory of a share location
31988 called @file{c-drive} on a machine @file{LOKI}, the following command will
31991 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31993 Be aware that every compilation using the network installation results in the
31994 transfer of large amounts of data across the network and will likely cause
31995 serious performance penalty.
31997 @node CONSOLE and WINDOWS subsystems
31998 @section CONSOLE and WINDOWS subsystems
31999 @cindex CONSOLE Subsystem
32000 @cindex WINDOWS Subsystem
32004 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
32005 (which is the default subsystem) will always create a console when
32006 launching the application. This is not something desirable when the
32007 application has a Windows GUI. To get rid of this console the
32008 application must be using the @code{WINDOWS} subsystem. To do so
32009 the @option{-mwindows} linker option must be specified.
32012 $ gnatmake winprog -largs -mwindows
32015 @node Temporary Files
32016 @section Temporary Files
32017 @cindex Temporary files
32020 It is possible to control where temporary files gets created by setting
32021 the @env{TMP} environment variable. The file will be created:
32024 @item Under the directory pointed to by the @env{TMP} environment variable if
32025 this directory exists.
32027 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
32028 set (or not pointing to a directory) and if this directory exists.
32030 @item Under the current working directory otherwise.
32034 This allows you to determine exactly where the temporary
32035 file will be created. This is particularly useful in networked
32036 environments where you may not have write access to some
32039 @node Mixed-Language Programming on Windows
32040 @section Mixed-Language Programming on Windows
32043 Developing pure Ada applications on Windows is no different than on
32044 other GNAT-supported platforms. However, when developing or porting an
32045 application that contains a mix of Ada and C/C++, the choice of your
32046 Windows C/C++ development environment conditions your overall
32047 interoperability strategy.
32049 If you use @command{gcc} to compile the non-Ada part of your application,
32050 there are no Windows-specific restrictions that affect the overall
32051 interoperability with your Ada code. If you plan to use
32052 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
32053 the following limitations:
32057 You cannot link your Ada code with an object or library generated with
32058 Microsoft tools if these use the @code{.tls} section (Thread Local
32059 Storage section) since the GNAT linker does not yet support this section.
32062 You cannot link your Ada code with an object or library generated with
32063 Microsoft tools if these use I/O routines other than those provided in
32064 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
32065 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
32066 libraries can cause a conflict with @code{msvcrt.dll} services. For
32067 instance Visual C++ I/O stream routines conflict with those in
32072 If you do want to use the Microsoft tools for your non-Ada code and hit one
32073 of the above limitations, you have two choices:
32077 Encapsulate your non-Ada code in a DLL to be linked with your Ada
32078 application. In this case, use the Microsoft or whatever environment to
32079 build the DLL and use GNAT to build your executable
32080 (@pxref{Using DLLs with GNAT}).
32083 Or you can encapsulate your Ada code in a DLL to be linked with the
32084 other part of your application. In this case, use GNAT to build the DLL
32085 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
32086 environment to build your executable.
32089 @node Windows Calling Conventions
32090 @section Windows Calling Conventions
32095 * C Calling Convention::
32096 * Stdcall Calling Convention::
32097 * Win32 Calling Convention::
32098 * DLL Calling Convention::
32102 When a subprogram @code{F} (caller) calls a subprogram @code{G}
32103 (callee), there are several ways to push @code{G}'s parameters on the
32104 stack and there are several possible scenarios to clean up the stack
32105 upon @code{G}'s return. A calling convention is an agreed upon software
32106 protocol whereby the responsibilities between the caller (@code{F}) and
32107 the callee (@code{G}) are clearly defined. Several calling conventions
32108 are available for Windows:
32112 @code{C} (Microsoft defined)
32115 @code{Stdcall} (Microsoft defined)
32118 @code{Win32} (GNAT specific)
32121 @code{DLL} (GNAT specific)
32124 @node C Calling Convention
32125 @subsection @code{C} Calling Convention
32128 This is the default calling convention used when interfacing to C/C++
32129 routines compiled with either @command{gcc} or Microsoft Visual C++.
32131 In the @code{C} calling convention subprogram parameters are pushed on the
32132 stack by the caller from right to left. The caller itself is in charge of
32133 cleaning up the stack after the call. In addition, the name of a routine
32134 with @code{C} calling convention is mangled by adding a leading underscore.
32136 The name to use on the Ada side when importing (or exporting) a routine
32137 with @code{C} calling convention is the name of the routine. For
32138 instance the C function:
32141 int get_val (long);
32145 should be imported from Ada as follows:
32147 @smallexample @c ada
32149 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32150 pragma Import (C, Get_Val, External_Name => "get_val");
32155 Note that in this particular case the @code{External_Name} parameter could
32156 have been omitted since, when missing, this parameter is taken to be the
32157 name of the Ada entity in lower case. When the @code{Link_Name} parameter
32158 is missing, as in the above example, this parameter is set to be the
32159 @code{External_Name} with a leading underscore.
32161 When importing a variable defined in C, you should always use the @code{C}
32162 calling convention unless the object containing the variable is part of a
32163 DLL (in which case you should use the @code{Stdcall} calling
32164 convention, @pxref{Stdcall Calling Convention}).
32166 @node Stdcall Calling Convention
32167 @subsection @code{Stdcall} Calling Convention
32170 This convention, which was the calling convention used for Pascal
32171 programs, is used by Microsoft for all the routines in the Win32 API for
32172 efficiency reasons. It must be used to import any routine for which this
32173 convention was specified.
32175 In the @code{Stdcall} calling convention subprogram parameters are pushed
32176 on the stack by the caller from right to left. The callee (and not the
32177 caller) is in charge of cleaning the stack on routine exit. In addition,
32178 the name of a routine with @code{Stdcall} calling convention is mangled by
32179 adding a leading underscore (as for the @code{C} calling convention) and a
32180 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
32181 bytes) of the parameters passed to the routine.
32183 The name to use on the Ada side when importing a C routine with a
32184 @code{Stdcall} calling convention is the name of the C routine. The leading
32185 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
32186 the compiler. For instance the Win32 function:
32189 @b{APIENTRY} int get_val (long);
32193 should be imported from Ada as follows:
32195 @smallexample @c ada
32197 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32198 pragma Import (Stdcall, Get_Val);
32199 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
32204 As for the @code{C} calling convention, when the @code{External_Name}
32205 parameter is missing, it is taken to be the name of the Ada entity in lower
32206 case. If instead of writing the above import pragma you write:
32208 @smallexample @c ada
32210 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32211 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
32216 then the imported routine is @code{_retrieve_val@@4}. However, if instead
32217 of specifying the @code{External_Name} parameter you specify the
32218 @code{Link_Name} as in the following example:
32220 @smallexample @c ada
32222 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32223 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
32228 then the imported routine is @code{retrieve_val}, that is, there is no
32229 decoration at all. No leading underscore and no Stdcall suffix
32230 @code{@@}@code{@var{nn}}.
32233 This is especially important as in some special cases a DLL's entry
32234 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
32235 name generated for a call has it.
32238 It is also possible to import variables defined in a DLL by using an
32239 import pragma for a variable. As an example, if a DLL contains a
32240 variable defined as:
32247 then, to access this variable from Ada you should write:
32249 @smallexample @c ada
32251 My_Var : Interfaces.C.int;
32252 pragma Import (Stdcall, My_Var);
32257 Note that to ease building cross-platform bindings this convention
32258 will be handled as a @code{C} calling convention on non-Windows platforms.
32260 @node Win32 Calling Convention
32261 @subsection @code{Win32} Calling Convention
32264 This convention, which is GNAT-specific is fully equivalent to the
32265 @code{Stdcall} calling convention described above.
32267 @node DLL Calling Convention
32268 @subsection @code{DLL} Calling Convention
32271 This convention, which is GNAT-specific is fully equivalent to the
32272 @code{Stdcall} calling convention described above.
32274 @node Introduction to Dynamic Link Libraries (DLLs)
32275 @section Introduction to Dynamic Link Libraries (DLLs)
32279 A Dynamically Linked Library (DLL) is a library that can be shared by
32280 several applications running under Windows. A DLL can contain any number of
32281 routines and variables.
32283 One advantage of DLLs is that you can change and enhance them without
32284 forcing all the applications that depend on them to be relinked or
32285 recompiled. However, you should be aware than all calls to DLL routines are
32286 slower since, as you will understand below, such calls are indirect.
32288 To illustrate the remainder of this section, suppose that an application
32289 wants to use the services of a DLL @file{API.dll}. To use the services
32290 provided by @file{API.dll} you must statically link against the DLL or
32291 an import library which contains a jump table with an entry for each
32292 routine and variable exported by the DLL. In the Microsoft world this
32293 import library is called @file{API.lib}. When using GNAT this import
32294 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
32295 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
32297 After you have linked your application with the DLL or the import library
32298 and you run your application, here is what happens:
32302 Your application is loaded into memory.
32305 The DLL @file{API.dll} is mapped into the address space of your
32306 application. This means that:
32310 The DLL will use the stack of the calling thread.
32313 The DLL will use the virtual address space of the calling process.
32316 The DLL will allocate memory from the virtual address space of the calling
32320 Handles (pointers) can be safely exchanged between routines in the DLL
32321 routines and routines in the application using the DLL.
32325 The entries in the jump table (from the import library @file{libAPI.dll.a}
32326 or @file{API.lib} or automatically created when linking against a DLL)
32327 which is part of your application are initialized with the addresses
32328 of the routines and variables in @file{API.dll}.
32331 If present in @file{API.dll}, routines @code{DllMain} or
32332 @code{DllMainCRTStartup} are invoked. These routines typically contain
32333 the initialization code needed for the well-being of the routines and
32334 variables exported by the DLL.
32338 There is an additional point which is worth mentioning. In the Windows
32339 world there are two kind of DLLs: relocatable and non-relocatable
32340 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
32341 in the target application address space. If the addresses of two
32342 non-relocatable DLLs overlap and these happen to be used by the same
32343 application, a conflict will occur and the application will run
32344 incorrectly. Hence, when possible, it is always preferable to use and
32345 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
32346 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
32347 User's Guide) removes the debugging symbols from the DLL but the DLL can
32348 still be relocated.
32350 As a side note, an interesting difference between Microsoft DLLs and
32351 Unix shared libraries, is the fact that on most Unix systems all public
32352 routines are exported by default in a Unix shared library, while under
32353 Windows it is possible (but not required) to list exported routines in
32354 a definition file (@pxref{The Definition File}).
32356 @node Using DLLs with GNAT
32357 @section Using DLLs with GNAT
32360 * Creating an Ada Spec for the DLL Services::
32361 * Creating an Import Library::
32365 To use the services of a DLL, say @file{API.dll}, in your Ada application
32370 The Ada spec for the routines and/or variables you want to access in
32371 @file{API.dll}. If not available this Ada spec must be built from the C/C++
32372 header files provided with the DLL.
32375 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
32376 mentioned an import library is a statically linked library containing the
32377 import table which will be filled at load time to point to the actual
32378 @file{API.dll} routines. Sometimes you don't have an import library for the
32379 DLL you want to use. The following sections will explain how to build
32380 one. Note that this is optional.
32383 The actual DLL, @file{API.dll}.
32387 Once you have all the above, to compile an Ada application that uses the
32388 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
32389 you simply issue the command
32392 $ gnatmake my_ada_app -largs -lAPI
32396 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
32397 tells the GNAT linker to look first for a library named @file{API.lib}
32398 (Microsoft-style name) and if not found for a libraries named
32399 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
32400 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
32401 contains the following pragma
32403 @smallexample @c ada
32404 pragma Linker_Options ("-lAPI");
32408 you do not have to add @option{-largs -lAPI} at the end of the
32409 @command{gnatmake} command.
32411 If any one of the items above is missing you will have to create it
32412 yourself. The following sections explain how to do so using as an
32413 example a fictitious DLL called @file{API.dll}.
32415 @node Creating an Ada Spec for the DLL Services
32416 @subsection Creating an Ada Spec for the DLL Services
32419 A DLL typically comes with a C/C++ header file which provides the
32420 definitions of the routines and variables exported by the DLL. The Ada
32421 equivalent of this header file is a package spec that contains definitions
32422 for the imported entities. If the DLL you intend to use does not come with
32423 an Ada spec you have to generate one such spec yourself. For example if
32424 the header file of @file{API.dll} is a file @file{api.h} containing the
32425 following two definitions:
32437 then the equivalent Ada spec could be:
32439 @smallexample @c ada
32442 with Interfaces.C.Strings;
32447 function Get (Str : C.Strings.Chars_Ptr) return C.int;
32450 pragma Import (C, Get);
32451 pragma Import (DLL, Some_Var);
32458 Note that a variable is
32459 @strong{always imported with a Stdcall convention}. A function
32460 can have @code{C} or @code{Stdcall} convention.
32461 (@pxref{Windows Calling Conventions}).
32463 @node Creating an Import Library
32464 @subsection Creating an Import Library
32465 @cindex Import library
32468 * The Definition File::
32469 * GNAT-Style Import Library::
32470 * Microsoft-Style Import Library::
32474 If a Microsoft-style import library @file{API.lib} or a GNAT-style
32475 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
32476 with @file{API.dll} you can skip this section. You can also skip this
32477 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
32478 as in this case it is possible to link directly against the
32479 DLL. Otherwise read on.
32481 @node The Definition File
32482 @subsubsection The Definition File
32483 @cindex Definition file
32487 As previously mentioned, and unlike Unix systems, the list of symbols
32488 that are exported from a DLL must be provided explicitly in Windows.
32489 The main goal of a definition file is precisely that: list the symbols
32490 exported by a DLL. A definition file (usually a file with a @code{.def}
32491 suffix) has the following structure:
32496 @r{[}LIBRARY @var{name}@r{]}
32497 @r{[}DESCRIPTION @var{string}@r{]}
32507 @item LIBRARY @var{name}
32508 This section, which is optional, gives the name of the DLL.
32510 @item DESCRIPTION @var{string}
32511 This section, which is optional, gives a description string that will be
32512 embedded in the import library.
32515 This section gives the list of exported symbols (procedures, functions or
32516 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32517 section of @file{API.def} looks like:
32531 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32532 (@pxref{Windows Calling Conventions}) for a Stdcall
32533 calling convention function in the exported symbols list.
32536 There can actually be other sections in a definition file, but these
32537 sections are not relevant to the discussion at hand.
32539 @node GNAT-Style Import Library
32540 @subsubsection GNAT-Style Import Library
32543 To create a static import library from @file{API.dll} with the GNAT tools
32544 you should proceed as follows:
32548 Create the definition file @file{API.def} (@pxref{The Definition File}).
32549 For that use the @code{dll2def} tool as follows:
32552 $ dll2def API.dll > API.def
32556 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32557 to standard output the list of entry points in the DLL. Note that if
32558 some routines in the DLL have the @code{Stdcall} convention
32559 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32560 suffix then you'll have to edit @file{api.def} to add it, and specify
32561 @option{-k} to @command{gnatdll} when creating the import library.
32564 Here are some hints to find the right @code{@@}@var{nn} suffix.
32568 If you have the Microsoft import library (.lib), it is possible to get
32569 the right symbols by using Microsoft @code{dumpbin} tool (see the
32570 corresponding Microsoft documentation for further details).
32573 $ dumpbin /exports api.lib
32577 If you have a message about a missing symbol at link time the compiler
32578 tells you what symbol is expected. You just have to go back to the
32579 definition file and add the right suffix.
32583 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32584 (@pxref{Using gnatdll}) as follows:
32587 $ gnatdll -e API.def -d API.dll
32591 @code{gnatdll} takes as input a definition file @file{API.def} and the
32592 name of the DLL containing the services listed in the definition file
32593 @file{API.dll}. The name of the static import library generated is
32594 computed from the name of the definition file as follows: if the
32595 definition file name is @var{xyz}@code{.def}, the import library name will
32596 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32597 @option{-e} could have been removed because the name of the definition
32598 file (before the ``@code{.def}'' suffix) is the same as the name of the
32599 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32602 @node Microsoft-Style Import Library
32603 @subsubsection Microsoft-Style Import Library
32606 With GNAT you can either use a GNAT-style or Microsoft-style import
32607 library. A Microsoft import library is needed only if you plan to make an
32608 Ada DLL available to applications developed with Microsoft
32609 tools (@pxref{Mixed-Language Programming on Windows}).
32611 To create a Microsoft-style import library for @file{API.dll} you
32612 should proceed as follows:
32616 Create the definition file @file{API.def} from the DLL. For this use either
32617 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32618 tool (see the corresponding Microsoft documentation for further details).
32621 Build the actual import library using Microsoft's @code{lib} utility:
32624 $ lib -machine:IX86 -def:API.def -out:API.lib
32628 If you use the above command the definition file @file{API.def} must
32629 contain a line giving the name of the DLL:
32636 See the Microsoft documentation for further details about the usage of
32640 @node Building DLLs with GNAT
32641 @section Building DLLs with GNAT
32642 @cindex DLLs, building
32645 This section explain how to build DLLs using the GNAT built-in DLL
32646 support. With the following procedure it is straight forward to build
32647 and use DLLs with GNAT.
32651 @item building object files
32653 The first step is to build all objects files that are to be included
32654 into the DLL. This is done by using the standard @command{gnatmake} tool.
32656 @item building the DLL
32658 To build the DLL you must use @command{gcc}'s @option{-shared}
32659 option. It is quite simple to use this method:
32662 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32665 It is important to note that in this case all symbols found in the
32666 object files are automatically exported. It is possible to restrict
32667 the set of symbols to export by passing to @command{gcc} a definition
32668 file, @pxref{The Definition File}. For example:
32671 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32674 If you use a definition file you must export the elaboration procedures
32675 for every package that required one. Elaboration procedures are named
32676 using the package name followed by "_E".
32678 @item preparing DLL to be used
32680 For the DLL to be used by client programs the bodies must be hidden
32681 from it and the .ali set with read-only attribute. This is very important
32682 otherwise GNAT will recompile all packages and will not actually use
32683 the code in the DLL. For example:
32687 $ copy *.ads *.ali api.dll apilib
32688 $ attrib +R apilib\*.ali
32693 At this point it is possible to use the DLL by directly linking
32694 against it. Note that you must use the GNAT shared runtime when using
32695 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32699 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32702 @node Building DLLs with GNAT Project files
32703 @section Building DLLs with GNAT Project files
32704 @cindex DLLs, building
32707 There is nothing specific to Windows in the build process.
32708 @pxref{Library Projects}.
32711 Due to a system limitation, it is not possible under Windows to create threads
32712 when inside the @code{DllMain} routine which is used for auto-initialization
32713 of shared libraries, so it is not possible to have library level tasks in SALs.
32715 @node Building DLLs with gnatdll
32716 @section Building DLLs with gnatdll
32717 @cindex DLLs, building
32720 * Limitations When Using Ada DLLs from Ada::
32721 * Exporting Ada Entities::
32722 * Ada DLLs and Elaboration::
32723 * Ada DLLs and Finalization::
32724 * Creating a Spec for Ada DLLs::
32725 * Creating the Definition File::
32730 Note that it is preferred to use the built-in GNAT DLL support
32731 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32732 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32734 This section explains how to build DLLs containing Ada code using
32735 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32736 remainder of this section.
32738 The steps required to build an Ada DLL that is to be used by Ada as well as
32739 non-Ada applications are as follows:
32743 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32744 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32745 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32746 skip this step if you plan to use the Ada DLL only from Ada applications.
32749 Your Ada code must export an initialization routine which calls the routine
32750 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32751 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32752 routine exported by the Ada DLL must be invoked by the clients of the DLL
32753 to initialize the DLL.
32756 When useful, the DLL should also export a finalization routine which calls
32757 routine @code{adafinal} generated by @command{gnatbind} to perform the
32758 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32759 The finalization routine exported by the Ada DLL must be invoked by the
32760 clients of the DLL when the DLL services are no further needed.
32763 You must provide a spec for the services exported by the Ada DLL in each
32764 of the programming languages to which you plan to make the DLL available.
32767 You must provide a definition file listing the exported entities
32768 (@pxref{The Definition File}).
32771 Finally you must use @code{gnatdll} to produce the DLL and the import
32772 library (@pxref{Using gnatdll}).
32776 Note that a relocatable DLL stripped using the @code{strip}
32777 binutils tool will not be relocatable anymore. To build a DLL without
32778 debug information pass @code{-largs -s} to @code{gnatdll}. This
32779 restriction does not apply to a DLL built using a Library Project.
32780 @pxref{Library Projects}.
32782 @node Limitations When Using Ada DLLs from Ada
32783 @subsection Limitations When Using Ada DLLs from Ada
32786 When using Ada DLLs from Ada applications there is a limitation users
32787 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32788 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32789 each Ada DLL includes the services of the GNAT run time that are necessary
32790 to the Ada code inside the DLL. As a result, when an Ada program uses an
32791 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32792 one in the main program.
32794 It is therefore not possible to exchange GNAT run-time objects between the
32795 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32796 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32799 It is completely safe to exchange plain elementary, array or record types,
32800 Windows object handles, etc.
32802 @node Exporting Ada Entities
32803 @subsection Exporting Ada Entities
32804 @cindex Export table
32807 Building a DLL is a way to encapsulate a set of services usable from any
32808 application. As a result, the Ada entities exported by a DLL should be
32809 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32810 any Ada name mangling. As an example here is an Ada package
32811 @code{API}, spec and body, exporting two procedures, a function, and a
32814 @smallexample @c ada
32817 with Interfaces.C; use Interfaces;
32819 Count : C.int := 0;
32820 function Factorial (Val : C.int) return C.int;
32822 procedure Initialize_API;
32823 procedure Finalize_API;
32824 -- Initialization & Finalization routines. More in the next section.
32826 pragma Export (C, Initialize_API);
32827 pragma Export (C, Finalize_API);
32828 pragma Export (C, Count);
32829 pragma Export (C, Factorial);
32835 @smallexample @c ada
32838 package body API is
32839 function Factorial (Val : C.int) return C.int is
32842 Count := Count + 1;
32843 for K in 1 .. Val loop
32849 procedure Initialize_API is
32851 pragma Import (C, Adainit);
32854 end Initialize_API;
32856 procedure Finalize_API is
32857 procedure Adafinal;
32858 pragma Import (C, Adafinal);
32868 If the Ada DLL you are building will only be used by Ada applications
32869 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32870 convention. As an example, the previous package could be written as
32873 @smallexample @c ada
32877 Count : Integer := 0;
32878 function Factorial (Val : Integer) return Integer;
32880 procedure Initialize_API;
32881 procedure Finalize_API;
32882 -- Initialization and Finalization routines.
32888 @smallexample @c ada
32891 package body API is
32892 function Factorial (Val : Integer) return Integer is
32893 Fact : Integer := 1;
32895 Count := Count + 1;
32896 for K in 1 .. Val loop
32903 -- The remainder of this package body is unchanged.
32910 Note that if you do not export the Ada entities with a @code{C} or
32911 @code{Stdcall} convention you will have to provide the mangled Ada names
32912 in the definition file of the Ada DLL
32913 (@pxref{Creating the Definition File}).
32915 @node Ada DLLs and Elaboration
32916 @subsection Ada DLLs and Elaboration
32917 @cindex DLLs and elaboration
32920 The DLL that you are building contains your Ada code as well as all the
32921 routines in the Ada library that are needed by it. The first thing a
32922 user of your DLL must do is elaborate the Ada code
32923 (@pxref{Elaboration Order Handling in GNAT}).
32925 To achieve this you must export an initialization routine
32926 (@code{Initialize_API} in the previous example), which must be invoked
32927 before using any of the DLL services. This elaboration routine must call
32928 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32929 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32930 @code{Initialize_Api} for an example. Note that the GNAT binder is
32931 automatically invoked during the DLL build process by the @code{gnatdll}
32932 tool (@pxref{Using gnatdll}).
32934 When a DLL is loaded, Windows systematically invokes a routine called
32935 @code{DllMain}. It would therefore be possible to call @code{adainit}
32936 directly from @code{DllMain} without having to provide an explicit
32937 initialization routine. Unfortunately, it is not possible to call
32938 @code{adainit} from the @code{DllMain} if your program has library level
32939 tasks because access to the @code{DllMain} entry point is serialized by
32940 the system (that is, only a single thread can execute ``through'' it at a
32941 time), which means that the GNAT run time will deadlock waiting for the
32942 newly created task to complete its initialization.
32944 @node Ada DLLs and Finalization
32945 @subsection Ada DLLs and Finalization
32946 @cindex DLLs and finalization
32949 When the services of an Ada DLL are no longer needed, the client code should
32950 invoke the DLL finalization routine, if available. The DLL finalization
32951 routine is in charge of releasing all resources acquired by the DLL. In the
32952 case of the Ada code contained in the DLL, this is achieved by calling
32953 routine @code{adafinal} generated by the GNAT binder
32954 (@pxref{Binding with Non-Ada Main Programs}).
32955 See the body of @code{Finalize_Api} for an
32956 example. As already pointed out the GNAT binder is automatically invoked
32957 during the DLL build process by the @code{gnatdll} tool
32958 (@pxref{Using gnatdll}).
32960 @node Creating a Spec for Ada DLLs
32961 @subsection Creating a Spec for Ada DLLs
32964 To use the services exported by the Ada DLL from another programming
32965 language (e.g.@: C), you have to translate the specs of the exported Ada
32966 entities in that language. For instance in the case of @code{API.dll},
32967 the corresponding C header file could look like:
32972 extern int *_imp__count;
32973 #define count (*_imp__count)
32974 int factorial (int);
32980 It is important to understand that when building an Ada DLL to be used by
32981 other Ada applications, you need two different specs for the packages
32982 contained in the DLL: one for building the DLL and the other for using
32983 the DLL. This is because the @code{DLL} calling convention is needed to
32984 use a variable defined in a DLL, but when building the DLL, the variable
32985 must have either the @code{Ada} or @code{C} calling convention. As an
32986 example consider a DLL comprising the following package @code{API}:
32988 @smallexample @c ada
32992 Count : Integer := 0;
32994 -- Remainder of the package omitted.
33001 After producing a DLL containing package @code{API}, the spec that
33002 must be used to import @code{API.Count} from Ada code outside of the
33005 @smallexample @c ada
33010 pragma Import (DLL, Count);
33016 @node Creating the Definition File
33017 @subsection Creating the Definition File
33020 The definition file is the last file needed to build the DLL. It lists
33021 the exported symbols. As an example, the definition file for a DLL
33022 containing only package @code{API} (where all the entities are exported
33023 with a @code{C} calling convention) is:
33038 If the @code{C} calling convention is missing from package @code{API},
33039 then the definition file contains the mangled Ada names of the above
33040 entities, which in this case are:
33049 api__initialize_api
33054 @node Using gnatdll
33055 @subsection Using @code{gnatdll}
33059 * gnatdll Example::
33060 * gnatdll behind the Scenes::
33065 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
33066 and non-Ada sources that make up your DLL have been compiled.
33067 @code{gnatdll} is actually in charge of two distinct tasks: build the
33068 static import library for the DLL and the actual DLL. The form of the
33069 @code{gnatdll} command is
33073 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
33078 where @var{list-of-files} is a list of ALI and object files. The object
33079 file list must be the exact list of objects corresponding to the non-Ada
33080 sources whose services are to be included in the DLL. The ALI file list
33081 must be the exact list of ALI files for the corresponding Ada sources
33082 whose services are to be included in the DLL. If @var{list-of-files} is
33083 missing, only the static import library is generated.
33086 You may specify any of the following switches to @code{gnatdll}:
33089 @item -a@ovar{address}
33090 @cindex @option{-a} (@code{gnatdll})
33091 Build a non-relocatable DLL at @var{address}. If @var{address} is not
33092 specified the default address @var{0x11000000} will be used. By default,
33093 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
33094 advise the reader to build relocatable DLL.
33096 @item -b @var{address}
33097 @cindex @option{-b} (@code{gnatdll})
33098 Set the relocatable DLL base address. By default the address is
33101 @item -bargs @var{opts}
33102 @cindex @option{-bargs} (@code{gnatdll})
33103 Binder options. Pass @var{opts} to the binder.
33105 @item -d @var{dllfile}
33106 @cindex @option{-d} (@code{gnatdll})
33107 @var{dllfile} is the name of the DLL. This switch must be present for
33108 @code{gnatdll} to do anything. The name of the generated import library is
33109 obtained algorithmically from @var{dllfile} as shown in the following
33110 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
33111 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
33112 by option @option{-e}) is obtained algorithmically from @var{dllfile}
33113 as shown in the following example:
33114 if @var{dllfile} is @code{xyz.dll}, the definition
33115 file used is @code{xyz.def}.
33117 @item -e @var{deffile}
33118 @cindex @option{-e} (@code{gnatdll})
33119 @var{deffile} is the name of the definition file.
33122 @cindex @option{-g} (@code{gnatdll})
33123 Generate debugging information. This information is stored in the object
33124 file and copied from there to the final DLL file by the linker,
33125 where it can be read by the debugger. You must use the
33126 @option{-g} switch if you plan on using the debugger or the symbolic
33130 @cindex @option{-h} (@code{gnatdll})
33131 Help mode. Displays @code{gnatdll} switch usage information.
33134 @cindex @option{-I} (@code{gnatdll})
33135 Direct @code{gnatdll} to search the @var{dir} directory for source and
33136 object files needed to build the DLL.
33137 (@pxref{Search Paths and the Run-Time Library (RTL)}).
33140 @cindex @option{-k} (@code{gnatdll})
33141 Removes the @code{@@}@var{nn} suffix from the import library's exported
33142 names, but keeps them for the link names. You must specify this
33143 option if you want to use a @code{Stdcall} function in a DLL for which
33144 the @code{@@}@var{nn} suffix has been removed. This is the case for most
33145 of the Windows NT DLL for example. This option has no effect when
33146 @option{-n} option is specified.
33148 @item -l @var{file}
33149 @cindex @option{-l} (@code{gnatdll})
33150 The list of ALI and object files used to build the DLL are listed in
33151 @var{file}, instead of being given in the command line. Each line in
33152 @var{file} contains the name of an ALI or object file.
33155 @cindex @option{-n} (@code{gnatdll})
33156 No Import. Do not create the import library.
33159 @cindex @option{-q} (@code{gnatdll})
33160 Quiet mode. Do not display unnecessary messages.
33163 @cindex @option{-v} (@code{gnatdll})
33164 Verbose mode. Display extra information.
33166 @item -largs @var{opts}
33167 @cindex @option{-largs} (@code{gnatdll})
33168 Linker options. Pass @var{opts} to the linker.
33171 @node gnatdll Example
33172 @subsubsection @code{gnatdll} Example
33175 As an example the command to build a relocatable DLL from @file{api.adb}
33176 once @file{api.adb} has been compiled and @file{api.def} created is
33179 $ gnatdll -d api.dll api.ali
33183 The above command creates two files: @file{libapi.dll.a} (the import
33184 library) and @file{api.dll} (the actual DLL). If you want to create
33185 only the DLL, just type:
33188 $ gnatdll -d api.dll -n api.ali
33192 Alternatively if you want to create just the import library, type:
33195 $ gnatdll -d api.dll
33198 @node gnatdll behind the Scenes
33199 @subsubsection @code{gnatdll} behind the Scenes
33202 This section details the steps involved in creating a DLL. @code{gnatdll}
33203 does these steps for you. Unless you are interested in understanding what
33204 goes on behind the scenes, you should skip this section.
33206 We use the previous example of a DLL containing the Ada package @code{API},
33207 to illustrate the steps necessary to build a DLL. The starting point is a
33208 set of objects that will make up the DLL and the corresponding ALI
33209 files. In the case of this example this means that @file{api.o} and
33210 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
33215 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
33216 the information necessary to generate relocation information for the
33222 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
33227 In addition to the base file, the @command{gnatlink} command generates an
33228 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
33229 asks @command{gnatlink} to generate the routines @code{DllMain} and
33230 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
33231 is loaded into memory.
33234 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
33235 export table (@file{api.exp}). The export table contains the relocation
33236 information in a form which can be used during the final link to ensure
33237 that the Windows loader is able to place the DLL anywhere in memory.
33241 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33242 --output-exp api.exp
33247 @code{gnatdll} builds the base file using the new export table. Note that
33248 @command{gnatbind} must be called once again since the binder generated file
33249 has been deleted during the previous call to @command{gnatlink}.
33254 $ gnatlink api -o api.jnk api.exp -mdll
33255 -Wl,--base-file,api.base
33260 @code{gnatdll} builds the new export table using the new base file and
33261 generates the DLL import library @file{libAPI.dll.a}.
33265 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33266 --output-exp api.exp --output-lib libAPI.a
33271 Finally @code{gnatdll} builds the relocatable DLL using the final export
33277 $ gnatlink api api.exp -o api.dll -mdll
33282 @node Using dlltool
33283 @subsubsection Using @code{dlltool}
33286 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
33287 DLLs and static import libraries. This section summarizes the most
33288 common @code{dlltool} switches. The form of the @code{dlltool} command
33292 $ dlltool @ovar{switches}
33296 @code{dlltool} switches include:
33299 @item --base-file @var{basefile}
33300 @cindex @option{--base-file} (@command{dlltool})
33301 Read the base file @var{basefile} generated by the linker. This switch
33302 is used to create a relocatable DLL.
33304 @item --def @var{deffile}
33305 @cindex @option{--def} (@command{dlltool})
33306 Read the definition file.
33308 @item --dllname @var{name}
33309 @cindex @option{--dllname} (@command{dlltool})
33310 Gives the name of the DLL. This switch is used to embed the name of the
33311 DLL in the static import library generated by @code{dlltool} with switch
33312 @option{--output-lib}.
33315 @cindex @option{-k} (@command{dlltool})
33316 Kill @code{@@}@var{nn} from exported names
33317 (@pxref{Windows Calling Conventions}
33318 for a discussion about @code{Stdcall}-style symbols.
33321 @cindex @option{--help} (@command{dlltool})
33322 Prints the @code{dlltool} switches with a concise description.
33324 @item --output-exp @var{exportfile}
33325 @cindex @option{--output-exp} (@command{dlltool})
33326 Generate an export file @var{exportfile}. The export file contains the
33327 export table (list of symbols in the DLL) and is used to create the DLL.
33329 @item --output-lib @var{libfile}
33330 @cindex @option{--output-lib} (@command{dlltool})
33331 Generate a static import library @var{libfile}.
33334 @cindex @option{-v} (@command{dlltool})
33337 @item --as @var{assembler-name}
33338 @cindex @option{--as} (@command{dlltool})
33339 Use @var{assembler-name} as the assembler. The default is @code{as}.
33342 @node GNAT and Windows Resources
33343 @section GNAT and Windows Resources
33344 @cindex Resources, windows
33347 * Building Resources::
33348 * Compiling Resources::
33349 * Using Resources::
33353 Resources are an easy way to add Windows specific objects to your
33354 application. The objects that can be added as resources include:
33383 This section explains how to build, compile and use resources.
33385 @node Building Resources
33386 @subsection Building Resources
33387 @cindex Resources, building
33390 A resource file is an ASCII file. By convention resource files have an
33391 @file{.rc} extension.
33392 The easiest way to build a resource file is to use Microsoft tools
33393 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
33394 @code{dlgedit.exe} to build dialogs.
33395 It is always possible to build an @file{.rc} file yourself by writing a
33398 It is not our objective to explain how to write a resource file. A
33399 complete description of the resource script language can be found in the
33400 Microsoft documentation.
33402 @node Compiling Resources
33403 @subsection Compiling Resources
33406 @cindex Resources, compiling
33409 This section describes how to build a GNAT-compatible (COFF) object file
33410 containing the resources. This is done using the Resource Compiler
33411 @code{windres} as follows:
33414 $ windres -i myres.rc -o myres.o
33418 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
33419 file. You can specify an alternate preprocessor (usually named
33420 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
33421 parameter. A list of all possible options may be obtained by entering
33422 the command @code{windres} @option{--help}.
33424 It is also possible to use the Microsoft resource compiler @code{rc.exe}
33425 to produce a @file{.res} file (binary resource file). See the
33426 corresponding Microsoft documentation for further details. In this case
33427 you need to use @code{windres} to translate the @file{.res} file to a
33428 GNAT-compatible object file as follows:
33431 $ windres -i myres.res -o myres.o
33434 @node Using Resources
33435 @subsection Using Resources
33436 @cindex Resources, using
33439 To include the resource file in your program just add the
33440 GNAT-compatible object file for the resource(s) to the linker
33441 arguments. With @command{gnatmake} this is done by using the @option{-largs}
33445 $ gnatmake myprog -largs myres.o
33448 @node Debugging a DLL
33449 @section Debugging a DLL
33450 @cindex DLL debugging
33453 * Program and DLL Both Built with GCC/GNAT::
33454 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
33458 Debugging a DLL is similar to debugging a standard program. But
33459 we have to deal with two different executable parts: the DLL and the
33460 program that uses it. We have the following four possibilities:
33464 The program and the DLL are built with @code{GCC/GNAT}.
33466 The program is built with foreign tools and the DLL is built with
33469 The program is built with @code{GCC/GNAT} and the DLL is built with
33475 In this section we address only cases one and two above.
33476 There is no point in trying to debug
33477 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
33478 information in it. To do so you must use a debugger compatible with the
33479 tools suite used to build the DLL.
33481 @node Program and DLL Both Built with GCC/GNAT
33482 @subsection Program and DLL Both Built with GCC/GNAT
33485 This is the simplest case. Both the DLL and the program have @code{GDB}
33486 compatible debugging information. It is then possible to break anywhere in
33487 the process. Let's suppose here that the main procedure is named
33488 @code{ada_main} and that in the DLL there is an entry point named
33492 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
33493 program must have been built with the debugging information (see GNAT -g
33494 switch). Here are the step-by-step instructions for debugging it:
33497 @item Launch @code{GDB} on the main program.
33503 @item Start the program and stop at the beginning of the main procedure
33510 This step is required to be able to set a breakpoint inside the DLL. As long
33511 as the program is not run, the DLL is not loaded. This has the
33512 consequence that the DLL debugging information is also not loaded, so it is not
33513 possible to set a breakpoint in the DLL.
33515 @item Set a breakpoint inside the DLL
33518 (gdb) break ada_dll
33525 At this stage a breakpoint is set inside the DLL. From there on
33526 you can use the standard approach to debug the whole program
33527 (@pxref{Running and Debugging Ada Programs}).
33530 @c This used to work, probably because the DLLs were non-relocatable
33531 @c keep this section around until the problem is sorted out.
33533 To break on the @code{DllMain} routine it is not possible to follow
33534 the procedure above. At the time the program stop on @code{ada_main}
33535 the @code{DllMain} routine as already been called. Either you can use
33536 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33539 @item Launch @code{GDB} on the main program.
33545 @item Load DLL symbols
33548 (gdb) add-sym api.dll
33551 @item Set a breakpoint inside the DLL
33554 (gdb) break ada_dll.adb:45
33557 Note that at this point it is not possible to break using the routine symbol
33558 directly as the program is not yet running. The solution is to break
33559 on the proper line (break in @file{ada_dll.adb} line 45).
33561 @item Start the program
33570 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33571 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33574 * Debugging the DLL Directly::
33575 * Attaching to a Running Process::
33579 In this case things are slightly more complex because it is not possible to
33580 start the main program and then break at the beginning to load the DLL and the
33581 associated DLL debugging information. It is not possible to break at the
33582 beginning of the program because there is no @code{GDB} debugging information,
33583 and therefore there is no direct way of getting initial control. This
33584 section addresses this issue by describing some methods that can be used
33585 to break somewhere in the DLL to debug it.
33588 First suppose that the main procedure is named @code{main} (this is for
33589 example some C code built with Microsoft Visual C) and that there is a
33590 DLL named @code{test.dll} containing an Ada entry point named
33594 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33595 been built with debugging information (see GNAT -g option).
33597 @node Debugging the DLL Directly
33598 @subsubsection Debugging the DLL Directly
33602 Find out the executable starting address
33605 $ objdump --file-header main.exe
33608 The starting address is reported on the last line. For example:
33611 main.exe: file format pei-i386
33612 architecture: i386, flags 0x0000010a:
33613 EXEC_P, HAS_DEBUG, D_PAGED
33614 start address 0x00401010
33618 Launch the debugger on the executable.
33625 Set a breakpoint at the starting address, and launch the program.
33628 $ (gdb) break *0x00401010
33632 The program will stop at the given address.
33635 Set a breakpoint on a DLL subroutine.
33638 (gdb) break ada_dll.adb:45
33641 Or if you want to break using a symbol on the DLL, you need first to
33642 select the Ada language (language used by the DLL).
33645 (gdb) set language ada
33646 (gdb) break ada_dll
33650 Continue the program.
33657 This will run the program until it reaches the breakpoint that has been
33658 set. From that point you can use the standard way to debug a program
33659 as described in (@pxref{Running and Debugging Ada Programs}).
33664 It is also possible to debug the DLL by attaching to a running process.
33666 @node Attaching to a Running Process
33667 @subsubsection Attaching to a Running Process
33668 @cindex DLL debugging, attach to process
33671 With @code{GDB} it is always possible to debug a running process by
33672 attaching to it. It is possible to debug a DLL this way. The limitation
33673 of this approach is that the DLL must run long enough to perform the
33674 attach operation. It may be useful for instance to insert a time wasting
33675 loop in the code of the DLL to meet this criterion.
33679 @item Launch the main program @file{main.exe}.
33685 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33686 that the process PID for @file{main.exe} is 208.
33694 @item Attach to the running process to be debugged.
33700 @item Load the process debugging information.
33703 (gdb) symbol-file main.exe
33706 @item Break somewhere in the DLL.
33709 (gdb) break ada_dll
33712 @item Continue process execution.
33721 This last step will resume the process execution, and stop at
33722 the breakpoint we have set. From there you can use the standard
33723 approach to debug a program as described in
33724 (@pxref{Running and Debugging Ada Programs}).
33726 @node Setting Stack Size from gnatlink
33727 @section Setting Stack Size from @command{gnatlink}
33730 It is possible to specify the program stack size at link time. On modern
33731 versions of Windows, starting with XP, this is mostly useful to set the size of
33732 the main stack (environment task). The other task stacks are set with pragma
33733 Storage_Size or with the @command{gnatbind -d} command.
33735 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33736 reserve size of individual tasks, the link-time stack size applies to all
33737 tasks, and pragma Storage_Size has no effect.
33738 In particular, Stack Overflow checks are made against this
33739 link-time specified size.
33741 This setting can be done with
33742 @command{gnatlink} using either:
33746 @item using @option{-Xlinker} linker option
33749 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33752 This sets the stack reserve size to 0x10000 bytes and the stack commit
33753 size to 0x1000 bytes.
33755 @item using @option{-Wl} linker option
33758 $ gnatlink hello -Wl,--stack=0x1000000
33761 This sets the stack reserve size to 0x1000000 bytes. Note that with
33762 @option{-Wl} option it is not possible to set the stack commit size
33763 because the coma is a separator for this option.
33767 @node Setting Heap Size from gnatlink
33768 @section Setting Heap Size from @command{gnatlink}
33771 Under Windows systems, it is possible to specify the program heap size from
33772 @command{gnatlink} using either:
33776 @item using @option{-Xlinker} linker option
33779 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33782 This sets the heap reserve size to 0x10000 bytes and the heap commit
33783 size to 0x1000 bytes.
33785 @item using @option{-Wl} linker option
33788 $ gnatlink hello -Wl,--heap=0x1000000
33791 This sets the heap reserve size to 0x1000000 bytes. Note that with
33792 @option{-Wl} option it is not possible to set the heap commit size
33793 because the coma is a separator for this option.
33799 @c **********************************
33800 @c * GNU Free Documentation License *
33801 @c **********************************
33803 @c GNU Free Documentation License
33805 @node Index,,GNU Free Documentation License, Top
33811 @c Put table of contents at end, otherwise it precedes the "title page" in
33812 @c the .txt version
33813 @c Edit the pdf file to move the contents to the beginning, after the title