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{} 1995-2005, 2006, 2007, 2008 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 * gnatxref Switches::
394 * gnatfind Switches::
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::
495 Sample Bodies Using gnatstub
498 * Switches for gnatstub::
500 Other Utility Programs
502 * Using Other Utility Programs with GNAT::
503 * The External Symbol Naming Scheme of GNAT::
504 * Converting Ada Files to html with gnathtml::
507 Code Coverage and Profiling
509 * Code Coverage of Ada Programs using gcov::
510 * Profiling an Ada Program using gprof::
513 Running and Debugging Ada Programs
515 * The GNAT Debugger GDB::
517 * Introduction to GDB Commands::
518 * Using Ada Expressions::
519 * Calling User-Defined Subprograms::
520 * Using the Next Command in a Function::
523 * Debugging Generic Units::
524 * GNAT Abnormal Termination or Failure to Terminate::
525 * Naming Conventions for GNAT Source Files::
526 * Getting Internal Debugging Information::
534 Compatibility with HP Ada
536 * Ada Language Compatibility::
537 * Differences in the Definition of Package System::
538 * Language-Related Features::
539 * The Package STANDARD::
540 * The Package SYSTEM::
541 * Tasking and Task-Related Features::
542 * Pragmas and Pragma-Related Features::
543 * Library of Predefined Units::
545 * Main Program Definition::
546 * Implementation-Defined Attributes::
547 * Compiler and Run-Time Interfacing::
548 * Program Compilation and Library Management::
550 * Implementation Limits::
551 * Tools and Utilities::
553 Language-Related Features
555 * Integer Types and Representations::
556 * Floating-Point Types and Representations::
557 * Pragmas Float_Representation and Long_Float::
558 * Fixed-Point Types and Representations::
559 * Record and Array Component Alignment::
561 * Other Representation Clauses::
563 Tasking and Task-Related Features
565 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
566 * Assigning Task IDs::
567 * Task IDs and Delays::
568 * Task-Related Pragmas::
569 * Scheduling and Task Priority::
571 * External Interrupts::
573 Pragmas and Pragma-Related Features
575 * Restrictions on the Pragma INLINE::
576 * Restrictions on the Pragma INTERFACE::
577 * Restrictions on the Pragma SYSTEM_NAME::
579 Library of Predefined Units
581 * Changes to DECLIB::
585 * Shared Libraries and Options Files::
589 Platform-Specific Information for the Run-Time Libraries
591 * Summary of Run-Time Configurations::
592 * Specifying a Run-Time Library::
593 * Choosing the Scheduling Policy::
594 * Solaris-Specific Considerations::
595 * Linux-Specific Considerations::
596 * AIX-Specific Considerations::
597 * Irix-Specific Considerations::
599 Example of Binder Output File
601 Elaboration Order Handling in GNAT
604 * Checking the Elaboration Order::
605 * Controlling the Elaboration Order::
606 * Controlling Elaboration in GNAT - Internal Calls::
607 * Controlling Elaboration in GNAT - External Calls::
608 * Default Behavior in GNAT - Ensuring Safety::
609 * Treatment of Pragma Elaborate::
610 * Elaboration Issues for Library Tasks::
611 * Mixing Elaboration Models::
612 * What to Do If the Default Elaboration Behavior Fails::
613 * Elaboration for Access-to-Subprogram Values::
614 * Summary of Procedures for Elaboration Control::
615 * Other Elaboration Order Considerations::
617 Conditional Compilation
618 * Use of Boolean Constants::
619 * Debugging - A Special Case::
620 * Conditionalizing Declarations::
621 * Use of Alternative Implementations::
626 * Basic Assembler Syntax::
627 * A Simple Example of Inline Assembler::
628 * Output Variables in Inline Assembler::
629 * Input Variables in Inline Assembler::
630 * Inlining Inline Assembler Code::
631 * Other Asm Functionality::
633 Compatibility and Porting Guide
635 * Compatibility with Ada 83::
636 * Compatibility between Ada 95 and Ada 2005::
637 * Implementation-dependent characteristics::
639 @c This brief section is only in the non-VMS version
640 @c The complete chapter on HP Ada issues is in the VMS version
641 * Compatibility with HP Ada 83::
643 * Compatibility with Other Ada Systems::
644 * Representation Clauses::
646 * Transitioning to 64-Bit GNAT for OpenVMS::
650 Microsoft Windows Topics
652 * Using GNAT on Windows::
653 * CONSOLE and WINDOWS subsystems::
655 * Mixed-Language Programming on Windows::
656 * Windows Calling Conventions::
657 * Introduction to Dynamic Link Libraries (DLLs)::
658 * Using DLLs with GNAT::
659 * Building DLLs with GNAT::
660 * GNAT and Windows Resources::
662 * Setting Stack Size from gnatlink::
663 * Setting Heap Size from gnatlink::
670 @node About This Guide
671 @unnumbered About This Guide
675 This guide describes the use of @value{EDITION},
676 a compiler and software development toolset for the full Ada
677 programming language, implemented on OpenVMS for HP's Alpha and
678 Integrity server (I64) platforms.
681 This guide describes the use of @value{EDITION},
682 a compiler and software development
683 toolset for the full Ada programming language.
685 It documents the features of the compiler and tools, and explains
686 how to use them to build Ada applications.
688 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
689 Ada 83 compatibility mode.
690 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
691 but you can override with a compiler switch
692 (@pxref{Compiling Different Versions of Ada})
693 to explicitly specify the language version.
694 Throughout this manual, references to ``Ada'' without a year suffix
695 apply to both the Ada 95 and Ada 2005 versions of the language.
699 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
700 ``GNAT'' in the remainder of this document.
707 * What This Guide Contains::
708 * What You Should Know before Reading This Guide::
709 * Related Information::
713 @node What This Guide Contains
714 @unnumberedsec What This Guide Contains
717 This guide contains the following chapters:
721 @ref{Getting Started with GNAT}, describes how to get started compiling
722 and running Ada programs with the GNAT Ada programming environment.
724 @ref{The GNAT Compilation Model}, describes the compilation model used
728 @ref{Compiling Using gcc}, describes how to compile
729 Ada programs with @command{gcc}, the Ada compiler.
732 @ref{Binding Using gnatbind}, describes how to
733 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
737 @ref{Linking Using gnatlink},
738 describes @command{gnatlink}, a
739 program that provides for linking using the GNAT run-time library to
740 construct a program. @command{gnatlink} can also incorporate foreign language
741 object units into the executable.
744 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
745 utility that automatically determines the set of sources
746 needed by an Ada compilation unit, and executes the necessary compilations
750 @ref{Improving Performance}, shows various techniques for making your
751 Ada program run faster or take less space.
752 It discusses the effect of the compiler's optimization switch and
753 also describes the @command{gnatelim} tool and unused subprogram/data
757 @ref{Renaming Files Using gnatchop}, describes
758 @code{gnatchop}, a utility that allows you to preprocess a file that
759 contains Ada source code, and split it into one or more new files, one
760 for each compilation unit.
763 @ref{Configuration Pragmas}, describes the configuration pragmas
767 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
768 shows how to override the default GNAT file naming conventions,
769 either for an individual unit or globally.
772 @ref{GNAT Project Manager}, describes how to use project files
773 to organize large projects.
776 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
777 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
778 way to navigate through sources.
781 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
782 version of an Ada source file with control over casing, indentation,
783 comment placement, and other elements of program presentation style.
786 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
787 metrics for an Ada source file, such as the number of types and subprograms,
788 and assorted complexity measures.
791 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
792 file name krunching utility, used to handle shortened
793 file names on operating systems with a limit on the length of names.
796 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
797 preprocessor utility that allows a single source file to be used to
798 generate multiple or parameterized source files by means of macro
803 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
804 a tool for rebuilding the GNAT run time with user-supplied
805 configuration pragmas.
809 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
810 utility that displays information about compiled units, including dependences
811 on the corresponding sources files, and consistency of compilations.
814 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
815 to delete files that are produced by the compiler, binder and linker.
819 @ref{GNAT and Libraries}, describes the process of creating and using
820 Libraries with GNAT. It also describes how to recompile the GNAT run-time
824 @ref{Using the GNU make Utility}, describes some techniques for using
825 the GNAT toolset in Makefiles.
829 @ref{Memory Management Issues}, describes some useful predefined storage pools
830 and in particular the GNAT Debug Pool facility, which helps detect incorrect
833 It also describes @command{gnatmem}, a utility that monitors dynamic
834 allocation and deallocation and helps detect ``memory leaks''.
838 @ref{Stack Related Facilities}, describes some useful tools associated with
839 stack checking and analysis.
842 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
843 a utility that checks Ada code against a set of rules.
846 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
847 a utility that generates empty but compilable bodies for library units.
850 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
851 generate automatically Ada bindings from C and C++ headers.
854 @ref{Other Utility Programs}, discusses several other GNAT utilities,
855 including @code{gnathtml}.
859 @ref{Code Coverage and Profiling}, describes how to perform a structural
860 coverage and profile the execution of Ada programs.
864 @ref{Running and Debugging Ada Programs}, describes how to run and debug
869 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
870 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
871 developed by Digital Equipment Corporation and currently supported by HP.}
872 for OpenVMS Alpha. This product was formerly known as DEC Ada,
875 historical compatibility reasons, the relevant libraries still use the
880 @ref{Platform-Specific Information for the Run-Time Libraries},
881 describes the various run-time
882 libraries supported by GNAT on various platforms and explains how to
883 choose a particular library.
886 @ref{Example of Binder Output File}, shows the source code for the binder
887 output file for a sample program.
890 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
891 you deal with elaboration order issues.
894 @ref{Conditional Compilation}, describes how to model conditional compilation,
895 both with Ada in general and with GNAT facilities in particular.
898 @ref{Inline Assembler}, shows how to use the inline assembly facility
902 @ref{Compatibility and Porting Guide}, contains sections on compatibility
903 of GNAT with other Ada development environments (including Ada 83 systems),
904 to assist in porting code from those environments.
908 @ref{Microsoft Windows Topics}, presents information relevant to the
909 Microsoft Windows platform.
913 @c *************************************************
914 @node What You Should Know before Reading This Guide
915 @c *************************************************
916 @unnumberedsec What You Should Know before Reading This Guide
918 @cindex Ada 95 Language Reference Manual
919 @cindex Ada 2005 Language Reference Manual
921 This guide assumes a basic familiarity with the Ada 95 language, as
922 described in the International Standard ANSI/ISO/IEC-8652:1995, January
924 It does not require knowledge of the new features introduced by Ada 2005,
925 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
927 Both reference manuals are included in the GNAT documentation
930 @node Related Information
931 @unnumberedsec Related Information
934 For further information about related tools, refer to the following
939 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
940 Reference Manual}, which contains all reference material for the GNAT
941 implementation of Ada.
945 @cite{Using the GNAT Programming Studio}, which describes the GPS
946 Integrated Development Environment.
949 @cite{GNAT Programming Studio Tutorial}, which introduces the
950 main GPS features through examples.
954 @cite{Ada 95 Reference Manual}, which contains reference
955 material for the Ada 95 programming language.
958 @cite{Ada 2005 Reference Manual}, which contains reference
959 material for the Ada 2005 programming language.
962 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
964 in the GNU:[DOCS] directory,
966 for all details on the use of the GNU source-level debugger.
969 @xref{Top,, The extensible self-documenting text editor, emacs,
972 located in the GNU:[DOCS] directory if the EMACS kit is installed,
974 for full information on the extensible editor and programming
981 @unnumberedsec Conventions
983 @cindex Typographical conventions
986 Following are examples of the typographical and graphic conventions used
991 @code{Functions}, @command{utility program names}, @code{standard names},
995 @option{Option flags}
998 @file{File names}, @samp{button names}, and @samp{field names}.
1001 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1008 @r{[}optional information or parameters@r{]}
1011 Examples are described by text
1013 and then shown this way.
1018 Commands that are entered by the user are preceded in this manual by the
1019 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1020 uses this sequence as a prompt, then the commands will appear exactly as
1021 you see them in the manual. If your system uses some other prompt, then
1022 the command will appear with the @code{$} replaced by whatever prompt
1023 character you are using.
1026 Full file names are shown with the ``@code{/}'' character
1027 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1028 If you are using GNAT on a Windows platform, please note that
1029 the ``@code{\}'' character should be used instead.
1032 @c ****************************
1033 @node Getting Started with GNAT
1034 @chapter Getting Started with GNAT
1037 This chapter describes some simple ways of using GNAT to build
1038 executable Ada programs.
1040 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1041 show how to use the command line environment.
1042 @ref{Introduction to GPS}, provides a brief
1043 introduction to the GNAT Programming Studio, a visually-oriented
1044 Integrated Development Environment for GNAT.
1045 GPS offers a graphical ``look and feel'', support for development in
1046 other programming languages, comprehensive browsing features, and
1047 many other capabilities.
1048 For information on GPS please refer to
1049 @cite{Using the GNAT Programming Studio}.
1054 * Running a Simple Ada Program::
1055 * Running a Program with Multiple Units::
1056 * Using the gnatmake Utility::
1058 * Editing with Emacs::
1061 * Introduction to GPS::
1066 @section Running GNAT
1069 Three steps are needed to create an executable file from an Ada source
1074 The source file(s) must be compiled.
1076 The file(s) must be bound using the GNAT binder.
1078 All appropriate object files must be linked to produce an executable.
1082 All three steps are most commonly handled by using the @command{gnatmake}
1083 utility program that, given the name of the main program, automatically
1084 performs the necessary compilation, binding and linking steps.
1086 @node Running a Simple Ada Program
1087 @section Running a Simple Ada Program
1090 Any text editor may be used to prepare an Ada program.
1092 used, the optional Ada mode may be helpful in laying out the program.)
1094 program text is a normal text file. We will assume in our initial
1095 example that you have used your editor to prepare the following
1096 standard format text file:
1098 @smallexample @c ada
1100 with Ada.Text_IO; use Ada.Text_IO;
1103 Put_Line ("Hello WORLD!");
1109 This file should be named @file{hello.adb}.
1110 With the normal default file naming conventions, GNAT requires
1112 contain a single compilation unit whose file name is the
1114 with periods replaced by hyphens; the
1115 extension is @file{ads} for a
1116 spec and @file{adb} for a body.
1117 You can override this default file naming convention by use of the
1118 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1119 Alternatively, if you want to rename your files according to this default
1120 convention, which is probably more convenient if you will be using GNAT
1121 for all your compilations, then the @code{gnatchop} utility
1122 can be used to generate correctly-named source files
1123 (@pxref{Renaming Files Using gnatchop}).
1125 You can compile the program using the following command (@code{$} is used
1126 as the command prompt in the examples in this document):
1133 @command{gcc} is the command used to run the compiler. This compiler is
1134 capable of compiling programs in several languages, including Ada and
1135 C. It assumes that you have given it an Ada program if the file extension is
1136 either @file{.ads} or @file{.adb}, and it will then call
1137 the GNAT compiler to compile the specified file.
1140 The @option{-c} switch is required. It tells @command{gcc} to only do a
1141 compilation. (For C programs, @command{gcc} can also do linking, but this
1142 capability is not used directly for Ada programs, so the @option{-c}
1143 switch must always be present.)
1146 This compile command generates a file
1147 @file{hello.o}, which is the object
1148 file corresponding to your Ada program. It also generates
1149 an ``Ada Library Information'' file @file{hello.ali},
1150 which contains additional information used to check
1151 that an Ada program is consistent.
1152 To build an executable file,
1153 use @code{gnatbind} to bind the program
1154 and @command{gnatlink} to link it. The
1155 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1156 @file{ALI} file, but the default extension of @file{.ali} can
1157 be omitted. This means that in the most common case, the argument
1158 is simply the name of the main program:
1166 A simpler method of carrying out these steps is to use
1168 a master program that invokes all the required
1169 compilation, binding and linking tools in the correct order. In particular,
1170 @command{gnatmake} automatically recompiles any sources that have been
1171 modified since they were last compiled, or sources that depend
1172 on such modified sources, so that ``version skew'' is avoided.
1173 @cindex Version skew (avoided by @command{gnatmake})
1176 $ gnatmake hello.adb
1180 The result is an executable program called @file{hello}, which can be
1188 assuming that the current directory is on the search path
1189 for executable programs.
1192 and, if all has gone well, you will see
1199 appear in response to this command.
1201 @c ****************************************
1202 @node Running a Program with Multiple Units
1203 @section Running a Program with Multiple Units
1206 Consider a slightly more complicated example that has three files: a
1207 main program, and the spec and body of a package:
1209 @smallexample @c ada
1212 package Greetings is
1217 with Ada.Text_IO; use Ada.Text_IO;
1218 package body Greetings is
1221 Put_Line ("Hello WORLD!");
1224 procedure Goodbye is
1226 Put_Line ("Goodbye WORLD!");
1243 Following the one-unit-per-file rule, place this program in the
1244 following three separate files:
1248 spec of package @code{Greetings}
1251 body of package @code{Greetings}
1254 body of main program
1258 To build an executable version of
1259 this program, we could use four separate steps to compile, bind, and link
1260 the program, as follows:
1264 $ gcc -c greetings.adb
1270 Note that there is no required order of compilation when using GNAT.
1271 In particular it is perfectly fine to compile the main program first.
1272 Also, it is not necessary to compile package specs in the case where
1273 there is an accompanying body; you only need to compile the body. If you want
1274 to submit these files to the compiler for semantic checking and not code
1275 generation, then use the
1276 @option{-gnatc} switch:
1279 $ gcc -c greetings.ads -gnatc
1283 Although the compilation can be done in separate steps as in the
1284 above example, in practice it is almost always more convenient
1285 to use the @command{gnatmake} tool. All you need to know in this case
1286 is the name of the main program's source file. The effect of the above four
1287 commands can be achieved with a single one:
1290 $ gnatmake gmain.adb
1294 In the next section we discuss the advantages of using @command{gnatmake} in
1297 @c *****************************
1298 @node Using the gnatmake Utility
1299 @section Using the @command{gnatmake} Utility
1302 If you work on a program by compiling single components at a time using
1303 @command{gcc}, you typically keep track of the units you modify. In order to
1304 build a consistent system, you compile not only these units, but also any
1305 units that depend on the units you have modified.
1306 For example, in the preceding case,
1307 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1308 you edit @file{greetings.ads}, you must recompile both
1309 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1310 units that depend on @file{greetings.ads}.
1312 @code{gnatbind} will warn you if you forget one of these compilation
1313 steps, so that it is impossible to generate an inconsistent program as a
1314 result of forgetting to do a compilation. Nevertheless it is tedious and
1315 error-prone to keep track of dependencies among units.
1316 One approach to handle the dependency-bookkeeping is to use a
1317 makefile. However, makefiles present maintenance problems of their own:
1318 if the dependencies change as you change the program, you must make
1319 sure that the makefile is kept up-to-date manually, which is also an
1320 error-prone process.
1322 The @command{gnatmake} utility takes care of these details automatically.
1323 Invoke it using either one of the following forms:
1326 $ gnatmake gmain.adb
1327 $ gnatmake ^gmain^GMAIN^
1331 The argument is the name of the file containing the main program;
1332 you may omit the extension. @command{gnatmake}
1333 examines the environment, automatically recompiles any files that need
1334 recompiling, and binds and links the resulting set of object files,
1335 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1336 In a large program, it
1337 can be extremely helpful to use @command{gnatmake}, because working out by hand
1338 what needs to be recompiled can be difficult.
1340 Note that @command{gnatmake}
1341 takes into account all the Ada rules that
1342 establish dependencies among units. These include dependencies that result
1343 from inlining subprogram bodies, and from
1344 generic instantiation. Unlike some other
1345 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1346 found by the compiler on a previous compilation, which may possibly
1347 be wrong when sources change. @command{gnatmake} determines the exact set of
1348 dependencies from scratch each time it is run.
1351 @node Editing with Emacs
1352 @section Editing with Emacs
1356 Emacs is an extensible self-documenting text editor that is available in a
1357 separate VMSINSTAL kit.
1359 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1360 click on the Emacs Help menu and run the Emacs Tutorial.
1361 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1362 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1364 Documentation on Emacs and other tools is available in Emacs under the
1365 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1366 use the middle mouse button to select a topic (e.g.@: Emacs).
1368 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1369 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1370 get to the Emacs manual.
1371 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1374 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1375 which is sufficiently extensible to provide for a complete programming
1376 environment and shell for the sophisticated user.
1380 @node Introduction to GPS
1381 @section Introduction to GPS
1382 @cindex GPS (GNAT Programming Studio)
1383 @cindex GNAT Programming Studio (GPS)
1385 Although the command line interface (@command{gnatmake}, etc.) alone
1386 is sufficient, a graphical Interactive Development
1387 Environment can make it easier for you to compose, navigate, and debug
1388 programs. This section describes the main features of GPS
1389 (``GNAT Programming Studio''), the GNAT graphical IDE.
1390 You will see how to use GPS to build and debug an executable, and
1391 you will also learn some of the basics of the GNAT ``project'' facility.
1393 GPS enables you to do much more than is presented here;
1394 e.g., you can produce a call graph, interface to a third-party
1395 Version Control System, and inspect the generated assembly language
1397 Indeed, GPS also supports languages other than Ada.
1398 Such additional information, and an explanation of all of the GPS menu
1399 items. may be found in the on-line help, which includes
1400 a user's guide and a tutorial (these are also accessible from the GNAT
1404 * Building a New Program with GPS::
1405 * Simple Debugging with GPS::
1408 @node Building a New Program with GPS
1409 @subsection Building a New Program with GPS
1411 GPS invokes the GNAT compilation tools using information
1412 contained in a @emph{project} (also known as a @emph{project file}):
1413 a collection of properties such
1414 as source directories, identities of main subprograms, tool switches, etc.,
1415 and their associated values.
1416 See @ref{GNAT Project Manager} for details.
1417 In order to run GPS, you will need to either create a new project
1418 or else open an existing one.
1420 This section will explain how you can use GPS to create a project,
1421 to associate Ada source files with a project, and to build and run
1425 @item @emph{Creating a project}
1427 Invoke GPS, either from the command line or the platform's IDE.
1428 After it starts, GPS will display a ``Welcome'' screen with three
1433 @code{Start with default project in directory}
1436 @code{Create new project with wizard}
1439 @code{Open existing project}
1443 Select @code{Create new project with wizard} and press @code{OK}.
1444 A new window will appear. In the text box labeled with
1445 @code{Enter the name of the project to create}, type @file{sample}
1446 as the project name.
1447 In the next box, browse to choose the directory in which you
1448 would like to create the project file.
1449 After selecting an appropriate directory, press @code{Forward}.
1451 A window will appear with the title
1452 @code{Version Control System Configuration}.
1453 Simply press @code{Forward}.
1455 A window will appear with the title
1456 @code{Please select the source directories for this project}.
1457 The directory that you specified for the project file will be selected
1458 by default as the one to use for sources; simply press @code{Forward}.
1460 A window will appear with the title
1461 @code{Please select the build directory for this project}.
1462 The directory that you specified for the project file will be selected
1463 by default for object files and executables;
1464 simply press @code{Forward}.
1466 A window will appear with the title
1467 @code{Please select the main units for this project}.
1468 You will supply this information later, after creating the source file.
1469 Simply press @code{Forward} for now.
1471 A window will appear with the title
1472 @code{Please select the switches to build the project}.
1473 Press @code{Apply}. This will create a project file named
1474 @file{sample.prj} in the directory that you had specified.
1476 @item @emph{Creating and saving the source file}
1478 After you create the new project, a GPS window will appear, which is
1479 partitioned into two main sections:
1483 A @emph{Workspace area}, initially greyed out, which you will use for
1484 creating and editing source files
1487 Directly below, a @emph{Messages area}, which initially displays a
1488 ``Welcome'' message.
1489 (If the Messages area is not visible, drag its border upward to expand it.)
1493 Select @code{File} on the menu bar, and then the @code{New} command.
1494 The Workspace area will become white, and you can now
1495 enter the source program explicitly.
1496 Type the following text
1498 @smallexample @c ada
1500 with Ada.Text_IO; use Ada.Text_IO;
1503 Put_Line("Hello from GPS!");
1509 Select @code{File}, then @code{Save As}, and enter the source file name
1511 The file will be saved in the same directory you specified as the
1512 location of the default project file.
1514 @item @emph{Updating the project file}
1516 You need to add the new source file to the project.
1518 the @code{Project} menu and then @code{Edit project properties}.
1519 Click the @code{Main files} tab on the left, and then the
1521 Choose @file{hello.adb} from the list, and press @code{Open}.
1522 The project settings window will reflect this action.
1525 @item @emph{Building and running the program}
1527 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1528 and select @file{hello.adb}.
1529 The Messages window will display the resulting invocations of @command{gcc},
1530 @command{gnatbind}, and @command{gnatlink}
1531 (reflecting the default switch settings from the
1532 project file that you created) and then a ``successful compilation/build''
1535 To run the program, choose the @code{Build} menu, then @code{Run}, and
1536 select @command{hello}.
1537 An @emph{Arguments Selection} window will appear.
1538 There are no command line arguments, so just click @code{OK}.
1540 The Messages window will now display the program's output (the string
1541 @code{Hello from GPS}), and at the bottom of the GPS window a status
1542 update is displayed (@code{Run: hello}).
1543 Close the GPS window (or select @code{File}, then @code{Exit}) to
1544 terminate this GPS session.
1547 @node Simple Debugging with GPS
1548 @subsection Simple Debugging with GPS
1550 This section illustrates basic debugging techniques (setting breakpoints,
1551 examining/modifying variables, single stepping).
1554 @item @emph{Opening a project}
1556 Start GPS and select @code{Open existing project}; browse to
1557 specify the project file @file{sample.prj} that you had created in the
1560 @item @emph{Creating a source file}
1562 Select @code{File}, then @code{New}, and type in the following program:
1564 @smallexample @c ada
1566 with Ada.Text_IO; use Ada.Text_IO;
1567 procedure Example is
1568 Line : String (1..80);
1571 Put_Line("Type a line of text at each prompt; an empty line to exit");
1575 Put_Line (Line (1..N) );
1583 Select @code{File}, then @code{Save as}, and enter the file name
1586 @item @emph{Updating the project file}
1588 Add @code{Example} as a new main unit for the project:
1591 Select @code{Project}, then @code{Edit Project Properties}.
1594 Select the @code{Main files} tab, click @code{Add}, then
1595 select the file @file{example.adb} from the list, and
1597 You will see the file name appear in the list of main units
1603 @item @emph{Building/running the executable}
1605 To build the executable
1606 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1608 Run the program to see its effect (in the Messages area).
1609 Each line that you enter is displayed; an empty line will
1610 cause the loop to exit and the program to terminate.
1612 @item @emph{Debugging the program}
1614 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1615 which are required for debugging, are on by default when you create
1617 Thus unless you intentionally remove these settings, you will be able
1618 to debug any program that you develop using GPS.
1621 @item @emph{Initializing}
1623 Select @code{Debug}, then @code{Initialize}, then @file{example}
1625 @item @emph{Setting a breakpoint}
1627 After performing the initialization step, you will observe a small
1628 icon to the right of each line number.
1629 This serves as a toggle for breakpoints; clicking the icon will
1630 set a breakpoint at the corresponding line (the icon will change to
1631 a red circle with an ``x''), and clicking it again
1632 will remove the breakpoint / reset the icon.
1634 For purposes of this example, set a breakpoint at line 10 (the
1635 statement @code{Put_Line@ (Line@ (1..N));}
1637 @item @emph{Starting program execution}
1639 Select @code{Debug}, then @code{Run}. When the
1640 @code{Program Arguments} window appears, click @code{OK}.
1641 A console window will appear; enter some line of text,
1642 e.g.@: @code{abcde}, at the prompt.
1643 The program will pause execution when it gets to the
1644 breakpoint, and the corresponding line is highlighted.
1646 @item @emph{Examining a variable}
1648 Move the mouse over one of the occurrences of the variable @code{N}.
1649 You will see the value (5) displayed, in ``tool tip'' fashion.
1650 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1651 You will see information about @code{N} appear in the @code{Debugger Data}
1652 pane, showing the value as 5.
1654 @item @emph{Assigning a new value to a variable}
1656 Right click on the @code{N} in the @code{Debugger Data} pane, and
1657 select @code{Set value of N}.
1658 When the input window appears, enter the value @code{4} and click
1660 This value does not automatically appear in the @code{Debugger Data}
1661 pane; to see it, right click again on the @code{N} in the
1662 @code{Debugger Data} pane and select @code{Update value}.
1663 The new value, 4, will appear in red.
1665 @item @emph{Single stepping}
1667 Select @code{Debug}, then @code{Next}.
1668 This will cause the next statement to be executed, in this case the
1669 call of @code{Put_Line} with the string slice.
1670 Notice in the console window that the displayed string is simply
1671 @code{abcd} and not @code{abcde} which you had entered.
1672 This is because the upper bound of the slice is now 4 rather than 5.
1674 @item @emph{Removing a breakpoint}
1676 Toggle the breakpoint icon at line 10.
1678 @item @emph{Resuming execution from a breakpoint}
1680 Select @code{Debug}, then @code{Continue}.
1681 The program will reach the next iteration of the loop, and
1682 wait for input after displaying the prompt.
1683 This time, just hit the @kbd{Enter} key.
1684 The value of @code{N} will be 0, and the program will terminate.
1685 The console window will disappear.
1690 @node The GNAT Compilation Model
1691 @chapter The GNAT Compilation Model
1692 @cindex GNAT compilation model
1693 @cindex Compilation model
1696 * Source Representation::
1697 * Foreign Language Representation::
1698 * File Naming Rules::
1699 * Using Other File Names::
1700 * Alternative File Naming Schemes::
1701 * Generating Object Files::
1702 * Source Dependencies::
1703 * The Ada Library Information Files::
1704 * Binding an Ada Program::
1705 * Mixed Language Programming::
1707 * Building Mixed Ada & C++ Programs::
1708 * Comparison between GNAT and C/C++ Compilation Models::
1710 * Comparison between GNAT and Conventional Ada Library Models::
1712 * Placement of temporary files::
1717 This chapter describes the compilation model used by GNAT. Although
1718 similar to that used by other languages, such as C and C++, this model
1719 is substantially different from the traditional Ada compilation models,
1720 which are based on a library. The model is initially described without
1721 reference to the library-based model. If you have not previously used an
1722 Ada compiler, you need only read the first part of this chapter. The
1723 last section describes and discusses the differences between the GNAT
1724 model and the traditional Ada compiler models. If you have used other
1725 Ada compilers, this section will help you to understand those
1726 differences, and the advantages of the GNAT model.
1728 @node Source Representation
1729 @section Source Representation
1733 Ada source programs are represented in standard text files, using
1734 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1735 7-bit ASCII set, plus additional characters used for
1736 representing foreign languages (@pxref{Foreign Language Representation}
1737 for support of non-USA character sets). The format effector characters
1738 are represented using their standard ASCII encodings, as follows:
1743 Vertical tab, @code{16#0B#}
1747 Horizontal tab, @code{16#09#}
1751 Carriage return, @code{16#0D#}
1755 Line feed, @code{16#0A#}
1759 Form feed, @code{16#0C#}
1763 Source files are in standard text file format. In addition, GNAT will
1764 recognize a wide variety of stream formats, in which the end of
1765 physical lines is marked by any of the following sequences:
1766 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1767 in accommodating files that are imported from other operating systems.
1769 @cindex End of source file
1770 @cindex Source file, end
1772 The end of a source file is normally represented by the physical end of
1773 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1774 recognized as signalling the end of the source file. Again, this is
1775 provided for compatibility with other operating systems where this
1776 code is used to represent the end of file.
1778 Each file contains a single Ada compilation unit, including any pragmas
1779 associated with the unit. For example, this means you must place a
1780 package declaration (a package @dfn{spec}) and the corresponding body in
1781 separate files. An Ada @dfn{compilation} (which is a sequence of
1782 compilation units) is represented using a sequence of files. Similarly,
1783 you will place each subunit or child unit in a separate file.
1785 @node Foreign Language Representation
1786 @section Foreign Language Representation
1789 GNAT supports the standard character sets defined in Ada as well as
1790 several other non-standard character sets for use in localized versions
1791 of the compiler (@pxref{Character Set Control}).
1794 * Other 8-Bit Codes::
1795 * Wide Character Encodings::
1803 The basic character set is Latin-1. This character set is defined by ISO
1804 standard 8859, part 1. The lower half (character codes @code{16#00#}
1805 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1806 is used to represent additional characters. These include extended letters
1807 used by European languages, such as French accents, the vowels with umlauts
1808 used in German, and the extra letter A-ring used in Swedish.
1810 @findex Ada.Characters.Latin_1
1811 For a complete list of Latin-1 codes and their encodings, see the source
1812 file of library unit @code{Ada.Characters.Latin_1} in file
1813 @file{a-chlat1.ads}.
1814 You may use any of these extended characters freely in character or
1815 string literals. In addition, the extended characters that represent
1816 letters can be used in identifiers.
1818 @node Other 8-Bit Codes
1819 @subsection Other 8-Bit Codes
1822 GNAT also supports several other 8-bit coding schemes:
1825 @item ISO 8859-2 (Latin-2)
1828 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1831 @item ISO 8859-3 (Latin-3)
1834 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1837 @item ISO 8859-4 (Latin-4)
1840 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1843 @item ISO 8859-5 (Cyrillic)
1846 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1847 lowercase equivalence.
1849 @item ISO 8859-15 (Latin-9)
1852 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1853 lowercase equivalence
1855 @item IBM PC (code page 437)
1856 @cindex code page 437
1857 This code page is the normal default for PCs in the U.S. It corresponds
1858 to the original IBM PC character set. This set has some, but not all, of
1859 the extended Latin-1 letters, but these letters do not have the same
1860 encoding as Latin-1. In this mode, these letters are allowed in
1861 identifiers with uppercase and lowercase equivalence.
1863 @item IBM PC (code page 850)
1864 @cindex code page 850
1865 This code page is a modification of 437 extended to include all the
1866 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1867 mode, all these letters are allowed in identifiers with uppercase and
1868 lowercase equivalence.
1870 @item Full Upper 8-bit
1871 Any character in the range 80-FF allowed in identifiers, and all are
1872 considered distinct. In other words, there are no uppercase and lowercase
1873 equivalences in this range. This is useful in conjunction with
1874 certain encoding schemes used for some foreign character sets (e.g.,
1875 the typical method of representing Chinese characters on the PC).
1878 No upper-half characters in the range 80-FF are allowed in identifiers.
1879 This gives Ada 83 compatibility for identifier names.
1883 For precise data on the encodings permitted, and the uppercase and lowercase
1884 equivalences that are recognized, see the file @file{csets.adb} in
1885 the GNAT compiler sources. You will need to obtain a full source release
1886 of GNAT to obtain this file.
1888 @node Wide Character Encodings
1889 @subsection Wide Character Encodings
1892 GNAT allows wide character codes to appear in character and string
1893 literals, and also optionally in identifiers, by means of the following
1894 possible encoding schemes:
1899 In this encoding, a wide character is represented by the following five
1907 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1908 characters (using uppercase letters) of the wide character code. For
1909 example, ESC A345 is used to represent the wide character with code
1911 This scheme is compatible with use of the full Wide_Character set.
1913 @item Upper-Half Coding
1914 @cindex Upper-Half Coding
1915 The wide character with encoding @code{16#abcd#} where the upper bit is on
1916 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1917 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1918 character, but is not required to be in the upper half. This method can
1919 be also used for shift-JIS or EUC, where the internal coding matches the
1922 @item Shift JIS Coding
1923 @cindex Shift JIS Coding
1924 A wide character is represented by a two-character sequence,
1926 @code{16#cd#}, with the restrictions described for upper-half encoding as
1927 described above. The internal character code is the corresponding JIS
1928 character according to the standard algorithm for Shift-JIS
1929 conversion. Only characters defined in the JIS code set table can be
1930 used with this encoding method.
1934 A wide character is represented by a two-character sequence
1936 @code{16#cd#}, with both characters being in the upper half. The internal
1937 character code is the corresponding JIS character according to the EUC
1938 encoding algorithm. Only characters defined in the JIS code set table
1939 can be used with this encoding method.
1942 A wide character is represented using
1943 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1944 10646-1/Am.2. Depending on the character value, the representation
1945 is a one, two, or three byte sequence:
1950 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1951 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1952 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1957 where the @var{xxx} bits correspond to the left-padded bits of the
1958 16-bit character value. Note that all lower half ASCII characters
1959 are represented as ASCII bytes and all upper half characters and
1960 other wide characters are represented as sequences of upper-half
1961 (The full UTF-8 scheme allows for encoding 31-bit characters as
1962 6-byte sequences, but in this implementation, all UTF-8 sequences
1963 of four or more bytes length will be treated as illegal).
1964 @item Brackets Coding
1965 In this encoding, a wide character is represented by the following eight
1973 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1974 characters (using uppercase letters) of the wide character code. For
1975 example, [``A345''] is used to represent the wide character with code
1976 @code{16#A345#}. It is also possible (though not required) to use the
1977 Brackets coding for upper half characters. For example, the code
1978 @code{16#A3#} can be represented as @code{[``A3'']}.
1980 This scheme is compatible with use of the full Wide_Character set,
1981 and is also the method used for wide character encoding in the standard
1982 ACVC (Ada Compiler Validation Capability) test suite distributions.
1987 Note: Some of these coding schemes do not permit the full use of the
1988 Ada character set. For example, neither Shift JIS, nor EUC allow the
1989 use of the upper half of the Latin-1 set.
1991 @node File Naming Rules
1992 @section File Naming Rules
1995 The default file name is determined by the name of the unit that the
1996 file contains. The name is formed by taking the full expanded name of
1997 the unit and replacing the separating dots with hyphens and using
1998 ^lowercase^uppercase^ for all letters.
2000 An exception arises if the file name generated by the above rules starts
2001 with one of the characters
2003 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2006 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2008 and the second character is a
2009 minus. In this case, the character ^tilde^dollar sign^ is used in place
2010 of the minus. The reason for this special rule is to avoid clashes with
2011 the standard names for child units of the packages System, Ada,
2012 Interfaces, and GNAT, which use the prefixes
2014 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2017 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2021 The file extension is @file{.ads} for a spec and
2022 @file{.adb} for a body. The following list shows some
2023 examples of these rules.
2030 @item arith_functions.ads
2031 Arith_Functions (package spec)
2032 @item arith_functions.adb
2033 Arith_Functions (package body)
2035 Func.Spec (child package spec)
2037 Func.Spec (child package body)
2039 Sub (subunit of Main)
2040 @item ^a~bad.adb^A$BAD.ADB^
2041 A.Bad (child package body)
2045 Following these rules can result in excessively long
2046 file names if corresponding
2047 unit names are long (for example, if child units or subunits are
2048 heavily nested). An option is available to shorten such long file names
2049 (called file name ``krunching''). This may be particularly useful when
2050 programs being developed with GNAT are to be used on operating systems
2051 with limited file name lengths. @xref{Using gnatkr}.
2053 Of course, no file shortening algorithm can guarantee uniqueness over
2054 all possible unit names; if file name krunching is used, it is your
2055 responsibility to ensure no name clashes occur. Alternatively you
2056 can specify the exact file names that you want used, as described
2057 in the next section. Finally, if your Ada programs are migrating from a
2058 compiler with a different naming convention, you can use the gnatchop
2059 utility to produce source files that follow the GNAT naming conventions.
2060 (For details @pxref{Renaming Files Using gnatchop}.)
2062 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2063 systems, case is not significant. So for example on @code{Windows XP}
2064 if the canonical name is @code{main-sub.adb}, you can use the file name
2065 @code{Main-Sub.adb} instead. However, case is significant for other
2066 operating systems, so for example, if you want to use other than
2067 canonically cased file names on a Unix system, you need to follow
2068 the procedures described in the next section.
2070 @node Using Other File Names
2071 @section Using Other File Names
2075 In the previous section, we have described the default rules used by
2076 GNAT to determine the file name in which a given unit resides. It is
2077 often convenient to follow these default rules, and if you follow them,
2078 the compiler knows without being explicitly told where to find all
2081 However, in some cases, particularly when a program is imported from
2082 another Ada compiler environment, it may be more convenient for the
2083 programmer to specify which file names contain which units. GNAT allows
2084 arbitrary file names to be used by means of the Source_File_Name pragma.
2085 The form of this pragma is as shown in the following examples:
2086 @cindex Source_File_Name pragma
2088 @smallexample @c ada
2090 pragma Source_File_Name (My_Utilities.Stacks,
2091 Spec_File_Name => "myutilst_a.ada");
2092 pragma Source_File_name (My_Utilities.Stacks,
2093 Body_File_Name => "myutilst.ada");
2098 As shown in this example, the first argument for the pragma is the unit
2099 name (in this example a child unit). The second argument has the form
2100 of a named association. The identifier
2101 indicates whether the file name is for a spec or a body;
2102 the file name itself is given by a string literal.
2104 The source file name pragma is a configuration pragma, which means that
2105 normally it will be placed in the @file{gnat.adc}
2106 file used to hold configuration
2107 pragmas that apply to a complete compilation environment.
2108 For more details on how the @file{gnat.adc} file is created and used
2109 see @ref{Handling of Configuration Pragmas}.
2110 @cindex @file{gnat.adc}
2113 GNAT allows completely arbitrary file names to be specified using the
2114 source file name pragma. However, if the file name specified has an
2115 extension other than @file{.ads} or @file{.adb} it is necessary to use
2116 a special syntax when compiling the file. The name in this case must be
2117 preceded by the special sequence @option{-x} followed by a space and the name
2118 of the language, here @code{ada}, as in:
2121 $ gcc -c -x ada peculiar_file_name.sim
2126 @command{gnatmake} handles non-standard file names in the usual manner (the
2127 non-standard file name for the main program is simply used as the
2128 argument to gnatmake). Note that if the extension is also non-standard,
2129 then it must be included in the @command{gnatmake} command, it may not
2132 @node Alternative File Naming Schemes
2133 @section Alternative File Naming Schemes
2134 @cindex File naming schemes, alternative
2137 In the previous section, we described the use of the @code{Source_File_Name}
2138 pragma to allow arbitrary names to be assigned to individual source files.
2139 However, this approach requires one pragma for each file, and especially in
2140 large systems can result in very long @file{gnat.adc} files, and also create
2141 a maintenance problem.
2143 GNAT also provides a facility for specifying systematic file naming schemes
2144 other than the standard default naming scheme previously described. An
2145 alternative scheme for naming is specified by the use of
2146 @code{Source_File_Name} pragmas having the following format:
2147 @cindex Source_File_Name pragma
2149 @smallexample @c ada
2150 pragma Source_File_Name (
2151 Spec_File_Name => FILE_NAME_PATTERN
2152 @r{[},Casing => CASING_SPEC@r{]}
2153 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2155 pragma Source_File_Name (
2156 Body_File_Name => FILE_NAME_PATTERN
2157 @r{[},Casing => CASING_SPEC@r{]}
2158 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2160 pragma Source_File_Name (
2161 Subunit_File_Name => FILE_NAME_PATTERN
2162 @r{[},Casing => CASING_SPEC@r{]}
2163 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2165 FILE_NAME_PATTERN ::= STRING_LITERAL
2166 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2170 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2171 It contains a single asterisk character, and the unit name is substituted
2172 systematically for this asterisk. The optional parameter
2173 @code{Casing} indicates
2174 whether the unit name is to be all upper-case letters, all lower-case letters,
2175 or mixed-case. If no
2176 @code{Casing} parameter is used, then the default is all
2177 ^lower-case^upper-case^.
2179 The optional @code{Dot_Replacement} string is used to replace any periods
2180 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2181 argument is used then separating dots appear unchanged in the resulting
2183 Although the above syntax indicates that the
2184 @code{Casing} argument must appear
2185 before the @code{Dot_Replacement} argument, but it
2186 is also permissible to write these arguments in the opposite order.
2188 As indicated, it is possible to specify different naming schemes for
2189 bodies, specs, and subunits. Quite often the rule for subunits is the
2190 same as the rule for bodies, in which case, there is no need to give
2191 a separate @code{Subunit_File_Name} rule, and in this case the
2192 @code{Body_File_name} rule is used for subunits as well.
2194 The separate rule for subunits can also be used to implement the rather
2195 unusual case of a compilation environment (e.g.@: a single directory) which
2196 contains a subunit and a child unit with the same unit name. Although
2197 both units cannot appear in the same partition, the Ada Reference Manual
2198 allows (but does not require) the possibility of the two units coexisting
2199 in the same environment.
2201 The file name translation works in the following steps:
2206 If there is a specific @code{Source_File_Name} pragma for the given unit,
2207 then this is always used, and any general pattern rules are ignored.
2210 If there is a pattern type @code{Source_File_Name} pragma that applies to
2211 the unit, then the resulting file name will be used if the file exists. If
2212 more than one pattern matches, the latest one will be tried first, and the
2213 first attempt resulting in a reference to a file that exists will be used.
2216 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2217 for which the corresponding file exists, then the standard GNAT default
2218 naming rules are used.
2223 As an example of the use of this mechanism, consider a commonly used scheme
2224 in which file names are all lower case, with separating periods copied
2225 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2226 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2229 @smallexample @c ada
2230 pragma Source_File_Name
2231 (Spec_File_Name => "*.1.ada");
2232 pragma Source_File_Name
2233 (Body_File_Name => "*.2.ada");
2237 The default GNAT scheme is actually implemented by providing the following
2238 default pragmas internally:
2240 @smallexample @c ada
2241 pragma Source_File_Name
2242 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2243 pragma Source_File_Name
2244 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2248 Our final example implements a scheme typically used with one of the
2249 Ada 83 compilers, where the separator character for subunits was ``__''
2250 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2251 by adding @file{.ADA}, and subunits by
2252 adding @file{.SEP}. All file names were
2253 upper case. Child units were not present of course since this was an
2254 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2255 the same double underscore separator for child units.
2257 @smallexample @c ada
2258 pragma Source_File_Name
2259 (Spec_File_Name => "*_.ADA",
2260 Dot_Replacement => "__",
2261 Casing = Uppercase);
2262 pragma Source_File_Name
2263 (Body_File_Name => "*.ADA",
2264 Dot_Replacement => "__",
2265 Casing = Uppercase);
2266 pragma Source_File_Name
2267 (Subunit_File_Name => "*.SEP",
2268 Dot_Replacement => "__",
2269 Casing = Uppercase);
2272 @node Generating Object Files
2273 @section Generating Object Files
2276 An Ada program consists of a set of source files, and the first step in
2277 compiling the program is to generate the corresponding object files.
2278 These are generated by compiling a subset of these source files.
2279 The files you need to compile are the following:
2283 If a package spec has no body, compile the package spec to produce the
2284 object file for the package.
2287 If a package has both a spec and a body, compile the body to produce the
2288 object file for the package. The source file for the package spec need
2289 not be compiled in this case because there is only one object file, which
2290 contains the code for both the spec and body of the package.
2293 For a subprogram, compile the subprogram body to produce the object file
2294 for the subprogram. The spec, if one is present, is as usual in a
2295 separate file, and need not be compiled.
2299 In the case of subunits, only compile the parent unit. A single object
2300 file is generated for the entire subunit tree, which includes all the
2304 Compile child units independently of their parent units
2305 (though, of course, the spec of all the ancestor unit must be present in order
2306 to compile a child unit).
2310 Compile generic units in the same manner as any other units. The object
2311 files in this case are small dummy files that contain at most the
2312 flag used for elaboration checking. This is because GNAT always handles generic
2313 instantiation by means of macro expansion. However, it is still necessary to
2314 compile generic units, for dependency checking and elaboration purposes.
2318 The preceding rules describe the set of files that must be compiled to
2319 generate the object files for a program. Each object file has the same
2320 name as the corresponding source file, except that the extension is
2323 You may wish to compile other files for the purpose of checking their
2324 syntactic and semantic correctness. For example, in the case where a
2325 package has a separate spec and body, you would not normally compile the
2326 spec. However, it is convenient in practice to compile the spec to make
2327 sure it is error-free before compiling clients of this spec, because such
2328 compilations will fail if there is an error in the spec.
2330 GNAT provides an option for compiling such files purely for the
2331 purposes of checking correctness; such compilations are not required as
2332 part of the process of building a program. To compile a file in this
2333 checking mode, use the @option{-gnatc} switch.
2335 @node Source Dependencies
2336 @section Source Dependencies
2339 A given object file clearly depends on the source file which is compiled
2340 to produce it. Here we are using @dfn{depends} in the sense of a typical
2341 @code{make} utility; in other words, an object file depends on a source
2342 file if changes to the source file require the object file to be
2344 In addition to this basic dependency, a given object may depend on
2345 additional source files as follows:
2349 If a file being compiled @code{with}'s a unit @var{X}, the object file
2350 depends on the file containing the spec of unit @var{X}. This includes
2351 files that are @code{with}'ed implicitly either because they are parents
2352 of @code{with}'ed child units or they are run-time units required by the
2353 language constructs used in a particular unit.
2356 If a file being compiled instantiates a library level generic unit, the
2357 object file depends on both the spec and body files for this generic
2361 If a file being compiled instantiates a generic unit defined within a
2362 package, the object file depends on the body file for the package as
2363 well as the spec file.
2367 @cindex @option{-gnatn} switch
2368 If a file being compiled contains a call to a subprogram for which
2369 pragma @code{Inline} applies and inlining is activated with the
2370 @option{-gnatn} switch, the object file depends on the file containing the
2371 body of this subprogram as well as on the file containing the spec. Note
2372 that for inlining to actually occur as a result of the use of this switch,
2373 it is necessary to compile in optimizing mode.
2375 @cindex @option{-gnatN} switch
2376 The use of @option{-gnatN} activates inlining optimization
2377 that is performed by the front end of the compiler. This inlining does
2378 not require that the code generation be optimized. Like @option{-gnatn},
2379 the use of this switch generates additional dependencies.
2381 When using a gcc-based back end (in practice this means using any version
2382 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2383 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2384 Historically front end inlining was more extensive than the gcc back end
2385 inlining, but that is no longer the case.
2388 If an object file @file{O} depends on the proper body of a subunit through
2389 inlining or instantiation, it depends on the parent unit of the subunit.
2390 This means that any modification of the parent unit or one of its subunits
2391 affects the compilation of @file{O}.
2394 The object file for a parent unit depends on all its subunit body files.
2397 The previous two rules meant that for purposes of computing dependencies and
2398 recompilation, a body and all its subunits are treated as an indivisible whole.
2401 These rules are applied transitively: if unit @code{A} @code{with}'s
2402 unit @code{B}, whose elaboration calls an inlined procedure in package
2403 @code{C}, the object file for unit @code{A} will depend on the body of
2404 @code{C}, in file @file{c.adb}.
2406 The set of dependent files described by these rules includes all the
2407 files on which the unit is semantically dependent, as dictated by the
2408 Ada language standard. However, it is a superset of what the
2409 standard describes, because it includes generic, inline, and subunit
2412 An object file must be recreated by recompiling the corresponding source
2413 file if any of the source files on which it depends are modified. For
2414 example, if the @code{make} utility is used to control compilation,
2415 the rule for an Ada object file must mention all the source files on
2416 which the object file depends, according to the above definition.
2417 The determination of the necessary
2418 recompilations is done automatically when one uses @command{gnatmake}.
2421 @node The Ada Library Information Files
2422 @section The Ada Library Information Files
2423 @cindex Ada Library Information files
2424 @cindex @file{ALI} files
2427 Each compilation actually generates two output files. The first of these
2428 is the normal object file that has a @file{.o} extension. The second is a
2429 text file containing full dependency information. It has the same
2430 name as the source file, but an @file{.ali} extension.
2431 This file is known as the Ada Library Information (@file{ALI}) file.
2432 The following information is contained in the @file{ALI} file.
2436 Version information (indicates which version of GNAT was used to compile
2437 the unit(s) in question)
2440 Main program information (including priority and time slice settings,
2441 as well as the wide character encoding used during compilation).
2444 List of arguments used in the @command{gcc} command for the compilation
2447 Attributes of the unit, including configuration pragmas used, an indication
2448 of whether the compilation was successful, exception model used etc.
2451 A list of relevant restrictions applying to the unit (used for consistency)
2455 Categorization information (e.g.@: use of pragma @code{Pure}).
2458 Information on all @code{with}'ed units, including presence of
2459 @code{Elaborate} or @code{Elaborate_All} pragmas.
2462 Information from any @code{Linker_Options} pragmas used in the unit
2465 Information on the use of @code{Body_Version} or @code{Version}
2466 attributes in the unit.
2469 Dependency information. This is a list of files, together with
2470 time stamp and checksum information. These are files on which
2471 the unit depends in the sense that recompilation is required
2472 if any of these units are modified.
2475 Cross-reference data. Contains information on all entities referenced
2476 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2477 provide cross-reference information.
2482 For a full detailed description of the format of the @file{ALI} file,
2483 see the source of the body of unit @code{Lib.Writ}, contained in file
2484 @file{lib-writ.adb} in the GNAT compiler sources.
2486 @node Binding an Ada Program
2487 @section Binding an Ada Program
2490 When using languages such as C and C++, once the source files have been
2491 compiled the only remaining step in building an executable program
2492 is linking the object modules together. This means that it is possible to
2493 link an inconsistent version of a program, in which two units have
2494 included different versions of the same header.
2496 The rules of Ada do not permit such an inconsistent program to be built.
2497 For example, if two clients have different versions of the same package,
2498 it is illegal to build a program containing these two clients.
2499 These rules are enforced by the GNAT binder, which also determines an
2500 elaboration order consistent with the Ada rules.
2502 The GNAT binder is run after all the object files for a program have
2503 been created. It is given the name of the main program unit, and from
2504 this it determines the set of units required by the program, by reading the
2505 corresponding ALI files. It generates error messages if the program is
2506 inconsistent or if no valid order of elaboration exists.
2508 If no errors are detected, the binder produces a main program, in Ada by
2509 default, that contains calls to the elaboration procedures of those
2510 compilation unit that require them, followed by
2511 a call to the main program. This Ada program is compiled to generate the
2512 object file for the main program. The name of
2513 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2514 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2517 Finally, the linker is used to build the resulting executable program,
2518 using the object from the main program from the bind step as well as the
2519 object files for the Ada units of the program.
2521 @node Mixed Language Programming
2522 @section Mixed Language Programming
2523 @cindex Mixed Language Programming
2526 This section describes how to develop a mixed-language program,
2527 specifically one that comprises units in both Ada and C.
2530 * Interfacing to C::
2531 * Calling Conventions::
2534 @node Interfacing to C
2535 @subsection Interfacing to C
2537 Interfacing Ada with a foreign language such as C involves using
2538 compiler directives to import and/or export entity definitions in each
2539 language---using @code{extern} statements in C, for instance, and the
2540 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2541 A full treatment of these topics is provided in Appendix B, section 1
2542 of the Ada Reference Manual.
2544 There are two ways to build a program using GNAT that contains some Ada
2545 sources and some foreign language sources, depending on whether or not
2546 the main subprogram is written in Ada. Here is a source example with
2547 the main subprogram in Ada:
2553 void print_num (int num)
2555 printf ("num is %d.\n", num);
2561 /* num_from_Ada is declared in my_main.adb */
2562 extern int num_from_Ada;
2566 return num_from_Ada;
2570 @smallexample @c ada
2572 procedure My_Main is
2574 -- Declare then export an Integer entity called num_from_Ada
2575 My_Num : Integer := 10;
2576 pragma Export (C, My_Num, "num_from_Ada");
2578 -- Declare an Ada function spec for Get_Num, then use
2579 -- C function get_num for the implementation.
2580 function Get_Num return Integer;
2581 pragma Import (C, Get_Num, "get_num");
2583 -- Declare an Ada procedure spec for Print_Num, then use
2584 -- C function print_num for the implementation.
2585 procedure Print_Num (Num : Integer);
2586 pragma Import (C, Print_Num, "print_num");
2589 Print_Num (Get_Num);
2595 To build this example, first compile the foreign language files to
2596 generate object files:
2598 ^gcc -c file1.c^gcc -c FILE1.C^
2599 ^gcc -c file2.c^gcc -c FILE2.C^
2603 Then, compile the Ada units to produce a set of object files and ALI
2606 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2610 Run the Ada binder on the Ada main program:
2612 gnatbind my_main.ali
2616 Link the Ada main program, the Ada objects and the other language
2619 gnatlink my_main.ali file1.o file2.o
2623 The last three steps can be grouped in a single command:
2625 gnatmake my_main.adb -largs file1.o file2.o
2628 @cindex Binder output file
2630 If the main program is in a language other than Ada, then you may have
2631 more than one entry point into the Ada subsystem. You must use a special
2632 binder option to generate callable routines that initialize and
2633 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2634 Calls to the initialization and finalization routines must be inserted
2635 in the main program, or some other appropriate point in the code. The
2636 call to initialize the Ada units must occur before the first Ada
2637 subprogram is called, and the call to finalize the Ada units must occur
2638 after the last Ada subprogram returns. The binder will place the
2639 initialization and finalization subprograms into the
2640 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2641 sources. To illustrate, we have the following example:
2645 extern void adainit (void);
2646 extern void adafinal (void);
2647 extern int add (int, int);
2648 extern int sub (int, int);
2650 int main (int argc, char *argv[])
2656 /* Should print "21 + 7 = 28" */
2657 printf ("%d + %d = %d\n", a, b, add (a, b));
2658 /* Should print "21 - 7 = 14" */
2659 printf ("%d - %d = %d\n", a, b, sub (a, b));
2665 @smallexample @c ada
2668 function Add (A, B : Integer) return Integer;
2669 pragma Export (C, Add, "add");
2673 package body Unit1 is
2674 function Add (A, B : Integer) return Integer is
2682 function Sub (A, B : Integer) return Integer;
2683 pragma Export (C, Sub, "sub");
2687 package body Unit2 is
2688 function Sub (A, B : Integer) return Integer is
2697 The build procedure for this application is similar to the last
2698 example's. First, compile the foreign language files to generate object
2701 ^gcc -c main.c^gcc -c main.c^
2705 Next, compile the Ada units to produce a set of object files and ALI
2708 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2709 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2713 Run the Ada binder on every generated ALI file. Make sure to use the
2714 @option{-n} option to specify a foreign main program:
2716 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2720 Link the Ada main program, the Ada objects and the foreign language
2721 objects. You need only list the last ALI file here:
2723 gnatlink unit2.ali main.o -o exec_file
2726 This procedure yields a binary executable called @file{exec_file}.
2730 Depending on the circumstances (for example when your non-Ada main object
2731 does not provide symbol @code{main}), you may also need to instruct the
2732 GNAT linker not to include the standard startup objects by passing the
2733 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2735 @node Calling Conventions
2736 @subsection Calling Conventions
2737 @cindex Foreign Languages
2738 @cindex Calling Conventions
2739 GNAT follows standard calling sequence conventions and will thus interface
2740 to any other language that also follows these conventions. The following
2741 Convention identifiers are recognized by GNAT:
2744 @cindex Interfacing to Ada
2745 @cindex Other Ada compilers
2746 @cindex Convention Ada
2748 This indicates that the standard Ada calling sequence will be
2749 used and all Ada data items may be passed without any limitations in the
2750 case where GNAT is used to generate both the caller and callee. It is also
2751 possible to mix GNAT generated code and code generated by another Ada
2752 compiler. In this case, the data types should be restricted to simple
2753 cases, including primitive types. Whether complex data types can be passed
2754 depends on the situation. Probably it is safe to pass simple arrays, such
2755 as arrays of integers or floats. Records may or may not work, depending
2756 on whether both compilers lay them out identically. Complex structures
2757 involving variant records, access parameters, tasks, or protected types,
2758 are unlikely to be able to be passed.
2760 Note that in the case of GNAT running
2761 on a platform that supports HP Ada 83, a higher degree of compatibility
2762 can be guaranteed, and in particular records are layed out in an identical
2763 manner in the two compilers. Note also that if output from two different
2764 compilers is mixed, the program is responsible for dealing with elaboration
2765 issues. Probably the safest approach is to write the main program in the
2766 version of Ada other than GNAT, so that it takes care of its own elaboration
2767 requirements, and then call the GNAT-generated adainit procedure to ensure
2768 elaboration of the GNAT components. Consult the documentation of the other
2769 Ada compiler for further details on elaboration.
2771 However, it is not possible to mix the tasking run time of GNAT and
2772 HP Ada 83, All the tasking operations must either be entirely within
2773 GNAT compiled sections of the program, or entirely within HP Ada 83
2774 compiled sections of the program.
2776 @cindex Interfacing to Assembly
2777 @cindex Convention Assembler
2779 Specifies assembler as the convention. In practice this has the
2780 same effect as convention Ada (but is not equivalent in the sense of being
2781 considered the same convention).
2783 @cindex Convention Asm
2786 Equivalent to Assembler.
2788 @cindex Interfacing to COBOL
2789 @cindex Convention COBOL
2792 Data will be passed according to the conventions described
2793 in section B.4 of the Ada Reference Manual.
2796 @cindex Interfacing to C
2797 @cindex Convention C
2799 Data will be passed according to the conventions described
2800 in section B.3 of the Ada Reference Manual.
2802 A note on interfacing to a C ``varargs'' function:
2803 @findex C varargs function
2804 @cindex Interfacing to C varargs function
2805 @cindex varargs function interfaces
2809 In C, @code{varargs} allows a function to take a variable number of
2810 arguments. There is no direct equivalent in this to Ada. One
2811 approach that can be used is to create a C wrapper for each
2812 different profile and then interface to this C wrapper. For
2813 example, to print an @code{int} value using @code{printf},
2814 create a C function @code{printfi} that takes two arguments, a
2815 pointer to a string and an int, and calls @code{printf}.
2816 Then in the Ada program, use pragma @code{Import} to
2817 interface to @code{printfi}.
2820 It may work on some platforms to directly interface to
2821 a @code{varargs} function by providing a specific Ada profile
2822 for a particular call. However, this does not work on
2823 all platforms, since there is no guarantee that the
2824 calling sequence for a two argument normal C function
2825 is the same as for calling a @code{varargs} C function with
2826 the same two arguments.
2829 @cindex Convention Default
2834 @cindex Convention External
2841 @cindex Interfacing to C++
2842 @cindex Convention C++
2843 @item C_Plus_Plus (or CPP)
2844 This stands for C++. For most purposes this is identical to C.
2845 See the separate description of the specialized GNAT pragmas relating to
2846 C++ interfacing for further details.
2850 @cindex Interfacing to Fortran
2851 @cindex Convention Fortran
2853 Data will be passed according to the conventions described
2854 in section B.5 of the Ada Reference Manual.
2857 This applies to an intrinsic operation, as defined in the Ada
2858 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2859 this means that the body of the subprogram is provided by the compiler itself,
2860 usually by means of an efficient code sequence, and that the user does not
2861 supply an explicit body for it. In an application program, the pragma may
2862 be applied to the following sets of names:
2866 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2867 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2868 two formal parameters. The
2869 first one must be a signed integer type or a modular type with a binary
2870 modulus, and the second parameter must be of type Natural.
2871 The return type must be the same as the type of the first argument. The size
2872 of this type can only be 8, 16, 32, or 64.
2875 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2876 The corresponding operator declaration must have parameters and result type
2877 that have the same root numeric type (for example, all three are long_float
2878 types). This simplifies the definition of operations that use type checking
2879 to perform dimensional checks:
2881 @smallexample @c ada
2882 type Distance is new Long_Float;
2883 type Time is new Long_Float;
2884 type Velocity is new Long_Float;
2885 function "/" (D : Distance; T : Time)
2887 pragma Import (Intrinsic, "/");
2891 This common idiom is often programmed with a generic definition and an
2892 explicit body. The pragma makes it simpler to introduce such declarations.
2893 It incurs no overhead in compilation time or code size, because it is
2894 implemented as a single machine instruction.
2897 General subprogram entities, to bind an Ada subprogram declaration to
2898 a compiler builtin by name with back-ends where such interfaces are
2899 available. A typical example is the set of ``__builtin'' functions
2900 exposed by the GCC back-end, as in the following example:
2902 @smallexample @c ada
2903 function builtin_sqrt (F : Float) return Float;
2904 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2907 Most of the GCC builtins are accessible this way, and as for other
2908 import conventions (e.g. C), it is the user's responsibility to ensure
2909 that the Ada subprogram profile matches the underlying builtin
2917 @cindex Convention Stdcall
2919 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2920 and specifies that the @code{Stdcall} calling sequence will be used,
2921 as defined by the NT API. Nevertheless, to ease building
2922 cross-platform bindings this convention will be handled as a @code{C} calling
2923 convention on non-Windows platforms.
2926 @cindex Convention DLL
2928 This is equivalent to @code{Stdcall}.
2931 @cindex Convention Win32
2933 This is equivalent to @code{Stdcall}.
2937 @cindex Convention Stubbed
2939 This is a special convention that indicates that the compiler
2940 should provide a stub body that raises @code{Program_Error}.
2944 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2945 that can be used to parametrize conventions and allow additional synonyms
2946 to be specified. For example if you have legacy code in which the convention
2947 identifier Fortran77 was used for Fortran, you can use the configuration
2950 @smallexample @c ada
2951 pragma Convention_Identifier (Fortran77, Fortran);
2955 And from now on the identifier Fortran77 may be used as a convention
2956 identifier (for example in an @code{Import} pragma) with the same
2960 @node Building Mixed Ada & C++ Programs
2961 @section Building Mixed Ada and C++ Programs
2964 A programmer inexperienced with mixed-language development may find that
2965 building an application containing both Ada and C++ code can be a
2966 challenge. This section gives a few
2967 hints that should make this task easier. The first section addresses
2968 the differences between interfacing with C and interfacing with C++.
2970 looks into the delicate problem of linking the complete application from
2971 its Ada and C++ parts. The last section gives some hints on how the GNAT
2972 run-time library can be adapted in order to allow inter-language dispatching
2973 with a new C++ compiler.
2976 * Interfacing to C++::
2977 * Linking a Mixed C++ & Ada Program::
2978 * A Simple Example::
2979 * Interfacing with C++ at the Class Level::
2982 @node Interfacing to C++
2983 @subsection Interfacing to C++
2986 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2987 generating code that is compatible with the G++ Application Binary
2988 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2991 Interfacing can be done at 3 levels: simple data, subprograms, and
2992 classes. In the first two cases, GNAT offers a specific @code{Convention
2993 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2994 Usually, C++ mangles the names of subprograms, and currently, GNAT does
2995 not provide any help to solve the demangling problem. This problem can be
2996 addressed in two ways:
2999 by modifying the C++ code in order to force a C convention using
3000 the @code{extern "C"} syntax.
3003 by figuring out the mangled name and use it as the Link_Name argument of
3008 Interfacing at the class level can be achieved by using the GNAT specific
3009 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3010 gnat_rm, GNAT Reference Manual}, for additional information.
3012 @node Linking a Mixed C++ & Ada Program
3013 @subsection Linking a Mixed C++ & Ada Program
3016 Usually the linker of the C++ development system must be used to link
3017 mixed applications because most C++ systems will resolve elaboration
3018 issues (such as calling constructors on global class instances)
3019 transparently during the link phase. GNAT has been adapted to ease the
3020 use of a foreign linker for the last phase. Three cases can be
3025 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3026 The C++ linker can simply be called by using the C++ specific driver
3027 called @code{c++}. Note that this setup is not very common because it
3028 may involve recompiling the whole GCC tree from sources, which makes it
3029 harder to upgrade the compilation system for one language without
3030 destabilizing the other.
3035 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3039 Using GNAT and G++ from two different GCC installations: If both
3040 compilers are on the @env{PATH}, the previous method may be used. It is
3041 important to note that environment variables such as
3042 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3043 @env{GCC_ROOT} will affect both compilers
3044 at the same time and may make one of the two compilers operate
3045 improperly if set during invocation of the wrong compiler. It is also
3046 very important that the linker uses the proper @file{libgcc.a} GCC
3047 library -- that is, the one from the C++ compiler installation. The
3048 implicit link command as suggested in the @command{gnatmake} command
3049 from the former example can be replaced by an explicit link command with
3050 the full-verbosity option in order to verify which library is used:
3053 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3055 If there is a problem due to interfering environment variables, it can
3056 be worked around by using an intermediate script. The following example
3057 shows the proper script to use when GNAT has not been installed at its
3058 default location and g++ has been installed at its default location:
3066 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3070 Using a non-GNU C++ compiler: The commands previously described can be
3071 used to insure that the C++ linker is used. Nonetheless, you need to add
3072 a few more parameters to the link command line, depending on the exception
3075 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3076 to the libgcc libraries are required:
3081 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3082 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3085 Where CC is the name of the non-GNU C++ compiler.
3087 If the @code{zero cost} exception mechanism is used, and the platform
3088 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3089 paths to more objects are required:
3094 CC `gcc -print-file-name=crtbegin.o` $* \
3095 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3096 `gcc -print-file-name=crtend.o`
3097 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3100 If the @code{zero cost} exception mechanism is used, and the platform
3101 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3102 Tru64 or AIX), the simple approach described above will not work and
3103 a pre-linking phase using GNAT will be necessary.
3107 @node A Simple Example
3108 @subsection A Simple Example
3110 The following example, provided as part of the GNAT examples, shows how
3111 to achieve procedural interfacing between Ada and C++ in both
3112 directions. The C++ class A has two methods. The first method is exported
3113 to Ada by the means of an extern C wrapper function. The second method
3114 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3115 a limited record with a layout comparable to the C++ class. The Ada
3116 subprogram, in turn, calls the C++ method. So, starting from the C++
3117 main program, the process passes back and forth between the two
3121 Here are the compilation commands:
3123 $ gnatmake -c simple_cpp_interface
3126 $ gnatbind -n simple_cpp_interface
3127 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3128 -lstdc++ ex7.o cpp_main.o
3132 Here are the corresponding sources:
3140 void adainit (void);
3141 void adafinal (void);
3142 void method1 (A *t);
3164 class A : public Origin @{
3166 void method1 (void);
3167 void method2 (int v);
3177 extern "C" @{ void ada_method2 (A *t, int v);@}
3179 void A::method1 (void)
3182 printf ("in A::method1, a_value = %d \n",a_value);
3186 void A::method2 (int v)
3188 ada_method2 (this, v);
3189 printf ("in A::method2, a_value = %d \n",a_value);
3196 printf ("in A::A, a_value = %d \n",a_value);
3200 @smallexample @c ada
3202 package body Simple_Cpp_Interface is
3204 procedure Ada_Method2 (This : in out A; V : Integer) is
3210 end Simple_Cpp_Interface;
3213 package Simple_Cpp_Interface is
3216 Vptr : System.Address;
3220 pragma Convention (C, A);
3222 procedure Method1 (This : in out A);
3223 pragma Import (C, Method1);
3225 procedure Ada_Method2 (This : in out A; V : Integer);
3226 pragma Export (C, Ada_Method2);
3228 end Simple_Cpp_Interface;
3231 @node Interfacing with C++ at the Class Level
3232 @subsection Interfacing with C++ at the Class Level
3234 In this section we demonstrate the GNAT features for interfacing with
3235 C++ by means of an example making use of Ada 2005 abstract interface
3236 types. This example consists of a classification of animals; classes
3237 have been used to model our main classification of animals, and
3238 interfaces provide support for the management of secondary
3239 classifications. We first demonstrate a case in which the types and
3240 constructors are defined on the C++ side and imported from the Ada
3241 side, and latter the reverse case.
3243 The root of our derivation will be the @code{Animal} class, with a
3244 single private attribute (the @code{Age} of the animal) and two public
3245 primitives to set and get the value of this attribute.
3250 @b{virtual} void Set_Age (int New_Age);
3251 @b{virtual} int Age ();
3257 Abstract interface types are defined in C++ by means of classes with pure
3258 virtual functions and no data members. In our example we will use two
3259 interfaces that provide support for the common management of @code{Carnivore}
3260 and @code{Domestic} animals:
3263 @b{class} Carnivore @{
3265 @b{virtual} int Number_Of_Teeth () = 0;
3268 @b{class} Domestic @{
3270 @b{virtual void} Set_Owner (char* Name) = 0;
3274 Using these declarations, we can now say that a @code{Dog} is an animal that is
3275 both Carnivore and Domestic, that is:
3278 @b{class} Dog : Animal, Carnivore, Domestic @{
3280 @b{virtual} int Number_Of_Teeth ();
3281 @b{virtual} void Set_Owner (char* Name);
3283 Dog(); // Constructor
3290 In the following examples we will assume that the previous declarations are
3291 located in a file named @code{animals.h}. The following package demonstrates
3292 how to import these C++ declarations from the Ada side:
3294 @smallexample @c ada
3295 with Interfaces.C.Strings; use Interfaces.C.Strings;
3297 type Carnivore is interface;
3298 pragma Convention (C_Plus_Plus, Carnivore);
3299 function Number_Of_Teeth (X : Carnivore)
3300 return Natural is abstract;
3302 type Domestic is interface;
3303 pragma Convention (C_Plus_Plus, Set_Owner);
3305 (X : in out Domestic;
3306 Name : Chars_Ptr) is abstract;
3308 type Animal is tagged record
3311 pragma Import (C_Plus_Plus, Animal);
3313 procedure Set_Age (X : in out Animal; Age : Integer);
3314 pragma Import (C_Plus_Plus, Set_Age);
3316 function Age (X : Animal) return Integer;
3317 pragma Import (C_Plus_Plus, Age);
3319 type Dog is new Animal and Carnivore and Domestic with record
3320 Tooth_Count : Natural;
3321 Owner : String (1 .. 30);
3323 pragma Import (C_Plus_Plus, Dog);
3325 function Number_Of_Teeth (A : Dog) return Integer;
3326 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3328 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3329 pragma Import (C_Plus_Plus, Set_Owner);
3331 function New_Dog return Dog'Class;
3332 pragma CPP_Constructor (New_Dog);
3333 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3337 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3338 interfacing with these C++ classes is easy. The only requirement is that all
3339 the primitives and components must be declared exactly in the same order in
3342 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3343 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3344 the arguments to the called primitives will be the same as for C++. For the
3345 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3346 to indicate that they have been defined on the C++ side; this is required
3347 because the dispatch table associated with these tagged types will be built
3348 in the C++ side and therefore will not contain the predefined Ada primitives
3349 which Ada would otherwise expect.
3351 As the reader can see there is no need to indicate the C++ mangled names
3352 associated with each subprogram because it is assumed that all the calls to
3353 these primitives will be dispatching calls. The only exception is the
3354 constructor, which must be registered with the compiler by means of
3355 @code{pragma CPP_Constructor} and needs to provide its associated C++
3356 mangled name because the Ada compiler generates direct calls to it.
3358 With the above packages we can now declare objects of type Dog on the Ada side
3359 and dispatch calls to the corresponding subprograms on the C++ side. We can
3360 also extend the tagged type Dog with further fields and primitives, and
3361 override some of its C++ primitives on the Ada side. For example, here we have
3362 a type derivation defined on the Ada side that inherits all the dispatching
3363 primitives of the ancestor from the C++ side.
3366 @b{with} Animals; @b{use} Animals;
3367 @b{package} Vaccinated_Animals @b{is}
3368 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3369 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3370 @b{end} Vaccinated_Animals;
3373 It is important to note that, because of the ABI compatibility, the programmer
3374 does not need to add any further information to indicate either the object
3375 layout or the dispatch table entry associated with each dispatching operation.
3377 Now let us define all the types and constructors on the Ada side and export
3378 them to C++, using the same hierarchy of our previous example:
3380 @smallexample @c ada
3381 with Interfaces.C.Strings;
3382 use Interfaces.C.Strings;
3384 type Carnivore is interface;
3385 pragma Convention (C_Plus_Plus, Carnivore);
3386 function Number_Of_Teeth (X : Carnivore)
3387 return Natural is abstract;
3389 type Domestic is interface;
3390 pragma Convention (C_Plus_Plus, Set_Owner);
3392 (X : in out Domestic;
3393 Name : Chars_Ptr) is abstract;
3395 type Animal is tagged record
3398 pragma Convention (C_Plus_Plus, Animal);
3400 procedure Set_Age (X : in out Animal; Age : Integer);
3401 pragma Export (C_Plus_Plus, Set_Age);
3403 function Age (X : Animal) return Integer;
3404 pragma Export (C_Plus_Plus, Age);
3406 type Dog is new Animal and Carnivore and Domestic with record
3407 Tooth_Count : Natural;
3408 Owner : String (1 .. 30);
3410 pragma Convention (C_Plus_Plus, Dog);
3412 function Number_Of_Teeth (A : Dog) return Integer;
3413 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3415 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3416 pragma Export (C_Plus_Plus, Set_Owner);
3418 function New_Dog return Dog'Class;
3419 pragma Export (C_Plus_Plus, New_Dog);
3423 Compared with our previous example the only difference is the use of
3424 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3425 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3426 nothing else to be done; as explained above, the only requirement is that all
3427 the primitives and components are declared in exactly the same order.
3429 For completeness, let us see a brief C++ main program that uses the
3430 declarations available in @code{animals.h} (presented in our first example) to
3431 import and use the declarations from the Ada side, properly initializing and
3432 finalizing the Ada run-time system along the way:
3435 @b{#include} "animals.h"
3436 @b{#include} <iostream>
3437 @b{using namespace} std;
3439 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3440 void Check_Domestic (Domestic *obj) @{@dots{}@}
3441 void Check_Animal (Animal *obj) @{@dots{}@}
3442 void Check_Dog (Dog *obj) @{@dots{}@}
3445 void adainit (void);
3446 void adafinal (void);
3452 Dog *obj = new_dog(); // Ada constructor
3453 Check_Carnivore (obj); // Check secondary DT
3454 Check_Domestic (obj); // Check secondary DT
3455 Check_Animal (obj); // Check primary DT
3456 Check_Dog (obj); // Check primary DT
3461 adainit (); test(); adafinal ();
3466 @node Comparison between GNAT and C/C++ Compilation Models
3467 @section Comparison between GNAT and C/C++ Compilation Models
3470 The GNAT model of compilation is close to the C and C++ models. You can
3471 think of Ada specs as corresponding to header files in C. As in C, you
3472 don't need to compile specs; they are compiled when they are used. The
3473 Ada @code{with} is similar in effect to the @code{#include} of a C
3476 One notable difference is that, in Ada, you may compile specs separately
3477 to check them for semantic and syntactic accuracy. This is not always
3478 possible with C headers because they are fragments of programs that have
3479 less specific syntactic or semantic rules.
3481 The other major difference is the requirement for running the binder,
3482 which performs two important functions. First, it checks for
3483 consistency. In C or C++, the only defense against assembling
3484 inconsistent programs lies outside the compiler, in a makefile, for
3485 example. The binder satisfies the Ada requirement that it be impossible
3486 to construct an inconsistent program when the compiler is used in normal
3489 @cindex Elaboration order control
3490 The other important function of the binder is to deal with elaboration
3491 issues. There are also elaboration issues in C++ that are handled
3492 automatically. This automatic handling has the advantage of being
3493 simpler to use, but the C++ programmer has no control over elaboration.
3494 Where @code{gnatbind} might complain there was no valid order of
3495 elaboration, a C++ compiler would simply construct a program that
3496 malfunctioned at run time.
3499 @node Comparison between GNAT and Conventional Ada Library Models
3500 @section Comparison between GNAT and Conventional Ada Library Models
3503 This section is intended for Ada programmers who have
3504 used an Ada compiler implementing the traditional Ada library
3505 model, as described in the Ada Reference Manual.
3507 @cindex GNAT library
3508 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3509 source files themselves acts as the library. Compiling Ada programs does
3510 not generate any centralized information, but rather an object file and
3511 a ALI file, which are of interest only to the binder and linker.
3512 In a traditional system, the compiler reads information not only from
3513 the source file being compiled, but also from the centralized library.
3514 This means that the effect of a compilation depends on what has been
3515 previously compiled. In particular:
3519 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3520 to the version of the unit most recently compiled into the library.
3523 Inlining is effective only if the necessary body has already been
3524 compiled into the library.
3527 Compiling a unit may obsolete other units in the library.
3531 In GNAT, compiling one unit never affects the compilation of any other
3532 units because the compiler reads only source files. Only changes to source
3533 files can affect the results of a compilation. In particular:
3537 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3538 to the source version of the unit that is currently accessible to the
3543 Inlining requires the appropriate source files for the package or
3544 subprogram bodies to be available to the compiler. Inlining is always
3545 effective, independent of the order in which units are complied.
3548 Compiling a unit never affects any other compilations. The editing of
3549 sources may cause previous compilations to be out of date if they
3550 depended on the source file being modified.
3554 The most important result of these differences is that order of compilation
3555 is never significant in GNAT. There is no situation in which one is
3556 required to do one compilation before another. What shows up as order of
3557 compilation requirements in the traditional Ada library becomes, in
3558 GNAT, simple source dependencies; in other words, there is only a set
3559 of rules saying what source files must be present when a file is
3563 @node Placement of temporary files
3564 @section Placement of temporary files
3565 @cindex Temporary files (user control over placement)
3568 GNAT creates temporary files in the directory designated by the environment
3569 variable @env{TMPDIR}.
3570 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3571 for detailed information on how environment variables are resolved.
3572 For most users the easiest way to make use of this feature is to simply
3573 define @env{TMPDIR} as a job level logical name).
3574 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3575 for compiler temporary files, then you can include something like the
3576 following command in your @file{LOGIN.COM} file:
3579 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3583 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3584 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3585 designated by @env{TEMP}.
3586 If none of these environment variables are defined then GNAT uses the
3587 directory designated by the logical name @code{SYS$SCRATCH:}
3588 (by default the user's home directory). If all else fails
3589 GNAT uses the current directory for temporary files.
3592 @c *************************
3593 @node Compiling Using gcc
3594 @chapter Compiling Using @command{gcc}
3597 This chapter discusses how to compile Ada programs using the @command{gcc}
3598 command. It also describes the set of switches
3599 that can be used to control the behavior of the compiler.
3601 * Compiling Programs::
3602 * Switches for gcc::
3603 * Search Paths and the Run-Time Library (RTL)::
3604 * Order of Compilation Issues::
3608 @node Compiling Programs
3609 @section Compiling Programs
3612 The first step in creating an executable program is to compile the units
3613 of the program using the @command{gcc} command. You must compile the
3618 the body file (@file{.adb}) for a library level subprogram or generic
3622 the spec file (@file{.ads}) for a library level package or generic
3623 package that has no body
3626 the body file (@file{.adb}) for a library level package
3627 or generic package that has a body
3632 You need @emph{not} compile the following files
3637 the spec of a library unit which has a body
3644 because they are compiled as part of compiling related units. GNAT
3646 when the corresponding body is compiled, and subunits when the parent is
3649 @cindex cannot generate code
3650 If you attempt to compile any of these files, you will get one of the
3651 following error messages (where @var{fff} is the name of the file you compiled):
3654 cannot generate code for file @var{fff} (package spec)
3655 to check package spec, use -gnatc
3657 cannot generate code for file @var{fff} (missing subunits)
3658 to check parent unit, use -gnatc
3660 cannot generate code for file @var{fff} (subprogram spec)
3661 to check subprogram spec, use -gnatc
3663 cannot generate code for file @var{fff} (subunit)
3664 to check subunit, use -gnatc
3668 As indicated by the above error messages, if you want to submit
3669 one of these files to the compiler to check for correct semantics
3670 without generating code, then use the @option{-gnatc} switch.
3672 The basic command for compiling a file containing an Ada unit is
3675 $ gcc -c @ovar{switches} @file{file name}
3679 where @var{file name} is the name of the Ada file (usually
3681 @file{.ads} for a spec or @file{.adb} for a body).
3684 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3686 The result of a successful compilation is an object file, which has the
3687 same name as the source file but an extension of @file{.o} and an Ada
3688 Library Information (ALI) file, which also has the same name as the
3689 source file, but with @file{.ali} as the extension. GNAT creates these
3690 two output files in the current directory, but you may specify a source
3691 file in any directory using an absolute or relative path specification
3692 containing the directory information.
3695 @command{gcc} is actually a driver program that looks at the extensions of
3696 the file arguments and loads the appropriate compiler. For example, the
3697 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3698 These programs are in directories known to the driver program (in some
3699 configurations via environment variables you set), but need not be in
3700 your path. The @command{gcc} driver also calls the assembler and any other
3701 utilities needed to complete the generation of the required object
3704 It is possible to supply several file names on the same @command{gcc}
3705 command. This causes @command{gcc} to call the appropriate compiler for
3706 each file. For example, the following command lists three separate
3707 files to be compiled:
3710 $ gcc -c x.adb y.adb z.c
3714 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3715 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3716 The compiler generates three object files @file{x.o}, @file{y.o} and
3717 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3718 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3721 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3724 @node Switches for gcc
3725 @section Switches for @command{gcc}
3728 The @command{gcc} command accepts switches that control the
3729 compilation process. These switches are fully described in this section.
3730 First we briefly list all the switches, in alphabetical order, then we
3731 describe the switches in more detail in functionally grouped sections.
3733 More switches exist for GCC than those documented here, especially
3734 for specific targets. However, their use is not recommended as
3735 they may change code generation in ways that are incompatible with
3736 the Ada run-time library, or can cause inconsistencies between
3740 * Output and Error Message Control::
3741 * Warning Message Control::
3742 * Debugging and Assertion Control::
3743 * Validity Checking::
3746 * Using gcc for Syntax Checking::
3747 * Using gcc for Semantic Checking::
3748 * Compiling Different Versions of Ada::
3749 * Character Set Control::
3750 * File Naming Control::
3751 * Subprogram Inlining Control::
3752 * Auxiliary Output Control::
3753 * Debugging Control::
3754 * Exception Handling Control::
3755 * Units to Sources Mapping Files::
3756 * Integrated Preprocessing::
3757 * Code Generation Control::
3766 @cindex @option{-b} (@command{gcc})
3767 @item -b @var{target}
3768 Compile your program to run on @var{target}, which is the name of a
3769 system configuration. You must have a GNAT cross-compiler built if
3770 @var{target} is not the same as your host system.
3773 @cindex @option{-B} (@command{gcc})
3774 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3775 from @var{dir} instead of the default location. Only use this switch
3776 when multiple versions of the GNAT compiler are available.
3777 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3778 GNU Compiler Collection (GCC)}, for further details. You would normally
3779 use the @option{-b} or @option{-V} switch instead.
3782 @cindex @option{-c} (@command{gcc})
3783 Compile. Always use this switch when compiling Ada programs.
3785 Note: for some other languages when using @command{gcc}, notably in
3786 the case of C and C++, it is possible to use
3787 use @command{gcc} without a @option{-c} switch to
3788 compile and link in one step. In the case of GNAT, you
3789 cannot use this approach, because the binder must be run
3790 and @command{gcc} cannot be used to run the GNAT binder.
3794 @cindex @option{-fno-inline} (@command{gcc})
3795 Suppresses all back-end inlining, even if other optimization or inlining
3797 This includes suppression of inlining that results
3798 from the use of the pragma @code{Inline_Always}.
3799 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3800 are ignored, and @option{-gnatn} and @option{-gnatN} have no
3801 effect if this switch is present.
3803 @item -fno-inline-functions
3804 @cindex @option{-fno-inline-functions} (@command{gcc})
3805 Suppresses automatic inlining of simple subprograms, which is enabled
3806 if @option{-O3} is used.
3808 @item -fno-inline-small-functions
3809 @cindex @option{-fno-inline-small-functions} (@command{gcc})
3810 Suppresses automatic inlining of small subprograms, which is enabled
3811 if @option{-O2} is used.
3813 @item -fno-inline-functions-called-once
3814 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
3815 Suppresses inlining of subprograms local to the unit and called once
3816 from within it, which is enabled if @option{-O1} is used.
3818 @item -fno-strict-aliasing
3819 @cindex @option{-fno-strict-aliasing} (@command{gcc})
3820 Causes the compiler to avoid assumptions regarding non-aliasing
3821 of objects of different types. See
3822 @ref{Optimization and Strict Aliasing} for details.
3825 @cindex @option{-fstack-check} (@command{gcc})
3826 Activates stack checking.
3827 See @ref{Stack Overflow Checking} for details.
3830 @cindex @option{-fstack-usage} (@command{gcc})
3831 Makes the compiler output stack usage information for the program, on a
3832 per-function basis. See @ref{Static Stack Usage Analysis} for details.
3834 @item -fcallgraph-info@r{[}=su@r{]}
3835 @cindex @option{-fcallgraph-info} (@command{gcc})
3836 Makes the compiler output callgraph information for the program, on a
3837 per-file basis. The information is generated in the VCG format. It can
3838 be decorated with stack-usage per-node information.
3841 @cindex @option{^-g^/DEBUG^} (@command{gcc})
3842 Generate debugging information. This information is stored in the object
3843 file and copied from there to the final executable file by the linker,
3844 where it can be read by the debugger. You must use the
3845 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3848 @cindex @option{-gnat83} (@command{gcc})
3849 Enforce Ada 83 restrictions.
3852 @cindex @option{-gnat95} (@command{gcc})
3853 Enforce Ada 95 restrictions.
3856 @cindex @option{-gnat05} (@command{gcc})
3857 Allow full Ada 2005 features.
3860 @cindex @option{-gnata} (@command{gcc})
3861 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3862 activated. Note that these pragmas can also be controlled using the
3863 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
3864 It also activates pragmas @code{Check}, @code{Precondition}, and
3865 @code{Postcondition}. Note that these pragmas can also be controlled
3866 using the configuration pragma @code{Check_Policy}.
3869 @cindex @option{-gnatA} (@command{gcc})
3870 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
3874 @cindex @option{-gnatb} (@command{gcc})
3875 Generate brief messages to @file{stderr} even if verbose mode set.
3878 @cindex @option{-gnatB} (@command{gcc})
3879 Assume no invalid (bad) values except for 'Valid attribute use.
3882 @cindex @option{-gnatc} (@command{gcc})
3883 Check syntax and semantics only (no code generation attempted).
3886 @cindex @option{-gnatd} (@command{gcc})
3887 Specify debug options for the compiler. The string of characters after
3888 the @option{-gnatd} specify the specific debug options. The possible
3889 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3890 compiler source file @file{debug.adb} for details of the implemented
3891 debug options. Certain debug options are relevant to applications
3892 programmers, and these are documented at appropriate points in this
3897 @cindex @option{-gnatD[nn]} (@command{gcc})
3900 @item /XDEBUG /LXDEBUG=nnn
3902 Create expanded source files for source level debugging. This switch
3903 also suppress generation of cross-reference information
3904 (see @option{-gnatx}).
3906 @item -gnatec=@var{path}
3907 @cindex @option{-gnatec} (@command{gcc})
3908 Specify a configuration pragma file
3910 (the equal sign is optional)
3912 (@pxref{The Configuration Pragmas Files}).
3914 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
3915 @cindex @option{-gnateD} (@command{gcc})
3916 Defines a symbol, associated with @var{value}, for preprocessing.
3917 (@pxref{Integrated Preprocessing}).
3920 @cindex @option{-gnatef} (@command{gcc})
3921 Display full source path name in brief error messages.
3924 @cindex @option{-gnateG} (@command{gcc})
3925 Save result of preprocessing in a text file.
3927 @item -gnatem=@var{path}
3928 @cindex @option{-gnatem} (@command{gcc})
3929 Specify a mapping file
3931 (the equal sign is optional)
3933 (@pxref{Units to Sources Mapping Files}).
3935 @item -gnatep=@var{file}
3936 @cindex @option{-gnatep} (@command{gcc})
3937 Specify a preprocessing data file
3939 (the equal sign is optional)
3941 (@pxref{Integrated Preprocessing}).
3944 @cindex @option{-gnatE} (@command{gcc})
3945 Full dynamic elaboration checks.
3948 @cindex @option{-gnatf} (@command{gcc})
3949 Full errors. Multiple errors per line, all undefined references, do not
3950 attempt to suppress cascaded errors.
3953 @cindex @option{-gnatF} (@command{gcc})
3954 Externals names are folded to all uppercase.
3956 @item ^-gnatg^/GNAT_INTERNAL^
3957 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
3958 Internal GNAT implementation mode. This should not be used for
3959 applications programs, it is intended only for use by the compiler
3960 and its run-time library. For documentation, see the GNAT sources.
3961 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
3962 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
3963 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
3964 so that all standard warnings and all standard style options are turned on.
3965 All warnings and style error messages are treated as errors.
3969 @cindex @option{-gnatG[nn]} (@command{gcc})
3972 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
3974 List generated expanded code in source form.
3976 @item ^-gnath^/HELP^
3977 @cindex @option{^-gnath^/HELP^} (@command{gcc})
3978 Output usage information. The output is written to @file{stdout}.
3980 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3981 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
3982 Identifier character set
3984 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3986 For details of the possible selections for @var{c},
3987 see @ref{Character Set Control}.
3989 @item ^-gnatI^/IGNORE_REP_CLAUSES^
3990 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
3991 Ignore representation clauses. When this switch is used, all
3992 representation clauses are treated as comments. This is useful
3993 when initially porting code where you want to ignore rep clause
3994 problems, and also for compiling foreign code (particularly
3998 @cindex @option{-gnatjnn} (@command{gcc})
3999 Reformat error messages to fit on nn character lines
4001 @item -gnatk=@var{n}
4002 @cindex @option{-gnatk} (@command{gcc})
4003 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4006 @cindex @option{-gnatl} (@command{gcc})
4007 Output full source listing with embedded error messages.
4010 @cindex @option{-gnatL} (@command{gcc})
4011 Used in conjunction with -gnatG or -gnatD to intersperse original
4012 source lines (as comment lines with line numbers) in the expanded
4015 @item -gnatm=@var{n}
4016 @cindex @option{-gnatm} (@command{gcc})
4017 Limit number of detected error or warning messages to @var{n}
4018 where @var{n} is in the range 1..999999. The default setting if
4019 no switch is given is 9999. If the number of warnings reaches this
4020 limit, then a message is output and further warnings are suppressed,
4021 but the compilation is continued. If the number of error messages
4022 reaches this limit, then a message is output and the compilation
4023 is abandoned. The equal sign here is optional. A value of zero
4024 means that no limit applies.
4027 @cindex @option{-gnatn} (@command{gcc})
4028 Activate inlining for subprograms for which
4029 pragma @code{inline} is specified. This inlining is performed
4030 by the GCC back-end.
4033 @cindex @option{-gnatN} (@command{gcc})
4034 Activate front end inlining for subprograms for which
4035 pragma @code{Inline} is specified. This inlining is performed
4036 by the front end and will be visible in the
4037 @option{-gnatG} output.
4039 When using a gcc-based back end (in practice this means using any version
4040 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4041 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4042 Historically front end inlining was more extensive than the gcc back end
4043 inlining, but that is no longer the case.
4046 @cindex @option{-gnato} (@command{gcc})
4047 Enable numeric overflow checking (which is not normally enabled by
4048 default). Note that division by zero is a separate check that is not
4049 controlled by this switch (division by zero checking is on by default).
4052 @cindex @option{-gnatp} (@command{gcc})
4053 Suppress all checks. See @ref{Run-Time Checks} for details.
4056 @cindex @option{-gnatP} (@command{gcc})
4057 Enable polling. This is required on some systems (notably Windows NT) to
4058 obtain asynchronous abort and asynchronous transfer of control capability.
4059 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4063 @cindex @option{-gnatq} (@command{gcc})
4064 Don't quit. Try semantics, even if parse errors.
4067 @cindex @option{-gnatQ} (@command{gcc})
4068 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4071 @cindex @option{-gnatr} (@command{gcc})
4072 Treat pragma Restrictions as Restriction_Warnings.
4074 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4075 @cindex @option{-gnatR} (@command{gcc})
4076 Output representation information for declared types and objects.
4079 @cindex @option{-gnats} (@command{gcc})
4083 @cindex @option{-gnatS} (@command{gcc})
4084 Print package Standard.
4087 @cindex @option{-gnatt} (@command{gcc})
4088 Generate tree output file.
4090 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4091 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4092 All compiler tables start at @var{nnn} times usual starting size.
4095 @cindex @option{-gnatu} (@command{gcc})
4096 List units for this compilation.
4099 @cindex @option{-gnatU} (@command{gcc})
4100 Tag all error messages with the unique string ``error:''
4103 @cindex @option{-gnatv} (@command{gcc})
4104 Verbose mode. Full error output with source lines to @file{stdout}.
4107 @cindex @option{-gnatV} (@command{gcc})
4108 Control level of validity checking. See separate section describing
4111 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4112 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4114 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4115 the exact warnings that
4116 are enabled or disabled (@pxref{Warning Message Control}).
4118 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4119 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4120 Wide character encoding method
4122 (@var{e}=n/h/u/s/e/8).
4125 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4129 @cindex @option{-gnatx} (@command{gcc})
4130 Suppress generation of cross-reference information.
4132 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4133 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4134 Enable built-in style checks (@pxref{Style Checking}).
4136 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4137 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4138 Distribution stub generation and compilation
4140 (@var{m}=r/c for receiver/caller stubs).
4143 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4144 to be generated and compiled).
4147 @item ^-I^/SEARCH=^@var{dir}
4148 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4150 Direct GNAT to search the @var{dir} directory for source files needed by
4151 the current compilation
4152 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4154 @item ^-I-^/NOCURRENT_DIRECTORY^
4155 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4157 Except for the source file named in the command line, do not look for source
4158 files in the directory containing the source file named in the command line
4159 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4163 @cindex @option{-mbig-switch} (@command{gcc})
4164 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4165 This standard gcc switch causes the compiler to use larger offsets in its
4166 jump table representation for @code{case} statements.
4167 This may result in less efficient code, but is sometimes necessary
4168 (for example on HP-UX targets)
4169 @cindex HP-UX and @option{-mbig-switch} option
4170 in order to compile large and/or nested @code{case} statements.
4173 @cindex @option{-o} (@command{gcc})
4174 This switch is used in @command{gcc} to redirect the generated object file
4175 and its associated ALI file. Beware of this switch with GNAT, because it may
4176 cause the object file and ALI file to have different names which in turn
4177 may confuse the binder and the linker.
4181 @cindex @option{-nostdinc} (@command{gcc})
4182 Inhibit the search of the default location for the GNAT Run Time
4183 Library (RTL) source files.
4186 @cindex @option{-nostdlib} (@command{gcc})
4187 Inhibit the search of the default location for the GNAT Run Time
4188 Library (RTL) ALI files.
4192 @cindex @option{-O} (@command{gcc})
4193 @var{n} controls the optimization level.
4197 No optimization, the default setting if no @option{-O} appears
4200 Normal optimization, the default if you specify @option{-O} without
4201 an operand. A good compromise between code quality and compilation
4205 Extensive optimization, may improve execution time, possibly at the cost of
4206 substantially increased compilation time.
4209 Same as @option{-O2}, and also includes inline expansion for small subprograms
4213 Optimize space usage
4217 See also @ref{Optimization Levels}.
4222 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4223 Equivalent to @option{/OPTIMIZE=NONE}.
4224 This is the default behavior in the absence of an @option{/OPTIMIZE}
4227 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4228 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4229 Selects the level of optimization for your program. The supported
4230 keywords are as follows:
4233 Perform most optimizations, including those that
4235 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4236 without keyword options.
4239 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4242 Perform some optimizations, but omit ones that are costly.
4245 Same as @code{SOME}.
4248 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4249 automatic inlining of small subprograms within a unit
4252 Try to unroll loops. This keyword may be specified together with
4253 any keyword above other than @code{NONE}. Loop unrolling
4254 usually, but not always, improves the performance of programs.
4257 Optimize space usage
4261 See also @ref{Optimization Levels}.
4265 @item -pass-exit-codes
4266 @cindex @option{-pass-exit-codes} (@command{gcc})
4267 Catch exit codes from the compiler and use the most meaningful as
4271 @item --RTS=@var{rts-path}
4272 @cindex @option{--RTS} (@command{gcc})
4273 Specifies the default location of the runtime library. Same meaning as the
4274 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4277 @cindex @option{^-S^/ASM^} (@command{gcc})
4278 ^Used in place of @option{-c} to^Used to^
4279 cause the assembler source file to be
4280 generated, using @file{^.s^.S^} as the extension,
4281 instead of the object file.
4282 This may be useful if you need to examine the generated assembly code.
4284 @item ^-fverbose-asm^/VERBOSE_ASM^
4285 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4286 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4287 to cause the generated assembly code file to be annotated with variable
4288 names, making it significantly easier to follow.
4291 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4292 Show commands generated by the @command{gcc} driver. Normally used only for
4293 debugging purposes or if you need to be sure what version of the
4294 compiler you are executing.
4298 @cindex @option{-V} (@command{gcc})
4299 Execute @var{ver} version of the compiler. This is the @command{gcc}
4300 version, not the GNAT version.
4303 @item ^-w^/NO_BACK_END_WARNINGS^
4304 @cindex @option{-w} (@command{gcc})
4305 Turn off warnings generated by the back end of the compiler. Use of
4306 this switch also causes the default for front end warnings to be set
4307 to suppress (as though @option{-gnatws} had appeared at the start of
4313 @c Combining qualifiers does not work on VMS
4314 You may combine a sequence of GNAT switches into a single switch. For
4315 example, the combined switch
4317 @cindex Combining GNAT switches
4323 is equivalent to specifying the following sequence of switches:
4326 -gnato -gnatf -gnati3
4331 The following restrictions apply to the combination of switches
4336 The switch @option{-gnatc} if combined with other switches must come
4337 first in the string.
4340 The switch @option{-gnats} if combined with other switches must come
4341 first in the string.
4345 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4346 may not be combined with any other switches.
4350 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4351 switch), then all further characters in the switch are interpreted
4352 as style modifiers (see description of @option{-gnaty}).
4355 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4356 switch), then all further characters in the switch are interpreted
4357 as debug flags (see description of @option{-gnatd}).
4360 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4361 switch), then all further characters in the switch are interpreted
4362 as warning mode modifiers (see description of @option{-gnatw}).
4365 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4366 switch), then all further characters in the switch are interpreted
4367 as validity checking options (see description of @option{-gnatV}).
4371 @node Output and Error Message Control
4372 @subsection Output and Error Message Control
4376 The standard default format for error messages is called ``brief format''.
4377 Brief format messages are written to @file{stderr} (the standard error
4378 file) and have the following form:
4381 e.adb:3:04: Incorrect spelling of keyword "function"
4382 e.adb:4:20: ";" should be "is"
4386 The first integer after the file name is the line number in the file,
4387 and the second integer is the column number within the line.
4389 @code{GPS} can parse the error messages
4390 and point to the referenced character.
4392 The following switches provide control over the error message
4398 @cindex @option{-gnatv} (@command{gcc})
4401 The v stands for verbose.
4403 The effect of this setting is to write long-format error
4404 messages to @file{stdout} (the standard output file.
4405 The same program compiled with the
4406 @option{-gnatv} switch would generate:
4410 3. funcion X (Q : Integer)
4412 >>> Incorrect spelling of keyword "function"
4415 >>> ";" should be "is"
4420 The vertical bar indicates the location of the error, and the @samp{>>>}
4421 prefix can be used to search for error messages. When this switch is
4422 used the only source lines output are those with errors.
4425 @cindex @option{-gnatl} (@command{gcc})
4427 The @code{l} stands for list.
4429 This switch causes a full listing of
4430 the file to be generated. In the case where a body is
4431 compiled, the corresponding spec is also listed, along
4432 with any subunits. Typical output from compiling a package
4433 body @file{p.adb} might look like:
4435 @smallexample @c ada
4439 1. package body p is
4441 3. procedure a is separate;
4452 2. pragma Elaborate_Body
4476 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4477 standard output is redirected, a brief summary is written to
4478 @file{stderr} (standard error) giving the number of error messages and
4479 warning messages generated.
4481 @item -^gnatl^OUTPUT_FILE^=file
4482 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4483 This has the same effect as @option{-gnatl} except that the output is
4484 written to a file instead of to standard output. If the given name
4485 @file{fname} does not start with a period, then it is the full name
4486 of the file to be written. If @file{fname} is an extension, it is
4487 appended to the name of the file being compiled. For example, if
4488 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4489 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4492 @cindex @option{-gnatU} (@command{gcc})
4493 This switch forces all error messages to be preceded by the unique
4494 string ``error:''. This means that error messages take a few more
4495 characters in space, but allows easy searching for and identification
4499 @cindex @option{-gnatb} (@command{gcc})
4501 The @code{b} stands for brief.
4503 This switch causes GNAT to generate the
4504 brief format error messages to @file{stderr} (the standard error
4505 file) as well as the verbose
4506 format message or full listing (which as usual is written to
4507 @file{stdout} (the standard output file).
4509 @item -gnatm=@var{n}
4510 @cindex @option{-gnatm} (@command{gcc})
4512 The @code{m} stands for maximum.
4514 @var{n} is a decimal integer in the
4515 range of 1 to 999999 and limits the number of error or warning
4516 messages to be generated. For example, using
4517 @option{-gnatm2} might yield
4520 e.adb:3:04: Incorrect spelling of keyword "function"
4521 e.adb:5:35: missing ".."
4522 fatal error: maximum number of errors detected
4523 compilation abandoned
4527 The default setting if
4528 no switch is given is 9999. If the number of warnings reaches this
4529 limit, then a message is output and further warnings are suppressed,
4530 but the compilation is continued. If the number of error messages
4531 reaches this limit, then a message is output and the compilation
4532 is abandoned. A value of zero means that no limit applies.
4535 Note that the equal sign is optional, so the switches
4536 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4539 @cindex @option{-gnatf} (@command{gcc})
4540 @cindex Error messages, suppressing
4542 The @code{f} stands for full.
4544 Normally, the compiler suppresses error messages that are likely to be
4545 redundant. This switch causes all error
4546 messages to be generated. In particular, in the case of
4547 references to undefined variables. If a given variable is referenced
4548 several times, the normal format of messages is
4550 e.adb:7:07: "V" is undefined (more references follow)
4554 where the parenthetical comment warns that there are additional
4555 references to the variable @code{V}. Compiling the same program with the
4556 @option{-gnatf} switch yields
4559 e.adb:7:07: "V" is undefined
4560 e.adb:8:07: "V" is undefined
4561 e.adb:8:12: "V" is undefined
4562 e.adb:8:16: "V" is undefined
4563 e.adb:9:07: "V" is undefined
4564 e.adb:9:12: "V" is undefined
4568 The @option{-gnatf} switch also generates additional information for
4569 some error messages. Some examples are:
4573 Full details on entities not available in high integrity mode
4575 Details on possibly non-portable unchecked conversion
4577 List possible interpretations for ambiguous calls
4579 Additional details on incorrect parameters
4583 @cindex @option{-gnatjnn} (@command{gcc})
4584 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4585 with continuation lines are treated as though the continuation lines were
4586 separate messages (and so a warning with two continuation lines counts as
4587 three warnings, and is listed as three separate messages).
4589 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4590 messages are output in a different manner. A message and all its continuation
4591 lines are treated as a unit, and count as only one warning or message in the
4592 statistics totals. Furthermore, the message is reformatted so that no line
4593 is longer than nn characters.
4596 @cindex @option{-gnatq} (@command{gcc})
4598 The @code{q} stands for quit (really ``don't quit'').
4600 In normal operation mode, the compiler first parses the program and
4601 determines if there are any syntax errors. If there are, appropriate
4602 error messages are generated and compilation is immediately terminated.
4604 GNAT to continue with semantic analysis even if syntax errors have been
4605 found. This may enable the detection of more errors in a single run. On
4606 the other hand, the semantic analyzer is more likely to encounter some
4607 internal fatal error when given a syntactically invalid tree.
4610 @cindex @option{-gnatQ} (@command{gcc})
4611 In normal operation mode, the @file{ALI} file is not generated if any
4612 illegalities are detected in the program. The use of @option{-gnatQ} forces
4613 generation of the @file{ALI} file. This file is marked as being in
4614 error, so it cannot be used for binding purposes, but it does contain
4615 reasonably complete cross-reference information, and thus may be useful
4616 for use by tools (e.g., semantic browsing tools or integrated development
4617 environments) that are driven from the @file{ALI} file. This switch
4618 implies @option{-gnatq}, since the semantic phase must be run to get a
4619 meaningful ALI file.
4621 In addition, if @option{-gnatt} is also specified, then the tree file is
4622 generated even if there are illegalities. It may be useful in this case
4623 to also specify @option{-gnatq} to ensure that full semantic processing
4624 occurs. The resulting tree file can be processed by ASIS, for the purpose
4625 of providing partial information about illegal units, but if the error
4626 causes the tree to be badly malformed, then ASIS may crash during the
4629 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4630 being in error, @command{gnatmake} will attempt to recompile the source when it
4631 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4633 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4634 since ALI files are never generated if @option{-gnats} is set.
4638 @node Warning Message Control
4639 @subsection Warning Message Control
4640 @cindex Warning messages
4642 In addition to error messages, which correspond to illegalities as defined
4643 in the Ada Reference Manual, the compiler detects two kinds of warning
4646 First, the compiler considers some constructs suspicious and generates a
4647 warning message to alert you to a possible error. Second, if the
4648 compiler detects a situation that is sure to raise an exception at
4649 run time, it generates a warning message. The following shows an example
4650 of warning messages:
4652 e.adb:4:24: warning: creation of object may raise Storage_Error
4653 e.adb:10:17: warning: static value out of range
4654 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4658 GNAT considers a large number of situations as appropriate
4659 for the generation of warning messages. As always, warnings are not
4660 definite indications of errors. For example, if you do an out-of-range
4661 assignment with the deliberate intention of raising a
4662 @code{Constraint_Error} exception, then the warning that may be
4663 issued does not indicate an error. Some of the situations for which GNAT
4664 issues warnings (at least some of the time) are given in the following
4665 list. This list is not complete, and new warnings are often added to
4666 subsequent versions of GNAT. The list is intended to give a general idea
4667 of the kinds of warnings that are generated.
4671 Possible infinitely recursive calls
4674 Out-of-range values being assigned
4677 Possible order of elaboration problems
4680 Assertions (pragma Assert) that are sure to fail
4686 Address clauses with possibly unaligned values, or where an attempt is
4687 made to overlay a smaller variable with a larger one.
4690 Fixed-point type declarations with a null range
4693 Direct_IO or Sequential_IO instantiated with a type that has access values
4696 Variables that are never assigned a value
4699 Variables that are referenced before being initialized
4702 Task entries with no corresponding @code{accept} statement
4705 Duplicate accepts for the same task entry in a @code{select}
4708 Objects that take too much storage
4711 Unchecked conversion between types of differing sizes
4714 Missing @code{return} statement along some execution path in a function
4717 Incorrect (unrecognized) pragmas
4720 Incorrect external names
4723 Allocation from empty storage pool
4726 Potentially blocking operation in protected type
4729 Suspicious parenthesization of expressions
4732 Mismatching bounds in an aggregate
4735 Attempt to return local value by reference
4738 Premature instantiation of a generic body
4741 Attempt to pack aliased components
4744 Out of bounds array subscripts
4747 Wrong length on string assignment
4750 Violations of style rules if style checking is enabled
4753 Unused @code{with} clauses
4756 @code{Bit_Order} usage that does not have any effect
4759 @code{Standard.Duration} used to resolve universal fixed expression
4762 Dereference of possibly null value
4765 Declaration that is likely to cause storage error
4768 Internal GNAT unit @code{with}'ed by application unit
4771 Values known to be out of range at compile time
4774 Unreferenced labels and variables
4777 Address overlays that could clobber memory
4780 Unexpected initialization when address clause present
4783 Bad alignment for address clause
4786 Useless type conversions
4789 Redundant assignment statements and other redundant constructs
4792 Useless exception handlers
4795 Accidental hiding of name by child unit
4798 Access before elaboration detected at compile time
4801 A range in a @code{for} loop that is known to be null or might be null
4806 The following section lists compiler switches that are available
4807 to control the handling of warning messages. It is also possible
4808 to exercise much finer control over what warnings are issued and
4809 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
4810 gnat_rm, GNAT Reference manual}.
4815 @emph{Activate all optional errors.}
4816 @cindex @option{-gnatwa} (@command{gcc})
4817 This switch activates most optional warning messages, see remaining list
4818 in this section for details on optional warning messages that can be
4819 individually controlled. The warnings that are not turned on by this
4821 @option{-gnatwd} (implicit dereferencing),
4822 @option{-gnatwh} (hiding),
4823 @option{-gnatwl} (elaboration warnings),
4824 @option{-gnatw.o} (warn on values set by out parameters ignored)
4825 and @option{-gnatwt} (tracking of deleted conditional code).
4826 All other optional warnings are turned on.
4829 @emph{Suppress all optional errors.}
4830 @cindex @option{-gnatwA} (@command{gcc})
4831 This switch suppresses all optional warning messages, see remaining list
4832 in this section for details on optional warning messages that can be
4833 individually controlled.
4836 @emph{Activate warnings on failing assertions.}
4837 @cindex @option{-gnatw.a} (@command{gcc})
4838 @cindex Assert failures
4839 This switch activates warnings for assertions where the compiler can tell at
4840 compile time that the assertion will fail. Note that this warning is given
4841 even if assertions are disabled. The default is that such warnings are
4845 @emph{Suppress warnings on failing assertions.}
4846 @cindex @option{-gnatw.A} (@command{gcc})
4847 @cindex Assert failures
4848 This switch suppresses warnings for assertions where the compiler can tell at
4849 compile time that the assertion will fail.
4852 @emph{Activate warnings on bad fixed values.}
4853 @cindex @option{-gnatwb} (@command{gcc})
4854 @cindex Bad fixed values
4855 @cindex Fixed-point Small value
4857 This switch activates warnings for static fixed-point expressions whose
4858 value is not an exact multiple of Small. Such values are implementation
4859 dependent, since an implementation is free to choose either of the multiples
4860 that surround the value. GNAT always chooses the closer one, but this is not
4861 required behavior, and it is better to specify a value that is an exact
4862 multiple, ensuring predictable execution. The default is that such warnings
4866 @emph{Suppress warnings on bad fixed values.}
4867 @cindex @option{-gnatwB} (@command{gcc})
4868 This switch suppresses warnings for static fixed-point expressions whose
4869 value is not an exact multiple of Small.
4872 @emph{Activate warnings on biased representation.}
4873 @cindex @option{-gnatw.b} (@command{gcc})
4874 @cindex Biased representation
4875 This switch activates warnings when a size clause, value size clause, component
4876 clause, or component size clause forces the use of biased representation for an
4877 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
4878 to represent 10/11). The default is that such warnings are generated.
4881 @emph{Suppress warnings on biased representation.}
4882 @cindex @option{-gnatwB} (@command{gcc})
4883 This switch suppresses warnings for representation clauses that force the use
4884 of biased representation.
4887 @emph{Activate warnings on conditionals.}
4888 @cindex @option{-gnatwc} (@command{gcc})
4889 @cindex Conditionals, constant
4890 This switch activates warnings for conditional expressions used in
4891 tests that are known to be True or False at compile time. The default
4892 is that such warnings are not generated.
4893 Note that this warning does
4894 not get issued for the use of boolean variables or constants whose
4895 values are known at compile time, since this is a standard technique
4896 for conditional compilation in Ada, and this would generate too many
4897 false positive warnings.
4899 This warning option also activates a special test for comparisons using
4900 the operators ``>='' and`` <=''.
4901 If the compiler can tell that only the equality condition is possible,
4902 then it will warn that the ``>'' or ``<'' part of the test
4903 is useless and that the operator could be replaced by ``=''.
4904 An example would be comparing a @code{Natural} variable <= 0.
4906 This warning option also generates warnings if
4907 one or both tests is optimized away in a membership test for integer
4908 values if the result can be determined at compile time. Range tests on
4909 enumeration types are not included, since it is common for such tests
4910 to include an end point.
4912 This warning can also be turned on using @option{-gnatwa}.
4915 @emph{Suppress warnings on conditionals.}
4916 @cindex @option{-gnatwC} (@command{gcc})
4917 This switch suppresses warnings for conditional expressions used in
4918 tests that are known to be True or False at compile time.
4921 @emph{Activate warnings on missing component clauses.}
4922 @cindex @option{-gnatw.c} (@command{gcc})
4923 @cindex Component clause, missing
4924 This switch activates warnings for record components where a record
4925 representation clause is present and has component clauses for the
4926 majority, but not all, of the components. A warning is given for each
4927 component for which no component clause is present.
4929 This warning can also be turned on using @option{-gnatwa}.
4932 @emph{Suppress warnings on missing component clauses.}
4933 @cindex @option{-gnatwC} (@command{gcc})
4934 This switch suppresses warnings for record components that are
4935 missing a component clause in the situation described above.
4938 @emph{Activate warnings on implicit dereferencing.}
4939 @cindex @option{-gnatwd} (@command{gcc})
4940 If this switch is set, then the use of a prefix of an access type
4941 in an indexed component, slice, or selected component without an
4942 explicit @code{.all} will generate a warning. With this warning
4943 enabled, access checks occur only at points where an explicit
4944 @code{.all} appears in the source code (assuming no warnings are
4945 generated as a result of this switch). The default is that such
4946 warnings are not generated.
4947 Note that @option{-gnatwa} does not affect the setting of
4948 this warning option.
4951 @emph{Suppress warnings on implicit dereferencing.}
4952 @cindex @option{-gnatwD} (@command{gcc})
4953 @cindex Implicit dereferencing
4954 @cindex Dereferencing, implicit
4955 This switch suppresses warnings for implicit dereferences in
4956 indexed components, slices, and selected components.
4959 @emph{Treat warnings as errors.}
4960 @cindex @option{-gnatwe} (@command{gcc})
4961 @cindex Warnings, treat as error
4962 This switch causes warning messages to be treated as errors.
4963 The warning string still appears, but the warning messages are counted
4964 as errors, and prevent the generation of an object file.
4967 @emph{Activate every optional warning}
4968 @cindex @option{-gnatw.e} (@command{gcc})
4969 @cindex Warnings, activate every optional warning
4970 This switch activates all optional warnings, including those which
4971 are not activated by @code{-gnatwa}.
4974 @emph{Activate warnings on unreferenced formals.}
4975 @cindex @option{-gnatwf} (@command{gcc})
4976 @cindex Formals, unreferenced
4977 This switch causes a warning to be generated if a formal parameter
4978 is not referenced in the body of the subprogram. This warning can
4979 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
4980 default is that these warnings are not generated.
4983 @emph{Suppress warnings on unreferenced formals.}
4984 @cindex @option{-gnatwF} (@command{gcc})
4985 This switch suppresses warnings for unreferenced formal
4986 parameters. Note that the
4987 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4988 effect of warning on unreferenced entities other than subprogram
4992 @emph{Activate warnings on unrecognized pragmas.}
4993 @cindex @option{-gnatwg} (@command{gcc})
4994 @cindex Pragmas, unrecognized
4995 This switch causes a warning to be generated if an unrecognized
4996 pragma is encountered. Apart from issuing this warning, the
4997 pragma is ignored and has no effect. This warning can
4998 also be turned on using @option{-gnatwa}. The default
4999 is that such warnings are issued (satisfying the Ada Reference
5000 Manual requirement that such warnings appear).
5003 @emph{Suppress warnings on unrecognized pragmas.}
5004 @cindex @option{-gnatwG} (@command{gcc})
5005 This switch suppresses warnings for unrecognized pragmas.
5008 @emph{Activate warnings on hiding.}
5009 @cindex @option{-gnatwh} (@command{gcc})
5010 @cindex Hiding of Declarations
5011 This switch activates warnings on hiding declarations.
5012 A declaration is considered hiding
5013 if it is for a non-overloadable entity, and it declares an entity with the
5014 same name as some other entity that is directly or use-visible. The default
5015 is that such warnings are not generated.
5016 Note that @option{-gnatwa} does not affect the setting of this warning option.
5019 @emph{Suppress warnings on hiding.}
5020 @cindex @option{-gnatwH} (@command{gcc})
5021 This switch suppresses warnings on hiding declarations.
5024 @emph{Activate warnings on implementation units.}
5025 @cindex @option{-gnatwi} (@command{gcc})
5026 This switch activates warnings for a @code{with} of an internal GNAT
5027 implementation unit, defined as any unit from the @code{Ada},
5028 @code{Interfaces}, @code{GNAT},
5029 ^^@code{DEC},^ or @code{System}
5030 hierarchies that is not
5031 documented in either the Ada Reference Manual or the GNAT
5032 Programmer's Reference Manual. Such units are intended only
5033 for internal implementation purposes and should not be @code{with}'ed
5034 by user programs. The default is that such warnings are generated
5035 This warning can also be turned on using @option{-gnatwa}.
5038 @emph{Disable warnings on implementation units.}
5039 @cindex @option{-gnatwI} (@command{gcc})
5040 This switch disables warnings for a @code{with} of an internal GNAT
5041 implementation unit.
5044 @emph{Activate warnings on obsolescent features (Annex J).}
5045 @cindex @option{-gnatwj} (@command{gcc})
5046 @cindex Features, obsolescent
5047 @cindex Obsolescent features
5048 If this warning option is activated, then warnings are generated for
5049 calls to subprograms marked with @code{pragma Obsolescent} and
5050 for use of features in Annex J of the Ada Reference Manual. In the
5051 case of Annex J, not all features are flagged. In particular use
5052 of the renamed packages (like @code{Text_IO}) and use of package
5053 @code{ASCII} are not flagged, since these are very common and
5054 would generate many annoying positive warnings. The default is that
5055 such warnings are not generated. This warning is also turned on by
5056 the use of @option{-gnatwa}.
5058 In addition to the above cases, warnings are also generated for
5059 GNAT features that have been provided in past versions but which
5060 have been superseded (typically by features in the new Ada standard).
5061 For example, @code{pragma Ravenscar} will be flagged since its
5062 function is replaced by @code{pragma Profile(Ravenscar)}.
5064 Note that this warning option functions differently from the
5065 restriction @code{No_Obsolescent_Features} in two respects.
5066 First, the restriction applies only to annex J features.
5067 Second, the restriction does flag uses of package @code{ASCII}.
5070 @emph{Suppress warnings on obsolescent features (Annex J).}
5071 @cindex @option{-gnatwJ} (@command{gcc})
5072 This switch disables warnings on use of obsolescent features.
5075 @emph{Activate warnings on variables that could be constants.}
5076 @cindex @option{-gnatwk} (@command{gcc})
5077 This switch activates warnings for variables that are initialized but
5078 never modified, and then could be declared constants. The default is that
5079 such warnings are not given.
5080 This warning can also be turned on using @option{-gnatwa}.
5083 @emph{Suppress warnings on variables that could be constants.}
5084 @cindex @option{-gnatwK} (@command{gcc})
5085 This switch disables warnings on variables that could be declared constants.
5088 @emph{Activate warnings for elaboration pragmas.}
5089 @cindex @option{-gnatwl} (@command{gcc})
5090 @cindex Elaboration, warnings
5091 This switch activates warnings on missing
5092 @code{Elaborate_All} and @code{Elaborate} pragmas.
5093 See the section in this guide on elaboration checking for details on
5094 when such pragmas should be used. In dynamic elaboration mode, this switch
5095 generations warnings about the need to add elaboration pragmas. Note however,
5096 that if you blindly follow these warnings, and add @code{Elaborate_All}
5097 warnings wherever they are recommended, you basically end up with the
5098 equivalent of the static elaboration model, which may not be what you want for
5099 legacy code for which the static model does not work.
5101 For the static model, the messages generated are labeled "info:" (for
5102 information messages). They are not warnings to add elaboration pragmas,
5103 merely informational messages showing what implicit elaboration pragmas
5104 have been added, for use in analyzing elaboration circularity problems.
5106 Warnings are also generated if you
5107 are using the static mode of elaboration, and a @code{pragma Elaborate}
5108 is encountered. The default is that such warnings
5110 This warning is not automatically turned on by the use of @option{-gnatwa}.
5113 @emph{Suppress warnings for elaboration pragmas.}
5114 @cindex @option{-gnatwL} (@command{gcc})
5115 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5116 See the section in this guide on elaboration checking for details on
5117 when such pragmas should be used.
5120 @emph{Activate warnings on modified but unreferenced variables.}
5121 @cindex @option{-gnatwm} (@command{gcc})
5122 This switch activates warnings for variables that are assigned (using
5123 an initialization value or with one or more assignment statements) but
5124 whose value is never read. The warning is suppressed for volatile
5125 variables and also for variables that are renamings of other variables
5126 or for which an address clause is given.
5127 This warning can also be turned on using @option{-gnatwa}.
5128 The default is that these warnings are not given.
5131 @emph{Disable warnings on modified but unreferenced variables.}
5132 @cindex @option{-gnatwM} (@command{gcc})
5133 This switch disables warnings for variables that are assigned or
5134 initialized, but never read.
5137 @emph{Set normal warnings mode.}
5138 @cindex @option{-gnatwn} (@command{gcc})
5139 This switch sets normal warning mode, in which enabled warnings are
5140 issued and treated as warnings rather than errors. This is the default
5141 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5142 an explicit @option{-gnatws} or
5143 @option{-gnatwe}. It also cancels the effect of the
5144 implicit @option{-gnatwe} that is activated by the
5145 use of @option{-gnatg}.
5148 @emph{Activate warnings on address clause overlays.}
5149 @cindex @option{-gnatwo} (@command{gcc})
5150 @cindex Address Clauses, warnings
5151 This switch activates warnings for possibly unintended initialization
5152 effects of defining address clauses that cause one variable to overlap
5153 another. The default is that such warnings are generated.
5154 This warning can also be turned on using @option{-gnatwa}.
5157 @emph{Suppress warnings on address clause overlays.}
5158 @cindex @option{-gnatwO} (@command{gcc})
5159 This switch suppresses warnings on possibly unintended initialization
5160 effects of defining address clauses that cause one variable to overlap
5164 @emph{Activate warnings on modified but unreferenced out parameters.}
5165 @cindex @option{-gnatw.o} (@command{gcc})
5166 This switch activates warnings for variables that are modified by using
5167 them as actuals for a call to a procedure with an out mode formal, where
5168 the resulting assigned value is never read. It is applicable in the case
5169 where there is more than one out mode formal. If there is only one out
5170 mode formal, the warning is issued by default (controlled by -gnatwu).
5171 The warning is suppressed for volatile
5172 variables and also for variables that are renamings of other variables
5173 or for which an address clause is given.
5174 The default is that these warnings are not given. Note that this warning
5175 is not included in -gnatwa, it must be activated explicitly.
5178 @emph{Disable warnings on modified but unreferenced out parameters.}
5179 @cindex @option{-gnatw.O} (@command{gcc})
5180 This switch suppresses warnings for variables that are modified by using
5181 them as actuals for a call to a procedure with an out mode formal, where
5182 the resulting assigned value is never read.
5185 @emph{Activate warnings on ineffective pragma Inlines.}
5186 @cindex @option{-gnatwp} (@command{gcc})
5187 @cindex Inlining, warnings
5188 This switch activates warnings for failure of front end inlining
5189 (activated by @option{-gnatN}) to inline a particular call. There are
5190 many reasons for not being able to inline a call, including most
5191 commonly that the call is too complex to inline. The default is
5192 that such warnings are not given.
5193 This warning can also be turned on using @option{-gnatwa}.
5194 Warnings on ineffective inlining by the gcc back-end can be activated
5195 separately, using the gcc switch -Winline.
5198 @emph{Suppress warnings on ineffective pragma Inlines.}
5199 @cindex @option{-gnatwP} (@command{gcc})
5200 This switch suppresses warnings on ineffective pragma Inlines. If the
5201 inlining mechanism cannot inline a call, it will simply ignore the
5205 @emph{Activate warnings on parameter ordering.}
5206 @cindex @option{-gnatw.p} (@command{gcc})
5207 @cindex Parameter order, warnings
5208 This switch activates warnings for cases of suspicious parameter
5209 ordering when the list of arguments are all simple identifiers that
5210 match the names of the formals, but are in a different order. The
5211 warning is suppressed if any use of named parameter notation is used,
5212 so this is the appropriate way to suppress a false positive (and
5213 serves to emphasize that the "misordering" is deliberate). The
5215 that such warnings are not given.
5216 This warning can also be turned on using @option{-gnatwa}.
5219 @emph{Suppress warnings on parameter ordering.}
5220 @cindex @option{-gnatw.P} (@command{gcc})
5221 This switch suppresses warnings on cases of suspicious parameter
5225 @emph{Activate warnings on questionable missing parentheses.}
5226 @cindex @option{-gnatwq} (@command{gcc})
5227 @cindex Parentheses, warnings
5228 This switch activates warnings for cases where parentheses are not used and
5229 the result is potential ambiguity from a readers point of view. For example
5230 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5231 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5232 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5233 follow the rule of always parenthesizing to make the association clear, and
5234 this warning switch warns if such parentheses are not present. The default
5235 is that these warnings are given.
5236 This warning can also be turned on using @option{-gnatwa}.
5239 @emph{Suppress warnings on questionable missing parentheses.}
5240 @cindex @option{-gnatwQ} (@command{gcc})
5241 This switch suppresses warnings for cases where the association is not
5242 clear and the use of parentheses is preferred.
5245 @emph{Activate warnings on redundant constructs.}
5246 @cindex @option{-gnatwr} (@command{gcc})
5247 This switch activates warnings for redundant constructs. The following
5248 is the current list of constructs regarded as redundant:
5252 Assignment of an item to itself.
5254 Type conversion that converts an expression to its own type.
5256 Use of the attribute @code{Base} where @code{typ'Base} is the same
5259 Use of pragma @code{Pack} when all components are placed by a record
5260 representation clause.
5262 Exception handler containing only a reraise statement (raise with no
5263 operand) which has no effect.
5265 Use of the operator abs on an operand that is known at compile time
5268 Comparison of boolean expressions to an explicit True value.
5271 This warning can also be turned on using @option{-gnatwa}.
5272 The default is that warnings for redundant constructs are not given.
5275 @emph{Suppress warnings on redundant constructs.}
5276 @cindex @option{-gnatwR} (@command{gcc})
5277 This switch suppresses warnings for redundant constructs.
5280 @emph{Suppress all warnings.}
5281 @cindex @option{-gnatws} (@command{gcc})
5282 This switch completely suppresses the
5283 output of all warning messages from the GNAT front end.
5284 Note that it does not suppress warnings from the @command{gcc} back end.
5285 To suppress these back end warnings as well, use the switch @option{-w}
5286 in addition to @option{-gnatws}.
5289 @emph{Activate warnings for tracking of deleted conditional code.}
5290 @cindex @option{-gnatwt} (@command{gcc})
5291 @cindex Deactivated code, warnings
5292 @cindex Deleted code, warnings
5293 This switch activates warnings for tracking of code in conditionals (IF and
5294 CASE statements) that is detected to be dead code which cannot be executed, and
5295 which is removed by the front end. This warning is off by default, and is not
5296 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5297 useful for detecting deactivated code in certified applications.
5300 @emph{Suppress warnings for tracking of deleted conditional code.}
5301 @cindex @option{-gnatwT} (@command{gcc})
5302 This switch suppresses warnings for tracking of deleted conditional code.
5305 @emph{Activate warnings on unused entities.}
5306 @cindex @option{-gnatwu} (@command{gcc})
5307 This switch activates warnings to be generated for entities that
5308 are declared but not referenced, and for units that are @code{with}'ed
5310 referenced. In the case of packages, a warning is also generated if
5311 no entities in the package are referenced. This means that if the package
5312 is referenced but the only references are in @code{use}
5313 clauses or @code{renames}
5314 declarations, a warning is still generated. A warning is also generated
5315 for a generic package that is @code{with}'ed but never instantiated.
5316 In the case where a package or subprogram body is compiled, and there
5317 is a @code{with} on the corresponding spec
5318 that is only referenced in the body,
5319 a warning is also generated, noting that the
5320 @code{with} can be moved to the body. The default is that
5321 such warnings are not generated.
5322 This switch also activates warnings on unreferenced formals
5323 (it includes the effect of @option{-gnatwf}).
5324 This warning can also be turned on using @option{-gnatwa}.
5327 @emph{Suppress warnings on unused entities.}
5328 @cindex @option{-gnatwU} (@command{gcc})
5329 This switch suppresses warnings for unused entities and packages.
5330 It also turns off warnings on unreferenced formals (and thus includes
5331 the effect of @option{-gnatwF}).
5334 @emph{Activate warnings on unassigned variables.}
5335 @cindex @option{-gnatwv} (@command{gcc})
5336 @cindex Unassigned variable warnings
5337 This switch activates warnings for access to variables which
5338 may not be properly initialized. The default is that
5339 such warnings are generated.
5340 This warning can also be turned on using @option{-gnatwa}.
5343 @emph{Suppress warnings on unassigned variables.}
5344 @cindex @option{-gnatwV} (@command{gcc})
5345 This switch suppresses warnings for access to variables which
5346 may not be properly initialized.
5347 For variables of a composite type, the warning can also be suppressed in
5348 Ada 2005 by using a default initialization with a box. For example, if
5349 Table is an array of records whose components are only partially uninitialized,
5350 then the following code:
5352 @smallexample @c ada
5353 Tab : Table := (others => <>);
5356 will suppress warnings on subsequent statements that access components
5360 @emph{Activate warnings on wrong low bound assumption.}
5361 @cindex @option{-gnatww} (@command{gcc})
5362 @cindex String indexing warnings
5363 This switch activates warnings for indexing an unconstrained string parameter
5364 with a literal or S'Length. This is a case where the code is assuming that the
5365 low bound is one, which is in general not true (for example when a slice is
5366 passed). The default is that such warnings are generated.
5367 This warning can also be turned on using @option{-gnatwa}.
5370 @emph{Suppress warnings on wrong low bound assumption.}
5371 @cindex @option{-gnatwW} (@command{gcc})
5372 This switch suppresses warnings for indexing an unconstrained string parameter
5373 with a literal or S'Length. Note that this warning can also be suppressed
5374 in a particular case by adding an
5375 assertion that the lower bound is 1,
5376 as shown in the following example.
5378 @smallexample @c ada
5379 procedure K (S : String) is
5380 pragma Assert (S'First = 1);
5385 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5386 @cindex @option{-gnatw.w} (@command{gcc})
5387 @cindex Warnings Off control
5388 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5389 where either the pragma is entirely useless (because it suppresses no
5390 warnings), or it could be replaced by @code{pragma Unreferenced} or
5391 @code{pragma Unmodified}.The default is that these warnings are not given.
5392 Note that this warning is not included in -gnatwa, it must be
5393 activated explicitly.
5396 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5397 @cindex @option{-gnatw.W} (@command{gcc})
5398 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5401 @emph{Activate warnings on Export/Import pragmas.}
5402 @cindex @option{-gnatwx} (@command{gcc})
5403 @cindex Export/Import pragma warnings
5404 This switch activates warnings on Export/Import pragmas when
5405 the compiler detects a possible conflict between the Ada and
5406 foreign language calling sequences. For example, the use of
5407 default parameters in a convention C procedure is dubious
5408 because the C compiler cannot supply the proper default, so
5409 a warning is issued. The default is that such warnings are
5411 This warning can also be turned on using @option{-gnatwa}.
5414 @emph{Suppress warnings on Export/Import pragmas.}
5415 @cindex @option{-gnatwX} (@command{gcc})
5416 This switch suppresses warnings on Export/Import pragmas.
5417 The sense of this is that you are telling the compiler that
5418 you know what you are doing in writing the pragma, and it
5419 should not complain at you.
5422 @emph{Activate warnings for No_Exception_Propagation mode.}
5423 @cindex @option{-gnatwm} (@command{gcc})
5424 This switch activates warnings for exception usage when pragma Restrictions
5425 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5426 explicit exception raises which are not covered by a local handler, and for
5427 exception handlers which do not cover a local raise. The default is that these
5428 warnings are not given.
5431 @emph{Disable warnings for No_Exception_Propagation mode.}
5432 This switch disables warnings for exception usage when pragma Restrictions
5433 (No_Exception_Propagation) is in effect.
5436 @emph{Activate warnings for Ada 2005 compatibility issues.}
5437 @cindex @option{-gnatwy} (@command{gcc})
5438 @cindex Ada 2005 compatibility issues warnings
5439 For the most part Ada 2005 is upwards compatible with Ada 95,
5440 but there are some exceptions (for example the fact that
5441 @code{interface} is now a reserved word in Ada 2005). This
5442 switch activates several warnings to help in identifying
5443 and correcting such incompatibilities. The default is that
5444 these warnings are generated. Note that at one point Ada 2005
5445 was called Ada 0Y, hence the choice of character.
5446 This warning can also be turned on using @option{-gnatwa}.
5449 @emph{Disable warnings for Ada 2005 compatibility issues.}
5450 @cindex @option{-gnatwY} (@command{gcc})
5451 @cindex Ada 2005 compatibility issues warnings
5452 This switch suppresses several warnings intended to help in identifying
5453 incompatibilities between Ada 95 and Ada 2005.
5456 @emph{Activate warnings on unchecked conversions.}
5457 @cindex @option{-gnatwz} (@command{gcc})
5458 @cindex Unchecked_Conversion warnings
5459 This switch activates warnings for unchecked conversions
5460 where the types are known at compile time to have different
5462 is that such warnings are generated. Warnings are also
5463 generated for subprogram pointers with different conventions,
5464 and, on VMS only, for data pointers with different conventions.
5465 This warning can also be turned on using @option{-gnatwa}.
5468 @emph{Suppress warnings on unchecked conversions.}
5469 @cindex @option{-gnatwZ} (@command{gcc})
5470 This switch suppresses warnings for unchecked conversions
5471 where the types are known at compile time to have different
5472 sizes or conventions.
5474 @item ^-Wunused^WARNINGS=UNUSED^
5475 @cindex @option{-Wunused}
5476 The warnings controlled by the @option{-gnatw} switch are generated by
5477 the front end of the compiler. The @option{GCC} back end can provide
5478 additional warnings and they are controlled by the @option{-W} switch.
5479 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5480 warnings for entities that are declared but not referenced.
5482 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5483 @cindex @option{-Wuninitialized}
5484 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5485 the back end warning for uninitialized variables. This switch must be
5486 used in conjunction with an optimization level greater than zero.
5488 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5489 @cindex @option{-Wall}
5490 This switch enables all the above warnings from the @option{GCC} back end.
5491 The code generator detects a number of warning situations that are missed
5492 by the @option{GNAT} front end, and this switch can be used to activate them.
5493 The use of this switch also sets the default front end warning mode to
5494 @option{-gnatwa}, that is, most front end warnings activated as well.
5496 @item ^-w^/NO_BACK_END_WARNINGS^
5498 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5499 The use of this switch also sets the default front end warning mode to
5500 @option{-gnatws}, that is, front end warnings suppressed as well.
5506 A string of warning parameters can be used in the same parameter. For example:
5513 will turn on all optional warnings except for elaboration pragma warnings,
5514 and also specify that warnings should be treated as errors.
5516 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5541 @node Debugging and Assertion Control
5542 @subsection Debugging and Assertion Control
5546 @cindex @option{-gnata} (@command{gcc})
5552 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5553 are ignored. This switch, where @samp{a} stands for assert, causes
5554 @code{Assert} and @code{Debug} pragmas to be activated.
5556 The pragmas have the form:
5560 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5561 @var{static-string-expression}@r{]})
5562 @b{pragma} Debug (@var{procedure call})
5567 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5568 If the result is @code{True}, the pragma has no effect (other than
5569 possible side effects from evaluating the expression). If the result is
5570 @code{False}, the exception @code{Assert_Failure} declared in the package
5571 @code{System.Assertions} is
5572 raised (passing @var{static-string-expression}, if present, as the
5573 message associated with the exception). If no string expression is
5574 given the default is a string giving the file name and line number
5577 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5578 @code{pragma Debug} may appear within a declaration sequence, allowing
5579 debugging procedures to be called between declarations.
5582 @item /DEBUG@r{[}=debug-level@r{]}
5584 Specifies how much debugging information is to be included in
5585 the resulting object file where 'debug-level' is one of the following:
5588 Include both debugger symbol records and traceback
5590 This is the default setting.
5592 Include both debugger symbol records and traceback in
5595 Excludes both debugger symbol records and traceback
5596 the object file. Same as /NODEBUG.
5598 Includes only debugger symbol records in the object
5599 file. Note that this doesn't include traceback information.
5604 @node Validity Checking
5605 @subsection Validity Checking
5606 @findex Validity Checking
5609 The Ada Reference Manual has specific requirements for checking
5610 for invalid values. In particular, RM 13.9.1 requires that the
5611 evaluation of invalid values (for example from unchecked conversions),
5612 not result in erroneous execution. In GNAT, the result of such an
5613 evaluation in normal default mode is to either use the value
5614 unmodified, or to raise Constraint_Error in those cases where use
5615 of the unmodified value would cause erroneous execution. The cases
5616 where unmodified values might lead to erroneous execution are case
5617 statements (where a wild jump might result from an invalid value),
5618 and subscripts on the left hand side (where memory corruption could
5619 occur as a result of an invalid value).
5621 The @option{-gnatB} switch tells the compiler to assume that all
5622 values are valid (that is, within their declared subtype range)
5623 except in the context of a use of the Valid attribute. This means
5624 the compiler can generate more efficient code, since the range
5625 of values is better known at compile time.
5627 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5630 The @code{x} argument is a string of letters that
5631 indicate validity checks that are performed or not performed in addition
5632 to the default checks described above.
5635 The options allowed for this qualifier
5636 indicate validity checks that are performed or not performed in addition
5637 to the default checks described above.
5643 @emph{All validity checks.}
5644 @cindex @option{-gnatVa} (@command{gcc})
5645 All validity checks are turned on.
5647 That is, @option{-gnatVa} is
5648 equivalent to @option{gnatVcdfimorst}.
5652 @emph{Validity checks for copies.}
5653 @cindex @option{-gnatVc} (@command{gcc})
5654 The right hand side of assignments, and the initializing values of
5655 object declarations are validity checked.
5658 @emph{Default (RM) validity checks.}
5659 @cindex @option{-gnatVd} (@command{gcc})
5660 Some validity checks are done by default following normal Ada semantics
5662 A check is done in case statements that the expression is within the range
5663 of the subtype. If it is not, Constraint_Error is raised.
5664 For assignments to array components, a check is done that the expression used
5665 as index is within the range. If it is not, Constraint_Error is raised.
5666 Both these validity checks may be turned off using switch @option{-gnatVD}.
5667 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5668 switch @option{-gnatVd} will leave the checks turned on.
5669 Switch @option{-gnatVD} should be used only if you are sure that all such
5670 expressions have valid values. If you use this switch and invalid values
5671 are present, then the program is erroneous, and wild jumps or memory
5672 overwriting may occur.
5675 @emph{Validity checks for elementary components.}
5676 @cindex @option{-gnatVe} (@command{gcc})
5677 In the absence of this switch, assignments to record or array components are
5678 not validity checked, even if validity checks for assignments generally
5679 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5680 require valid data, but assignment of individual components does. So for
5681 example, there is a difference between copying the elements of an array with a
5682 slice assignment, compared to assigning element by element in a loop. This
5683 switch allows you to turn off validity checking for components, even when they
5684 are assigned component by component.
5687 @emph{Validity checks for floating-point values.}
5688 @cindex @option{-gnatVf} (@command{gcc})
5689 In the absence of this switch, validity checking occurs only for discrete
5690 values. If @option{-gnatVf} is specified, then validity checking also applies
5691 for floating-point values, and NaNs and infinities are considered invalid,
5692 as well as out of range values for constrained types. Note that this means
5693 that standard IEEE infinity mode is not allowed. The exact contexts
5694 in which floating-point values are checked depends on the setting of other
5695 options. For example,
5696 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5697 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5698 (the order does not matter) specifies that floating-point parameters of mode
5699 @code{in} should be validity checked.
5702 @emph{Validity checks for @code{in} mode parameters}
5703 @cindex @option{-gnatVi} (@command{gcc})
5704 Arguments for parameters of mode @code{in} are validity checked in function
5705 and procedure calls at the point of call.
5708 @emph{Validity checks for @code{in out} mode parameters.}
5709 @cindex @option{-gnatVm} (@command{gcc})
5710 Arguments for parameters of mode @code{in out} are validity checked in
5711 procedure calls at the point of call. The @code{'m'} here stands for
5712 modify, since this concerns parameters that can be modified by the call.
5713 Note that there is no specific option to test @code{out} parameters,
5714 but any reference within the subprogram will be tested in the usual
5715 manner, and if an invalid value is copied back, any reference to it
5716 will be subject to validity checking.
5719 @emph{No validity checks.}
5720 @cindex @option{-gnatVn} (@command{gcc})
5721 This switch turns off all validity checking, including the default checking
5722 for case statements and left hand side subscripts. Note that the use of
5723 the switch @option{-gnatp} suppresses all run-time checks, including
5724 validity checks, and thus implies @option{-gnatVn}. When this switch
5725 is used, it cancels any other @option{-gnatV} previously issued.
5728 @emph{Validity checks for operator and attribute operands.}
5729 @cindex @option{-gnatVo} (@command{gcc})
5730 Arguments for predefined operators and attributes are validity checked.
5731 This includes all operators in package @code{Standard},
5732 the shift operators defined as intrinsic in package @code{Interfaces}
5733 and operands for attributes such as @code{Pos}. Checks are also made
5734 on individual component values for composite comparisons, and on the
5735 expressions in type conversions and qualified expressions. Checks are
5736 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5739 @emph{Validity checks for parameters.}
5740 @cindex @option{-gnatVp} (@command{gcc})
5741 This controls the treatment of parameters within a subprogram (as opposed
5742 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5743 of parameters on a call. If either of these call options is used, then
5744 normally an assumption is made within a subprogram that the input arguments
5745 have been validity checking at the point of call, and do not need checking
5746 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5747 is not made, and parameters are not assumed to be valid, so their validity
5748 will be checked (or rechecked) within the subprogram.
5751 @emph{Validity checks for function returns.}
5752 @cindex @option{-gnatVr} (@command{gcc})
5753 The expression in @code{return} statements in functions is validity
5757 @emph{Validity checks for subscripts.}
5758 @cindex @option{-gnatVs} (@command{gcc})
5759 All subscripts expressions are checked for validity, whether they appear
5760 on the right side or left side (in default mode only left side subscripts
5761 are validity checked).
5764 @emph{Validity checks for tests.}
5765 @cindex @option{-gnatVt} (@command{gcc})
5766 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5767 statements are checked, as well as guard expressions in entry calls.
5772 The @option{-gnatV} switch may be followed by
5773 ^a string of letters^a list of options^
5774 to turn on a series of validity checking options.
5776 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5777 specifies that in addition to the default validity checking, copies and
5778 function return expressions are to be validity checked.
5779 In order to make it easier
5780 to specify the desired combination of effects,
5782 the upper case letters @code{CDFIMORST} may
5783 be used to turn off the corresponding lower case option.
5786 the prefix @code{NO} on an option turns off the corresponding validity
5789 @item @code{NOCOPIES}
5790 @item @code{NODEFAULT}
5791 @item @code{NOFLOATS}
5792 @item @code{NOIN_PARAMS}
5793 @item @code{NOMOD_PARAMS}
5794 @item @code{NOOPERANDS}
5795 @item @code{NORETURNS}
5796 @item @code{NOSUBSCRIPTS}
5797 @item @code{NOTESTS}
5801 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5802 turns on all validity checking options except for
5803 checking of @code{@b{in out}} procedure arguments.
5805 The specification of additional validity checking generates extra code (and
5806 in the case of @option{-gnatVa} the code expansion can be substantial).
5807 However, these additional checks can be very useful in detecting
5808 uninitialized variables, incorrect use of unchecked conversion, and other
5809 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5810 is useful in conjunction with the extra validity checking, since this
5811 ensures that wherever possible uninitialized variables have invalid values.
5813 See also the pragma @code{Validity_Checks} which allows modification of
5814 the validity checking mode at the program source level, and also allows for
5815 temporary disabling of validity checks.
5817 @node Style Checking
5818 @subsection Style Checking
5819 @findex Style checking
5822 The @option{-gnaty^x^(option,option,@dots{})^} switch
5823 @cindex @option{-gnaty} (@command{gcc})
5824 causes the compiler to
5825 enforce specified style rules. A limited set of style rules has been used
5826 in writing the GNAT sources themselves. This switch allows user programs
5827 to activate all or some of these checks. If the source program fails a
5828 specified style check, an appropriate warning message is given, preceded by
5829 the character sequence ``(style)''.
5831 @code{(option,option,@dots{})} is a sequence of keywords
5834 The string @var{x} is a sequence of letters or digits
5836 indicating the particular style
5837 checks to be performed. The following checks are defined:
5842 @emph{Specify indentation level.}
5843 If a digit from 1-9 appears
5844 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5845 then proper indentation is checked, with the digit indicating the
5846 indentation level required. A value of zero turns off this style check.
5847 The general style of required indentation is as specified by
5848 the examples in the Ada Reference Manual. Full line comments must be
5849 aligned with the @code{--} starting on a column that is a multiple of
5850 the alignment level, or they may be aligned the same way as the following
5851 non-blank line (this is useful when full line comments appear in the middle
5855 @emph{Check attribute casing.}
5856 Attribute names, including the case of keywords such as @code{digits}
5857 used as attributes names, must be written in mixed case, that is, the
5858 initial letter and any letter following an underscore must be uppercase.
5859 All other letters must be lowercase.
5861 @item ^A^ARRAY_INDEXES^
5862 @emph{Use of array index numbers in array attributes.}
5863 When using the array attributes First, Last, Range,
5864 or Length, the index number must be omitted for one-dimensional arrays
5865 and is required for multi-dimensional arrays.
5868 @emph{Blanks not allowed at statement end.}
5869 Trailing blanks are not allowed at the end of statements. The purpose of this
5870 rule, together with h (no horizontal tabs), is to enforce a canonical format
5871 for the use of blanks to separate source tokens.
5874 @emph{Check comments.}
5875 Comments must meet the following set of rules:
5880 The ``@code{--}'' that starts the column must either start in column one,
5881 or else at least one blank must precede this sequence.
5884 Comments that follow other tokens on a line must have at least one blank
5885 following the ``@code{--}'' at the start of the comment.
5888 Full line comments must have two blanks following the ``@code{--}'' that
5889 starts the comment, with the following exceptions.
5892 A line consisting only of the ``@code{--}'' characters, possibly preceded
5893 by blanks is permitted.
5896 A comment starting with ``@code{--x}'' where @code{x} is a special character
5898 This allows proper processing of the output generated by specialized tools
5899 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5901 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5902 special character is defined as being in one of the ASCII ranges
5903 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
5904 Note that this usage is not permitted
5905 in GNAT implementation units (i.e., when @option{-gnatg} is used).
5908 A line consisting entirely of minus signs, possibly preceded by blanks, is
5909 permitted. This allows the construction of box comments where lines of minus
5910 signs are used to form the top and bottom of the box.
5913 A comment that starts and ends with ``@code{--}'' is permitted as long as at
5914 least one blank follows the initial ``@code{--}''. Together with the preceding
5915 rule, this allows the construction of box comments, as shown in the following
5918 ---------------------------
5919 -- This is a box comment --
5920 -- with two text lines. --
5921 ---------------------------
5925 @item ^d^DOS_LINE_ENDINGS^
5926 @emph{Check no DOS line terminators present.}
5927 All lines must be terminated by a single ASCII.LF
5928 character (in particular the DOS line terminator sequence CR/LF is not
5932 @emph{Check end/exit labels.}
5933 Optional labels on @code{end} statements ending subprograms and on
5934 @code{exit} statements exiting named loops, are required to be present.
5937 @emph{No form feeds or vertical tabs.}
5938 Neither form feeds nor vertical tab characters are permitted
5942 @emph{GNAT style mode}
5943 The set of style check switches is set to match that used by the GNAT sources.
5944 This may be useful when developing code that is eventually intended to be
5945 incorporated into GNAT. For further details, see GNAT sources.
5948 @emph{No horizontal tabs.}
5949 Horizontal tab characters are not permitted in the source text.
5950 Together with the b (no blanks at end of line) check, this
5951 enforces a canonical form for the use of blanks to separate
5955 @emph{Check if-then layout.}
5956 The keyword @code{then} must appear either on the same
5957 line as corresponding @code{if}, or on a line on its own, lined
5958 up under the @code{if} with at least one non-blank line in between
5959 containing all or part of the condition to be tested.
5962 @emph{check mode IN keywords}
5963 Mode @code{in} (the default mode) is not
5964 allowed to be given explicitly. @code{in out} is fine,
5965 but not @code{in} on its own.
5968 @emph{Check keyword casing.}
5969 All keywords must be in lower case (with the exception of keywords
5970 such as @code{digits} used as attribute names to which this check
5974 @emph{Check layout.}
5975 Layout of statement and declaration constructs must follow the
5976 recommendations in the Ada Reference Manual, as indicated by the
5977 form of the syntax rules. For example an @code{else} keyword must
5978 be lined up with the corresponding @code{if} keyword.
5980 There are two respects in which the style rule enforced by this check
5981 option are more liberal than those in the Ada Reference Manual. First
5982 in the case of record declarations, it is permissible to put the
5983 @code{record} keyword on the same line as the @code{type} keyword, and
5984 then the @code{end} in @code{end record} must line up under @code{type}.
5985 This is also permitted when the type declaration is split on two lines.
5986 For example, any of the following three layouts is acceptable:
5988 @smallexample @c ada
6011 Second, in the case of a block statement, a permitted alternative
6012 is to put the block label on the same line as the @code{declare} or
6013 @code{begin} keyword, and then line the @code{end} keyword up under
6014 the block label. For example both the following are permitted:
6016 @smallexample @c ada
6034 The same alternative format is allowed for loops. For example, both of
6035 the following are permitted:
6037 @smallexample @c ada
6039 Clear : while J < 10 loop
6050 @item ^Lnnn^MAX_NESTING=nnn^
6051 @emph{Set maximum nesting level}
6052 The maximum level of nesting of constructs (including subprograms, loops,
6053 blocks, packages, and conditionals) may not exceed the given value
6054 @option{nnn}. A value of zero disconnects this style check.
6056 @item ^m^LINE_LENGTH^
6057 @emph{Check maximum line length.}
6058 The length of source lines must not exceed 79 characters, including
6059 any trailing blanks. The value of 79 allows convenient display on an
6060 80 character wide device or window, allowing for possible special
6061 treatment of 80 character lines. Note that this count is of
6062 characters in the source text. This means that a tab character counts
6063 as one character in this count but a wide character sequence counts as
6064 a single character (however many bytes are needed in the encoding).
6066 @item ^Mnnn^MAX_LENGTH=nnn^
6067 @emph{Set maximum line length.}
6068 The length of lines must not exceed the
6069 given value @option{nnn}. The maximum value that can be specified is 32767.
6071 @item ^n^STANDARD_CASING^
6072 @emph{Check casing of entities in Standard.}
6073 Any identifier from Standard must be cased
6074 to match the presentation in the Ada Reference Manual (for example,
6075 @code{Integer} and @code{ASCII.NUL}).
6078 @emph{Turn off all style checks}
6079 All style check options are turned off.
6081 @item ^o^ORDERED_SUBPROGRAMS^
6082 @emph{Check order of subprogram bodies.}
6083 All subprogram bodies in a given scope
6084 (e.g.@: a package body) must be in alphabetical order. The ordering
6085 rule uses normal Ada rules for comparing strings, ignoring casing
6086 of letters, except that if there is a trailing numeric suffix, then
6087 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6090 @item ^O^OVERRIDING_INDICATORS^
6091 @emph{Check that overriding subprograms are explicitly marked as such.}
6092 The declaration of a primitive operation of a type extension that overrides
6093 an inherited operation must carry an overriding indicator.
6096 @emph{Check pragma casing.}
6097 Pragma names must be written in mixed case, that is, the
6098 initial letter and any letter following an underscore must be uppercase.
6099 All other letters must be lowercase.
6101 @item ^r^REFERENCES^
6102 @emph{Check references.}
6103 All identifier references must be cased in the same way as the
6104 corresponding declaration. No specific casing style is imposed on
6105 identifiers. The only requirement is for consistency of references
6108 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6109 @emph{Check no statements after THEN/ELSE.}
6110 No statements are allowed
6111 on the same line as a THEN or ELSE keyword following the
6112 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6113 and a special exception allows a pragma to appear after ELSE.
6116 @emph{Check separate specs.}
6117 Separate declarations (``specs'') are required for subprograms (a
6118 body is not allowed to serve as its own declaration). The only
6119 exception is that parameterless library level procedures are
6120 not required to have a separate declaration. This exception covers
6121 the most frequent form of main program procedures.
6124 @emph{Check token spacing.}
6125 The following token spacing rules are enforced:
6130 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6133 The token @code{=>} must be surrounded by spaces.
6136 The token @code{<>} must be preceded by a space or a left parenthesis.
6139 Binary operators other than @code{**} must be surrounded by spaces.
6140 There is no restriction on the layout of the @code{**} binary operator.
6143 Colon must be surrounded by spaces.
6146 Colon-equal (assignment, initialization) must be surrounded by spaces.
6149 Comma must be the first non-blank character on the line, or be
6150 immediately preceded by a non-blank character, and must be followed
6154 If the token preceding a left parenthesis ends with a letter or digit, then
6155 a space must separate the two tokens.
6158 A right parenthesis must either be the first non-blank character on
6159 a line, or it must be preceded by a non-blank character.
6162 A semicolon must not be preceded by a space, and must not be followed by
6163 a non-blank character.
6166 A unary plus or minus may not be followed by a space.
6169 A vertical bar must be surrounded by spaces.
6172 @item ^u^UNNECESSARY_BLANK_LINES^
6173 @emph{Check unnecessary blank lines.}
6174 Unnecessary blank lines are not allowed. A blank line is considered
6175 unnecessary if it appears at the end of the file, or if more than
6176 one blank line occurs in sequence.
6178 @item ^x^XTRA_PARENS^
6179 @emph{Check extra parentheses.}
6180 Unnecessary extra level of parentheses (C-style) are not allowed
6181 around conditions in @code{if} statements, @code{while} statements and
6182 @code{exit} statements.
6184 @item ^y^ALL_BUILTIN^
6185 @emph{Set all standard style check options}
6186 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6187 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6188 @option{-gnatyS}, @option{-gnatyLnnn},
6189 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6193 @emph{Remove style check options}
6194 This causes any subsequent options in the string to act as canceling the
6195 corresponding style check option. To cancel maximum nesting level control,
6196 use @option{L} parameter witout any integer value after that, because any
6197 digit following @option{-} in the parameter string of the @option{-gnaty}
6198 option will be threated as canceling indentation check. The same is true
6199 for @option{M} parameter. @option{y} and @option{N} parameters are not
6200 allowed after @option{-}.
6203 This causes any subsequent options in the string to enable the corresponding
6204 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6210 @emph{Removing style check options}
6211 If the name of a style check is preceded by @option{NO} then the corresponding
6212 style check is turned off. For example @option{NOCOMMENTS} turns off style
6213 checking for comments.
6218 In the above rules, appearing in column one is always permitted, that is,
6219 counts as meeting either a requirement for a required preceding space,
6220 or as meeting a requirement for no preceding space.
6222 Appearing at the end of a line is also always permitted, that is, counts
6223 as meeting either a requirement for a following space, or as meeting
6224 a requirement for no following space.
6227 If any of these style rules is violated, a message is generated giving
6228 details on the violation. The initial characters of such messages are
6229 always ``@code{(style)}''. Note that these messages are treated as warning
6230 messages, so they normally do not prevent the generation of an object
6231 file. The @option{-gnatwe} switch can be used to treat warning messages,
6232 including style messages, as fatal errors.
6236 @option{-gnaty} on its own (that is not
6237 followed by any letters or digits), then the effect is equivalent
6238 to the use of @option{-gnatyy}, as described above, that is all
6239 built-in standard style check options are enabled.
6243 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6244 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6245 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6257 clears any previously set style checks.
6259 @node Run-Time Checks
6260 @subsection Run-Time Checks
6261 @cindex Division by zero
6262 @cindex Access before elaboration
6263 @cindex Checks, division by zero
6264 @cindex Checks, access before elaboration
6265 @cindex Checks, stack overflow checking
6268 By default, the following checks are suppressed: integer overflow
6269 checks, stack overflow checks, and checks for access before
6270 elaboration on subprogram calls. All other checks, including range
6271 checks and array bounds checks, are turned on by default. The
6272 following @command{gcc} switches refine this default behavior.
6277 @cindex @option{-gnatp} (@command{gcc})
6278 @cindex Suppressing checks
6279 @cindex Checks, suppressing
6281 Suppress all run-time checks as though @code{pragma Suppress (All_checks)}
6282 had been present in the source. Validity checks are also suppressed (in
6283 other words @option{-gnatp} also implies @option{-gnatVn}.
6284 Use this switch to improve the performance
6285 of the code at the expense of safety in the presence of invalid data or
6288 Note that when checks are suppressed, the compiler is allowed, but not
6289 required, to omit the checking code. If the run-time cost of the
6290 checking code is zero or near-zero, the compiler will generate it even
6291 if checks are suppressed. In particular, if the compiler can prove
6292 that a certain check will necessarily fail, it will generate code to
6293 do an unconditional ``raise'', even if checks are suppressed. The
6294 compiler warns in this case.
6296 Of course, run-time checks are omitted whenever the compiler can prove
6297 that they will not fail, whether or not checks are suppressed.
6299 Note that if you suppress a check that would have failed, program
6300 execution is erroneous, which means the behavior is totally
6301 unpredictable. The program might crash, or print wrong answers, or
6302 do anything else. It might even do exactly what you wanted it to do
6303 (and then it might start failing mysteriously next week or next
6304 year). The compiler will generate code based on the assumption that
6305 the condition being checked is true, which can result in disaster if
6306 that assumption is wrong.
6309 @cindex @option{-gnato} (@command{gcc})
6310 @cindex Overflow checks
6311 @cindex Check, overflow
6312 Enables overflow checking for integer operations.
6313 This causes GNAT to generate slower and larger executable
6314 programs by adding code to check for overflow (resulting in raising
6315 @code{Constraint_Error} as required by standard Ada
6316 semantics). These overflow checks correspond to situations in which
6317 the true value of the result of an operation may be outside the base
6318 range of the result type. The following example shows the distinction:
6320 @smallexample @c ada
6321 X1 : Integer := "Integer'Last";
6322 X2 : Integer range 1 .. 5 := "5";
6323 X3 : Integer := "Integer'Last";
6324 X4 : Integer range 1 .. 5 := "5";
6325 F : Float := "2.0E+20";
6334 Note that if explicit values are assigned at compile time, the
6335 compiler may be able to detect overflow at compile time, in which case
6336 no actual run-time checking code is required, and Constraint_Error
6337 will be raised unconditionally, with or without
6338 @option{-gnato}. That's why the assigned values in the above fragment
6339 are in quotes, the meaning is "assign a value not known to the
6340 compiler that happens to be equal to ...". The remaining discussion
6341 assumes that the compiler cannot detect the values at compile time.
6343 Here the first addition results in a value that is outside the base range
6344 of Integer, and hence requires an overflow check for detection of the
6345 constraint error. Thus the first assignment to @code{X1} raises a
6346 @code{Constraint_Error} exception only if @option{-gnato} is set.
6348 The second increment operation results in a violation of the explicit
6349 range constraint; such range checks are performed by default, and are
6350 unaffected by @option{-gnato}.
6352 The two conversions of @code{F} both result in values that are outside
6353 the base range of type @code{Integer} and thus will raise
6354 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6355 The fact that the result of the second conversion is assigned to
6356 variable @code{X4} with a restricted range is irrelevant, since the problem
6357 is in the conversion, not the assignment.
6359 Basically the rule is that in the default mode (@option{-gnato} not
6360 used), the generated code assures that all integer variables stay
6361 within their declared ranges, or within the base range if there is
6362 no declared range. This prevents any serious problems like indexes
6363 out of range for array operations.
6365 What is not checked in default mode is an overflow that results in
6366 an in-range, but incorrect value. In the above example, the assignments
6367 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6368 range of the target variable, but the result is wrong in the sense that
6369 it is too large to be represented correctly. Typically the assignment
6370 to @code{X1} will result in wrap around to the largest negative number.
6371 The conversions of @code{F} will result in some @code{Integer} value
6372 and if that integer value is out of the @code{X4} range then the
6373 subsequent assignment would generate an exception.
6375 @findex Machine_Overflows
6376 Note that the @option{-gnato} switch does not affect the code generated
6377 for any floating-point operations; it applies only to integer
6379 For floating-point, GNAT has the @code{Machine_Overflows}
6380 attribute set to @code{False} and the normal mode of operation is to
6381 generate IEEE NaN and infinite values on overflow or invalid operations
6382 (such as dividing 0.0 by 0.0).
6384 The reason that we distinguish overflow checking from other kinds of
6385 range constraint checking is that a failure of an overflow check, unlike
6386 for example the failure of a range check, can result in an incorrect
6387 value, but cannot cause random memory destruction (like an out of range
6388 subscript), or a wild jump (from an out of range case value). Overflow
6389 checking is also quite expensive in time and space, since in general it
6390 requires the use of double length arithmetic.
6392 Note again that @option{-gnato} is off by default, so overflow checking is
6393 not performed in default mode. This means that out of the box, with the
6394 default settings, GNAT does not do all the checks expected from the
6395 language description in the Ada Reference Manual. If you want all constraint
6396 checks to be performed, as described in this Manual, then you must
6397 explicitly use the -gnato switch either on the @command{gnatmake} or
6398 @command{gcc} command.
6401 @cindex @option{-gnatE} (@command{gcc})
6402 @cindex Elaboration checks
6403 @cindex Check, elaboration
6404 Enables dynamic checks for access-before-elaboration
6405 on subprogram calls and generic instantiations.
6406 Note that @option{-gnatE} is not necessary for safety, because in the
6407 default mode, GNAT ensures statically that the checks would not fail.
6408 For full details of the effect and use of this switch,
6409 @xref{Compiling Using gcc}.
6412 @cindex @option{-fstack-check} (@command{gcc})
6413 @cindex Stack Overflow Checking
6414 @cindex Checks, stack overflow checking
6415 Activates stack overflow checking. For full details of the effect and use of
6416 this switch see @ref{Stack Overflow Checking}.
6421 The setting of these switches only controls the default setting of the
6422 checks. You may modify them using either @code{Suppress} (to remove
6423 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6426 @node Using gcc for Syntax Checking
6427 @subsection Using @command{gcc} for Syntax Checking
6430 @cindex @option{-gnats} (@command{gcc})
6434 The @code{s} stands for ``syntax''.
6437 Run GNAT in syntax checking only mode. For
6438 example, the command
6441 $ gcc -c -gnats x.adb
6445 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6446 series of files in a single command
6448 , and can use wild cards to specify such a group of files.
6449 Note that you must specify the @option{-c} (compile
6450 only) flag in addition to the @option{-gnats} flag.
6453 You may use other switches in conjunction with @option{-gnats}. In
6454 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6455 format of any generated error messages.
6457 When the source file is empty or contains only empty lines and/or comments,
6458 the output is a warning:
6461 $ gcc -c -gnats -x ada toto.txt
6462 toto.txt:1:01: warning: empty file, contains no compilation units
6466 Otherwise, the output is simply the error messages, if any. No object file or
6467 ALI file is generated by a syntax-only compilation. Also, no units other
6468 than the one specified are accessed. For example, if a unit @code{X}
6469 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6470 check only mode does not access the source file containing unit
6473 @cindex Multiple units, syntax checking
6474 Normally, GNAT allows only a single unit in a source file. However, this
6475 restriction does not apply in syntax-check-only mode, and it is possible
6476 to check a file containing multiple compilation units concatenated
6477 together. This is primarily used by the @code{gnatchop} utility
6478 (@pxref{Renaming Files Using gnatchop}).
6481 @node Using gcc for Semantic Checking
6482 @subsection Using @command{gcc} for Semantic Checking
6485 @cindex @option{-gnatc} (@command{gcc})
6489 The @code{c} stands for ``check''.
6491 Causes the compiler to operate in semantic check mode,
6492 with full checking for all illegalities specified in the
6493 Ada Reference Manual, but without generation of any object code
6494 (no object file is generated).
6496 Because dependent files must be accessed, you must follow the GNAT
6497 semantic restrictions on file structuring to operate in this mode:
6501 The needed source files must be accessible
6502 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6505 Each file must contain only one compilation unit.
6508 The file name and unit name must match (@pxref{File Naming Rules}).
6511 The output consists of error messages as appropriate. No object file is
6512 generated. An @file{ALI} file is generated for use in the context of
6513 cross-reference tools, but this file is marked as not being suitable
6514 for binding (since no object file is generated).
6515 The checking corresponds exactly to the notion of
6516 legality in the Ada Reference Manual.
6518 Any unit can be compiled in semantics-checking-only mode, including
6519 units that would not normally be compiled (subunits,
6520 and specifications where a separate body is present).
6523 @node Compiling Different Versions of Ada
6524 @subsection Compiling Different Versions of Ada
6527 The switches described in this section allow you to explicitly specify
6528 the version of the Ada language that your programs are written in.
6529 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6530 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6531 indicate Ada 83 compatibility mode.
6534 @cindex Compatibility with Ada 83
6536 @item -gnat83 (Ada 83 Compatibility Mode)
6537 @cindex @option{-gnat83} (@command{gcc})
6538 @cindex ACVC, Ada 83 tests
6542 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6543 specifies that the program is to be compiled in Ada 83 mode. With
6544 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6545 semantics where this can be done easily.
6546 It is not possible to guarantee this switch does a perfect
6547 job; some subtle tests, such as are
6548 found in earlier ACVC tests (and that have been removed from the ACATS suite
6549 for Ada 95), might not compile correctly.
6550 Nevertheless, this switch may be useful in some circumstances, for example
6551 where, due to contractual reasons, existing code needs to be maintained
6552 using only Ada 83 features.
6554 With few exceptions (most notably the need to use @code{<>} on
6555 @cindex Generic formal parameters
6556 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6557 reserved words, and the use of packages
6558 with optional bodies), it is not necessary to specify the
6559 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6560 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6561 a correct Ada 83 program is usually also a correct program
6562 in these later versions of the language standard.
6563 For further information, please refer to @ref{Compatibility and Porting Guide}.
6565 @item -gnat95 (Ada 95 mode)
6566 @cindex @option{-gnat95} (@command{gcc})
6570 This switch directs the compiler to implement the Ada 95 version of the
6572 Since Ada 95 is almost completely upwards
6573 compatible with Ada 83, Ada 83 programs may generally be compiled using
6574 this switch (see the description of the @option{-gnat83} switch for further
6575 information about Ada 83 mode).
6576 If an Ada 2005 program is compiled in Ada 95 mode,
6577 uses of the new Ada 2005 features will cause error
6578 messages or warnings.
6580 This switch also can be used to cancel the effect of a previous
6581 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6583 @item -gnat05 (Ada 2005 mode)
6584 @cindex @option{-gnat05} (@command{gcc})
6585 @cindex Ada 2005 mode
6588 This switch directs the compiler to implement the Ada 2005 version of the
6590 Since Ada 2005 is almost completely upwards
6591 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6592 may generally be compiled using this switch (see the description of the
6593 @option{-gnat83} and @option{-gnat95} switches for further
6596 For information about the approved ``Ada Issues'' that have been incorporated
6597 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6598 Included with GNAT releases is a file @file{features-ada0y} that describes
6599 the set of implemented Ada 2005 features.
6603 @node Character Set Control
6604 @subsection Character Set Control
6606 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6607 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6610 Normally GNAT recognizes the Latin-1 character set in source program
6611 identifiers, as described in the Ada Reference Manual.
6613 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6614 single character ^^or word^ indicating the character set, as follows:
6618 ISO 8859-1 (Latin-1) identifiers
6621 ISO 8859-2 (Latin-2) letters allowed in identifiers
6624 ISO 8859-3 (Latin-3) letters allowed in identifiers
6627 ISO 8859-4 (Latin-4) letters allowed in identifiers
6630 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6633 ISO 8859-15 (Latin-9) letters allowed in identifiers
6636 IBM PC letters (code page 437) allowed in identifiers
6639 IBM PC letters (code page 850) allowed in identifiers
6641 @item ^f^FULL_UPPER^
6642 Full upper-half codes allowed in identifiers
6645 No upper-half codes allowed in identifiers
6648 Wide-character codes (that is, codes greater than 255)
6649 allowed in identifiers
6652 @xref{Foreign Language Representation}, for full details on the
6653 implementation of these character sets.
6655 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6656 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6657 Specify the method of encoding for wide characters.
6658 @var{e} is one of the following:
6663 Hex encoding (brackets coding also recognized)
6666 Upper half encoding (brackets encoding also recognized)
6669 Shift/JIS encoding (brackets encoding also recognized)
6672 EUC encoding (brackets encoding also recognized)
6675 UTF-8 encoding (brackets encoding also recognized)
6678 Brackets encoding only (default value)
6680 For full details on these encoding
6681 methods see @ref{Wide Character Encodings}.
6682 Note that brackets coding is always accepted, even if one of the other
6683 options is specified, so for example @option{-gnatW8} specifies that both
6684 brackets and UTF-8 encodings will be recognized. The units that are
6685 with'ed directly or indirectly will be scanned using the specified
6686 representation scheme, and so if one of the non-brackets scheme is
6687 used, it must be used consistently throughout the program. However,
6688 since brackets encoding is always recognized, it may be conveniently
6689 used in standard libraries, allowing these libraries to be used with
6690 any of the available coding schemes.
6693 If no @option{-gnatW?} parameter is present, then the default
6694 representation is normally Brackets encoding only. However, if the
6695 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6696 byte order mark or BOM for UTF-8), then these three characters are
6697 skipped and the default representation for the file is set to UTF-8.
6699 Note that the wide character representation that is specified (explicitly
6700 or by default) for the main program also acts as the default encoding used
6701 for Wide_Text_IO files if not specifically overridden by a WCEM form
6705 @node File Naming Control
6706 @subsection File Naming Control
6709 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6710 @cindex @option{-gnatk} (@command{gcc})
6711 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6712 1-999, indicates the maximum allowable length of a file name (not
6713 including the @file{.ads} or @file{.adb} extension). The default is not
6714 to enable file name krunching.
6716 For the source file naming rules, @xref{File Naming Rules}.
6719 @node Subprogram Inlining Control
6720 @subsection Subprogram Inlining Control
6725 @cindex @option{-gnatn} (@command{gcc})
6727 The @code{n} here is intended to suggest the first syllable of the
6730 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6731 inlining to actually occur, optimization must be enabled. To enable
6732 inlining of subprograms specified by pragma @code{Inline},
6733 you must also specify this switch.
6734 In the absence of this switch, GNAT does not attempt
6735 inlining and does not need to access the bodies of
6736 subprograms for which @code{pragma Inline} is specified if they are not
6737 in the current unit.
6739 If you specify this switch the compiler will access these bodies,
6740 creating an extra source dependency for the resulting object file, and
6741 where possible, the call will be inlined.
6742 For further details on when inlining is possible
6743 see @ref{Inlining of Subprograms}.
6746 @cindex @option{-gnatN} (@command{gcc})
6747 This switch activates front-end inlining which also
6748 generates additional dependencies.
6750 When using a gcc-based back end (in practice this means using any version
6751 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
6752 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
6753 Historically front end inlining was more extensive than the gcc back end
6754 inlining, but that is no longer the case.
6757 @node Auxiliary Output Control
6758 @subsection Auxiliary Output Control
6762 @cindex @option{-gnatt} (@command{gcc})
6763 @cindex Writing internal trees
6764 @cindex Internal trees, writing to file
6765 Causes GNAT to write the internal tree for a unit to a file (with the
6766 extension @file{.adt}.
6767 This not normally required, but is used by separate analysis tools.
6769 these tools do the necessary compilations automatically, so you should
6770 not have to specify this switch in normal operation.
6773 @cindex @option{-gnatu} (@command{gcc})
6774 Print a list of units required by this compilation on @file{stdout}.
6775 The listing includes all units on which the unit being compiled depends
6776 either directly or indirectly.
6779 @item -pass-exit-codes
6780 @cindex @option{-pass-exit-codes} (@command{gcc})
6781 If this switch is not used, the exit code returned by @command{gcc} when
6782 compiling multiple files indicates whether all source files have
6783 been successfully used to generate object files or not.
6785 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
6786 exit status and allows an integrated development environment to better
6787 react to a compilation failure. Those exit status are:
6791 There was an error in at least one source file.
6793 At least one source file did not generate an object file.
6795 The compiler died unexpectedly (internal error for example).
6797 An object file has been generated for every source file.
6802 @node Debugging Control
6803 @subsection Debugging Control
6807 @cindex Debugging options
6810 @cindex @option{-gnatd} (@command{gcc})
6811 Activate internal debugging switches. @var{x} is a letter or digit, or
6812 string of letters or digits, which specifies the type of debugging
6813 outputs desired. Normally these are used only for internal development
6814 or system debugging purposes. You can find full documentation for these
6815 switches in the body of the @code{Debug} unit in the compiler source
6816 file @file{debug.adb}.
6820 @cindex @option{-gnatG} (@command{gcc})
6821 This switch causes the compiler to generate auxiliary output containing
6822 a pseudo-source listing of the generated expanded code. Like most Ada
6823 compilers, GNAT works by first transforming the high level Ada code into
6824 lower level constructs. For example, tasking operations are transformed
6825 into calls to the tasking run-time routines. A unique capability of GNAT
6826 is to list this expanded code in a form very close to normal Ada source.
6827 This is very useful in understanding the implications of various Ada
6828 usage on the efficiency of the generated code. There are many cases in
6829 Ada (e.g.@: the use of controlled types), where simple Ada statements can
6830 generate a lot of run-time code. By using @option{-gnatG} you can identify
6831 these cases, and consider whether it may be desirable to modify the coding
6832 approach to improve efficiency.
6834 The optional parameter @code{nn} if present after -gnatG specifies an
6835 alternative maximum line length that overrides the normal default of 72.
6836 This value is in the range 40-999999, values less than 40 being silently
6837 reset to 40. The equal sign is optional.
6839 The format of the output is very similar to standard Ada source, and is
6840 easily understood by an Ada programmer. The following special syntactic
6841 additions correspond to low level features used in the generated code that
6842 do not have any exact analogies in pure Ada source form. The following
6843 is a partial list of these special constructions. See the spec
6844 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6846 If the switch @option{-gnatL} is used in conjunction with
6847 @cindex @option{-gnatL} (@command{gcc})
6848 @option{-gnatG}, then the original source lines are interspersed
6849 in the expanded source (as comment lines with the original line number).
6852 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
6853 Shows the storage pool being used for an allocator.
6855 @item at end @var{procedure-name};
6856 Shows the finalization (cleanup) procedure for a scope.
6858 @item (if @var{expr} then @var{expr} else @var{expr})
6859 Conditional expression equivalent to the @code{x?y:z} construction in C.
6861 @item @var{target}^^^(@var{source})
6862 A conversion with floating-point truncation instead of rounding.
6864 @item @var{target}?(@var{source})
6865 A conversion that bypasses normal Ada semantic checking. In particular
6866 enumeration types and fixed-point types are treated simply as integers.
6868 @item @var{target}?^^^(@var{source})
6869 Combines the above two cases.
6871 @item @var{x} #/ @var{y}
6872 @itemx @var{x} #mod @var{y}
6873 @itemx @var{x} #* @var{y}
6874 @itemx @var{x} #rem @var{y}
6875 A division or multiplication of fixed-point values which are treated as
6876 integers without any kind of scaling.
6878 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
6879 Shows the storage pool associated with a @code{free} statement.
6881 @item [subtype or type declaration]
6882 Used to list an equivalent declaration for an internally generated
6883 type that is referenced elsewhere in the listing.
6885 @item freeze @var{type-name} @ovar{actions}
6886 Shows the point at which @var{type-name} is frozen, with possible
6887 associated actions to be performed at the freeze point.
6889 @item reference @var{itype}
6890 Reference (and hence definition) to internal type @var{itype}.
6892 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6893 Intrinsic function call.
6895 @item @var{label-name} : label
6896 Declaration of label @var{labelname}.
6898 @item #$ @var{subprogram-name}
6899 An implicit call to a run-time support routine
6900 (to meet the requirement of H.3.1(9) in a
6903 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
6904 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6905 @var{expr}, but handled more efficiently).
6907 @item [constraint_error]
6908 Raise the @code{Constraint_Error} exception.
6910 @item @var{expression}'reference
6911 A pointer to the result of evaluating @var{expression}.
6913 @item @var{target-type}!(@var{source-expression})
6914 An unchecked conversion of @var{source-expression} to @var{target-type}.
6916 @item [@var{numerator}/@var{denominator}]
6917 Used to represent internal real literals (that) have no exact
6918 representation in base 2-16 (for example, the result of compile time
6919 evaluation of the expression 1.0/27.0).
6923 @cindex @option{-gnatD} (@command{gcc})
6924 When used in conjunction with @option{-gnatG}, this switch causes
6925 the expanded source, as described above for
6926 @option{-gnatG} to be written to files with names
6927 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6928 instead of to the standard output file. For
6929 example, if the source file name is @file{hello.adb}, then a file
6930 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6931 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
6932 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6933 you to do source level debugging using the generated code which is
6934 sometimes useful for complex code, for example to find out exactly
6935 which part of a complex construction raised an exception. This switch
6936 also suppress generation of cross-reference information (see
6937 @option{-gnatx}) since otherwise the cross-reference information
6938 would refer to the @file{^.dg^.DG^} file, which would cause
6939 confusion since this is not the original source file.
6941 Note that @option{-gnatD} actually implies @option{-gnatG}
6942 automatically, so it is not necessary to give both options.
6943 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6945 If the switch @option{-gnatL} is used in conjunction with
6946 @cindex @option{-gnatL} (@command{gcc})
6947 @option{-gnatDG}, then the original source lines are interspersed
6948 in the expanded source (as comment lines with the original line number).
6950 The optional parameter @code{nn} if present after -gnatD specifies an
6951 alternative maximum line length that overrides the normal default of 72.
6952 This value is in the range 40-999999, values less than 40 being silently
6953 reset to 40. The equal sign is optional.
6956 @cindex @option{-gnatr} (@command{gcc})
6957 @cindex pragma Restrictions
6958 This switch causes pragma Restrictions to be treated as Restriction_Warnings
6959 so that violation of restrictions causes warnings rather than illegalities.
6960 This is useful during the development process when new restrictions are added
6961 or investigated. The switch also causes pragma Profile to be treated as
6962 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
6963 restriction warnings rather than restrictions.
6966 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
6967 @cindex @option{-gnatR} (@command{gcc})
6968 This switch controls output from the compiler of a listing showing
6969 representation information for declared types and objects. For
6970 @option{-gnatR0}, no information is output (equivalent to omitting
6971 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6972 so @option{-gnatR} with no parameter has the same effect), size and alignment
6973 information is listed for declared array and record types. For
6974 @option{-gnatR2}, size and alignment information is listed for all
6975 declared types and objects. Finally @option{-gnatR3} includes symbolic
6976 expressions for values that are computed at run time for
6977 variant records. These symbolic expressions have a mostly obvious
6978 format with #n being used to represent the value of the n'th
6979 discriminant. See source files @file{repinfo.ads/adb} in the
6980 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6981 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
6982 the output is to a file with the name @file{^file.rep^file_REP^} where
6983 file is the name of the corresponding source file.
6986 @item /REPRESENTATION_INFO
6987 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
6988 This qualifier controls output from the compiler of a listing showing
6989 representation information for declared types and objects. For
6990 @option{/REPRESENTATION_INFO=NONE}, no information is output
6991 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6992 @option{/REPRESENTATION_INFO} without option is equivalent to
6993 @option{/REPRESENTATION_INFO=ARRAYS}.
6994 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6995 information is listed for declared array and record types. For
6996 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6997 is listed for all expression information for values that are computed
6998 at run time for variant records. These symbolic expressions have a mostly
6999 obvious format with #n being used to represent the value of the n'th
7000 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7001 @code{GNAT} sources for full details on the format of
7002 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7003 If _FILE is added at the end of an option
7004 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7005 then the output is to a file with the name @file{file_REP} where
7006 file is the name of the corresponding source file.
7008 Note that it is possible for record components to have zero size. In
7009 this case, the component clause uses an obvious extension of permitted
7010 Ada syntax, for example @code{at 0 range 0 .. -1}.
7012 Representation information requires that code be generated (since it is the
7013 code generator that lays out complex data structures). If an attempt is made
7014 to output representation information when no code is generated, for example
7015 when a subunit is compiled on its own, then no information can be generated
7016 and the compiler outputs a message to this effect.
7019 @cindex @option{-gnatS} (@command{gcc})
7020 The use of the switch @option{-gnatS} for an
7021 Ada compilation will cause the compiler to output a
7022 representation of package Standard in a form very
7023 close to standard Ada. It is not quite possible to
7024 do this entirely in standard Ada (since new
7025 numeric base types cannot be created in standard
7026 Ada), but the output is easily
7027 readable to any Ada programmer, and is useful to
7028 determine the characteristics of target dependent
7029 types in package Standard.
7032 @cindex @option{-gnatx} (@command{gcc})
7033 Normally the compiler generates full cross-referencing information in
7034 the @file{ALI} file. This information is used by a number of tools,
7035 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7036 suppresses this information. This saves some space and may slightly
7037 speed up compilation, but means that these tools cannot be used.
7040 @node Exception Handling Control
7041 @subsection Exception Handling Control
7044 GNAT uses two methods for handling exceptions at run-time. The
7045 @code{setjmp/longjmp} method saves the context when entering
7046 a frame with an exception handler. Then when an exception is
7047 raised, the context can be restored immediately, without the
7048 need for tracing stack frames. This method provides very fast
7049 exception propagation, but introduces significant overhead for
7050 the use of exception handlers, even if no exception is raised.
7052 The other approach is called ``zero cost'' exception handling.
7053 With this method, the compiler builds static tables to describe
7054 the exception ranges. No dynamic code is required when entering
7055 a frame containing an exception handler. When an exception is
7056 raised, the tables are used to control a back trace of the
7057 subprogram invocation stack to locate the required exception
7058 handler. This method has considerably poorer performance for
7059 the propagation of exceptions, but there is no overhead for
7060 exception handlers if no exception is raised. Note that in this
7061 mode and in the context of mixed Ada and C/C++ programming,
7062 to propagate an exception through a C/C++ code, the C/C++ code
7063 must be compiled with the @option{-funwind-tables} GCC's
7066 The following switches may be used to control which of the
7067 two exception handling methods is used.
7073 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7074 This switch causes the setjmp/longjmp run-time (when available) to be used
7075 for exception handling. If the default
7076 mechanism for the target is zero cost exceptions, then
7077 this switch can be used to modify this default, and must be
7078 used for all units in the partition.
7079 This option is rarely used. One case in which it may be
7080 advantageous is if you have an application where exception
7081 raising is common and the overall performance of the
7082 application is improved by favoring exception propagation.
7085 @cindex @option{--RTS=zcx} (@command{gnatmake})
7086 @cindex Zero Cost Exceptions
7087 This switch causes the zero cost approach to be used
7088 for exception handling. If this is the default mechanism for the
7089 target (see below), then this switch is unneeded. If the default
7090 mechanism for the target is setjmp/longjmp exceptions, then
7091 this switch can be used to modify this default, and must be
7092 used for all units in the partition.
7093 This option can only be used if the zero cost approach
7094 is available for the target in use, otherwise it will generate an error.
7098 The same option @option{--RTS} must be used both for @command{gcc}
7099 and @command{gnatbind}. Passing this option to @command{gnatmake}
7100 (@pxref{Switches for gnatmake}) will ensure the required consistency
7101 through the compilation and binding steps.
7103 @node Units to Sources Mapping Files
7104 @subsection Units to Sources Mapping Files
7108 @item -gnatem^^=^@var{path}
7109 @cindex @option{-gnatem} (@command{gcc})
7110 A mapping file is a way to communicate to the compiler two mappings:
7111 from unit names to file names (without any directory information) and from
7112 file names to path names (with full directory information). These mappings
7113 are used by the compiler to short-circuit the path search.
7115 The use of mapping files is not required for correct operation of the
7116 compiler, but mapping files can improve efficiency, particularly when
7117 sources are read over a slow network connection. In normal operation,
7118 you need not be concerned with the format or use of mapping files,
7119 and the @option{-gnatem} switch is not a switch that you would use
7120 explicitly. it is intended only for use by automatic tools such as
7121 @command{gnatmake} running under the project file facility. The
7122 description here of the format of mapping files is provided
7123 for completeness and for possible use by other tools.
7125 A mapping file is a sequence of sets of three lines. In each set,
7126 the first line is the unit name, in lower case, with ``@code{%s}''
7128 specs and ``@code{%b}'' appended for bodies; the second line is the
7129 file name; and the third line is the path name.
7135 /gnat/project1/sources/main.2.ada
7138 When the switch @option{-gnatem} is specified, the compiler will create
7139 in memory the two mappings from the specified file. If there is any problem
7140 (nonexistent file, truncated file or duplicate entries), no mapping will
7143 Several @option{-gnatem} switches may be specified; however, only the last
7144 one on the command line will be taken into account.
7146 When using a project file, @command{gnatmake} create a temporary mapping file
7147 and communicates it to the compiler using this switch.
7151 @node Integrated Preprocessing
7152 @subsection Integrated Preprocessing
7155 GNAT sources may be preprocessed immediately before compilation.
7156 In this case, the actual
7157 text of the source is not the text of the source file, but is derived from it
7158 through a process called preprocessing. Integrated preprocessing is specified
7159 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7160 indicates, through a text file, the preprocessing data to be used.
7161 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7164 Note that when integrated preprocessing is used, the output from the
7165 preprocessor is not written to any external file. Instead it is passed
7166 internally to the compiler. If you need to preserve the result of
7167 preprocessing in a file, then you should use @command{gnatprep}
7168 to perform the desired preprocessing in stand-alone mode.
7171 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7172 used when Integrated Preprocessing is used. The reason is that preprocessing
7173 with another Preprocessing Data file without changing the sources will
7174 not trigger recompilation without this switch.
7177 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7178 always trigger recompilation for sources that are preprocessed,
7179 because @command{gnatmake} cannot compute the checksum of the source after
7183 The actual preprocessing function is described in details in section
7184 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7185 preprocessing is triggered and parameterized.
7189 @item -gnatep=@var{file}
7190 @cindex @option{-gnatep} (@command{gcc})
7191 This switch indicates to the compiler the file name (without directory
7192 information) of the preprocessor data file to use. The preprocessor data file
7193 should be found in the source directories.
7196 A preprocessing data file is a text file with significant lines indicating
7197 how should be preprocessed either a specific source or all sources not
7198 mentioned in other lines. A significant line is a nonempty, non-comment line.
7199 Comments are similar to Ada comments.
7202 Each significant line starts with either a literal string or the character '*'.
7203 A literal string is the file name (without directory information) of the source
7204 to preprocess. A character '*' indicates the preprocessing for all the sources
7205 that are not specified explicitly on other lines (order of the lines is not
7206 significant). It is an error to have two lines with the same file name or two
7207 lines starting with the character '*'.
7210 After the file name or the character '*', another optional literal string
7211 indicating the file name of the definition file to be used for preprocessing
7212 (@pxref{Form of Definitions File}). The definition files are found by the
7213 compiler in one of the source directories. In some cases, when compiling
7214 a source in a directory other than the current directory, if the definition
7215 file is in the current directory, it may be necessary to add the current
7216 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7217 the compiler would not find the definition file.
7220 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7221 be found. Those ^switches^switches^ are:
7226 Causes both preprocessor lines and the lines deleted by
7227 preprocessing to be replaced by blank lines, preserving the line number.
7228 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7229 it cancels the effect of @option{-c}.
7232 Causes both preprocessor lines and the lines deleted
7233 by preprocessing to be retained as comments marked
7234 with the special string ``@code{--! }''.
7236 @item -Dsymbol=value
7237 Define or redefine a symbol, associated with value. A symbol is an Ada
7238 identifier, or an Ada reserved word, with the exception of @code{if},
7239 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7240 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7241 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7242 same name defined in a definition file.
7245 Causes a sorted list of symbol names and values to be
7246 listed on the standard output file.
7249 Causes undefined symbols to be treated as having the value @code{FALSE}
7251 of a preprocessor test. In the absence of this option, an undefined symbol in
7252 a @code{#if} or @code{#elsif} test will be treated as an error.
7257 Examples of valid lines in a preprocessor data file:
7260 "toto.adb" "prep.def" -u
7261 -- preprocess "toto.adb", using definition file "prep.def",
7262 -- undefined symbol are False.
7265 -- preprocess all other sources without a definition file;
7266 -- suppressed lined are commented; symbol VERSION has the value V101.
7268 "titi.adb" "prep2.def" -s
7269 -- preprocess "titi.adb", using definition file "prep2.def";
7270 -- list all symbols with their values.
7273 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7274 @cindex @option{-gnateD} (@command{gcc})
7275 Define or redefine a preprocessing symbol, associated with value. If no value
7276 is given on the command line, then the value of the symbol is @code{True}.
7277 A symbol is an identifier, following normal Ada (case-insensitive)
7278 rules for its syntax, and value is any sequence (including an empty sequence)
7279 of characters from the set (letters, digits, period, underline).
7280 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7281 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7284 A symbol declared with this ^switch^switch^ on the command line replaces a
7285 symbol with the same name either in a definition file or specified with a
7286 ^switch^switch^ -D in the preprocessor data file.
7289 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7292 When integrated preprocessing is performed and the preprocessor modifies
7293 the source text, write the result of this preprocessing into a file
7294 <source>^.prep^_prep^.
7298 @node Code Generation Control
7299 @subsection Code Generation Control
7303 The GCC technology provides a wide range of target dependent
7304 @option{-m} switches for controlling
7305 details of code generation with respect to different versions of
7306 architectures. This includes variations in instruction sets (e.g.@:
7307 different members of the power pc family), and different requirements
7308 for optimal arrangement of instructions (e.g.@: different members of
7309 the x86 family). The list of available @option{-m} switches may be
7310 found in the GCC documentation.
7312 Use of these @option{-m} switches may in some cases result in improved
7315 The GNAT Pro technology is tested and qualified without any
7316 @option{-m} switches,
7317 so generally the most reliable approach is to avoid the use of these
7318 switches. However, we generally expect most of these switches to work
7319 successfully with GNAT Pro, and many customers have reported successful
7320 use of these options.
7322 Our general advice is to avoid the use of @option{-m} switches unless
7323 special needs lead to requirements in this area. In particular,
7324 there is no point in using @option{-m} switches to improve performance
7325 unless you actually see a performance improvement.
7329 @subsection Return Codes
7330 @cindex Return Codes
7331 @cindex @option{/RETURN_CODES=VMS}
7334 On VMS, GNAT compiled programs return POSIX-style codes by default,
7335 e.g.@: @option{/RETURN_CODES=POSIX}.
7337 To enable VMS style return codes, use GNAT BIND and LINK with the option
7338 @option{/RETURN_CODES=VMS}. For example:
7341 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7342 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7346 Programs built with /RETURN_CODES=VMS are suitable to be called in
7347 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7348 are suitable for spawning with appropriate GNAT RTL routines.
7352 @node Search Paths and the Run-Time Library (RTL)
7353 @section Search Paths and the Run-Time Library (RTL)
7356 With the GNAT source-based library system, the compiler must be able to
7357 find source files for units that are needed by the unit being compiled.
7358 Search paths are used to guide this process.
7360 The compiler compiles one source file whose name must be given
7361 explicitly on the command line. In other words, no searching is done
7362 for this file. To find all other source files that are needed (the most
7363 common being the specs of units), the compiler examines the following
7364 directories, in the following order:
7368 The directory containing the source file of the main unit being compiled
7369 (the file name on the command line).
7372 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7373 @command{gcc} command line, in the order given.
7376 @findex ADA_PRJ_INCLUDE_FILE
7377 Each of the directories listed in the text file whose name is given
7378 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7381 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7382 driver when project files are used. It should not normally be set
7386 @findex ADA_INCLUDE_PATH
7387 Each of the directories listed in the value of the
7388 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7390 Construct this value
7391 exactly as the @env{PATH} environment variable: a list of directory
7392 names separated by colons (semicolons when working with the NT version).
7395 Normally, define this value as a logical name containing a comma separated
7396 list of directory names.
7398 This variable can also be defined by means of an environment string
7399 (an argument to the HP C exec* set of functions).
7403 DEFINE ANOTHER_PATH FOO:[BAG]
7404 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7407 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7408 first, followed by the standard Ada
7409 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7410 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7411 (Text_IO, Sequential_IO, etc)
7412 instead of the standard Ada packages. Thus, in order to get the standard Ada
7413 packages by default, ADA_INCLUDE_PATH must be redefined.
7417 The content of the @file{ada_source_path} file which is part of the GNAT
7418 installation tree and is used to store standard libraries such as the
7419 GNAT Run Time Library (RTL) source files.
7421 @ref{Installing a library}
7426 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7427 inhibits the use of the directory
7428 containing the source file named in the command line. You can still
7429 have this directory on your search path, but in this case it must be
7430 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7432 Specifying the switch @option{-nostdinc}
7433 inhibits the search of the default location for the GNAT Run Time
7434 Library (RTL) source files.
7436 The compiler outputs its object files and ALI files in the current
7439 Caution: The object file can be redirected with the @option{-o} switch;
7440 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7441 so the @file{ALI} file will not go to the right place. Therefore, you should
7442 avoid using the @option{-o} switch.
7446 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7447 children make up the GNAT RTL, together with the simple @code{System.IO}
7448 package used in the @code{"Hello World"} example. The sources for these units
7449 are needed by the compiler and are kept together in one directory. Not
7450 all of the bodies are needed, but all of the sources are kept together
7451 anyway. In a normal installation, you need not specify these directory
7452 names when compiling or binding. Either the environment variables or
7453 the built-in defaults cause these files to be found.
7455 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7456 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7457 consisting of child units of @code{GNAT}. This is a collection of generally
7458 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7459 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7461 Besides simplifying access to the RTL, a major use of search paths is
7462 in compiling sources from multiple directories. This can make
7463 development environments much more flexible.
7465 @node Order of Compilation Issues
7466 @section Order of Compilation Issues
7469 If, in our earlier example, there was a spec for the @code{hello}
7470 procedure, it would be contained in the file @file{hello.ads}; yet this
7471 file would not have to be explicitly compiled. This is the result of the
7472 model we chose to implement library management. Some of the consequences
7473 of this model are as follows:
7477 There is no point in compiling specs (except for package
7478 specs with no bodies) because these are compiled as needed by clients. If
7479 you attempt a useless compilation, you will receive an error message.
7480 It is also useless to compile subunits because they are compiled as needed
7484 There are no order of compilation requirements: performing a
7485 compilation never obsoletes anything. The only way you can obsolete
7486 something and require recompilations is to modify one of the
7487 source files on which it depends.
7490 There is no library as such, apart from the ALI files
7491 (@pxref{The Ada Library Information Files}, for information on the format
7492 of these files). For now we find it convenient to create separate ALI files,
7493 but eventually the information therein may be incorporated into the object
7497 When you compile a unit, the source files for the specs of all units
7498 that it @code{with}'s, all its subunits, and the bodies of any generics it
7499 instantiates must be available (reachable by the search-paths mechanism
7500 described above), or you will receive a fatal error message.
7507 The following are some typical Ada compilation command line examples:
7510 @item $ gcc -c xyz.adb
7511 Compile body in file @file{xyz.adb} with all default options.
7514 @item $ gcc -c -O2 -gnata xyz-def.adb
7517 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7520 Compile the child unit package in file @file{xyz-def.adb} with extensive
7521 optimizations, and pragma @code{Assert}/@code{Debug} statements
7524 @item $ gcc -c -gnatc abc-def.adb
7525 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7529 @node Binding Using gnatbind
7530 @chapter Binding Using @code{gnatbind}
7534 * Running gnatbind::
7535 * Switches for gnatbind::
7536 * Command-Line Access::
7537 * Search Paths for gnatbind::
7538 * Examples of gnatbind Usage::
7542 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7543 to bind compiled GNAT objects.
7545 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7546 driver (see @ref{The GNAT Driver and Project Files}).
7548 The @code{gnatbind} program performs four separate functions:
7552 Checks that a program is consistent, in accordance with the rules in
7553 Chapter 10 of the Ada Reference Manual. In particular, error
7554 messages are generated if a program uses inconsistent versions of a
7558 Checks that an acceptable order of elaboration exists for the program
7559 and issues an error message if it cannot find an order of elaboration
7560 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7563 Generates a main program incorporating the given elaboration order.
7564 This program is a small Ada package (body and spec) that
7565 must be subsequently compiled
7566 using the GNAT compiler. The necessary compilation step is usually
7567 performed automatically by @command{gnatlink}. The two most important
7568 functions of this program
7569 are to call the elaboration routines of units in an appropriate order
7570 and to call the main program.
7573 Determines the set of object files required by the given main program.
7574 This information is output in the forms of comments in the generated program,
7575 to be read by the @command{gnatlink} utility used to link the Ada application.
7578 @node Running gnatbind
7579 @section Running @code{gnatbind}
7582 The form of the @code{gnatbind} command is
7585 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7589 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7590 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7591 package in two files whose names are
7592 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7593 For example, if given the
7594 parameter @file{hello.ali}, for a main program contained in file
7595 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7596 and @file{b~hello.adb}.
7598 When doing consistency checking, the binder takes into consideration
7599 any source files it can locate. For example, if the binder determines
7600 that the given main program requires the package @code{Pack}, whose
7602 file is @file{pack.ali} and whose corresponding source spec file is
7603 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7604 (using the same search path conventions as previously described for the
7605 @command{gcc} command). If it can locate this source file, it checks that
7607 or source checksums of the source and its references to in @file{ALI} files
7608 match. In other words, any @file{ALI} files that mentions this spec must have
7609 resulted from compiling this version of the source file (or in the case
7610 where the source checksums match, a version close enough that the
7611 difference does not matter).
7613 @cindex Source files, use by binder
7614 The effect of this consistency checking, which includes source files, is
7615 that the binder ensures that the program is consistent with the latest
7616 version of the source files that can be located at bind time. Editing a
7617 source file without compiling files that depend on the source file cause
7618 error messages to be generated by the binder.
7620 For example, suppose you have a main program @file{hello.adb} and a
7621 package @code{P}, from file @file{p.ads} and you perform the following
7626 Enter @code{gcc -c hello.adb} to compile the main program.
7629 Enter @code{gcc -c p.ads} to compile package @code{P}.
7632 Edit file @file{p.ads}.
7635 Enter @code{gnatbind hello}.
7639 At this point, the file @file{p.ali} contains an out-of-date time stamp
7640 because the file @file{p.ads} has been edited. The attempt at binding
7641 fails, and the binder generates the following error messages:
7644 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7645 error: "p.ads" has been modified and must be recompiled
7649 Now both files must be recompiled as indicated, and then the bind can
7650 succeed, generating a main program. You need not normally be concerned
7651 with the contents of this file, but for reference purposes a sample
7652 binder output file is given in @ref{Example of Binder Output File}.
7654 In most normal usage, the default mode of @command{gnatbind} which is to
7655 generate the main package in Ada, as described in the previous section.
7656 In particular, this means that any Ada programmer can read and understand
7657 the generated main program. It can also be debugged just like any other
7658 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7659 @command{gnatbind} and @command{gnatlink}.
7661 However for some purposes it may be convenient to generate the main
7662 program in C rather than Ada. This may for example be helpful when you
7663 are generating a mixed language program with the main program in C. The
7664 GNAT compiler itself is an example.
7665 The use of the @option{^-C^/BIND_FILE=C^} switch
7666 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7667 be generated in C (and compiled using the gnu C compiler).
7669 @node Switches for gnatbind
7670 @section Switches for @command{gnatbind}
7673 The following switches are available with @code{gnatbind}; details will
7674 be presented in subsequent sections.
7677 * Consistency-Checking Modes::
7678 * Binder Error Message Control::
7679 * Elaboration Control::
7681 * Binding with Non-Ada Main Programs::
7682 * Binding Programs with No Main Subprogram::
7689 @cindex @option{--version} @command{gnatbind}
7690 Display Copyright and version, then exit disregarding all other options.
7693 @cindex @option{--help} @command{gnatbind}
7694 If @option{--version} was not used, display usage, then exit disregarding
7698 @cindex @option{-a} @command{gnatbind}
7699 Indicates that, if supported by the platform, the adainit procedure should
7700 be treated as an initialisation routine by the linker (a constructor). This
7701 is intended to be used by the Project Manager to automatically initialize
7702 shared Stand-Alone Libraries.
7704 @item ^-aO^/OBJECT_SEARCH^
7705 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7706 Specify directory to be searched for ALI files.
7708 @item ^-aI^/SOURCE_SEARCH^
7709 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7710 Specify directory to be searched for source file.
7712 @item ^-A^/BIND_FILE=ADA^
7713 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7714 Generate binder program in Ada (default)
7716 @item ^-b^/REPORT_ERRORS=BRIEF^
7717 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7718 Generate brief messages to @file{stderr} even if verbose mode set.
7720 @item ^-c^/NOOUTPUT^
7721 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7722 Check only, no generation of binder output file.
7724 @item ^-C^/BIND_FILE=C^
7725 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7726 Generate binder program in C
7728 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7729 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7730 This switch can be used to change the default task stack size value
7731 to a specified size @var{nn}, which is expressed in bytes by default, or
7732 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7734 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7735 in effect, to completing all task specs with
7736 @smallexample @c ada
7737 pragma Storage_Size (nn);
7739 When they do not already have such a pragma.
7741 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7742 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7743 This switch can be used to change the default secondary stack size value
7744 to a specified size @var{nn}, which is expressed in bytes by default, or
7745 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7748 The secondary stack is used to deal with functions that return a variable
7749 sized result, for example a function returning an unconstrained
7750 String. There are two ways in which this secondary stack is allocated.
7752 For most targets, the secondary stack is growing on demand and is allocated
7753 as a chain of blocks in the heap. The -D option is not very
7754 relevant. It only give some control over the size of the allocated
7755 blocks (whose size is the minimum of the default secondary stack size value,
7756 and the actual size needed for the current allocation request).
7758 For certain targets, notably VxWorks 653,
7759 the secondary stack is allocated by carving off a fixed ratio chunk of the
7760 primary task stack. The -D option is used to define the
7761 size of the environment task's secondary stack.
7763 @item ^-e^/ELABORATION_DEPENDENCIES^
7764 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
7765 Output complete list of elaboration-order dependencies.
7767 @item ^-E^/STORE_TRACEBACKS^
7768 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
7769 Store tracebacks in exception occurrences when the target supports it.
7770 This is the default with the zero cost exception mechanism.
7772 @c The following may get moved to an appendix
7773 This option is currently supported on the following targets:
7774 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
7776 See also the packages @code{GNAT.Traceback} and
7777 @code{GNAT.Traceback.Symbolic} for more information.
7779 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
7780 @command{gcc} option.
7783 @item ^-F^/FORCE_ELABS_FLAGS^
7784 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
7785 Force the checks of elaboration flags. @command{gnatbind} does not normally
7786 generate checks of elaboration flags for the main executable, except when
7787 a Stand-Alone Library is used. However, there are cases when this cannot be
7788 detected by gnatbind. An example is importing an interface of a Stand-Alone
7789 Library through a pragma Import and only specifying through a linker switch
7790 this Stand-Alone Library. This switch is used to guarantee that elaboration
7791 flag checks are generated.
7794 @cindex @option{^-h^/HELP^} (@command{gnatbind})
7795 Output usage (help) information
7798 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7799 Specify directory to be searched for source and ALI files.
7801 @item ^-I-^/NOCURRENT_DIRECTORY^
7802 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
7803 Do not look for sources in the current directory where @code{gnatbind} was
7804 invoked, and do not look for ALI files in the directory containing the
7805 ALI file named in the @code{gnatbind} command line.
7807 @item ^-l^/ORDER_OF_ELABORATION^
7808 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7809 Output chosen elaboration order.
7811 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
7812 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7813 Bind the units for library building. In this case the adainit and
7814 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
7815 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
7816 ^@var{xxx}final^@var{XXX}FINAL^.
7817 Implies ^-n^/NOCOMPILE^.
7819 (@xref{GNAT and Libraries}, for more details.)
7822 On OpenVMS, these init and final procedures are exported in uppercase
7823 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7824 the init procedure will be "TOTOINIT" and the exported name of the final
7825 procedure will be "TOTOFINAL".
7828 @item ^-Mxyz^/RENAME_MAIN=xyz^
7829 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7830 Rename generated main program from main to xyz. This option is
7831 supported on cross environments only.
7833 @item ^-m^/ERROR_LIMIT=^@var{n}
7834 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7835 Limit number of detected errors or warnings to @var{n}, where @var{n} is
7836 in the range 1..999999. The default value if no switch is
7837 given is 9999. If the number of warnings reaches this limit, then a
7838 message is output and further warnings are suppressed, the bind
7839 continues in this case. If the number of errors reaches this
7840 limit, then a message is output and the bind is abandoned.
7841 A value of zero means that no limit is enforced. The equal
7845 Furthermore, under Windows, the sources pointed to by the libraries path
7846 set in the registry are not searched for.
7850 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7854 @cindex @option{-nostdinc} (@command{gnatbind})
7855 Do not look for sources in the system default directory.
7858 @cindex @option{-nostdlib} (@command{gnatbind})
7859 Do not look for library files in the system default directory.
7861 @item --RTS=@var{rts-path}
7862 @cindex @option{--RTS} (@code{gnatbind})
7863 Specifies the default location of the runtime library. Same meaning as the
7864 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
7866 @item ^-o ^/OUTPUT=^@var{file}
7867 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7868 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7869 Note that if this option is used, then linking must be done manually,
7870 gnatlink cannot be used.
7872 @item ^-O^/OBJECT_LIST^
7873 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7876 @item ^-p^/PESSIMISTIC_ELABORATION^
7877 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7878 Pessimistic (worst-case) elaboration order
7881 @cindex @option{^-R^-R^} (@command{gnatbind})
7882 Output closure source list.
7884 @item ^-s^/READ_SOURCES=ALL^
7885 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7886 Require all source files to be present.
7888 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7889 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7890 Specifies the value to be used when detecting uninitialized scalar
7891 objects with pragma Initialize_Scalars.
7892 The @var{xxx} ^string specified with the switch^option^ may be either
7894 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7895 @item ``@option{^lo^LOW^}'' for the lowest possible value
7896 @item ``@option{^hi^HIGH^}'' for the highest possible value
7897 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
7898 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
7901 In addition, you can specify @option{-Sev} to indicate that the value is
7902 to be set at run time. In this case, the program will look for an environment
7903 @cindex GNAT_INIT_SCALARS
7904 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
7905 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
7906 If no environment variable is found, or if it does not have a valid value,
7907 then the default is @option{in} (invalid values).
7911 @cindex @option{-static} (@code{gnatbind})
7912 Link against a static GNAT run time.
7915 @cindex @option{-shared} (@code{gnatbind})
7916 Link against a shared GNAT run time when available.
7919 @item ^-t^/NOTIME_STAMP_CHECK^
7920 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7921 Tolerate time stamp and other consistency errors
7923 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7924 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7925 Set the time slice value to @var{n} milliseconds. If the system supports
7926 the specification of a specific time slice value, then the indicated value
7927 is used. If the system does not support specific time slice values, but
7928 does support some general notion of round-robin scheduling, then any
7929 nonzero value will activate round-robin scheduling.
7931 A value of zero is treated specially. It turns off time
7932 slicing, and in addition, indicates to the tasking run time that the
7933 semantics should match as closely as possible the Annex D
7934 requirements of the Ada RM, and in particular sets the default
7935 scheduling policy to @code{FIFO_Within_Priorities}.
7937 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
7938 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
7939 Enable dynamic stack usage, with @var{n} results stored and displayed
7940 at program termination. A result is generated when a task
7941 terminates. Results that can't be stored are displayed on the fly, at
7942 task termination. This option is currently not supported on Itanium
7943 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
7945 @item ^-v^/REPORT_ERRORS=VERBOSE^
7946 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7947 Verbose mode. Write error messages, header, summary output to
7952 @cindex @option{-w} (@code{gnatbind})
7953 Warning mode (@var{x}=s/e for suppress/treat as error)
7957 @item /WARNINGS=NORMAL
7958 @cindex @option{/WARNINGS} (@code{gnatbind})
7959 Normal warnings mode. Warnings are issued but ignored
7961 @item /WARNINGS=SUPPRESS
7962 @cindex @option{/WARNINGS} (@code{gnatbind})
7963 All warning messages are suppressed
7965 @item /WARNINGS=ERROR
7966 @cindex @option{/WARNINGS} (@code{gnatbind})
7967 Warning messages are treated as fatal errors
7970 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7971 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7972 Override default wide character encoding for standard Text_IO files.
7974 @item ^-x^/READ_SOURCES=NONE^
7975 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7976 Exclude source files (check object consistency only).
7979 @item /READ_SOURCES=AVAILABLE
7980 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7981 Default mode, in which sources are checked for consistency only if
7985 @item ^-y^/ENABLE_LEAP_SECONDS^
7986 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
7987 Enable leap seconds support in @code{Ada.Calendar} and its children.
7989 @item ^-z^/ZERO_MAIN^
7990 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7996 You may obtain this listing of switches by running @code{gnatbind} with
8000 @node Consistency-Checking Modes
8001 @subsection Consistency-Checking Modes
8004 As described earlier, by default @code{gnatbind} checks
8005 that object files are consistent with one another and are consistent
8006 with any source files it can locate. The following switches control binder
8011 @item ^-s^/READ_SOURCES=ALL^
8012 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8013 Require source files to be present. In this mode, the binder must be
8014 able to locate all source files that are referenced, in order to check
8015 their consistency. In normal mode, if a source file cannot be located it
8016 is simply ignored. If you specify this switch, a missing source
8019 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8020 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8021 Override default wide character encoding for standard Text_IO files.
8022 Normally the default wide character encoding method used for standard
8023 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8024 the main source input (see description of switch
8025 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8026 use of this switch for the binder (which has the same set of
8027 possible arguments) overrides this default as specified.
8029 @item ^-x^/READ_SOURCES=NONE^
8030 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8031 Exclude source files. In this mode, the binder only checks that ALI
8032 files are consistent with one another. Source files are not accessed.
8033 The binder runs faster in this mode, and there is still a guarantee that
8034 the resulting program is self-consistent.
8035 If a source file has been edited since it was last compiled, and you
8036 specify this switch, the binder will not detect that the object
8037 file is out of date with respect to the source file. Note that this is the
8038 mode that is automatically used by @command{gnatmake} because in this
8039 case the checking against sources has already been performed by
8040 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8043 @item /READ_SOURCES=AVAILABLE
8044 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8045 This is the default mode in which source files are checked if they are
8046 available, and ignored if they are not available.
8050 @node Binder Error Message Control
8051 @subsection Binder Error Message Control
8054 The following switches provide control over the generation of error
8055 messages from the binder:
8059 @item ^-v^/REPORT_ERRORS=VERBOSE^
8060 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8061 Verbose mode. In the normal mode, brief error messages are generated to
8062 @file{stderr}. If this switch is present, a header is written
8063 to @file{stdout} and any error messages are directed to @file{stdout}.
8064 All that is written to @file{stderr} is a brief summary message.
8066 @item ^-b^/REPORT_ERRORS=BRIEF^
8067 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8068 Generate brief error messages to @file{stderr} even if verbose mode is
8069 specified. This is relevant only when used with the
8070 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8074 @cindex @option{-m} (@code{gnatbind})
8075 Limits the number of error messages to @var{n}, a decimal integer in the
8076 range 1-999. The binder terminates immediately if this limit is reached.
8079 @cindex @option{-M} (@code{gnatbind})
8080 Renames the generated main program from @code{main} to @code{xxx}.
8081 This is useful in the case of some cross-building environments, where
8082 the actual main program is separate from the one generated
8086 @item ^-ws^/WARNINGS=SUPPRESS^
8087 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8089 Suppress all warning messages.
8091 @item ^-we^/WARNINGS=ERROR^
8092 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8093 Treat any warning messages as fatal errors.
8096 @item /WARNINGS=NORMAL
8097 Standard mode with warnings generated, but warnings do not get treated
8101 @item ^-t^/NOTIME_STAMP_CHECK^
8102 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8103 @cindex Time stamp checks, in binder
8104 @cindex Binder consistency checks
8105 @cindex Consistency checks, in binder
8106 The binder performs a number of consistency checks including:
8110 Check that time stamps of a given source unit are consistent
8112 Check that checksums of a given source unit are consistent
8114 Check that consistent versions of @code{GNAT} were used for compilation
8116 Check consistency of configuration pragmas as required
8120 Normally failure of such checks, in accordance with the consistency
8121 requirements of the Ada Reference Manual, causes error messages to be
8122 generated which abort the binder and prevent the output of a binder
8123 file and subsequent link to obtain an executable.
8125 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8126 into warnings, so that
8127 binding and linking can continue to completion even in the presence of such
8128 errors. The result may be a failed link (due to missing symbols), or a
8129 non-functional executable which has undefined semantics.
8130 @emph{This means that
8131 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8135 @node Elaboration Control
8136 @subsection Elaboration Control
8139 The following switches provide additional control over the elaboration
8140 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8143 @item ^-p^/PESSIMISTIC_ELABORATION^
8144 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8145 Normally the binder attempts to choose an elaboration order that is
8146 likely to minimize the likelihood of an elaboration order error resulting
8147 in raising a @code{Program_Error} exception. This switch reverses the
8148 action of the binder, and requests that it deliberately choose an order
8149 that is likely to maximize the likelihood of an elaboration error.
8150 This is useful in ensuring portability and avoiding dependence on
8151 accidental fortuitous elaboration ordering.
8153 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8155 elaboration checking is used (@option{-gnatE} switch used for compilation).
8156 This is because in the default static elaboration mode, all necessary
8157 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8158 These implicit pragmas are still respected by the binder in
8159 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8160 safe elaboration order is assured.
8163 @node Output Control
8164 @subsection Output Control
8167 The following switches allow additional control over the output
8168 generated by the binder.
8173 @item ^-A^/BIND_FILE=ADA^
8174 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8175 Generate binder program in Ada (default). The binder program is named
8176 @file{b~@var{mainprog}.adb} by default. This can be changed with
8177 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8179 @item ^-c^/NOOUTPUT^
8180 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8181 Check only. Do not generate the binder output file. In this mode the
8182 binder performs all error checks but does not generate an output file.
8184 @item ^-C^/BIND_FILE=C^
8185 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8186 Generate binder program in C. The binder program is named
8187 @file{b_@var{mainprog}.c}.
8188 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8191 @item ^-e^/ELABORATION_DEPENDENCIES^
8192 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8193 Output complete list of elaboration-order dependencies, showing the
8194 reason for each dependency. This output can be rather extensive but may
8195 be useful in diagnosing problems with elaboration order. The output is
8196 written to @file{stdout}.
8199 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8200 Output usage information. The output is written to @file{stdout}.
8202 @item ^-K^/LINKER_OPTION_LIST^
8203 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8204 Output linker options to @file{stdout}. Includes library search paths,
8205 contents of pragmas Ident and Linker_Options, and libraries added
8208 @item ^-l^/ORDER_OF_ELABORATION^
8209 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8210 Output chosen elaboration order. The output is written to @file{stdout}.
8212 @item ^-O^/OBJECT_LIST^
8213 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8214 Output full names of all the object files that must be linked to provide
8215 the Ada component of the program. The output is written to @file{stdout}.
8216 This list includes the files explicitly supplied and referenced by the user
8217 as well as implicitly referenced run-time unit files. The latter are
8218 omitted if the corresponding units reside in shared libraries. The
8219 directory names for the run-time units depend on the system configuration.
8221 @item ^-o ^/OUTPUT=^@var{file}
8222 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8223 Set name of output file to @var{file} instead of the normal
8224 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8225 binder generated body filename. In C mode you would normally give
8226 @var{file} an extension of @file{.c} because it will be a C source program.
8227 Note that if this option is used, then linking must be done manually.
8228 It is not possible to use gnatlink in this case, since it cannot locate
8231 @item ^-r^/RESTRICTION_LIST^
8232 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8233 Generate list of @code{pragma Restrictions} that could be applied to
8234 the current unit. This is useful for code audit purposes, and also may
8235 be used to improve code generation in some cases.
8239 @node Binding with Non-Ada Main Programs
8240 @subsection Binding with Non-Ada Main Programs
8243 In our description so far we have assumed that the main
8244 program is in Ada, and that the task of the binder is to generate a
8245 corresponding function @code{main} that invokes this Ada main
8246 program. GNAT also supports the building of executable programs where
8247 the main program is not in Ada, but some of the called routines are
8248 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8249 The following switch is used in this situation:
8253 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8254 No main program. The main program is not in Ada.
8258 In this case, most of the functions of the binder are still required,
8259 but instead of generating a main program, the binder generates a file
8260 containing the following callable routines:
8265 You must call this routine to initialize the Ada part of the program by
8266 calling the necessary elaboration routines. A call to @code{adainit} is
8267 required before the first call to an Ada subprogram.
8269 Note that it is assumed that the basic execution environment must be setup
8270 to be appropriate for Ada execution at the point where the first Ada
8271 subprogram is called. In particular, if the Ada code will do any
8272 floating-point operations, then the FPU must be setup in an appropriate
8273 manner. For the case of the x86, for example, full precision mode is
8274 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8275 that the FPU is in the right state.
8279 You must call this routine to perform any library-level finalization
8280 required by the Ada subprograms. A call to @code{adafinal} is required
8281 after the last call to an Ada subprogram, and before the program
8286 If the @option{^-n^/NOMAIN^} switch
8287 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8288 @cindex Binder, multiple input files
8289 is given, more than one ALI file may appear on
8290 the command line for @code{gnatbind}. The normal @dfn{closure}
8291 calculation is performed for each of the specified units. Calculating
8292 the closure means finding out the set of units involved by tracing
8293 @code{with} references. The reason it is necessary to be able to
8294 specify more than one ALI file is that a given program may invoke two or
8295 more quite separate groups of Ada units.
8297 The binder takes the name of its output file from the last specified ALI
8298 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8299 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8300 The output is an Ada unit in source form that can
8301 be compiled with GNAT unless the -C switch is used in which case the
8302 output is a C source file, which must be compiled using the C compiler.
8303 This compilation occurs automatically as part of the @command{gnatlink}
8306 Currently the GNAT run time requires a FPU using 80 bits mode
8307 precision. Under targets where this is not the default it is required to
8308 call GNAT.Float_Control.Reset before using floating point numbers (this
8309 include float computation, float input and output) in the Ada code. A
8310 side effect is that this could be the wrong mode for the foreign code
8311 where floating point computation could be broken after this call.
8313 @node Binding Programs with No Main Subprogram
8314 @subsection Binding Programs with No Main Subprogram
8317 It is possible to have an Ada program which does not have a main
8318 subprogram. This program will call the elaboration routines of all the
8319 packages, then the finalization routines.
8321 The following switch is used to bind programs organized in this manner:
8324 @item ^-z^/ZERO_MAIN^
8325 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8326 Normally the binder checks that the unit name given on the command line
8327 corresponds to a suitable main subprogram. When this switch is used,
8328 a list of ALI files can be given, and the execution of the program
8329 consists of elaboration of these units in an appropriate order. Note
8330 that the default wide character encoding method for standard Text_IO
8331 files is always set to Brackets if this switch is set (you can use
8333 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8336 @node Command-Line Access
8337 @section Command-Line Access
8340 The package @code{Ada.Command_Line} provides access to the command-line
8341 arguments and program name. In order for this interface to operate
8342 correctly, the two variables
8354 are declared in one of the GNAT library routines. These variables must
8355 be set from the actual @code{argc} and @code{argv} values passed to the
8356 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8357 generates the C main program to automatically set these variables.
8358 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8359 set these variables. If they are not set, the procedures in
8360 @code{Ada.Command_Line} will not be available, and any attempt to use
8361 them will raise @code{Constraint_Error}. If command line access is
8362 required, your main program must set @code{gnat_argc} and
8363 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8366 @node Search Paths for gnatbind
8367 @section Search Paths for @code{gnatbind}
8370 The binder takes the name of an ALI file as its argument and needs to
8371 locate source files as well as other ALI files to verify object consistency.
8373 For source files, it follows exactly the same search rules as @command{gcc}
8374 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8375 directories searched are:
8379 The directory containing the ALI file named in the command line, unless
8380 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8383 All directories specified by @option{^-I^/SEARCH^}
8384 switches on the @code{gnatbind}
8385 command line, in the order given.
8388 @findex ADA_PRJ_OBJECTS_FILE
8389 Each of the directories listed in the text file whose name is given
8390 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8393 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8394 driver when project files are used. It should not normally be set
8398 @findex ADA_OBJECTS_PATH
8399 Each of the directories listed in the value of the
8400 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8402 Construct this value
8403 exactly as the @env{PATH} environment variable: a list of directory
8404 names separated by colons (semicolons when working with the NT version
8408 Normally, define this value as a logical name containing a comma separated
8409 list of directory names.
8411 This variable can also be defined by means of an environment string
8412 (an argument to the HP C exec* set of functions).
8416 DEFINE ANOTHER_PATH FOO:[BAG]
8417 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8420 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8421 first, followed by the standard Ada
8422 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8423 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8424 (Text_IO, Sequential_IO, etc)
8425 instead of the standard Ada packages. Thus, in order to get the standard Ada
8426 packages by default, ADA_OBJECTS_PATH must be redefined.
8430 The content of the @file{ada_object_path} file which is part of the GNAT
8431 installation tree and is used to store standard libraries such as the
8432 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8435 @ref{Installing a library}
8440 In the binder the switch @option{^-I^/SEARCH^}
8441 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8442 is used to specify both source and
8443 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8444 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8445 instead if you want to specify
8446 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8447 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8448 if you want to specify library paths
8449 only. This means that for the binder
8450 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8451 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8452 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8453 The binder generates the bind file (a C language source file) in the
8454 current working directory.
8460 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8461 children make up the GNAT Run-Time Library, together with the package
8462 GNAT and its children, which contain a set of useful additional
8463 library functions provided by GNAT. The sources for these units are
8464 needed by the compiler and are kept together in one directory. The ALI
8465 files and object files generated by compiling the RTL are needed by the
8466 binder and the linker and are kept together in one directory, typically
8467 different from the directory containing the sources. In a normal
8468 installation, you need not specify these directory names when compiling
8469 or binding. Either the environment variables or the built-in defaults
8470 cause these files to be found.
8472 Besides simplifying access to the RTL, a major use of search paths is
8473 in compiling sources from multiple directories. This can make
8474 development environments much more flexible.
8476 @node Examples of gnatbind Usage
8477 @section Examples of @code{gnatbind} Usage
8480 This section contains a number of examples of using the GNAT binding
8481 utility @code{gnatbind}.
8484 @item gnatbind hello
8485 The main program @code{Hello} (source program in @file{hello.adb}) is
8486 bound using the standard switch settings. The generated main program is
8487 @file{b~hello.adb}. This is the normal, default use of the binder.
8490 @item gnatbind hello -o mainprog.adb
8493 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8495 The main program @code{Hello} (source program in @file{hello.adb}) is
8496 bound using the standard switch settings. The generated main program is
8497 @file{mainprog.adb} with the associated spec in
8498 @file{mainprog.ads}. Note that you must specify the body here not the
8499 spec, in the case where the output is in Ada. Note that if this option
8500 is used, then linking must be done manually, since gnatlink will not
8501 be able to find the generated file.
8504 @item gnatbind main -C -o mainprog.c -x
8507 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8509 The main program @code{Main} (source program in
8510 @file{main.adb}) is bound, excluding source files from the
8511 consistency checking, generating
8512 the file @file{mainprog.c}.
8515 @item gnatbind -x main_program -C -o mainprog.c
8516 This command is exactly the same as the previous example. Switches may
8517 appear anywhere in the command line, and single letter switches may be
8518 combined into a single switch.
8522 @item gnatbind -n math dbase -C -o ada-control.c
8525 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8527 The main program is in a language other than Ada, but calls to
8528 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8529 to @code{gnatbind} generates the file @file{ada-control.c} containing
8530 the @code{adainit} and @code{adafinal} routines to be called before and
8531 after accessing the Ada units.
8534 @c ------------------------------------
8535 @node Linking Using gnatlink
8536 @chapter Linking Using @command{gnatlink}
8537 @c ------------------------------------
8541 This chapter discusses @command{gnatlink}, a tool that links
8542 an Ada program and builds an executable file. This utility
8543 invokes the system linker ^(via the @command{gcc} command)^^
8544 with a correct list of object files and library references.
8545 @command{gnatlink} automatically determines the list of files and
8546 references for the Ada part of a program. It uses the binder file
8547 generated by the @command{gnatbind} to determine this list.
8549 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8550 driver (see @ref{The GNAT Driver and Project Files}).
8553 * Running gnatlink::
8554 * Switches for gnatlink::
8557 @node Running gnatlink
8558 @section Running @command{gnatlink}
8561 The form of the @command{gnatlink} command is
8564 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8565 @ovar{non-Ada objects} @ovar{linker options}
8569 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8571 or linker options) may be in any order, provided that no non-Ada object may
8572 be mistaken for a main @file{ALI} file.
8573 Any file name @file{F} without the @file{.ali}
8574 extension will be taken as the main @file{ALI} file if a file exists
8575 whose name is the concatenation of @file{F} and @file{.ali}.
8578 @file{@var{mainprog}.ali} references the ALI file of the main program.
8579 The @file{.ali} extension of this file can be omitted. From this
8580 reference, @command{gnatlink} locates the corresponding binder file
8581 @file{b~@var{mainprog}.adb} and, using the information in this file along
8582 with the list of non-Ada objects and linker options, constructs a
8583 linker command file to create the executable.
8585 The arguments other than the @command{gnatlink} switches and the main
8586 @file{ALI} file are passed to the linker uninterpreted.
8587 They typically include the names of
8588 object files for units written in other languages than Ada and any library
8589 references required to resolve references in any of these foreign language
8590 units, or in @code{Import} pragmas in any Ada units.
8592 @var{linker options} is an optional list of linker specific
8594 The default linker called by gnatlink is @command{gcc} which in
8595 turn calls the appropriate system linker.
8596 Standard options for the linker such as @option{-lmy_lib} or
8597 @option{-Ldir} can be added as is.
8598 For options that are not recognized by
8599 @command{gcc} as linker options, use the @command{gcc} switches
8600 @option{-Xlinker} or @option{-Wl,}.
8601 Refer to the GCC documentation for
8602 details. Here is an example showing how to generate a linker map:
8605 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8608 Using @var{linker options} it is possible to set the program stack and
8611 See @ref{Setting Stack Size from gnatlink} and
8612 @ref{Setting Heap Size from gnatlink}.
8615 @command{gnatlink} determines the list of objects required by the Ada
8616 program and prepends them to the list of objects passed to the linker.
8617 @command{gnatlink} also gathers any arguments set by the use of
8618 @code{pragma Linker_Options} and adds them to the list of arguments
8619 presented to the linker.
8622 @command{gnatlink} accepts the following types of extra files on the command
8623 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8624 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8625 handled according to their extension.
8628 @node Switches for gnatlink
8629 @section Switches for @command{gnatlink}
8632 The following switches are available with the @command{gnatlink} utility:
8638 @cindex @option{--version} @command{gnatlink}
8639 Display Copyright and version, then exit disregarding all other options.
8642 @cindex @option{--help} @command{gnatlink}
8643 If @option{--version} was not used, display usage, then exit disregarding
8646 @item ^-A^/BIND_FILE=ADA^
8647 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8648 The binder has generated code in Ada. This is the default.
8650 @item ^-C^/BIND_FILE=C^
8651 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8652 If instead of generating a file in Ada, the binder has generated one in
8653 C, then the linker needs to know about it. Use this switch to signal
8654 to @command{gnatlink} that the binder has generated C code rather than
8657 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8658 @cindex Command line length
8659 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8660 On some targets, the command line length is limited, and @command{gnatlink}
8661 will generate a separate file for the linker if the list of object files
8663 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8664 to be generated even if
8665 the limit is not exceeded. This is useful in some cases to deal with
8666 special situations where the command line length is exceeded.
8669 @cindex Debugging information, including
8670 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8671 The option to include debugging information causes the Ada bind file (in
8672 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8673 @option{^-g^/DEBUG^}.
8674 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8675 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8676 Without @option{^-g^/DEBUG^}, the binder removes these files by
8677 default. The same procedure apply if a C bind file was generated using
8678 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8679 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8681 @item ^-n^/NOCOMPILE^
8682 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8683 Do not compile the file generated by the binder. This may be used when
8684 a link is rerun with different options, but there is no need to recompile
8688 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8689 Causes additional information to be output, including a full list of the
8690 included object files. This switch option is most useful when you want
8691 to see what set of object files are being used in the link step.
8693 @item ^-v -v^/VERBOSE/VERBOSE^
8694 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8695 Very verbose mode. Requests that the compiler operate in verbose mode when
8696 it compiles the binder file, and that the system linker run in verbose mode.
8698 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8699 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8700 @var{exec-name} specifies an alternate name for the generated
8701 executable program. If this switch is omitted, the executable has the same
8702 name as the main unit. For example, @code{gnatlink try.ali} creates
8703 an executable called @file{^try^TRY.EXE^}.
8706 @item -b @var{target}
8707 @cindex @option{-b} (@command{gnatlink})
8708 Compile your program to run on @var{target}, which is the name of a
8709 system configuration. You must have a GNAT cross-compiler built if
8710 @var{target} is not the same as your host system.
8713 @cindex @option{-B} (@command{gnatlink})
8714 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8715 from @var{dir} instead of the default location. Only use this switch
8716 when multiple versions of the GNAT compiler are available.
8717 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8718 for further details. You would normally use the @option{-b} or
8719 @option{-V} switch instead.
8721 @item --GCC=@var{compiler_name}
8722 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8723 Program used for compiling the binder file. The default is
8724 @command{gcc}. You need to use quotes around @var{compiler_name} if
8725 @code{compiler_name} contains spaces or other separator characters.
8726 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8727 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8728 inserted after your command name. Thus in the above example the compiler
8729 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8730 A limitation of this syntax is that the name and path name of the executable
8731 itself must not include any embedded spaces. If the compiler executable is
8732 different from the default one (gcc or <prefix>-gcc), then the back-end
8733 switches in the ALI file are not used to compile the binder generated source.
8734 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8735 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8736 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8737 is taken into account. However, all the additional switches are also taken
8739 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8740 @option{--GCC="bar -x -y -z -t"}.
8742 @item --LINK=@var{name}
8743 @cindex @option{--LINK=} (@command{gnatlink})
8744 @var{name} is the name of the linker to be invoked. This is especially
8745 useful in mixed language programs since languages such as C++ require
8746 their own linker to be used. When this switch is omitted, the default
8747 name for the linker is @command{gcc}. When this switch is used, the
8748 specified linker is called instead of @command{gcc} with exactly the same
8749 parameters that would have been passed to @command{gcc} so if the desired
8750 linker requires different parameters it is necessary to use a wrapper
8751 script that massages the parameters before invoking the real linker. It
8752 may be useful to control the exact invocation by using the verbose
8758 @item /DEBUG=TRACEBACK
8759 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
8760 This qualifier causes sufficient information to be included in the
8761 executable file to allow a traceback, but does not include the full
8762 symbol information needed by the debugger.
8764 @item /IDENTIFICATION="<string>"
8765 @code{"<string>"} specifies the string to be stored in the image file
8766 identification field in the image header.
8767 It overrides any pragma @code{Ident} specified string.
8769 @item /NOINHIBIT-EXEC
8770 Generate the executable file even if there are linker warnings.
8772 @item /NOSTART_FILES
8773 Don't link in the object file containing the ``main'' transfer address.
8774 Used when linking with a foreign language main program compiled with an
8778 Prefer linking with object libraries over sharable images, even without
8784 @node The GNAT Make Program gnatmake
8785 @chapter The GNAT Make Program @command{gnatmake}
8789 * Running gnatmake::
8790 * Switches for gnatmake::
8791 * Mode Switches for gnatmake::
8792 * Notes on the Command Line::
8793 * How gnatmake Works::
8794 * Examples of gnatmake Usage::
8797 A typical development cycle when working on an Ada program consists of
8798 the following steps:
8802 Edit some sources to fix bugs.
8808 Compile all sources affected.
8818 The third step can be tricky, because not only do the modified files
8819 @cindex Dependency rules
8820 have to be compiled, but any files depending on these files must also be
8821 recompiled. The dependency rules in Ada can be quite complex, especially
8822 in the presence of overloading, @code{use} clauses, generics and inlined
8825 @command{gnatmake} automatically takes care of the third and fourth steps
8826 of this process. It determines which sources need to be compiled,
8827 compiles them, and binds and links the resulting object files.
8829 Unlike some other Ada make programs, the dependencies are always
8830 accurately recomputed from the new sources. The source based approach of
8831 the GNAT compilation model makes this possible. This means that if
8832 changes to the source program cause corresponding changes in
8833 dependencies, they will always be tracked exactly correctly by
8836 @node Running gnatmake
8837 @section Running @command{gnatmake}
8840 The usual form of the @command{gnatmake} command is
8843 $ gnatmake @ovar{switches} @var{file_name}
8844 @ovar{file_names} @ovar{mode_switches}
8848 The only required argument is one @var{file_name}, which specifies
8849 a compilation unit that is a main program. Several @var{file_names} can be
8850 specified: this will result in several executables being built.
8851 If @code{switches} are present, they can be placed before the first
8852 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8853 If @var{mode_switches} are present, they must always be placed after
8854 the last @var{file_name} and all @code{switches}.
8856 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
8857 extension may be omitted from the @var{file_name} arguments. However, if
8858 you are using non-standard extensions, then it is required that the
8859 extension be given. A relative or absolute directory path can be
8860 specified in a @var{file_name}, in which case, the input source file will
8861 be searched for in the specified directory only. Otherwise, the input
8862 source file will first be searched in the directory where
8863 @command{gnatmake} was invoked and if it is not found, it will be search on
8864 the source path of the compiler as described in
8865 @ref{Search Paths and the Run-Time Library (RTL)}.
8867 All @command{gnatmake} output (except when you specify
8868 @option{^-M^/DEPENDENCIES_LIST^}) is to
8869 @file{stderr}. The output produced by the
8870 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8873 @node Switches for gnatmake
8874 @section Switches for @command{gnatmake}
8877 You may specify any of the following switches to @command{gnatmake}:
8883 @cindex @option{--version} @command{gnatmake}
8884 Display Copyright and version, then exit disregarding all other options.
8887 @cindex @option{--help} @command{gnatmake}
8888 If @option{--version} was not used, display usage, then exit disregarding
8892 @item --GCC=@var{compiler_name}
8893 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
8894 Program used for compiling. The default is `@command{gcc}'. You need to use
8895 quotes around @var{compiler_name} if @code{compiler_name} contains
8896 spaces or other separator characters. As an example @option{--GCC="foo -x
8897 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
8898 compiler. A limitation of this syntax is that the name and path name of
8899 the executable itself must not include any embedded spaces. Note that
8900 switch @option{-c} is always inserted after your command name. Thus in the
8901 above example the compiler command that will be used by @command{gnatmake}
8902 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
8903 used, only the last @var{compiler_name} is taken into account. However,
8904 all the additional switches are also taken into account. Thus,
8905 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8906 @option{--GCC="bar -x -y -z -t"}.
8908 @item --GNATBIND=@var{binder_name}
8909 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
8910 Program used for binding. The default is `@code{gnatbind}'. You need to
8911 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8912 or other separator characters. As an example @option{--GNATBIND="bar -x
8913 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
8914 binder. Binder switches that are normally appended by @command{gnatmake}
8915 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8916 A limitation of this syntax is that the name and path name of the executable
8917 itself must not include any embedded spaces.
8919 @item --GNATLINK=@var{linker_name}
8920 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
8921 Program used for linking. The default is `@command{gnatlink}'. You need to
8922 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8923 or other separator characters. As an example @option{--GNATLINK="lan -x
8924 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
8925 linker. Linker switches that are normally appended by @command{gnatmake} to
8926 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
8927 A limitation of this syntax is that the name and path name of the executable
8928 itself must not include any embedded spaces.
8932 @item ^-a^/ALL_FILES^
8933 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
8934 Consider all files in the make process, even the GNAT internal system
8935 files (for example, the predefined Ada library files), as well as any
8936 locked files. Locked files are files whose ALI file is write-protected.
8938 @command{gnatmake} does not check these files,
8939 because the assumption is that the GNAT internal files are properly up
8940 to date, and also that any write protected ALI files have been properly
8941 installed. Note that if there is an installation problem, such that one
8942 of these files is not up to date, it will be properly caught by the
8944 You may have to specify this switch if you are working on GNAT
8945 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8946 in conjunction with @option{^-f^/FORCE_COMPILE^}
8947 if you need to recompile an entire application,
8948 including run-time files, using special configuration pragmas,
8949 such as a @code{Normalize_Scalars} pragma.
8952 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8955 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8958 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8961 @item ^-b^/ACTIONS=BIND^
8962 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
8963 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8964 compilation and binding, but no link.
8965 Can be combined with @option{^-l^/ACTIONS=LINK^}
8966 to do binding and linking. When not combined with
8967 @option{^-c^/ACTIONS=COMPILE^}
8968 all the units in the closure of the main program must have been previously
8969 compiled and must be up to date. The root unit specified by @var{file_name}
8970 may be given without extension, with the source extension or, if no GNAT
8971 Project File is specified, with the ALI file extension.
8973 @item ^-c^/ACTIONS=COMPILE^
8974 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
8975 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8976 is also specified. Do not perform linking, except if both
8977 @option{^-b^/ACTIONS=BIND^} and
8978 @option{^-l^/ACTIONS=LINK^} are also specified.
8979 If the root unit specified by @var{file_name} is not a main unit, this is the
8980 default. Otherwise @command{gnatmake} will attempt binding and linking
8981 unless all objects are up to date and the executable is more recent than
8985 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
8986 Use a temporary mapping file. A mapping file is a way to communicate to the
8987 compiler two mappings: from unit names to file names (without any directory
8988 information) and from file names to path names (with full directory
8989 information). These mappings are used by the compiler to short-circuit the path
8990 search. When @command{gnatmake} is invoked with this switch, it will create
8991 a temporary mapping file, initially populated by the project manager,
8992 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8993 Each invocation of the compiler will add the newly accessed sources to the
8994 mapping file. This will improve the source search during the next invocation
8997 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8998 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
8999 Use a specific mapping file. The file, specified as a path name (absolute or
9000 relative) by this switch, should already exist, otherwise the switch is
9001 ineffective. The specified mapping file will be communicated to the compiler.
9002 This switch is not compatible with a project file
9003 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9004 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9006 @item ^-d^/DISPLAY_PROGRESS^
9007 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9008 Display progress for each source, up to date or not, as a single line
9011 completed x out of y (zz%)
9014 If the file needs to be compiled this is displayed after the invocation of
9015 the compiler. These lines are displayed even in quiet output mode.
9017 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9018 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9019 Put all object files and ALI file in directory @var{dir}.
9020 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9021 and ALI files go in the current working directory.
9023 This switch cannot be used when using a project file.
9027 @cindex @option{-eL} (@command{gnatmake})
9028 Follow all symbolic links when processing project files.
9031 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9032 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9033 Output the commands for the compiler, the binder and the linker
9034 on ^standard output^SYS$OUTPUT^,
9035 instead of ^standard error^SYS$ERROR^.
9037 @item ^-f^/FORCE_COMPILE^
9038 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9039 Force recompilations. Recompile all sources, even though some object
9040 files may be up to date, but don't recompile predefined or GNAT internal
9041 files or locked files (files with a write-protected ALI file),
9042 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9044 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9045 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9046 When using project files, if some errors or warnings are detected during
9047 parsing and verbose mode is not in effect (no use of switch
9048 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9049 file, rather than its simple file name.
9052 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9053 Enable debugging. This switch is simply passed to the compiler and to the
9056 @item ^-i^/IN_PLACE^
9057 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9058 In normal mode, @command{gnatmake} compiles all object files and ALI files
9059 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9060 then instead object files and ALI files that already exist are overwritten
9061 in place. This means that once a large project is organized into separate
9062 directories in the desired manner, then @command{gnatmake} will automatically
9063 maintain and update this organization. If no ALI files are found on the
9064 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9065 the new object and ALI files are created in the
9066 directory containing the source being compiled. If another organization
9067 is desired, where objects and sources are kept in different directories,
9068 a useful technique is to create dummy ALI files in the desired directories.
9069 When detecting such a dummy file, @command{gnatmake} will be forced to
9070 recompile the corresponding source file, and it will be put the resulting
9071 object and ALI files in the directory where it found the dummy file.
9073 @item ^-j^/PROCESSES=^@var{n}
9074 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9075 @cindex Parallel make
9076 Use @var{n} processes to carry out the (re)compilations. On a
9077 multiprocessor machine compilations will occur in parallel. In the
9078 event of compilation errors, messages from various compilations might
9079 get interspersed (but @command{gnatmake} will give you the full ordered
9080 list of failing compiles at the end). If this is problematic, rerun
9081 the make process with n set to 1 to get a clean list of messages.
9083 @item ^-k^/CONTINUE_ON_ERROR^
9084 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9085 Keep going. Continue as much as possible after a compilation error. To
9086 ease the programmer's task in case of compilation errors, the list of
9087 sources for which the compile fails is given when @command{gnatmake}
9090 If @command{gnatmake} is invoked with several @file{file_names} and with this
9091 switch, if there are compilation errors when building an executable,
9092 @command{gnatmake} will not attempt to build the following executables.
9094 @item ^-l^/ACTIONS=LINK^
9095 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9096 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9097 and linking. Linking will not be performed if combined with
9098 @option{^-c^/ACTIONS=COMPILE^}
9099 but not with @option{^-b^/ACTIONS=BIND^}.
9100 When not combined with @option{^-b^/ACTIONS=BIND^}
9101 all the units in the closure of the main program must have been previously
9102 compiled and must be up to date, and the main program needs to have been bound.
9103 The root unit specified by @var{file_name}
9104 may be given without extension, with the source extension or, if no GNAT
9105 Project File is specified, with the ALI file extension.
9107 @item ^-m^/MINIMAL_RECOMPILATION^
9108 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9109 Specify that the minimum necessary amount of recompilations
9110 be performed. In this mode @command{gnatmake} ignores time
9111 stamp differences when the only
9112 modifications to a source file consist in adding/removing comments,
9113 empty lines, spaces or tabs. This means that if you have changed the
9114 comments in a source file or have simply reformatted it, using this
9115 switch will tell @command{gnatmake} not to recompile files that depend on it
9116 (provided other sources on which these files depend have undergone no
9117 semantic modifications). Note that the debugging information may be
9118 out of date with respect to the sources if the @option{-m} switch causes
9119 a compilation to be switched, so the use of this switch represents a
9120 trade-off between compilation time and accurate debugging information.
9122 @item ^-M^/DEPENDENCIES_LIST^
9123 @cindex Dependencies, producing list
9124 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9125 Check if all objects are up to date. If they are, output the object
9126 dependences to @file{stdout} in a form that can be directly exploited in
9127 a @file{Makefile}. By default, each source file is prefixed with its
9128 (relative or absolute) directory name. This name is whatever you
9129 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9130 and @option{^-I^/SEARCH^} switches. If you use
9131 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9132 @option{^-q^/QUIET^}
9133 (see below), only the source file names,
9134 without relative paths, are output. If you just specify the
9135 @option{^-M^/DEPENDENCIES_LIST^}
9136 switch, dependencies of the GNAT internal system files are omitted. This
9137 is typically what you want. If you also specify
9138 the @option{^-a^/ALL_FILES^} switch,
9139 dependencies of the GNAT internal files are also listed. Note that
9140 dependencies of the objects in external Ada libraries (see switch
9141 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9144 @item ^-n^/DO_OBJECT_CHECK^
9145 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9146 Don't compile, bind, or link. Checks if all objects are up to date.
9147 If they are not, the full name of the first file that needs to be
9148 recompiled is printed.
9149 Repeated use of this option, followed by compiling the indicated source
9150 file, will eventually result in recompiling all required units.
9152 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9153 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9154 Output executable name. The name of the final executable program will be
9155 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9156 name for the executable will be the name of the input file in appropriate form
9157 for an executable file on the host system.
9159 This switch cannot be used when invoking @command{gnatmake} with several
9162 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9163 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9164 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9165 automatically missing object directories, library directories and exec
9168 @item ^-P^/PROJECT_FILE=^@var{project}
9169 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9170 Use project file @var{project}. Only one such switch can be used.
9171 @xref{gnatmake and Project Files}.
9174 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9175 Quiet. When this flag is not set, the commands carried out by
9176 @command{gnatmake} are displayed.
9178 @item ^-s^/SWITCH_CHECK/^
9179 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9180 Recompile if compiler switches have changed since last compilation.
9181 All compiler switches but -I and -o are taken into account in the
9183 orders between different ``first letter'' switches are ignored, but
9184 orders between same switches are taken into account. For example,
9185 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9186 is equivalent to @option{-O -g}.
9188 This switch is recommended when Integrated Preprocessing is used.
9191 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9192 Unique. Recompile at most the main files. It implies -c. Combined with
9193 -f, it is equivalent to calling the compiler directly. Note that using
9194 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9195 (@pxref{Project Files and Main Subprograms}).
9197 @item ^-U^/ALL_PROJECTS^
9198 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9199 When used without a project file or with one or several mains on the command
9200 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9201 on the command line, all sources of all project files are checked and compiled
9202 if not up to date, and libraries are rebuilt, if necessary.
9205 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9206 Verbose. Display the reason for all recompilations @command{gnatmake}
9207 decides are necessary, with the highest verbosity level.
9209 @item ^-vl^/LOW_VERBOSITY^
9210 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9211 Verbosity level Low. Display fewer lines than in verbosity Medium.
9213 @item ^-vm^/MEDIUM_VERBOSITY^
9214 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9215 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9217 @item ^-vh^/HIGH_VERBOSITY^
9218 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9219 Verbosity level High. Equivalent to ^-v^/REASONS^.
9221 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9222 Indicate the verbosity of the parsing of GNAT project files.
9223 @xref{Switches Related to Project Files}.
9225 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9226 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9227 Indicate that sources that are not part of any Project File may be compiled.
9228 Normally, when using Project Files, only sources that are part of a Project
9229 File may be compile. When this switch is used, a source outside of all Project
9230 Files may be compiled. The ALI file and the object file will be put in the
9231 object directory of the main Project. The compilation switches used will only
9232 be those specified on the command line. Even when
9233 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9234 command line need to be sources of a project file.
9236 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9237 Indicate that external variable @var{name} has the value @var{value}.
9238 The Project Manager will use this value for occurrences of
9239 @code{external(name)} when parsing the project file.
9240 @xref{Switches Related to Project Files}.
9243 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9244 No main subprogram. Bind and link the program even if the unit name
9245 given on the command line is a package name. The resulting executable
9246 will execute the elaboration routines of the package and its closure,
9247 then the finalization routines.
9252 @item @command{gcc} @asis{switches}
9254 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9255 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9258 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9259 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9260 automatically treated as a compiler switch, and passed on to all
9261 compilations that are carried out.
9266 Source and library search path switches:
9270 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9271 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9272 When looking for source files also look in directory @var{dir}.
9273 The order in which source files search is undertaken is
9274 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9276 @item ^-aL^/SKIP_MISSING=^@var{dir}
9277 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9278 Consider @var{dir} as being an externally provided Ada library.
9279 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9280 files have been located in directory @var{dir}. This allows you to have
9281 missing bodies for the units in @var{dir} and to ignore out of date bodies
9282 for the same units. You still need to specify
9283 the location of the specs for these units by using the switches
9284 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9285 or @option{^-I^/SEARCH=^@var{dir}}.
9286 Note: this switch is provided for compatibility with previous versions
9287 of @command{gnatmake}. The easier method of causing standard libraries
9288 to be excluded from consideration is to write-protect the corresponding
9291 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9292 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9293 When searching for library and object files, look in directory
9294 @var{dir}. The order in which library files are searched is described in
9295 @ref{Search Paths for gnatbind}.
9297 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9298 @cindex Search paths, for @command{gnatmake}
9299 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9300 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9301 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9303 @item ^-I^/SEARCH=^@var{dir}
9304 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9305 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9306 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9308 @item ^-I-^/NOCURRENT_DIRECTORY^
9309 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9310 @cindex Source files, suppressing search
9311 Do not look for source files in the directory containing the source
9312 file named in the command line.
9313 Do not look for ALI or object files in the directory
9314 where @command{gnatmake} was invoked.
9316 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9317 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9318 @cindex Linker libraries
9319 Add directory @var{dir} to the list of directories in which the linker
9320 will search for libraries. This is equivalent to
9321 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9323 Furthermore, under Windows, the sources pointed to by the libraries path
9324 set in the registry are not searched for.
9328 @cindex @option{-nostdinc} (@command{gnatmake})
9329 Do not look for source files in the system default directory.
9332 @cindex @option{-nostdlib} (@command{gnatmake})
9333 Do not look for library files in the system default directory.
9335 @item --RTS=@var{rts-path}
9336 @cindex @option{--RTS} (@command{gnatmake})
9337 Specifies the default location of the runtime library. GNAT looks for the
9339 in the following directories, and stops as soon as a valid runtime is found
9340 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9341 @file{ada_object_path} present):
9344 @item <current directory>/$rts_path
9346 @item <default-search-dir>/$rts_path
9348 @item <default-search-dir>/rts-$rts_path
9352 The selected path is handled like a normal RTS path.
9356 @node Mode Switches for gnatmake
9357 @section Mode Switches for @command{gnatmake}
9360 The mode switches (referred to as @code{mode_switches}) allow the
9361 inclusion of switches that are to be passed to the compiler itself, the
9362 binder or the linker. The effect of a mode switch is to cause all
9363 subsequent switches up to the end of the switch list, or up to the next
9364 mode switch, to be interpreted as switches to be passed on to the
9365 designated component of GNAT.
9369 @item -cargs @var{switches}
9370 @cindex @option{-cargs} (@command{gnatmake})
9371 Compiler switches. Here @var{switches} is a list of switches
9372 that are valid switches for @command{gcc}. They will be passed on to
9373 all compile steps performed by @command{gnatmake}.
9375 @item -bargs @var{switches}
9376 @cindex @option{-bargs} (@command{gnatmake})
9377 Binder switches. Here @var{switches} is a list of switches
9378 that are valid switches for @code{gnatbind}. They will be passed on to
9379 all bind steps performed by @command{gnatmake}.
9381 @item -largs @var{switches}
9382 @cindex @option{-largs} (@command{gnatmake})
9383 Linker switches. Here @var{switches} is a list of switches
9384 that are valid switches for @command{gnatlink}. They will be passed on to
9385 all link steps performed by @command{gnatmake}.
9387 @item -margs @var{switches}
9388 @cindex @option{-margs} (@command{gnatmake})
9389 Make switches. The switches are directly interpreted by @command{gnatmake},
9390 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9394 @node Notes on the Command Line
9395 @section Notes on the Command Line
9398 This section contains some additional useful notes on the operation
9399 of the @command{gnatmake} command.
9403 @cindex Recompilation, by @command{gnatmake}
9404 If @command{gnatmake} finds no ALI files, it recompiles the main program
9405 and all other units required by the main program.
9406 This means that @command{gnatmake}
9407 can be used for the initial compile, as well as during subsequent steps of
9408 the development cycle.
9411 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9412 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9413 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9417 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9418 is used to specify both source and
9419 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9420 instead if you just want to specify
9421 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9422 if you want to specify library paths
9426 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9427 This may conveniently be used to exclude standard libraries from
9428 consideration and in particular it means that the use of the
9429 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9430 unless @option{^-a^/ALL_FILES^} is also specified.
9433 @command{gnatmake} has been designed to make the use of Ada libraries
9434 particularly convenient. Assume you have an Ada library organized
9435 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9436 of your Ada compilation units,
9437 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9438 specs of these units, but no bodies. Then to compile a unit
9439 stored in @code{main.adb}, which uses this Ada library you would just type
9443 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9446 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9447 /SKIP_MISSING=@i{[OBJ_DIR]} main
9452 Using @command{gnatmake} along with the
9453 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9454 switch provides a mechanism for avoiding unnecessary recompilations. Using
9456 you can update the comments/format of your
9457 source files without having to recompile everything. Note, however, that
9458 adding or deleting lines in a source files may render its debugging
9459 info obsolete. If the file in question is a spec, the impact is rather
9460 limited, as that debugging info will only be useful during the
9461 elaboration phase of your program. For bodies the impact can be more
9462 significant. In all events, your debugger will warn you if a source file
9463 is more recent than the corresponding object, and alert you to the fact
9464 that the debugging information may be out of date.
9467 @node How gnatmake Works
9468 @section How @command{gnatmake} Works
9471 Generally @command{gnatmake} automatically performs all necessary
9472 recompilations and you don't need to worry about how it works. However,
9473 it may be useful to have some basic understanding of the @command{gnatmake}
9474 approach and in particular to understand how it uses the results of
9475 previous compilations without incorrectly depending on them.
9477 First a definition: an object file is considered @dfn{up to date} if the
9478 corresponding ALI file exists and if all the source files listed in the
9479 dependency section of this ALI file have time stamps matching those in
9480 the ALI file. This means that neither the source file itself nor any
9481 files that it depends on have been modified, and hence there is no need
9482 to recompile this file.
9484 @command{gnatmake} works by first checking if the specified main unit is up
9485 to date. If so, no compilations are required for the main unit. If not,
9486 @command{gnatmake} compiles the main program to build a new ALI file that
9487 reflects the latest sources. Then the ALI file of the main unit is
9488 examined to find all the source files on which the main program depends,
9489 and @command{gnatmake} recursively applies the above procedure on all these
9492 This process ensures that @command{gnatmake} only trusts the dependencies
9493 in an existing ALI file if they are known to be correct. Otherwise it
9494 always recompiles to determine a new, guaranteed accurate set of
9495 dependencies. As a result the program is compiled ``upside down'' from what may
9496 be more familiar as the required order of compilation in some other Ada
9497 systems. In particular, clients are compiled before the units on which
9498 they depend. The ability of GNAT to compile in any order is critical in
9499 allowing an order of compilation to be chosen that guarantees that
9500 @command{gnatmake} will recompute a correct set of new dependencies if
9503 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9504 imported by several of the executables, it will be recompiled at most once.
9506 Note: when using non-standard naming conventions
9507 (@pxref{Using Other File Names}), changing through a configuration pragmas
9508 file the version of a source and invoking @command{gnatmake} to recompile may
9509 have no effect, if the previous version of the source is still accessible
9510 by @command{gnatmake}. It may be necessary to use the switch
9511 ^-f^/FORCE_COMPILE^.
9513 @node Examples of gnatmake Usage
9514 @section Examples of @command{gnatmake} Usage
9517 @item gnatmake hello.adb
9518 Compile all files necessary to bind and link the main program
9519 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9520 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9522 @item gnatmake main1 main2 main3
9523 Compile all files necessary to bind and link the main programs
9524 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9525 (containing unit @code{Main2}) and @file{main3.adb}
9526 (containing unit @code{Main3}) and bind and link the resulting object files
9527 to generate three executable files @file{^main1^MAIN1.EXE^},
9528 @file{^main2^MAIN2.EXE^}
9529 and @file{^main3^MAIN3.EXE^}.
9532 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9536 @item gnatmake Main_Unit /QUIET
9537 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9538 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9540 Compile all files necessary to bind and link the main program unit
9541 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9542 be done with optimization level 2 and the order of elaboration will be
9543 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9544 displaying commands it is executing.
9547 @c *************************
9548 @node Improving Performance
9549 @chapter Improving Performance
9550 @cindex Improving performance
9553 This chapter presents several topics related to program performance.
9554 It first describes some of the tradeoffs that need to be considered
9555 and some of the techniques for making your program run faster.
9556 It then documents the @command{gnatelim} tool and unused subprogram/data
9557 elimination feature, which can reduce the size of program executables.
9559 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9560 driver (see @ref{The GNAT Driver and Project Files}).
9564 * Performance Considerations::
9565 * Text_IO Suggestions::
9566 * Reducing Size of Ada Executables with gnatelim::
9567 * Reducing Size of Executables with unused subprogram/data elimination::
9571 @c *****************************
9572 @node Performance Considerations
9573 @section Performance Considerations
9576 The GNAT system provides a number of options that allow a trade-off
9581 performance of the generated code
9584 speed of compilation
9587 minimization of dependences and recompilation
9590 the degree of run-time checking.
9594 The defaults (if no options are selected) aim at improving the speed
9595 of compilation and minimizing dependences, at the expense of performance
9596 of the generated code:
9603 no inlining of subprogram calls
9606 all run-time checks enabled except overflow and elaboration checks
9610 These options are suitable for most program development purposes. This
9611 chapter describes how you can modify these choices, and also provides
9612 some guidelines on debugging optimized code.
9615 * Controlling Run-Time Checks::
9616 * Use of Restrictions::
9617 * Optimization Levels::
9618 * Debugging Optimized Code::
9619 * Inlining of Subprograms::
9620 * Other Optimization Switches::
9621 * Optimization and Strict Aliasing::
9624 * Coverage Analysis::
9628 @node Controlling Run-Time Checks
9629 @subsection Controlling Run-Time Checks
9632 By default, GNAT generates all run-time checks, except integer overflow
9633 checks, stack overflow checks, and checks for access before elaboration on
9634 subprogram calls. The latter are not required in default mode, because all
9635 necessary checking is done at compile time.
9636 @cindex @option{-gnatp} (@command{gcc})
9637 @cindex @option{-gnato} (@command{gcc})
9638 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9639 be modified. @xref{Run-Time Checks}.
9641 Our experience is that the default is suitable for most development
9644 We treat integer overflow specially because these
9645 are quite expensive and in our experience are not as important as other
9646 run-time checks in the development process. Note that division by zero
9647 is not considered an overflow check, and divide by zero checks are
9648 generated where required by default.
9650 Elaboration checks are off by default, and also not needed by default, since
9651 GNAT uses a static elaboration analysis approach that avoids the need for
9652 run-time checking. This manual contains a full chapter discussing the issue
9653 of elaboration checks, and if the default is not satisfactory for your use,
9654 you should read this chapter.
9656 For validity checks, the minimal checks required by the Ada Reference
9657 Manual (for case statements and assignments to array elements) are on
9658 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9659 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9660 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9661 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9662 are also suppressed entirely if @option{-gnatp} is used.
9664 @cindex Overflow checks
9665 @cindex Checks, overflow
9668 @cindex pragma Suppress
9669 @cindex pragma Unsuppress
9670 Note that the setting of the switches controls the default setting of
9671 the checks. They may be modified using either @code{pragma Suppress} (to
9672 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9673 checks) in the program source.
9675 @node Use of Restrictions
9676 @subsection Use of Restrictions
9679 The use of pragma Restrictions allows you to control which features are
9680 permitted in your program. Apart from the obvious point that if you avoid
9681 relatively expensive features like finalization (enforceable by the use
9682 of pragma Restrictions (No_Finalization), the use of this pragma does not
9683 affect the generated code in most cases.
9685 One notable exception to this rule is that the possibility of task abort
9686 results in some distributed overhead, particularly if finalization or
9687 exception handlers are used. The reason is that certain sections of code
9688 have to be marked as non-abortable.
9690 If you use neither the @code{abort} statement, nor asynchronous transfer
9691 of control (@code{select @dots{} then abort}), then this distributed overhead
9692 is removed, which may have a general positive effect in improving
9693 overall performance. Especially code involving frequent use of tasking
9694 constructs and controlled types will show much improved performance.
9695 The relevant restrictions pragmas are
9697 @smallexample @c ada
9698 pragma Restrictions (No_Abort_Statements);
9699 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9703 It is recommended that these restriction pragmas be used if possible. Note
9704 that this also means that you can write code without worrying about the
9705 possibility of an immediate abort at any point.
9707 @node Optimization Levels
9708 @subsection Optimization Levels
9709 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9712 Without any optimization ^option,^qualifier,^
9713 the compiler's goal is to reduce the cost of
9714 compilation and to make debugging produce the expected results.
9715 Statements are independent: if you stop the program with a breakpoint between
9716 statements, you can then assign a new value to any variable or change
9717 the program counter to any other statement in the subprogram and get exactly
9718 the results you would expect from the source code.
9720 Turning on optimization makes the compiler attempt to improve the
9721 performance and/or code size at the expense of compilation time and
9722 possibly the ability to debug the program.
9725 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9726 the last such option is the one that is effective.
9729 The default is optimization off. This results in the fastest compile
9730 times, but GNAT makes absolutely no attempt to optimize, and the
9731 generated programs are considerably larger and slower than when
9732 optimization is enabled. You can use the
9734 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9735 @option{-O2}, @option{-O3}, and @option{-Os})
9738 @code{OPTIMIZE} qualifier
9740 to @command{gcc} to control the optimization level:
9743 @item ^-O0^/OPTIMIZE=NONE^
9744 No optimization (the default);
9745 generates unoptimized code but has
9746 the fastest compilation time.
9748 Note that many other compilers do fairly extensive optimization
9749 even if ``no optimization'' is specified. With gcc, it is
9750 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9751 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9752 really does mean no optimization at all. This difference between
9753 gcc and other compilers should be kept in mind when doing
9754 performance comparisons.
9756 @item ^-O1^/OPTIMIZE=SOME^
9757 Moderate optimization;
9758 optimizes reasonably well but does not
9759 degrade compilation time significantly.
9761 @item ^-O2^/OPTIMIZE=ALL^
9763 @itemx /OPTIMIZE=DEVELOPMENT
9766 generates highly optimized code and has
9767 the slowest compilation time.
9769 @item ^-O3^/OPTIMIZE=INLINING^
9770 Full optimization as in @option{-O2},
9771 and also attempts automatic inlining of small
9772 subprograms within a unit (@pxref{Inlining of Subprograms}).
9774 @item ^-Os^/OPTIMIZE=SPACE^
9775 Optimize space usage of resulting program.
9779 Higher optimization levels perform more global transformations on the
9780 program and apply more expensive analysis algorithms in order to generate
9781 faster and more compact code. The price in compilation time, and the
9782 resulting improvement in execution time,
9783 both depend on the particular application and the hardware environment.
9784 You should experiment to find the best level for your application.
9786 Since the precise set of optimizations done at each level will vary from
9787 release to release (and sometime from target to target), it is best to think
9788 of the optimization settings in general terms.
9789 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
9790 the GNU Compiler Collection (GCC)}, for details about
9791 ^the @option{-O} settings and a number of @option{-f} options that^how to^
9792 individually enable or disable specific optimizations.
9794 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
9795 been tested extensively at all optimization levels. There are some bugs
9796 which appear only with optimization turned on, but there have also been
9797 bugs which show up only in @emph{unoptimized} code. Selecting a lower
9798 level of optimization does not improve the reliability of the code
9799 generator, which in practice is highly reliable at all optimization
9802 Note regarding the use of @option{-O3}: The use of this optimization level
9803 is generally discouraged with GNAT, since it often results in larger
9804 executables which run more slowly. See further discussion of this point
9805 in @ref{Inlining of Subprograms}.
9807 @node Debugging Optimized Code
9808 @subsection Debugging Optimized Code
9809 @cindex Debugging optimized code
9810 @cindex Optimization and debugging
9813 Although it is possible to do a reasonable amount of debugging at
9815 nonzero optimization levels,
9816 the higher the level the more likely that
9819 @option{/OPTIMIZE} settings other than @code{NONE},
9820 such settings will make it more likely that
9822 source-level constructs will have been eliminated by optimization.
9823 For example, if a loop is strength-reduced, the loop
9824 control variable may be completely eliminated and thus cannot be
9825 displayed in the debugger.
9826 This can only happen at @option{-O2} or @option{-O3}.
9827 Explicit temporary variables that you code might be eliminated at
9828 ^level^setting^ @option{-O1} or higher.
9830 The use of the @option{^-g^/DEBUG^} switch,
9831 @cindex @option{^-g^/DEBUG^} (@command{gcc})
9832 which is needed for source-level debugging,
9833 affects the size of the program executable on disk,
9834 and indeed the debugging information can be quite large.
9835 However, it has no effect on the generated code (and thus does not
9836 degrade performance)
9838 Since the compiler generates debugging tables for a compilation unit before
9839 it performs optimizations, the optimizing transformations may invalidate some
9840 of the debugging data. You therefore need to anticipate certain
9841 anomalous situations that may arise while debugging optimized code.
9842 These are the most common cases:
9846 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
9848 the PC bouncing back and forth in the code. This may result from any of
9849 the following optimizations:
9853 @i{Common subexpression elimination:} using a single instance of code for a
9854 quantity that the source computes several times. As a result you
9855 may not be able to stop on what looks like a statement.
9858 @i{Invariant code motion:} moving an expression that does not change within a
9859 loop, to the beginning of the loop.
9862 @i{Instruction scheduling:} moving instructions so as to
9863 overlap loads and stores (typically) with other code, or in
9864 general to move computations of values closer to their uses. Often
9865 this causes you to pass an assignment statement without the assignment
9866 happening and then later bounce back to the statement when the
9867 value is actually needed. Placing a breakpoint on a line of code
9868 and then stepping over it may, therefore, not always cause all the
9869 expected side-effects.
9873 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
9874 two identical pieces of code are merged and the program counter suddenly
9875 jumps to a statement that is not supposed to be executed, simply because
9876 it (and the code following) translates to the same thing as the code
9877 that @emph{was} supposed to be executed. This effect is typically seen in
9878 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9879 a @code{break} in a C @code{^switch^switch^} statement.
9882 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9883 There are various reasons for this effect:
9887 In a subprogram prologue, a parameter may not yet have been moved to its
9891 A variable may be dead, and its register re-used. This is
9892 probably the most common cause.
9895 As mentioned above, the assignment of a value to a variable may
9899 A variable may be eliminated entirely by value propagation or
9900 other means. In this case, GCC may incorrectly generate debugging
9901 information for the variable
9905 In general, when an unexpected value appears for a local variable or parameter
9906 you should first ascertain if that value was actually computed by
9907 your program, as opposed to being incorrectly reported by the debugger.
9909 array elements in an object designated by an access value
9910 are generally less of a problem, once you have ascertained that the access
9912 Typically, this means checking variables in the preceding code and in the
9913 calling subprogram to verify that the value observed is explainable from other
9914 values (one must apply the procedure recursively to those
9915 other values); or re-running the code and stopping a little earlier
9916 (perhaps before the call) and stepping to better see how the variable obtained
9917 the value in question; or continuing to step @emph{from} the point of the
9918 strange value to see if code motion had simply moved the variable's
9923 In light of such anomalies, a recommended technique is to use @option{-O0}
9924 early in the software development cycle, when extensive debugging capabilities
9925 are most needed, and then move to @option{-O1} and later @option{-O2} as
9926 the debugger becomes less critical.
9927 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9928 a release management issue.
9930 Note that if you use @option{-g} you can then use the @command{strip} program
9931 on the resulting executable,
9932 which removes both debugging information and global symbols.
9935 @node Inlining of Subprograms
9936 @subsection Inlining of Subprograms
9939 A call to a subprogram in the current unit is inlined if all the
9940 following conditions are met:
9944 The optimization level is at least @option{-O1}.
9947 The called subprogram is suitable for inlining: It must be small enough
9948 and not contain something that @command{gcc} cannot support in inlined
9952 @cindex pragma Inline
9954 Either @code{pragma Inline} applies to the subprogram, or it is local
9955 to the unit and called once from within it, or it is small and automatic
9956 inlining (optimization level @option{-O3}) is specified.
9960 Calls to subprograms in @code{with}'ed units are normally not inlined.
9961 To achieve actual inlining (that is, replacement of the call by the code
9962 in the body of the subprogram), the following conditions must all be true.
9966 The optimization level is at least @option{-O1}.
9969 The called subprogram is suitable for inlining: It must be small enough
9970 and not contain something that @command{gcc} cannot support in inlined
9974 The call appears in a body (not in a package spec).
9977 There is a @code{pragma Inline} for the subprogram.
9980 @cindex @option{-gnatn} (@command{gcc})
9981 The @option{^-gnatn^/INLINE^} switch
9982 is used in the @command{gcc} command line
9985 Even if all these conditions are met, it may not be possible for
9986 the compiler to inline the call, due to the length of the body,
9987 or features in the body that make it impossible for the compiler
9990 Note that specifying the @option{-gnatn} switch causes additional
9991 compilation dependencies. Consider the following:
9993 @smallexample @c ada
10013 With the default behavior (no @option{-gnatn} switch specified), the
10014 compilation of the @code{Main} procedure depends only on its own source,
10015 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10016 means that editing the body of @code{R} does not require recompiling
10019 On the other hand, the call @code{R.Q} is not inlined under these
10020 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10021 is compiled, the call will be inlined if the body of @code{Q} is small
10022 enough, but now @code{Main} depends on the body of @code{R} in
10023 @file{r.adb} as well as on the spec. This means that if this body is edited,
10024 the main program must be recompiled. Note that this extra dependency
10025 occurs whether or not the call is in fact inlined by @command{gcc}.
10027 The use of front end inlining with @option{-gnatN} generates similar
10028 additional dependencies.
10030 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10031 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10032 can be used to prevent
10033 all inlining. This switch overrides all other conditions and ensures
10034 that no inlining occurs. The extra dependences resulting from
10035 @option{-gnatn} will still be active, even if
10036 this switch is used to suppress the resulting inlining actions.
10038 @cindex @option{-fno-inline-functions} (@command{gcc})
10039 Note: The @option{-fno-inline-functions} switch can be used to prevent
10040 automatic inlining of small subprograms if @option{-O3} is used.
10042 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10043 Note: The @option{-fno-inline-functions-called-once} switch
10044 can be used to prevent inlining of subprograms local to the unit
10045 and called once from within it if @option{-O1} is used.
10047 Note regarding the use of @option{-O3}: There is no difference in inlining
10048 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10049 pragma @code{Inline} assuming the use of @option{-gnatn}
10050 or @option{-gnatN} (the switches that activate inlining). If you have used
10051 pragma @code{Inline} in appropriate cases, then it is usually much better
10052 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10053 in this case only has the effect of inlining subprograms you did not
10054 think should be inlined. We often find that the use of @option{-O3} slows
10055 down code by performing excessive inlining, leading to increased instruction
10056 cache pressure from the increased code size. So the bottom line here is
10057 that you should not automatically assume that @option{-O3} is better than
10058 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10059 it actually improves performance.
10061 @node Other Optimization Switches
10062 @subsection Other Optimization Switches
10063 @cindex Optimization Switches
10065 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10066 @command{gcc} optimization switches are potentially usable. These switches
10067 have not been extensively tested with GNAT but can generally be expected
10068 to work. Examples of switches in this category are
10069 @option{-funroll-loops} and
10070 the various target-specific @option{-m} options (in particular, it has been
10071 observed that @option{-march=pentium4} can significantly improve performance
10072 on appropriate machines). For full details of these switches, see
10073 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10074 the GNU Compiler Collection (GCC)}.
10076 @node Optimization and Strict Aliasing
10077 @subsection Optimization and Strict Aliasing
10079 @cindex Strict Aliasing
10080 @cindex No_Strict_Aliasing
10083 The strong typing capabilities of Ada allow an optimizer to generate
10084 efficient code in situations where other languages would be forced to
10085 make worst case assumptions preventing such optimizations. Consider
10086 the following example:
10088 @smallexample @c ada
10091 type Int1 is new Integer;
10092 type Int2 is new Integer;
10093 type Int1A is access Int1;
10094 type Int2A is access Int2;
10101 for J in Data'Range loop
10102 if Data (J) = Int1V.all then
10103 Int2V.all := Int2V.all + 1;
10112 In this example, since the variable @code{Int1V} can only access objects
10113 of type @code{Int1}, and @code{Int2V} can only access objects of type
10114 @code{Int2}, there is no possibility that the assignment to
10115 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10116 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10117 for all iterations of the loop and avoid the extra memory reference
10118 required to dereference it each time through the loop.
10120 This kind of optimization, called strict aliasing analysis, is
10121 triggered by specifying an optimization level of @option{-O2} or
10122 higher and allows @code{GNAT} to generate more efficient code
10123 when access values are involved.
10125 However, although this optimization is always correct in terms of
10126 the formal semantics of the Ada Reference Manual, difficulties can
10127 arise if features like @code{Unchecked_Conversion} are used to break
10128 the typing system. Consider the following complete program example:
10130 @smallexample @c ada
10133 type int1 is new integer;
10134 type int2 is new integer;
10135 type a1 is access int1;
10136 type a2 is access int2;
10141 function to_a2 (Input : a1) return a2;
10144 with Unchecked_Conversion;
10146 function to_a2 (Input : a1) return a2 is
10148 new Unchecked_Conversion (a1, a2);
10150 return to_a2u (Input);
10156 with Text_IO; use Text_IO;
10158 v1 : a1 := new int1;
10159 v2 : a2 := to_a2 (v1);
10163 put_line (int1'image (v1.all));
10169 This program prints out 0 in @option{-O0} or @option{-O1}
10170 mode, but it prints out 1 in @option{-O2} mode. That's
10171 because in strict aliasing mode, the compiler can and
10172 does assume that the assignment to @code{v2.all} could not
10173 affect the value of @code{v1.all}, since different types
10176 This behavior is not a case of non-conformance with the standard, since
10177 the Ada RM specifies that an unchecked conversion where the resulting
10178 bit pattern is not a correct value of the target type can result in an
10179 abnormal value and attempting to reference an abnormal value makes the
10180 execution of a program erroneous. That's the case here since the result
10181 does not point to an object of type @code{int2}. This means that the
10182 effect is entirely unpredictable.
10184 However, although that explanation may satisfy a language
10185 lawyer, in practice an applications programmer expects an
10186 unchecked conversion involving pointers to create true
10187 aliases and the behavior of printing 1 seems plain wrong.
10188 In this case, the strict aliasing optimization is unwelcome.
10190 Indeed the compiler recognizes this possibility, and the
10191 unchecked conversion generates a warning:
10194 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10195 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10196 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10200 Unfortunately the problem is recognized when compiling the body of
10201 package @code{p2}, but the actual "bad" code is generated while
10202 compiling the body of @code{m} and this latter compilation does not see
10203 the suspicious @code{Unchecked_Conversion}.
10205 As implied by the warning message, there are approaches you can use to
10206 avoid the unwanted strict aliasing optimization in a case like this.
10208 One possibility is to simply avoid the use of @option{-O2}, but
10209 that is a bit drastic, since it throws away a number of useful
10210 optimizations that do not involve strict aliasing assumptions.
10212 A less drastic approach is to compile the program using the
10213 option @option{-fno-strict-aliasing}. Actually it is only the
10214 unit containing the dereferencing of the suspicious pointer
10215 that needs to be compiled. So in this case, if we compile
10216 unit @code{m} with this switch, then we get the expected
10217 value of zero printed. Analyzing which units might need
10218 the switch can be painful, so a more reasonable approach
10219 is to compile the entire program with options @option{-O2}
10220 and @option{-fno-strict-aliasing}. If the performance is
10221 satisfactory with this combination of options, then the
10222 advantage is that the entire issue of possible "wrong"
10223 optimization due to strict aliasing is avoided.
10225 To avoid the use of compiler switches, the configuration
10226 pragma @code{No_Strict_Aliasing} with no parameters may be
10227 used to specify that for all access types, the strict
10228 aliasing optimization should be suppressed.
10230 However, these approaches are still overkill, in that they causes
10231 all manipulations of all access values to be deoptimized. A more
10232 refined approach is to concentrate attention on the specific
10233 access type identified as problematic.
10235 First, if a careful analysis of uses of the pointer shows
10236 that there are no possible problematic references, then
10237 the warning can be suppressed by bracketing the
10238 instantiation of @code{Unchecked_Conversion} to turn
10241 @smallexample @c ada
10242 pragma Warnings (Off);
10244 new Unchecked_Conversion (a1, a2);
10245 pragma Warnings (On);
10249 Of course that approach is not appropriate for this particular
10250 example, since indeed there is a problematic reference. In this
10251 case we can take one of two other approaches.
10253 The first possibility is to move the instantiation of unchecked
10254 conversion to the unit in which the type is declared. In
10255 this example, we would move the instantiation of
10256 @code{Unchecked_Conversion} from the body of package
10257 @code{p2} to the spec of package @code{p1}. Now the
10258 warning disappears. That's because any use of the
10259 access type knows there is a suspicious unchecked
10260 conversion, and the strict aliasing optimization
10261 is automatically suppressed for the type.
10263 If it is not practical to move the unchecked conversion to the same unit
10264 in which the destination access type is declared (perhaps because the
10265 source type is not visible in that unit), you may use pragma
10266 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10267 same declarative sequence as the declaration of the access type:
10269 @smallexample @c ada
10270 type a2 is access int2;
10271 pragma No_Strict_Aliasing (a2);
10275 Here again, the compiler now knows that the strict aliasing optimization
10276 should be suppressed for any reference to type @code{a2} and the
10277 expected behavior is obtained.
10279 Finally, note that although the compiler can generate warnings for
10280 simple cases of unchecked conversions, there are tricker and more
10281 indirect ways of creating type incorrect aliases which the compiler
10282 cannot detect. Examples are the use of address overlays and unchecked
10283 conversions involving composite types containing access types as
10284 components. In such cases, no warnings are generated, but there can
10285 still be aliasing problems. One safe coding practice is to forbid the
10286 use of address clauses for type overlaying, and to allow unchecked
10287 conversion only for primitive types. This is not really a significant
10288 restriction since any possible desired effect can be achieved by
10289 unchecked conversion of access values.
10292 @node Coverage Analysis
10293 @subsection Coverage Analysis
10296 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10297 the user to determine the distribution of execution time across a program,
10298 @pxref{Profiling} for details of usage.
10302 @node Text_IO Suggestions
10303 @section @code{Text_IO} Suggestions
10304 @cindex @code{Text_IO} and performance
10307 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10308 the requirement of maintaining page and line counts. If performance
10309 is critical, a recommendation is to use @code{Stream_IO} instead of
10310 @code{Text_IO} for volume output, since this package has less overhead.
10312 If @code{Text_IO} must be used, note that by default output to the standard
10313 output and standard error files is unbuffered (this provides better
10314 behavior when output statements are used for debugging, or if the
10315 progress of a program is observed by tracking the output, e.g. by
10316 using the Unix @command{tail -f} command to watch redirected output.
10318 If you are generating large volumes of output with @code{Text_IO} and
10319 performance is an important factor, use a designated file instead
10320 of the standard output file, or change the standard output file to
10321 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10325 @node Reducing Size of Ada Executables with gnatelim
10326 @section Reducing Size of Ada Executables with @code{gnatelim}
10330 This section describes @command{gnatelim}, a tool which detects unused
10331 subprograms and helps the compiler to create a smaller executable for your
10336 * Running gnatelim::
10337 * Correcting the List of Eliminate Pragmas::
10338 * Making Your Executables Smaller::
10339 * Summary of the gnatelim Usage Cycle::
10342 @node About gnatelim
10343 @subsection About @code{gnatelim}
10346 When a program shares a set of Ada
10347 packages with other programs, it may happen that this program uses
10348 only a fraction of the subprograms defined in these packages. The code
10349 created for these unused subprograms increases the size of the executable.
10351 @code{gnatelim} tracks unused subprograms in an Ada program and
10352 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10353 subprograms that are declared but never called. By placing the list of
10354 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10355 recompiling your program, you may decrease the size of its executable,
10356 because the compiler will not generate the code for 'eliminated' subprograms.
10357 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10358 information about this pragma.
10360 @code{gnatelim} needs as its input data the name of the main subprogram
10361 and a bind file for a main subprogram.
10363 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10364 the main subprogram. @code{gnatelim} can work with both Ada and C
10365 bind files; when both are present, it uses the Ada bind file.
10366 The following commands will build the program and create the bind file:
10369 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10370 $ gnatbind main_prog
10373 Note that @code{gnatelim} needs neither object nor ALI files.
10375 @node Running gnatelim
10376 @subsection Running @code{gnatelim}
10379 @code{gnatelim} has the following command-line interface:
10382 $ gnatelim @ovar{options} name
10386 @code{name} should be a name of a source file that contains the main subprogram
10387 of a program (partition).
10389 @code{gnatelim} has the following switches:
10394 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10395 Quiet mode: by default @code{gnatelim} outputs to the standard error
10396 stream the number of program units left to be processed. This option turns
10399 @item ^-v^/VERBOSE^
10400 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10401 Verbose mode: @code{gnatelim} version information is printed as Ada
10402 comments to the standard output stream. Also, in addition to the number of
10403 program units left @code{gnatelim} will output the name of the current unit
10407 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10408 Also look for subprograms from the GNAT run time that can be eliminated. Note
10409 that when @file{gnat.adc} is produced using this switch, the entire program
10410 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10412 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10413 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10414 When looking for source files also look in directory @var{dir}. Specifying
10415 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10416 sources in the current directory.
10418 @item ^-b^/BIND_FILE=^@var{bind_file}
10419 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10420 Specifies @var{bind_file} as the bind file to process. If not set, the name
10421 of the bind file is computed from the full expanded Ada name
10422 of a main subprogram.
10424 @item ^-C^/CONFIG_FILE=^@var{config_file}
10425 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10426 Specifies a file @var{config_file} that contains configuration pragmas. The
10427 file must be specified with full path.
10429 @item ^--GCC^/COMPILER^=@var{compiler_name}
10430 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10431 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10432 available on the path.
10434 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10435 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10436 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10437 available on the path.
10441 @code{gnatelim} sends its output to the standard output stream, and all the
10442 tracing and debug information is sent to the standard error stream.
10443 In order to produce a proper GNAT configuration file
10444 @file{gnat.adc}, redirection must be used:
10448 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10451 $ gnatelim main_prog.adb > gnat.adc
10460 $ gnatelim main_prog.adb >> gnat.adc
10464 in order to append the @code{gnatelim} output to the existing contents of
10468 @node Correcting the List of Eliminate Pragmas
10469 @subsection Correcting the List of Eliminate Pragmas
10472 In some rare cases @code{gnatelim} may try to eliminate
10473 subprograms that are actually called in the program. In this case, the
10474 compiler will generate an error message of the form:
10477 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10481 You will need to manually remove the wrong @code{Eliminate} pragmas from
10482 the @file{gnat.adc} file. You should recompile your program
10483 from scratch after that, because you need a consistent @file{gnat.adc} file
10484 during the entire compilation.
10486 @node Making Your Executables Smaller
10487 @subsection Making Your Executables Smaller
10490 In order to get a smaller executable for your program you now have to
10491 recompile the program completely with the new @file{gnat.adc} file
10492 created by @code{gnatelim} in your current directory:
10495 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10499 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10500 recompile everything
10501 with the set of pragmas @code{Eliminate} that you have obtained with
10502 @command{gnatelim}).
10504 Be aware that the set of @code{Eliminate} pragmas is specific to each
10505 program. It is not recommended to merge sets of @code{Eliminate}
10506 pragmas created for different programs in one @file{gnat.adc} file.
10508 @node Summary of the gnatelim Usage Cycle
10509 @subsection Summary of the gnatelim Usage Cycle
10512 Here is a quick summary of the steps to be taken in order to reduce
10513 the size of your executables with @code{gnatelim}. You may use
10514 other GNAT options to control the optimization level,
10515 to produce the debugging information, to set search path, etc.
10519 Produce a bind file
10522 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10523 $ gnatbind main_prog
10527 Generate a list of @code{Eliminate} pragmas
10530 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10533 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10538 Recompile the application
10541 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10546 @node Reducing Size of Executables with unused subprogram/data elimination
10547 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10548 @findex unused subprogram/data elimination
10551 This section describes how you can eliminate unused subprograms and data from
10552 your executable just by setting options at compilation time.
10555 * About unused subprogram/data elimination::
10556 * Compilation options::
10557 * Example of unused subprogram/data elimination::
10560 @node About unused subprogram/data elimination
10561 @subsection About unused subprogram/data elimination
10564 By default, an executable contains all code and data of its composing objects
10565 (directly linked or coming from statically linked libraries), even data or code
10566 never used by this executable.
10568 This feature will allow you to eliminate such unused code from your
10569 executable, making it smaller (in disk and in memory).
10571 This functionality is available on all Linux platforms except for the IA-64
10572 architecture and on all cross platforms using the ELF binary file format.
10573 In both cases GNU binutils version 2.16 or later are required to enable it.
10575 @node Compilation options
10576 @subsection Compilation options
10579 The operation of eliminating the unused code and data from the final executable
10580 is directly performed by the linker.
10582 In order to do this, it has to work with objects compiled with the
10584 @option{-ffunction-sections} @option{-fdata-sections}.
10585 @cindex @option{-ffunction-sections} (@command{gcc})
10586 @cindex @option{-fdata-sections} (@command{gcc})
10587 These options are usable with C and Ada files.
10588 They will place respectively each
10589 function or data in a separate section in the resulting object file.
10591 Once the objects and static libraries are created with these options, the
10592 linker can perform the dead code elimination. You can do this by setting
10593 the @option{-Wl,--gc-sections} option to gcc command or in the
10594 @option{-largs} section of @command{gnatmake}. This will perform a
10595 garbage collection of code and data never referenced.
10597 If the linker performs a partial link (@option{-r} ld linker option), then you
10598 will need to provide one or several entry point using the
10599 @option{-e} / @option{--entry} ld option.
10601 Note that objects compiled without the @option{-ffunction-sections} and
10602 @option{-fdata-sections} options can still be linked with the executable.
10603 However, no dead code elimination will be performed on those objects (they will
10606 The GNAT static library is now compiled with -ffunction-sections and
10607 -fdata-sections on some platforms. This allows you to eliminate the unused code
10608 and data of the GNAT library from your executable.
10610 @node Example of unused subprogram/data elimination
10611 @subsection Example of unused subprogram/data elimination
10614 Here is a simple example:
10616 @smallexample @c ada
10625 Used_Data : Integer;
10626 Unused_Data : Integer;
10628 procedure Used (Data : Integer);
10629 procedure Unused (Data : Integer);
10632 package body Aux is
10633 procedure Used (Data : Integer) is
10638 procedure Unused (Data : Integer) is
10640 Unused_Data := Data;
10646 @code{Unused} and @code{Unused_Data} are never referenced in this code
10647 excerpt, and hence they may be safely removed from the final executable.
10652 $ nm test | grep used
10653 020015f0 T aux__unused
10654 02005d88 B aux__unused_data
10655 020015cc T aux__used
10656 02005d84 B aux__used_data
10658 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10659 -largs -Wl,--gc-sections
10661 $ nm test | grep used
10662 02005350 T aux__used
10663 0201ffe0 B aux__used_data
10667 It can be observed that the procedure @code{Unused} and the object
10668 @code{Unused_Data} are removed by the linker when using the
10669 appropriate options.
10671 @c ********************************
10672 @node Renaming Files Using gnatchop
10673 @chapter Renaming Files Using @code{gnatchop}
10677 This chapter discusses how to handle files with multiple units by using
10678 the @code{gnatchop} utility. This utility is also useful in renaming
10679 files to meet the standard GNAT default file naming conventions.
10682 * Handling Files with Multiple Units::
10683 * Operating gnatchop in Compilation Mode::
10684 * Command Line for gnatchop::
10685 * Switches for gnatchop::
10686 * Examples of gnatchop Usage::
10689 @node Handling Files with Multiple Units
10690 @section Handling Files with Multiple Units
10693 The basic compilation model of GNAT requires that a file submitted to the
10694 compiler have only one unit and there be a strict correspondence
10695 between the file name and the unit name.
10697 The @code{gnatchop} utility allows both of these rules to be relaxed,
10698 allowing GNAT to process files which contain multiple compilation units
10699 and files with arbitrary file names. @code{gnatchop}
10700 reads the specified file and generates one or more output files,
10701 containing one unit per file. The unit and the file name correspond,
10702 as required by GNAT.
10704 If you want to permanently restructure a set of ``foreign'' files so that
10705 they match the GNAT rules, and do the remaining development using the
10706 GNAT structure, you can simply use @command{gnatchop} once, generate the
10707 new set of files and work with them from that point on.
10709 Alternatively, if you want to keep your files in the ``foreign'' format,
10710 perhaps to maintain compatibility with some other Ada compilation
10711 system, you can set up a procedure where you use @command{gnatchop} each
10712 time you compile, regarding the source files that it writes as temporary
10713 files that you throw away.
10715 Note that if your file containing multiple units starts with a byte order
10716 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
10717 will each start with a copy of this BOM, meaning that they can be compiled
10718 automatically in UTF-8 mode without needing to specify an explicit encoding.
10720 @node Operating gnatchop in Compilation Mode
10721 @section Operating gnatchop in Compilation Mode
10724 The basic function of @code{gnatchop} is to take a file with multiple units
10725 and split it into separate files. The boundary between files is reasonably
10726 clear, except for the issue of comments and pragmas. In default mode, the
10727 rule is that any pragmas between units belong to the previous unit, except
10728 that configuration pragmas always belong to the following unit. Any comments
10729 belong to the following unit. These rules
10730 almost always result in the right choice of
10731 the split point without needing to mark it explicitly and most users will
10732 find this default to be what they want. In this default mode it is incorrect to
10733 submit a file containing only configuration pragmas, or one that ends in
10734 configuration pragmas, to @code{gnatchop}.
10736 However, using a special option to activate ``compilation mode'',
10738 can perform another function, which is to provide exactly the semantics
10739 required by the RM for handling of configuration pragmas in a compilation.
10740 In the absence of configuration pragmas (at the main file level), this
10741 option has no effect, but it causes such configuration pragmas to be handled
10742 in a quite different manner.
10744 First, in compilation mode, if @code{gnatchop} is given a file that consists of
10745 only configuration pragmas, then this file is appended to the
10746 @file{gnat.adc} file in the current directory. This behavior provides
10747 the required behavior described in the RM for the actions to be taken
10748 on submitting such a file to the compiler, namely that these pragmas
10749 should apply to all subsequent compilations in the same compilation
10750 environment. Using GNAT, the current directory, possibly containing a
10751 @file{gnat.adc} file is the representation
10752 of a compilation environment. For more information on the
10753 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
10755 Second, in compilation mode, if @code{gnatchop}
10756 is given a file that starts with
10757 configuration pragmas, and contains one or more units, then these
10758 configuration pragmas are prepended to each of the chopped files. This
10759 behavior provides the required behavior described in the RM for the
10760 actions to be taken on compiling such a file, namely that the pragmas
10761 apply to all units in the compilation, but not to subsequently compiled
10764 Finally, if configuration pragmas appear between units, they are appended
10765 to the previous unit. This results in the previous unit being illegal,
10766 since the compiler does not accept configuration pragmas that follow
10767 a unit. This provides the required RM behavior that forbids configuration
10768 pragmas other than those preceding the first compilation unit of a
10771 For most purposes, @code{gnatchop} will be used in default mode. The
10772 compilation mode described above is used only if you need exactly
10773 accurate behavior with respect to compilations, and you have files
10774 that contain multiple units and configuration pragmas. In this
10775 circumstance the use of @code{gnatchop} with the compilation mode
10776 switch provides the required behavior, and is for example the mode
10777 in which GNAT processes the ACVC tests.
10779 @node Command Line for gnatchop
10780 @section Command Line for @code{gnatchop}
10783 The @code{gnatchop} command has the form:
10786 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
10791 The only required argument is the file name of the file to be chopped.
10792 There are no restrictions on the form of this file name. The file itself
10793 contains one or more Ada units, in normal GNAT format, concatenated
10794 together. As shown, more than one file may be presented to be chopped.
10796 When run in default mode, @code{gnatchop} generates one output file in
10797 the current directory for each unit in each of the files.
10799 @var{directory}, if specified, gives the name of the directory to which
10800 the output files will be written. If it is not specified, all files are
10801 written to the current directory.
10803 For example, given a
10804 file called @file{hellofiles} containing
10806 @smallexample @c ada
10811 with Text_IO; use Text_IO;
10814 Put_Line ("Hello");
10824 $ gnatchop ^hellofiles^HELLOFILES.^
10828 generates two files in the current directory, one called
10829 @file{hello.ads} containing the single line that is the procedure spec,
10830 and the other called @file{hello.adb} containing the remaining text. The
10831 original file is not affected. The generated files can be compiled in
10835 When gnatchop is invoked on a file that is empty or that contains only empty
10836 lines and/or comments, gnatchop will not fail, but will not produce any
10839 For example, given a
10840 file called @file{toto.txt} containing
10842 @smallexample @c ada
10854 $ gnatchop ^toto.txt^TOT.TXT^
10858 will not produce any new file and will result in the following warnings:
10861 toto.txt:1:01: warning: empty file, contains no compilation units
10862 no compilation units found
10863 no source files written
10866 @node Switches for gnatchop
10867 @section Switches for @code{gnatchop}
10870 @command{gnatchop} recognizes the following switches:
10876 @cindex @option{--version} @command{gnatchop}
10877 Display Copyright and version, then exit disregarding all other options.
10880 @cindex @option{--help} @command{gnatchop}
10881 If @option{--version} was not used, display usage, then exit disregarding
10884 @item ^-c^/COMPILATION^
10885 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
10886 Causes @code{gnatchop} to operate in compilation mode, in which
10887 configuration pragmas are handled according to strict RM rules. See
10888 previous section for a full description of this mode.
10891 @item -gnat@var{xxx}
10892 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
10893 used to parse the given file. Not all @var{xxx} options make sense,
10894 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
10895 process a source file that uses Latin-2 coding for identifiers.
10899 Causes @code{gnatchop} to generate a brief help summary to the standard
10900 output file showing usage information.
10902 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
10903 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
10904 Limit generated file names to the specified number @code{mm}
10906 This is useful if the
10907 resulting set of files is required to be interoperable with systems
10908 which limit the length of file names.
10910 If no value is given, or
10911 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
10912 a default of 39, suitable for OpenVMS Alpha
10913 Systems, is assumed
10916 No space is allowed between the @option{-k} and the numeric value. The numeric
10917 value may be omitted in which case a default of @option{-k8},
10919 with DOS-like file systems, is used. If no @option{-k} switch
10921 there is no limit on the length of file names.
10924 @item ^-p^/PRESERVE^
10925 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
10926 Causes the file ^modification^creation^ time stamp of the input file to be
10927 preserved and used for the time stamp of the output file(s). This may be
10928 useful for preserving coherency of time stamps in an environment where
10929 @code{gnatchop} is used as part of a standard build process.
10932 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
10933 Causes output of informational messages indicating the set of generated
10934 files to be suppressed. Warnings and error messages are unaffected.
10936 @item ^-r^/REFERENCE^
10937 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
10938 @findex Source_Reference
10939 Generate @code{Source_Reference} pragmas. Use this switch if the output
10940 files are regarded as temporary and development is to be done in terms
10941 of the original unchopped file. This switch causes
10942 @code{Source_Reference} pragmas to be inserted into each of the
10943 generated files to refers back to the original file name and line number.
10944 The result is that all error messages refer back to the original
10946 In addition, the debugging information placed into the object file (when
10947 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
10949 also refers back to this original file so that tools like profilers and
10950 debuggers will give information in terms of the original unchopped file.
10952 If the original file to be chopped itself contains
10953 a @code{Source_Reference}
10954 pragma referencing a third file, then gnatchop respects
10955 this pragma, and the generated @code{Source_Reference} pragmas
10956 in the chopped file refer to the original file, with appropriate
10957 line numbers. This is particularly useful when @code{gnatchop}
10958 is used in conjunction with @code{gnatprep} to compile files that
10959 contain preprocessing statements and multiple units.
10961 @item ^-v^/VERBOSE^
10962 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
10963 Causes @code{gnatchop} to operate in verbose mode. The version
10964 number and copyright notice are output, as well as exact copies of
10965 the gnat1 commands spawned to obtain the chop control information.
10967 @item ^-w^/OVERWRITE^
10968 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
10969 Overwrite existing file names. Normally @code{gnatchop} regards it as a
10970 fatal error if there is already a file with the same name as a
10971 file it would otherwise output, in other words if the files to be
10972 chopped contain duplicated units. This switch bypasses this
10973 check, and causes all but the last instance of such duplicated
10974 units to be skipped.
10977 @item --GCC=@var{xxxx}
10978 @cindex @option{--GCC=} (@code{gnatchop})
10979 Specify the path of the GNAT parser to be used. When this switch is used,
10980 no attempt is made to add the prefix to the GNAT parser executable.
10984 @node Examples of gnatchop Usage
10985 @section Examples of @code{gnatchop} Usage
10989 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
10992 @item gnatchop -w hello_s.ada prerelease/files
10995 Chops the source file @file{hello_s.ada}. The output files will be
10996 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
10998 files with matching names in that directory (no files in the current
10999 directory are modified).
11001 @item gnatchop ^archive^ARCHIVE.^
11002 Chops the source file @file{^archive^ARCHIVE.^}
11003 into the current directory. One
11004 useful application of @code{gnatchop} is in sending sets of sources
11005 around, for example in email messages. The required sources are simply
11006 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11008 @command{gnatchop} is used at the other end to reconstitute the original
11011 @item gnatchop file1 file2 file3 direc
11012 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11013 the resulting files in the directory @file{direc}. Note that if any units
11014 occur more than once anywhere within this set of files, an error message
11015 is generated, and no files are written. To override this check, use the
11016 @option{^-w^/OVERWRITE^} switch,
11017 in which case the last occurrence in the last file will
11018 be the one that is output, and earlier duplicate occurrences for a given
11019 unit will be skipped.
11022 @node Configuration Pragmas
11023 @chapter Configuration Pragmas
11024 @cindex Configuration pragmas
11025 @cindex Pragmas, configuration
11028 Configuration pragmas include those pragmas described as
11029 such in the Ada Reference Manual, as well as
11030 implementation-dependent pragmas that are configuration pragmas.
11031 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11032 for details on these additional GNAT-specific configuration pragmas.
11033 Most notably, the pragma @code{Source_File_Name}, which allows
11034 specifying non-default names for source files, is a configuration
11035 pragma. The following is a complete list of configuration pragmas
11036 recognized by GNAT:
11048 Compile_Time_Warning
11050 Component_Alignment
11057 External_Name_Casing
11060 Float_Representation
11073 Priority_Specific_Dispatching
11076 Propagate_Exceptions
11079 Restricted_Run_Time
11081 Restrictions_Warnings
11084 Source_File_Name_Project
11087 Suppress_Exception_Locations
11088 Task_Dispatching_Policy
11094 Wide_Character_Encoding
11099 * Handling of Configuration Pragmas::
11100 * The Configuration Pragmas Files::
11103 @node Handling of Configuration Pragmas
11104 @section Handling of Configuration Pragmas
11106 Configuration pragmas may either appear at the start of a compilation
11107 unit, in which case they apply only to that unit, or they may apply to
11108 all compilations performed in a given compilation environment.
11110 GNAT also provides the @code{gnatchop} utility to provide an automatic
11111 way to handle configuration pragmas following the semantics for
11112 compilations (that is, files with multiple units), described in the RM.
11113 See @ref{Operating gnatchop in Compilation Mode} for details.
11114 However, for most purposes, it will be more convenient to edit the
11115 @file{gnat.adc} file that contains configuration pragmas directly,
11116 as described in the following section.
11118 @node The Configuration Pragmas Files
11119 @section The Configuration Pragmas Files
11120 @cindex @file{gnat.adc}
11123 In GNAT a compilation environment is defined by the current
11124 directory at the time that a compile command is given. This current
11125 directory is searched for a file whose name is @file{gnat.adc}. If
11126 this file is present, it is expected to contain one or more
11127 configuration pragmas that will be applied to the current compilation.
11128 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11131 Configuration pragmas may be entered into the @file{gnat.adc} file
11132 either by running @code{gnatchop} on a source file that consists only of
11133 configuration pragmas, or more conveniently by
11134 direct editing of the @file{gnat.adc} file, which is a standard format
11137 In addition to @file{gnat.adc}, additional files containing configuration
11138 pragmas may be applied to the current compilation using the switch
11139 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11140 contains only configuration pragmas. These configuration pragmas are
11141 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11142 is present and switch @option{-gnatA} is not used).
11144 It is allowed to specify several switches @option{-gnatec}, all of which
11145 will be taken into account.
11147 If you are using project file, a separate mechanism is provided using
11148 project attributes, see @ref{Specifying Configuration Pragmas} for more
11152 Of special interest to GNAT OpenVMS Alpha is the following
11153 configuration pragma:
11155 @smallexample @c ada
11157 pragma Extend_System (Aux_DEC);
11162 In the presence of this pragma, GNAT adds to the definition of the
11163 predefined package SYSTEM all the additional types and subprograms that are
11164 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11167 @node Handling Arbitrary File Naming Conventions Using gnatname
11168 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11169 @cindex Arbitrary File Naming Conventions
11172 * Arbitrary File Naming Conventions::
11173 * Running gnatname::
11174 * Switches for gnatname::
11175 * Examples of gnatname Usage::
11178 @node Arbitrary File Naming Conventions
11179 @section Arbitrary File Naming Conventions
11182 The GNAT compiler must be able to know the source file name of a compilation
11183 unit. When using the standard GNAT default file naming conventions
11184 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11185 does not need additional information.
11188 When the source file names do not follow the standard GNAT default file naming
11189 conventions, the GNAT compiler must be given additional information through
11190 a configuration pragmas file (@pxref{Configuration Pragmas})
11192 When the non-standard file naming conventions are well-defined,
11193 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11194 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11195 if the file naming conventions are irregular or arbitrary, a number
11196 of pragma @code{Source_File_Name} for individual compilation units
11198 To help maintain the correspondence between compilation unit names and
11199 source file names within the compiler,
11200 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11203 @node Running gnatname
11204 @section Running @code{gnatname}
11207 The usual form of the @code{gnatname} command is
11210 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11211 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11215 All of the arguments are optional. If invoked without any argument,
11216 @code{gnatname} will display its usage.
11219 When used with at least one naming pattern, @code{gnatname} will attempt to
11220 find all the compilation units in files that follow at least one of the
11221 naming patterns. To find these compilation units,
11222 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11226 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11227 Each Naming Pattern is enclosed between double quotes.
11228 A Naming Pattern is a regular expression similar to the wildcard patterns
11229 used in file names by the Unix shells or the DOS prompt.
11232 @code{gnatname} may be called with several sections of directories/patterns.
11233 Sections are separated by switch @code{--and}. In each section, there must be
11234 at least one pattern. If no directory is specified in a section, the current
11235 directory (or the project directory is @code{-P} is used) is implied.
11236 The options other that the directory switches and the patterns apply globally
11237 even if they are in different sections.
11240 Examples of Naming Patterns are
11249 For a more complete description of the syntax of Naming Patterns,
11250 see the second kind of regular expressions described in @file{g-regexp.ads}
11251 (the ``Glob'' regular expressions).
11254 When invoked with no switch @code{-P}, @code{gnatname} will create a
11255 configuration pragmas file @file{gnat.adc} in the current working directory,
11256 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11259 @node Switches for gnatname
11260 @section Switches for @code{gnatname}
11263 Switches for @code{gnatname} must precede any specified Naming Pattern.
11266 You may specify any of the following switches to @code{gnatname}:
11272 @cindex @option{--version} @command{gnatname}
11273 Display Copyright and version, then exit disregarding all other options.
11276 @cindex @option{--help} @command{gnatname}
11277 If @option{--version} was not used, display usage, then exit disregarding
11281 Start another section of directories/patterns.
11283 @item ^-c^/CONFIG_FILE=^@file{file}
11284 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11285 Create a configuration pragmas file @file{file} (instead of the default
11288 There may be zero, one or more space between @option{-c} and
11291 @file{file} may include directory information. @file{file} must be
11292 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11293 When a switch @option{^-c^/CONFIG_FILE^} is
11294 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11296 @item ^-d^/SOURCE_DIRS=^@file{dir}
11297 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11298 Look for source files in directory @file{dir}. There may be zero, one or more
11299 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11300 When a switch @option{^-d^/SOURCE_DIRS^}
11301 is specified, the current working directory will not be searched for source
11302 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11303 or @option{^-D^/DIR_FILES^} switch.
11304 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11305 If @file{dir} is a relative path, it is relative to the directory of
11306 the configuration pragmas file specified with switch
11307 @option{^-c^/CONFIG_FILE^},
11308 or to the directory of the project file specified with switch
11309 @option{^-P^/PROJECT_FILE^} or,
11310 if neither switch @option{^-c^/CONFIG_FILE^}
11311 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11312 current working directory. The directory
11313 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11315 @item ^-D^/DIRS_FILE=^@file{file}
11316 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11317 Look for source files in all directories listed in text file @file{file}.
11318 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11320 @file{file} must be an existing, readable text file.
11321 Each nonempty line in @file{file} must be a directory.
11322 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11323 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11326 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11327 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11328 Foreign patterns. Using this switch, it is possible to add sources of languages
11329 other than Ada to the list of sources of a project file.
11330 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11333 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11336 will look for Ada units in all files with the @file{.ada} extension,
11337 and will add to the list of file for project @file{prj.gpr} the C files
11338 with extension @file{.^c^C^}.
11341 @cindex @option{^-h^/HELP^} (@code{gnatname})
11342 Output usage (help) information. The output is written to @file{stdout}.
11344 @item ^-P^/PROJECT_FILE=^@file{proj}
11345 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11346 Create or update project file @file{proj}. There may be zero, one or more space
11347 between @option{-P} and @file{proj}. @file{proj} may include directory
11348 information. @file{proj} must be writable.
11349 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11350 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11351 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11353 @item ^-v^/VERBOSE^
11354 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11355 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11356 This includes name of the file written, the name of the directories to search
11357 and, for each file in those directories whose name matches at least one of
11358 the Naming Patterns, an indication of whether the file contains a unit,
11359 and if so the name of the unit.
11361 @item ^-v -v^/VERBOSE /VERBOSE^
11362 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11363 Very Verbose mode. In addition to the output produced in verbose mode,
11364 for each file in the searched directories whose name matches none of
11365 the Naming Patterns, an indication is given that there is no match.
11367 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11368 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11369 Excluded patterns. Using this switch, it is possible to exclude some files
11370 that would match the name patterns. For example,
11372 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11375 will look for Ada units in all files with the @file{.ada} extension,
11376 except those whose names end with @file{_nt.ada}.
11380 @node Examples of gnatname Usage
11381 @section Examples of @code{gnatname} Usage
11385 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11391 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11396 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11397 and be writable. In addition, the directory
11398 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11399 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11402 Note the optional spaces after @option{-c} and @option{-d}.
11407 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11408 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11411 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11412 /EXCLUDED_PATTERN=*_nt_body.ada
11413 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11414 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11418 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11419 even in conjunction with one or several switches
11420 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11421 are used in this example.
11423 @c *****************************************
11424 @c * G N A T P r o j e c t M a n a g e r *
11425 @c *****************************************
11426 @node GNAT Project Manager
11427 @chapter GNAT Project Manager
11431 * Examples of Project Files::
11432 * Project File Syntax::
11433 * Objects and Sources in Project Files::
11434 * Importing Projects::
11435 * Project Extension::
11436 * Project Hierarchy Extension::
11437 * External References in Project Files::
11438 * Packages in Project Files::
11439 * Variables from Imported Projects::
11441 * Library Projects::
11442 * Stand-alone Library Projects::
11443 * Switches Related to Project Files::
11444 * Tools Supporting Project Files::
11445 * An Extended Example::
11446 * Project File Complete Syntax::
11449 @c ****************
11450 @c * Introduction *
11451 @c ****************
11454 @section Introduction
11457 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11458 you to manage complex builds involving a number of source files, directories,
11459 and compilation options for different system configurations. In particular,
11460 project files allow you to specify:
11463 The directory or set of directories containing the source files, and/or the
11464 names of the specific source files themselves
11466 The directory in which the compiler's output
11467 (@file{ALI} files, object files, tree files) is to be placed
11469 The directory in which the executable programs is to be placed
11471 ^Switch^Switch^ settings for any of the project-enabled tools
11472 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11473 @code{gnatfind}); you can apply these settings either globally or to individual
11476 The source files containing the main subprogram(s) to be built
11478 The source programming language(s) (currently Ada and/or C)
11480 Source file naming conventions; you can specify these either globally or for
11481 individual compilation units
11488 @node Project Files
11489 @subsection Project Files
11492 Project files are written in a syntax close to that of Ada, using familiar
11493 notions such as packages, context clauses, declarations, default values,
11494 assignments, and inheritance. Finally, project files can be built
11495 hierarchically from other project files, simplifying complex system
11496 integration and project reuse.
11498 A @dfn{project} is a specific set of values for various compilation properties.
11499 The settings for a given project are described by means of
11500 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11501 Property values in project files are either strings or lists of strings.
11502 Properties that are not explicitly set receive default values. A project
11503 file may interrogate the values of @dfn{external variables} (user-defined
11504 command-line switches or environment variables), and it may specify property
11505 settings conditionally, based on the value of such variables.
11507 In simple cases, a project's source files depend only on other source files
11508 in the same project, or on the predefined libraries. (@emph{Dependence} is
11510 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11511 the Project Manager also allows more sophisticated arrangements,
11512 where the source files in one project depend on source files in other
11516 One project can @emph{import} other projects containing needed source files.
11518 You can organize GNAT projects in a hierarchy: a @emph{child} project
11519 can extend a @emph{parent} project, inheriting the parent's source files and
11520 optionally overriding any of them with alternative versions
11524 More generally, the Project Manager lets you structure large development
11525 efforts into hierarchical subsystems, where build decisions are delegated
11526 to the subsystem level, and thus different compilation environments
11527 (^switch^switch^ settings) used for different subsystems.
11529 The Project Manager is invoked through the
11530 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11531 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11533 There may be zero, one or more spaces between @option{-P} and
11534 @option{@emph{projectfile}}.
11536 If you want to define (on the command line) an external variable that is
11537 queried by the project file, you must use the
11538 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11539 The Project Manager parses and interprets the project file, and drives the
11540 invoked tool based on the project settings.
11542 The Project Manager supports a wide range of development strategies,
11543 for systems of all sizes. Here are some typical practices that are
11547 Using a common set of source files, but generating object files in different
11548 directories via different ^switch^switch^ settings
11550 Using a mostly-shared set of source files, but with different versions of
11555 The destination of an executable can be controlled inside a project file
11556 using the @option{^-o^-o^}
11558 In the absence of such a ^switch^switch^ either inside
11559 the project file or on the command line, any executable files generated by
11560 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11561 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11562 in the object directory of the project.
11564 You can use project files to achieve some of the effects of a source
11565 versioning system (for example, defining separate projects for
11566 the different sets of sources that comprise different releases) but the
11567 Project Manager is independent of any source configuration management tools
11568 that might be used by the developers.
11570 The next section introduces the main features of GNAT's project facility
11571 through a sequence of examples; subsequent sections will present the syntax
11572 and semantics in more detail. A more formal description of the project
11573 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11576 @c *****************************
11577 @c * Examples of Project Files *
11578 @c *****************************
11580 @node Examples of Project Files
11581 @section Examples of Project Files
11583 This section illustrates some of the typical uses of project files and
11584 explains their basic structure and behavior.
11587 * Common Sources with Different ^Switches^Switches^ and Directories::
11588 * Using External Variables::
11589 * Importing Other Projects::
11590 * Extending a Project::
11593 @node Common Sources with Different ^Switches^Switches^ and Directories
11594 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11598 * Specifying the Object Directory::
11599 * Specifying the Exec Directory::
11600 * Project File Packages::
11601 * Specifying ^Switch^Switch^ Settings::
11602 * Main Subprograms::
11603 * Executable File Names::
11604 * Source File Naming Conventions::
11605 * Source Language(s)::
11609 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11610 @file{proc.adb} are in the @file{/common} directory. The file
11611 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11612 package @code{Pack}. We want to compile these source files under two sets
11613 of ^switches^switches^:
11616 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11617 and the @option{^-gnata^-gnata^},
11618 @option{^-gnato^-gnato^},
11619 and @option{^-gnatE^-gnatE^} switches to the
11620 compiler; the compiler's output is to appear in @file{/common/debug}
11622 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11623 to the compiler; the compiler's output is to appear in @file{/common/release}
11627 The GNAT project files shown below, respectively @file{debug.gpr} and
11628 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11641 ^/common/debug^[COMMON.DEBUG]^
11646 ^/common/release^[COMMON.RELEASE]^
11651 Here are the corresponding project files:
11653 @smallexample @c projectfile
11656 for Object_Dir use "debug";
11657 for Main use ("proc");
11660 for ^Default_Switches^Default_Switches^ ("Ada")
11662 for Executable ("proc.adb") use "proc1";
11667 package Compiler is
11668 for ^Default_Switches^Default_Switches^ ("Ada")
11669 use ("-fstack-check",
11672 "^-gnatE^-gnatE^");
11678 @smallexample @c projectfile
11681 for Object_Dir use "release";
11682 for Exec_Dir use ".";
11683 for Main use ("proc");
11685 package Compiler is
11686 for ^Default_Switches^Default_Switches^ ("Ada")
11694 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11695 insensitive), and analogously the project defined by @file{release.gpr} is
11696 @code{"Release"}. For consistency the file should have the same name as the
11697 project, and the project file's extension should be @code{"gpr"}. These
11698 conventions are not required, but a warning is issued if they are not followed.
11700 If the current directory is @file{^/temp^[TEMP]^}, then the command
11702 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11706 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11707 as well as the @code{^proc1^PROC1.EXE^} executable,
11708 using the ^switch^switch^ settings defined in the project file.
11710 Likewise, the command
11712 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11716 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11717 and the @code{^proc^PROC.EXE^}
11718 executable in @file{^/common^[COMMON]^},
11719 using the ^switch^switch^ settings from the project file.
11722 @unnumberedsubsubsec Source Files
11725 If a project file does not explicitly specify a set of source directories or
11726 a set of source files, then by default the project's source files are the
11727 Ada source files in the project file directory. Thus @file{pack.ads},
11728 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11730 @node Specifying the Object Directory
11731 @unnumberedsubsubsec Specifying the Object Directory
11734 Several project properties are modeled by Ada-style @emph{attributes};
11735 a property is defined by supplying the equivalent of an Ada attribute
11736 definition clause in the project file.
11737 A project's object directory is another such a property; the corresponding
11738 attribute is @code{Object_Dir}, and its value is also a string expression,
11739 specified either as absolute or relative. In the later case,
11740 it is relative to the project file directory. Thus the compiler's
11741 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
11742 (for the @code{Debug} project)
11743 and to @file{^/common/release^[COMMON.RELEASE]^}
11744 (for the @code{Release} project).
11745 If @code{Object_Dir} is not specified, then the default is the project file
11748 @node Specifying the Exec Directory
11749 @unnumberedsubsubsec Specifying the Exec Directory
11752 A project's exec directory is another property; the corresponding
11753 attribute is @code{Exec_Dir}, and its value is also a string expression,
11754 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
11755 then the default is the object directory (which may also be the project file
11756 directory if attribute @code{Object_Dir} is not specified). Thus the executable
11757 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
11758 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
11759 and in @file{^/common^[COMMON]^} for the @code{Release} project.
11761 @node Project File Packages
11762 @unnumberedsubsubsec Project File Packages
11765 A GNAT tool that is integrated with the Project Manager is modeled by a
11766 corresponding package in the project file. In the example above,
11767 The @code{Debug} project defines the packages @code{Builder}
11768 (for @command{gnatmake}) and @code{Compiler};
11769 the @code{Release} project defines only the @code{Compiler} package.
11771 The Ada-like package syntax is not to be taken literally. Although packages in
11772 project files bear a surface resemblance to packages in Ada source code, the
11773 notation is simply a way to convey a grouping of properties for a named
11774 entity. Indeed, the package names permitted in project files are restricted
11775 to a predefined set, corresponding to the project-aware tools, and the contents
11776 of packages are limited to a small set of constructs.
11777 The packages in the example above contain attribute definitions.
11779 @node Specifying ^Switch^Switch^ Settings
11780 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
11783 ^Switch^Switch^ settings for a project-aware tool can be specified through
11784 attributes in the package that corresponds to the tool.
11785 The example above illustrates one of the relevant attributes,
11786 @code{^Default_Switches^Default_Switches^}, which is defined in packages
11787 in both project files.
11788 Unlike simple attributes like @code{Source_Dirs},
11789 @code{^Default_Switches^Default_Switches^} is
11790 known as an @emph{associative array}. When you define this attribute, you must
11791 supply an ``index'' (a literal string), and the effect of the attribute
11792 definition is to set the value of the array at the specified index.
11793 For the @code{^Default_Switches^Default_Switches^} attribute,
11794 the index is a programming language (in our case, Ada),
11795 and the value specified (after @code{use}) must be a list
11796 of string expressions.
11798 The attributes permitted in project files are restricted to a predefined set.
11799 Some may appear at project level, others in packages.
11800 For any attribute that is an associative array, the index must always be a
11801 literal string, but the restrictions on this string (e.g., a file name or a
11802 language name) depend on the individual attribute.
11803 Also depending on the attribute, its specified value will need to be either a
11804 string or a string list.
11806 In the @code{Debug} project, we set the switches for two tools,
11807 @command{gnatmake} and the compiler, and thus we include the two corresponding
11808 packages; each package defines the @code{^Default_Switches^Default_Switches^}
11809 attribute with index @code{"Ada"}.
11810 Note that the package corresponding to
11811 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
11812 similar, but only includes the @code{Compiler} package.
11814 In project @code{Debug} above, the ^switches^switches^ starting with
11815 @option{-gnat} that are specified in package @code{Compiler}
11816 could have been placed in package @code{Builder}, since @command{gnatmake}
11817 transmits all such ^switches^switches^ to the compiler.
11819 @node Main Subprograms
11820 @unnumberedsubsubsec Main Subprograms
11823 One of the specifiable properties of a project is a list of files that contain
11824 main subprograms. This property is captured in the @code{Main} attribute,
11825 whose value is a list of strings. If a project defines the @code{Main}
11826 attribute, it is not necessary to identify the main subprogram(s) when
11827 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
11829 @node Executable File Names
11830 @unnumberedsubsubsec Executable File Names
11833 By default, the executable file name corresponding to a main source is
11834 deduced from the main source file name. Through the attributes
11835 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
11836 it is possible to change this default.
11837 In project @code{Debug} above, the executable file name
11838 for main source @file{^proc.adb^PROC.ADB^} is
11839 @file{^proc1^PROC1.EXE^}.
11840 Attribute @code{Executable_Suffix}, when specified, may change the suffix
11841 of the executable files, when no attribute @code{Executable} applies:
11842 its value replace the platform-specific executable suffix.
11843 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
11844 specify a non-default executable file name when several mains are built at once
11845 in a single @command{gnatmake} command.
11847 @node Source File Naming Conventions
11848 @unnumberedsubsubsec Source File Naming Conventions
11851 Since the project files above do not specify any source file naming
11852 conventions, the GNAT defaults are used. The mechanism for defining source
11853 file naming conventions -- a package named @code{Naming} --
11854 is described below (@pxref{Naming Schemes}).
11856 @node Source Language(s)
11857 @unnumberedsubsubsec Source Language(s)
11860 Since the project files do not specify a @code{Languages} attribute, by
11861 default the GNAT tools assume that the language of the project file is Ada.
11862 More generally, a project can comprise source files
11863 in Ada, C, and/or other languages.
11865 @node Using External Variables
11866 @subsection Using External Variables
11869 Instead of supplying different project files for debug and release, we can
11870 define a single project file that queries an external variable (set either
11871 on the command line or via an ^environment variable^logical name^) in order to
11872 conditionally define the appropriate settings. Again, assume that the
11873 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
11874 located in directory @file{^/common^[COMMON]^}. The following project file,
11875 @file{build.gpr}, queries the external variable named @code{STYLE} and
11876 defines an object directory and ^switch^switch^ settings based on whether
11877 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
11878 the default is @code{"deb"}.
11880 @smallexample @c projectfile
11883 for Main use ("proc");
11885 type Style_Type is ("deb", "rel");
11886 Style : Style_Type := external ("STYLE", "deb");
11890 for Object_Dir use "debug";
11893 for Object_Dir use "release";
11894 for Exec_Dir use ".";
11903 for ^Default_Switches^Default_Switches^ ("Ada")
11905 for Executable ("proc") use "proc1";
11914 package Compiler is
11918 for ^Default_Switches^Default_Switches^ ("Ada")
11919 use ("^-gnata^-gnata^",
11921 "^-gnatE^-gnatE^");
11924 for ^Default_Switches^Default_Switches^ ("Ada")
11935 @code{Style_Type} is an example of a @emph{string type}, which is the project
11936 file analog of an Ada enumeration type but whose components are string literals
11937 rather than identifiers. @code{Style} is declared as a variable of this type.
11939 The form @code{external("STYLE", "deb")} is known as an
11940 @emph{external reference}; its first argument is the name of an
11941 @emph{external variable}, and the second argument is a default value to be
11942 used if the external variable doesn't exist. You can define an external
11943 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
11944 or you can use ^an environment variable^a logical name^
11945 as an external variable.
11947 Each @code{case} construct is expanded by the Project Manager based on the
11948 value of @code{Style}. Thus the command
11951 gnatmake -P/common/build.gpr -XSTYLE=deb
11957 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
11962 is equivalent to the @command{gnatmake} invocation using the project file
11963 @file{debug.gpr} in the earlier example. So is the command
11965 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
11969 since @code{"deb"} is the default for @code{STYLE}.
11975 gnatmake -P/common/build.gpr -XSTYLE=rel
11981 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
11986 is equivalent to the @command{gnatmake} invocation using the project file
11987 @file{release.gpr} in the earlier example.
11989 @node Importing Other Projects
11990 @subsection Importing Other Projects
11991 @cindex @code{ADA_PROJECT_PATH}
11994 A compilation unit in a source file in one project may depend on compilation
11995 units in source files in other projects. To compile this unit under
11996 control of a project file, the
11997 dependent project must @emph{import} the projects containing the needed source
11999 This effect is obtained using syntax similar to an Ada @code{with} clause,
12000 but where @code{with}ed entities are strings that denote project files.
12002 As an example, suppose that the two projects @code{GUI_Proj} and
12003 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12004 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12005 and @file{^/comm^[COMM]^}, respectively.
12006 Suppose that the source files for @code{GUI_Proj} are
12007 @file{gui.ads} and @file{gui.adb}, and that the source files for
12008 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12009 files is located in its respective project file directory. Schematically:
12028 We want to develop an application in directory @file{^/app^[APP]^} that
12029 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12030 the corresponding project files (e.g.@: the ^switch^switch^ settings
12031 and object directory).
12032 Skeletal code for a main procedure might be something like the following:
12034 @smallexample @c ada
12037 procedure App_Main is
12046 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12049 @smallexample @c projectfile
12051 with "/gui/gui_proj", "/comm/comm_proj";
12052 project App_Proj is
12053 for Main use ("app_main");
12059 Building an executable is achieved through the command:
12061 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12064 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12065 in the directory where @file{app_proj.gpr} resides.
12067 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12068 (as illustrated above) the @code{with} clause can omit the extension.
12070 Our example specified an absolute path for each imported project file.
12071 Alternatively, the directory name of an imported object can be omitted
12075 The imported project file is in the same directory as the importing project
12078 You have defined ^an environment variable^a logical name^
12079 that includes the directory containing
12080 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
12081 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12082 directory names separated by colons (semicolons on Windows).
12086 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12087 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12090 @smallexample @c projectfile
12092 with "gui_proj", "comm_proj";
12093 project App_Proj is
12094 for Main use ("app_main");
12100 Importing other projects can create ambiguities.
12101 For example, the same unit might be present in different imported projects, or
12102 it might be present in both the importing project and in an imported project.
12103 Both of these conditions are errors. Note that in the current version of
12104 the Project Manager, it is illegal to have an ambiguous unit even if the
12105 unit is never referenced by the importing project. This restriction may be
12106 relaxed in a future release.
12108 @node Extending a Project
12109 @subsection Extending a Project
12112 In large software systems it is common to have multiple
12113 implementations of a common interface; in Ada terms, multiple versions of a
12114 package body for the same spec. For example, one implementation
12115 might be safe for use in tasking programs, while another might only be used
12116 in sequential applications. This can be modeled in GNAT using the concept
12117 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12118 another project (the ``parent'') then by default all source files of the
12119 parent project are inherited by the child, but the child project can
12120 override any of the parent's source files with new versions, and can also
12121 add new files. This facility is the project analog of a type extension in
12122 Object-Oriented Programming. Project hierarchies are permitted (a child
12123 project may be the parent of yet another project), and a project that
12124 inherits one project can also import other projects.
12126 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12127 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12128 @file{pack.adb}, and @file{proc.adb}:
12141 Note that the project file can simply be empty (that is, no attribute or
12142 package is defined):
12144 @smallexample @c projectfile
12146 project Seq_Proj is
12152 implying that its source files are all the Ada source files in the project
12155 Suppose we want to supply an alternate version of @file{pack.adb}, in
12156 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12157 @file{pack.ads} and @file{proc.adb}. We can define a project
12158 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12162 ^/tasking^[TASKING]^
12168 project Tasking_Proj extends "/seq/seq_proj" is
12174 The version of @file{pack.adb} used in a build depends on which project file
12177 Note that we could have obtained the desired behavior using project import
12178 rather than project inheritance; a @code{base} project would contain the
12179 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12180 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12181 would import @code{base} and add a different version of @file{pack.adb}. The
12182 choice depends on whether other sources in the original project need to be
12183 overridden. If they do, then project extension is necessary, otherwise,
12184 importing is sufficient.
12187 In a project file that extends another project file, it is possible to
12188 indicate that an inherited source is not part of the sources of the extending
12189 project. This is necessary sometimes when a package spec has been overloaded
12190 and no longer requires a body: in this case, it is necessary to indicate that
12191 the inherited body is not part of the sources of the project, otherwise there
12192 will be a compilation error when compiling the spec.
12194 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12195 Its value is a string list: a list of file names. It is also possible to use
12196 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12197 the file name of a text file containing a list of file names, one per line.
12199 @smallexample @c @projectfile
12200 project B extends "a" is
12201 for Source_Files use ("pkg.ads");
12202 -- New spec of Pkg does not need a completion
12203 for Excluded_Source_Files use ("pkg.adb");
12207 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12208 is still needed: if it is possible to build using @command{gnatmake} when such
12209 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12210 it is possible to remove the source completely from a system that includes
12213 @c ***********************
12214 @c * Project File Syntax *
12215 @c ***********************
12217 @node Project File Syntax
12218 @section Project File Syntax
12222 * Qualified Projects::
12228 * Associative Array Attributes::
12229 * case Constructions::
12233 This section describes the structure of project files.
12235 A project may be an @emph{independent project}, entirely defined by a single
12236 project file. Any Ada source file in an independent project depends only
12237 on the predefined library and other Ada source files in the same project.
12240 A project may also @dfn{depend on} other projects, in either or both of
12241 the following ways:
12243 @item It may import any number of projects
12244 @item It may extend at most one other project
12248 The dependence relation is a directed acyclic graph (the subgraph reflecting
12249 the ``extends'' relation is a tree).
12251 A project's @dfn{immediate sources} are the source files directly defined by
12252 that project, either implicitly by residing in the project file's directory,
12253 or explicitly through any of the source-related attributes described below.
12254 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12255 of @var{proj} together with the immediate sources (unless overridden) of any
12256 project on which @var{proj} depends (either directly or indirectly).
12259 @subsection Basic Syntax
12262 As seen in the earlier examples, project files have an Ada-like syntax.
12263 The minimal project file is:
12264 @smallexample @c projectfile
12273 The identifier @code{Empty} is the name of the project.
12274 This project name must be present after the reserved
12275 word @code{end} at the end of the project file, followed by a semi-colon.
12277 Any name in a project file, such as the project name or a variable name,
12278 has the same syntax as an Ada identifier.
12280 The reserved words of project files are the Ada 95 reserved words plus
12281 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12282 reserved words currently used in project file syntax are:
12318 Comments in project files have the same syntax as in Ada, two consecutive
12319 hyphens through the end of the line.
12321 @node Qualified Projects
12322 @subsection Qualified Projects
12325 Before the reserved @code{project}, there may be one or two "qualifiers", that
12326 is identifiers or other reserved words, to qualify the project.
12328 The current list of qualifiers is:
12332 @code{abstract}: qualify a project with no sources. An abstract project must
12333 have a declaration specifying that there are no sources in the project, and,
12334 if it extends another project, the project it extends must also be a qualified
12338 @code{standard}: a standard project is a non library project with sources.
12341 @code{aggregate}: for future extension
12344 @code{aggregate library}: for future extension
12347 @code{library}: a library project must declare both attributes
12348 @code{Library_Name} and @code{Library_Dir}.
12351 @code{configuration}: a configuration project cannot be in a project tree.
12355 @subsection Packages
12358 A project file may contain @emph{packages}. The name of a package must be one
12359 of the identifiers from the following list. A package
12360 with a given name may only appear once in a project file. Package names are
12361 case insensitive. The following package names are legal:
12377 @code{Cross_Reference}
12381 @code{Pretty_Printer}
12391 @code{Language_Processing}
12395 In its simplest form, a package may be empty:
12397 @smallexample @c projectfile
12407 A package may contain @emph{attribute declarations},
12408 @emph{variable declarations} and @emph{case constructions}, as will be
12411 When there is ambiguity between a project name and a package name,
12412 the name always designates the project. To avoid possible confusion, it is
12413 always a good idea to avoid naming a project with one of the
12414 names allowed for packages or any name that starts with @code{gnat}.
12417 @subsection Expressions
12420 An @emph{expression} is either a @emph{string expression} or a
12421 @emph{string list expression}.
12423 A @emph{string expression} is either a @emph{simple string expression} or a
12424 @emph{compound string expression}.
12426 A @emph{simple string expression} is one of the following:
12428 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12429 @item A string-valued variable reference (@pxref{Variables})
12430 @item A string-valued attribute reference (@pxref{Attributes})
12431 @item An external reference (@pxref{External References in Project Files})
12435 A @emph{compound string expression} is a concatenation of string expressions,
12436 using the operator @code{"&"}
12438 Path & "/" & File_Name & ".ads"
12442 A @emph{string list expression} is either a
12443 @emph{simple string list expression} or a
12444 @emph{compound string list expression}.
12446 A @emph{simple string list expression} is one of the following:
12448 @item A parenthesized list of zero or more string expressions,
12449 separated by commas
12451 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12454 @item A string list-valued variable reference
12455 @item A string list-valued attribute reference
12459 A @emph{compound string list expression} is the concatenation (using
12460 @code{"&"}) of a simple string list expression and an expression. Note that
12461 each term in a compound string list expression, except the first, may be
12462 either a string expression or a string list expression.
12464 @smallexample @c projectfile
12466 File_Name_List := () & File_Name; -- One string in this list
12467 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12469 Big_List := File_Name_List & Extended_File_Name_List;
12470 -- Concatenation of two string lists: three strings
12471 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12472 -- Illegal: must start with a string list
12477 @subsection String Types
12480 A @emph{string type declaration} introduces a discrete set of string literals.
12481 If a string variable is declared to have this type, its value
12482 is restricted to the given set of literals.
12484 Here is an example of a string type declaration:
12486 @smallexample @c projectfile
12487 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12491 Variables of a string type are called @emph{typed variables}; all other
12492 variables are called @emph{untyped variables}. Typed variables are
12493 particularly useful in @code{case} constructions, to support conditional
12494 attribute declarations.
12495 (@pxref{case Constructions}).
12497 The string literals in the list are case sensitive and must all be different.
12498 They may include any graphic characters allowed in Ada, including spaces.
12500 A string type may only be declared at the project level, not inside a package.
12502 A string type may be referenced by its name if it has been declared in the same
12503 project file, or by an expanded name whose prefix is the name of the project
12504 in which it is declared.
12507 @subsection Variables
12510 A variable may be declared at the project file level, or within a package.
12511 Here are some examples of variable declarations:
12513 @smallexample @c projectfile
12515 This_OS : OS := external ("OS"); -- a typed variable declaration
12516 That_OS := "GNU/Linux"; -- an untyped variable declaration
12521 The syntax of a @emph{typed variable declaration} is identical to the Ada
12522 syntax for an object declaration. By contrast, the syntax of an untyped
12523 variable declaration is identical to an Ada assignment statement. In fact,
12524 variable declarations in project files have some of the characteristics of
12525 an assignment, in that successive declarations for the same variable are
12526 allowed. Untyped variable declarations do establish the expected kind of the
12527 variable (string or string list), and successive declarations for it must
12528 respect the initial kind.
12531 A string variable declaration (typed or untyped) declares a variable
12532 whose value is a string. This variable may be used as a string expression.
12533 @smallexample @c projectfile
12534 File_Name := "readme.txt";
12535 Saved_File_Name := File_Name & ".saved";
12539 A string list variable declaration declares a variable whose value is a list
12540 of strings. The list may contain any number (zero or more) of strings.
12542 @smallexample @c projectfile
12544 List_With_One_Element := ("^-gnaty^-gnaty^");
12545 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12546 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12547 "pack2.ada", "util_.ada", "util.ada");
12551 The same typed variable may not be declared more than once at project level,
12552 and it may not be declared more than once in any package; it is in effect
12555 The same untyped variable may be declared several times. Declarations are
12556 elaborated in the order in which they appear, so the new value replaces
12557 the old one, and any subsequent reference to the variable uses the new value.
12558 However, as noted above, if a variable has been declared as a string, all
12560 declarations must give it a string value. Similarly, if a variable has
12561 been declared as a string list, all subsequent declarations
12562 must give it a string list value.
12564 A @emph{variable reference} may take several forms:
12567 @item The simple variable name, for a variable in the current package (if any)
12568 or in the current project
12569 @item An expanded name, whose prefix is a context name.
12573 A @emph{context} may be one of the following:
12576 @item The name of an existing package in the current project
12577 @item The name of an imported project of the current project
12578 @item The name of an ancestor project (i.e., a project extended by the current
12579 project, either directly or indirectly)
12580 @item An expanded name whose prefix is an imported/parent project name, and
12581 whose selector is a package name in that project.
12585 A variable reference may be used in an expression.
12588 @subsection Attributes
12591 A project (and its packages) may have @emph{attributes} that define
12592 the project's properties. Some attributes have values that are strings;
12593 others have values that are string lists.
12595 There are two categories of attributes: @emph{simple attributes}
12596 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12598 Legal project attribute names, and attribute names for each legal package are
12599 listed below. Attributes names are case-insensitive.
12601 The following attributes are defined on projects (all are simple attributes):
12603 @multitable @columnfractions .4 .3
12604 @item @emph{Attribute Name}
12606 @item @code{Source_Files}
12608 @item @code{Source_Dirs}
12610 @item @code{Source_List_File}
12612 @item @code{Object_Dir}
12614 @item @code{Exec_Dir}
12616 @item @code{Excluded_Source_Dirs}
12618 @item @code{Excluded_Source_Files}
12620 @item @code{Excluded_Source_List_File}
12622 @item @code{Languages}
12626 @item @code{Library_Dir}
12628 @item @code{Library_Name}
12630 @item @code{Library_Kind}
12632 @item @code{Library_Version}
12634 @item @code{Library_Interface}
12636 @item @code{Library_Auto_Init}
12638 @item @code{Library_Options}
12640 @item @code{Library_Src_Dir}
12642 @item @code{Library_ALI_Dir}
12644 @item @code{Library_GCC}
12646 @item @code{Library_Symbol_File}
12648 @item @code{Library_Symbol_Policy}
12650 @item @code{Library_Reference_Symbol_File}
12652 @item @code{Externally_Built}
12657 The following attributes are defined for package @code{Naming}
12658 (@pxref{Naming Schemes}):
12660 @multitable @columnfractions .4 .2 .2 .2
12661 @item Attribute Name @tab Category @tab Index @tab Value
12662 @item @code{Spec_Suffix}
12663 @tab associative array
12666 @item @code{Body_Suffix}
12667 @tab associative array
12670 @item @code{Separate_Suffix}
12671 @tab simple attribute
12674 @item @code{Casing}
12675 @tab simple attribute
12678 @item @code{Dot_Replacement}
12679 @tab simple attribute
12683 @tab associative array
12687 @tab associative array
12690 @item @code{Specification_Exceptions}
12691 @tab associative array
12694 @item @code{Implementation_Exceptions}
12695 @tab associative array
12701 The following attributes are defined for packages @code{Builder},
12702 @code{Compiler}, @code{Binder},
12703 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12704 (@pxref{^Switches^Switches^ and Project Files}).
12706 @multitable @columnfractions .4 .2 .2 .2
12707 @item Attribute Name @tab Category @tab Index @tab Value
12708 @item @code{^Default_Switches^Default_Switches^}
12709 @tab associative array
12712 @item @code{^Switches^Switches^}
12713 @tab associative array
12719 In addition, package @code{Compiler} has a single string attribute
12720 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12721 string attribute @code{Global_Configuration_Pragmas}.
12724 Each simple attribute has a default value: the empty string (for string-valued
12725 attributes) and the empty list (for string list-valued attributes).
12727 An attribute declaration defines a new value for an attribute.
12729 Examples of simple attribute declarations:
12731 @smallexample @c projectfile
12732 for Object_Dir use "objects";
12733 for Source_Dirs use ("units", "test/drivers");
12737 The syntax of a @dfn{simple attribute declaration} is similar to that of an
12738 attribute definition clause in Ada.
12740 Attributes references may be appear in expressions.
12741 The general form for such a reference is @code{<entity>'<attribute>}:
12742 Associative array attributes are functions. Associative
12743 array attribute references must have an argument that is a string literal.
12747 @smallexample @c projectfile
12749 Naming'Dot_Replacement
12750 Imported_Project'Source_Dirs
12751 Imported_Project.Naming'Casing
12752 Builder'^Default_Switches^Default_Switches^("Ada")
12756 The prefix of an attribute may be:
12758 @item @code{project} for an attribute of the current project
12759 @item The name of an existing package of the current project
12760 @item The name of an imported project
12761 @item The name of a parent project that is extended by the current project
12762 @item An expanded name whose prefix is imported/parent project name,
12763 and whose selector is a package name
12768 @smallexample @c projectfile
12771 for Source_Dirs use project'Source_Dirs & "units";
12772 for Source_Dirs use project'Source_Dirs & "test/drivers"
12778 In the first attribute declaration, initially the attribute @code{Source_Dirs}
12779 has the default value: an empty string list. After this declaration,
12780 @code{Source_Dirs} is a string list of one element: @code{"units"}.
12781 After the second attribute declaration @code{Source_Dirs} is a string list of
12782 two elements: @code{"units"} and @code{"test/drivers"}.
12784 Note: this example is for illustration only. In practice,
12785 the project file would contain only one attribute declaration:
12787 @smallexample @c projectfile
12788 for Source_Dirs use ("units", "test/drivers");
12791 @node Associative Array Attributes
12792 @subsection Associative Array Attributes
12795 Some attributes are defined as @emph{associative arrays}. An associative
12796 array may be regarded as a function that takes a string as a parameter
12797 and delivers a string or string list value as its result.
12799 Here are some examples of single associative array attribute associations:
12801 @smallexample @c projectfile
12802 for Body ("main") use "Main.ada";
12803 for ^Switches^Switches^ ("main.ada")
12805 "^-gnatv^-gnatv^");
12806 for ^Switches^Switches^ ("main.ada")
12807 use Builder'^Switches^Switches^ ("main.ada")
12812 Like untyped variables and simple attributes, associative array attributes
12813 may be declared several times. Each declaration supplies a new value for the
12814 attribute, and replaces the previous setting.
12817 An associative array attribute may be declared as a full associative array
12818 declaration, with the value of the same attribute in an imported or extended
12821 @smallexample @c projectfile
12823 for Default_Switches use Default.Builder'Default_Switches;
12828 In this example, @code{Default} must be either a project imported by the
12829 current project, or the project that the current project extends. If the
12830 attribute is in a package (in this case, in package @code{Builder}), the same
12831 package needs to be specified.
12834 A full associative array declaration replaces any other declaration for the
12835 attribute, including other full associative array declaration. Single
12836 associative array associations may be declare after a full associative
12837 declaration, modifying the value for a single association of the attribute.
12839 @node case Constructions
12840 @subsection @code{case} Constructions
12843 A @code{case} construction is used in a project file to effect conditional
12845 Here is a typical example:
12847 @smallexample @c projectfile
12850 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
12852 OS : OS_Type := external ("OS", "GNU/Linux");
12856 package Compiler is
12858 when "GNU/Linux" | "Unix" =>
12859 for ^Default_Switches^Default_Switches^ ("Ada")
12860 use ("^-gnath^-gnath^");
12862 for ^Default_Switches^Default_Switches^ ("Ada")
12863 use ("^-gnatP^-gnatP^");
12872 The syntax of a @code{case} construction is based on the Ada case statement
12873 (although there is no @code{null} construction for empty alternatives).
12875 The case expression must be a typed string variable.
12876 Each alternative comprises the reserved word @code{when}, either a list of
12877 literal strings separated by the @code{"|"} character or the reserved word
12878 @code{others}, and the @code{"=>"} token.
12879 Each literal string must belong to the string type that is the type of the
12881 An @code{others} alternative, if present, must occur last.
12883 After each @code{=>}, there are zero or more constructions. The only
12884 constructions allowed in a case construction are other case constructions,
12885 attribute declarations and variable declarations. String type declarations and
12886 package declarations are not allowed. Variable declarations are restricted to
12887 variables that have already been declared before the case construction.
12889 The value of the case variable is often given by an external reference
12890 (@pxref{External References in Project Files}).
12892 @c ****************************************
12893 @c * Objects and Sources in Project Files *
12894 @c ****************************************
12896 @node Objects and Sources in Project Files
12897 @section Objects and Sources in Project Files
12900 * Object Directory::
12902 * Source Directories::
12903 * Source File Names::
12907 Each project has exactly one object directory and one or more source
12908 directories. The source directories must contain at least one source file,
12909 unless the project file explicitly specifies that no source files are present
12910 (@pxref{Source File Names}).
12912 @node Object Directory
12913 @subsection Object Directory
12916 The object directory for a project is the directory containing the compiler's
12917 output (such as @file{ALI} files and object files) for the project's immediate
12920 The object directory is given by the value of the attribute @code{Object_Dir}
12921 in the project file.
12923 @smallexample @c projectfile
12924 for Object_Dir use "objects";
12928 The attribute @code{Object_Dir} has a string value, the path name of the object
12929 directory. The path name may be absolute or relative to the directory of the
12930 project file. This directory must already exist, and be readable and writable.
12932 By default, when the attribute @code{Object_Dir} is not given an explicit value
12933 or when its value is the empty string, the object directory is the same as the
12934 directory containing the project file.
12936 @node Exec Directory
12937 @subsection Exec Directory
12940 The exec directory for a project is the directory containing the executables
12941 for the project's main subprograms.
12943 The exec directory is given by the value of the attribute @code{Exec_Dir}
12944 in the project file.
12946 @smallexample @c projectfile
12947 for Exec_Dir use "executables";
12951 The attribute @code{Exec_Dir} has a string value, the path name of the exec
12952 directory. The path name may be absolute or relative to the directory of the
12953 project file. This directory must already exist, and be writable.
12955 By default, when the attribute @code{Exec_Dir} is not given an explicit value
12956 or when its value is the empty string, the exec directory is the same as the
12957 object directory of the project file.
12959 @node Source Directories
12960 @subsection Source Directories
12963 The source directories of a project are specified by the project file
12964 attribute @code{Source_Dirs}.
12966 This attribute's value is a string list. If the attribute is not given an
12967 explicit value, then there is only one source directory, the one where the
12968 project file resides.
12970 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
12973 @smallexample @c projectfile
12974 for Source_Dirs use ();
12978 indicates that the project contains no source files.
12980 Otherwise, each string in the string list designates one or more
12981 source directories.
12983 @smallexample @c projectfile
12984 for Source_Dirs use ("sources", "test/drivers");
12988 If a string in the list ends with @code{"/**"}, then the directory whose path
12989 name precedes the two asterisks, as well as all its subdirectories
12990 (recursively), are source directories.
12992 @smallexample @c projectfile
12993 for Source_Dirs use ("/system/sources/**");
12997 Here the directory @code{/system/sources} and all of its subdirectories
12998 (recursively) are source directories.
13000 To specify that the source directories are the directory of the project file
13001 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13002 @smallexample @c projectfile
13003 for Source_Dirs use ("./**");
13007 Each of the source directories must exist and be readable.
13009 @node Source File Names
13010 @subsection Source File Names
13013 In a project that contains source files, their names may be specified by the
13014 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13015 (a string). Source file names never include any directory information.
13017 If the attribute @code{Source_Files} is given an explicit value, then each
13018 element of the list is a source file name.
13020 @smallexample @c projectfile
13021 for Source_Files use ("main.adb");
13022 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13026 If the attribute @code{Source_Files} is not given an explicit value,
13027 but the attribute @code{Source_List_File} is given a string value,
13028 then the source file names are contained in the text file whose path name
13029 (absolute or relative to the directory of the project file) is the
13030 value of the attribute @code{Source_List_File}.
13032 Each line in the file that is not empty or is not a comment
13033 contains a source file name.
13035 @smallexample @c projectfile
13036 for Source_List_File use "source_list.txt";
13040 By default, if neither the attribute @code{Source_Files} nor the attribute
13041 @code{Source_List_File} is given an explicit value, then each file in the
13042 source directories that conforms to the project's naming scheme
13043 (@pxref{Naming Schemes}) is an immediate source of the project.
13045 A warning is issued if both attributes @code{Source_Files} and
13046 @code{Source_List_File} are given explicit values. In this case, the attribute
13047 @code{Source_Files} prevails.
13049 Each source file name must be the name of one existing source file
13050 in one of the source directories.
13052 A @code{Source_Files} attribute whose value is an empty list
13053 indicates that there are no source files in the project.
13055 If the order of the source directories is known statically, that is if
13056 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13057 be several files with the same source file name. In this case, only the file
13058 in the first directory is considered as an immediate source of the project
13059 file. If the order of the source directories is not known statically, it is
13060 an error to have several files with the same source file name.
13062 Projects can be specified to have no Ada source
13063 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
13064 list, or the @code{"Ada"} may be absent from @code{Languages}:
13066 @smallexample @c projectfile
13067 for Source_Dirs use ();
13068 for Source_Files use ();
13069 for Languages use ("C", "C++");
13073 Otherwise, a project must contain at least one immediate source.
13075 Projects with no source files are useful as template packages
13076 (@pxref{Packages in Project Files}) for other projects; in particular to
13077 define a package @code{Naming} (@pxref{Naming Schemes}).
13079 @c ****************************
13080 @c * Importing Projects *
13081 @c ****************************
13083 @node Importing Projects
13084 @section Importing Projects
13085 @cindex @code{ADA_PROJECT_PATH}
13088 An immediate source of a project P may depend on source files that
13089 are neither immediate sources of P nor in the predefined library.
13090 To get this effect, P must @emph{import} the projects that contain the needed
13093 @smallexample @c projectfile
13095 with "project1", "utilities.gpr";
13096 with "/namings/apex.gpr";
13103 As can be seen in this example, the syntax for importing projects is similar
13104 to the syntax for importing compilation units in Ada. However, project files
13105 use literal strings instead of names, and the @code{with} clause identifies
13106 project files rather than packages.
13108 Each literal string is the file name or path name (absolute or relative) of a
13109 project file. If a string corresponds to a file name, with no path or a
13110 relative path, then its location is determined by the @emph{project path}. The
13111 latter can be queried using @code{gnatls -v}. It contains:
13115 In first position, the directory containing the current project file.
13117 In last position, the default project directory. This default project directory
13118 is part of the GNAT installation and is the standard place to install project
13119 files giving access to standard support libraries.
13121 @ref{Installing a library}
13125 In between, all the directories referenced in the
13126 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13130 If a relative pathname is used, as in
13132 @smallexample @c projectfile
13137 then the full path for the project is constructed by concatenating this
13138 relative path to those in the project path, in order, until a matching file is
13139 found. Any symbolic link will be fully resolved in the directory of the
13140 importing project file before the imported project file is examined.
13142 If the @code{with}'ed project file name does not have an extension,
13143 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13144 then the file name as specified in the @code{with} clause (no extension) will
13145 be used. In the above example, if a file @code{project1.gpr} is found, then it
13146 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13147 then it will be used; if neither file exists, this is an error.
13149 A warning is issued if the name of the project file does not match the
13150 name of the project; this check is case insensitive.
13152 Any source file that is an immediate source of the imported project can be
13153 used by the immediate sources of the importing project, transitively. Thus
13154 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13155 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13156 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13157 because if and when @code{B} ceases to import @code{C}, some sources in
13158 @code{A} will no longer compile.
13160 A side effect of this capability is that normally cyclic dependencies are not
13161 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13162 is not allowed to import @code{A}. However, there are cases when cyclic
13163 dependencies would be beneficial. For these cases, another form of import
13164 between projects exists, the @code{limited with}: a project @code{A} that
13165 imports a project @code{B} with a straight @code{with} may also be imported,
13166 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13167 to @code{A} include at least one @code{limited with}.
13169 @smallexample @c 0projectfile
13175 limited with "../a/a.gpr";
13183 limited with "../a/a.gpr";
13189 In the above legal example, there are two project cycles:
13192 @item A -> C -> D -> A
13196 In each of these cycle there is one @code{limited with}: import of @code{A}
13197 from @code{B} and import of @code{A} from @code{D}.
13199 The difference between straight @code{with} and @code{limited with} is that
13200 the name of a project imported with a @code{limited with} cannot be used in the
13201 project that imports it. In particular, its packages cannot be renamed and
13202 its variables cannot be referred to.
13204 An exception to the above rules for @code{limited with} is that for the main
13205 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13206 @code{limited with} is equivalent to a straight @code{with}. For example,
13207 in the example above, projects @code{B} and @code{D} could not be main
13208 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13209 each have a @code{limited with} that is the only one in a cycle of importing
13212 @c *********************
13213 @c * Project Extension *
13214 @c *********************
13216 @node Project Extension
13217 @section Project Extension
13220 During development of a large system, it is sometimes necessary to use
13221 modified versions of some of the source files, without changing the original
13222 sources. This can be achieved through the @emph{project extension} facility.
13224 @smallexample @c projectfile
13225 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13229 A project extension declaration introduces an extending project
13230 (the @emph{child}) and a project being extended (the @emph{parent}).
13232 By default, a child project inherits all the sources of its parent.
13233 However, inherited sources can be overridden: a unit in a parent is hidden
13234 by a unit of the same name in the child.
13236 Inherited sources are considered to be sources (but not immediate sources)
13237 of the child project; see @ref{Project File Syntax}.
13239 An inherited source file retains any switches specified in the parent project.
13241 For example if the project @code{Utilities} contains the spec and the
13242 body of an Ada package @code{Util_IO}, then the project
13243 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13244 The original body of @code{Util_IO} will not be considered in program builds.
13245 However, the package spec will still be found in the project
13248 A child project can have only one parent, except when it is qualified as
13249 abstract. But it may import any number of other projects.
13251 A project is not allowed to import directly or indirectly at the same time a
13252 child project and any of its ancestors.
13254 @c *******************************
13255 @c * Project Hierarchy Extension *
13256 @c *******************************
13258 @node Project Hierarchy Extension
13259 @section Project Hierarchy Extension
13262 When extending a large system spanning multiple projects, it is often
13263 inconvenient to extend every project in the hierarchy that is impacted by a
13264 small change introduced. In such cases, it is possible to create a virtual
13265 extension of entire hierarchy using @code{extends all} relationship.
13267 When the project is extended using @code{extends all} inheritance, all projects
13268 that are imported by it, both directly and indirectly, are considered virtually
13269 extended. That is, the Project Manager creates "virtual projects"
13270 that extend every project in the hierarchy; all these virtual projects have
13271 no sources of their own and have as object directory the object directory of
13272 the root of "extending all" project.
13274 It is possible to explicitly extend one or more projects in the hierarchy
13275 in order to modify the sources. These extending projects must be imported by
13276 the "extending all" project, which will replace the corresponding virtual
13277 projects with the explicit ones.
13279 When building such a project hierarchy extension, the Project Manager will
13280 ensure that both modified sources and sources in virtual extending projects
13281 that depend on them, are recompiled.
13283 By means of example, consider the following hierarchy of projects.
13287 project A, containing package P1
13289 project B importing A and containing package P2 which depends on P1
13291 project C importing B and containing package P3 which depends on P2
13295 We want to modify packages P1 and P3.
13297 This project hierarchy will need to be extended as follows:
13301 Create project A1 that extends A, placing modified P1 there:
13303 @smallexample @c 0projectfile
13304 project A1 extends "(@dots{})/A" is
13309 Create project C1 that "extends all" C and imports A1, placing modified
13312 @smallexample @c 0projectfile
13313 with "(@dots{})/A1";
13314 project C1 extends all "(@dots{})/C" is
13319 When you build project C1, your entire modified project space will be
13320 recompiled, including the virtual project B1 that has been impacted by the
13321 "extending all" inheritance of project C.
13323 Note that if a Library Project in the hierarchy is virtually extended,
13324 the virtual project that extends the Library Project is not a Library Project.
13326 @c ****************************************
13327 @c * External References in Project Files *
13328 @c ****************************************
13330 @node External References in Project Files
13331 @section External References in Project Files
13334 A project file may contain references to external variables; such references
13335 are called @emph{external references}.
13337 An external variable is either defined as part of the environment (an
13338 environment variable in Unix, for example) or else specified on the command
13339 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13340 If both, then the command line value is used.
13342 The value of an external reference is obtained by means of the built-in
13343 function @code{external}, which returns a string value.
13344 This function has two forms:
13346 @item @code{external (external_variable_name)}
13347 @item @code{external (external_variable_name, default_value)}
13351 Each parameter must be a string literal. For example:
13353 @smallexample @c projectfile
13355 external ("OS", "GNU/Linux")
13359 In the form with one parameter, the function returns the value of
13360 the external variable given as parameter. If this name is not present in the
13361 environment, the function returns an empty string.
13363 In the form with two string parameters, the second argument is
13364 the value returned when the variable given as the first argument is not
13365 present in the environment. In the example above, if @code{"OS"} is not
13366 the name of ^an environment variable^a logical name^ and is not passed on
13367 the command line, then the returned value is @code{"GNU/Linux"}.
13369 An external reference may be part of a string expression or of a string
13370 list expression, and can therefore appear in a variable declaration or
13371 an attribute declaration.
13373 @smallexample @c projectfile
13375 type Mode_Type is ("Debug", "Release");
13376 Mode : Mode_Type := external ("MODE");
13383 @c *****************************
13384 @c * Packages in Project Files *
13385 @c *****************************
13387 @node Packages in Project Files
13388 @section Packages in Project Files
13391 A @emph{package} defines the settings for project-aware tools within a
13393 For each such tool one can declare a package; the names for these
13394 packages are preset (@pxref{Packages}).
13395 A package may contain variable declarations, attribute declarations, and case
13398 @smallexample @c projectfile
13401 package Builder is -- used by gnatmake
13402 for ^Default_Switches^Default_Switches^ ("Ada")
13411 The syntax of package declarations mimics that of package in Ada.
13413 Most of the packages have an attribute
13414 @code{^Default_Switches^Default_Switches^}.
13415 This attribute is an associative array, and its value is a string list.
13416 The index of the associative array is the name of a programming language (case
13417 insensitive). This attribute indicates the ^switch^switch^
13418 or ^switches^switches^ to be used
13419 with the corresponding tool.
13421 Some packages also have another attribute, @code{^Switches^Switches^},
13422 an associative array whose value is a string list.
13423 The index is the name of a source file.
13424 This attribute indicates the ^switch^switch^
13425 or ^switches^switches^ to be used by the corresponding
13426 tool when dealing with this specific file.
13428 Further information on these ^switch^switch^-related attributes is found in
13429 @ref{^Switches^Switches^ and Project Files}.
13431 A package may be declared as a @emph{renaming} of another package; e.g., from
13432 the project file for an imported project.
13434 @smallexample @c projectfile
13436 with "/global/apex.gpr";
13438 package Naming renames Apex.Naming;
13445 Packages that are renamed in other project files often come from project files
13446 that have no sources: they are just used as templates. Any modification in the
13447 template will be reflected automatically in all the project files that rename
13448 a package from the template.
13450 In addition to the tool-oriented packages, you can also declare a package
13451 named @code{Naming} to establish specialized source file naming conventions
13452 (@pxref{Naming Schemes}).
13454 @c ************************************
13455 @c * Variables from Imported Projects *
13456 @c ************************************
13458 @node Variables from Imported Projects
13459 @section Variables from Imported Projects
13462 An attribute or variable defined in an imported or parent project can
13463 be used in expressions in the importing / extending project.
13464 Such an attribute or variable is denoted by an expanded name whose prefix
13465 is either the name of the project or the expanded name of a package within
13468 @smallexample @c projectfile
13471 project Main extends "base" is
13472 Var1 := Imported.Var;
13473 Var2 := Base.Var & ".new";
13478 for ^Default_Switches^Default_Switches^ ("Ada")
13479 use Imported.Builder'Ada_^Switches^Switches^ &
13480 "^-gnatg^-gnatg^" &
13486 package Compiler is
13487 for ^Default_Switches^Default_Switches^ ("Ada")
13488 use Base.Compiler'Ada_^Switches^Switches^;
13499 The value of @code{Var1} is a copy of the variable @code{Var} defined
13500 in the project file @file{"imported.gpr"}
13502 the value of @code{Var2} is a copy of the value of variable @code{Var}
13503 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13505 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13506 @code{Builder} is a string list that includes in its value a copy of the value
13507 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13508 in project file @file{imported.gpr} plus two new elements:
13509 @option{"^-gnatg^-gnatg^"}
13510 and @option{"^-v^-v^"};
13512 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13513 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13514 defined in the @code{Compiler} package in project file @file{base.gpr},
13515 the project being extended.
13518 @c ******************
13519 @c * Naming Schemes *
13520 @c ******************
13522 @node Naming Schemes
13523 @section Naming Schemes
13526 Sometimes an Ada software system is ported from a foreign compilation
13527 environment to GNAT, and the file names do not use the default GNAT
13528 conventions. Instead of changing all the file names (which for a variety
13529 of reasons might not be possible), you can define the relevant file
13530 naming scheme in the @code{Naming} package in your project file.
13533 Note that the use of pragmas described in
13534 @ref{Alternative File Naming Schemes} by mean of a configuration
13535 pragmas file is not supported when using project files. You must use
13536 the features described in this paragraph. You can however use specify
13537 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13540 For example, the following
13541 package models the Apex file naming rules:
13543 @smallexample @c projectfile
13546 for Casing use "lowercase";
13547 for Dot_Replacement use ".";
13548 for Spec_Suffix ("Ada") use ".1.ada";
13549 for Body_Suffix ("Ada") use ".2.ada";
13556 For example, the following package models the HP Ada file naming rules:
13558 @smallexample @c projectfile
13561 for Casing use "lowercase";
13562 for Dot_Replacement use "__";
13563 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13564 for Body_Suffix ("Ada") use ".^ada^ada^";
13570 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13571 names in lower case)
13575 You can define the following attributes in package @code{Naming}:
13579 @item @code{Casing}
13580 This must be a string with one of the three values @code{"lowercase"},
13581 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13584 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13586 @item @code{Dot_Replacement}
13587 This must be a string whose value satisfies the following conditions:
13590 @item It must not be empty
13591 @item It cannot start or end with an alphanumeric character
13592 @item It cannot be a single underscore
13593 @item It cannot start with an underscore followed by an alphanumeric
13594 @item It cannot contain a dot @code{'.'} except if the entire string
13599 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13601 @item @code{Spec_Suffix}
13602 This is an associative array (indexed by the programming language name, case
13603 insensitive) whose value is a string that must satisfy the following
13607 @item It must not be empty
13608 @item It must include at least one dot
13611 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13612 @code{"^.ads^.ADS^"}.
13614 @item @code{Body_Suffix}
13615 This is an associative array (indexed by the programming language name, case
13616 insensitive) whose value is a string that must satisfy the following
13620 @item It must not be empty
13621 @item It must include at least one dot
13622 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13625 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13626 same string, then a file name that ends with the longest of these two suffixes
13627 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13628 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13630 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13631 @code{"^.adb^.ADB^"}.
13633 @item @code{Separate_Suffix}
13634 This must be a string whose value satisfies the same conditions as
13635 @code{Body_Suffix}. The same "longest suffix" rules apply.
13638 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13639 value as @code{Body_Suffix ("Ada")}.
13643 You can use the associative array attribute @code{Spec} to define
13644 the source file name for an individual Ada compilation unit's spec. The array
13645 index must be a string literal that identifies the Ada unit (case insensitive).
13646 The value of this attribute must be a string that identifies the file that
13647 contains this unit's spec (case sensitive or insensitive depending on the
13650 @smallexample @c projectfile
13651 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13656 You can use the associative array attribute @code{Body} to
13657 define the source file name for an individual Ada compilation unit's body
13658 (possibly a subunit). The array index must be a string literal that identifies
13659 the Ada unit (case insensitive). The value of this attribute must be a string
13660 that identifies the file that contains this unit's body or subunit (case
13661 sensitive or insensitive depending on the operating system).
13663 @smallexample @c projectfile
13664 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13668 @c ********************
13669 @c * Library Projects *
13670 @c ********************
13672 @node Library Projects
13673 @section Library Projects
13676 @emph{Library projects} are projects whose object code is placed in a library.
13677 (Note that this facility is not yet supported on all platforms)
13679 To create a library project, you need to define in its project file
13680 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13681 Additionally, you may define other library-related attributes such as
13682 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13683 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13685 The @code{Library_Name} attribute has a string value. There is no restriction
13686 on the name of a library. It is the responsibility of the developer to
13687 choose a name that will be accepted by the platform. It is recommended to
13688 choose names that could be Ada identifiers; such names are almost guaranteed
13689 to be acceptable on all platforms.
13691 The @code{Library_Dir} attribute has a string value that designates the path
13692 (absolute or relative) of the directory where the library will reside.
13693 It must designate an existing directory, and this directory must be writable,
13694 different from the project's object directory and from any source directory
13695 in the project tree.
13697 If both @code{Library_Name} and @code{Library_Dir} are specified and
13698 are legal, then the project file defines a library project. The optional
13699 library-related attributes are checked only for such project files.
13701 The @code{Library_Kind} attribute has a string value that must be one of the
13702 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13703 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13704 attribute is not specified, the library is a static library, that is
13705 an archive of object files that can be potentially linked into a
13706 static executable. Otherwise, the library may be dynamic or
13707 relocatable, that is a library that is loaded only at the start of execution.
13709 If you need to build both a static and a dynamic library, you should use two
13710 different object directories, since in some cases some extra code needs to
13711 be generated for the latter. For such cases, it is recommended to either use
13712 two different project files, or a single one which uses external variables
13713 to indicate what kind of library should be build.
13715 The @code{Library_ALI_Dir} attribute may be specified to indicate the
13716 directory where the ALI files of the library will be copied. When it is
13717 not specified, the ALI files are copied to the directory specified in
13718 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
13719 must be writable and different from the project's object directory and from
13720 any source directory in the project tree.
13722 The @code{Library_Version} attribute has a string value whose interpretation
13723 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
13724 used only for dynamic/relocatable libraries as the internal name of the
13725 library (the @code{"soname"}). If the library file name (built from the
13726 @code{Library_Name}) is different from the @code{Library_Version}, then the
13727 library file will be a symbolic link to the actual file whose name will be
13728 @code{Library_Version}.
13732 @smallexample @c projectfile
13738 for Library_Dir use "lib_dir";
13739 for Library_Name use "dummy";
13740 for Library_Kind use "relocatable";
13741 for Library_Version use "libdummy.so." & Version;
13748 Directory @file{lib_dir} will contain the internal library file whose name
13749 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
13750 @file{libdummy.so.1}.
13752 When @command{gnatmake} detects that a project file
13753 is a library project file, it will check all immediate sources of the project
13754 and rebuild the library if any of the sources have been recompiled.
13756 Standard project files can import library project files. In such cases,
13757 the libraries will only be rebuilt if some of its sources are recompiled
13758 because they are in the closure of some other source in an importing project.
13759 Sources of the library project files that are not in such a closure will
13760 not be checked, unless the full library is checked, because one of its sources
13761 needs to be recompiled.
13763 For instance, assume the project file @code{A} imports the library project file
13764 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
13765 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
13766 @file{l2.ads}, @file{l2.adb}.
13768 If @file{l1.adb} has been modified, then the library associated with @code{L}
13769 will be rebuilt when compiling all the immediate sources of @code{A} only
13770 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
13773 To be sure that all the sources in the library associated with @code{L} are
13774 up to date, and that all the sources of project @code{A} are also up to date,
13775 the following two commands needs to be used:
13782 When a library is built or rebuilt, an attempt is made first to delete all
13783 files in the library directory.
13784 All @file{ALI} files will also be copied from the object directory to the
13785 library directory. To build executables, @command{gnatmake} will use the
13786 library rather than the individual object files.
13789 It is also possible to create library project files for third-party libraries
13790 that are precompiled and cannot be compiled locally thanks to the
13791 @code{externally_built} attribute. (See @ref{Installing a library}).
13794 @c *******************************
13795 @c * Stand-alone Library Projects *
13796 @c *******************************
13798 @node Stand-alone Library Projects
13799 @section Stand-alone Library Projects
13802 A Stand-alone Library is a library that contains the necessary code to
13803 elaborate the Ada units that are included in the library. A Stand-alone
13804 Library is suitable to be used in an executable when the main is not
13805 in Ada. However, Stand-alone Libraries may also be used with an Ada main
13808 A Stand-alone Library Project is a Library Project where the library is
13809 a Stand-alone Library.
13811 To be a Stand-alone Library Project, in addition to the two attributes
13812 that make a project a Library Project (@code{Library_Name} and
13813 @code{Library_Dir}, see @ref{Library Projects}), the attribute
13814 @code{Library_Interface} must be defined.
13816 @smallexample @c projectfile
13818 for Library_Dir use "lib_dir";
13819 for Library_Name use "dummy";
13820 for Library_Interface use ("int1", "int1.child");
13824 Attribute @code{Library_Interface} has a nonempty string list value,
13825 each string in the list designating a unit contained in an immediate source
13826 of the project file.
13828 When a Stand-alone Library is built, first the binder is invoked to build
13829 a package whose name depends on the library name
13830 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
13831 This binder-generated package includes initialization and
13832 finalization procedures whose
13833 names depend on the library name (dummyinit and dummyfinal in the example
13834 above). The object corresponding to this package is included in the library.
13836 A dynamic or relocatable Stand-alone Library is automatically initialized
13837 if automatic initialization of Stand-alone Libraries is supported on the
13838 platform and if attribute @code{Library_Auto_Init} is not specified or
13839 is specified with the value "true". A static Stand-alone Library is never
13840 automatically initialized.
13842 Single string attribute @code{Library_Auto_Init} may be specified with only
13843 two possible values: "false" or "true" (case-insensitive). Specifying
13844 "false" for attribute @code{Library_Auto_Init} will prevent automatic
13845 initialization of dynamic or relocatable libraries.
13847 When a non-automatically initialized Stand-alone Library is used
13848 in an executable, its initialization procedure must be called before
13849 any service of the library is used.
13850 When the main subprogram is in Ada, it may mean that the initialization
13851 procedure has to be called during elaboration of another package.
13853 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
13854 (those that are listed in attribute @code{Library_Interface}) are copied to
13855 the Library Directory. As a consequence, only the Interface Units may be
13856 imported from Ada units outside of the library. If other units are imported,
13857 the binding phase will fail.
13859 When a Stand-Alone Library is bound, the switches that are specified in
13860 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
13861 used in the call to @command{gnatbind}.
13863 The string list attribute @code{Library_Options} may be used to specified
13864 additional switches to the call to @command{gcc} to link the library.
13866 The attribute @code{Library_Src_Dir}, may be specified for a
13867 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
13868 single string value. Its value must be the path (absolute or relative to the
13869 project directory) of an existing directory. This directory cannot be the
13870 object directory or one of the source directories, but it can be the same as
13871 the library directory. The sources of the Interface
13872 Units of the library, necessary to an Ada client of the library, will be
13873 copied to the designated directory, called Interface Copy directory.
13874 These sources includes the specs of the Interface Units, but they may also
13875 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
13876 are used, or when there is a generic units in the spec. Before the sources
13877 are copied to the Interface Copy directory, an attempt is made to delete all
13878 files in the Interface Copy directory.
13880 @c *************************************
13881 @c * Switches Related to Project Files *
13882 @c *************************************
13883 @node Switches Related to Project Files
13884 @section Switches Related to Project Files
13887 The following switches are used by GNAT tools that support project files:
13891 @item ^-P^/PROJECT_FILE=^@var{project}
13892 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
13893 Indicates the name of a project file. This project file will be parsed with
13894 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
13895 if any, and using the external references indicated
13896 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
13898 There may zero, one or more spaces between @option{-P} and @var{project}.
13902 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
13905 Since the Project Manager parses the project file only after all the switches
13906 on the command line are checked, the order of the switches
13907 @option{^-P^/PROJECT_FILE^},
13908 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
13909 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
13911 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
13912 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
13913 Indicates that external variable @var{name} has the value @var{value}.
13914 The Project Manager will use this value for occurrences of
13915 @code{external(name)} when parsing the project file.
13919 If @var{name} or @var{value} includes a space, then @var{name=value} should be
13920 put between quotes.
13928 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
13929 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
13930 @var{name}, only the last one is used.
13933 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
13934 takes precedence over the value of the same name in the environment.
13936 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
13937 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
13938 Indicates the verbosity of the parsing of GNAT project files.
13941 @option{-vP0} means Default;
13942 @option{-vP1} means Medium;
13943 @option{-vP2} means High.
13947 There are three possible options for this qualifier: DEFAULT, MEDIUM and
13952 The default is ^Default^DEFAULT^: no output for syntactically correct
13955 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
13956 only the last one is used.
13958 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
13959 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
13960 Add directory <dir> at the beginning of the project search path, in order,
13961 after the current working directory.
13965 @cindex @option{-eL} (any project-aware tool)
13966 Follow all symbolic links when processing project files.
13969 @item ^--subdirs^/SUBDIRS^=<subdir>
13970 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
13971 This switch is recognized by gnatmake and gnatclean. It indicate that the real
13972 directories (except the source directories) are the subdirectories <subdir>
13973 of the directories specified in the project files. This applies in particular
13974 to object directories, library directories and exec directories. If the
13975 subdirectories do not exist, they are created automatically.
13979 @c **********************************
13980 @c * Tools Supporting Project Files *
13981 @c **********************************
13983 @node Tools Supporting Project Files
13984 @section Tools Supporting Project Files
13987 * gnatmake and Project Files::
13988 * The GNAT Driver and Project Files::
13991 @node gnatmake and Project Files
13992 @subsection gnatmake and Project Files
13995 This section covers several topics related to @command{gnatmake} and
13996 project files: defining ^switches^switches^ for @command{gnatmake}
13997 and for the tools that it invokes; specifying configuration pragmas;
13998 the use of the @code{Main} attribute; building and rebuilding library project
14002 * ^Switches^Switches^ and Project Files::
14003 * Specifying Configuration Pragmas::
14004 * Project Files and Main Subprograms::
14005 * Library Project Files::
14008 @node ^Switches^Switches^ and Project Files
14009 @subsubsection ^Switches^Switches^ and Project Files
14012 It is not currently possible to specify VMS style qualifiers in the project
14013 files; only Unix style ^switches^switches^ may be specified.
14017 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14018 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14019 attribute, a @code{^Switches^Switches^} attribute, or both;
14020 as their names imply, these ^switch^switch^-related
14021 attributes affect the ^switches^switches^ that are used for each of these GNAT
14023 @command{gnatmake} is invoked. As will be explained below, these
14024 component-specific ^switches^switches^ precede
14025 the ^switches^switches^ provided on the @command{gnatmake} command line.
14027 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14028 array indexed by language name (case insensitive) whose value is a string list.
14031 @smallexample @c projectfile
14033 package Compiler is
14034 for ^Default_Switches^Default_Switches^ ("Ada")
14035 use ("^-gnaty^-gnaty^",
14042 The @code{^Switches^Switches^} attribute is also an associative array,
14043 indexed by a file name (which may or may not be case sensitive, depending
14044 on the operating system) whose value is a string list. For example:
14046 @smallexample @c projectfile
14049 for ^Switches^Switches^ ("main1.adb")
14051 for ^Switches^Switches^ ("main2.adb")
14058 For the @code{Builder} package, the file names must designate source files
14059 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14060 file names must designate @file{ALI} or source files for main subprograms.
14061 In each case just the file name without an explicit extension is acceptable.
14063 For each tool used in a program build (@command{gnatmake}, the compiler, the
14064 binder, and the linker), the corresponding package @dfn{contributes} a set of
14065 ^switches^switches^ for each file on which the tool is invoked, based on the
14066 ^switch^switch^-related attributes defined in the package.
14067 In particular, the ^switches^switches^
14068 that each of these packages contributes for a given file @var{f} comprise:
14072 the value of attribute @code{^Switches^Switches^ (@var{f})},
14073 if it is specified in the package for the given file,
14075 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14076 if it is specified in the package.
14080 If neither of these attributes is defined in the package, then the package does
14081 not contribute any ^switches^switches^ for the given file.
14083 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14084 two sets, in the following order: those contributed for the file
14085 by the @code{Builder} package;
14086 and the switches passed on the command line.
14088 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14089 the ^switches^switches^ passed to the tool comprise three sets,
14090 in the following order:
14094 the applicable ^switches^switches^ contributed for the file
14095 by the @code{Builder} package in the project file supplied on the command line;
14098 those contributed for the file by the package (in the relevant project file --
14099 see below) corresponding to the tool; and
14102 the applicable switches passed on the command line.
14106 The term @emph{applicable ^switches^switches^} reflects the fact that
14107 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14108 tools, depending on the individual ^switch^switch^.
14110 @command{gnatmake} may invoke the compiler on source files from different
14111 projects. The Project Manager will use the appropriate project file to
14112 determine the @code{Compiler} package for each source file being compiled.
14113 Likewise for the @code{Binder} and @code{Linker} packages.
14115 As an example, consider the following package in a project file:
14117 @smallexample @c projectfile
14120 package Compiler is
14121 for ^Default_Switches^Default_Switches^ ("Ada")
14123 for ^Switches^Switches^ ("a.adb")
14125 for ^Switches^Switches^ ("b.adb")
14127 "^-gnaty^-gnaty^");
14134 If @command{gnatmake} is invoked with this project file, and it needs to
14135 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14136 @file{a.adb} will be compiled with the ^switch^switch^
14137 @option{^-O1^-O1^},
14138 @file{b.adb} with ^switches^switches^
14140 and @option{^-gnaty^-gnaty^},
14141 and @file{c.adb} with @option{^-g^-g^}.
14143 The following example illustrates the ordering of the ^switches^switches^
14144 contributed by different packages:
14146 @smallexample @c projectfile
14150 for ^Switches^Switches^ ("main.adb")
14158 package Compiler is
14159 for ^Switches^Switches^ ("main.adb")
14167 If you issue the command:
14170 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14174 then the compiler will be invoked on @file{main.adb} with the following
14175 sequence of ^switches^switches^
14178 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14181 with the last @option{^-O^-O^}
14182 ^switch^switch^ having precedence over the earlier ones;
14183 several other ^switches^switches^
14184 (such as @option{^-c^-c^}) are added implicitly.
14186 The ^switches^switches^
14188 and @option{^-O1^-O1^} are contributed by package
14189 @code{Builder}, @option{^-O2^-O2^} is contributed
14190 by the package @code{Compiler}
14191 and @option{^-O0^-O0^} comes from the command line.
14193 The @option{^-g^-g^}
14194 ^switch^switch^ will also be passed in the invocation of
14195 @command{Gnatlink.}
14197 A final example illustrates switch contributions from packages in different
14200 @smallexample @c projectfile
14203 for Source_Files use ("pack.ads", "pack.adb");
14204 package Compiler is
14205 for ^Default_Switches^Default_Switches^ ("Ada")
14206 use ("^-gnata^-gnata^");
14214 for Source_Files use ("foo_main.adb", "bar_main.adb");
14216 for ^Switches^Switches^ ("foo_main.adb")
14224 -- Ada source file:
14226 procedure Foo_Main is
14234 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14238 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14239 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14240 @option{^-gnato^-gnato^} (passed on the command line).
14241 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14242 are @option{^-g^-g^} from @code{Proj4.Builder},
14243 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14244 and @option{^-gnato^-gnato^} from the command line.
14247 When using @command{gnatmake} with project files, some ^switches^switches^ or
14248 arguments may be expressed as relative paths. As the working directory where
14249 compilation occurs may change, these relative paths are converted to absolute
14250 paths. For the ^switches^switches^ found in a project file, the relative paths
14251 are relative to the project file directory, for the switches on the command
14252 line, they are relative to the directory where @command{gnatmake} is invoked.
14253 The ^switches^switches^ for which this occurs are:
14259 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14261 ^-o^-o^, object files specified in package @code{Linker} or after
14262 -largs on the command line). The exception to this rule is the ^switch^switch^
14263 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14265 @node Specifying Configuration Pragmas
14266 @subsubsection Specifying Configuration Pragmas
14268 When using @command{gnatmake} with project files, if there exists a file
14269 @file{gnat.adc} that contains configuration pragmas, this file will be
14272 Configuration pragmas can be defined by means of the following attributes in
14273 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14274 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14276 Both these attributes are single string attributes. Their values is the path
14277 name of a file containing configuration pragmas. If a path name is relative,
14278 then it is relative to the project directory of the project file where the
14279 attribute is defined.
14281 When compiling a source, the configuration pragmas used are, in order,
14282 those listed in the file designated by attribute
14283 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14284 project file, if it is specified, and those listed in the file designated by
14285 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14286 the project file of the source, if it exists.
14288 @node Project Files and Main Subprograms
14289 @subsubsection Project Files and Main Subprograms
14292 When using a project file, you can invoke @command{gnatmake}
14293 with one or several main subprograms, by specifying their source files on the
14297 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14301 Each of these needs to be a source file of the same project, except
14302 when the switch ^-u^/UNIQUE^ is used.
14305 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14306 same project, one of the project in the tree rooted at the project specified
14307 on the command line. The package @code{Builder} of this common project, the
14308 "main project" is the one that is considered by @command{gnatmake}.
14311 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14312 imported directly or indirectly by the project specified on the command line.
14313 Note that if such a source file is not part of the project specified on the
14314 command line, the ^switches^switches^ found in package @code{Builder} of the
14315 project specified on the command line, if any, that are transmitted
14316 to the compiler will still be used, not those found in the project file of
14320 When using a project file, you can also invoke @command{gnatmake} without
14321 explicitly specifying any main, and the effect depends on whether you have
14322 defined the @code{Main} attribute. This attribute has a string list value,
14323 where each element in the list is the name of a source file (the file
14324 extension is optional) that contains a unit that can be a main subprogram.
14326 If the @code{Main} attribute is defined in a project file as a non-empty
14327 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14328 line, then invoking @command{gnatmake} with this project file but without any
14329 main on the command line is equivalent to invoking @command{gnatmake} with all
14330 the file names in the @code{Main} attribute on the command line.
14333 @smallexample @c projectfile
14336 for Main use ("main1", "main2", "main3");
14342 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14344 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14346 When the project attribute @code{Main} is not specified, or is specified
14347 as an empty string list, or when the switch @option{-u} is used on the command
14348 line, then invoking @command{gnatmake} with no main on the command line will
14349 result in all immediate sources of the project file being checked, and
14350 potentially recompiled. Depending on the presence of the switch @option{-u},
14351 sources from other project files on which the immediate sources of the main
14352 project file depend are also checked and potentially recompiled. In other
14353 words, the @option{-u} switch is applied to all of the immediate sources of the
14356 When no main is specified on the command line and attribute @code{Main} exists
14357 and includes several mains, or when several mains are specified on the
14358 command line, the default ^switches^switches^ in package @code{Builder} will
14359 be used for all mains, even if there are specific ^switches^switches^
14360 specified for one or several mains.
14362 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14363 the specific ^switches^switches^ for each main, if they are specified.
14365 @node Library Project Files
14366 @subsubsection Library Project Files
14369 When @command{gnatmake} is invoked with a main project file that is a library
14370 project file, it is not allowed to specify one or more mains on the command
14374 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14375 ^-l^/ACTION=LINK^ have special meanings.
14378 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14379 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14382 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14383 to @command{gnatmake} that the binder generated file should be compiled
14384 (in the case of a stand-alone library) and that the library should be built.
14388 @node The GNAT Driver and Project Files
14389 @subsection The GNAT Driver and Project Files
14392 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14393 can benefit from project files:
14394 @command{^gnatbind^gnatbind^},
14395 @command{^gnatcheck^gnatcheck^}),
14396 @command{^gnatclean^gnatclean^}),
14397 @command{^gnatelim^gnatelim^},
14398 @command{^gnatfind^gnatfind^},
14399 @command{^gnatlink^gnatlink^},
14400 @command{^gnatls^gnatls^},
14401 @command{^gnatmetric^gnatmetric^},
14402 @command{^gnatpp^gnatpp^},
14403 @command{^gnatstub^gnatstub^},
14404 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14405 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14406 They must be invoked through the @command{gnat} driver.
14408 The @command{gnat} driver is a wrapper that accepts a number of commands and
14409 calls the corresponding tool. It was designed initially for VMS platforms (to
14410 convert VMS qualifiers to Unix-style switches), but it is now available on all
14413 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14414 (case insensitive):
14418 BIND to invoke @command{^gnatbind^gnatbind^}
14420 CHOP to invoke @command{^gnatchop^gnatchop^}
14422 CLEAN to invoke @command{^gnatclean^gnatclean^}
14424 COMP or COMPILE to invoke the compiler
14426 ELIM to invoke @command{^gnatelim^gnatelim^}
14428 FIND to invoke @command{^gnatfind^gnatfind^}
14430 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14432 LINK to invoke @command{^gnatlink^gnatlink^}
14434 LS or LIST to invoke @command{^gnatls^gnatls^}
14436 MAKE to invoke @command{^gnatmake^gnatmake^}
14438 NAME to invoke @command{^gnatname^gnatname^}
14440 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14442 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14444 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14446 STUB to invoke @command{^gnatstub^gnatstub^}
14448 XREF to invoke @command{^gnatxref^gnatxref^}
14452 (note that the compiler is invoked using the command
14453 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14456 On non-VMS platforms, between @command{gnat} and the command, two
14457 special switches may be used:
14461 @command{-v} to display the invocation of the tool.
14463 @command{-dn} to prevent the @command{gnat} driver from removing
14464 the temporary files it has created. These temporary files are
14465 configuration files and temporary file list files.
14469 The command may be followed by switches and arguments for the invoked
14473 gnat bind -C main.ali
14479 Switches may also be put in text files, one switch per line, and the text
14480 files may be specified with their path name preceded by '@@'.
14483 gnat bind @@args.txt main.ali
14487 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14488 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14489 (@option{^-P^/PROJECT_FILE^},
14490 @option{^-X^/EXTERNAL_REFERENCE^} and
14491 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14492 the switches of the invoking tool.
14495 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14496 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14497 the immediate sources of the specified project file.
14500 When GNAT METRIC is used with a project file, but with no source
14501 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14502 with all the immediate sources of the specified project file and with
14503 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14507 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14508 a project file, no source is specified on the command line and
14509 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14510 the underlying tool (^gnatpp^gnatpp^ or
14511 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14512 not only for the immediate sources of the main project.
14514 (-U stands for Universal or Union of the project files of the project tree)
14518 For each of the following commands, there is optionally a corresponding
14519 package in the main project.
14523 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14526 package @code{Check} for command CHECK (invoking
14527 @code{^gnatcheck^gnatcheck^})
14530 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14533 package @code{Cross_Reference} for command XREF (invoking
14534 @code{^gnatxref^gnatxref^})
14537 package @code{Eliminate} for command ELIM (invoking
14538 @code{^gnatelim^gnatelim^})
14541 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14544 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14547 package @code{Gnatstub} for command STUB
14548 (invoking @code{^gnatstub^gnatstub^})
14551 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14554 package @code{Metrics} for command METRIC
14555 (invoking @code{^gnatmetric^gnatmetric^})
14558 package @code{Pretty_Printer} for command PP or PRETTY
14559 (invoking @code{^gnatpp^gnatpp^})
14564 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14565 a simple variable with a string list value. It contains ^switches^switches^
14566 for the invocation of @code{^gnatls^gnatls^}.
14568 @smallexample @c projectfile
14572 for ^Switches^Switches^
14581 All other packages have two attribute @code{^Switches^Switches^} and
14582 @code{^Default_Switches^Default_Switches^}.
14585 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14586 source file name, that has a string list value: the ^switches^switches^ to be
14587 used when the tool corresponding to the package is invoked for the specific
14591 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14592 indexed by the programming language that has a string list value.
14593 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14594 ^switches^switches^ for the invocation of the tool corresponding
14595 to the package, except if a specific @code{^Switches^Switches^} attribute
14596 is specified for the source file.
14598 @smallexample @c projectfile
14602 for Source_Dirs use ("./**");
14605 for ^Switches^Switches^ use
14612 package Compiler is
14613 for ^Default_Switches^Default_Switches^ ("Ada")
14614 use ("^-gnatv^-gnatv^",
14615 "^-gnatwa^-gnatwa^");
14621 for ^Default_Switches^Default_Switches^ ("Ada")
14629 for ^Default_Switches^Default_Switches^ ("Ada")
14631 for ^Switches^Switches^ ("main.adb")
14640 for ^Default_Switches^Default_Switches^ ("Ada")
14647 package Cross_Reference is
14648 for ^Default_Switches^Default_Switches^ ("Ada")
14653 end Cross_Reference;
14659 With the above project file, commands such as
14662 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14663 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14664 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14665 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14666 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14670 will set up the environment properly and invoke the tool with the switches
14671 found in the package corresponding to the tool:
14672 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14673 except @code{^Switches^Switches^ ("main.adb")}
14674 for @code{^gnatlink^gnatlink^}.
14675 It is also possible to invoke some of the tools,
14676 @code{^gnatcheck^gnatcheck^}),
14677 @code{^gnatmetric^gnatmetric^}),
14678 and @code{^gnatpp^gnatpp^})
14679 on a set of project units thanks to the combination of the switches
14680 @option{-P}, @option{-U} and possibly the main unit when one is interested
14681 in its closure. For instance,
14685 will compute the metrics for all the immediate units of project
14688 gnat metric -Pproj -U
14690 will compute the metrics for all the units of the closure of projects
14691 rooted at @code{proj}.
14693 gnat metric -Pproj -U main_unit
14695 will compute the metrics for the closure of units rooted at
14696 @code{main_unit}. This last possibility relies implicitly
14697 on @command{gnatbind}'s option @option{-R}.
14699 @c **********************
14700 @node An Extended Example
14701 @section An Extended Example
14704 Suppose that we have two programs, @var{prog1} and @var{prog2},
14705 whose sources are in corresponding directories. We would like
14706 to build them with a single @command{gnatmake} command, and we want to place
14707 their object files into @file{build} subdirectories of the source directories.
14708 Furthermore, we want to have to have two separate subdirectories
14709 in @file{build} -- @file{release} and @file{debug} -- which will contain
14710 the object files compiled with different set of compilation flags.
14712 In other words, we have the following structure:
14729 Here are the project files that we must place in a directory @file{main}
14730 to maintain this structure:
14734 @item We create a @code{Common} project with a package @code{Compiler} that
14735 specifies the compilation ^switches^switches^:
14740 @b{project} Common @b{is}
14742 @b{for} Source_Dirs @b{use} (); -- No source files
14746 @b{type} Build_Type @b{is} ("release", "debug");
14747 Build : Build_Type := External ("BUILD", "debug");
14750 @b{package} Compiler @b{is}
14751 @b{case} Build @b{is}
14752 @b{when} "release" =>
14753 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14754 @b{use} ("^-O2^-O2^");
14755 @b{when} "debug" =>
14756 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14757 @b{use} ("^-g^-g^");
14765 @item We create separate projects for the two programs:
14772 @b{project} Prog1 @b{is}
14774 @b{for} Source_Dirs @b{use} ("prog1");
14775 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
14777 @b{package} Compiler @b{renames} Common.Compiler;
14788 @b{project} Prog2 @b{is}
14790 @b{for} Source_Dirs @b{use} ("prog2");
14791 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
14793 @b{package} Compiler @b{renames} Common.Compiler;
14799 @item We create a wrapping project @code{Main}:
14808 @b{project} Main @b{is}
14810 @b{package} Compiler @b{renames} Common.Compiler;
14816 @item Finally we need to create a dummy procedure that @code{with}s (either
14817 explicitly or implicitly) all the sources of our two programs.
14822 Now we can build the programs using the command
14825 gnatmake ^-P^/PROJECT_FILE=^main dummy
14829 for the Debug mode, or
14833 gnatmake -Pmain -XBUILD=release
14839 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
14844 for the Release mode.
14846 @c ********************************
14847 @c * Project File Complete Syntax *
14848 @c ********************************
14850 @node Project File Complete Syntax
14851 @section Project File Complete Syntax
14855 context_clause project_declaration
14861 @b{with} path_name @{ , path_name @} ;
14866 project_declaration ::=
14867 simple_project_declaration | project_extension
14869 simple_project_declaration ::=
14870 @b{project} <project_>simple_name @b{is}
14871 @{declarative_item@}
14872 @b{end} <project_>simple_name;
14874 project_extension ::=
14875 @b{project} <project_>simple_name @b{extends} path_name @b{is}
14876 @{declarative_item@}
14877 @b{end} <project_>simple_name;
14879 declarative_item ::=
14880 package_declaration |
14881 typed_string_declaration |
14882 other_declarative_item
14884 package_declaration ::=
14885 package_spec | package_renaming
14888 @b{package} package_identifier @b{is}
14889 @{simple_declarative_item@}
14890 @b{end} package_identifier ;
14892 package_identifier ::=
14893 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
14894 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
14895 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
14897 package_renaming ::==
14898 @b{package} package_identifier @b{renames}
14899 <project_>simple_name.package_identifier ;
14901 typed_string_declaration ::=
14902 @b{type} <typed_string_>_simple_name @b{is}
14903 ( string_literal @{, string_literal@} );
14905 other_declarative_item ::=
14906 attribute_declaration |
14907 typed_variable_declaration |
14908 variable_declaration |
14911 attribute_declaration ::=
14912 full_associative_array_declaration |
14913 @b{for} attribute_designator @b{use} expression ;
14915 full_associative_array_declaration ::=
14916 @b{for} <associative_array_attribute_>simple_name @b{use}
14917 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
14919 attribute_designator ::=
14920 <simple_attribute_>simple_name |
14921 <associative_array_attribute_>simple_name ( string_literal )
14923 typed_variable_declaration ::=
14924 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
14926 variable_declaration ::=
14927 <variable_>simple_name := expression;
14937 attribute_reference
14943 ( <string_>expression @{ , <string_>expression @} )
14946 @b{external} ( string_literal [, string_literal] )
14948 attribute_reference ::=
14949 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
14951 attribute_prefix ::=
14953 <project_>simple_name | package_identifier |
14954 <project_>simple_name . package_identifier
14956 case_construction ::=
14957 @b{case} <typed_variable_>name @b{is}
14962 @b{when} discrete_choice_list =>
14963 @{case_construction | attribute_declaration@}
14965 discrete_choice_list ::=
14966 string_literal @{| string_literal@} |
14970 simple_name @{. simple_name@}
14973 identifier (same as Ada)
14977 @node The Cross-Referencing Tools gnatxref and gnatfind
14978 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
14983 The compiler generates cross-referencing information (unless
14984 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
14985 This information indicates where in the source each entity is declared and
14986 referenced. Note that entities in package Standard are not included, but
14987 entities in all other predefined units are included in the output.
14989 Before using any of these two tools, you need to compile successfully your
14990 application, so that GNAT gets a chance to generate the cross-referencing
14993 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
14994 information to provide the user with the capability to easily locate the
14995 declaration and references to an entity. These tools are quite similar,
14996 the difference being that @code{gnatfind} is intended for locating
14997 definitions and/or references to a specified entity or entities, whereas
14998 @code{gnatxref} is oriented to generating a full report of all
15001 To use these tools, you must not compile your application using the
15002 @option{-gnatx} switch on the @command{gnatmake} command line
15003 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15004 information will not be generated.
15006 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15007 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15010 * gnatxref Switches::
15011 * gnatfind Switches::
15012 * Project Files for gnatxref and gnatfind::
15013 * Regular Expressions in gnatfind and gnatxref::
15014 * Examples of gnatxref Usage::
15015 * Examples of gnatfind Usage::
15018 @node gnatxref Switches
15019 @section @code{gnatxref} Switches
15022 The command invocation for @code{gnatxref} is:
15024 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15033 identifies the source files for which a report is to be generated. The
15034 ``with''ed units will be processed too. You must provide at least one file.
15036 These file names are considered to be regular expressions, so for instance
15037 specifying @file{source*.adb} is the same as giving every file in the current
15038 directory whose name starts with @file{source} and whose extension is
15041 You shouldn't specify any directory name, just base names. @command{gnatxref}
15042 and @command{gnatfind} will be able to locate these files by themselves using
15043 the source path. If you specify directories, no result is produced.
15048 The switches can be:
15052 @cindex @option{--version} @command{gnatxref}
15053 Display Copyright and version, then exit disregarding all other options.
15056 @cindex @option{--help} @command{gnatxref}
15057 If @option{--version} was not used, display usage, then exit disregarding
15060 @item ^-a^/ALL_FILES^
15061 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15062 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15063 the read-only files found in the library search path. Otherwise, these files
15064 will be ignored. This option can be used to protect Gnat sources or your own
15065 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15066 much faster, and their output much smaller. Read-only here refers to access
15067 or permissions status in the file system for the current user.
15070 @cindex @option{-aIDIR} (@command{gnatxref})
15071 When looking for source files also look in directory DIR. The order in which
15072 source file search is undertaken is the same as for @command{gnatmake}.
15075 @cindex @option{-aODIR} (@command{gnatxref})
15076 When searching for library and object files, look in directory
15077 DIR. The order in which library files are searched is the same as for
15078 @command{gnatmake}.
15081 @cindex @option{-nostdinc} (@command{gnatxref})
15082 Do not look for sources in the system default directory.
15085 @cindex @option{-nostdlib} (@command{gnatxref})
15086 Do not look for library files in the system default directory.
15088 @item --RTS=@var{rts-path}
15089 @cindex @option{--RTS} (@command{gnatxref})
15090 Specifies the default location of the runtime library. Same meaning as the
15091 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15093 @item ^-d^/DERIVED_TYPES^
15094 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15095 If this switch is set @code{gnatxref} will output the parent type
15096 reference for each matching derived types.
15098 @item ^-f^/FULL_PATHNAME^
15099 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15100 If this switch is set, the output file names will be preceded by their
15101 directory (if the file was found in the search path). If this switch is
15102 not set, the directory will not be printed.
15104 @item ^-g^/IGNORE_LOCALS^
15105 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15106 If this switch is set, information is output only for library-level
15107 entities, ignoring local entities. The use of this switch may accelerate
15108 @code{gnatfind} and @code{gnatxref}.
15111 @cindex @option{-IDIR} (@command{gnatxref})
15112 Equivalent to @samp{-aODIR -aIDIR}.
15115 @cindex @option{-pFILE} (@command{gnatxref})
15116 Specify a project file to use @xref{Project Files}.
15117 If you need to use the @file{.gpr}
15118 project files, you should use gnatxref through the GNAT driver
15119 (@command{gnat xref -Pproject}).
15121 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15122 project file in the current directory.
15124 If a project file is either specified or found by the tools, then the content
15125 of the source directory and object directory lines are added as if they
15126 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15127 and @samp{^-aO^OBJECT_SEARCH^}.
15129 Output only unused symbols. This may be really useful if you give your
15130 main compilation unit on the command line, as @code{gnatxref} will then
15131 display every unused entity and 'with'ed package.
15135 Instead of producing the default output, @code{gnatxref} will generate a
15136 @file{tags} file that can be used by vi. For examples how to use this
15137 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15138 to the standard output, thus you will have to redirect it to a file.
15144 All these switches may be in any order on the command line, and may even
15145 appear after the file names. They need not be separated by spaces, thus
15146 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15147 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15149 @node gnatfind Switches
15150 @section @code{gnatfind} Switches
15153 The command line for @code{gnatfind} is:
15156 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15157 @r{[}@var{file1} @var{file2} @dots{}]
15165 An entity will be output only if it matches the regular expression found
15166 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15168 Omitting the pattern is equivalent to specifying @samp{*}, which
15169 will match any entity. Note that if you do not provide a pattern, you
15170 have to provide both a sourcefile and a line.
15172 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15173 for matching purposes. At the current time there is no support for
15174 8-bit codes other than Latin-1, or for wide characters in identifiers.
15177 @code{gnatfind} will look for references, bodies or declarations
15178 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15179 and column @var{column}. See @ref{Examples of gnatfind Usage}
15180 for syntax examples.
15183 is a decimal integer identifying the line number containing
15184 the reference to the entity (or entities) to be located.
15187 is a decimal integer identifying the exact location on the
15188 line of the first character of the identifier for the
15189 entity reference. Columns are numbered from 1.
15191 @item file1 file2 @dots{}
15192 The search will be restricted to these source files. If none are given, then
15193 the search will be done for every library file in the search path.
15194 These file must appear only after the pattern or sourcefile.
15196 These file names are considered to be regular expressions, so for instance
15197 specifying @file{source*.adb} is the same as giving every file in the current
15198 directory whose name starts with @file{source} and whose extension is
15201 The location of the spec of the entity will always be displayed, even if it
15202 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15203 occurrences of the entity in the separate units of the ones given on the
15204 command line will also be displayed.
15206 Note that if you specify at least one file in this part, @code{gnatfind} may
15207 sometimes not be able to find the body of the subprograms.
15212 At least one of 'sourcefile' or 'pattern' has to be present on
15215 The following switches are available:
15219 @cindex @option{--version} @command{gnatfind}
15220 Display Copyright and version, then exit disregarding all other options.
15223 @cindex @option{--help} @command{gnatfind}
15224 If @option{--version} was not used, display usage, then exit disregarding
15227 @item ^-a^/ALL_FILES^
15228 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15229 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15230 the read-only files found in the library search path. Otherwise, these files
15231 will be ignored. This option can be used to protect Gnat sources or your own
15232 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15233 much faster, and their output much smaller. Read-only here refers to access
15234 or permission status in the file system for the current user.
15237 @cindex @option{-aIDIR} (@command{gnatfind})
15238 When looking for source files also look in directory DIR. The order in which
15239 source file search is undertaken is the same as for @command{gnatmake}.
15242 @cindex @option{-aODIR} (@command{gnatfind})
15243 When searching for library and object files, look in directory
15244 DIR. The order in which library files are searched is the same as for
15245 @command{gnatmake}.
15248 @cindex @option{-nostdinc} (@command{gnatfind})
15249 Do not look for sources in the system default directory.
15252 @cindex @option{-nostdlib} (@command{gnatfind})
15253 Do not look for library files in the system default directory.
15255 @item --RTS=@var{rts-path}
15256 @cindex @option{--RTS} (@command{gnatfind})
15257 Specifies the default location of the runtime library. Same meaning as the
15258 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15260 @item ^-d^/DERIVED_TYPE_INFORMATION^
15261 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15262 If this switch is set, then @code{gnatfind} will output the parent type
15263 reference for each matching derived types.
15265 @item ^-e^/EXPRESSIONS^
15266 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15267 By default, @code{gnatfind} accept the simple regular expression set for
15268 @samp{pattern}. If this switch is set, then the pattern will be
15269 considered as full Unix-style regular expression.
15271 @item ^-f^/FULL_PATHNAME^
15272 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15273 If this switch is set, the output file names will be preceded by their
15274 directory (if the file was found in the search path). If this switch is
15275 not set, the directory will not be printed.
15277 @item ^-g^/IGNORE_LOCALS^
15278 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15279 If this switch is set, information is output only for library-level
15280 entities, ignoring local entities. The use of this switch may accelerate
15281 @code{gnatfind} and @code{gnatxref}.
15284 @cindex @option{-IDIR} (@command{gnatfind})
15285 Equivalent to @samp{-aODIR -aIDIR}.
15288 @cindex @option{-pFILE} (@command{gnatfind})
15289 Specify a project file (@pxref{Project Files}) to use.
15290 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15291 project file in the current directory.
15293 If a project file is either specified or found by the tools, then the content
15294 of the source directory and object directory lines are added as if they
15295 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15296 @samp{^-aO^/OBJECT_SEARCH^}.
15298 @item ^-r^/REFERENCES^
15299 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15300 By default, @code{gnatfind} will output only the information about the
15301 declaration, body or type completion of the entities. If this switch is
15302 set, the @code{gnatfind} will locate every reference to the entities in
15303 the files specified on the command line (or in every file in the search
15304 path if no file is given on the command line).
15306 @item ^-s^/PRINT_LINES^
15307 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15308 If this switch is set, then @code{gnatfind} will output the content
15309 of the Ada source file lines were the entity was found.
15311 @item ^-t^/TYPE_HIERARCHY^
15312 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15313 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15314 the specified type. It act like -d option but recursively from parent
15315 type to parent type. When this switch is set it is not possible to
15316 specify more than one file.
15321 All these switches may be in any order on the command line, and may even
15322 appear after the file names. They need not be separated by spaces, thus
15323 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15324 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15326 As stated previously, gnatfind will search in every directory in the
15327 search path. You can force it to look only in the current directory if
15328 you specify @code{*} at the end of the command line.
15330 @node Project Files for gnatxref and gnatfind
15331 @section Project Files for @command{gnatxref} and @command{gnatfind}
15334 Project files allow a programmer to specify how to compile its
15335 application, where to find sources, etc. These files are used
15337 primarily by GPS, but they can also be used
15340 @code{gnatxref} and @code{gnatfind}.
15342 A project file name must end with @file{.gpr}. If a single one is
15343 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15344 extract the information from it. If multiple project files are found, none of
15345 them is read, and you have to use the @samp{-p} switch to specify the one
15348 The following lines can be included, even though most of them have default
15349 values which can be used in most cases.
15350 The lines can be entered in any order in the file.
15351 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15352 each line. If you have multiple instances, only the last one is taken into
15357 [default: @code{"^./^[]^"}]
15358 specifies a directory where to look for source files. Multiple @code{src_dir}
15359 lines can be specified and they will be searched in the order they
15363 [default: @code{"^./^[]^"}]
15364 specifies a directory where to look for object and library files. Multiple
15365 @code{obj_dir} lines can be specified, and they will be searched in the order
15368 @item comp_opt=SWITCHES
15369 [default: @code{""}]
15370 creates a variable which can be referred to subsequently by using
15371 the @code{$@{comp_opt@}} notation. This is intended to store the default
15372 switches given to @command{gnatmake} and @command{gcc}.
15374 @item bind_opt=SWITCHES
15375 [default: @code{""}]
15376 creates a variable which can be referred to subsequently by using
15377 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15378 switches given to @command{gnatbind}.
15380 @item link_opt=SWITCHES
15381 [default: @code{""}]
15382 creates a variable which can be referred to subsequently by using
15383 the @samp{$@{link_opt@}} notation. This is intended to store the default
15384 switches given to @command{gnatlink}.
15386 @item main=EXECUTABLE
15387 [default: @code{""}]
15388 specifies the name of the executable for the application. This variable can
15389 be referred to in the following lines by using the @samp{$@{main@}} notation.
15392 @item comp_cmd=COMMAND
15393 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15396 @item comp_cmd=COMMAND
15397 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15399 specifies the command used to compile a single file in the application.
15402 @item make_cmd=COMMAND
15403 [default: @code{"GNAT MAKE $@{main@}
15404 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15405 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15406 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15409 @item make_cmd=COMMAND
15410 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15411 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15412 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15414 specifies the command used to recompile the whole application.
15416 @item run_cmd=COMMAND
15417 [default: @code{"$@{main@}"}]
15418 specifies the command used to run the application.
15420 @item debug_cmd=COMMAND
15421 [default: @code{"gdb $@{main@}"}]
15422 specifies the command used to debug the application
15427 @command{gnatxref} and @command{gnatfind} only take into account the
15428 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15430 @node Regular Expressions in gnatfind and gnatxref
15431 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15434 As specified in the section about @command{gnatfind}, the pattern can be a
15435 regular expression. Actually, there are to set of regular expressions
15436 which are recognized by the program:
15439 @item globbing patterns
15440 These are the most usual regular expression. They are the same that you
15441 generally used in a Unix shell command line, or in a DOS session.
15443 Here is a more formal grammar:
15450 term ::= elmt -- matches elmt
15451 term ::= elmt elmt -- concatenation (elmt then elmt)
15452 term ::= * -- any string of 0 or more characters
15453 term ::= ? -- matches any character
15454 term ::= [char @{char@}] -- matches any character listed
15455 term ::= [char - char] -- matches any character in range
15459 @item full regular expression
15460 The second set of regular expressions is much more powerful. This is the
15461 type of regular expressions recognized by utilities such a @file{grep}.
15463 The following is the form of a regular expression, expressed in Ada
15464 reference manual style BNF is as follows
15471 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15473 term ::= item @{item@} -- concatenation (item then item)
15475 item ::= elmt -- match elmt
15476 item ::= elmt * -- zero or more elmt's
15477 item ::= elmt + -- one or more elmt's
15478 item ::= elmt ? -- matches elmt or nothing
15481 elmt ::= nschar -- matches given character
15482 elmt ::= [nschar @{nschar@}] -- matches any character listed
15483 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15484 elmt ::= [char - char] -- matches chars in given range
15485 elmt ::= \ char -- matches given character
15486 elmt ::= . -- matches any single character
15487 elmt ::= ( regexp ) -- parens used for grouping
15489 char ::= any character, including special characters
15490 nschar ::= any character except ()[].*+?^^^
15494 Following are a few examples:
15498 will match any of the two strings @samp{abcde} and @samp{fghi},
15501 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15502 @samp{abcccd}, and so on,
15505 will match any string which has only lowercase characters in it (and at
15506 least one character.
15511 @node Examples of gnatxref Usage
15512 @section Examples of @code{gnatxref} Usage
15514 @subsection General Usage
15517 For the following examples, we will consider the following units:
15519 @smallexample @c ada
15525 3: procedure Foo (B : in Integer);
15532 1: package body Main is
15533 2: procedure Foo (B : in Integer) is
15544 2: procedure Print (B : Integer);
15553 The first thing to do is to recompile your application (for instance, in
15554 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15555 the cross-referencing information.
15556 You can then issue any of the following commands:
15558 @item gnatxref main.adb
15559 @code{gnatxref} generates cross-reference information for main.adb
15560 and every unit 'with'ed by main.adb.
15562 The output would be:
15570 Decl: main.ads 3:20
15571 Body: main.adb 2:20
15572 Ref: main.adb 4:13 5:13 6:19
15575 Ref: main.adb 6:8 7:8
15585 Decl: main.ads 3:15
15586 Body: main.adb 2:15
15589 Body: main.adb 1:14
15592 Ref: main.adb 6:12 7:12
15596 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15597 its body is in main.adb, line 1, column 14 and is not referenced any where.
15599 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15600 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15602 @item gnatxref package1.adb package2.ads
15603 @code{gnatxref} will generates cross-reference information for
15604 package1.adb, package2.ads and any other package 'with'ed by any
15610 @subsection Using gnatxref with vi
15612 @code{gnatxref} can generate a tags file output, which can be used
15613 directly from @command{vi}. Note that the standard version of @command{vi}
15614 will not work properly with overloaded symbols. Consider using another
15615 free implementation of @command{vi}, such as @command{vim}.
15618 $ gnatxref -v gnatfind.adb > tags
15622 will generate the tags file for @code{gnatfind} itself (if the sources
15623 are in the search path!).
15625 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15626 (replacing @var{entity} by whatever you are looking for), and vi will
15627 display a new file with the corresponding declaration of entity.
15630 @node Examples of gnatfind Usage
15631 @section Examples of @code{gnatfind} Usage
15635 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15636 Find declarations for all entities xyz referenced at least once in
15637 main.adb. The references are search in every library file in the search
15640 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15643 The output will look like:
15645 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15646 ^directory/^[directory]^main.adb:24:10: xyz <= body
15647 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15651 that is to say, one of the entities xyz found in main.adb is declared at
15652 line 12 of main.ads (and its body is in main.adb), and another one is
15653 declared at line 45 of foo.ads
15655 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15656 This is the same command as the previous one, instead @code{gnatfind} will
15657 display the content of the Ada source file lines.
15659 The output will look like:
15662 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15664 ^directory/^[directory]^main.adb:24:10: xyz <= body
15666 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15671 This can make it easier to find exactly the location your are looking
15674 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15675 Find references to all entities containing an x that are
15676 referenced on line 123 of main.ads.
15677 The references will be searched only in main.ads and foo.adb.
15679 @item gnatfind main.ads:123
15680 Find declarations and bodies for all entities that are referenced on
15681 line 123 of main.ads.
15683 This is the same as @code{gnatfind "*":main.adb:123}.
15685 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15686 Find the declaration for the entity referenced at column 45 in
15687 line 123 of file main.adb in directory mydir. Note that it
15688 is usual to omit the identifier name when the column is given,
15689 since the column position identifies a unique reference.
15691 The column has to be the beginning of the identifier, and should not
15692 point to any character in the middle of the identifier.
15696 @c *********************************
15697 @node The GNAT Pretty-Printer gnatpp
15698 @chapter The GNAT Pretty-Printer @command{gnatpp}
15700 @cindex Pretty-Printer
15703 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15704 for source reformatting / pretty-printing.
15705 It takes an Ada source file as input and generates a reformatted
15707 You can specify various style directives via switches; e.g.,
15708 identifier case conventions, rules of indentation, and comment layout.
15710 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
15711 tree for the input source and thus requires the input to be syntactically and
15712 semantically legal.
15713 If this condition is not met, @command{gnatpp} will terminate with an
15714 error message; no output file will be generated.
15716 If the source files presented to @command{gnatpp} contain
15717 preprocessing directives, then the output file will
15718 correspond to the generated source after all
15719 preprocessing is carried out. There is no way
15720 using @command{gnatpp} to obtain pretty printed files that
15721 include the preprocessing directives.
15723 If the compilation unit
15724 contained in the input source depends semantically upon units located
15725 outside the current directory, you have to provide the source search path
15726 when invoking @command{gnatpp}, if these units are contained in files with
15727 names that do not follow the GNAT file naming rules, you have to provide
15728 the configuration file describing the corresponding naming scheme;
15729 see the description of the @command{gnatpp}
15730 switches below. Another possibility is to use a project file and to
15731 call @command{gnatpp} through the @command{gnat} driver
15733 The @command{gnatpp} command has the form
15736 $ gnatpp @ovar{switches} @var{filename}
15743 @var{switches} is an optional sequence of switches defining such properties as
15744 the formatting rules, the source search path, and the destination for the
15748 @var{filename} is the name (including the extension) of the source file to
15749 reformat; ``wildcards'' or several file names on the same gnatpp command are
15750 allowed. The file name may contain path information; it does not have to
15751 follow the GNAT file naming rules
15755 * Switches for gnatpp::
15756 * Formatting Rules::
15759 @node Switches for gnatpp
15760 @section Switches for @command{gnatpp}
15763 The following subsections describe the various switches accepted by
15764 @command{gnatpp}, organized by category.
15767 You specify a switch by supplying a name and generally also a value.
15768 In many cases the values for a switch with a given name are incompatible with
15770 (for example the switch that controls the casing of a reserved word may have
15771 exactly one value: upper case, lower case, or
15772 mixed case) and thus exactly one such switch can be in effect for an
15773 invocation of @command{gnatpp}.
15774 If more than one is supplied, the last one is used.
15775 However, some values for the same switch are mutually compatible.
15776 You may supply several such switches to @command{gnatpp}, but then
15777 each must be specified in full, with both the name and the value.
15778 Abbreviated forms (the name appearing once, followed by each value) are
15780 For example, to set
15781 the alignment of the assignment delimiter both in declarations and in
15782 assignment statements, you must write @option{-A2A3}
15783 (or @option{-A2 -A3}), but not @option{-A23}.
15787 In many cases the set of options for a given qualifier are incompatible with
15788 each other (for example the qualifier that controls the casing of a reserved
15789 word may have exactly one option, which specifies either upper case, lower
15790 case, or mixed case), and thus exactly one such option can be in effect for
15791 an invocation of @command{gnatpp}.
15792 If more than one is supplied, the last one is used.
15793 However, some qualifiers have options that are mutually compatible,
15794 and then you may then supply several such options when invoking
15798 In most cases, it is obvious whether or not the
15799 ^values for a switch with a given name^options for a given qualifier^
15800 are compatible with each other.
15801 When the semantics might not be evident, the summaries below explicitly
15802 indicate the effect.
15805 * Alignment Control::
15807 * Construct Layout Control::
15808 * General Text Layout Control::
15809 * Other Formatting Options::
15810 * Setting the Source Search Path::
15811 * Output File Control::
15812 * Other gnatpp Switches::
15815 @node Alignment Control
15816 @subsection Alignment Control
15817 @cindex Alignment control in @command{gnatpp}
15820 Programs can be easier to read if certain constructs are vertically aligned.
15821 By default all alignments are set ON.
15822 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
15823 OFF, and then use one or more of the other
15824 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
15825 to activate alignment for specific constructs.
15828 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
15832 Set all alignments to ON
15835 @item ^-A0^/ALIGN=OFF^
15836 Set all alignments to OFF
15838 @item ^-A1^/ALIGN=COLONS^
15839 Align @code{:} in declarations
15841 @item ^-A2^/ALIGN=DECLARATIONS^
15842 Align @code{:=} in initializations in declarations
15844 @item ^-A3^/ALIGN=STATEMENTS^
15845 Align @code{:=} in assignment statements
15847 @item ^-A4^/ALIGN=ARROWS^
15848 Align @code{=>} in associations
15850 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
15851 Align @code{at} keywords in the component clauses in record
15852 representation clauses
15856 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
15859 @node Casing Control
15860 @subsection Casing Control
15861 @cindex Casing control in @command{gnatpp}
15864 @command{gnatpp} allows you to specify the casing for reserved words,
15865 pragma names, attribute designators and identifiers.
15866 For identifiers you may define a
15867 general rule for name casing but also override this rule
15868 via a set of dictionary files.
15870 Three types of casing are supported: lower case, upper case, and mixed case.
15871 Lower and upper case are self-explanatory (but since some letters in
15872 Latin1 and other GNAT-supported character sets
15873 exist only in lower-case form, an upper case conversion will have no
15875 ``Mixed case'' means that the first letter, and also each letter immediately
15876 following an underscore, are converted to their uppercase forms;
15877 all the other letters are converted to their lowercase forms.
15880 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
15881 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
15882 Attribute designators are lower case
15884 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
15885 Attribute designators are upper case
15887 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
15888 Attribute designators are mixed case (this is the default)
15890 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
15891 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
15892 Keywords (technically, these are known in Ada as @emph{reserved words}) are
15893 lower case (this is the default)
15895 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
15896 Keywords are upper case
15898 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
15899 @item ^-nD^/NAME_CASING=AS_DECLARED^
15900 Name casing for defining occurrences are as they appear in the source file
15901 (this is the default)
15903 @item ^-nU^/NAME_CASING=UPPER_CASE^
15904 Names are in upper case
15906 @item ^-nL^/NAME_CASING=LOWER_CASE^
15907 Names are in lower case
15909 @item ^-nM^/NAME_CASING=MIXED_CASE^
15910 Names are in mixed case
15912 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
15913 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
15914 Pragma names are lower case
15916 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
15917 Pragma names are upper case
15919 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
15920 Pragma names are mixed case (this is the default)
15922 @item ^-D@var{file}^/DICTIONARY=@var{file}^
15923 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
15924 Use @var{file} as a @emph{dictionary file} that defines
15925 the casing for a set of specified names,
15926 thereby overriding the effect on these names by
15927 any explicit or implicit
15928 ^-n^/NAME_CASING^ switch.
15929 To supply more than one dictionary file,
15930 use ^several @option{-D} switches^a list of files as options^.
15933 @option{gnatpp} implicitly uses a @emph{default dictionary file}
15934 to define the casing for the Ada predefined names and
15935 the names declared in the GNAT libraries.
15937 @item ^-D-^/SPECIFIC_CASING^
15938 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
15939 Do not use the default dictionary file;
15940 instead, use the casing
15941 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
15946 The structure of a dictionary file, and details on the conventions
15947 used in the default dictionary file, are defined in @ref{Name Casing}.
15949 The @option{^-D-^/SPECIFIC_CASING^} and
15950 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
15953 @node Construct Layout Control
15954 @subsection Construct Layout Control
15955 @cindex Layout control in @command{gnatpp}
15958 This group of @command{gnatpp} switches controls the layout of comments and
15959 complex syntactic constructs. See @ref{Formatting Comments} for details
15963 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
15964 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
15965 All the comments remain unchanged
15967 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
15968 GNAT-style comment line indentation (this is the default).
15970 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
15971 Reference-manual comment line indentation.
15973 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
15974 GNAT-style comment beginning
15976 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
15977 Reformat comment blocks
15979 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
15980 Keep unchanged special form comments
15982 Reformat comment blocks
15984 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
15985 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
15986 GNAT-style layout (this is the default)
15988 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
15991 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
15994 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
15996 All the VT characters are removed from the comment text. All the HT characters
15997 are expanded with the sequences of space characters to get to the next tab
16000 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16001 @item ^--no-separate-is^/NO_SEPARATE_IS^
16002 Do not place the keyword @code{is} on a separate line in a subprogram body in
16003 case if the spec occupies more then one line.
16005 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16006 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16007 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16008 keyword @code{then} in IF statements on a separate line.
16010 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16011 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16012 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16013 keyword @code{then} in IF statements on a separate line. This option is
16014 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16016 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16017 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16018 Start each USE clause in a context clause from a separate line.
16020 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16021 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16022 Use a separate line for a loop or block statement name, but do not use an extra
16023 indentation level for the statement itself.
16029 The @option{-c1} and @option{-c2} switches are incompatible.
16030 The @option{-c3} and @option{-c4} switches are compatible with each other and
16031 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16032 the other comment formatting switches.
16034 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16039 For the @option{/COMMENTS_LAYOUT} qualifier:
16042 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16044 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16045 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16049 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16050 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16053 @node General Text Layout Control
16054 @subsection General Text Layout Control
16057 These switches allow control over line length and indentation.
16060 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16061 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16062 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16064 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16065 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16066 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16068 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16069 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16070 Indentation level for continuation lines (relative to the line being
16071 continued), @var{nnn} from 1@dots{}9.
16073 value is one less then the (normal) indentation level, unless the
16074 indentation is set to 1 (in which case the default value for continuation
16075 line indentation is also 1)
16078 @node Other Formatting Options
16079 @subsection Other Formatting Options
16082 These switches control the inclusion of missing end/exit labels, and
16083 the indentation level in @b{case} statements.
16086 @item ^-e^/NO_MISSED_LABELS^
16087 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16088 Do not insert missing end/exit labels. An end label is the name of
16089 a construct that may optionally be repeated at the end of the
16090 construct's declaration;
16091 e.g., the names of packages, subprograms, and tasks.
16092 An exit label is the name of a loop that may appear as target
16093 of an exit statement within the loop.
16094 By default, @command{gnatpp} inserts these end/exit labels when
16095 they are absent from the original source. This option suppresses such
16096 insertion, so that the formatted source reflects the original.
16098 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16099 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16100 Insert a Form Feed character after a pragma Page.
16102 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16103 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16104 Do not use an additional indentation level for @b{case} alternatives
16105 and variants if there are @var{nnn} or more (the default
16107 If @var{nnn} is 0, an additional indentation level is
16108 used for @b{case} alternatives and variants regardless of their number.
16111 @node Setting the Source Search Path
16112 @subsection Setting the Source Search Path
16115 To define the search path for the input source file, @command{gnatpp}
16116 uses the same switches as the GNAT compiler, with the same effects.
16119 @item ^-I^/SEARCH=^@var{dir}
16120 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16121 The same as the corresponding gcc switch
16123 @item ^-I-^/NOCURRENT_DIRECTORY^
16124 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16125 The same as the corresponding gcc switch
16127 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16128 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16129 The same as the corresponding gcc switch
16131 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16132 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16133 The same as the corresponding gcc switch
16137 @node Output File Control
16138 @subsection Output File Control
16141 By default the output is sent to the file whose name is obtained by appending
16142 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16143 (if the file with this name already exists, it is unconditionally overwritten).
16144 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16145 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16147 The output may be redirected by the following switches:
16150 @item ^-pipe^/STANDARD_OUTPUT^
16151 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16152 Send the output to @code{Standard_Output}
16154 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16155 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16156 Write the output into @var{output_file}.
16157 If @var{output_file} already exists, @command{gnatpp} terminates without
16158 reading or processing the input file.
16160 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16161 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16162 Write the output into @var{output_file}, overwriting the existing file
16163 (if one is present).
16165 @item ^-r^/REPLACE^
16166 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16167 Replace the input source file with the reformatted output, and copy the
16168 original input source into the file whose name is obtained by appending the
16169 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16170 If a file with this name already exists, @command{gnatpp} terminates without
16171 reading or processing the input file.
16173 @item ^-rf^/OVERRIDING_REPLACE^
16174 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16175 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16176 already exists, it is overwritten.
16178 @item ^-rnb^/REPLACE_NO_BACKUP^
16179 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16180 Replace the input source file with the reformatted output without
16181 creating any backup copy of the input source.
16183 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16184 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16185 Specifies the format of the reformatted output file. The @var{xxx}
16186 ^string specified with the switch^option^ may be either
16188 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16189 @item ``@option{^crlf^CRLF^}''
16190 the same as @option{^crlf^CRLF^}
16191 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16192 @item ``@option{^lf^LF^}''
16193 the same as @option{^unix^UNIX^}
16196 @item ^-W^/RESULT_ENCODING=^@var{e}
16197 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16198 Specify the wide character encoding method used to write the code in the
16200 @var{e} is one of the following:
16208 Upper half encoding
16210 @item ^s^SHIFT_JIS^
16220 Brackets encoding (default value)
16226 Options @option{^-pipe^/STANDARD_OUTPUT^},
16227 @option{^-o^/OUTPUT^} and
16228 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16229 contains only one file to reformat.
16231 @option{^--eol^/END_OF_LINE^}
16233 @option{^-W^/RESULT_ENCODING^}
16234 cannot be used together
16235 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16237 @node Other gnatpp Switches
16238 @subsection Other @code{gnatpp} Switches
16241 The additional @command{gnatpp} switches are defined in this subsection.
16244 @item ^-files @var{filename}^/FILES=@var{output_file}^
16245 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16246 Take the argument source files from the specified file. This file should be an
16247 ordinary textual file containing file names separated by spaces or
16248 line breaks. You can use this switch more then once in the same call to
16249 @command{gnatpp}. You also can combine this switch with explicit list of
16252 @item ^-v^/VERBOSE^
16253 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16255 @command{gnatpp} generates version information and then
16256 a trace of the actions it takes to produce or obtain the ASIS tree.
16258 @item ^-w^/WARNINGS^
16259 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16261 @command{gnatpp} generates a warning whenever it cannot provide
16262 a required layout in the result source.
16265 @node Formatting Rules
16266 @section Formatting Rules
16269 The following subsections show how @command{gnatpp} treats ``white space'',
16270 comments, program layout, and name casing.
16271 They provide the detailed descriptions of the switches shown above.
16274 * White Space and Empty Lines::
16275 * Formatting Comments::
16276 * Construct Layout::
16280 @node White Space and Empty Lines
16281 @subsection White Space and Empty Lines
16284 @command{gnatpp} does not have an option to control space characters.
16285 It will add or remove spaces according to the style illustrated by the
16286 examples in the @cite{Ada Reference Manual}.
16288 The only format effectors
16289 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16290 that will appear in the output file are platform-specific line breaks,
16291 and also format effectors within (but not at the end of) comments.
16292 In particular, each horizontal tab character that is not inside
16293 a comment will be treated as a space and thus will appear in the
16294 output file as zero or more spaces depending on
16295 the reformatting of the line in which it appears.
16296 The only exception is a Form Feed character, which is inserted after a
16297 pragma @code{Page} when @option{-ff} is set.
16299 The output file will contain no lines with trailing ``white space'' (spaces,
16302 Empty lines in the original source are preserved
16303 only if they separate declarations or statements.
16304 In such contexts, a
16305 sequence of two or more empty lines is replaced by exactly one empty line.
16306 Note that a blank line will be removed if it separates two ``comment blocks''
16307 (a comment block is a sequence of whole-line comments).
16308 In order to preserve a visual separation between comment blocks, use an
16309 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16310 Likewise, if for some reason you wish to have a sequence of empty lines,
16311 use a sequence of empty comments instead.
16313 @node Formatting Comments
16314 @subsection Formatting Comments
16317 Comments in Ada code are of two kinds:
16320 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16321 ``white space'') on a line
16324 an @emph{end-of-line comment}, which follows some other Ada lexical element
16329 The indentation of a whole-line comment is that of either
16330 the preceding or following line in
16331 the formatted source, depending on switch settings as will be described below.
16333 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16334 between the end of the preceding Ada lexical element and the beginning
16335 of the comment as appear in the original source,
16336 unless either the comment has to be split to
16337 satisfy the line length limitation, or else the next line contains a
16338 whole line comment that is considered a continuation of this end-of-line
16339 comment (because it starts at the same position).
16341 cases, the start of the end-of-line comment is moved right to the nearest
16342 multiple of the indentation level.
16343 This may result in a ``line overflow'' (the right-shifted comment extending
16344 beyond the maximum line length), in which case the comment is split as
16347 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16348 (GNAT-style comment line indentation)
16349 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16350 (reference-manual comment line indentation).
16351 With reference-manual style, a whole-line comment is indented as if it
16352 were a declaration or statement at the same place
16353 (i.e., according to the indentation of the preceding line(s)).
16354 With GNAT style, a whole-line comment that is immediately followed by an
16355 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16356 word @b{begin}, is indented based on the construct that follows it.
16359 @smallexample @c ada
16371 Reference-manual indentation produces:
16373 @smallexample @c ada
16385 while GNAT-style indentation produces:
16387 @smallexample @c ada
16399 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16400 (GNAT style comment beginning) has the following
16405 For each whole-line comment that does not end with two hyphens,
16406 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16407 to ensure that there are at least two spaces between these hyphens and the
16408 first non-blank character of the comment.
16412 For an end-of-line comment, if in the original source the next line is a
16413 whole-line comment that starts at the same position
16414 as the end-of-line comment,
16415 then the whole-line comment (and all whole-line comments
16416 that follow it and that start at the same position)
16417 will start at this position in the output file.
16420 That is, if in the original source we have:
16422 @smallexample @c ada
16425 A := B + C; -- B must be in the range Low1..High1
16426 -- C must be in the range Low2..High2
16427 --B+C will be in the range Low1+Low2..High1+High2
16433 Then in the formatted source we get
16435 @smallexample @c ada
16438 A := B + C; -- B must be in the range Low1..High1
16439 -- C must be in the range Low2..High2
16440 -- B+C will be in the range Low1+Low2..High1+High2
16446 A comment that exceeds the line length limit will be split.
16448 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16449 the line belongs to a reformattable block, splitting the line generates a
16450 @command{gnatpp} warning.
16451 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16452 comments may be reformatted in typical
16453 word processor style (that is, moving words between lines and putting as
16454 many words in a line as possible).
16457 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16458 that has a special format (that is, a character that is neither a letter nor digit
16459 not white space nor line break immediately following the leading @code{--} of
16460 the comment) should be without any change moved from the argument source
16461 into reformatted source. This switch allows to preserve comments that are used
16462 as a special marks in the code (e.g.@: SPARK annotation).
16464 @node Construct Layout
16465 @subsection Construct Layout
16468 In several cases the suggested layout in the Ada Reference Manual includes
16469 an extra level of indentation that many programmers prefer to avoid. The
16470 affected cases include:
16474 @item Record type declaration (RM 3.8)
16476 @item Record representation clause (RM 13.5.1)
16478 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16480 @item Block statement in case if a block has a statement identifier (RM 5.6)
16484 In compact mode (when GNAT style layout or compact layout is set),
16485 the pretty printer uses one level of indentation instead
16486 of two. This is achieved in the record definition and record representation
16487 clause cases by putting the @code{record} keyword on the same line as the
16488 start of the declaration or representation clause, and in the block and loop
16489 case by putting the block or loop header on the same line as the statement
16493 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16494 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16495 layout on the one hand, and uncompact layout
16496 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16497 can be illustrated by the following examples:
16501 @multitable @columnfractions .5 .5
16502 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16505 @smallexample @c ada
16512 @smallexample @c ada
16521 @smallexample @c ada
16523 a at 0 range 0 .. 31;
16524 b at 4 range 0 .. 31;
16528 @smallexample @c ada
16531 a at 0 range 0 .. 31;
16532 b at 4 range 0 .. 31;
16537 @smallexample @c ada
16545 @smallexample @c ada
16555 @smallexample @c ada
16556 Clear : for J in 1 .. 10 loop
16561 @smallexample @c ada
16563 for J in 1 .. 10 loop
16574 GNAT style, compact layout Uncompact layout
16576 type q is record type q is
16577 a : integer; record
16578 b : integer; a : integer;
16579 end record; b : integer;
16582 for q use record for q use
16583 a at 0 range 0 .. 31; record
16584 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16585 end record; b at 4 range 0 .. 31;
16588 Block : declare Block :
16589 A : Integer := 3; declare
16590 begin A : Integer := 3;
16592 end Block; Proc (A, A);
16595 Clear : for J in 1 .. 10 loop Clear :
16596 A (J) := 0; for J in 1 .. 10 loop
16597 end loop Clear; A (J) := 0;
16604 A further difference between GNAT style layout and compact layout is that
16605 GNAT style layout inserts empty lines as separation for
16606 compound statements, return statements and bodies.
16608 Note that the layout specified by
16609 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16610 for named block and loop statements overrides the layout defined by these
16611 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16612 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16613 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16616 @subsection Name Casing
16619 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16620 the same casing as the corresponding defining identifier.
16622 You control the casing for defining occurrences via the
16623 @option{^-n^/NAME_CASING^} switch.
16625 With @option{-nD} (``as declared'', which is the default),
16628 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16630 defining occurrences appear exactly as in the source file
16631 where they are declared.
16632 The other ^values for this switch^options for this qualifier^ ---
16633 @option{^-nU^UPPER_CASE^},
16634 @option{^-nL^LOWER_CASE^},
16635 @option{^-nM^MIXED_CASE^} ---
16637 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16638 If @command{gnatpp} changes the casing of a defining
16639 occurrence, it analogously changes the casing of all the
16640 usage occurrences of this name.
16642 If the defining occurrence of a name is not in the source compilation unit
16643 currently being processed by @command{gnatpp}, the casing of each reference to
16644 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16645 switch (subject to the dictionary file mechanism described below).
16646 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16648 casing for the defining occurrence of the name.
16650 Some names may need to be spelled with casing conventions that are not
16651 covered by the upper-, lower-, and mixed-case transformations.
16652 You can arrange correct casing by placing such names in a
16653 @emph{dictionary file},
16654 and then supplying a @option{^-D^/DICTIONARY^} switch.
16655 The casing of names from dictionary files overrides
16656 any @option{^-n^/NAME_CASING^} switch.
16658 To handle the casing of Ada predefined names and the names from GNAT libraries,
16659 @command{gnatpp} assumes a default dictionary file.
16660 The name of each predefined entity is spelled with the same casing as is used
16661 for the entity in the @cite{Ada Reference Manual}.
16662 The name of each entity in the GNAT libraries is spelled with the same casing
16663 as is used in the declaration of that entity.
16665 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16666 default dictionary file.
16667 Instead, the casing for predefined and GNAT-defined names will be established
16668 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16669 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16670 will appear as just shown,
16671 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16672 To ensure that even such names are rendered in uppercase,
16673 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16674 (or else, less conveniently, place these names in upper case in a dictionary
16677 A dictionary file is
16678 a plain text file; each line in this file can be either a blank line
16679 (containing only space characters and ASCII.HT characters), an Ada comment
16680 line, or the specification of exactly one @emph{casing schema}.
16682 A casing schema is a string that has the following syntax:
16686 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16688 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16693 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16694 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16696 The casing schema string can be followed by white space and/or an Ada-style
16697 comment; any amount of white space is allowed before the string.
16699 If a dictionary file is passed as
16701 the value of a @option{-D@var{file}} switch
16704 an option to the @option{/DICTIONARY} qualifier
16707 simple name and every identifier, @command{gnatpp} checks if the dictionary
16708 defines the casing for the name or for some of its parts (the term ``subword''
16709 is used below to denote the part of a name which is delimited by ``_'' or by
16710 the beginning or end of the word and which does not contain any ``_'' inside):
16714 if the whole name is in the dictionary, @command{gnatpp} uses for this name
16715 the casing defined by the dictionary; no subwords are checked for this word
16718 for every subword @command{gnatpp} checks if the dictionary contains the
16719 corresponding string of the form @code{*@var{simple_identifier}*},
16720 and if it does, the casing of this @var{simple_identifier} is used
16724 if the whole name does not contain any ``_'' inside, and if for this name
16725 the dictionary contains two entries - one of the form @var{identifier},
16726 and another - of the form *@var{simple_identifier}*, then the first one
16727 is applied to define the casing of this name
16730 if more than one dictionary file is passed as @command{gnatpp} switches, each
16731 dictionary adds new casing exceptions and overrides all the existing casing
16732 exceptions set by the previous dictionaries
16735 when @command{gnatpp} checks if the word or subword is in the dictionary,
16736 this check is not case sensitive
16740 For example, suppose we have the following source to reformat:
16742 @smallexample @c ada
16745 name1 : integer := 1;
16746 name4_name3_name2 : integer := 2;
16747 name2_name3_name4 : Boolean;
16750 name2_name3_name4 := name4_name3_name2 > name1;
16756 And suppose we have two dictionaries:
16773 If @command{gnatpp} is called with the following switches:
16777 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
16780 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
16785 then we will get the following name casing in the @command{gnatpp} output:
16787 @smallexample @c ada
16790 NAME1 : Integer := 1;
16791 Name4_NAME3_Name2 : Integer := 2;
16792 Name2_NAME3_Name4 : Boolean;
16795 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
16800 @c *********************************
16801 @node The GNAT Metric Tool gnatmetric
16802 @chapter The GNAT Metric Tool @command{gnatmetric}
16804 @cindex Metric tool
16807 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
16808 for computing various program metrics.
16809 It takes an Ada source file as input and generates a file containing the
16810 metrics data as output. Various switches control which
16811 metrics are computed and output.
16813 @command{gnatmetric} generates and uses the ASIS
16814 tree for the input source and thus requires the input to be syntactically and
16815 semantically legal.
16816 If this condition is not met, @command{gnatmetric} will generate
16817 an error message; no metric information for this file will be
16818 computed and reported.
16820 If the compilation unit contained in the input source depends semantically
16821 upon units in files located outside the current directory, you have to provide
16822 the source search path when invoking @command{gnatmetric}.
16823 If it depends semantically upon units that are contained
16824 in files with names that do not follow the GNAT file naming rules, you have to
16825 provide the configuration file describing the corresponding naming scheme (see
16826 the description of the @command{gnatmetric} switches below.)
16827 Alternatively, you may use a project file and invoke @command{gnatmetric}
16828 through the @command{gnat} driver.
16830 The @command{gnatmetric} command has the form
16833 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
16840 @var{switches} specify the metrics to compute and define the destination for
16844 Each @var{filename} is the name (including the extension) of a source
16845 file to process. ``Wildcards'' are allowed, and
16846 the file name may contain path information.
16847 If no @var{filename} is supplied, then the @var{switches} list must contain
16849 @option{-files} switch (@pxref{Other gnatmetric Switches}).
16850 Including both a @option{-files} switch and one or more
16851 @var{filename} arguments is permitted.
16854 @samp{-cargs @var{gcc_switches}} is a list of switches for
16855 @command{gcc}. They will be passed on to all compiler invocations made by
16856 @command{gnatmetric} to generate the ASIS trees. Here you can provide
16857 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
16858 and use the @option{-gnatec} switch to set the configuration file.
16862 * Switches for gnatmetric::
16865 @node Switches for gnatmetric
16866 @section Switches for @command{gnatmetric}
16869 The following subsections describe the various switches accepted by
16870 @command{gnatmetric}, organized by category.
16873 * Output Files Control::
16874 * Disable Metrics For Local Units::
16875 * Specifying a set of metrics to compute::
16876 * Other gnatmetric Switches::
16877 * Generate project-wide metrics::
16880 @node Output Files Control
16881 @subsection Output File Control
16882 @cindex Output file control in @command{gnatmetric}
16885 @command{gnatmetric} has two output formats. It can generate a
16886 textual (human-readable) form, and also XML. By default only textual
16887 output is generated.
16889 When generating the output in textual form, @command{gnatmetric} creates
16890 for each Ada source file a corresponding text file
16891 containing the computed metrics, except for the case when the set of metrics
16892 specified by gnatmetric parameters consists only of metrics that are computed
16893 for the whole set of analyzed sources, but not for each Ada source.
16894 By default, this file is placed in the same directory as where the source
16895 file is located, and its name is obtained
16896 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
16899 All the output information generated in XML format is placed in a single
16900 file. By default this file is placed in the current directory and has the
16901 name ^@file{metrix.xml}^@file{METRIX$XML}^.
16903 Some of the computed metrics are summed over the units passed to
16904 @command{gnatmetric}; for example, the total number of lines of code.
16905 By default this information is sent to @file{stdout}, but a file
16906 can be specified with the @option{-og} switch.
16908 The following switches control the @command{gnatmetric} output:
16911 @cindex @option{^-x^/XML^} (@command{gnatmetric})
16913 Generate the XML output
16915 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
16916 @item ^-nt^/NO_TEXT^
16917 Do not generate the output in text form (implies @option{^-x^/XML^})
16919 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
16920 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
16921 Put textual files with detailed metrics into @var{output_dir}
16923 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
16924 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
16925 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
16926 in the name of the output file.
16928 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
16929 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
16930 Put global metrics into @var{file_name}
16932 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
16933 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
16934 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
16936 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
16937 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
16938 Use ``short'' source file names in the output. (The @command{gnatmetric}
16939 output includes the name(s) of the Ada source file(s) from which the metrics
16940 are computed. By default each name includes the absolute path. The
16941 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
16942 to exclude all directory information from the file names that are output.)
16946 @node Disable Metrics For Local Units
16947 @subsection Disable Metrics For Local Units
16948 @cindex Disable Metrics For Local Units in @command{gnatmetric}
16951 @command{gnatmetric} relies on the GNAT compilation model @minus{}
16953 unit per one source file. It computes line metrics for the whole source
16954 file, and it also computes syntax
16955 and complexity metrics for the file's outermost unit.
16957 By default, @command{gnatmetric} will also compute all metrics for certain
16958 kinds of locally declared program units:
16962 subprogram (and generic subprogram) bodies;
16965 package (and generic package) specs and bodies;
16968 task object and type specifications and bodies;
16971 protected object and type specifications and bodies.
16975 These kinds of entities will be referred to as
16976 @emph{eligible local program units}, or simply @emph{eligible local units},
16977 @cindex Eligible local unit (for @command{gnatmetric})
16978 in the discussion below.
16980 Note that a subprogram declaration, generic instantiation,
16981 or renaming declaration only receives metrics
16982 computation when it appear as the outermost entity
16985 Suppression of metrics computation for eligible local units can be
16986 obtained via the following switch:
16989 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
16990 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
16991 Do not compute detailed metrics for eligible local program units
16995 @node Specifying a set of metrics to compute
16996 @subsection Specifying a set of metrics to compute
16999 By default all the metrics are computed and reported. The switches
17000 described in this subsection allow you to control, on an individual
17001 basis, whether metrics are computed and
17002 reported. If at least one positive metric
17003 switch is specified (that is, a switch that defines that a given
17004 metric or set of metrics is to be computed), then only
17005 explicitly specified metrics are reported.
17008 * Line Metrics Control::
17009 * Syntax Metrics Control::
17010 * Complexity Metrics Control::
17011 * Object-Oriented Metrics Control::
17014 @node Line Metrics Control
17015 @subsubsection Line Metrics Control
17016 @cindex Line metrics control in @command{gnatmetric}
17019 For any (legal) source file, and for each of its
17020 eligible local program units, @command{gnatmetric} computes the following
17025 the total number of lines;
17028 the total number of code lines (i.e., non-blank lines that are not comments)
17031 the number of comment lines
17034 the number of code lines containing end-of-line comments;
17037 the comment percentage: the ratio between the number of lines that contain
17038 comments and the number of all non-blank lines, expressed as a percentage;
17041 the number of empty lines and lines containing only space characters and/or
17042 format effectors (blank lines)
17045 the average number of code lines in subprogram bodies, task bodies, entry
17046 bodies and statement sequences in package bodies (this metric is only computed
17047 across the whole set of the analyzed units)
17052 @command{gnatmetric} sums the values of the line metrics for all the
17053 files being processed and then generates the cumulative results. The tool
17054 also computes for all the files being processed the average number of code
17057 You can use the following switches to select the specific line metrics
17058 to be computed and reported.
17061 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17064 @cindex @option{--no-lines@var{x}}
17067 @item ^--lines-all^/LINE_COUNT_METRICS=ALL_ON^
17068 Report all the line metrics
17070 @item ^--no-lines-all^/LINE_COUNT_METRICS=ALL_OFF^
17071 Do not report any of line metrics
17073 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES_ON^
17074 Report the number of all lines
17076 @item ^--no-lines^/LINE_COUNT_METRICS=ALL_LINES_OFF^
17077 Do not report the number of all lines
17079 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES_ON^
17080 Report the number of code lines
17082 @item ^--no-lines-code^/LINE_COUNT_METRICS=CODE_LINES_OFF^
17083 Do not report the number of code lines
17085 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_ON^
17086 Report the number of comment lines
17088 @item ^--no-lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_OFF^
17089 Do not report the number of comment lines
17091 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_ON^
17092 Report the number of code lines containing
17093 end-of-line comments
17095 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_OFF^
17096 Do not report the number of code lines containing
17097 end-of-line comments
17099 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_ON^
17100 Report the comment percentage in the program text
17102 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_OFF^
17103 Do not report the comment percentage in the program text
17105 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_ON^
17106 Report the number of blank lines
17108 @item ^--no-lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_OFF^
17109 Do not report the number of blank lines
17111 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_ON^
17112 Report the average number of code lines in subprogram bodies, task bodies,
17113 entry bodies and statement sequences in package bodies. The metric is computed
17114 and reported for the whole set of processed Ada sources only.
17116 @item ^--no-lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_OFF^
17117 Do not report the average number of code lines in subprogram bodies,
17118 task bodies, entry bodies and statement sequences in package bodies.
17122 @node Syntax Metrics Control
17123 @subsubsection Syntax Metrics Control
17124 @cindex Syntax metrics control in @command{gnatmetric}
17127 @command{gnatmetric} computes various syntactic metrics for the
17128 outermost unit and for each eligible local unit:
17131 @item LSLOC (``Logical Source Lines Of Code'')
17132 The total number of declarations and the total number of statements
17134 @item Maximal static nesting level of inner program units
17136 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17137 package, a task unit, a protected unit, a
17138 protected entry, a generic unit, or an explicitly declared subprogram other
17139 than an enumeration literal.''
17141 @item Maximal nesting level of composite syntactic constructs
17142 This corresponds to the notion of the
17143 maximum nesting level in the GNAT built-in style checks
17144 (@pxref{Style Checking})
17148 For the outermost unit in the file, @command{gnatmetric} additionally computes
17149 the following metrics:
17152 @item Public subprograms
17153 This metric is computed for package specs. It is the
17154 number of subprograms and generic subprograms declared in the visible
17155 part (including the visible part of nested packages, protected objects, and
17158 @item All subprograms
17159 This metric is computed for bodies and subunits. The
17160 metric is equal to a total number of subprogram bodies in the compilation
17162 Neither generic instantiations nor renamings-as-a-body nor body stubs
17163 are counted. Any subprogram body is counted, independently of its nesting
17164 level and enclosing constructs. Generic bodies and bodies of protected
17165 subprograms are counted in the same way as ``usual'' subprogram bodies.
17168 This metric is computed for package specs and
17169 generic package declarations. It is the total number of types
17170 that can be referenced from outside this compilation unit, plus the
17171 number of types from all the visible parts of all the visible generic
17172 packages. Generic formal types are not counted. Only types, not subtypes,
17176 Along with the total number of public types, the following
17177 types are counted and reported separately:
17184 Root tagged types (abstract, non-abstract, private, non-private). Type
17185 extensions are @emph{not} counted
17188 Private types (including private extensions)
17199 This metric is computed for any compilation unit. It is equal to the total
17200 number of the declarations of different types given in the compilation unit.
17201 The private and the corresponding full type declaration are counted as one
17202 type declaration. Incomplete type declarations and generic formal types
17204 No distinction is made among different kinds of types (abstract,
17205 private etc.); the total number of types is computed and reported.
17210 By default, all the syntax metrics are computed and reported. You can use the
17211 following switches to select specific syntax metrics.
17215 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17218 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17221 @item ^--syntax-all^/SYNTAX_METRICS=ALL_ON^
17222 Report all the syntax metrics
17224 @item ^--no-syntax-all^/ALL_OFF^
17225 Do not report any of syntax metrics
17227 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS_ON^
17228 Report the total number of declarations
17230 @item ^--no-declarations^/SYNTAX_METRICS=DECLARATIONS_OFF^
17231 Do not report the total number of declarations
17233 @item ^--statements^/SYNTAX_METRICS=STATEMENTS_ON^
17234 Report the total number of statements
17236 @item ^--no-statements^/SYNTAX_METRICS=STATEMENTS_OFF^
17237 Do not report the total number of statements
17239 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_ON^
17240 Report the number of public subprograms in a compilation unit
17242 @item ^--no-public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_OFF^
17243 Do not report the number of public subprograms in a compilation unit
17245 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_ON^
17246 Report the number of all the subprograms in a compilation unit
17248 @item ^--no-all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_OFF^
17249 Do not report the number of all the subprograms in a compilation unit
17251 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES_ON^
17252 Report the number of public types in a compilation unit
17254 @item ^--no-public-types^/SYNTAX_METRICS=PUBLIC_TYPES_OFF^
17255 Do not report the number of public types in a compilation unit
17257 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES_ON^
17258 Report the number of all the types in a compilation unit
17260 @item ^--no-all-types^/SYNTAX_METRICS=ALL_TYPES_OFF^
17261 Do not report the number of all the types in a compilation unit
17263 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_ON^
17264 Report the maximal program unit nesting level
17266 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17267 Do not report the maximal program unit nesting level
17269 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_ON^
17270 Report the maximal construct nesting level
17272 @item ^--no-construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_OFF^
17273 Do not report the maximal construct nesting level
17277 @node Complexity Metrics Control
17278 @subsubsection Complexity Metrics Control
17279 @cindex Complexity metrics control in @command{gnatmetric}
17282 For a program unit that is an executable body (a subprogram body (including
17283 generic bodies), task body, entry body or a package body containing
17284 its own statement sequence) @command{gnatmetric} computes the following
17285 complexity metrics:
17289 McCabe cyclomatic complexity;
17292 McCabe essential complexity;
17295 maximal loop nesting level
17300 The McCabe complexity metrics are defined
17301 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17303 According to McCabe, both control statements and short-circuit control forms
17304 should be taken into account when computing cyclomatic complexity. For each
17305 body, we compute three metric values:
17309 the complexity introduced by control
17310 statements only, without taking into account short-circuit forms,
17313 the complexity introduced by short-circuit control forms only, and
17317 cyclomatic complexity, which is the sum of these two values.
17321 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17322 the code in the exception handlers and in all the nested program units.
17324 By default, all the complexity metrics are computed and reported.
17325 For more fine-grained control you can use
17326 the following switches:
17329 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17332 @cindex @option{--no-complexity@var{x}}
17335 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL_ON^
17336 Report all the complexity metrics
17338 @item ^--no-complexity-all^/COMPLEXITY_METRICS=ALL_OFF^
17339 Do not report any of complexity metrics
17341 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_ON^
17342 Report the McCabe Cyclomatic Complexity
17344 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_OFF^
17345 Do not report the McCabe Cyclomatic Complexity
17347 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_ON^
17348 Report the Essential Complexity
17350 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_OFF^
17351 Do not report the Essential Complexity
17353 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17354 Report maximal loop nesting level
17356 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_OFF^
17357 Do not report maximal loop nesting level
17359 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_ON^
17360 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17361 task bodies, entry bodies and statement sequences in package bodies.
17362 The metric is computed and reported for whole set of processed Ada sources
17365 @item ^--no-complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_OFF^
17366 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17367 bodies, task bodies, entry bodies and statement sequences in package bodies
17369 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17370 @item ^-ne^/NO_EXITS_AS_GOTOS^
17371 Do not consider @code{exit} statements as @code{goto}s when
17372 computing Essential Complexity
17377 @node Object-Oriented Metrics Control
17378 @subsubsection Object-Oriented Metrics Control
17379 @cindex Object-Oriented metrics control in @command{gnatmetric}
17382 @cindex Coupling metrics (in in @command{gnatmetric})
17383 Coupling metrics are object-oriented metrics that measure the
17384 dependencies between a given class (or a group of classes) and the
17385 ``external world'' (that is, the other classes in the program). In this
17386 subsection the term ``class'' is used in its
17387 traditional object-oriented programming sense
17388 (an instantiable module that contains data and/or method members).
17389 A @emph{category} (of classes)
17390 is a group of closely related classes that are reused and/or
17393 A class @code{K}'s @emph{efferent coupling} is the number of classes
17394 that @code{K} depends upon.
17395 A category's efferent coupling is the number of classes outside the
17396 category that the classes inside the category depend upon.
17398 A class @code{K}'s @emph{afferent coupling} is the number of classes
17399 that depend upon @code{K}.
17400 A category's afferent coupling is the number of classes outside the
17401 category that depend on classes belonging to the category.
17403 Ada's implementation of the object-oriented paradigm does not use the
17404 traditional class notion, so the definition of the coupling
17405 metrics for Ada maps the class and class category notions
17406 onto Ada constructs.
17408 For the coupling metrics, several kinds of modules -- a library package,
17409 a library generic package, and a library generic package instantiation --
17410 that define a tagged type or an interface type are
17411 considered to be a class. A category consists of a library package (or
17412 a library generic package) that defines a tagged or an interface type,
17413 together with all its descendant (generic) packages that define tagged
17414 or interface types. For any package counted as a class,
17415 its body (if any) is considered
17416 together with its spec when counting the dependencies. For dependencies
17417 between classes, the Ada semantic dependencies are considered.
17418 For coupling metrics, only dependencies on units that are considered as
17419 classes, are considered.
17421 When computing coupling metrics, @command{gnatmetric} counts only
17422 dependencies between units that are arguments of the gnatmetric call.
17423 Coupling metrics are program-wide (or project-wide) metrics, so to
17424 get a valid result, you should call @command{gnatmetric} for
17425 the whole set of sources that make up your program. It can be done
17426 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17427 option (see See @ref{The GNAT Driver and Project Files} for details.
17429 By default, all the coupling metrics are disabled. You can use the following
17430 switches to specify the coupling metrics to be computed and reported:
17435 @cindex @option{--package@var{x}} (@command{gnatmetric})
17436 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17437 @cindex @option{--category@var{x}} (@command{gnatmetric})
17438 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17442 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17445 @item ^--coupling-all^/COUPLING_METRICS=ALL_ON^
17446 Report all the coupling metrics
17448 @item ^--no-coupling-all^/COUPLING_METRICS=ALL_OFF^
17449 Do not report any of metrics
17451 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_ON^
17452 Report package efferent coupling
17454 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_OFF^
17455 Do not report package efferent coupling
17457 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_ON^
17458 Report package afferent coupling
17460 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_OFF^
17461 Do not report package afferent coupling
17463 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_ON^
17464 Report category efferent coupling
17466 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_OFF^
17467 Do not report category efferent coupling
17469 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_ON^
17470 Report category afferent coupling
17472 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_OFF^
17473 Do not report category afferent coupling
17477 @node Other gnatmetric Switches
17478 @subsection Other @code{gnatmetric} Switches
17481 Additional @command{gnatmetric} switches are as follows:
17484 @item ^-files @var{filename}^/FILES=@var{filename}^
17485 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17486 Take the argument source files from the specified file. This file should be an
17487 ordinary text file containing file names separated by spaces or
17488 line breaks. You can use this switch more then once in the same call to
17489 @command{gnatmetric}. You also can combine this switch with
17490 an explicit list of files.
17492 @item ^-v^/VERBOSE^
17493 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17495 @command{gnatmetric} generates version information and then
17496 a trace of sources being processed.
17498 @item ^-dv^/DEBUG_OUTPUT^
17499 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17501 @command{gnatmetric} generates various messages useful to understand what
17502 happens during the metrics computation
17505 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17509 @node Generate project-wide metrics
17510 @subsection Generate project-wide metrics
17512 In order to compute metrics on all units of a given project, you can use
17513 the @command{gnat} driver along with the @option{-P} option:
17519 If the project @code{proj} depends upon other projects, you can compute
17520 the metrics on the project closure using the @option{-U} option:
17522 gnat metric -Pproj -U
17526 Finally, if not all the units are relevant to a particular main
17527 program in the project closure, you can generate metrics for the set
17528 of units needed to create a given main program (unit closure) using
17529 the @option{-U} option followed by the name of the main unit:
17531 gnat metric -Pproj -U main
17535 @c ***********************************
17536 @node File Name Krunching Using gnatkr
17537 @chapter File Name Krunching Using @code{gnatkr}
17541 This chapter discusses the method used by the compiler to shorten
17542 the default file names chosen for Ada units so that they do not
17543 exceed the maximum length permitted. It also describes the
17544 @code{gnatkr} utility that can be used to determine the result of
17545 applying this shortening.
17549 * Krunching Method::
17550 * Examples of gnatkr Usage::
17554 @section About @code{gnatkr}
17557 The default file naming rule in GNAT
17558 is that the file name must be derived from
17559 the unit name. The exact default rule is as follows:
17562 Take the unit name and replace all dots by hyphens.
17564 If such a replacement occurs in the
17565 second character position of a name, and the first character is
17566 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17567 then replace the dot by the character
17568 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17569 instead of a minus.
17571 The reason for this exception is to avoid clashes
17572 with the standard names for children of System, Ada, Interfaces,
17573 and GNAT, which use the prefixes
17574 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17577 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17578 switch of the compiler activates a ``krunching''
17579 circuit that limits file names to nn characters (where nn is a decimal
17580 integer). For example, using OpenVMS,
17581 where the maximum file name length is
17582 39, the value of nn is usually set to 39, but if you want to generate
17583 a set of files that would be usable if ported to a system with some
17584 different maximum file length, then a different value can be specified.
17585 The default value of 39 for OpenVMS need not be specified.
17587 The @code{gnatkr} utility can be used to determine the krunched name for
17588 a given file, when krunched to a specified maximum length.
17591 @section Using @code{gnatkr}
17594 The @code{gnatkr} command has the form
17598 $ gnatkr @var{name} @ovar{length}
17604 $ gnatkr @var{name} /COUNT=nn
17609 @var{name} is the uncrunched file name, derived from the name of the unit
17610 in the standard manner described in the previous section (i.e., in particular
17611 all dots are replaced by hyphens). The file name may or may not have an
17612 extension (defined as a suffix of the form period followed by arbitrary
17613 characters other than period). If an extension is present then it will
17614 be preserved in the output. For example, when krunching @file{hellofile.ads}
17615 to eight characters, the result will be hellofil.ads.
17617 Note: for compatibility with previous versions of @code{gnatkr} dots may
17618 appear in the name instead of hyphens, but the last dot will always be
17619 taken as the start of an extension. So if @code{gnatkr} is given an argument
17620 such as @file{Hello.World.adb} it will be treated exactly as if the first
17621 period had been a hyphen, and for example krunching to eight characters
17622 gives the result @file{hellworl.adb}.
17624 Note that the result is always all lower case (except on OpenVMS where it is
17625 all upper case). Characters of the other case are folded as required.
17627 @var{length} represents the length of the krunched name. The default
17628 when no argument is given is ^8^39^ characters. A length of zero stands for
17629 unlimited, in other words do not chop except for system files where the
17630 implied crunching length is always eight characters.
17633 The output is the krunched name. The output has an extension only if the
17634 original argument was a file name with an extension.
17636 @node Krunching Method
17637 @section Krunching Method
17640 The initial file name is determined by the name of the unit that the file
17641 contains. The name is formed by taking the full expanded name of the
17642 unit and replacing the separating dots with hyphens and
17643 using ^lowercase^uppercase^
17644 for all letters, except that a hyphen in the second character position is
17645 replaced by a ^tilde^dollar sign^ if the first character is
17646 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17647 The extension is @code{.ads} for a
17648 spec and @code{.adb} for a body.
17649 Krunching does not affect the extension, but the file name is shortened to
17650 the specified length by following these rules:
17654 The name is divided into segments separated by hyphens, tildes or
17655 underscores and all hyphens, tildes, and underscores are
17656 eliminated. If this leaves the name short enough, we are done.
17659 If the name is too long, the longest segment is located (left-most
17660 if there are two of equal length), and shortened by dropping
17661 its last character. This is repeated until the name is short enough.
17663 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17664 to fit the name into 8 characters as required by some operating systems.
17667 our-strings-wide_fixed 22
17668 our strings wide fixed 19
17669 our string wide fixed 18
17670 our strin wide fixed 17
17671 our stri wide fixed 16
17672 our stri wide fixe 15
17673 our str wide fixe 14
17674 our str wid fixe 13
17680 Final file name: oustwifi.adb
17684 The file names for all predefined units are always krunched to eight
17685 characters. The krunching of these predefined units uses the following
17686 special prefix replacements:
17690 replaced by @file{^a^A^-}
17693 replaced by @file{^g^G^-}
17696 replaced by @file{^i^I^-}
17699 replaced by @file{^s^S^-}
17702 These system files have a hyphen in the second character position. That
17703 is why normal user files replace such a character with a
17704 ^tilde^dollar sign^, to
17705 avoid confusion with system file names.
17707 As an example of this special rule, consider
17708 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
17711 ada-strings-wide_fixed 22
17712 a- strings wide fixed 18
17713 a- string wide fixed 17
17714 a- strin wide fixed 16
17715 a- stri wide fixed 15
17716 a- stri wide fixe 14
17717 a- str wide fixe 13
17723 Final file name: a-stwifi.adb
17727 Of course no file shortening algorithm can guarantee uniqueness over all
17728 possible unit names, and if file name krunching is used then it is your
17729 responsibility to ensure that no name clashes occur. The utility
17730 program @code{gnatkr} is supplied for conveniently determining the
17731 krunched name of a file.
17733 @node Examples of gnatkr Usage
17734 @section Examples of @code{gnatkr} Usage
17741 $ gnatkr very_long_unit_name.ads --> velounna.ads
17742 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
17743 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
17744 $ gnatkr grandparent-parent-child --> grparchi
17746 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
17747 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
17750 @node Preprocessing Using gnatprep
17751 @chapter Preprocessing Using @code{gnatprep}
17755 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
17757 Although designed for use with GNAT, @code{gnatprep} does not depend on any
17758 special GNAT features.
17759 For further discussion of conditional compilation in general, see
17760 @ref{Conditional Compilation}.
17763 * Preprocessing Symbols::
17765 * Switches for gnatprep::
17766 * Form of Definitions File::
17767 * Form of Input Text for gnatprep::
17770 @node Preprocessing Symbols
17771 @section Preprocessing Symbols
17774 Preprocessing symbols are defined in definition files and referred to in
17775 sources to be preprocessed. A Preprocessing symbol is an identifier, following
17776 normal Ada (case-insensitive) rules for its syntax, with the restriction that
17777 all characters need to be in the ASCII set (no accented letters).
17779 @node Using gnatprep
17780 @section Using @code{gnatprep}
17783 To call @code{gnatprep} use
17786 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
17793 is an optional sequence of switches as described in the next section.
17796 is the full name of the input file, which is an Ada source
17797 file containing preprocessor directives.
17800 is the full name of the output file, which is an Ada source
17801 in standard Ada form. When used with GNAT, this file name will
17802 normally have an ads or adb suffix.
17805 is the full name of a text file containing definitions of
17806 preprocessing symbols to be referenced by the preprocessor. This argument is
17807 optional, and can be replaced by the use of the @option{-D} switch.
17811 @node Switches for gnatprep
17812 @section Switches for @code{gnatprep}
17817 @item ^-b^/BLANK_LINES^
17818 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
17819 Causes both preprocessor lines and the lines deleted by
17820 preprocessing to be replaced by blank lines in the output source file,
17821 preserving line numbers in the output file.
17823 @item ^-c^/COMMENTS^
17824 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
17825 Causes both preprocessor lines and the lines deleted
17826 by preprocessing to be retained in the output source as comments marked
17827 with the special string @code{"--! "}. This option will result in line numbers
17828 being preserved in the output file.
17830 @item ^-C^/REPLACE_IN_COMMENTS^
17831 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
17832 Causes comments to be scanned. Normally comments are ignored by gnatprep.
17833 If this option is specified, then comments are scanned and any $symbol
17834 substitutions performed as in program text. This is particularly useful
17835 when structured comments are used (e.g., when writing programs in the
17836 SPARK dialect of Ada). Note that this switch is not available when
17837 doing integrated preprocessing (it would be useless in this context
17838 since comments are ignored by the compiler in any case).
17840 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
17841 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
17842 Defines a new preprocessing symbol, associated with value. If no value is given
17843 on the command line, then symbol is considered to be @code{True}. This switch
17844 can be used in place of a definition file.
17848 @cindex @option{/REMOVE} (@command{gnatprep})
17849 This is the default setting which causes lines deleted by preprocessing
17850 to be entirely removed from the output file.
17853 @item ^-r^/REFERENCE^
17854 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
17855 Causes a @code{Source_Reference} pragma to be generated that
17856 references the original input file, so that error messages will use
17857 the file name of this original file. The use of this switch implies
17858 that preprocessor lines are not to be removed from the file, so its
17859 use will force @option{^-b^/BLANK_LINES^} mode if
17860 @option{^-c^/COMMENTS^}
17861 has not been specified explicitly.
17863 Note that if the file to be preprocessed contains multiple units, then
17864 it will be necessary to @code{gnatchop} the output file from
17865 @code{gnatprep}. If a @code{Source_Reference} pragma is present
17866 in the preprocessed file, it will be respected by
17867 @code{gnatchop ^-r^/REFERENCE^}
17868 so that the final chopped files will correctly refer to the original
17869 input source file for @code{gnatprep}.
17871 @item ^-s^/SYMBOLS^
17872 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
17873 Causes a sorted list of symbol names and values to be
17874 listed on the standard output file.
17876 @item ^-u^/UNDEFINED^
17877 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
17878 Causes undefined symbols to be treated as having the value FALSE in the context
17879 of a preprocessor test. In the absence of this option, an undefined symbol in
17880 a @code{#if} or @code{#elsif} test will be treated as an error.
17886 Note: if neither @option{-b} nor @option{-c} is present,
17887 then preprocessor lines and
17888 deleted lines are completely removed from the output, unless -r is
17889 specified, in which case -b is assumed.
17892 @node Form of Definitions File
17893 @section Form of Definitions File
17896 The definitions file contains lines of the form
17903 where symbol is a preprocessing symbol, and value is one of the following:
17907 Empty, corresponding to a null substitution
17909 A string literal using normal Ada syntax
17911 Any sequence of characters from the set
17912 (letters, digits, period, underline).
17916 Comment lines may also appear in the definitions file, starting with
17917 the usual @code{--},
17918 and comments may be added to the definitions lines.
17920 @node Form of Input Text for gnatprep
17921 @section Form of Input Text for @code{gnatprep}
17924 The input text may contain preprocessor conditional inclusion lines,
17925 as well as general symbol substitution sequences.
17927 The preprocessor conditional inclusion commands have the form
17932 #if @i{expression} @r{[}then@r{]}
17934 #elsif @i{expression} @r{[}then@r{]}
17936 #elsif @i{expression} @r{[}then@r{]}
17947 In this example, @i{expression} is defined by the following grammar:
17949 @i{expression} ::= <symbol>
17950 @i{expression} ::= <symbol> = "<value>"
17951 @i{expression} ::= <symbol> = <symbol>
17952 @i{expression} ::= <symbol> 'Defined
17953 @i{expression} ::= not @i{expression}
17954 @i{expression} ::= @i{expression} and @i{expression}
17955 @i{expression} ::= @i{expression} or @i{expression}
17956 @i{expression} ::= @i{expression} and then @i{expression}
17957 @i{expression} ::= @i{expression} or else @i{expression}
17958 @i{expression} ::= ( @i{expression} )
17961 The following restriction exists: it is not allowed to have "and" or "or"
17962 following "not" in the same expression without parentheses. For example, this
17969 This should be one of the following:
17977 For the first test (@i{expression} ::= <symbol>) the symbol must have
17978 either the value true or false, that is to say the right-hand of the
17979 symbol definition must be one of the (case-insensitive) literals
17980 @code{True} or @code{False}. If the value is true, then the
17981 corresponding lines are included, and if the value is false, they are
17984 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
17985 the symbol has been defined in the definition file or by a @option{-D}
17986 switch on the command line. Otherwise, the test is false.
17988 The equality tests are case insensitive, as are all the preprocessor lines.
17990 If the symbol referenced is not defined in the symbol definitions file,
17991 then the effect depends on whether or not switch @option{-u}
17992 is specified. If so, then the symbol is treated as if it had the value
17993 false and the test fails. If this switch is not specified, then
17994 it is an error to reference an undefined symbol. It is also an error to
17995 reference a symbol that is defined with a value other than @code{True}
17998 The use of the @code{not} operator inverts the sense of this logical test.
17999 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18000 operators, without parentheses. For example, "if not X or Y then" is not
18001 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18003 The @code{then} keyword is optional as shown
18005 The @code{#} must be the first non-blank character on a line, but
18006 otherwise the format is free form. Spaces or tabs may appear between
18007 the @code{#} and the keyword. The keywords and the symbols are case
18008 insensitive as in normal Ada code. Comments may be used on a
18009 preprocessor line, but other than that, no other tokens may appear on a
18010 preprocessor line. Any number of @code{elsif} clauses can be present,
18011 including none at all. The @code{else} is optional, as in Ada.
18013 The @code{#} marking the start of a preprocessor line must be the first
18014 non-blank character on the line, i.e., it must be preceded only by
18015 spaces or horizontal tabs.
18017 Symbol substitution outside of preprocessor lines is obtained by using
18025 anywhere within a source line, except in a comment or within a
18026 string literal. The identifier
18027 following the @code{$} must match one of the symbols defined in the symbol
18028 definition file, and the result is to substitute the value of the
18029 symbol in place of @code{$symbol} in the output file.
18031 Note that although the substitution of strings within a string literal
18032 is not possible, it is possible to have a symbol whose defined value is
18033 a string literal. So instead of setting XYZ to @code{hello} and writing:
18036 Header : String := "$XYZ";
18040 you should set XYZ to @code{"hello"} and write:
18043 Header : String := $XYZ;
18047 and then the substitution will occur as desired.
18050 @node The GNAT Run-Time Library Builder gnatlbr
18051 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18053 @cindex Library builder
18056 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18057 supplied configuration pragmas.
18060 * Running gnatlbr::
18061 * Switches for gnatlbr::
18062 * Examples of gnatlbr Usage::
18065 @node Running gnatlbr
18066 @section Running @code{gnatlbr}
18069 The @code{gnatlbr} command has the form
18072 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18075 @node Switches for gnatlbr
18076 @section Switches for @code{gnatlbr}
18079 @code{gnatlbr} recognizes the following switches:
18083 @item /CREATE=directory
18084 @cindex @code{/CREATE} (@code{gnatlbr})
18085 Create the new run-time library in the specified directory.
18087 @item /SET=directory
18088 @cindex @code{/SET} (@code{gnatlbr})
18089 Make the library in the specified directory the current run-time library.
18091 @item /DELETE=directory
18092 @cindex @code{/DELETE} (@code{gnatlbr})
18093 Delete the run-time library in the specified directory.
18096 @cindex @code{/CONFIG} (@code{gnatlbr})
18097 With /CREATE: Use the configuration pragmas in the specified file when
18098 building the library.
18100 With /SET: Use the configuration pragmas in the specified file when
18105 @node Examples of gnatlbr Usage
18106 @section Example of @code{gnatlbr} Usage
18109 Contents of VAXFLOAT.ADC:
18110 pragma Float_Representation (VAX_Float);
18112 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18114 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18119 @node The GNAT Library Browser gnatls
18120 @chapter The GNAT Library Browser @code{gnatls}
18122 @cindex Library browser
18125 @code{gnatls} is a tool that outputs information about compiled
18126 units. It gives the relationship between objects, unit names and source
18127 files. It can also be used to check the source dependencies of a unit
18128 as well as various characteristics.
18130 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18131 driver (see @ref{The GNAT Driver and Project Files}).
18135 * Switches for gnatls::
18136 * Examples of gnatls Usage::
18139 @node Running gnatls
18140 @section Running @code{gnatls}
18143 The @code{gnatls} command has the form
18146 $ gnatls switches @var{object_or_ali_file}
18150 The main argument is the list of object or @file{ali} files
18151 (@pxref{The Ada Library Information Files})
18152 for which information is requested.
18154 In normal mode, without additional option, @code{gnatls} produces a
18155 four-column listing. Each line represents information for a specific
18156 object. The first column gives the full path of the object, the second
18157 column gives the name of the principal unit in this object, the third
18158 column gives the status of the source and the fourth column gives the
18159 full path of the source representing this unit.
18160 Here is a simple example of use:
18164 ^./^[]^demo1.o demo1 DIF demo1.adb
18165 ^./^[]^demo2.o demo2 OK demo2.adb
18166 ^./^[]^hello.o h1 OK hello.adb
18167 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18168 ^./^[]^instr.o instr OK instr.adb
18169 ^./^[]^tef.o tef DIF tef.adb
18170 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18171 ^./^[]^tgef.o tgef DIF tgef.adb
18175 The first line can be interpreted as follows: the main unit which is
18177 object file @file{demo1.o} is demo1, whose main source is in
18178 @file{demo1.adb}. Furthermore, the version of the source used for the
18179 compilation of demo1 has been modified (DIF). Each source file has a status
18180 qualifier which can be:
18183 @item OK (unchanged)
18184 The version of the source file used for the compilation of the
18185 specified unit corresponds exactly to the actual source file.
18187 @item MOK (slightly modified)
18188 The version of the source file used for the compilation of the
18189 specified unit differs from the actual source file but not enough to
18190 require recompilation. If you use gnatmake with the qualifier
18191 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18192 MOK will not be recompiled.
18194 @item DIF (modified)
18195 No version of the source found on the path corresponds to the source
18196 used to build this object.
18198 @item ??? (file not found)
18199 No source file was found for this unit.
18201 @item HID (hidden, unchanged version not first on PATH)
18202 The version of the source that corresponds exactly to the source used
18203 for compilation has been found on the path but it is hidden by another
18204 version of the same source that has been modified.
18208 @node Switches for gnatls
18209 @section Switches for @code{gnatls}
18212 @code{gnatls} recognizes the following switches:
18216 @cindex @option{--version} @command{gnatls}
18217 Display Copyright and version, then exit disregarding all other options.
18220 @cindex @option{--help} @command{gnatls}
18221 If @option{--version} was not used, display usage, then exit disregarding
18224 @item ^-a^/ALL_UNITS^
18225 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18226 Consider all units, including those of the predefined Ada library.
18227 Especially useful with @option{^-d^/DEPENDENCIES^}.
18229 @item ^-d^/DEPENDENCIES^
18230 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18231 List sources from which specified units depend on.
18233 @item ^-h^/OUTPUT=OPTIONS^
18234 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18235 Output the list of options.
18237 @item ^-o^/OUTPUT=OBJECTS^
18238 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18239 Only output information about object files.
18241 @item ^-s^/OUTPUT=SOURCES^
18242 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18243 Only output information about source files.
18245 @item ^-u^/OUTPUT=UNITS^
18246 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18247 Only output information about compilation units.
18249 @item ^-files^/FILES^=@var{file}
18250 @cindex @option{^-files^/FILES^} (@code{gnatls})
18251 Take as arguments the files listed in text file @var{file}.
18252 Text file @var{file} may contain empty lines that are ignored.
18253 Each nonempty line should contain the name of an existing file.
18254 Several such switches may be specified simultaneously.
18256 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18257 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18258 @itemx ^-I^/SEARCH=^@var{dir}
18259 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18261 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18262 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18263 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18264 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18265 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18266 flags (@pxref{Switches for gnatmake}).
18268 @item --RTS=@var{rts-path}
18269 @cindex @option{--RTS} (@code{gnatls})
18270 Specifies the default location of the runtime library. Same meaning as the
18271 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18273 @item ^-v^/OUTPUT=VERBOSE^
18274 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18275 Verbose mode. Output the complete source, object and project paths. Do not use
18276 the default column layout but instead use long format giving as much as
18277 information possible on each requested units, including special
18278 characteristics such as:
18281 @item Preelaborable
18282 The unit is preelaborable in the Ada sense.
18285 No elaboration code has been produced by the compiler for this unit.
18288 The unit is pure in the Ada sense.
18290 @item Elaborate_Body
18291 The unit contains a pragma Elaborate_Body.
18294 The unit contains a pragma Remote_Types.
18296 @item Shared_Passive
18297 The unit contains a pragma Shared_Passive.
18300 This unit is part of the predefined environment and cannot be modified
18303 @item Remote_Call_Interface
18304 The unit contains a pragma Remote_Call_Interface.
18310 @node Examples of gnatls Usage
18311 @section Example of @code{gnatls} Usage
18315 Example of using the verbose switch. Note how the source and
18316 object paths are affected by the -I switch.
18319 $ gnatls -v -I.. demo1.o
18321 GNATLS 5.03w (20041123-34)
18322 Copyright 1997-2004 Free Software Foundation, Inc.
18324 Source Search Path:
18325 <Current_Directory>
18327 /home/comar/local/adainclude/
18329 Object Search Path:
18330 <Current_Directory>
18332 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18334 Project Search Path:
18335 <Current_Directory>
18336 /home/comar/local/lib/gnat/
18341 Kind => subprogram body
18342 Flags => No_Elab_Code
18343 Source => demo1.adb modified
18347 The following is an example of use of the dependency list.
18348 Note the use of the -s switch
18349 which gives a straight list of source files. This can be useful for
18350 building specialized scripts.
18353 $ gnatls -d demo2.o
18354 ./demo2.o demo2 OK demo2.adb
18360 $ gnatls -d -s -a demo1.o
18362 /home/comar/local/adainclude/ada.ads
18363 /home/comar/local/adainclude/a-finali.ads
18364 /home/comar/local/adainclude/a-filico.ads
18365 /home/comar/local/adainclude/a-stream.ads
18366 /home/comar/local/adainclude/a-tags.ads
18369 /home/comar/local/adainclude/gnat.ads
18370 /home/comar/local/adainclude/g-io.ads
18372 /home/comar/local/adainclude/system.ads
18373 /home/comar/local/adainclude/s-exctab.ads
18374 /home/comar/local/adainclude/s-finimp.ads
18375 /home/comar/local/adainclude/s-finroo.ads
18376 /home/comar/local/adainclude/s-secsta.ads
18377 /home/comar/local/adainclude/s-stalib.ads
18378 /home/comar/local/adainclude/s-stoele.ads
18379 /home/comar/local/adainclude/s-stratt.ads
18380 /home/comar/local/adainclude/s-tasoli.ads
18381 /home/comar/local/adainclude/s-unstyp.ads
18382 /home/comar/local/adainclude/unchconv.ads
18388 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18390 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18391 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18392 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18393 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18394 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18398 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18399 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18401 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18402 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18403 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18404 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18405 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18406 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18407 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18408 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18409 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18410 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18411 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18415 @node Cleaning Up Using gnatclean
18416 @chapter Cleaning Up Using @code{gnatclean}
18418 @cindex Cleaning tool
18421 @code{gnatclean} is a tool that allows the deletion of files produced by the
18422 compiler, binder and linker, including ALI files, object files, tree files,
18423 expanded source files, library files, interface copy source files, binder
18424 generated files and executable files.
18427 * Running gnatclean::
18428 * Switches for gnatclean::
18429 @c * Examples of gnatclean Usage::
18432 @node Running gnatclean
18433 @section Running @code{gnatclean}
18436 The @code{gnatclean} command has the form:
18439 $ gnatclean switches @var{names}
18443 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18444 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18445 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18448 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18449 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18450 the linker. In informative-only mode, specified by switch
18451 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18452 normal mode is listed, but no file is actually deleted.
18454 @node Switches for gnatclean
18455 @section Switches for @code{gnatclean}
18458 @code{gnatclean} recognizes the following switches:
18462 @cindex @option{--version} @command{gnatclean}
18463 Display Copyright and version, then exit disregarding all other options.
18466 @cindex @option{--help} @command{gnatclean}
18467 If @option{--version} was not used, display usage, then exit disregarding
18470 @item ^-c^/COMPILER_FILES_ONLY^
18471 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18472 Only attempt to delete the files produced by the compiler, not those produced
18473 by the binder or the linker. The files that are not to be deleted are library
18474 files, interface copy files, binder generated files and executable files.
18476 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18477 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18478 Indicate that ALI and object files should normally be found in directory
18481 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18482 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18483 When using project files, if some errors or warnings are detected during
18484 parsing and verbose mode is not in effect (no use of switch
18485 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18486 file, rather than its simple file name.
18489 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18490 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18492 @item ^-n^/NODELETE^
18493 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18494 Informative-only mode. Do not delete any files. Output the list of the files
18495 that would have been deleted if this switch was not specified.
18497 @item ^-P^/PROJECT_FILE=^@var{project}
18498 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18499 Use project file @var{project}. Only one such switch can be used.
18500 When cleaning a project file, the files produced by the compilation of the
18501 immediate sources or inherited sources of the project files are to be
18502 deleted. This is not depending on the presence or not of executable names
18503 on the command line.
18506 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18507 Quiet output. If there are no errors, do not output anything, except in
18508 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18509 (switch ^-n^/NODELETE^).
18511 @item ^-r^/RECURSIVE^
18512 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18513 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18514 clean all imported and extended project files, recursively. If this switch
18515 is not specified, only the files related to the main project file are to be
18516 deleted. This switch has no effect if no project file is specified.
18518 @item ^-v^/VERBOSE^
18519 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18522 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18523 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18524 Indicates the verbosity of the parsing of GNAT project files.
18525 @xref{Switches Related to Project Files}.
18527 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18528 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18529 Indicates that external variable @var{name} has the value @var{value}.
18530 The Project Manager will use this value for occurrences of
18531 @code{external(name)} when parsing the project file.
18532 @xref{Switches Related to Project Files}.
18534 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18535 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18536 When searching for ALI and object files, look in directory
18539 @item ^-I^/SEARCH=^@var{dir}
18540 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18541 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18543 @item ^-I-^/NOCURRENT_DIRECTORY^
18544 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18545 @cindex Source files, suppressing search
18546 Do not look for ALI or object files in the directory
18547 where @code{gnatclean} was invoked.
18551 @c @node Examples of gnatclean Usage
18552 @c @section Examples of @code{gnatclean} Usage
18555 @node GNAT and Libraries
18556 @chapter GNAT and Libraries
18557 @cindex Library, building, installing, using
18560 This chapter describes how to build and use libraries with GNAT, and also shows
18561 how to recompile the GNAT run-time library. You should be familiar with the
18562 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18566 * Introduction to Libraries in GNAT::
18567 * General Ada Libraries::
18568 * Stand-alone Ada Libraries::
18569 * Rebuilding the GNAT Run-Time Library::
18572 @node Introduction to Libraries in GNAT
18573 @section Introduction to Libraries in GNAT
18576 A library is, conceptually, a collection of objects which does not have its
18577 own main thread of execution, but rather provides certain services to the
18578 applications that use it. A library can be either statically linked with the
18579 application, in which case its code is directly included in the application,
18580 or, on platforms that support it, be dynamically linked, in which case
18581 its code is shared by all applications making use of this library.
18583 GNAT supports both types of libraries.
18584 In the static case, the compiled code can be provided in different ways. The
18585 simplest approach is to provide directly the set of objects resulting from
18586 compilation of the library source files. Alternatively, you can group the
18587 objects into an archive using whatever commands are provided by the operating
18588 system. For the latter case, the objects are grouped into a shared library.
18590 In the GNAT environment, a library has three types of components:
18596 @xref{The Ada Library Information Files}.
18598 Object files, an archive or a shared library.
18602 A GNAT library may expose all its source files, which is useful for
18603 documentation purposes. Alternatively, it may expose only the units needed by
18604 an external user to make use of the library. That is to say, the specs
18605 reflecting the library services along with all the units needed to compile
18606 those specs, which can include generic bodies or any body implementing an
18607 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18608 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18610 All compilation units comprising an application, including those in a library,
18611 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18612 computes the elaboration order from the @file{ALI} files and this is why they
18613 constitute a mandatory part of GNAT libraries. Except in the case of
18614 @emph{stand-alone libraries}, where a specific library elaboration routine is
18615 produced independently of the application(s) using the library.
18617 @node General Ada Libraries
18618 @section General Ada Libraries
18621 * Building a library::
18622 * Installing a library::
18623 * Using a library::
18626 @node Building a library
18627 @subsection Building a library
18630 The easiest way to build a library is to use the Project Manager,
18631 which supports a special type of project called a @emph{Library Project}
18632 (@pxref{Library Projects}).
18634 A project is considered a library project, when two project-level attributes
18635 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18636 control different aspects of library configuration, additional optional
18637 project-level attributes can be specified:
18640 This attribute controls whether the library is to be static or dynamic
18642 @item Library_Version
18643 This attribute specifies the library version; this value is used
18644 during dynamic linking of shared libraries to determine if the currently
18645 installed versions of the binaries are compatible.
18647 @item Library_Options
18649 These attributes specify additional low-level options to be used during
18650 library generation, and redefine the actual application used to generate
18655 The GNAT Project Manager takes full care of the library maintenance task,
18656 including recompilation of the source files for which objects do not exist
18657 or are not up to date, assembly of the library archive, and installation of
18658 the library (i.e., copying associated source, object and @file{ALI} files
18659 to the specified location).
18661 Here is a simple library project file:
18662 @smallexample @c ada
18664 for Source_Dirs use ("src1", "src2");
18665 for Object_Dir use "obj";
18666 for Library_Name use "mylib";
18667 for Library_Dir use "lib";
18668 for Library_Kind use "dynamic";
18673 and the compilation command to build and install the library:
18675 @smallexample @c ada
18676 $ gnatmake -Pmy_lib
18680 It is not entirely trivial to perform manually all the steps required to
18681 produce a library. We recommend that you use the GNAT Project Manager
18682 for this task. In special cases where this is not desired, the necessary
18683 steps are discussed below.
18685 There are various possibilities for compiling the units that make up the
18686 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18687 with a conventional script. For simple libraries, it is also possible to create
18688 a dummy main program which depends upon all the packages that comprise the
18689 interface of the library. This dummy main program can then be given to
18690 @command{gnatmake}, which will ensure that all necessary objects are built.
18692 After this task is accomplished, you should follow the standard procedure
18693 of the underlying operating system to produce the static or shared library.
18695 Here is an example of such a dummy program:
18696 @smallexample @c ada
18698 with My_Lib.Service1;
18699 with My_Lib.Service2;
18700 with My_Lib.Service3;
18701 procedure My_Lib_Dummy is
18709 Here are the generic commands that will build an archive or a shared library.
18712 # compiling the library
18713 $ gnatmake -c my_lib_dummy.adb
18715 # we don't need the dummy object itself
18716 $ rm my_lib_dummy.o my_lib_dummy.ali
18718 # create an archive with the remaining objects
18719 $ ar rc libmy_lib.a *.o
18720 # some systems may require "ranlib" to be run as well
18722 # or create a shared library
18723 $ gcc -shared -o libmy_lib.so *.o
18724 # some systems may require the code to have been compiled with -fPIC
18726 # remove the object files that are now in the library
18729 # Make the ALI files read-only so that gnatmake will not try to
18730 # regenerate the objects that are in the library
18735 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
18736 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
18737 be accessed by the directive @option{-l@var{xxx}} at link time.
18739 @node Installing a library
18740 @subsection Installing a library
18741 @cindex @code{ADA_PROJECT_PATH}
18744 If you use project files, library installation is part of the library build
18745 process. Thus no further action is needed in order to make use of the
18746 libraries that are built as part of the general application build. A usable
18747 version of the library is installed in the directory specified by the
18748 @code{Library_Dir} attribute of the library project file.
18750 You may want to install a library in a context different from where the library
18751 is built. This situation arises with third party suppliers, who may want
18752 to distribute a library in binary form where the user is not expected to be
18753 able to recompile the library. The simplest option in this case is to provide
18754 a project file slightly different from the one used to build the library, by
18755 using the @code{externally_built} attribute. For instance, the project
18756 file used to build the library in the previous section can be changed into the
18757 following one when the library is installed:
18759 @smallexample @c projectfile
18761 for Source_Dirs use ("src1", "src2");
18762 for Library_Name use "mylib";
18763 for Library_Dir use "lib";
18764 for Library_Kind use "dynamic";
18765 for Externally_Built use "true";
18770 This project file assumes that the directories @file{src1},
18771 @file{src2}, and @file{lib} exist in
18772 the directory containing the project file. The @code{externally_built}
18773 attribute makes it clear to the GNAT builder that it should not attempt to
18774 recompile any of the units from this library. It allows the library provider to
18775 restrict the source set to the minimum necessary for clients to make use of the
18776 library as described in the first section of this chapter. It is the
18777 responsibility of the library provider to install the necessary sources, ALI
18778 files and libraries in the directories mentioned in the project file. For
18779 convenience, the user's library project file should be installed in a location
18780 that will be searched automatically by the GNAT
18781 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
18782 environment variable (@pxref{Importing Projects}), and also the default GNAT
18783 library location that can be queried with @command{gnatls -v} and is usually of
18784 the form $gnat_install_root/lib/gnat.
18786 When project files are not an option, it is also possible, but not recommended,
18787 to install the library so that the sources needed to use the library are on the
18788 Ada source path and the ALI files & libraries be on the Ada Object path (see
18789 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
18790 administrator can place general-purpose libraries in the default compiler
18791 paths, by specifying the libraries' location in the configuration files
18792 @file{ada_source_path} and @file{ada_object_path}. These configuration files
18793 must be located in the GNAT installation tree at the same place as the gcc spec
18794 file. The location of the gcc spec file can be determined as follows:
18800 The configuration files mentioned above have a simple format: each line
18801 must contain one unique directory name.
18802 Those names are added to the corresponding path
18803 in their order of appearance in the file. The names can be either absolute
18804 or relative; in the latter case, they are relative to where theses files
18807 The files @file{ada_source_path} and @file{ada_object_path} might not be
18809 GNAT installation, in which case, GNAT will look for its run-time library in
18810 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
18811 objects and @file{ALI} files). When the files exist, the compiler does not
18812 look in @file{adainclude} and @file{adalib}, and thus the
18813 @file{ada_source_path} file
18814 must contain the location for the GNAT run-time sources (which can simply
18815 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
18816 contain the location for the GNAT run-time objects (which can simply
18819 You can also specify a new default path to the run-time library at compilation
18820 time with the switch @option{--RTS=rts-path}. You can thus choose / change
18821 the run-time library you want your program to be compiled with. This switch is
18822 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
18823 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
18825 It is possible to install a library before or after the standard GNAT
18826 library, by reordering the lines in the configuration files. In general, a
18827 library must be installed before the GNAT library if it redefines
18830 @node Using a library
18831 @subsection Using a library
18833 @noindent Once again, the project facility greatly simplifies the use of
18834 libraries. In this context, using a library is just a matter of adding a
18835 @code{with} clause in the user project. For instance, to make use of the
18836 library @code{My_Lib} shown in examples in earlier sections, you can
18839 @smallexample @c projectfile
18846 Even if you have a third-party, non-Ada library, you can still use GNAT's
18847 Project Manager facility to provide a wrapper for it. For example, the
18848 following project, when @code{with}ed by your main project, will link with the
18849 third-party library @file{liba.a}:
18851 @smallexample @c projectfile
18854 for Externally_Built use "true";
18855 for Source_Files use ();
18856 for Library_Dir use "lib";
18857 for Library_Name use "a";
18858 for Library_Kind use "static";
18862 This is an alternative to the use of @code{pragma Linker_Options}. It is
18863 especially interesting in the context of systems with several interdependent
18864 static libraries where finding a proper linker order is not easy and best be
18865 left to the tools having visibility over project dependence information.
18868 In order to use an Ada library manually, you need to make sure that this
18869 library is on both your source and object path
18870 (see @ref{Search Paths and the Run-Time Library (RTL)}
18871 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
18872 in an archive or a shared library, you need to specify the desired
18873 library at link time.
18875 For example, you can use the library @file{mylib} installed in
18876 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
18879 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
18884 This can be expressed more simply:
18889 when the following conditions are met:
18892 @file{/dir/my_lib_src} has been added by the user to the environment
18893 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
18894 @file{ada_source_path}
18896 @file{/dir/my_lib_obj} has been added by the user to the environment
18897 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
18898 @file{ada_object_path}
18900 a pragma @code{Linker_Options} has been added to one of the sources.
18903 @smallexample @c ada
18904 pragma Linker_Options ("-lmy_lib");
18908 @node Stand-alone Ada Libraries
18909 @section Stand-alone Ada Libraries
18910 @cindex Stand-alone library, building, using
18913 * Introduction to Stand-alone Libraries::
18914 * Building a Stand-alone Library::
18915 * Creating a Stand-alone Library to be used in a non-Ada context::
18916 * Restrictions in Stand-alone Libraries::
18919 @node Introduction to Stand-alone Libraries
18920 @subsection Introduction to Stand-alone Libraries
18923 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
18925 elaborate the Ada units that are included in the library. In contrast with
18926 an ordinary library, which consists of all sources, objects and @file{ALI}
18928 library, a SAL may specify a restricted subset of compilation units
18929 to serve as a library interface. In this case, the fully
18930 self-sufficient set of files will normally consist of an objects
18931 archive, the sources of interface units' specs, and the @file{ALI}
18932 files of interface units.
18933 If an interface spec contains a generic unit or an inlined subprogram,
18935 source must also be provided; if the units that must be provided in the source
18936 form depend on other units, the source and @file{ALI} files of those must
18939 The main purpose of a SAL is to minimize the recompilation overhead of client
18940 applications when a new version of the library is installed. Specifically,
18941 if the interface sources have not changed, client applications do not need to
18942 be recompiled. If, furthermore, a SAL is provided in the shared form and its
18943 version, controlled by @code{Library_Version} attribute, is not changed,
18944 then the clients do not need to be relinked.
18946 SALs also allow the library providers to minimize the amount of library source
18947 text exposed to the clients. Such ``information hiding'' might be useful or
18948 necessary for various reasons.
18950 Stand-alone libraries are also well suited to be used in an executable whose
18951 main routine is not written in Ada.
18953 @node Building a Stand-alone Library
18954 @subsection Building a Stand-alone Library
18957 GNAT's Project facility provides a simple way of building and installing
18958 stand-alone libraries; see @ref{Stand-alone Library Projects}.
18959 To be a Stand-alone Library Project, in addition to the two attributes
18960 that make a project a Library Project (@code{Library_Name} and
18961 @code{Library_Dir}; see @ref{Library Projects}), the attribute
18962 @code{Library_Interface} must be defined. For example:
18964 @smallexample @c projectfile
18966 for Library_Dir use "lib_dir";
18967 for Library_Name use "dummy";
18968 for Library_Interface use ("int1", "int1.child");
18973 Attribute @code{Library_Interface} has a non-empty string list value,
18974 each string in the list designating a unit contained in an immediate source
18975 of the project file.
18977 When a Stand-alone Library is built, first the binder is invoked to build
18978 a package whose name depends on the library name
18979 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
18980 This binder-generated package includes initialization and
18981 finalization procedures whose
18982 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
18984 above). The object corresponding to this package is included in the library.
18986 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
18987 calling of these procedures if a static SAL is built, or if a shared SAL
18989 with the project-level attribute @code{Library_Auto_Init} set to
18992 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
18993 (those that are listed in attribute @code{Library_Interface}) are copied to
18994 the Library Directory. As a consequence, only the Interface Units may be
18995 imported from Ada units outside of the library. If other units are imported,
18996 the binding phase will fail.
18998 The attribute @code{Library_Src_Dir} may be specified for a
18999 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19000 single string value. Its value must be the path (absolute or relative to the
19001 project directory) of an existing directory. This directory cannot be the
19002 object directory or one of the source directories, but it can be the same as
19003 the library directory. The sources of the Interface
19004 Units of the library that are needed by an Ada client of the library will be
19005 copied to the designated directory, called the Interface Copy directory.
19006 These sources include the specs of the Interface Units, but they may also
19007 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19008 are used, or when there is a generic unit in the spec. Before the sources
19009 are copied to the Interface Copy directory, an attempt is made to delete all
19010 files in the Interface Copy directory.
19012 Building stand-alone libraries by hand is somewhat tedious, but for those
19013 occasions when it is necessary here are the steps that you need to perform:
19016 Compile all library sources.
19019 Invoke the binder with the switch @option{-n} (No Ada main program),
19020 with all the @file{ALI} files of the interfaces, and
19021 with the switch @option{-L} to give specific names to the @code{init}
19022 and @code{final} procedures. For example:
19024 gnatbind -n int1.ali int2.ali -Lsal1
19028 Compile the binder generated file:
19034 Link the dynamic library with all the necessary object files,
19035 indicating to the linker the names of the @code{init} (and possibly
19036 @code{final}) procedures for automatic initialization (and finalization).
19037 The built library should be placed in a directory different from
19038 the object directory.
19041 Copy the @code{ALI} files of the interface to the library directory,
19042 add in this copy an indication that it is an interface to a SAL
19043 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19044 with letter ``P'') and make the modified copy of the @file{ALI} file
19049 Using SALs is not different from using other libraries
19050 (see @ref{Using a library}).
19052 @node Creating a Stand-alone Library to be used in a non-Ada context
19053 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19056 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19059 The only extra step required is to ensure that library interface subprograms
19060 are compatible with the main program, by means of @code{pragma Export}
19061 or @code{pragma Convention}.
19063 Here is an example of simple library interface for use with C main program:
19065 @smallexample @c ada
19066 package Interface is
19068 procedure Do_Something;
19069 pragma Export (C, Do_Something, "do_something");
19071 procedure Do_Something_Else;
19072 pragma Export (C, Do_Something_Else, "do_something_else");
19078 On the foreign language side, you must provide a ``foreign'' view of the
19079 library interface; remember that it should contain elaboration routines in
19080 addition to interface subprograms.
19082 The example below shows the content of @code{mylib_interface.h} (note
19083 that there is no rule for the naming of this file, any name can be used)
19085 /* the library elaboration procedure */
19086 extern void mylibinit (void);
19088 /* the library finalization procedure */
19089 extern void mylibfinal (void);
19091 /* the interface exported by the library */
19092 extern void do_something (void);
19093 extern void do_something_else (void);
19097 Libraries built as explained above can be used from any program, provided
19098 that the elaboration procedures (named @code{mylibinit} in the previous
19099 example) are called before the library services are used. Any number of
19100 libraries can be used simultaneously, as long as the elaboration
19101 procedure of each library is called.
19103 Below is an example of a C program that uses the @code{mylib} library.
19106 #include "mylib_interface.h"
19111 /* First, elaborate the library before using it */
19114 /* Main program, using the library exported entities */
19116 do_something_else ();
19118 /* Library finalization at the end of the program */
19125 Note that invoking any library finalization procedure generated by
19126 @code{gnatbind} shuts down the Ada run-time environment.
19128 finalization of all Ada libraries must be performed at the end of the program.
19129 No call to these libraries or to the Ada run-time library should be made
19130 after the finalization phase.
19132 @node Restrictions in Stand-alone Libraries
19133 @subsection Restrictions in Stand-alone Libraries
19136 The pragmas listed below should be used with caution inside libraries,
19137 as they can create incompatibilities with other Ada libraries:
19139 @item pragma @code{Locking_Policy}
19140 @item pragma @code{Queuing_Policy}
19141 @item pragma @code{Task_Dispatching_Policy}
19142 @item pragma @code{Unreserve_All_Interrupts}
19146 When using a library that contains such pragmas, the user must make sure
19147 that all libraries use the same pragmas with the same values. Otherwise,
19148 @code{Program_Error} will
19149 be raised during the elaboration of the conflicting
19150 libraries. The usage of these pragmas and its consequences for the user
19151 should therefore be well documented.
19153 Similarly, the traceback in the exception occurrence mechanism should be
19154 enabled or disabled in a consistent manner across all libraries.
19155 Otherwise, Program_Error will be raised during the elaboration of the
19156 conflicting libraries.
19158 If the @code{Version} or @code{Body_Version}
19159 attributes are used inside a library, then you need to
19160 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19161 libraries, so that version identifiers can be properly computed.
19162 In practice these attributes are rarely used, so this is unlikely
19163 to be a consideration.
19165 @node Rebuilding the GNAT Run-Time Library
19166 @section Rebuilding the GNAT Run-Time Library
19167 @cindex GNAT Run-Time Library, rebuilding
19168 @cindex Building the GNAT Run-Time Library
19169 @cindex Rebuilding the GNAT Run-Time Library
19170 @cindex Run-Time Library, rebuilding
19173 It may be useful to recompile the GNAT library in various contexts, the
19174 most important one being the use of partition-wide configuration pragmas
19175 such as @code{Normalize_Scalars}. A special Makefile called
19176 @code{Makefile.adalib} is provided to that effect and can be found in
19177 the directory containing the GNAT library. The location of this
19178 directory depends on the way the GNAT environment has been installed and can
19179 be determined by means of the command:
19186 The last entry in the object search path usually contains the
19187 gnat library. This Makefile contains its own documentation and in
19188 particular the set of instructions needed to rebuild a new library and
19191 @node Using the GNU make Utility
19192 @chapter Using the GNU @code{make} Utility
19196 This chapter offers some examples of makefiles that solve specific
19197 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19198 make, make, GNU @code{make}}), nor does it try to replace the
19199 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19201 All the examples in this section are specific to the GNU version of
19202 make. Although @command{make} is a standard utility, and the basic language
19203 is the same, these examples use some advanced features found only in
19207 * Using gnatmake in a Makefile::
19208 * Automatically Creating a List of Directories::
19209 * Generating the Command Line Switches::
19210 * Overcoming Command Line Length Limits::
19213 @node Using gnatmake in a Makefile
19214 @section Using gnatmake in a Makefile
19219 Complex project organizations can be handled in a very powerful way by
19220 using GNU make combined with gnatmake. For instance, here is a Makefile
19221 which allows you to build each subsystem of a big project into a separate
19222 shared library. Such a makefile allows you to significantly reduce the link
19223 time of very big applications while maintaining full coherence at
19224 each step of the build process.
19226 The list of dependencies are handled automatically by
19227 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19228 the appropriate directories.
19230 Note that you should also read the example on how to automatically
19231 create the list of directories
19232 (@pxref{Automatically Creating a List of Directories})
19233 which might help you in case your project has a lot of subdirectories.
19238 @font@heightrm=cmr8
19241 ## This Makefile is intended to be used with the following directory
19243 ## - The sources are split into a series of csc (computer software components)
19244 ## Each of these csc is put in its own directory.
19245 ## Their name are referenced by the directory names.
19246 ## They will be compiled into shared library (although this would also work
19247 ## with static libraries
19248 ## - The main program (and possibly other packages that do not belong to any
19249 ## csc is put in the top level directory (where the Makefile is).
19250 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19251 ## \_ second_csc (sources) __ lib (will contain the library)
19253 ## Although this Makefile is build for shared library, it is easy to modify
19254 ## to build partial link objects instead (modify the lines with -shared and
19257 ## With this makefile, you can change any file in the system or add any new
19258 ## file, and everything will be recompiled correctly (only the relevant shared
19259 ## objects will be recompiled, and the main program will be re-linked).
19261 # The list of computer software component for your project. This might be
19262 # generated automatically.
19265 # Name of the main program (no extension)
19268 # If we need to build objects with -fPIC, uncomment the following line
19271 # The following variable should give the directory containing libgnat.so
19272 # You can get this directory through 'gnatls -v'. This is usually the last
19273 # directory in the Object_Path.
19276 # The directories for the libraries
19277 # (This macro expands the list of CSC to the list of shared libraries, you
19278 # could simply use the expanded form:
19279 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19280 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19282 $@{MAIN@}: objects $@{LIB_DIR@}
19283 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19284 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19287 # recompile the sources
19288 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19290 # Note: In a future version of GNAT, the following commands will be simplified
19291 # by a new tool, gnatmlib
19293 mkdir -p $@{dir $@@ @}
19294 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19295 cd $@{dir $@@ @} && cp -f ../*.ali .
19297 # The dependencies for the modules
19298 # Note that we have to force the expansion of *.o, since in some cases
19299 # make won't be able to do it itself.
19300 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19301 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19302 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19304 # Make sure all of the shared libraries are in the path before starting the
19307 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19310 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19311 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19312 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19313 $@{RM@} *.o *.ali $@{MAIN@}
19316 @node Automatically Creating a List of Directories
19317 @section Automatically Creating a List of Directories
19320 In most makefiles, you will have to specify a list of directories, and
19321 store it in a variable. For small projects, it is often easier to
19322 specify each of them by hand, since you then have full control over what
19323 is the proper order for these directories, which ones should be
19326 However, in larger projects, which might involve hundreds of
19327 subdirectories, it might be more convenient to generate this list
19330 The example below presents two methods. The first one, although less
19331 general, gives you more control over the list. It involves wildcard
19332 characters, that are automatically expanded by @command{make}. Its
19333 shortcoming is that you need to explicitly specify some of the
19334 organization of your project, such as for instance the directory tree
19335 depth, whether some directories are found in a separate tree, @enddots{}
19337 The second method is the most general one. It requires an external
19338 program, called @command{find}, which is standard on all Unix systems. All
19339 the directories found under a given root directory will be added to the
19345 @font@heightrm=cmr8
19348 # The examples below are based on the following directory hierarchy:
19349 # All the directories can contain any number of files
19350 # ROOT_DIRECTORY -> a -> aa -> aaa
19353 # -> b -> ba -> baa
19356 # This Makefile creates a variable called DIRS, that can be reused any time
19357 # you need this list (see the other examples in this section)
19359 # The root of your project's directory hierarchy
19363 # First method: specify explicitly the list of directories
19364 # This allows you to specify any subset of all the directories you need.
19367 DIRS := a/aa/ a/ab/ b/ba/
19370 # Second method: use wildcards
19371 # Note that the argument(s) to wildcard below should end with a '/'.
19372 # Since wildcards also return file names, we have to filter them out
19373 # to avoid duplicate directory names.
19374 # We thus use make's @code{dir} and @code{sort} functions.
19375 # It sets DIRs to the following value (note that the directories aaa and baa
19376 # are not given, unless you change the arguments to wildcard).
19377 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19380 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19381 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19384 # Third method: use an external program
19385 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19386 # This is the most complete command: it sets DIRs to the following value:
19387 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19390 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19394 @node Generating the Command Line Switches
19395 @section Generating the Command Line Switches
19398 Once you have created the list of directories as explained in the
19399 previous section (@pxref{Automatically Creating a List of Directories}),
19400 you can easily generate the command line arguments to pass to gnatmake.
19402 For the sake of completeness, this example assumes that the source path
19403 is not the same as the object path, and that you have two separate lists
19407 # see "Automatically creating a list of directories" to create
19412 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19413 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19416 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19419 @node Overcoming Command Line Length Limits
19420 @section Overcoming Command Line Length Limits
19423 One problem that might be encountered on big projects is that many
19424 operating systems limit the length of the command line. It is thus hard to give
19425 gnatmake the list of source and object directories.
19427 This example shows how you can set up environment variables, which will
19428 make @command{gnatmake} behave exactly as if the directories had been
19429 specified on the command line, but have a much higher length limit (or
19430 even none on most systems).
19432 It assumes that you have created a list of directories in your Makefile,
19433 using one of the methods presented in
19434 @ref{Automatically Creating a List of Directories}.
19435 For the sake of completeness, we assume that the object
19436 path (where the ALI files are found) is different from the sources patch.
19438 Note a small trick in the Makefile below: for efficiency reasons, we
19439 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19440 expanded immediately by @code{make}. This way we overcome the standard
19441 make behavior which is to expand the variables only when they are
19444 On Windows, if you are using the standard Windows command shell, you must
19445 replace colons with semicolons in the assignments to these variables.
19450 @font@heightrm=cmr8
19453 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19454 # This is the same thing as putting the -I arguments on the command line.
19455 # (the equivalent of using -aI on the command line would be to define
19456 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19457 # You can of course have different values for these variables.
19459 # Note also that we need to keep the previous values of these variables, since
19460 # they might have been set before running 'make' to specify where the GNAT
19461 # library is installed.
19463 # see "Automatically creating a list of directories" to create these
19469 space:=$@{empty@} $@{empty@}
19470 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19471 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19472 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19473 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19474 export ADA_INCLUDE_PATH
19475 export ADA_OBJECT_PATH
19482 @node Memory Management Issues
19483 @chapter Memory Management Issues
19486 This chapter describes some useful memory pools provided in the GNAT library
19487 and in particular the GNAT Debug Pool facility, which can be used to detect
19488 incorrect uses of access values (including ``dangling references'').
19490 It also describes the @command{gnatmem} tool, which can be used to track down
19495 * Some Useful Memory Pools::
19496 * The GNAT Debug Pool Facility::
19498 * The gnatmem Tool::
19502 @node Some Useful Memory Pools
19503 @section Some Useful Memory Pools
19504 @findex Memory Pool
19505 @cindex storage, pool
19508 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19509 storage pool. Allocations use the standard system call @code{malloc} while
19510 deallocations use the standard system call @code{free}. No reclamation is
19511 performed when the pool goes out of scope. For performance reasons, the
19512 standard default Ada allocators/deallocators do not use any explicit storage
19513 pools but if they did, they could use this storage pool without any change in
19514 behavior. That is why this storage pool is used when the user
19515 manages to make the default implicit allocator explicit as in this example:
19516 @smallexample @c ada
19517 type T1 is access Something;
19518 -- no Storage pool is defined for T2
19519 type T2 is access Something_Else;
19520 for T2'Storage_Pool use T1'Storage_Pool;
19521 -- the above is equivalent to
19522 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19526 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19527 pool. The allocation strategy is similar to @code{Pool_Local}'s
19528 except that the all
19529 storage allocated with this pool is reclaimed when the pool object goes out of
19530 scope. This pool provides a explicit mechanism similar to the implicit one
19531 provided by several Ada 83 compilers for allocations performed through a local
19532 access type and whose purpose was to reclaim memory when exiting the
19533 scope of a given local access. As an example, the following program does not
19534 leak memory even though it does not perform explicit deallocation:
19536 @smallexample @c ada
19537 with System.Pool_Local;
19538 procedure Pooloc1 is
19539 procedure Internal is
19540 type A is access Integer;
19541 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19542 for A'Storage_Pool use X;
19545 for I in 1 .. 50 loop
19550 for I in 1 .. 100 loop
19557 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19558 @code{Storage_Size} is specified for an access type.
19559 The whole storage for the pool is
19560 allocated at once, usually on the stack at the point where the access type is
19561 elaborated. It is automatically reclaimed when exiting the scope where the
19562 access type is defined. This package is not intended to be used directly by the
19563 user and it is implicitly used for each such declaration:
19565 @smallexample @c ada
19566 type T1 is access Something;
19567 for T1'Storage_Size use 10_000;
19570 @node The GNAT Debug Pool Facility
19571 @section The GNAT Debug Pool Facility
19573 @cindex storage, pool, memory corruption
19576 The use of unchecked deallocation and unchecked conversion can easily
19577 lead to incorrect memory references. The problems generated by such
19578 references are usually difficult to tackle because the symptoms can be
19579 very remote from the origin of the problem. In such cases, it is
19580 very helpful to detect the problem as early as possible. This is the
19581 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19583 In order to use the GNAT specific debugging pool, the user must
19584 associate a debug pool object with each of the access types that may be
19585 related to suspected memory problems. See Ada Reference Manual 13.11.
19586 @smallexample @c ada
19587 type Ptr is access Some_Type;
19588 Pool : GNAT.Debug_Pools.Debug_Pool;
19589 for Ptr'Storage_Pool use Pool;
19593 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19594 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19595 allow the user to redefine allocation and deallocation strategies. They
19596 also provide a checkpoint for each dereference, through the use of
19597 the primitive operation @code{Dereference} which is implicitly called at
19598 each dereference of an access value.
19600 Once an access type has been associated with a debug pool, operations on
19601 values of the type may raise four distinct exceptions,
19602 which correspond to four potential kinds of memory corruption:
19605 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19607 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19609 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19611 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19615 For types associated with a Debug_Pool, dynamic allocation is performed using
19616 the standard GNAT allocation routine. References to all allocated chunks of
19617 memory are kept in an internal dictionary. Several deallocation strategies are
19618 provided, whereupon the user can choose to release the memory to the system,
19619 keep it allocated for further invalid access checks, or fill it with an easily
19620 recognizable pattern for debug sessions. The memory pattern is the old IBM
19621 hexadecimal convention: @code{16#DEADBEEF#}.
19623 See the documentation in the file g-debpoo.ads for more information on the
19624 various strategies.
19626 Upon each dereference, a check is made that the access value denotes a
19627 properly allocated memory location. Here is a complete example of use of
19628 @code{Debug_Pools}, that includes typical instances of memory corruption:
19629 @smallexample @c ada
19633 with Gnat.Io; use Gnat.Io;
19634 with Unchecked_Deallocation;
19635 with Unchecked_Conversion;
19636 with GNAT.Debug_Pools;
19637 with System.Storage_Elements;
19638 with Ada.Exceptions; use Ada.Exceptions;
19639 procedure Debug_Pool_Test is
19641 type T is access Integer;
19642 type U is access all T;
19644 P : GNAT.Debug_Pools.Debug_Pool;
19645 for T'Storage_Pool use P;
19647 procedure Free is new Unchecked_Deallocation (Integer, T);
19648 function UC is new Unchecked_Conversion (U, T);
19651 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19661 Put_Line (Integer'Image(B.all));
19663 when E : others => Put_Line ("raised: " & Exception_Name (E));
19668 when E : others => Put_Line ("raised: " & Exception_Name (E));
19672 Put_Line (Integer'Image(B.all));
19674 when E : others => Put_Line ("raised: " & Exception_Name (E));
19679 when E : others => Put_Line ("raised: " & Exception_Name (E));
19682 end Debug_Pool_Test;
19686 The debug pool mechanism provides the following precise diagnostics on the
19687 execution of this erroneous program:
19690 Total allocated bytes : 0
19691 Total deallocated bytes : 0
19692 Current Water Mark: 0
19696 Total allocated bytes : 8
19697 Total deallocated bytes : 0
19698 Current Water Mark: 8
19701 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
19702 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
19703 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
19704 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
19706 Total allocated bytes : 8
19707 Total deallocated bytes : 4
19708 Current Water Mark: 4
19713 @node The gnatmem Tool
19714 @section The @command{gnatmem} Tool
19718 The @code{gnatmem} utility monitors dynamic allocation and
19719 deallocation activity in a program, and displays information about
19720 incorrect deallocations and possible sources of memory leaks.
19721 It is designed to work in association with a static runtime library
19722 only and in this context provides three types of information:
19725 General information concerning memory management, such as the total
19726 number of allocations and deallocations, the amount of allocated
19727 memory and the high water mark, i.e.@: the largest amount of allocated
19728 memory in the course of program execution.
19731 Backtraces for all incorrect deallocations, that is to say deallocations
19732 which do not correspond to a valid allocation.
19735 Information on each allocation that is potentially the origin of a memory
19740 * Running gnatmem::
19741 * Switches for gnatmem::
19742 * Example of gnatmem Usage::
19745 @node Running gnatmem
19746 @subsection Running @code{gnatmem}
19749 @code{gnatmem} makes use of the output created by the special version of
19750 allocation and deallocation routines that record call information. This
19751 allows to obtain accurate dynamic memory usage history at a minimal cost to
19752 the execution speed. Note however, that @code{gnatmem} is not supported on
19753 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
19754 Solaris and Windows NT/2000/XP (x86).
19757 The @code{gnatmem} command has the form
19760 $ gnatmem @ovar{switches} user_program
19764 The program must have been linked with the instrumented version of the
19765 allocation and deallocation routines. This is done by linking with the
19766 @file{libgmem.a} library. For correct symbolic backtrace information,
19767 the user program should be compiled with debugging options
19768 (see @ref{Switches for gcc}). For example to build @file{my_program}:
19771 $ gnatmake -g my_program -largs -lgmem
19775 As library @file{libgmem.a} contains an alternate body for package
19776 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
19777 when an executable is linked with library @file{libgmem.a}. It is then not
19778 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
19781 When @file{my_program} is executed, the file @file{gmem.out} is produced.
19782 This file contains information about all allocations and deallocations
19783 performed by the program. It is produced by the instrumented allocations and
19784 deallocations routines and will be used by @code{gnatmem}.
19786 In order to produce symbolic backtrace information for allocations and
19787 deallocations performed by the GNAT run-time library, you need to use a
19788 version of that library that has been compiled with the @option{-g} switch
19789 (see @ref{Rebuilding the GNAT Run-Time Library}).
19791 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
19792 examine. If the location of @file{gmem.out} file was not explicitly supplied by
19793 @option{-i} switch, gnatmem will assume that this file can be found in the
19794 current directory. For example, after you have executed @file{my_program},
19795 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
19798 $ gnatmem my_program
19802 This will produce the output with the following format:
19804 *************** debut cc
19806 $ gnatmem my_program
19810 Total number of allocations : 45
19811 Total number of deallocations : 6
19812 Final Water Mark (non freed mem) : 11.29 Kilobytes
19813 High Water Mark : 11.40 Kilobytes
19818 Allocation Root # 2
19819 -------------------
19820 Number of non freed allocations : 11
19821 Final Water Mark (non freed mem) : 1.16 Kilobytes
19822 High Water Mark : 1.27 Kilobytes
19824 my_program.adb:23 my_program.alloc
19830 The first block of output gives general information. In this case, the
19831 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
19832 Unchecked_Deallocation routine occurred.
19835 Subsequent paragraphs display information on all allocation roots.
19836 An allocation root is a specific point in the execution of the program
19837 that generates some dynamic allocation, such as a ``@code{@b{new}}''
19838 construct. This root is represented by an execution backtrace (or subprogram
19839 call stack). By default the backtrace depth for allocations roots is 1, so
19840 that a root corresponds exactly to a source location. The backtrace can
19841 be made deeper, to make the root more specific.
19843 @node Switches for gnatmem
19844 @subsection Switches for @code{gnatmem}
19847 @code{gnatmem} recognizes the following switches:
19852 @cindex @option{-q} (@code{gnatmem})
19853 Quiet. Gives the minimum output needed to identify the origin of the
19854 memory leaks. Omits statistical information.
19857 @cindex @var{N} (@code{gnatmem})
19858 N is an integer literal (usually between 1 and 10) which controls the
19859 depth of the backtraces defining allocation root. The default value for
19860 N is 1. The deeper the backtrace, the more precise the localization of
19861 the root. Note that the total number of roots can depend on this
19862 parameter. This parameter must be specified @emph{before} the name of the
19863 executable to be analyzed, to avoid ambiguity.
19866 @cindex @option{-b} (@code{gnatmem})
19867 This switch has the same effect as just depth parameter.
19869 @item -i @var{file}
19870 @cindex @option{-i} (@code{gnatmem})
19871 Do the @code{gnatmem} processing starting from @file{file}, rather than
19872 @file{gmem.out} in the current directory.
19875 @cindex @option{-m} (@code{gnatmem})
19876 This switch causes @code{gnatmem} to mask the allocation roots that have less
19877 than n leaks. The default value is 1. Specifying the value of 0 will allow to
19878 examine even the roots that didn't result in leaks.
19881 @cindex @option{-s} (@code{gnatmem})
19882 This switch causes @code{gnatmem} to sort the allocation roots according to the
19883 specified order of sort criteria, each identified by a single letter. The
19884 currently supported criteria are @code{n, h, w} standing respectively for
19885 number of unfreed allocations, high watermark, and final watermark
19886 corresponding to a specific root. The default order is @code{nwh}.
19890 @node Example of gnatmem Usage
19891 @subsection Example of @code{gnatmem} Usage
19894 The following example shows the use of @code{gnatmem}
19895 on a simple memory-leaking program.
19896 Suppose that we have the following Ada program:
19898 @smallexample @c ada
19901 with Unchecked_Deallocation;
19902 procedure Test_Gm is
19904 type T is array (1..1000) of Integer;
19905 type Ptr is access T;
19906 procedure Free is new Unchecked_Deallocation (T, Ptr);
19909 procedure My_Alloc is
19914 procedure My_DeAlloc is
19922 for I in 1 .. 5 loop
19923 for J in I .. 5 loop
19934 The program needs to be compiled with debugging option and linked with
19935 @code{gmem} library:
19938 $ gnatmake -g test_gm -largs -lgmem
19942 Then we execute the program as usual:
19949 Then @code{gnatmem} is invoked simply with
19955 which produces the following output (result may vary on different platforms):
19960 Total number of allocations : 18
19961 Total number of deallocations : 5
19962 Final Water Mark (non freed mem) : 53.00 Kilobytes
19963 High Water Mark : 56.90 Kilobytes
19965 Allocation Root # 1
19966 -------------------
19967 Number of non freed allocations : 11
19968 Final Water Mark (non freed mem) : 42.97 Kilobytes
19969 High Water Mark : 46.88 Kilobytes
19971 test_gm.adb:11 test_gm.my_alloc
19973 Allocation Root # 2
19974 -------------------
19975 Number of non freed allocations : 1
19976 Final Water Mark (non freed mem) : 10.02 Kilobytes
19977 High Water Mark : 10.02 Kilobytes
19979 s-secsta.adb:81 system.secondary_stack.ss_init
19981 Allocation Root # 3
19982 -------------------
19983 Number of non freed allocations : 1
19984 Final Water Mark (non freed mem) : 12 Bytes
19985 High Water Mark : 12 Bytes
19987 s-secsta.adb:181 system.secondary_stack.ss_init
19991 Note that the GNAT run time contains itself a certain number of
19992 allocations that have no corresponding deallocation,
19993 as shown here for root #2 and root
19994 #3. This is a normal behavior when the number of non-freed allocations
19995 is one, it allocates dynamic data structures that the run time needs for
19996 the complete lifetime of the program. Note also that there is only one
19997 allocation root in the user program with a single line back trace:
19998 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
19999 program shows that 'My_Alloc' is called at 2 different points in the
20000 source (line 21 and line 24). If those two allocation roots need to be
20001 distinguished, the backtrace depth parameter can be used:
20004 $ gnatmem 3 test_gm
20008 which will give the following output:
20013 Total number of allocations : 18
20014 Total number of deallocations : 5
20015 Final Water Mark (non freed mem) : 53.00 Kilobytes
20016 High Water Mark : 56.90 Kilobytes
20018 Allocation Root # 1
20019 -------------------
20020 Number of non freed allocations : 10
20021 Final Water Mark (non freed mem) : 39.06 Kilobytes
20022 High Water Mark : 42.97 Kilobytes
20024 test_gm.adb:11 test_gm.my_alloc
20025 test_gm.adb:24 test_gm
20026 b_test_gm.c:52 main
20028 Allocation Root # 2
20029 -------------------
20030 Number of non freed allocations : 1
20031 Final Water Mark (non freed mem) : 10.02 Kilobytes
20032 High Water Mark : 10.02 Kilobytes
20034 s-secsta.adb:81 system.secondary_stack.ss_init
20035 s-secsta.adb:283 <system__secondary_stack___elabb>
20036 b_test_gm.c:33 adainit
20038 Allocation Root # 3
20039 -------------------
20040 Number of non freed allocations : 1
20041 Final Water Mark (non freed mem) : 3.91 Kilobytes
20042 High Water Mark : 3.91 Kilobytes
20044 test_gm.adb:11 test_gm.my_alloc
20045 test_gm.adb:21 test_gm
20046 b_test_gm.c:52 main
20048 Allocation Root # 4
20049 -------------------
20050 Number of non freed allocations : 1
20051 Final Water Mark (non freed mem) : 12 Bytes
20052 High Water Mark : 12 Bytes
20054 s-secsta.adb:181 system.secondary_stack.ss_init
20055 s-secsta.adb:283 <system__secondary_stack___elabb>
20056 b_test_gm.c:33 adainit
20060 The allocation root #1 of the first example has been split in 2 roots #1
20061 and #3 thanks to the more precise associated backtrace.
20065 @node Stack Related Facilities
20066 @chapter Stack Related Facilities
20069 This chapter describes some useful tools associated with stack
20070 checking and analysis. In
20071 particular, it deals with dynamic and static stack usage measurements.
20074 * Stack Overflow Checking::
20075 * Static Stack Usage Analysis::
20076 * Dynamic Stack Usage Analysis::
20079 @node Stack Overflow Checking
20080 @section Stack Overflow Checking
20081 @cindex Stack Overflow Checking
20082 @cindex -fstack-check
20085 For most operating systems, @command{gcc} does not perform stack overflow
20086 checking by default. This means that if the main environment task or
20087 some other task exceeds the available stack space, then unpredictable
20088 behavior will occur. Most native systems offer some level of protection by
20089 adding a guard page at the end of each task stack. This mechanism is usually
20090 not enough for dealing properly with stack overflow situations because
20091 a large local variable could ``jump'' above the guard page.
20092 Furthermore, when the
20093 guard page is hit, there may not be any space left on the stack for executing
20094 the exception propagation code. Enabling stack checking avoids
20097 To activate stack checking, compile all units with the gcc option
20098 @option{-fstack-check}. For example:
20101 gcc -c -fstack-check package1.adb
20105 Units compiled with this option will generate extra instructions to check
20106 that any use of the stack (for procedure calls or for declaring local
20107 variables in declare blocks) does not exceed the available stack space.
20108 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20110 For declared tasks, the stack size is controlled by the size
20111 given in an applicable @code{Storage_Size} pragma or by the value specified
20112 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20113 the default size as defined in the GNAT runtime otherwise.
20115 For the environment task, the stack size depends on
20116 system defaults and is unknown to the compiler. Stack checking
20117 may still work correctly if a fixed
20118 size stack is allocated, but this cannot be guaranteed.
20120 To ensure that a clean exception is signalled for stack
20121 overflow, set the environment variable
20122 @env{GNAT_STACK_LIMIT} to indicate the maximum
20123 stack area that can be used, as in:
20124 @cindex GNAT_STACK_LIMIT
20127 SET GNAT_STACK_LIMIT 1600
20131 The limit is given in kilobytes, so the above declaration would
20132 set the stack limit of the environment task to 1.6 megabytes.
20133 Note that the only purpose of this usage is to limit the amount
20134 of stack used by the environment task. If it is necessary to
20135 increase the amount of stack for the environment task, then this
20136 is an operating systems issue, and must be addressed with the
20137 appropriate operating systems commands.
20140 To have a fixed size stack in the environment task, the stack must be put
20141 in the P0 address space and its size specified. Use these switches to
20145 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20149 The quotes are required to keep case. The number after @samp{STACK=} is the
20150 size of the environmental task stack in pagelets (512 bytes). In this example
20151 the stack size is about 2 megabytes.
20154 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20155 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20156 more details about the @option{/p0image} qualifier and the @option{stack}
20160 @node Static Stack Usage Analysis
20161 @section Static Stack Usage Analysis
20162 @cindex Static Stack Usage Analysis
20163 @cindex -fstack-usage
20166 A unit compiled with @option{-fstack-usage} will generate an extra file
20168 the maximum amount of stack used, on a per-function basis.
20169 The file has the same
20170 basename as the target object file with a @file{.su} extension.
20171 Each line of this file is made up of three fields:
20175 The name of the function.
20179 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20182 The second field corresponds to the size of the known part of the function
20185 The qualifier @code{static} means that the function frame size
20187 It usually means that all local variables have a static size.
20188 In this case, the second field is a reliable measure of the function stack
20191 The qualifier @code{dynamic} means that the function frame size is not static.
20192 It happens mainly when some local variables have a dynamic size. When this
20193 qualifier appears alone, the second field is not a reliable measure
20194 of the function stack analysis. When it is qualified with @code{bounded}, it
20195 means that the second field is a reliable maximum of the function stack
20198 @node Dynamic Stack Usage Analysis
20199 @section Dynamic Stack Usage Analysis
20202 It is possible to measure the maximum amount of stack used by a task, by
20203 adding a switch to @command{gnatbind}, as:
20206 $ gnatbind -u0 file
20210 With this option, at each task termination, its stack usage is output on
20212 It is not always convenient to output the stack usage when the program
20213 is still running. Hence, it is possible to delay this output until program
20214 termination. for a given number of tasks specified as the argument of the
20215 @option{-u} option. For instance:
20218 $ gnatbind -u100 file
20222 will buffer the stack usage information of the first 100 tasks to terminate and
20223 output this info at program termination. Results are displayed in four
20227 Index | Task Name | Stack Size | Actual Use [min - max]
20234 is a number associated with each task.
20237 is the name of the task analyzed.
20240 is the maximum size for the stack.
20243 is the measure done by the stack analyzer. In order to prevent overflow,
20244 the stack is not entirely analyzed, and it's not possible to know exactly how
20245 much has actually been used. The real amount of stack used is between the min
20251 The environment task stack, e.g., the stack that contains the main unit, is
20252 only processed when the environment variable GNAT_STACK_LIMIT is set.
20255 @c *********************************
20257 @c *********************************
20258 @node Verifying Properties Using gnatcheck
20259 @chapter Verifying Properties Using @command{gnatcheck}
20261 @cindex @command{gnatcheck}
20264 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20265 of Ada source files according to a given set of semantic rules.
20268 In order to check compliance with a given rule, @command{gnatcheck} has to
20269 semantically analyze the Ada sources.
20270 Therefore, checks can only be performed on
20271 legal Ada units. Moreover, when a unit depends semantically upon units located
20272 outside the current directory, the source search path has to be provided when
20273 calling @command{gnatcheck}, either through a specified project file or
20274 through @command{gnatcheck} switches as described below.
20276 A number of rules are predefined in @command{gnatcheck} and are described
20277 later in this chapter.
20278 You can also add new rules, by modifying the @command{gnatcheck} code and
20279 rebuilding the tool. In order to add a simple rule making some local checks,
20280 a small amount of straightforward ASIS-based programming is usually needed.
20282 Project support for @command{gnatcheck} is provided by the GNAT
20283 driver (see @ref{The GNAT Driver and Project Files}).
20285 Invoking @command{gnatcheck} on the command line has the form:
20288 $ gnatcheck @ovar{switches} @{@var{filename}@}
20289 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20290 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20297 @var{switches} specify the general tool options
20300 Each @var{filename} is the name (including the extension) of a source
20301 file to process. ``Wildcards'' are allowed, and
20302 the file name may contain path information.
20305 Each @var{arg_list_filename} is the name (including the extension) of a text
20306 file containing the names of the source files to process, separated by spaces
20310 @var{gcc_switches} is a list of switches for
20311 @command{gcc}. They will be passed on to all compiler invocations made by
20312 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20313 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20314 and use the @option{-gnatec} switch to set the configuration file.
20317 @var{rule_options} is a list of options for controlling a set of
20318 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20322 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20325 * Format of the Report File::
20326 * General gnatcheck Switches::
20327 * gnatcheck Rule Options::
20328 * Adding the Results of Compiler Checks to gnatcheck Output::
20329 * Project-Wide Checks::
20330 * Predefined Rules::
20333 @node Format of the Report File
20334 @section Format of the Report File
20335 @cindex Report file (for @code{gnatcheck})
20338 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20340 It also creates, in the current
20341 directory, a text file named @file{^gnatcheck.out^GNATCHECK.OUT^} that
20342 contains the complete report of the last gnatcheck run. This report contains:
20344 @item a list of the Ada source files being checked,
20345 @item a list of enabled and disabled rules,
20346 @item a list of the diagnostic messages, ordered in three different ways
20347 and collected in three separate
20348 sections. Section 1 contains the raw list of diagnostic messages. It
20349 corresponds to the output going to @file{stdout}. Section 2 contains
20350 messages ordered by rules.
20351 Section 3 contains messages ordered by source files.
20354 @node General gnatcheck Switches
20355 @section General @command{gnatcheck} Switches
20358 The following switches control the general @command{gnatcheck} behavior
20362 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20364 Process all units including those with read-only ALI files such as
20365 those from GNAT Run-Time library.
20369 @cindex @option{-d} (@command{gnatcheck})
20374 @cindex @option{-dd} (@command{gnatcheck})
20376 Progress indicator mode (for use in GPS)
20379 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20381 List the predefined and user-defined rules. For more details see
20382 @ref{Predefined Rules}.
20384 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20386 Use full source locations references in the report file. For a construct from
20387 a generic instantiation a full source location is a chain from the location
20388 of this construct in the generic unit to the place where this unit is
20391 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20392 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20393 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20394 the default value is 500. Zero means that there is no limitation on
20395 the number of diagnostic messages to be printed into Stdout.
20397 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20399 Quiet mode. All the diagnoses about rule violations are placed in the
20400 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20402 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20404 Short format of the report file (no version information, no list of applied
20405 rules, no list of checked sources is included)
20407 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20408 @item ^-s1^/COMPILER_STYLE^
20409 Include the compiler-style section in the report file
20411 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20412 @item ^-s2^/BY_RULES^
20413 Include the section containing diagnoses ordered by rules in the report file
20415 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20416 @item ^-s3^/BY_FILES_BY_RULES^
20417 Include the section containing diagnoses ordered by files and then by rules
20420 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20421 @item ^-v^/VERBOSE^
20422 Verbose mode; @command{gnatcheck} generates version information and then
20423 a trace of sources being processed.
20428 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20429 @option{^-s2^/BY_RULES^} or
20430 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20431 then the @command{gnatcheck} report file will only contain sections
20432 explicitly denoted by these options.
20434 @node gnatcheck Rule Options
20435 @section @command{gnatcheck} Rule Options
20438 The following options control the processing performed by
20439 @command{gnatcheck}.
20442 @cindex @option{+ALL} (@command{gnatcheck})
20444 Turn all the rule checks ON.
20446 @cindex @option{-ALL} (@command{gnatcheck})
20448 Turn all the rule checks OFF.
20450 @cindex @option{+R} (@command{gnatcheck})
20451 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20452 Turn on the check for a specified rule with the specified parameter, if any.
20453 @var{rule_id} must be the identifier of one of the currently implemented rules
20454 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20455 are not case-sensitive. The @var{param} item must
20456 be a string representing a valid parameter(s) for the specified rule.
20457 If it contains any space characters then this string must be enclosed in
20460 @cindex @option{-R} (@command{gnatcheck})
20461 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20462 Turn off the check for a specified rule with the specified parameter, if any.
20464 @cindex @option{-from} (@command{gnatcheck})
20465 @item -from=@var{rule_option_filename}
20466 Read the rule options from the text file @var{rule_option_filename}, referred as
20467 ``rule file'' below.
20472 The default behavior is that all the rule checks are disabled.
20474 A rule file is a text file containing a set of rule options.
20475 @cindex Rule file (for @code{gnatcheck})
20476 The file may contain empty lines and Ada-style comments (comment
20477 lines and end-of-line comments). The rule file has free format; that is,
20478 you do not have to start a new rule option on a new line.
20480 A rule file may contain other @option{-from=@var{rule_option_filename}}
20481 options, each such option being replaced with the content of the
20482 corresponding rule file during the rule files processing. In case a
20483 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20484 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20485 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20486 the processing of rule files is interrupted and a part of their content
20490 @node Adding the Results of Compiler Checks to gnatcheck Output
20491 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20494 The @command{gnatcheck} tool can include in the generated diagnostic messages
20496 the report file the results of the checks performed by the compiler. Though
20497 disabled by default, this effect may be obtained by using @option{+R} with
20498 the following rule identifiers and parameters:
20502 To record restrictions violations (that are performed by the compiler if the
20503 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20505 @code{Restrictions} with the same parameters as pragma
20506 @code{Restrictions} or @code{Restriction_Warnings}.
20509 To record compiler style checks(@pxref{Style Checking}), use the rule named
20510 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20511 which enables all the standard style checks that corresponds to @option{-gnatyy}
20512 GNAT style check option, or a string that has exactly the same
20513 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20514 @code{Style_Checks} (for further information about this pragma,
20515 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
20518 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20519 named @code{Warnings} with a parameter that is a valid
20520 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20521 (for further information about this pragma, @pxref{Pragma Warnings,,,
20522 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20523 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20524 all the specific warnings, but not suppresses the warning mode,
20525 and 'e' parameter, corresponding to @option{-gnatwe} that means
20526 "treat warnings as errors", does not have any effect.
20530 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20531 option with the corresponding restriction name as a parameter. @code{-R} is
20532 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20533 warnings and style checks, use the corresponding warning and style options.
20535 @node Project-Wide Checks
20536 @section Project-Wide Checks
20537 @cindex Project-wide checks (for @command{gnatcheck})
20540 In order to perform checks on all units of a given project, you can use
20541 the GNAT driver along with the @option{-P} option:
20543 gnat check -Pproj -rules -from=my_rules
20547 If the project @code{proj} depends upon other projects, you can perform
20548 checks on the project closure using the @option{-U} option:
20550 gnat check -Pproj -U -rules -from=my_rules
20554 Finally, if not all the units are relevant to a particular main
20555 program in the project closure, you can perform checks for the set
20556 of units needed to create a given main program (unit closure) using
20557 the @option{-U} option followed by the name of the main unit:
20559 gnat check -Pproj -U main -rules -from=my_rules
20563 @node Predefined Rules
20564 @section Predefined Rules
20565 @cindex Predefined rules (for @command{gnatcheck})
20568 @c (Jan 2007) Since the global rules are still under development and are not
20569 @c documented, there is no point in explaining the difference between
20570 @c global and local rules
20572 A rule in @command{gnatcheck} is either local or global.
20573 A @emph{local rule} is a rule that applies to a well-defined section
20574 of a program and that can be checked by analyzing only this section.
20575 A @emph{global rule} requires analysis of some global properties of the
20576 whole program (mostly related to the program call graph).
20577 As of @value{NOW}, the implementation of global rules should be
20578 considered to be at a preliminary stage. You can use the
20579 @option{+GLOBAL} option to enable all the global rules, and the
20580 @option{-GLOBAL} rule option to disable all the global rules.
20582 All the global rules in the list below are
20583 so indicated by marking them ``GLOBAL''.
20584 This +GLOBAL and -GLOBAL options are not
20585 included in the list of gnatcheck options above, because at the moment they
20586 are considered as a temporary debug options.
20588 @command{gnatcheck} performs rule checks for generic
20589 instances only for global rules. This limitation may be relaxed in a later
20594 The following subsections document the rules implemented in
20595 @command{gnatcheck}.
20596 The subsection title is the same as the rule identifier, which may be
20597 used as a parameter of the @option{+R} or @option{-R} options.
20601 * Abstract_Type_Declarations::
20602 * Anonymous_Arrays::
20603 * Anonymous_Subtypes::
20605 * Boolean_Relational_Operators::
20607 * Ceiling_Violations::
20609 * Controlled_Type_Declarations::
20610 * Declarations_In_Blocks::
20611 * Default_Parameters::
20612 * Discriminated_Records::
20613 * Enumeration_Ranges_In_CASE_Statements::
20614 * Exceptions_As_Control_Flow::
20615 * EXIT_Statements_With_No_Loop_Name::
20616 * Expanded_Loop_Exit_Names::
20617 * Explicit_Full_Discrete_Ranges::
20618 * Float_Equality_Checks::
20619 * Forbidden_Pragmas::
20620 * Function_Style_Procedures::
20621 * Generics_In_Subprograms::
20622 * GOTO_Statements::
20623 * Implicit_IN_Mode_Parameters::
20624 * Implicit_SMALL_For_Fixed_Point_Types::
20625 * Improperly_Located_Instantiations::
20626 * Improper_Returns::
20627 * Library_Level_Subprograms::
20630 * Improperly_Called_Protected_Entries::
20633 * Misnamed_Identifiers::
20634 * Multiple_Entries_In_Protected_Definitions::
20636 * Non_Qualified_Aggregates::
20637 * Non_Short_Circuit_Operators::
20638 * Non_SPARK_Attributes::
20639 * Non_Tagged_Derived_Types::
20640 * Non_Visible_Exceptions::
20641 * Numeric_Literals::
20642 * OTHERS_In_Aggregates::
20643 * OTHERS_In_CASE_Statements::
20644 * OTHERS_In_Exception_Handlers::
20645 * Outer_Loop_Exits::
20646 * Overloaded_Operators::
20647 * Overly_Nested_Control_Structures::
20648 * Parameters_Out_Of_Order::
20649 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20650 * Positional_Actuals_For_Defaulted_Parameters::
20651 * Positional_Components::
20652 * Positional_Generic_Parameters::
20653 * Positional_Parameters::
20654 * Predefined_Numeric_Types::
20655 * Raising_External_Exceptions::
20656 * Raising_Predefined_Exceptions::
20657 * Separate_Numeric_Error_Handlers::
20660 * Side_Effect_Functions::
20663 * Unassigned_OUT_Parameters::
20664 * Uncommented_BEGIN_In_Package_Bodies::
20665 * Unconstrained_Array_Returns::
20666 * Universal_Ranges::
20667 * Unnamed_Blocks_And_Loops::
20669 * Unused_Subprograms::
20671 * USE_PACKAGE_Clauses::
20672 * Volatile_Objects_Without_Address_Clauses::
20676 @node Abstract_Type_Declarations
20677 @subsection @code{Abstract_Type_Declarations}
20678 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
20681 Flag all declarations of abstract types. For an abstract private
20682 type, both the private and full type declarations are flagged.
20684 This rule has no parameters.
20687 @node Anonymous_Arrays
20688 @subsection @code{Anonymous_Arrays}
20689 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
20692 Flag all anonymous array type definitions (by Ada semantics these can only
20693 occur in object declarations).
20695 This rule has no parameters.
20697 @node Anonymous_Subtypes
20698 @subsection @code{Anonymous_Subtypes}
20699 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
20702 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
20703 any instance of a subtype indication with a constraint, other than one
20704 that occurs immediately within a subtype declaration. Any use of a range
20705 other than as a constraint used immediately within a subtype declaration
20706 is considered as an anonymous subtype.
20708 An effect of this rule is that @code{for} loops such as the following are
20709 flagged (since @code{1..N} is formally a ``range''):
20711 @smallexample @c ada
20712 for I in 1 .. N loop
20718 Declaring an explicit subtype solves the problem:
20720 @smallexample @c ada
20721 subtype S is Integer range 1..N;
20729 This rule has no parameters.
20732 @subsection @code{Blocks}
20733 @cindex @code{Blocks} rule (for @command{gnatcheck})
20736 Flag each block statement.
20738 This rule has no parameters.
20740 @node Boolean_Relational_Operators
20741 @subsection @code{Boolean_Relational_Operators}
20742 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
20745 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
20746 ``>='', ``='' and ``/='') for the predefined Boolean type.
20747 (This rule is useful in enforcing the SPARK language restrictions.)
20749 Calls to predefined relational operators of any type derived from
20750 @code{Standard.Boolean} are not detected. Calls to user-defined functions
20751 with these designators, and uses of operators that are renamings
20752 of the predefined relational operators for @code{Standard.Boolean},
20753 are likewise not detected.
20755 This rule has no parameters.
20758 @node Ceiling_Violations
20759 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
20760 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
20763 Flag invocations of a protected operation by a task whose priority exceeds
20764 the protected object's ceiling.
20766 As of @value{NOW}, this rule has the following limitations:
20771 We consider only pragmas Priority and Interrupt_Priority as means to define
20772 a task/protected operation priority. We do not consider the effect of using
20773 Ada.Dynamic_Priorities.Set_Priority procedure;
20776 We consider only base task priorities, and no priority inheritance. That is,
20777 we do not make a difference between calls issued during task activation and
20778 execution of the sequence of statements from task body;
20781 Any situation when the priority of protected operation caller is set by a
20782 dynamic expression (that is, the corresponding Priority or
20783 Interrupt_Priority pragma has a non-static expression as an argument) we
20784 treat as a priority inconsistency (and, therefore, detect this situation).
20788 At the moment the notion of the main subprogram is not implemented in
20789 gnatcheck, so any pragma Priority in a library level subprogram body (in case
20790 if this subprogram can be a main subprogram of a partition) changes the
20791 priority of an environment task. So if we have more then one such pragma in
20792 the set of processed sources, the pragma that is processed last, defines the
20793 priority of an environment task.
20795 This rule has no parameters.
20798 @node Controlled_Type_Declarations
20799 @subsection @code{Controlled_Type_Declarations}
20800 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
20803 Flag all declarations of controlled types. A declaration of a private type
20804 is flagged if its full declaration declares a controlled type. A declaration
20805 of a derived type is flagged if its ancestor type is controlled. Subtype
20806 declarations are not checked. A declaration of a type that itself is not a
20807 descendant of a type declared in @code{Ada.Finalization} but has a controlled
20808 component is not checked.
20810 This rule has no parameters.
20814 @node Declarations_In_Blocks
20815 @subsection @code{Declarations_In_Blocks}
20816 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
20819 Flag all block statements containing local declarations. A @code{declare}
20820 block with an empty @i{declarative_part} or with a @i{declarative part}
20821 containing only pragmas and/or @code{use} clauses is not flagged.
20823 This rule has no parameters.
20826 @node Default_Parameters
20827 @subsection @code{Default_Parameters}
20828 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
20831 Flag all default expressions for subprogram parameters. Parameter
20832 declarations of formal and generic subprograms are also checked.
20834 This rule has no parameters.
20837 @node Discriminated_Records
20838 @subsection @code{Discriminated_Records}
20839 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
20842 Flag all declarations of record types with discriminants. Only the
20843 declarations of record and record extension types are checked. Incomplete,
20844 formal, private, derived and private extension type declarations are not
20845 checked. Task and protected type declarations also are not checked.
20847 This rule has no parameters.
20850 @node Enumeration_Ranges_In_CASE_Statements
20851 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
20852 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
20855 Flag each use of a range of enumeration literals as a choice in a
20856 @code{case} statement.
20857 All forms for specifying a range (explicit ranges
20858 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
20859 An enumeration range is
20860 flagged even if contains exactly one enumeration value or no values at all. A
20861 type derived from an enumeration type is considered as an enumeration type.
20863 This rule helps prevent maintenance problems arising from adding an
20864 enumeration value to a type and having it implicitly handled by an existing
20865 @code{case} statement with an enumeration range that includes the new literal.
20867 This rule has no parameters.
20870 @node Exceptions_As_Control_Flow
20871 @subsection @code{Exceptions_As_Control_Flow}
20872 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
20875 Flag each place where an exception is explicitly raised and handled in the
20876 same subprogram body. A @code{raise} statement in an exception handler,
20877 package body, task body or entry body is not flagged.
20879 The rule has no parameters.
20881 @node EXIT_Statements_With_No_Loop_Name
20882 @subsection @code{EXIT_Statements_With_No_Loop_Name}
20883 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
20886 Flag each @code{exit} statement that does not specify the name of the loop
20889 The rule has no parameters.
20892 @node Expanded_Loop_Exit_Names
20893 @subsection @code{Expanded_Loop_Exit_Names}
20894 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
20897 Flag all expanded loop names in @code{exit} statements.
20899 This rule has no parameters.
20901 @node Explicit_Full_Discrete_Ranges
20902 @subsection @code{Explicit_Full_Discrete_Ranges}
20903 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
20906 Flag each discrete range that has the form @code{A'First .. A'Last}.
20908 This rule has no parameters.
20910 @node Float_Equality_Checks
20911 @subsection @code{Float_Equality_Checks}
20912 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
20915 Flag all calls to the predefined equality operations for floating-point types.
20916 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
20917 User-defined equality operations are not flagged, nor are ``@code{=}''
20918 and ``@code{/=}'' operations for fixed-point types.
20920 This rule has no parameters.
20923 @node Forbidden_Pragmas
20924 @subsection @code{Forbidden_Pragmas}
20925 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
20928 Flag each use of the specified pragmas. The pragmas to be detected
20929 are named in the rule's parameters.
20931 This rule has the following parameters:
20934 @item For the @option{+R} option
20937 @item @emph{Pragma_Name}
20938 Adds the specified pragma to the set of pragmas to be
20939 checked and sets the checks for all the specified pragmas
20940 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
20941 does not correspond to any pragma name defined in the Ada
20942 standard or to the name of a GNAT-specific pragma defined
20943 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20944 Manual}, it is treated as the name of unknown pragma.
20947 All the GNAT-specific pragmas are detected; this sets
20948 the checks for all the specified pragmas ON.
20951 All pragmas are detected; this sets the rule ON.
20954 @item For the @option{-R} option
20956 @item @emph{Pragma_Name}
20957 Removes the specified pragma from the set of pragmas to be
20958 checked without affecting checks for
20959 other pragmas. @emph{Pragma_Name} is treated as a name
20960 of a pragma. If it does not correspond to any pragma
20961 defined in the Ada standard or to any name defined in
20962 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
20963 this option is treated as turning OFF detection of all unknown pragmas.
20966 Turn OFF detection of all GNAT-specific pragmas
20969 Clear the list of the pragmas to be detected and
20975 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
20976 the syntax of an Ada identifier and therefore can not be considered
20977 as a pragma name, a diagnostic message is generated and the corresponding
20978 parameter is ignored.
20980 When more then one parameter is given in the same rule option, the parameters
20981 must be separated by a comma.
20983 If more then one option for this rule is specified for the @command{gnatcheck}
20984 call, a new option overrides the previous one(s).
20986 The @option{+R} option with no parameters turns the rule ON with the set of
20987 pragmas to be detected defined by the previous rule options.
20988 (By default this set is empty, so if the only option specified for the rule is
20989 @option{+RForbidden_Pragmas} (with
20990 no parameter), then the rule is enabled, but it does not detect anything).
20991 The @option{-R} option with no parameter turns the rule OFF, but it does not
20992 affect the set of pragmas to be detected.
20997 @node Function_Style_Procedures
20998 @subsection @code{Function_Style_Procedures}
20999 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21002 Flag each procedure that can be rewritten as a function. A procedure can be
21003 converted into a function if it has exactly one parameter of mode @code{out}
21004 and no parameters of mode @code{in out}. Procedure declarations,
21005 formal procedure declarations, and generic procedure declarations are always
21007 bodies and body stubs are flagged only if they do not have corresponding
21008 separate declarations. Procedure renamings and procedure instantiations are
21011 If a procedure can be rewritten as a function, but its @code{out} parameter is
21012 of a limited type, it is not flagged.
21014 Protected procedures are not flagged. Null procedures also are not flagged.
21016 This rule has no parameters.
21019 @node Generics_In_Subprograms
21020 @subsection @code{Generics_In_Subprograms}
21021 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21024 Flag each declaration of a generic unit in a subprogram. Generic
21025 declarations in the bodies of generic subprograms are also flagged.
21026 A generic unit nested in another generic unit is not flagged.
21027 If a generic unit is
21028 declared in a local package that is declared in a subprogram body, the
21029 generic unit is flagged.
21031 This rule has no parameters.
21034 @node GOTO_Statements
21035 @subsection @code{GOTO_Statements}
21036 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21039 Flag each occurrence of a @code{goto} statement.
21041 This rule has no parameters.
21044 @node Implicit_IN_Mode_Parameters
21045 @subsection @code{Implicit_IN_Mode_Parameters}
21046 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21049 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21050 Note that @code{access} parameters, although they technically behave
21051 like @code{in} parameters, are not flagged.
21053 This rule has no parameters.
21056 @node Implicit_SMALL_For_Fixed_Point_Types
21057 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21058 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21061 Flag each fixed point type declaration that lacks an explicit
21062 representation clause to define its @code{'Small} value.
21063 Since @code{'Small} can be defined only for ordinary fixed point types,
21064 decimal fixed point type declarations are not checked.
21066 This rule has no parameters.
21069 @node Improperly_Located_Instantiations
21070 @subsection @code{Improperly_Located_Instantiations}
21071 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21074 Flag all generic instantiations in library-level package specs
21075 (including library generic packages) and in all subprogram bodies.
21077 Instantiations in task and entry bodies are not flagged. Instantiations in the
21078 bodies of protected subprograms are flagged.
21080 This rule has no parameters.
21084 @node Improper_Returns
21085 @subsection @code{Improper_Returns}
21086 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21089 Flag each explicit @code{return} statement in procedures, and
21090 multiple @code{return} statements in functions.
21091 Diagnostic messages are generated for all @code{return} statements
21092 in a procedure (thus each procedure must be written so that it
21093 returns implicitly at the end of its statement part),
21094 and for all @code{return} statements in a function after the first one.
21095 This rule supports the stylistic convention that each subprogram
21096 should have no more than one point of normal return.
21098 This rule has no parameters.
21101 @node Library_Level_Subprograms
21102 @subsection @code{Library_Level_Subprograms}
21103 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21106 Flag all library-level subprograms (including generic subprogram instantiations).
21108 This rule has no parameters.
21111 @node Local_Packages
21112 @subsection @code{Local_Packages}
21113 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21116 Flag all local packages declared in package and generic package
21118 Local packages in bodies are not flagged.
21120 This rule has no parameters.
21123 @node Improperly_Called_Protected_Entries
21124 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21125 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21128 Flag each protected entry that can be called from more than one task.
21130 This rule has no parameters.
21134 @subsection @code{Metrics}
21135 @cindex @code{Metrics} rule (for @command{gnatcheck})
21138 There is a set of checks based on computing a metric value and comparing the
21139 result with the specified upper (or lower, depending on a specific metric)
21140 value specified for a given metric. A construct is flagged if a given metric
21141 is applicable (can be computed) for it and the computed value is greater
21142 then (lover then) the specified upper (lower) bound.
21144 The name of any metric-based rule consists of the prefix @code{Metrics_}
21145 followed by the name of the corresponding metric (see the table below).
21146 For @option{+R} option, each metric-based rule has a numeric parameter
21147 specifying the bound (integer or real, depending on a metric), @option{-R}
21148 option for metric rules does not have a parameter.
21150 The following table shows the metric names for that the corresponding
21151 metrics-based checks are supported by gnatcheck, including the
21152 constraint that must be satisfied by the bound that is specified for the check
21153 and what bound - upper (U) or lower (L) - should be specified.
21155 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21157 @headitem Check Name @tab Description @tab Bounds Value
21160 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21162 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21163 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21164 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21165 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21169 The meaning and the computed values for all these metrics are exactly
21170 the same as for the corresponding metrics in @command{gnatmetric}.
21172 @emph{Example:} the rule
21174 +RMetrics_Cyclomatic_Complexity : 7
21177 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21179 To turn OFF the check for cyclomatic complexity metric, use the following option:
21181 -RMetrics_Cyclomatic_Complexity
21184 @node Misnamed_Identifiers
21185 @subsection @code{Misnamed_Identifiers}
21186 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21189 Flag the declaration of each identifier that does not have a suffix
21190 corresponding to the kind of entity being declared.
21191 The following declarations are checked:
21198 constant declarations (but not number declarations)
21201 package renaming declarations (but not generic package renaming
21206 This rule may have parameters. When used without parameters, the rule enforces
21207 the following checks:
21211 type-defining names end with @code{_T}, unless the type is an access type,
21212 in which case the suffix must be @code{_A}
21214 constant names end with @code{_C}
21216 names defining package renamings end with @code{_R}
21220 For a private or incomplete type declaration the following checks are
21221 made for the defining name suffix:
21225 For an incomplete type declaration: if the corresponding full type
21226 declaration is available, the defining identifier from the full type
21227 declaration is checked, but the defining identifier from the incomplete type
21228 declaration is not; otherwise the defining identifier from the incomplete
21229 type declaration is checked against the suffix specified for type
21233 For a private type declaration (including private extensions), the defining
21234 identifier from the private type declaration is checked against the type
21235 suffix (even if the corresponding full declaration is an access type
21236 declaration), and the defining identifier from the corresponding full type
21237 declaration is not checked.
21241 For a deferred constant, the defining name in the corresponding full constant
21242 declaration is not checked.
21244 Defining names of formal types are not checked.
21246 The rule may have the following parameters:
21250 For the @option{+R} option:
21253 Sets the default listed above for all the names to be checked.
21255 @item Type_Suffix=@emph{string}
21256 Specifies the suffix for a type name.
21258 @item Access_Suffix=@emph{string}
21259 Specifies the suffix for an access type name. If
21260 this parameter is set, it overrides for access
21261 types the suffix set by the @code{Type_Suffix} parameter.
21263 @item Constant_Suffix=@emph{string}
21264 Specifies the suffix for a constant name.
21266 @item Renaming_Suffix=@emph{string}
21267 Specifies the suffix for a package renaming name.
21271 For the @option{-R} option:
21274 Remove all the suffixes specified for the
21275 identifier suffix checks, whether by default or
21276 as specified by other rule parameters. All the
21277 checks for this rule are disabled as a result.
21280 Removes the suffix specified for types. This
21281 disables checks for types but does not disable
21282 any other checks for this rule (including the
21283 check for access type names if @code{Access_Suffix} is
21286 @item Access_Suffix
21287 Removes the suffix specified for access types.
21288 This disables checks for access type names but
21289 does not disable any other checks for this rule.
21290 If @code{Type_Suffix} is set, access type names are
21291 checked as ordinary type names.
21293 @item Constant_Suffix
21294 Removes the suffix specified for constants. This
21295 disables checks for constant names but does not
21296 disable any other checks for this rule.
21298 @item Renaming_Suffix
21299 Removes the suffix specified for package
21300 renamings. This disables checks for package
21301 renamings but does not disable any other checks
21307 If more than one parameter is used, parameters must be separated by commas.
21309 If more than one option is specified for the @command{gnatcheck} invocation,
21310 a new option overrides the previous one(s).
21312 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21314 name suffixes specified by previous options used for this rule.
21316 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21317 all the checks but keeps
21318 all the suffixes specified by previous options used for this rule.
21320 The @emph{string} value must be a valid suffix for an Ada identifier (after
21321 trimming all the leading and trailing space characters, if any).
21322 Parameters are not case sensitive, except the @emph{string} part.
21324 If any error is detected in a rule parameter, the parameter is ignored.
21325 In such a case the options that are set for the rule are not
21330 @node Multiple_Entries_In_Protected_Definitions
21331 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21332 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21335 Flag each protected definition (i.e., each protected object/type declaration)
21336 that defines more than one entry.
21337 Diagnostic messages are generated for all the entry declarations
21338 except the first one. An entry family is counted as one entry. Entries from
21339 the private part of the protected definition are also checked.
21341 This rule has no parameters.
21344 @subsection @code{Name_Clashes}
21345 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21348 Check that certain names are not used as defining identifiers. To activate
21349 this rule, you need to supply a reference to the dictionary file(s) as a rule
21350 parameter(s) (more then one dictionary file can be specified). If no
21351 dictionary file is set, this rule will not cause anything to be flagged.
21352 Only defining occurrences, not references, are checked.
21353 The check is not case-sensitive.
21355 This rule is enabled by default, but without setting any corresponding
21356 dictionary file(s); thus the default effect is to do no checks.
21358 A dictionary file is a plain text file. The maximum line length for this file
21359 is 1024 characters. If the line is longer then this limit, extra characters
21362 Each line can be either an empty line, a comment line, or a line containing
21363 a list of identifiers separated by space or HT characters.
21364 A comment is an Ada-style comment (from @code{--} to end-of-line).
21365 Identifiers must follow the Ada syntax for identifiers.
21366 A line containing one or more identifiers may end with a comment.
21368 @node Non_Qualified_Aggregates
21369 @subsection @code{Non_Qualified_Aggregates}
21370 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21373 Flag each non-qualified aggregate.
21374 A non-qualified aggregate is an
21375 aggregate that is not the expression of a qualified expression. A
21376 string literal is not considered an aggregate, but an array
21377 aggregate of a string type is considered as a normal aggregate.
21378 Aggregates of anonymous array types are not flagged.
21380 This rule has no parameters.
21383 @node Non_Short_Circuit_Operators
21384 @subsection @code{Non_Short_Circuit_Operators}
21385 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21388 Flag all calls to predefined @code{and} and @code{or} operators for
21389 any boolean type. Calls to
21390 user-defined @code{and} and @code{or} and to operators defined by renaming
21391 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21392 operators for modular types or boolean array types are not flagged.
21394 This rule has no parameters.
21398 @node Non_SPARK_Attributes
21399 @subsection @code{Non_SPARK_Attributes}
21400 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21403 The SPARK language defines the following subset of Ada 95 attribute
21404 designators as those that can be used in SPARK programs. The use of
21405 any other attribute is flagged.
21408 @item @code{'Adjacent}
21411 @item @code{'Ceiling}
21412 @item @code{'Component_Size}
21413 @item @code{'Compose}
21414 @item @code{'Copy_Sign}
21415 @item @code{'Delta}
21416 @item @code{'Denorm}
21417 @item @code{'Digits}
21418 @item @code{'Exponent}
21419 @item @code{'First}
21420 @item @code{'Floor}
21422 @item @code{'Fraction}
21424 @item @code{'Leading_Part}
21425 @item @code{'Length}
21426 @item @code{'Machine}
21427 @item @code{'Machine_Emax}
21428 @item @code{'Machine_Emin}
21429 @item @code{'Machine_Mantissa}
21430 @item @code{'Machine_Overflows}
21431 @item @code{'Machine_Radix}
21432 @item @code{'Machine_Rounds}
21435 @item @code{'Model}
21436 @item @code{'Model_Emin}
21437 @item @code{'Model_Epsilon}
21438 @item @code{'Model_Mantissa}
21439 @item @code{'Model_Small}
21440 @item @code{'Modulus}
21443 @item @code{'Range}
21444 @item @code{'Remainder}
21445 @item @code{'Rounding}
21446 @item @code{'Safe_First}
21447 @item @code{'Safe_Last}
21448 @item @code{'Scaling}
21449 @item @code{'Signed_Zeros}
21451 @item @code{'Small}
21453 @item @code{'Truncation}
21454 @item @code{'Unbiased_Rounding}
21456 @item @code{'Valid}
21460 This rule has no parameters.
21463 @node Non_Tagged_Derived_Types
21464 @subsection @code{Non_Tagged_Derived_Types}
21465 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21468 Flag all derived type declarations that do not have a record extension part.
21470 This rule has no parameters.
21474 @node Non_Visible_Exceptions
21475 @subsection @code{Non_Visible_Exceptions}
21476 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21479 Flag constructs leading to the possibility of propagating an exception
21480 out of the scope in which the exception is declared.
21481 Two cases are detected:
21485 An exception declaration in a subprogram body, task body or block
21486 statement is flagged if the body or statement does not contain a handler for
21487 that exception or a handler with an @code{others} choice.
21490 A @code{raise} statement in an exception handler of a subprogram body,
21491 task body or block statement is flagged if it (re)raises a locally
21492 declared exception. This may occur under the following circumstances:
21495 it explicitly raises a locally declared exception, or
21497 it does not specify an exception name (i.e., it is simply @code{raise;})
21498 and the enclosing handler contains a locally declared exception in its
21504 Renamings of local exceptions are not flagged.
21506 This rule has no parameters.
21509 @node Numeric_Literals
21510 @subsection @code{Numeric_Literals}
21511 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21514 Flag each use of a numeric literal in an index expression, and in any
21515 circumstance except for the following:
21519 a literal occurring in the initialization expression for a constant
21520 declaration or a named number declaration, or
21523 an integer literal that is less than or equal to a value
21524 specified by the @option{N} rule parameter.
21528 This rule may have the following parameters for the @option{+R} option:
21532 @emph{N} is an integer literal used as the maximal value that is not flagged
21533 (i.e., integer literals not exceeding this value are allowed)
21536 All integer literals are flagged
21540 If no parameters are set, the maximum unflagged value is 1.
21542 The last specified check limit (or the fact that there is no limit at
21543 all) is used when multiple @option{+R} options appear.
21545 The @option{-R} option for this rule has no parameters.
21546 It disables the rule but retains the last specified maximum unflagged value.
21547 If the @option{+R} option subsequently appears, this value is used as the
21548 threshold for the check.
21551 @node OTHERS_In_Aggregates
21552 @subsection @code{OTHERS_In_Aggregates}
21553 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21556 Flag each use of an @code{others} choice in extension aggregates.
21557 In record and array aggregates, an @code{others} choice is flagged unless
21558 it is used to refer to all components, or to all but one component.
21560 If, in case of a named array aggregate, there are two associations, one
21561 with an @code{others} choice and another with a discrete range, the
21562 @code{others} choice is flagged even if the discrete range specifies
21563 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21565 This rule has no parameters.
21567 @node OTHERS_In_CASE_Statements
21568 @subsection @code{OTHERS_In_CASE_Statements}
21569 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21572 Flag any use of an @code{others} choice in a @code{case} statement.
21574 This rule has no parameters.
21576 @node OTHERS_In_Exception_Handlers
21577 @subsection @code{OTHERS_In_Exception_Handlers}
21578 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21581 Flag any use of an @code{others} choice in an exception handler.
21583 This rule has no parameters.
21586 @node Outer_Loop_Exits
21587 @subsection @code{Outer_Loop_Exits}
21588 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21591 Flag each @code{exit} statement containing a loop name that is not the name
21592 of the immediately enclosing @code{loop} statement.
21594 This rule has no parameters.
21597 @node Overloaded_Operators
21598 @subsection @code{Overloaded_Operators}
21599 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21602 Flag each function declaration that overloads an operator symbol.
21603 A function body is checked only if the body does not have a
21604 separate spec. Formal functions are also checked. For a
21605 renaming declaration, only renaming-as-declaration is checked
21607 This rule has no parameters.
21610 @node Overly_Nested_Control_Structures
21611 @subsection @code{Overly_Nested_Control_Structures}
21612 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21615 Flag each control structure whose nesting level exceeds the value provided
21616 in the rule parameter.
21618 The control structures checked are the following:
21621 @item @code{if} statement
21622 @item @code{case} statement
21623 @item @code{loop} statement
21624 @item Selective accept statement
21625 @item Timed entry call statement
21626 @item Conditional entry call
21627 @item Asynchronous select statement
21631 The rule has the following parameter for the @option{+R} option:
21635 Positive integer specifying the maximal control structure nesting
21636 level that is not flagged
21640 If the parameter for the @option{+R} option is not specified or
21641 if it is not a positive integer, @option{+R} option is ignored.
21643 If more then one option is specified for the gnatcheck call, the later option and
21644 new parameter override the previous one(s).
21647 @node Parameters_Out_Of_Order
21648 @subsection @code{Parameters_Out_Of_Order}
21649 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
21652 Flag each subprogram and entry declaration whose formal parameters are not
21653 ordered according to the following scheme:
21657 @item @code{in} and @code{access} parameters first,
21658 then @code{in out} parameters,
21659 and then @code{out} parameters;
21661 @item for @code{in} mode, parameters with default initialization expressions
21666 Only the first violation of the described order is flagged.
21668 The following constructs are checked:
21671 @item subprogram declarations (including null procedures);
21672 @item generic subprogram declarations;
21673 @item formal subprogram declarations;
21674 @item entry declarations;
21675 @item subprogram bodies and subprogram body stubs that do not
21676 have separate specifications
21680 Subprogram renamings are not checked.
21682 This rule has no parameters.
21685 @node Positional_Actuals_For_Defaulted_Generic_Parameters
21686 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
21687 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
21690 Flag each generic actual parameter corresponding to a generic formal
21691 parameter with a default initialization, if positional notation is used.
21693 This rule has no parameters.
21695 @node Positional_Actuals_For_Defaulted_Parameters
21696 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
21697 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
21700 Flag each actual parameter to a subprogram or entry call where the
21701 corresponding formal parameter has a default expression, if positional
21704 This rule has no parameters.
21706 @node Positional_Components
21707 @subsection @code{Positional_Components}
21708 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
21711 Flag each array, record and extension aggregate that includes positional
21714 This rule has no parameters.
21717 @node Positional_Generic_Parameters
21718 @subsection @code{Positional_Generic_Parameters}
21719 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
21722 Flag each instantiation using positional parameter notation.
21724 This rule has no parameters.
21727 @node Positional_Parameters
21728 @subsection @code{Positional_Parameters}
21729 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
21732 Flag each subprogram or entry call using positional parameter notation,
21733 except for the following:
21737 Invocations of prefix or infix operators are not flagged
21739 If the called subprogram or entry has only one formal parameter,
21740 the call is not flagged;
21742 If a subprogram call uses the @emph{Object.Operation} notation, then
21745 the first parameter (that is, @emph{Object}) is not flagged;
21747 if the called subprogram has only two parameters, the second parameter
21748 of the call is not flagged;
21753 This rule has no parameters.
21758 @node Predefined_Numeric_Types
21759 @subsection @code{Predefined_Numeric_Types}
21760 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
21763 Flag each explicit use of the name of any numeric type or subtype defined
21764 in package @code{Standard}.
21766 The rationale for this rule is to detect when the
21767 program may depend on platform-specific characteristics of the implementation
21768 of the predefined numeric types. Note that this rule is over-pessimistic;
21769 for example, a program that uses @code{String} indexing
21770 likely needs a variable of type @code{Integer}.
21771 Another example is the flagging of predefined numeric types with explicit
21774 @smallexample @c ada
21775 subtype My_Integer is Integer range Left .. Right;
21776 Vy_Var : My_Integer;
21780 This rule detects only numeric types and subtypes defined in
21781 @code{Standard}. The use of numeric types and subtypes defined in other
21782 predefined packages (such as @code{System.Any_Priority} or
21783 @code{Ada.Text_IO.Count}) is not flagged
21785 This rule has no parameters.
21789 @node Raising_External_Exceptions
21790 @subsection @code{Raising_External_Exceptions}
21791 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
21794 Flag any @code{raise} statement, in a program unit declared in a library
21795 package or in a generic library package, for an exception that is
21796 neither a predefined exception nor an exception that is also declared (or
21797 renamed) in the visible part of the package.
21799 This rule has no parameters.
21803 @node Raising_Predefined_Exceptions
21804 @subsection @code{Raising_Predefined_Exceptions}
21805 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
21808 Flag each @code{raise} statement that raises a predefined exception
21809 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
21810 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
21812 This rule has no parameters.
21814 @node Separate_Numeric_Error_Handlers
21815 @subsection @code{Separate_Numeric_Error_Handlers}
21816 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
21819 Flags each exception handler that contains a choice for
21820 the predefined @code{Constraint_Error} exception, but does not contain
21821 the choice for the predefined @code{Numeric_Error} exception, or
21822 that contains the choice for @code{Numeric_Error}, but does not contain the
21823 choice for @code{Constraint_Error}.
21825 This rule has no parameters.
21829 @subsection @code{Recursion} (under construction, GLOBAL)
21830 @cindex @code{Recursion} rule (for @command{gnatcheck})
21833 Flag recursive subprograms (cycles in the call graph). Declarations, and not
21834 calls, of recursive subprograms are detected.
21836 This rule has no parameters.
21840 @node Side_Effect_Functions
21841 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
21842 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
21845 Flag functions with side effects.
21847 We define a side effect as changing any data object that is not local for the
21848 body of this function.
21850 At the moment, we do NOT consider a side effect any input-output operations
21851 (changing a state or a content of any file).
21853 We do not consider protected functions for this rule (???)
21855 There are the following sources of side effect:
21858 @item Explicit (or direct) side-effect:
21862 direct assignment to a non-local variable;
21865 direct call to an entity that is known to change some data object that is
21866 not local for the body of this function (Note, that if F1 calls F2 and F2
21867 does have a side effect, this does not automatically mean that F1 also
21868 have a side effect, because it may be the case that F2 is declared in
21869 F1's body and it changes some data object that is global for F2, but
21873 @item Indirect side-effect:
21876 Subprogram calls implicitly issued by:
21879 computing initialization expressions from type declarations as a part
21880 of object elaboration or allocator evaluation;
21882 computing implicit parameters of subprogram or entry calls or generic
21887 activation of a task that change some non-local data object (directly or
21891 elaboration code of a package that is a result of a package instantiation;
21894 controlled objects;
21897 @item Situations when we can suspect a side-effect, but the full static check
21898 is either impossible or too hard:
21901 assignment to access variables or to the objects pointed by access
21905 call to a subprogram pointed by access-to-subprogram value
21913 This rule has no parameters.
21917 @subsection @code{Slices}
21918 @cindex @code{Slices} rule (for @command{gnatcheck})
21921 Flag all uses of array slicing
21923 This rule has no parameters.
21926 @node Unassigned_OUT_Parameters
21927 @subsection @code{Unassigned_OUT_Parameters}
21928 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
21931 Flags procedures' @code{out} parameters that are not assigned, and
21932 identifies the contexts in which the assignments are missing.
21934 An @code{out} parameter is flagged in the statements in the procedure
21935 body's handled sequence of statements (before the procedure body's
21936 @code{exception} part, if any) if this sequence of statements contains
21937 no assignments to the parameter.
21939 An @code{out} parameter is flagged in an exception handler in the exception
21940 part of the procedure body's handled sequence of statements if the handler
21941 contains no assignment to the parameter.
21943 Bodies of generic procedures are also considered.
21945 The following are treated as assignments to an @code{out} parameter:
21949 an assignment statement, with the parameter or some component as the target;
21952 passing the parameter (or one of its components) as an @code{out} or
21953 @code{in out} parameter.
21957 This rule does not have any parameters.
21961 @node Uncommented_BEGIN_In_Package_Bodies
21962 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
21963 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
21966 Flags each package body with declarations and a statement part that does not
21967 include a trailing comment on the line containing the @code{begin} keyword;
21968 this trailing comment needs to specify the package name and nothing else.
21969 The @code{begin} is not flagged if the package body does not
21970 contain any declarations.
21972 If the @code{begin} keyword is placed on the
21973 same line as the last declaration or the first statement, it is flagged
21974 independently of whether the line contains a trailing comment. The
21975 diagnostic message is attached to the line containing the first statement.
21977 This rule has no parameters.
21980 @node Unconstrained_Array_Returns
21981 @subsection @code{Unconstrained_Array_Returns}
21982 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
21985 Flag each function returning an unconstrained array. Function declarations,
21986 function bodies (and body stubs) having no separate specifications,
21987 and generic function instantiations are checked.
21988 Generic function declarations, function calls and function renamings are
21991 This rule has no parameters.
21993 @node Universal_Ranges
21994 @subsection @code{Universal_Ranges}
21995 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
21998 Flag discrete ranges that are a part of an index constraint, constrained
21999 array definition, or @code{for}-loop parameter specification, and whose bounds
22000 are both of type @i{universal_integer}. Ranges that have at least one
22001 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22002 or an expression of non-universal type) are not flagged.
22004 This rule has no parameters.
22007 @node Unnamed_Blocks_And_Loops
22008 @subsection @code{Unnamed_Blocks_And_Loops}
22009 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22012 Flag each unnamed block statement and loop statement.
22014 The rule has no parameters.
22019 @node Unused_Subprograms
22020 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22021 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22024 Flag all unused subprograms.
22026 This rule has no parameters.
22032 @node USE_PACKAGE_Clauses
22033 @subsection @code{USE_PACKAGE_Clauses}
22034 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22037 Flag all @code{use} clauses for packages; @code{use type} clauses are
22040 This rule has no parameters.
22044 @node Volatile_Objects_Without_Address_Clauses
22045 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22046 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22049 Flag each volatile object that does not have an address clause.
22051 The following check is made: if the pragma @code{Volatile} is applied to a
22052 data object or to its type, then an address clause must
22053 be supplied for this object.
22055 This rule does not check the components of data objects,
22056 array components that are volatile as a result of the pragma
22057 @code{Volatile_Components}, or objects that are volatile because
22058 they are atomic as a result of pragmas @code{Atomic} or
22059 @code{Atomic_Components}.
22061 Only variable declarations, and not constant declarations, are checked.
22063 This rule has no parameters.
22066 @c *********************************
22067 @node Creating Sample Bodies Using gnatstub
22068 @chapter Creating Sample Bodies Using @command{gnatstub}
22072 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22073 for library unit declarations.
22075 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22076 driver (see @ref{The GNAT Driver and Project Files}).
22078 To create a body stub, @command{gnatstub} has to compile the library
22079 unit declaration. Therefore, bodies can be created only for legal
22080 library units. Moreover, if a library unit depends semantically upon
22081 units located outside the current directory, you have to provide
22082 the source search path when calling @command{gnatstub}, see the description
22083 of @command{gnatstub} switches below.
22085 By default, all the program unit body stubs generated by @code{gnatstub}
22086 raise the predefined @code{Program_Error} exception, which will catch
22087 accidental calls of generated stubs. This behavior can be changed with
22088 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22091 * Running gnatstub::
22092 * Switches for gnatstub::
22095 @node Running gnatstub
22096 @section Running @command{gnatstub}
22099 @command{gnatstub} has the command-line interface of the form
22102 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22109 is the name of the source file that contains a library unit declaration
22110 for which a body must be created. The file name may contain the path
22112 The file name does not have to follow the GNAT file name conventions. If the
22114 does not follow GNAT file naming conventions, the name of the body file must
22116 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22117 If the file name follows the GNAT file naming
22118 conventions and the name of the body file is not provided,
22121 of the body file from the argument file name by replacing the @file{.ads}
22123 with the @file{.adb} suffix.
22126 indicates the directory in which the body stub is to be placed (the default
22131 is an optional sequence of switches as described in the next section
22134 @node Switches for gnatstub
22135 @section Switches for @command{gnatstub}
22141 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22142 If the destination directory already contains a file with the name of the
22144 for the argument spec file, replace it with the generated body stub.
22146 @item ^-hs^/HEADER=SPEC^
22147 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22148 Put the comment header (i.e., all the comments preceding the
22149 compilation unit) from the source of the library unit declaration
22150 into the body stub.
22152 @item ^-hg^/HEADER=GENERAL^
22153 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22154 Put a sample comment header into the body stub.
22156 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22157 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22158 Use the content of the file as the comment header for a generated body stub.
22162 @cindex @option{-IDIR} (@command{gnatstub})
22164 @cindex @option{-I-} (@command{gnatstub})
22167 @item /NOCURRENT_DIRECTORY
22168 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22170 ^These switches have ^This switch has^ the same meaning as in calls to
22172 ^They define ^It defines ^ the source search path in the call to
22173 @command{gcc} issued
22174 by @command{gnatstub} to compile an argument source file.
22176 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22177 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22178 This switch has the same meaning as in calls to @command{gcc}.
22179 It defines the additional configuration file to be passed to the call to
22180 @command{gcc} issued
22181 by @command{gnatstub} to compile an argument source file.
22183 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22184 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22185 (@var{n} is a non-negative integer). Set the maximum line length in the
22186 body stub to @var{n}; the default is 79. The maximum value that can be
22187 specified is 32767. Note that in the special case of configuration
22188 pragma files, the maximum is always 32767 regardless of whether or
22189 not this switch appears.
22191 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22192 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22193 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22194 the generated body sample to @var{n}.
22195 The default indentation is 3.
22197 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22198 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22199 Order local bodies alphabetically. (By default local bodies are ordered
22200 in the same way as the corresponding local specs in the argument spec file.)
22202 @item ^-i^/INDENTATION=^@var{n}
22203 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22204 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22206 @item ^-k^/TREE_FILE=SAVE^
22207 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22208 Do not remove the tree file (i.e., the snapshot of the compiler internal
22209 structures used by @command{gnatstub}) after creating the body stub.
22211 @item ^-l^/LINE_LENGTH=^@var{n}
22212 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22213 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22215 @item ^--no-exception^/NO_EXCEPTION^
22216 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22217 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22218 This is not always possible for function stubs.
22220 @item ^-o ^/BODY=^@var{body-name}
22221 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22222 Body file name. This should be set if the argument file name does not
22224 the GNAT file naming
22225 conventions. If this switch is omitted the default name for the body will be
22227 from the argument file name according to the GNAT file naming conventions.
22230 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22231 Quiet mode: do not generate a confirmation when a body is
22232 successfully created, and do not generate a message when a body is not
22236 @item ^-r^/TREE_FILE=REUSE^
22237 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22238 Reuse the tree file (if it exists) instead of creating it. Instead of
22239 creating the tree file for the library unit declaration, @command{gnatstub}
22240 tries to find it in the current directory and use it for creating
22241 a body. If the tree file is not found, no body is created. This option
22242 also implies @option{^-k^/SAVE^}, whether or not
22243 the latter is set explicitly.
22245 @item ^-t^/TREE_FILE=OVERWRITE^
22246 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22247 Overwrite the existing tree file. If the current directory already
22248 contains the file which, according to the GNAT file naming rules should
22249 be considered as a tree file for the argument source file,
22251 will refuse to create the tree file needed to create a sample body
22252 unless this option is set.
22254 @item ^-v^/VERBOSE^
22255 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22256 Verbose mode: generate version information.
22260 @c *********************************
22261 @node Generating Ada Bindings for C and C++ headers
22262 @chapter Generating Ada Bindings for C and C++ headers
22266 GNAT now comes with a new experimental binding generator for C and C++
22267 headers which is intended to do 95% of the tedious work of generating
22268 Ada specs from C or C++ header files. Note that this still is a work in
22269 progress, not designed to generate 100% correct Ada specs.
22271 The code generated is using the Ada 2005 syntax, which makes it
22272 easier to interface with other languages than previous versions of Ada.
22275 * Running the binding generator::
22276 * Generating bindings for C++ headers::
22280 @node Running the binding generator
22281 @section Running the binding generator
22284 The binding generator is part of the @command{gcc} compiler and can be
22285 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
22286 spec files for the header files specified on the command line, and all
22287 header files needed by these files transitivitely. For example:
22290 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
22291 $ gcc -c -gnat05 *.ads
22294 will generate, under GNU/Linux, the following files: @file{time_h.ads},
22295 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
22296 correspond to the files @file{/usr/include/time.h},
22297 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
22298 mode these Ada specs.
22300 The @code{-C} switch tells @command{gcc} to extract comments from headers,
22301 and will attempt to generate corresponding Ada comments.
22303 If you want to generate a single Ada file and not the transitive closure, you
22304 can use instead the @option{-fdump-ada-spec-slim} switch.
22306 Note that we recommend when possible to use the @command{g++} driver to
22307 generate bindings, even for most C headers, since this will in general
22308 generate better Ada specs. For generating bindings for C++ headers, it is
22309 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
22310 is equivalent in this case. If @command{g++} cannot work on your C headers
22311 because of incompatibilities between C and C++, then you can fallback to
22312 @command{gcc} instead.
22314 For an example of better bindings generated from the C++ front-end,
22315 the name of the parameters (when available) are actually ignored by the C
22316 front-end. Consider the following C header:
22319 extern void foo (int variable);
22322 with the C front-end, @code{variable} is ignored, and the above is handled as:
22325 extern void foo (int);
22328 generating a generic:
22331 procedure foo (param1 : int);
22334 with the C++ front-end, the name is available, and we generate:
22337 procedure foo (variable : int);
22340 In some cases, the generated bindings will be more complete or more meaningful
22341 when defining some macros, which you can do via the @option{-D} switch. This
22342 is for example the case with @file{Xlib.h} under GNU/Linux:
22345 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
22348 The above will generate more complete bindings than a straight call without
22349 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
22351 In other cases, it is not possible to parse a header file in a stand alone
22352 manner, because other include files need to be included first. In this
22353 case, the solution is to create a small header file including the needed
22354 @code{#include} and possible @code{#define} directives. For example, to
22355 generate Ada bindings for @file{readline/readline.h}, you need to first
22356 include @file{stdio.h}, so you can create a file with the following two
22357 lines in e.g. @file{readline1.h}:
22361 #include <readline/readline.h>
22364 and then generate Ada bindings from this file:
22367 $ g++ -c -fdump-ada-spec readline1.h
22370 @node Generating bindings for C++ headers
22371 @section Generating bindings for C++ headers
22374 Generating bindings for C++ headers is done using the same options, always
22375 with the @command{g++} compiler.
22377 In this mode, C++ classes will be mapped to Ada tagged types, constructors
22378 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
22379 multiple inheritance of abstract classes will be mapped to Ada interfaces
22380 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
22381 information on interfacing to C++).
22383 For example, given the following C++ header file:
22390 virtual int Number_Of_Teeth () = 0;
22395 virtual void Set_Owner (char* Name) = 0;
22401 virtual void Set_Age (int New_Age);
22404 class Dog : Animal, Carnivore, Domestic @{
22409 virtual int Number_Of_Teeth ();
22410 virtual void Set_Owner (char* Name);
22418 The corresponding Ada code is generated:
22420 @smallexample @c ada
22423 package Class_Carnivore is
22424 type Carnivore is limited interface;
22425 pragma Import (CPP, Carnivore);
22427 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
22429 use Class_Carnivore;
22431 package Class_Domestic is
22432 type Domestic is limited interface;
22433 pragma Import (CPP, Domestic);
22435 procedure Set_Owner
22436 (this : access Domestic;
22437 Name : Interfaces.C.Strings.chars_ptr) is abstract;
22439 use Class_Domestic;
22441 package Class_Animal is
22442 type Animal is tagged limited record
22443 Age_Count : aliased int;
22445 pragma Import (CPP, Animal);
22447 procedure Set_Age (this : access Animal; New_Age : int);
22448 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
22452 package Class_Dog is
22453 type Dog is new Animal and Carnivore and Domestic with record
22454 Tooth_Count : aliased int;
22455 Owner : Interfaces.C.Strings.chars_ptr;
22457 pragma Import (CPP, Dog);
22459 function Number_Of_Teeth (this : access Dog) return int;
22460 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
22462 procedure Set_Owner
22463 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
22464 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
22466 function New_Dog return Dog'Class;
22467 pragma CPP_Constructor (New_Dog);
22468 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
22479 @item -fdump-ada-spec
22480 @cindex @option{-fdump-ada-spec} (@command{gcc})
22481 Generate Ada spec files for the given header files transitively (including
22482 all header files that these headers depend upon).
22484 @item -fdump-ada-spec-slim
22485 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
22486 Generate Ada spec files for the header files specified on the command line
22490 @cindex @option{-C} (@command{gcc})
22491 Extract comments from headers and generate Ada comments in the Ada spec files.
22494 @node Other Utility Programs
22495 @chapter Other Utility Programs
22498 This chapter discusses some other utility programs available in the Ada
22502 * Using Other Utility Programs with GNAT::
22503 * The External Symbol Naming Scheme of GNAT::
22504 * Converting Ada Files to html with gnathtml::
22505 * Installing gnathtml::
22512 @node Using Other Utility Programs with GNAT
22513 @section Using Other Utility Programs with GNAT
22516 The object files generated by GNAT are in standard system format and in
22517 particular the debugging information uses this format. This means
22518 programs generated by GNAT can be used with existing utilities that
22519 depend on these formats.
22522 In general, any utility program that works with C will also often work with
22523 Ada programs generated by GNAT. This includes software utilities such as
22524 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22528 @node The External Symbol Naming Scheme of GNAT
22529 @section The External Symbol Naming Scheme of GNAT
22532 In order to interpret the output from GNAT, when using tools that are
22533 originally intended for use with other languages, it is useful to
22534 understand the conventions used to generate link names from the Ada
22537 All link names are in all lowercase letters. With the exception of library
22538 procedure names, the mechanism used is simply to use the full expanded
22539 Ada name with dots replaced by double underscores. For example, suppose
22540 we have the following package spec:
22542 @smallexample @c ada
22553 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22554 the corresponding link name is @code{qrs__mn}.
22556 Of course if a @code{pragma Export} is used this may be overridden:
22558 @smallexample @c ada
22563 pragma Export (Var1, C, External_Name => "var1_name");
22565 pragma Export (Var2, C, Link_Name => "var2_link_name");
22572 In this case, the link name for @var{Var1} is whatever link name the
22573 C compiler would assign for the C function @var{var1_name}. This typically
22574 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22575 system conventions, but other possibilities exist. The link name for
22576 @var{Var2} is @var{var2_link_name}, and this is not operating system
22580 One exception occurs for library level procedures. A potential ambiguity
22581 arises between the required name @code{_main} for the C main program,
22582 and the name we would otherwise assign to an Ada library level procedure
22583 called @code{Main} (which might well not be the main program).
22585 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22586 names. So if we have a library level procedure such as
22588 @smallexample @c ada
22591 procedure Hello (S : String);
22597 the external name of this procedure will be @var{_ada_hello}.
22600 @node Converting Ada Files to html with gnathtml
22601 @section Converting Ada Files to HTML with @code{gnathtml}
22604 This @code{Perl} script allows Ada source files to be browsed using
22605 standard Web browsers. For installation procedure, see the section
22606 @xref{Installing gnathtml}.
22608 Ada reserved keywords are highlighted in a bold font and Ada comments in
22609 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22610 switch to suppress the generation of cross-referencing information, user
22611 defined variables and types will appear in a different color; you will
22612 be able to click on any identifier and go to its declaration.
22614 The command line is as follow:
22616 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
22620 You can pass it as many Ada files as you want. @code{gnathtml} will generate
22621 an html file for every ada file, and a global file called @file{index.htm}.
22622 This file is an index of every identifier defined in the files.
22624 The available ^switches^options^ are the following ones:
22628 @cindex @option{-83} (@code{gnathtml})
22629 Only the Ada 83 subset of keywords will be highlighted.
22631 @item -cc @var{color}
22632 @cindex @option{-cc} (@code{gnathtml})
22633 This option allows you to change the color used for comments. The default
22634 value is green. The color argument can be any name accepted by html.
22637 @cindex @option{-d} (@code{gnathtml})
22638 If the Ada files depend on some other files (for instance through
22639 @code{with} clauses, the latter files will also be converted to html.
22640 Only the files in the user project will be converted to html, not the files
22641 in the run-time library itself.
22644 @cindex @option{-D} (@code{gnathtml})
22645 This command is the same as @option{-d} above, but @command{gnathtml} will
22646 also look for files in the run-time library, and generate html files for them.
22648 @item -ext @var{extension}
22649 @cindex @option{-ext} (@code{gnathtml})
22650 This option allows you to change the extension of the generated HTML files.
22651 If you do not specify an extension, it will default to @file{htm}.
22654 @cindex @option{-f} (@code{gnathtml})
22655 By default, gnathtml will generate html links only for global entities
22656 ('with'ed units, global variables and types,@dots{}). If you specify
22657 @option{-f} on the command line, then links will be generated for local
22660 @item -l @var{number}
22661 @cindex @option{-l} (@code{gnathtml})
22662 If this ^switch^option^ is provided and @var{number} is not 0, then
22663 @code{gnathtml} will number the html files every @var{number} line.
22666 @cindex @option{-I} (@code{gnathtml})
22667 Specify a directory to search for library files (@file{.ALI} files) and
22668 source files. You can provide several -I switches on the command line,
22669 and the directories will be parsed in the order of the command line.
22672 @cindex @option{-o} (@code{gnathtml})
22673 Specify the output directory for html files. By default, gnathtml will
22674 saved the generated html files in a subdirectory named @file{html/}.
22676 @item -p @var{file}
22677 @cindex @option{-p} (@code{gnathtml})
22678 If you are using Emacs and the most recent Emacs Ada mode, which provides
22679 a full Integrated Development Environment for compiling, checking,
22680 running and debugging applications, you may use @file{.gpr} files
22681 to give the directories where Emacs can find sources and object files.
22683 Using this ^switch^option^, you can tell gnathtml to use these files.
22684 This allows you to get an html version of your application, even if it
22685 is spread over multiple directories.
22687 @item -sc @var{color}
22688 @cindex @option{-sc} (@code{gnathtml})
22689 This ^switch^option^ allows you to change the color used for symbol
22691 The default value is red. The color argument can be any name accepted by html.
22693 @item -t @var{file}
22694 @cindex @option{-t} (@code{gnathtml})
22695 This ^switch^option^ provides the name of a file. This file contains a list of
22696 file names to be converted, and the effect is exactly as though they had
22697 appeared explicitly on the command line. This
22698 is the recommended way to work around the command line length limit on some
22703 @node Installing gnathtml
22704 @section Installing @code{gnathtml}
22707 @code{Perl} needs to be installed on your machine to run this script.
22708 @code{Perl} is freely available for almost every architecture and
22709 Operating System via the Internet.
22711 On Unix systems, you may want to modify the first line of the script
22712 @code{gnathtml}, to explicitly tell the Operating system where Perl
22713 is. The syntax of this line is:
22715 #!full_path_name_to_perl
22719 Alternatively, you may run the script using the following command line:
22722 $ perl gnathtml.pl @ovar{switches} @var{files}
22731 The GNAT distribution provides an Ada 95 template for the HP Language
22732 Sensitive Editor (LSE), a component of DECset. In order to
22733 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
22740 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
22741 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
22742 the collection phase with the /DEBUG qualifier.
22745 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
22746 $ DEFINE LIB$DEBUG PCA$COLLECTOR
22747 $ RUN/DEBUG <PROGRAM_NAME>
22753 @c ******************************
22754 @node Code Coverage and Profiling
22755 @chapter Code Coverage and Profiling
22756 @cindex Code Coverage
22760 This chapter describes how to use @code{gcov} - coverage testing tool - and
22761 @code{gprof} - profiler tool - on your Ada programs.
22764 * Code Coverage of Ada Programs using gcov::
22765 * Profiling an Ada Program using gprof::
22768 @node Code Coverage of Ada Programs using gcov
22769 @section Code Coverage of Ada Programs using gcov
22771 @cindex -fprofile-arcs
22772 @cindex -ftest-coverage
22774 @cindex Code Coverage
22777 @code{gcov} is a test coverage program: it analyzes the execution of a given
22778 program on selected tests, to help you determine the portions of the program
22779 that are still untested.
22781 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
22782 User's Guide. You can refer to this documentation for a more complete
22785 This chapter provides a quick startup guide, and
22786 details some Gnat-specific features.
22789 * Quick startup guide::
22793 @node Quick startup guide
22794 @subsection Quick startup guide
22796 In order to perform coverage analysis of a program using @code{gcov}, 3
22801 Code instrumentation during the compilation process
22803 Execution of the instrumented program
22805 Execution of the @code{gcov} tool to generate the result.
22808 The code instrumentation needed by gcov is created at the object level:
22809 The source code is not modified in any way, because the instrumentation code is
22810 inserted by gcc during the compilation process. To compile your code with code
22811 coverage activated, you need to recompile your whole project using the
22813 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
22814 @code{-fprofile-arcs}.
22817 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
22818 -largs -fprofile-arcs
22821 This compilation process will create @file{.gcno} files together with
22822 the usual object files.
22824 Once the program is compiled with coverage instrumentation, you can
22825 run it as many times as needed - on portions of a test suite for
22826 example. The first execution will produce @file{.gcda} files at the
22827 same location as the @file{.gcno} files. The following executions
22828 will update those files, so that a cumulative result of the covered
22829 portions of the program is generated.
22831 Finally, you need to call the @code{gcov} tool. The different options of
22832 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
22834 This will create annotated source files with a @file{.gcov} extension:
22835 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
22837 @node Gnat specifics
22838 @subsection Gnat specifics
22840 Because Ada semantics, portions of the source code may be shared among
22841 several object files. This is the case for example when generics are
22842 involved, when inlining is active or when declarations generate initialisation
22843 calls. In order to take
22844 into account this shared code, you need to call @code{gcov} on all
22845 source files of the tested program at once.
22847 The list of source files might exceed the system's maximum command line
22848 length. In order to bypass this limitation, a new mechanism has been
22849 implemented in @code{gcov}: you can now list all your project's files into a
22850 text file, and provide this file to gcov as a parameter, preceded by a @@
22851 (e.g. @samp{gcov @@mysrclist.txt}).
22853 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
22854 not supported as there can be unresolved symbols during the final link.
22856 @node Profiling an Ada Program using gprof
22857 @section Profiling an Ada Program using gprof
22863 This section is not meant to be an exhaustive documentation of @code{gprof}.
22864 Full documentation for it can be found in the GNU Profiler User's Guide
22865 documentation that is part of this GNAT distribution.
22867 Profiling a program helps determine the parts of a program that are executed
22868 most often, and are therefore the most time-consuming.
22870 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
22871 better handle Ada programs and multitasking.
22872 It is currently supported on the following platforms
22877 solaris sparc/sparc64/x86
22883 In order to profile a program using @code{gprof}, 3 steps are needed:
22887 Code instrumentation, requiring a full recompilation of the project with the
22890 Execution of the program under the analysis conditions, i.e. with the desired
22893 Analysis of the results using the @code{gprof} tool.
22897 The following sections detail the different steps, and indicate how
22898 to interpret the results:
22900 * Compilation for profiling::
22901 * Program execution::
22903 * Interpretation of profiling results::
22906 @node Compilation for profiling
22907 @subsection Compilation for profiling
22911 In order to profile a program the first step is to tell the compiler
22912 to generate the necessary profiling information. The compiler switch to be used
22913 is @code{-pg}, which must be added to other compilation switches. This
22914 switch needs to be specified both during compilation and link stages, and can
22915 be specified once when using gnatmake:
22918 gnatmake -f -pg -P my_project
22922 Note that only the objects that were compiled with the @samp{-pg} switch will be
22923 profiled; if you need to profile your whole project, use the
22924 @samp{-f} gnatmake switch to force full recompilation.
22926 @node Program execution
22927 @subsection Program execution
22930 Once the program has been compiled for profiling, you can run it as usual.
22932 The only constraint imposed by profiling is that the program must terminate
22933 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
22936 Once the program completes execution, a data file called @file{gmon.out} is
22937 generated in the directory where the program was launched from. If this file
22938 already exists, it will be overwritten.
22940 @node Running gprof
22941 @subsection Running gprof
22944 The @code{gprof} tool is called as follow:
22947 gprof my_prog gmon.out
22958 The complete form of the gprof command line is the following:
22961 gprof [^switches^options^] [executable [data-file]]
22965 @code{gprof} supports numerous ^switch^options^. The order of these
22966 ^switch^options^ does not matter. The full list of options can be found in
22967 the GNU Profiler User's Guide documentation that comes with this documentation.
22969 The following is the subset of those switches that is most relevant:
22973 @item --demangle[=@var{style}]
22974 @itemx --no-demangle
22975 @cindex @option{--demangle} (@code{gprof})
22976 These options control whether symbol names should be demangled when
22977 printing output. The default is to demangle C++ symbols. The
22978 @code{--no-demangle} option may be used to turn off demangling. Different
22979 compilers have different mangling styles. The optional demangling style
22980 argument can be used to choose an appropriate demangling style for your
22981 compiler, in particular Ada symbols generated by GNAT can be demangled using
22982 @code{--demangle=gnat}.
22984 @item -e @var{function_name}
22985 @cindex @option{-e} (@code{gprof})
22986 The @samp{-e @var{function}} option tells @code{gprof} not to print
22987 information about the function @var{function_name} (and its
22988 children@dots{}) in the call graph. The function will still be listed
22989 as a child of any functions that call it, but its index number will be
22990 shown as @samp{[not printed]}. More than one @samp{-e} option may be
22991 given; only one @var{function_name} may be indicated with each @samp{-e}
22994 @item -E @var{function_name}
22995 @cindex @option{-E} (@code{gprof})
22996 The @code{-E @var{function}} option works like the @code{-e} option, but
22997 execution time spent in the function (and children who were not called from
22998 anywhere else), will not be used to compute the percentages-of-time for
22999 the call graph. More than one @samp{-E} option may be given; only one
23000 @var{function_name} may be indicated with each @samp{-E} option.
23002 @item -f @var{function_name}
23003 @cindex @option{-f} (@code{gprof})
23004 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23005 call graph to the function @var{function_name} and its children (and
23006 their children@dots{}). More than one @samp{-f} option may be given;
23007 only one @var{function_name} may be indicated with each @samp{-f}
23010 @item -F @var{function_name}
23011 @cindex @option{-F} (@code{gprof})
23012 The @samp{-F @var{function}} option works like the @code{-f} option, but
23013 only time spent in the function and its children (and their
23014 children@dots{}) will be used to determine total-time and
23015 percentages-of-time for the call graph. More than one @samp{-F} option
23016 may be given; only one @var{function_name} may be indicated with each
23017 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23021 @node Interpretation of profiling results
23022 @subsection Interpretation of profiling results
23026 The results of the profiling analysis are represented by two arrays: the
23027 'flat profile' and the 'call graph'. Full documentation of those outputs
23028 can be found in the GNU Profiler User's Guide.
23030 The flat profile shows the time spent in each function of the program, and how
23031 many time it has been called. This allows you to locate easily the most
23032 time-consuming functions.
23034 The call graph shows, for each subprogram, the subprograms that call it,
23035 and the subprograms that it calls. It also provides an estimate of the time
23036 spent in each of those callers/called subprograms.
23039 @c ******************************
23040 @node Running and Debugging Ada Programs
23041 @chapter Running and Debugging Ada Programs
23045 This chapter discusses how to debug Ada programs.
23047 It applies to GNAT on the Alpha OpenVMS platform;
23048 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23049 since HP has implemented Ada support in the OpenVMS debugger on I64.
23052 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23056 The illegality may be a violation of the static semantics of Ada. In
23057 that case GNAT diagnoses the constructs in the program that are illegal.
23058 It is then a straightforward matter for the user to modify those parts of
23062 The illegality may be a violation of the dynamic semantics of Ada. In
23063 that case the program compiles and executes, but may generate incorrect
23064 results, or may terminate abnormally with some exception.
23067 When presented with a program that contains convoluted errors, GNAT
23068 itself may terminate abnormally without providing full diagnostics on
23069 the incorrect user program.
23073 * The GNAT Debugger GDB::
23075 * Introduction to GDB Commands::
23076 * Using Ada Expressions::
23077 * Calling User-Defined Subprograms::
23078 * Using the Next Command in a Function::
23081 * Debugging Generic Units::
23082 * GNAT Abnormal Termination or Failure to Terminate::
23083 * Naming Conventions for GNAT Source Files::
23084 * Getting Internal Debugging Information::
23085 * Stack Traceback::
23091 @node The GNAT Debugger GDB
23092 @section The GNAT Debugger GDB
23095 @code{GDB} is a general purpose, platform-independent debugger that
23096 can be used to debug mixed-language programs compiled with @command{gcc},
23097 and in particular is capable of debugging Ada programs compiled with
23098 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23099 complex Ada data structures.
23101 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23103 located in the GNU:[DOCS] directory,
23105 for full details on the usage of @code{GDB}, including a section on
23106 its usage on programs. This manual should be consulted for full
23107 details. The section that follows is a brief introduction to the
23108 philosophy and use of @code{GDB}.
23110 When GNAT programs are compiled, the compiler optionally writes debugging
23111 information into the generated object file, including information on
23112 line numbers, and on declared types and variables. This information is
23113 separate from the generated code. It makes the object files considerably
23114 larger, but it does not add to the size of the actual executable that
23115 will be loaded into memory, and has no impact on run-time performance. The
23116 generation of debug information is triggered by the use of the
23117 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23118 used to carry out the compilations. It is important to emphasize that
23119 the use of these options does not change the generated code.
23121 The debugging information is written in standard system formats that
23122 are used by many tools, including debuggers and profilers. The format
23123 of the information is typically designed to describe C types and
23124 semantics, but GNAT implements a translation scheme which allows full
23125 details about Ada types and variables to be encoded into these
23126 standard C formats. Details of this encoding scheme may be found in
23127 the file exp_dbug.ads in the GNAT source distribution. However, the
23128 details of this encoding are, in general, of no interest to a user,
23129 since @code{GDB} automatically performs the necessary decoding.
23131 When a program is bound and linked, the debugging information is
23132 collected from the object files, and stored in the executable image of
23133 the program. Again, this process significantly increases the size of
23134 the generated executable file, but it does not increase the size of
23135 the executable program itself. Furthermore, if this program is run in
23136 the normal manner, it runs exactly as if the debug information were
23137 not present, and takes no more actual memory.
23139 However, if the program is run under control of @code{GDB}, the
23140 debugger is activated. The image of the program is loaded, at which
23141 point it is ready to run. If a run command is given, then the program
23142 will run exactly as it would have if @code{GDB} were not present. This
23143 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23144 entirely non-intrusive until a breakpoint is encountered. If no
23145 breakpoint is ever hit, the program will run exactly as it would if no
23146 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23147 the debugging information and can respond to user commands to inspect
23148 variables, and more generally to report on the state of execution.
23152 @section Running GDB
23155 This section describes how to initiate the debugger.
23156 @c The above sentence is really just filler, but it was otherwise
23157 @c clumsy to get the first paragraph nonindented given the conditional
23158 @c nature of the description
23161 The debugger can be launched from a @code{GPS} menu or
23162 directly from the command line. The description below covers the latter use.
23163 All the commands shown can be used in the @code{GPS} debug console window,
23164 but there are usually more GUI-based ways to achieve the same effect.
23167 The command to run @code{GDB} is
23170 $ ^gdb program^GDB PROGRAM^
23174 where @code{^program^PROGRAM^} is the name of the executable file. This
23175 activates the debugger and results in a prompt for debugger commands.
23176 The simplest command is simply @code{run}, which causes the program to run
23177 exactly as if the debugger were not present. The following section
23178 describes some of the additional commands that can be given to @code{GDB}.
23180 @c *******************************
23181 @node Introduction to GDB Commands
23182 @section Introduction to GDB Commands
23185 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23186 Debugging with GDB, gdb, Debugging with GDB},
23188 located in the GNU:[DOCS] directory,
23190 for extensive documentation on the use
23191 of these commands, together with examples of their use. Furthermore,
23192 the command @command{help} invoked from within GDB activates a simple help
23193 facility which summarizes the available commands and their options.
23194 In this section we summarize a few of the most commonly
23195 used commands to give an idea of what @code{GDB} is about. You should create
23196 a simple program with debugging information and experiment with the use of
23197 these @code{GDB} commands on the program as you read through the
23201 @item set args @var{arguments}
23202 The @var{arguments} list above is a list of arguments to be passed to
23203 the program on a subsequent run command, just as though the arguments
23204 had been entered on a normal invocation of the program. The @code{set args}
23205 command is not needed if the program does not require arguments.
23208 The @code{run} command causes execution of the program to start from
23209 the beginning. If the program is already running, that is to say if
23210 you are currently positioned at a breakpoint, then a prompt will ask
23211 for confirmation that you want to abandon the current execution and
23214 @item breakpoint @var{location}
23215 The breakpoint command sets a breakpoint, that is to say a point at which
23216 execution will halt and @code{GDB} will await further
23217 commands. @var{location} is
23218 either a line number within a file, given in the format @code{file:linenumber},
23219 or it is the name of a subprogram. If you request that a breakpoint be set on
23220 a subprogram that is overloaded, a prompt will ask you to specify on which of
23221 those subprograms you want to breakpoint. You can also
23222 specify that all of them should be breakpointed. If the program is run
23223 and execution encounters the breakpoint, then the program
23224 stops and @code{GDB} signals that the breakpoint was encountered by
23225 printing the line of code before which the program is halted.
23227 @item breakpoint exception @var{name}
23228 A special form of the breakpoint command which breakpoints whenever
23229 exception @var{name} is raised.
23230 If @var{name} is omitted,
23231 then a breakpoint will occur when any exception is raised.
23233 @item print @var{expression}
23234 This will print the value of the given expression. Most simple
23235 Ada expression formats are properly handled by @code{GDB}, so the expression
23236 can contain function calls, variables, operators, and attribute references.
23239 Continues execution following a breakpoint, until the next breakpoint or the
23240 termination of the program.
23243 Executes a single line after a breakpoint. If the next statement
23244 is a subprogram call, execution continues into (the first statement of)
23245 the called subprogram.
23248 Executes a single line. If this line is a subprogram call, executes and
23249 returns from the call.
23252 Lists a few lines around the current source location. In practice, it
23253 is usually more convenient to have a separate edit window open with the
23254 relevant source file displayed. Successive applications of this command
23255 print subsequent lines. The command can be given an argument which is a
23256 line number, in which case it displays a few lines around the specified one.
23259 Displays a backtrace of the call chain. This command is typically
23260 used after a breakpoint has occurred, to examine the sequence of calls that
23261 leads to the current breakpoint. The display includes one line for each
23262 activation record (frame) corresponding to an active subprogram.
23265 At a breakpoint, @code{GDB} can display the values of variables local
23266 to the current frame. The command @code{up} can be used to
23267 examine the contents of other active frames, by moving the focus up
23268 the stack, that is to say from callee to caller, one frame at a time.
23271 Moves the focus of @code{GDB} down from the frame currently being
23272 examined to the frame of its callee (the reverse of the previous command),
23274 @item frame @var{n}
23275 Inspect the frame with the given number. The value 0 denotes the frame
23276 of the current breakpoint, that is to say the top of the call stack.
23281 The above list is a very short introduction to the commands that
23282 @code{GDB} provides. Important additional capabilities, including conditional
23283 breakpoints, the ability to execute command sequences on a breakpoint,
23284 the ability to debug at the machine instruction level and many other
23285 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
23286 Debugging with GDB}. Note that most commands can be abbreviated
23287 (for example, c for continue, bt for backtrace).
23289 @node Using Ada Expressions
23290 @section Using Ada Expressions
23291 @cindex Ada expressions
23294 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23295 extensions. The philosophy behind the design of this subset is
23299 That @code{GDB} should provide basic literals and access to operations for
23300 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23301 leaving more sophisticated computations to subprograms written into the
23302 program (which therefore may be called from @code{GDB}).
23305 That type safety and strict adherence to Ada language restrictions
23306 are not particularly important to the @code{GDB} user.
23309 That brevity is important to the @code{GDB} user.
23313 Thus, for brevity, the debugger acts as if there were
23314 implicit @code{with} and @code{use} clauses in effect for all user-written
23315 packages, thus making it unnecessary to fully qualify most names with
23316 their packages, regardless of context. Where this causes ambiguity,
23317 @code{GDB} asks the user's intent.
23319 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23320 GDB, gdb, Debugging with GDB}.
23322 @node Calling User-Defined Subprograms
23323 @section Calling User-Defined Subprograms
23326 An important capability of @code{GDB} is the ability to call user-defined
23327 subprograms while debugging. This is achieved simply by entering
23328 a subprogram call statement in the form:
23331 call subprogram-name (parameters)
23335 The keyword @code{call} can be omitted in the normal case where the
23336 @code{subprogram-name} does not coincide with any of the predefined
23337 @code{GDB} commands.
23339 The effect is to invoke the given subprogram, passing it the
23340 list of parameters that is supplied. The parameters can be expressions and
23341 can include variables from the program being debugged. The
23342 subprogram must be defined
23343 at the library level within your program, and @code{GDB} will call the
23344 subprogram within the environment of your program execution (which
23345 means that the subprogram is free to access or even modify variables
23346 within your program).
23348 The most important use of this facility is in allowing the inclusion of
23349 debugging routines that are tailored to particular data structures
23350 in your program. Such debugging routines can be written to provide a suitably
23351 high-level description of an abstract type, rather than a low-level dump
23352 of its physical layout. After all, the standard
23353 @code{GDB print} command only knows the physical layout of your
23354 types, not their abstract meaning. Debugging routines can provide information
23355 at the desired semantic level and are thus enormously useful.
23357 For example, when debugging GNAT itself, it is crucial to have access to
23358 the contents of the tree nodes used to represent the program internally.
23359 But tree nodes are represented simply by an integer value (which in turn
23360 is an index into a table of nodes).
23361 Using the @code{print} command on a tree node would simply print this integer
23362 value, which is not very useful. But the PN routine (defined in file
23363 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23364 a useful high level representation of the tree node, which includes the
23365 syntactic category of the node, its position in the source, the integers
23366 that denote descendant nodes and parent node, as well as varied
23367 semantic information. To study this example in more detail, you might want to
23368 look at the body of the PN procedure in the stated file.
23370 @node Using the Next Command in a Function
23371 @section Using the Next Command in a Function
23374 When you use the @code{next} command in a function, the current source
23375 location will advance to the next statement as usual. A special case
23376 arises in the case of a @code{return} statement.
23378 Part of the code for a return statement is the ``epilog'' of the function.
23379 This is the code that returns to the caller. There is only one copy of
23380 this epilog code, and it is typically associated with the last return
23381 statement in the function if there is more than one return. In some
23382 implementations, this epilog is associated with the first statement
23385 The result is that if you use the @code{next} command from a return
23386 statement that is not the last return statement of the function you
23387 may see a strange apparent jump to the last return statement or to
23388 the start of the function. You should simply ignore this odd jump.
23389 The value returned is always that from the first return statement
23390 that was stepped through.
23392 @node Ada Exceptions
23393 @section Breaking on Ada Exceptions
23397 You can set breakpoints that trip when your program raises
23398 selected exceptions.
23401 @item break exception
23402 Set a breakpoint that trips whenever (any task in the) program raises
23405 @item break exception @var{name}
23406 Set a breakpoint that trips whenever (any task in the) program raises
23407 the exception @var{name}.
23409 @item break exception unhandled
23410 Set a breakpoint that trips whenever (any task in the) program raises an
23411 exception for which there is no handler.
23413 @item info exceptions
23414 @itemx info exceptions @var{regexp}
23415 The @code{info exceptions} command permits the user to examine all defined
23416 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23417 argument, prints out only those exceptions whose name matches @var{regexp}.
23425 @code{GDB} allows the following task-related commands:
23429 This command shows a list of current Ada tasks, as in the following example:
23436 ID TID P-ID Thread Pri State Name
23437 1 8088000 0 807e000 15 Child Activation Wait main_task
23438 2 80a4000 1 80ae000 15 Accept/Select Wait b
23439 3 809a800 1 80a4800 15 Child Activation Wait a
23440 * 4 80ae800 3 80b8000 15 Running c
23444 In this listing, the asterisk before the first task indicates it to be the
23445 currently running task. The first column lists the task ID that is used
23446 to refer to tasks in the following commands.
23448 @item break @var{linespec} task @var{taskid}
23449 @itemx break @var{linespec} task @var{taskid} if @dots{}
23450 @cindex Breakpoints and tasks
23451 These commands are like the @code{break @dots{} thread @dots{}}.
23452 @var{linespec} specifies source lines.
23454 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23455 to specify that you only want @code{GDB} to stop the program when a
23456 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23457 numeric task identifiers assigned by @code{GDB}, shown in the first
23458 column of the @samp{info tasks} display.
23460 If you do not specify @samp{task @var{taskid}} when you set a
23461 breakpoint, the breakpoint applies to @emph{all} tasks of your
23464 You can use the @code{task} qualifier on conditional breakpoints as
23465 well; in this case, place @samp{task @var{taskid}} before the
23466 breakpoint condition (before the @code{if}).
23468 @item task @var{taskno}
23469 @cindex Task switching
23471 This command allows to switch to the task referred by @var{taskno}. In
23472 particular, This allows to browse the backtrace of the specified
23473 task. It is advised to switch back to the original task before
23474 continuing execution otherwise the scheduling of the program may be
23479 For more detailed information on the tasking support,
23480 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23482 @node Debugging Generic Units
23483 @section Debugging Generic Units
23484 @cindex Debugging Generic Units
23488 GNAT always uses code expansion for generic instantiation. This means that
23489 each time an instantiation occurs, a complete copy of the original code is
23490 made, with appropriate substitutions of formals by actuals.
23492 It is not possible to refer to the original generic entities in
23493 @code{GDB}, but it is always possible to debug a particular instance of
23494 a generic, by using the appropriate expanded names. For example, if we have
23496 @smallexample @c ada
23501 generic package k is
23502 procedure kp (v1 : in out integer);
23506 procedure kp (v1 : in out integer) is
23512 package k1 is new k;
23513 package k2 is new k;
23515 var : integer := 1;
23528 Then to break on a call to procedure kp in the k2 instance, simply
23532 (gdb) break g.k2.kp
23536 When the breakpoint occurs, you can step through the code of the
23537 instance in the normal manner and examine the values of local variables, as for
23540 @node GNAT Abnormal Termination or Failure to Terminate
23541 @section GNAT Abnormal Termination or Failure to Terminate
23542 @cindex GNAT Abnormal Termination or Failure to Terminate
23545 When presented with programs that contain serious errors in syntax
23547 GNAT may on rare occasions experience problems in operation, such
23549 segmentation fault or illegal memory access, raising an internal
23550 exception, terminating abnormally, or failing to terminate at all.
23551 In such cases, you can activate
23552 various features of GNAT that can help you pinpoint the construct in your
23553 program that is the likely source of the problem.
23555 The following strategies are presented in increasing order of
23556 difficulty, corresponding to your experience in using GNAT and your
23557 familiarity with compiler internals.
23561 Run @command{gcc} with the @option{-gnatf}. This first
23562 switch causes all errors on a given line to be reported. In its absence,
23563 only the first error on a line is displayed.
23565 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23566 are encountered, rather than after compilation is terminated. If GNAT
23567 terminates prematurely or goes into an infinite loop, the last error
23568 message displayed may help to pinpoint the culprit.
23571 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23572 mode, @command{gcc} produces ongoing information about the progress of the
23573 compilation and provides the name of each procedure as code is
23574 generated. This switch allows you to find which Ada procedure was being
23575 compiled when it encountered a code generation problem.
23578 @cindex @option{-gnatdc} switch
23579 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23580 switch that does for the front-end what @option{^-v^VERBOSE^} does
23581 for the back end. The system prints the name of each unit,
23582 either a compilation unit or nested unit, as it is being analyzed.
23584 Finally, you can start
23585 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23586 front-end of GNAT, and can be run independently (normally it is just
23587 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23588 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23589 @code{where} command is the first line of attack; the variable
23590 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23591 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23592 which the execution stopped, and @code{input_file name} indicates the name of
23596 @node Naming Conventions for GNAT Source Files
23597 @section Naming Conventions for GNAT Source Files
23600 In order to examine the workings of the GNAT system, the following
23601 brief description of its organization may be helpful:
23605 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23608 All files prefixed with @file{^par^PAR^} are components of the parser. The
23609 numbers correspond to chapters of the Ada Reference Manual. For example,
23610 parsing of select statements can be found in @file{par-ch9.adb}.
23613 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23614 numbers correspond to chapters of the Ada standard. For example, all
23615 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23616 addition, some features of the language require sufficient special processing
23617 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
23618 dynamic dispatching, etc.
23621 All files prefixed with @file{^exp^EXP^} perform normalization and
23622 expansion of the intermediate representation (abstract syntax tree, or AST).
23623 these files use the same numbering scheme as the parser and semantics files.
23624 For example, the construction of record initialization procedures is done in
23625 @file{exp_ch3.adb}.
23628 The files prefixed with @file{^bind^BIND^} implement the binder, which
23629 verifies the consistency of the compilation, determines an order of
23630 elaboration, and generates the bind file.
23633 The files @file{atree.ads} and @file{atree.adb} detail the low-level
23634 data structures used by the front-end.
23637 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
23638 the abstract syntax tree as produced by the parser.
23641 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
23642 all entities, computed during semantic analysis.
23645 Library management issues are dealt with in files with prefix
23651 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
23652 defined in Annex A.
23657 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
23658 defined in Annex B.
23662 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
23663 both language-defined children and GNAT run-time routines.
23667 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
23668 general-purpose packages, fully documented in their specs. All
23669 the other @file{.c} files are modifications of common @command{gcc} files.
23672 @node Getting Internal Debugging Information
23673 @section Getting Internal Debugging Information
23676 Most compilers have internal debugging switches and modes. GNAT
23677 does also, except GNAT internal debugging switches and modes are not
23678 secret. A summary and full description of all the compiler and binder
23679 debug flags are in the file @file{debug.adb}. You must obtain the
23680 sources of the compiler to see the full detailed effects of these flags.
23682 The switches that print the source of the program (reconstructed from
23683 the internal tree) are of general interest for user programs, as are the
23685 the full internal tree, and the entity table (the symbol table
23686 information). The reconstructed source provides a readable version of the
23687 program after the front-end has completed analysis and expansion,
23688 and is useful when studying the performance of specific constructs.
23689 For example, constraint checks are indicated, complex aggregates
23690 are replaced with loops and assignments, and tasking primitives
23691 are replaced with run-time calls.
23693 @node Stack Traceback
23694 @section Stack Traceback
23696 @cindex stack traceback
23697 @cindex stack unwinding
23700 Traceback is a mechanism to display the sequence of subprogram calls that
23701 leads to a specified execution point in a program. Often (but not always)
23702 the execution point is an instruction at which an exception has been raised.
23703 This mechanism is also known as @i{stack unwinding} because it obtains
23704 its information by scanning the run-time stack and recovering the activation
23705 records of all active subprograms. Stack unwinding is one of the most
23706 important tools for program debugging.
23708 The first entry stored in traceback corresponds to the deepest calling level,
23709 that is to say the subprogram currently executing the instruction
23710 from which we want to obtain the traceback.
23712 Note that there is no runtime performance penalty when stack traceback
23713 is enabled, and no exception is raised during program execution.
23716 * Non-Symbolic Traceback::
23717 * Symbolic Traceback::
23720 @node Non-Symbolic Traceback
23721 @subsection Non-Symbolic Traceback
23722 @cindex traceback, non-symbolic
23725 Note: this feature is not supported on all platforms. See
23726 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
23730 * Tracebacks From an Unhandled Exception::
23731 * Tracebacks From Exception Occurrences (non-symbolic)::
23732 * Tracebacks From Anywhere in a Program (non-symbolic)::
23735 @node Tracebacks From an Unhandled Exception
23736 @subsubsection Tracebacks From an Unhandled Exception
23739 A runtime non-symbolic traceback is a list of addresses of call instructions.
23740 To enable this feature you must use the @option{-E}
23741 @code{gnatbind}'s option. With this option a stack traceback is stored as part
23742 of exception information. You can retrieve this information using the
23743 @code{addr2line} tool.
23745 Here is a simple example:
23747 @smallexample @c ada
23753 raise Constraint_Error;
23768 $ gnatmake stb -bargs -E
23771 Execution terminated by unhandled exception
23772 Exception name: CONSTRAINT_ERROR
23774 Call stack traceback locations:
23775 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23779 As we see the traceback lists a sequence of addresses for the unhandled
23780 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
23781 guess that this exception come from procedure P1. To translate these
23782 addresses into the source lines where the calls appear, the
23783 @code{addr2line} tool, described below, is invaluable. The use of this tool
23784 requires the program to be compiled with debug information.
23787 $ gnatmake -g stb -bargs -E
23790 Execution terminated by unhandled exception
23791 Exception name: CONSTRAINT_ERROR
23793 Call stack traceback locations:
23794 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23796 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
23797 0x4011f1 0x77e892a4
23799 00401373 at d:/stb/stb.adb:5
23800 0040138B at d:/stb/stb.adb:10
23801 0040139C at d:/stb/stb.adb:14
23802 00401335 at d:/stb/b~stb.adb:104
23803 004011C4 at /build/@dots{}/crt1.c:200
23804 004011F1 at /build/@dots{}/crt1.c:222
23805 77E892A4 in ?? at ??:0
23809 The @code{addr2line} tool has several other useful options:
23813 to get the function name corresponding to any location
23815 @item --demangle=gnat
23816 to use the gnat decoding mode for the function names. Note that
23817 for binutils version 2.9.x the option is simply @option{--demangle}.
23821 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
23822 0x40139c 0x401335 0x4011c4 0x4011f1
23824 00401373 in stb.p1 at d:/stb/stb.adb:5
23825 0040138B in stb.p2 at d:/stb/stb.adb:10
23826 0040139C in stb at d:/stb/stb.adb:14
23827 00401335 in main at d:/stb/b~stb.adb:104
23828 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
23829 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
23833 From this traceback we can see that the exception was raised in
23834 @file{stb.adb} at line 5, which was reached from a procedure call in
23835 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
23836 which contains the call to the main program.
23837 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
23838 and the output will vary from platform to platform.
23840 It is also possible to use @code{GDB} with these traceback addresses to debug
23841 the program. For example, we can break at a given code location, as reported
23842 in the stack traceback:
23848 Furthermore, this feature is not implemented inside Windows DLL. Only
23849 the non-symbolic traceback is reported in this case.
23852 (gdb) break *0x401373
23853 Breakpoint 1 at 0x401373: file stb.adb, line 5.
23857 It is important to note that the stack traceback addresses
23858 do not change when debug information is included. This is particularly useful
23859 because it makes it possible to release software without debug information (to
23860 minimize object size), get a field report that includes a stack traceback
23861 whenever an internal bug occurs, and then be able to retrieve the sequence
23862 of calls with the same program compiled with debug information.
23864 @node Tracebacks From Exception Occurrences (non-symbolic)
23865 @subsubsection Tracebacks From Exception Occurrences
23868 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
23869 The stack traceback is attached to the exception information string, and can
23870 be retrieved in an exception handler within the Ada program, by means of the
23871 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
23873 @smallexample @c ada
23875 with Ada.Exceptions;
23880 use Ada.Exceptions;
23888 Text_IO.Put_Line (Exception_Information (E));
23902 This program will output:
23907 Exception name: CONSTRAINT_ERROR
23908 Message: stb.adb:12
23909 Call stack traceback locations:
23910 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
23913 @node Tracebacks From Anywhere in a Program (non-symbolic)
23914 @subsubsection Tracebacks From Anywhere in a Program
23917 It is also possible to retrieve a stack traceback from anywhere in a
23918 program. For this you need to
23919 use the @code{GNAT.Traceback} API. This package includes a procedure called
23920 @code{Call_Chain} that computes a complete stack traceback, as well as useful
23921 display procedures described below. It is not necessary to use the
23922 @option{-E gnatbind} option in this case, because the stack traceback mechanism
23923 is invoked explicitly.
23926 In the following example we compute a traceback at a specific location in
23927 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
23928 convert addresses to strings:
23930 @smallexample @c ada
23932 with GNAT.Traceback;
23933 with GNAT.Debug_Utilities;
23939 use GNAT.Traceback;
23942 TB : Tracebacks_Array (1 .. 10);
23943 -- We are asking for a maximum of 10 stack frames.
23945 -- Len will receive the actual number of stack frames returned.
23947 Call_Chain (TB, Len);
23949 Text_IO.Put ("In STB.P1 : ");
23951 for K in 1 .. Len loop
23952 Text_IO.Put (Debug_Utilities.Image (TB (K)));
23973 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
23974 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
23978 You can then get further information by invoking the @code{addr2line}
23979 tool as described earlier (note that the hexadecimal addresses
23980 need to be specified in C format, with a leading ``0x'').
23982 @node Symbolic Traceback
23983 @subsection Symbolic Traceback
23984 @cindex traceback, symbolic
23987 A symbolic traceback is a stack traceback in which procedure names are
23988 associated with each code location.
23991 Note that this feature is not supported on all platforms. See
23992 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
23993 list of currently supported platforms.
23996 Note that the symbolic traceback requires that the program be compiled
23997 with debug information. If it is not compiled with debug information
23998 only the non-symbolic information will be valid.
24001 * Tracebacks From Exception Occurrences (symbolic)::
24002 * Tracebacks From Anywhere in a Program (symbolic)::
24005 @node Tracebacks From Exception Occurrences (symbolic)
24006 @subsubsection Tracebacks From Exception Occurrences
24008 @smallexample @c ada
24010 with GNAT.Traceback.Symbolic;
24016 raise Constraint_Error;
24033 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24038 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24041 0040149F in stb.p1 at stb.adb:8
24042 004014B7 in stb.p2 at stb.adb:13
24043 004014CF in stb.p3 at stb.adb:18
24044 004015DD in ada.stb at stb.adb:22
24045 00401461 in main at b~stb.adb:168
24046 004011C4 in __mingw_CRTStartup at crt1.c:200
24047 004011F1 in mainCRTStartup at crt1.c:222
24048 77E892A4 in ?? at ??:0
24052 In the above example the ``.\'' syntax in the @command{gnatmake} command
24053 is currently required by @command{addr2line} for files that are in
24054 the current working directory.
24055 Moreover, the exact sequence of linker options may vary from platform
24057 The above @option{-largs} section is for Windows platforms. By contrast,
24058 under Unix there is no need for the @option{-largs} section.
24059 Differences across platforms are due to details of linker implementation.
24061 @node Tracebacks From Anywhere in a Program (symbolic)
24062 @subsubsection Tracebacks From Anywhere in a Program
24065 It is possible to get a symbolic stack traceback
24066 from anywhere in a program, just as for non-symbolic tracebacks.
24067 The first step is to obtain a non-symbolic
24068 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24069 information. Here is an example:
24071 @smallexample @c ada
24073 with GNAT.Traceback;
24074 with GNAT.Traceback.Symbolic;
24079 use GNAT.Traceback;
24080 use GNAT.Traceback.Symbolic;
24083 TB : Tracebacks_Array (1 .. 10);
24084 -- We are asking for a maximum of 10 stack frames.
24086 -- Len will receive the actual number of stack frames returned.
24088 Call_Chain (TB, Len);
24089 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24102 @c ******************************
24104 @node Compatibility with HP Ada
24105 @chapter Compatibility with HP Ada
24106 @cindex Compatibility
24111 @cindex Compatibility between GNAT and HP Ada
24112 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24113 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24114 GNAT is highly compatible
24115 with HP Ada, and it should generally be straightforward to port code
24116 from the HP Ada environment to GNAT. However, there are a few language
24117 and implementation differences of which the user must be aware. These
24118 differences are discussed in this chapter. In
24119 addition, the operating environment and command structure for the
24120 compiler are different, and these differences are also discussed.
24122 For further details on these and other compatibility issues,
24123 see Appendix E of the HP publication
24124 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24126 Except where otherwise indicated, the description of GNAT for OpenVMS
24127 applies to both the Alpha and I64 platforms.
24129 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24130 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24132 The discussion in this chapter addresses specifically the implementation
24133 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24134 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24135 GNAT always follows the Alpha implementation.
24137 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24138 attributes are recognized, although only a subset of them can sensibly
24139 be implemented. The description of pragmas in
24140 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24141 indicates whether or not they are applicable to non-VMS systems.
24144 * Ada Language Compatibility::
24145 * Differences in the Definition of Package System::
24146 * Language-Related Features::
24147 * The Package STANDARD::
24148 * The Package SYSTEM::
24149 * Tasking and Task-Related Features::
24150 * Pragmas and Pragma-Related Features::
24151 * Library of Predefined Units::
24153 * Main Program Definition::
24154 * Implementation-Defined Attributes::
24155 * Compiler and Run-Time Interfacing::
24156 * Program Compilation and Library Management::
24158 * Implementation Limits::
24159 * Tools and Utilities::
24162 @node Ada Language Compatibility
24163 @section Ada Language Compatibility
24166 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24167 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24168 with Ada 83, and therefore Ada 83 programs will compile
24169 and run under GNAT with
24170 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24171 provides details on specific incompatibilities.
24173 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24174 as well as the pragma @code{ADA_83}, to force the compiler to
24175 operate in Ada 83 mode. This mode does not guarantee complete
24176 conformance to Ada 83, but in practice is sufficient to
24177 eliminate most sources of incompatibilities.
24178 In particular, it eliminates the recognition of the
24179 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24180 in Ada 83 programs is legal, and handles the cases of packages
24181 with optional bodies, and generics that instantiate unconstrained
24182 types without the use of @code{(<>)}.
24184 @node Differences in the Definition of Package System
24185 @section Differences in the Definition of Package @code{System}
24188 An Ada compiler is allowed to add
24189 implementation-dependent declarations to package @code{System}.
24191 GNAT does not take advantage of this permission, and the version of
24192 @code{System} provided by GNAT exactly matches that defined in the Ada
24195 However, HP Ada adds an extensive set of declarations to package
24197 as fully documented in the HP Ada manuals. To minimize changes required
24198 for programs that make use of these extensions, GNAT provides the pragma
24199 @code{Extend_System} for extending the definition of package System. By using:
24200 @cindex pragma @code{Extend_System}
24201 @cindex @code{Extend_System} pragma
24203 @smallexample @c ada
24206 pragma Extend_System (Aux_DEC);
24212 the set of definitions in @code{System} is extended to include those in
24213 package @code{System.Aux_DEC}.
24214 @cindex @code{System.Aux_DEC} package
24215 @cindex @code{Aux_DEC} package (child of @code{System})
24216 These definitions are incorporated directly into package @code{System},
24217 as though they had been declared there. For a
24218 list of the declarations added, see the spec of this package,
24219 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24220 @cindex @file{s-auxdec.ads} file
24221 The pragma @code{Extend_System} is a configuration pragma, which means that
24222 it can be placed in the file @file{gnat.adc}, so that it will automatically
24223 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24224 for further details.
24226 An alternative approach that avoids the use of the non-standard
24227 @code{Extend_System} pragma is to add a context clause to the unit that
24228 references these facilities:
24230 @smallexample @c ada
24232 with System.Aux_DEC;
24233 use System.Aux_DEC;
24238 The effect is not quite semantically identical to incorporating
24239 the declarations directly into package @code{System},
24240 but most programs will not notice a difference
24241 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24242 to reference the entities directly in package @code{System}.
24243 For units containing such references,
24244 the prefixes must either be removed, or the pragma @code{Extend_System}
24247 @node Language-Related Features
24248 @section Language-Related Features
24251 The following sections highlight differences in types,
24252 representations of types, operations, alignment, and
24256 * Integer Types and Representations::
24257 * Floating-Point Types and Representations::
24258 * Pragmas Float_Representation and Long_Float::
24259 * Fixed-Point Types and Representations::
24260 * Record and Array Component Alignment::
24261 * Address Clauses::
24262 * Other Representation Clauses::
24265 @node Integer Types and Representations
24266 @subsection Integer Types and Representations
24269 The set of predefined integer types is identical in HP Ada and GNAT.
24270 Furthermore the representation of these integer types is also identical,
24271 including the capability of size clauses forcing biased representation.
24274 HP Ada for OpenVMS Alpha systems has defined the
24275 following additional integer types in package @code{System}:
24292 @code{LARGEST_INTEGER}
24296 In GNAT, the first four of these types may be obtained from the
24297 standard Ada package @code{Interfaces}.
24298 Alternatively, by use of the pragma @code{Extend_System}, identical
24299 declarations can be referenced directly in package @code{System}.
24300 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24302 @node Floating-Point Types and Representations
24303 @subsection Floating-Point Types and Representations
24304 @cindex Floating-Point types
24307 The set of predefined floating-point types is identical in HP Ada and GNAT.
24308 Furthermore the representation of these floating-point
24309 types is also identical. One important difference is that the default
24310 representation for HP Ada is @code{VAX_Float}, but the default representation
24313 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24314 pragma @code{Float_Representation} as described in the HP Ada
24316 For example, the declarations:
24318 @smallexample @c ada
24320 type F_Float is digits 6;
24321 pragma Float_Representation (VAX_Float, F_Float);
24326 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24328 This set of declarations actually appears in @code{System.Aux_DEC},
24330 the full set of additional floating-point declarations provided in
24331 the HP Ada version of package @code{System}.
24332 This and similar declarations may be accessed in a user program
24333 by using pragma @code{Extend_System}. The use of this
24334 pragma, and the related pragma @code{Long_Float} is described in further
24335 detail in the following section.
24337 @node Pragmas Float_Representation and Long_Float
24338 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24341 HP Ada provides the pragma @code{Float_Representation}, which
24342 acts as a program library switch to allow control over
24343 the internal representation chosen for the predefined
24344 floating-point types declared in the package @code{Standard}.
24345 The format of this pragma is as follows:
24347 @smallexample @c ada
24349 pragma Float_Representation(VAX_Float | IEEE_Float);
24354 This pragma controls the representation of floating-point
24359 @code{VAX_Float} specifies that floating-point
24360 types are represented by default with the VAX system hardware types
24361 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24362 Note that the @code{H-floating}
24363 type was available only on VAX systems, and is not available
24364 in either HP Ada or GNAT.
24367 @code{IEEE_Float} specifies that floating-point
24368 types are represented by default with the IEEE single and
24369 double floating-point types.
24373 GNAT provides an identical implementation of the pragma
24374 @code{Float_Representation}, except that it functions as a
24375 configuration pragma. Note that the
24376 notion of configuration pragma corresponds closely to the
24377 HP Ada notion of a program library switch.
24379 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24381 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24382 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24383 advisable to change the format of numbers passed to standard library
24384 routines, and if necessary explicit type conversions may be needed.
24386 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24387 efficient, and (given that it conforms to an international standard)
24388 potentially more portable.
24389 The situation in which @code{VAX_Float} may be useful is in interfacing
24390 to existing code and data that expect the use of @code{VAX_Float}.
24391 In such a situation use the predefined @code{VAX_Float}
24392 types in package @code{System}, as extended by
24393 @code{Extend_System}. For example, use @code{System.F_Float}
24394 to specify the 32-bit @code{F-Float} format.
24397 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24398 to allow control over the internal representation chosen
24399 for the predefined type @code{Long_Float} and for floating-point
24400 type declarations with digits specified in the range 7 .. 15.
24401 The format of this pragma is as follows:
24403 @smallexample @c ada
24405 pragma Long_Float (D_FLOAT | G_FLOAT);
24409 @node Fixed-Point Types and Representations
24410 @subsection Fixed-Point Types and Representations
24413 On HP Ada for OpenVMS Alpha systems, rounding is
24414 away from zero for both positive and negative numbers.
24415 Therefore, @code{+0.5} rounds to @code{1},
24416 and @code{-0.5} rounds to @code{-1}.
24418 On GNAT the results of operations
24419 on fixed-point types are in accordance with the Ada
24420 rules. In particular, results of operations on decimal
24421 fixed-point types are truncated.
24423 @node Record and Array Component Alignment
24424 @subsection Record and Array Component Alignment
24427 On HP Ada for OpenVMS Alpha, all non-composite components
24428 are aligned on natural boundaries. For example, 1-byte
24429 components are aligned on byte boundaries, 2-byte
24430 components on 2-byte boundaries, 4-byte components on 4-byte
24431 byte boundaries, and so on. The OpenVMS Alpha hardware
24432 runs more efficiently with naturally aligned data.
24434 On GNAT, alignment rules are compatible
24435 with HP Ada for OpenVMS Alpha.
24437 @node Address Clauses
24438 @subsection Address Clauses
24441 In HP Ada and GNAT, address clauses are supported for
24442 objects and imported subprograms.
24443 The predefined type @code{System.Address} is a private type
24444 in both compilers on Alpha OpenVMS, with the same representation
24445 (it is simply a machine pointer). Addition, subtraction, and comparison
24446 operations are available in the standard Ada package
24447 @code{System.Storage_Elements}, or in package @code{System}
24448 if it is extended to include @code{System.Aux_DEC} using a
24449 pragma @code{Extend_System} as previously described.
24451 Note that code that @code{with}'s both this extended package @code{System}
24452 and the package @code{System.Storage_Elements} should not @code{use}
24453 both packages, or ambiguities will result. In general it is better
24454 not to mix these two sets of facilities. The Ada package was
24455 designed specifically to provide the kind of features that HP Ada
24456 adds directly to package @code{System}.
24458 The type @code{System.Address} is a 64-bit integer type in GNAT for
24459 I64 OpenVMS. For more information,
24460 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24462 GNAT is compatible with HP Ada in its handling of address
24463 clauses, except for some limitations in
24464 the form of address clauses for composite objects with
24465 initialization. Such address clauses are easily replaced
24466 by the use of an explicitly-defined constant as described
24467 in the Ada Reference Manual (13.1(22)). For example, the sequence
24470 @smallexample @c ada
24472 X, Y : Integer := Init_Func;
24473 Q : String (X .. Y) := "abc";
24475 for Q'Address use Compute_Address;
24480 will be rejected by GNAT, since the address cannot be computed at the time
24481 that @code{Q} is declared. To achieve the intended effect, write instead:
24483 @smallexample @c ada
24486 X, Y : Integer := Init_Func;
24487 Q_Address : constant Address := Compute_Address;
24488 Q : String (X .. Y) := "abc";
24490 for Q'Address use Q_Address;
24496 which will be accepted by GNAT (and other Ada compilers), and is also
24497 compatible with Ada 83. A fuller description of the restrictions
24498 on address specifications is found in @ref{Top, GNAT Reference Manual,
24499 About This Guide, gnat_rm, GNAT Reference Manual}.
24501 @node Other Representation Clauses
24502 @subsection Other Representation Clauses
24505 GNAT implements in a compatible manner all the representation
24506 clauses supported by HP Ada. In addition, GNAT
24507 implements the representation clause forms that were introduced in Ada 95,
24508 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24510 @node The Package STANDARD
24511 @section The Package @code{STANDARD}
24514 The package @code{STANDARD}, as implemented by HP Ada, is fully
24515 described in the @cite{Ada Reference Manual} and in the
24516 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24517 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24519 In addition, HP Ada supports the Latin-1 character set in
24520 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24521 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24522 the type @code{WIDE_CHARACTER}.
24524 The floating-point types supported by GNAT are those
24525 supported by HP Ada, but the defaults are different, and are controlled by
24526 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24528 @node The Package SYSTEM
24529 @section The Package @code{SYSTEM}
24532 HP Ada provides a specific version of the package
24533 @code{SYSTEM} for each platform on which the language is implemented.
24534 For the complete spec of the package @code{SYSTEM}, see
24535 Appendix F of the @cite{HP Ada Language Reference Manual}.
24537 On HP Ada, the package @code{SYSTEM} includes the following conversion
24540 @item @code{TO_ADDRESS(INTEGER)}
24542 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24544 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24546 @item @code{TO_INTEGER(ADDRESS)}
24548 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24550 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24551 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24555 By default, GNAT supplies a version of @code{SYSTEM} that matches
24556 the definition given in the @cite{Ada Reference Manual}.
24558 is a subset of the HP system definitions, which is as
24559 close as possible to the original definitions. The only difference
24560 is that the definition of @code{SYSTEM_NAME} is different:
24562 @smallexample @c ada
24564 type Name is (SYSTEM_NAME_GNAT);
24565 System_Name : constant Name := SYSTEM_NAME_GNAT;
24570 Also, GNAT adds the Ada declarations for
24571 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24573 However, the use of the following pragma causes GNAT
24574 to extend the definition of package @code{SYSTEM} so that it
24575 encompasses the full set of HP-specific extensions,
24576 including the functions listed above:
24578 @smallexample @c ada
24580 pragma Extend_System (Aux_DEC);
24585 The pragma @code{Extend_System} is a configuration pragma that
24586 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24587 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24589 HP Ada does not allow the recompilation of the package
24590 @code{SYSTEM}. Instead HP Ada provides several pragmas
24591 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24592 to modify values in the package @code{SYSTEM}.
24593 On OpenVMS Alpha systems, the pragma
24594 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24595 its single argument.
24597 GNAT does permit the recompilation of package @code{SYSTEM} using
24598 the special switch @option{-gnatg}, and this switch can be used if
24599 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24600 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24601 or @code{MEMORY_SIZE} by any other means.
24603 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24604 enumeration literal @code{SYSTEM_NAME_GNAT}.
24606 The definitions provided by the use of
24608 @smallexample @c ada
24609 pragma Extend_System (AUX_Dec);
24613 are virtually identical to those provided by the HP Ada 83 package
24614 @code{SYSTEM}. One important difference is that the name of the
24616 function for type @code{UNSIGNED_LONGWORD} is changed to
24617 @code{TO_ADDRESS_LONG}.
24618 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
24619 discussion of why this change was necessary.
24622 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
24624 an extension to Ada 83 not strictly compatible with the reference manual.
24625 GNAT, in order to be exactly compatible with the standard,
24626 does not provide this capability. In HP Ada 83, the
24627 point of this definition is to deal with a call like:
24629 @smallexample @c ada
24630 TO_ADDRESS (16#12777#);
24634 Normally, according to Ada 83 semantics, one would expect this to be
24635 ambiguous, since it matches both the @code{INTEGER} and
24636 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
24637 However, in HP Ada 83, there is no ambiguity, since the
24638 definition using @i{universal_integer} takes precedence.
24640 In GNAT, since the version with @i{universal_integer} cannot be supplied,
24642 not possible to be 100% compatible. Since there are many programs using
24643 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
24645 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
24646 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
24648 @smallexample @c ada
24649 function To_Address (X : Integer) return Address;
24650 pragma Pure_Function (To_Address);
24652 function To_Address_Long (X : Unsigned_Longword) return Address;
24653 pragma Pure_Function (To_Address_Long);
24657 This means that programs using @code{TO_ADDRESS} for
24658 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
24660 @node Tasking and Task-Related Features
24661 @section Tasking and Task-Related Features
24664 This section compares the treatment of tasking in GNAT
24665 and in HP Ada for OpenVMS Alpha.
24666 The GNAT description applies to both Alpha and I64 OpenVMS.
24667 For detailed information on tasking in
24668 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
24669 relevant run-time reference manual.
24672 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
24673 * Assigning Task IDs::
24674 * Task IDs and Delays::
24675 * Task-Related Pragmas::
24676 * Scheduling and Task Priority::
24678 * External Interrupts::
24681 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24682 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24685 On OpenVMS Alpha systems, each Ada task (except a passive
24686 task) is implemented as a single stream of execution
24687 that is created and managed by the kernel. On these
24688 systems, HP Ada tasking support is based on DECthreads,
24689 an implementation of the POSIX standard for threads.
24691 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
24692 code that calls DECthreads routines can be used together.
24693 The interaction between Ada tasks and DECthreads routines
24694 can have some benefits. For example when on OpenVMS Alpha,
24695 HP Ada can call C code that is already threaded.
24697 GNAT uses the facilities of DECthreads,
24698 and Ada tasks are mapped to threads.
24700 @node Assigning Task IDs
24701 @subsection Assigning Task IDs
24704 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
24705 the environment task that executes the main program. On
24706 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
24707 that have been created but are not yet activated.
24709 On OpenVMS Alpha systems, task IDs are assigned at
24710 activation. On GNAT systems, task IDs are also assigned at
24711 task creation but do not have the same form or values as
24712 task ID values in HP Ada. There is no null task, and the
24713 environment task does not have a specific task ID value.
24715 @node Task IDs and Delays
24716 @subsection Task IDs and Delays
24719 On OpenVMS Alpha systems, tasking delays are implemented
24720 using Timer System Services. The Task ID is used for the
24721 identification of the timer request (the @code{REQIDT} parameter).
24722 If Timers are used in the application take care not to use
24723 @code{0} for the identification, because cancelling such a timer
24724 will cancel all timers and may lead to unpredictable results.
24726 @node Task-Related Pragmas
24727 @subsection Task-Related Pragmas
24730 Ada supplies the pragma @code{TASK_STORAGE}, which allows
24731 specification of the size of the guard area for a task
24732 stack. (The guard area forms an area of memory that has no
24733 read or write access and thus helps in the detection of
24734 stack overflow.) On OpenVMS Alpha systems, if the pragma
24735 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
24736 area is created. In the absence of a pragma @code{TASK_STORAGE},
24737 a default guard area is created.
24739 GNAT supplies the following task-related pragmas:
24742 @item @code{TASK_INFO}
24744 This pragma appears within a task definition and
24745 applies to the task in which it appears. The argument
24746 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
24748 @item @code{TASK_STORAGE}
24750 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
24751 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
24752 @code{SUPPRESS}, and @code{VOLATILE}.
24754 @node Scheduling and Task Priority
24755 @subsection Scheduling and Task Priority
24758 HP Ada implements the Ada language requirement that
24759 when two tasks are eligible for execution and they have
24760 different priorities, the lower priority task does not
24761 execute while the higher priority task is waiting. The HP
24762 Ada Run-Time Library keeps a task running until either the
24763 task is suspended or a higher priority task becomes ready.
24765 On OpenVMS Alpha systems, the default strategy is round-
24766 robin with preemption. Tasks of equal priority take turns
24767 at the processor. A task is run for a certain period of
24768 time and then placed at the tail of the ready queue for
24769 its priority level.
24771 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
24772 which can be used to enable or disable round-robin
24773 scheduling of tasks with the same priority.
24774 See the relevant HP Ada run-time reference manual for
24775 information on using the pragmas to control HP Ada task
24778 GNAT follows the scheduling rules of Annex D (Real-Time
24779 Annex) of the @cite{Ada Reference Manual}. In general, this
24780 scheduling strategy is fully compatible with HP Ada
24781 although it provides some additional constraints (as
24782 fully documented in Annex D).
24783 GNAT implements time slicing control in a manner compatible with
24784 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
24785 are identical to the HP Ada 83 pragma of the same name.
24786 Note that it is not possible to mix GNAT tasking and
24787 HP Ada 83 tasking in the same program, since the two run-time
24788 libraries are not compatible.
24790 @node The Task Stack
24791 @subsection The Task Stack
24794 In HP Ada, a task stack is allocated each time a
24795 non-passive task is activated. As soon as the task is
24796 terminated, the storage for the task stack is deallocated.
24797 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
24798 a default stack size is used. Also, regardless of the size
24799 specified, some additional space is allocated for task
24800 management purposes. On OpenVMS Alpha systems, at least
24801 one page is allocated.
24803 GNAT handles task stacks in a similar manner. In accordance with
24804 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
24805 an alternative method for controlling the task stack size.
24806 The specification of the attribute @code{T'STORAGE_SIZE} is also
24807 supported in a manner compatible with HP Ada.
24809 @node External Interrupts
24810 @subsection External Interrupts
24813 On HP Ada, external interrupts can be associated with task entries.
24814 GNAT is compatible with HP Ada in its handling of external interrupts.
24816 @node Pragmas and Pragma-Related Features
24817 @section Pragmas and Pragma-Related Features
24820 Both HP Ada and GNAT supply all language-defined pragmas
24821 as specified by the Ada 83 standard. GNAT also supplies all
24822 language-defined pragmas introduced by Ada 95 and Ada 2005.
24823 In addition, GNAT implements the implementation-defined pragmas
24827 @item @code{AST_ENTRY}
24829 @item @code{COMMON_OBJECT}
24831 @item @code{COMPONENT_ALIGNMENT}
24833 @item @code{EXPORT_EXCEPTION}
24835 @item @code{EXPORT_FUNCTION}
24837 @item @code{EXPORT_OBJECT}
24839 @item @code{EXPORT_PROCEDURE}
24841 @item @code{EXPORT_VALUED_PROCEDURE}
24843 @item @code{FLOAT_REPRESENTATION}
24847 @item @code{IMPORT_EXCEPTION}
24849 @item @code{IMPORT_FUNCTION}
24851 @item @code{IMPORT_OBJECT}
24853 @item @code{IMPORT_PROCEDURE}
24855 @item @code{IMPORT_VALUED_PROCEDURE}
24857 @item @code{INLINE_GENERIC}
24859 @item @code{INTERFACE_NAME}
24861 @item @code{LONG_FLOAT}
24863 @item @code{MAIN_STORAGE}
24865 @item @code{PASSIVE}
24867 @item @code{PSECT_OBJECT}
24869 @item @code{SHARE_GENERIC}
24871 @item @code{SUPPRESS_ALL}
24873 @item @code{TASK_STORAGE}
24875 @item @code{TIME_SLICE}
24881 These pragmas are all fully implemented, with the exception of @code{TITLE},
24882 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
24883 recognized, but which have no
24884 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
24885 use of Ada protected objects. In GNAT, all generics are inlined.
24887 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
24888 a separate subprogram specification which must appear before the
24891 GNAT also supplies a number of implementation-defined pragmas as follows:
24893 @item @code{ABORT_DEFER}
24895 @item @code{ADA_83}
24897 @item @code{ADA_95}
24899 @item @code{ADA_05}
24901 @item @code{ANNOTATE}
24903 @item @code{ASSERT}
24905 @item @code{C_PASS_BY_COPY}
24907 @item @code{CPP_CLASS}
24909 @item @code{CPP_CONSTRUCTOR}
24911 @item @code{CPP_DESTRUCTOR}
24915 @item @code{EXTEND_SYSTEM}
24917 @item @code{LINKER_ALIAS}
24919 @item @code{LINKER_SECTION}
24921 @item @code{MACHINE_ATTRIBUTE}
24923 @item @code{NO_RETURN}
24925 @item @code{PURE_FUNCTION}
24927 @item @code{SOURCE_FILE_NAME}
24929 @item @code{SOURCE_REFERENCE}
24931 @item @code{TASK_INFO}
24933 @item @code{UNCHECKED_UNION}
24935 @item @code{UNIMPLEMENTED_UNIT}
24937 @item @code{UNIVERSAL_DATA}
24939 @item @code{UNSUPPRESS}
24941 @item @code{WARNINGS}
24943 @item @code{WEAK_EXTERNAL}
24947 For full details on these GNAT implementation-defined pragmas,
24948 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
24952 * Restrictions on the Pragma INLINE::
24953 * Restrictions on the Pragma INTERFACE::
24954 * Restrictions on the Pragma SYSTEM_NAME::
24957 @node Restrictions on the Pragma INLINE
24958 @subsection Restrictions on Pragma @code{INLINE}
24961 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
24963 @item Parameters cannot have a task type.
24965 @item Function results cannot be task types, unconstrained
24966 array types, or unconstrained types with discriminants.
24968 @item Bodies cannot declare the following:
24970 @item Subprogram body or stub (imported subprogram is allowed)
24974 @item Generic declarations
24976 @item Instantiations
24980 @item Access types (types derived from access types allowed)
24982 @item Array or record types
24984 @item Dependent tasks
24986 @item Direct recursive calls of subprogram or containing
24987 subprogram, directly or via a renaming
24993 In GNAT, the only restriction on pragma @code{INLINE} is that the
24994 body must occur before the call if both are in the same
24995 unit, and the size must be appropriately small. There are
24996 no other specific restrictions which cause subprograms to
24997 be incapable of being inlined.
24999 @node Restrictions on the Pragma INTERFACE
25000 @subsection Restrictions on Pragma @code{INTERFACE}
25003 The following restrictions on pragma @code{INTERFACE}
25004 are enforced by both HP Ada and GNAT:
25006 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25007 Default is the default on OpenVMS Alpha systems.
25009 @item Parameter passing: Language specifies default
25010 mechanisms but can be overridden with an @code{EXPORT} pragma.
25013 @item Ada: Use internal Ada rules.
25015 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25016 record or task type. Result cannot be a string, an
25017 array, or a record.
25019 @item Fortran: Parameters cannot have a task type. Result cannot
25020 be a string, an array, or a record.
25025 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25026 record parameters for all languages.
25028 @node Restrictions on the Pragma SYSTEM_NAME
25029 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25032 For HP Ada for OpenVMS Alpha, the enumeration literal
25033 for the type @code{NAME} is @code{OPENVMS_AXP}.
25034 In GNAT, the enumeration
25035 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25037 @node Library of Predefined Units
25038 @section Library of Predefined Units
25041 A library of predefined units is provided as part of the
25042 HP Ada and GNAT implementations. HP Ada does not provide
25043 the package @code{MACHINE_CODE} but instead recommends importing
25046 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25047 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25049 The HP Ada Predefined Library units are modified to remove post-Ada 83
25050 incompatibilities and to make them interoperable with GNAT
25051 (@pxref{Changes to DECLIB}, for details).
25052 The units are located in the @file{DECLIB} directory.
25054 The GNAT RTL is contained in
25055 the @file{ADALIB} directory, and
25056 the default search path is set up to find @code{DECLIB} units in preference
25057 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25058 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25061 * Changes to DECLIB::
25064 @node Changes to DECLIB
25065 @subsection Changes to @code{DECLIB}
25068 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25069 compatibility are minor and include the following:
25072 @item Adjusting the location of pragmas and record representation
25073 clauses to obey Ada 95 (and thus Ada 2005) rules
25075 @item Adding the proper notation to generic formal parameters
25076 that take unconstrained types in instantiation
25078 @item Adding pragma @code{ELABORATE_BODY} to package specs
25079 that have package bodies not otherwise allowed
25081 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25082 ``@code{PROTECTD}''.
25083 Currently these are found only in the @code{STARLET} package spec.
25085 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25086 where the address size is constrained to 32 bits.
25090 None of the above changes is visible to users.
25096 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25099 @item Command Language Interpreter (CLI interface)
25101 @item DECtalk Run-Time Library (DTK interface)
25103 @item Librarian utility routines (LBR interface)
25105 @item General Purpose Run-Time Library (LIB interface)
25107 @item Math Run-Time Library (MTH interface)
25109 @item National Character Set Run-Time Library (NCS interface)
25111 @item Compiled Code Support Run-Time Library (OTS interface)
25113 @item Parallel Processing Run-Time Library (PPL interface)
25115 @item Screen Management Run-Time Library (SMG interface)
25117 @item Sort Run-Time Library (SOR interface)
25119 @item String Run-Time Library (STR interface)
25121 @item STARLET System Library
25124 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25126 @item X Windows Toolkit (XT interface)
25128 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25132 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25133 directory, on both the Alpha and I64 OpenVMS platforms.
25135 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25137 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25138 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25139 @code{Xt}, and @code{X_Lib}
25140 causing the default X/Motif sharable image libraries to be linked in. This
25141 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25142 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25144 It may be necessary to edit these options files to update or correct the
25145 library names if, for example, the newer X/Motif bindings from
25146 @file{ADA$EXAMPLES}
25147 had been (previous to installing GNAT) copied and renamed to supersede the
25148 default @file{ADA$PREDEFINED} versions.
25151 * Shared Libraries and Options Files::
25152 * Interfaces to C::
25155 @node Shared Libraries and Options Files
25156 @subsection Shared Libraries and Options Files
25159 When using the HP Ada
25160 predefined X and Motif bindings, the linking with their sharable images is
25161 done automatically by @command{GNAT LINK}.
25162 When using other X and Motif bindings, you need
25163 to add the corresponding sharable images to the command line for
25164 @code{GNAT LINK}. When linking with shared libraries, or with
25165 @file{.OPT} files, you must
25166 also add them to the command line for @command{GNAT LINK}.
25168 A shared library to be used with GNAT is built in the same way as other
25169 libraries under VMS. The VMS Link command can be used in standard fashion.
25171 @node Interfaces to C
25172 @subsection Interfaces to C
25176 provides the following Ada types and operations:
25179 @item C types package (@code{C_TYPES})
25181 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25183 @item Other_types (@code{SHORT_INT})
25187 Interfacing to C with GNAT, you can use the above approach
25188 described for HP Ada or the facilities of Annex B of
25189 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25190 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25191 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25193 The @option{-gnatF} qualifier forces default and explicit
25194 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25195 to be uppercased for compatibility with the default behavior
25196 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25198 @node Main Program Definition
25199 @section Main Program Definition
25202 The following section discusses differences in the
25203 definition of main programs on HP Ada and GNAT.
25204 On HP Ada, main programs are defined to meet the
25205 following conditions:
25207 @item Procedure with no formal parameters (returns @code{0} upon
25210 @item Procedure with no formal parameters (returns @code{42} when
25211 an unhandled exception is raised)
25213 @item Function with no formal parameters whose returned value
25214 is of a discrete type
25216 @item Procedure with one @code{out} formal of a discrete type for
25217 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25222 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25223 a main function or main procedure returns a discrete
25224 value whose size is less than 64 bits (32 on VAX systems),
25225 the value is zero- or sign-extended as appropriate.
25226 On GNAT, main programs are defined as follows:
25228 @item Must be a non-generic, parameterless subprogram that
25229 is either a procedure or function returning an Ada
25230 @code{STANDARD.INTEGER} (the predefined type)
25232 @item Cannot be a generic subprogram or an instantiation of a
25236 @node Implementation-Defined Attributes
25237 @section Implementation-Defined Attributes
25240 GNAT provides all HP Ada implementation-defined
25243 @node Compiler and Run-Time Interfacing
25244 @section Compiler and Run-Time Interfacing
25247 HP Ada provides the following qualifiers to pass options to the linker
25250 @item @option{/WAIT} and @option{/SUBMIT}
25252 @item @option{/COMMAND}
25254 @item @option{/@r{[}NO@r{]}MAP}
25256 @item @option{/OUTPUT=@var{file-spec}}
25258 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25262 To pass options to the linker, GNAT provides the following
25266 @item @option{/EXECUTABLE=@var{exec-name}}
25268 @item @option{/VERBOSE}
25270 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25274 For more information on these switches, see
25275 @ref{Switches for gnatlink}.
25276 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25277 to control optimization. HP Ada also supplies the
25280 @item @code{OPTIMIZE}
25282 @item @code{INLINE}
25284 @item @code{INLINE_GENERIC}
25286 @item @code{SUPPRESS_ALL}
25288 @item @code{PASSIVE}
25292 In GNAT, optimization is controlled strictly by command
25293 line parameters, as described in the corresponding section of this guide.
25294 The HP pragmas for control of optimization are
25295 recognized but ignored.
25297 Note that in GNAT, the default is optimization off, whereas in HP Ada
25298 the default is that optimization is turned on.
25300 @node Program Compilation and Library Management
25301 @section Program Compilation and Library Management
25304 HP Ada and GNAT provide a comparable set of commands to
25305 build programs. HP Ada also provides a program library,
25306 which is a concept that does not exist on GNAT. Instead,
25307 GNAT provides directories of sources that are compiled as
25310 The following table summarizes
25311 the HP Ada commands and provides
25312 equivalent GNAT commands. In this table, some GNAT
25313 equivalents reflect the fact that GNAT does not use the
25314 concept of a program library. Instead, it uses a model
25315 in which collections of source and object files are used
25316 in a manner consistent with other languages like C and
25317 Fortran. Therefore, standard system file commands are used
25318 to manipulate these elements. Those GNAT commands are marked with
25320 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25323 @multitable @columnfractions .35 .65
25325 @item @emph{HP Ada Command}
25326 @tab @emph{GNAT Equivalent / Description}
25328 @item @command{ADA}
25329 @tab @command{GNAT COMPILE}@*
25330 Invokes the compiler to compile one or more Ada source files.
25332 @item @command{ACS ATTACH}@*
25333 @tab [No equivalent]@*
25334 Switches control of terminal from current process running the program
25337 @item @command{ACS CHECK}
25338 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25339 Forms the execution closure of one
25340 or more compiled units and checks completeness and currency.
25342 @item @command{ACS COMPILE}
25343 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25344 Forms the execution closure of one or
25345 more specified units, checks completeness and currency,
25346 identifies units that have revised source files, compiles same,
25347 and recompiles units that are or will become obsolete.
25348 Also completes incomplete generic instantiations.
25350 @item @command{ACS COPY FOREIGN}
25352 Copies a foreign object file into the program library as a
25355 @item @command{ACS COPY UNIT}
25357 Copies a compiled unit from one program library to another.
25359 @item @command{ACS CREATE LIBRARY}
25360 @tab Create /directory (*)@*
25361 Creates a program library.
25363 @item @command{ACS CREATE SUBLIBRARY}
25364 @tab Create /directory (*)@*
25365 Creates a program sublibrary.
25367 @item @command{ACS DELETE LIBRARY}
25369 Deletes a program library and its contents.
25371 @item @command{ACS DELETE SUBLIBRARY}
25373 Deletes a program sublibrary and its contents.
25375 @item @command{ACS DELETE UNIT}
25376 @tab Delete file (*)@*
25377 On OpenVMS systems, deletes one or more compiled units from
25378 the current program library.
25380 @item @command{ACS DIRECTORY}
25381 @tab Directory (*)@*
25382 On OpenVMS systems, lists units contained in the current
25385 @item @command{ACS ENTER FOREIGN}
25387 Allows the import of a foreign body as an Ada library
25388 spec and enters a reference to a pointer.
25390 @item @command{ACS ENTER UNIT}
25392 Enters a reference (pointer) from the current program library to
25393 a unit compiled into another program library.
25395 @item @command{ACS EXIT}
25396 @tab [No equivalent]@*
25397 Exits from the program library manager.
25399 @item @command{ACS EXPORT}
25401 Creates an object file that contains system-specific object code
25402 for one or more units. With GNAT, object files can simply be copied
25403 into the desired directory.
25405 @item @command{ACS EXTRACT SOURCE}
25407 Allows access to the copied source file for each Ada compilation unit
25409 @item @command{ACS HELP}
25410 @tab @command{HELP GNAT}@*
25411 Provides online help.
25413 @item @command{ACS LINK}
25414 @tab @command{GNAT LINK}@*
25415 Links an object file containing Ada units into an executable file.
25417 @item @command{ACS LOAD}
25419 Loads (partially compiles) Ada units into the program library.
25420 Allows loading a program from a collection of files into a library
25421 without knowing the relationship among units.
25423 @item @command{ACS MERGE}
25425 Merges into the current program library, one or more units from
25426 another library where they were modified.
25428 @item @command{ACS RECOMPILE}
25429 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25430 Recompiles from external or copied source files any obsolete
25431 unit in the closure. Also, completes any incomplete generic
25434 @item @command{ACS REENTER}
25435 @tab @command{GNAT MAKE}@*
25436 Reenters current references to units compiled after last entered
25437 with the @command{ACS ENTER UNIT} command.
25439 @item @command{ACS SET LIBRARY}
25440 @tab Set default (*)@*
25441 Defines a program library to be the compilation context as well
25442 as the target library for compiler output and commands in general.
25444 @item @command{ACS SET PRAGMA}
25445 @tab Edit @file{gnat.adc} (*)@*
25446 Redefines specified values of the library characteristics
25447 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25448 and @code{Float_Representation}.
25450 @item @command{ACS SET SOURCE}
25451 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25452 Defines the source file search list for the @command{ACS COMPILE} command.
25454 @item @command{ACS SHOW LIBRARY}
25455 @tab Directory (*)@*
25456 Lists information about one or more program libraries.
25458 @item @command{ACS SHOW PROGRAM}
25459 @tab [No equivalent]@*
25460 Lists information about the execution closure of one or
25461 more units in the program library.
25463 @item @command{ACS SHOW SOURCE}
25464 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25465 Shows the source file search used when compiling units.
25467 @item @command{ACS SHOW VERSION}
25468 @tab Compile with @option{VERBOSE} option
25469 Displays the version number of the compiler and program library
25472 @item @command{ACS SPAWN}
25473 @tab [No equivalent]@*
25474 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25477 @item @command{ACS VERIFY}
25478 @tab [No equivalent]@*
25479 Performs a series of consistency checks on a program library to
25480 determine whether the library structure and library files are in
25487 @section Input-Output
25490 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25491 Management Services (RMS) to perform operations on
25495 HP Ada and GNAT predefine an identical set of input-
25496 output packages. To make the use of the
25497 generic @code{TEXT_IO} operations more convenient, HP Ada
25498 provides predefined library packages that instantiate the
25499 integer and floating-point operations for the predefined
25500 integer and floating-point types as shown in the following table.
25502 @multitable @columnfractions .45 .55
25503 @item @emph{Package Name} @tab Instantiation
25505 @item @code{INTEGER_TEXT_IO}
25506 @tab @code{INTEGER_IO(INTEGER)}
25508 @item @code{SHORT_INTEGER_TEXT_IO}
25509 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25511 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25512 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25514 @item @code{FLOAT_TEXT_IO}
25515 @tab @code{FLOAT_IO(FLOAT)}
25517 @item @code{LONG_FLOAT_TEXT_IO}
25518 @tab @code{FLOAT_IO(LONG_FLOAT)}
25522 The HP Ada predefined packages and their operations
25523 are implemented using OpenVMS Alpha files and input-output
25524 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25525 Familiarity with the following is recommended:
25527 @item RMS file organizations and access methods
25529 @item OpenVMS file specifications and directories
25531 @item OpenVMS File Definition Language (FDL)
25535 GNAT provides I/O facilities that are completely
25536 compatible with HP Ada. The distribution includes the
25537 standard HP Ada versions of all I/O packages, operating
25538 in a manner compatible with HP Ada. In particular, the
25539 following packages are by default the HP Ada (Ada 83)
25540 versions of these packages rather than the renamings
25541 suggested in Annex J of the Ada Reference Manual:
25543 @item @code{TEXT_IO}
25545 @item @code{SEQUENTIAL_IO}
25547 @item @code{DIRECT_IO}
25551 The use of the standard child package syntax (for
25552 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25554 GNAT provides HP-compatible predefined instantiations
25555 of the @code{TEXT_IO} packages, and also
25556 provides the standard predefined instantiations required
25557 by the @cite{Ada Reference Manual}.
25559 For further information on how GNAT interfaces to the file
25560 system or how I/O is implemented in programs written in
25561 mixed languages, see @ref{Implementation of the Standard I/O,,,
25562 gnat_rm, GNAT Reference Manual}.
25563 This chapter covers the following:
25565 @item Standard I/O packages
25567 @item @code{FORM} strings
25569 @item @code{ADA.DIRECT_IO}
25571 @item @code{ADA.SEQUENTIAL_IO}
25573 @item @code{ADA.TEXT_IO}
25575 @item Stream pointer positioning
25577 @item Reading and writing non-regular files
25579 @item @code{GET_IMMEDIATE}
25581 @item Treating @code{TEXT_IO} files as streams
25588 @node Implementation Limits
25589 @section Implementation Limits
25592 The following table lists implementation limits for HP Ada
25594 @multitable @columnfractions .60 .20 .20
25596 @item @emph{Compilation Parameter}
25601 @item In a subprogram or entry declaration, maximum number of
25602 formal parameters that are of an unconstrained record type
25607 @item Maximum identifier length (number of characters)
25612 @item Maximum number of characters in a source line
25617 @item Maximum collection size (number of bytes)
25622 @item Maximum number of discriminants for a record type
25627 @item Maximum number of formal parameters in an entry or
25628 subprogram declaration
25633 @item Maximum number of dimensions in an array type
25638 @item Maximum number of library units and subunits in a compilation.
25643 @item Maximum number of library units and subunits in an execution.
25648 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
25649 or @code{PSECT_OBJECT}
25654 @item Maximum number of enumeration literals in an enumeration type
25660 @item Maximum number of lines in a source file
25665 @item Maximum number of bits in any object
25670 @item Maximum size of the static portion of a stack frame (approximate)
25675 @node Tools and Utilities
25676 @section Tools and Utilities
25679 The following table lists some of the OpenVMS development tools
25680 available for HP Ada, and the corresponding tools for
25681 use with @value{EDITION} on Alpha and I64 platforms.
25682 Aside from the debugger, all the OpenVMS tools identified are part
25683 of the DECset package.
25686 @c Specify table in TeX since Texinfo does a poor job
25690 \settabs\+Language-Sensitive Editor\quad
25691 &Product with HP Ada\quad
25694 &\it Product with HP Ada
25695 & \it Product with GNAT Pro\cr
25697 \+Code Management System
25701 \+Language-Sensitive Editor
25703 & emacs or HP LSE (Alpha)\cr
25713 & OpenVMS Debug (I64)\cr
25715 \+Source Code Analyzer /
25732 \+Coverage Analyzer
25736 \+Module Management
25738 & Not applicable\cr
25748 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
25749 @c the TeX version above for the printed version
25751 @c @multitable @columnfractions .3 .4 .4
25752 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
25754 @tab @i{Tool with HP Ada}
25755 @tab @i{Tool with @value{EDITION}}
25756 @item Code Management@*System
25759 @item Language-Sensitive@*Editor
25761 @tab emacs or HP LSE (Alpha)
25770 @tab OpenVMS Debug (I64)
25771 @item Source Code Analyzer /@*Cross Referencer
25775 @tab HP Digital Test@*Manager (DTM)
25777 @item Performance and@*Coverage Analyzer
25780 @item Module Management@*System
25782 @tab Not applicable
25789 @c **************************************
25790 @node Platform-Specific Information for the Run-Time Libraries
25791 @appendix Platform-Specific Information for the Run-Time Libraries
25792 @cindex Tasking and threads libraries
25793 @cindex Threads libraries and tasking
25794 @cindex Run-time libraries (platform-specific information)
25797 The GNAT run-time implementation may vary with respect to both the
25798 underlying threads library and the exception handling scheme.
25799 For threads support, one or more of the following are supplied:
25801 @item @b{native threads library}, a binding to the thread package from
25802 the underlying operating system
25804 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
25805 POSIX thread package
25809 For exception handling, either or both of two models are supplied:
25811 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
25812 Most programs should experience a substantial speed improvement by
25813 being compiled with a ZCX run-time.
25814 This is especially true for
25815 tasking applications or applications with many exception handlers.}
25816 @cindex Zero-Cost Exceptions
25817 @cindex ZCX (Zero-Cost Exceptions)
25818 which uses binder-generated tables that
25819 are interrogated at run time to locate a handler
25821 @item @b{setjmp / longjmp} (``SJLJ''),
25822 @cindex setjmp/longjmp Exception Model
25823 @cindex SJLJ (setjmp/longjmp Exception Model)
25824 which uses dynamically-set data to establish
25825 the set of handlers
25829 This appendix summarizes which combinations of threads and exception support
25830 are supplied on various GNAT platforms.
25831 It then shows how to select a particular library either
25832 permanently or temporarily,
25833 explains the properties of (and tradeoffs among) the various threads
25834 libraries, and provides some additional
25835 information about several specific platforms.
25838 * Summary of Run-Time Configurations::
25839 * Specifying a Run-Time Library::
25840 * Choosing the Scheduling Policy::
25841 * Solaris-Specific Considerations::
25842 * Linux-Specific Considerations::
25843 * AIX-Specific Considerations::
25844 * Irix-Specific Considerations::
25845 * RTX-Specific Considerations::
25848 @node Summary of Run-Time Configurations
25849 @section Summary of Run-Time Configurations
25851 @multitable @columnfractions .30 .70
25852 @item @b{alpha-openvms}
25853 @item @code{@ @ }@i{rts-native (default)}
25854 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25855 @item @code{@ @ @ @ }Exceptions @tab ZCX
25857 @item @b{alpha-tru64}
25858 @item @code{@ @ }@i{rts-native (default)}
25859 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25860 @item @code{@ @ @ @ }Exceptions @tab ZCX
25862 @item @code{@ @ }@i{rts-sjlj}
25863 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25864 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25866 @item @b{ia64-hp_linux}
25867 @item @code{@ @ }@i{rts-native (default)}
25868 @item @code{@ @ @ @ }Tasking @tab pthread library
25869 @item @code{@ @ @ @ }Exceptions @tab ZCX
25871 @item @b{ia64-hpux}
25872 @item @code{@ @ }@i{rts-native (default)}
25873 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25874 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25876 @item @b{ia64-openvms}
25877 @item @code{@ @ }@i{rts-native (default)}
25878 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25879 @item @code{@ @ @ @ }Exceptions @tab ZCX
25881 @item @b{ia64-sgi_linux}
25882 @item @code{@ @ }@i{rts-native (default)}
25883 @item @code{@ @ @ @ }Tasking @tab pthread library
25884 @item @code{@ @ @ @ }Exceptions @tab ZCX
25886 @item @b{mips-irix}
25887 @item @code{@ @ }@i{rts-native (default)}
25888 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
25889 @item @code{@ @ @ @ }Exceptions @tab ZCX
25892 @item @code{@ @ }@i{rts-native (default)}
25893 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25894 @item @code{@ @ @ @ }Exceptions @tab ZCX
25896 @item @code{@ @ }@i{rts-sjlj}
25897 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25898 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25901 @item @code{@ @ }@i{rts-native (default)}
25902 @item @code{@ @ @ @ }Tasking @tab native AIX threads
25903 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25905 @item @b{ppc-darwin}
25906 @item @code{@ @ }@i{rts-native (default)}
25907 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
25908 @item @code{@ @ @ @ }Exceptions @tab ZCX
25910 @item @b{sparc-solaris} @tab
25911 @item @code{@ @ }@i{rts-native (default)}
25912 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25913 @item @code{@ @ @ @ }Exceptions @tab ZCX
25915 @item @code{@ @ }@i{rts-pthread}
25916 @item @code{@ @ @ @ }Tasking @tab pthread library
25917 @item @code{@ @ @ @ }Exceptions @tab ZCX
25919 @item @code{@ @ }@i{rts-sjlj}
25920 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25921 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25923 @item @b{sparc64-solaris} @tab
25924 @item @code{@ @ }@i{rts-native (default)}
25925 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25926 @item @code{@ @ @ @ }Exceptions @tab ZCX
25928 @item @b{x86-linux}
25929 @item @code{@ @ }@i{rts-native (default)}
25930 @item @code{@ @ @ @ }Tasking @tab pthread library
25931 @item @code{@ @ @ @ }Exceptions @tab ZCX
25933 @item @code{@ @ }@i{rts-sjlj}
25934 @item @code{@ @ @ @ }Tasking @tab pthread library
25935 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25938 @item @code{@ @ }@i{rts-native (default)}
25939 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
25940 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25942 @item @b{x86-solaris}
25943 @item @code{@ @ }@i{rts-native (default)}
25944 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
25945 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25947 @item @b{x86-windows}
25948 @item @code{@ @ }@i{rts-native (default)}
25949 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25950 @item @code{@ @ @ @ }Exceptions @tab ZCX
25952 @item @code{@ @ }@i{rts-sjlj (default)}
25953 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25954 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25956 @item @b{x86-windows-rtx}
25957 @item @code{@ @ }@i{rts-rtx-rtss (default)}
25958 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
25959 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25961 @item @code{@ @ }@i{rts-rtx-w32}
25962 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
25963 @item @code{@ @ @ @ }Exceptions @tab ZCX
25965 @item @b{x86_64-linux}
25966 @item @code{@ @ }@i{rts-native (default)}
25967 @item @code{@ @ @ @ }Tasking @tab pthread library
25968 @item @code{@ @ @ @ }Exceptions @tab ZCX
25970 @item @code{@ @ }@i{rts-sjlj}
25971 @item @code{@ @ @ @ }Tasking @tab pthread library
25972 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25976 @node Specifying a Run-Time Library
25977 @section Specifying a Run-Time Library
25980 The @file{adainclude} subdirectory containing the sources of the GNAT
25981 run-time library, and the @file{adalib} subdirectory containing the
25982 @file{ALI} files and the static and/or shared GNAT library, are located
25983 in the gcc target-dependent area:
25986 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
25990 As indicated above, on some platforms several run-time libraries are supplied.
25991 These libraries are installed in the target dependent area and
25992 contain a complete source and binary subdirectory. The detailed description
25993 below explains the differences between the different libraries in terms of
25994 their thread support.
25996 The default run-time library (when GNAT is installed) is @emph{rts-native}.
25997 This default run time is selected by the means of soft links.
25998 For example on x86-linux:
26004 +--- adainclude----------+
26006 +--- adalib-----------+ |
26008 +--- rts-native | |
26010 | +--- adainclude <---+
26012 | +--- adalib <----+
26023 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26024 these soft links can be modified with the following commands:
26028 $ rm -f adainclude adalib
26029 $ ln -s rts-sjlj/adainclude adainclude
26030 $ ln -s rts-sjlj/adalib adalib
26034 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26035 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26036 @file{$target/ada_object_path}.
26038 Selecting another run-time library temporarily can be
26039 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26040 @cindex @option{--RTS} option
26042 @node Choosing the Scheduling Policy
26043 @section Choosing the Scheduling Policy
26046 When using a POSIX threads implementation, you have a choice of several
26047 scheduling policies: @code{SCHED_FIFO},
26048 @cindex @code{SCHED_FIFO} scheduling policy
26050 @cindex @code{SCHED_RR} scheduling policy
26051 and @code{SCHED_OTHER}.
26052 @cindex @code{SCHED_OTHER} scheduling policy
26053 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26054 or @code{SCHED_RR} requires special (e.g., root) privileges.
26056 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26058 @cindex @code{SCHED_FIFO} scheduling policy
26059 you can use one of the following:
26063 @code{pragma Time_Slice (0.0)}
26064 @cindex pragma Time_Slice
26066 the corresponding binder option @option{-T0}
26067 @cindex @option{-T0} option
26069 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26070 @cindex pragma Task_Dispatching_Policy
26074 To specify @code{SCHED_RR},
26075 @cindex @code{SCHED_RR} scheduling policy
26076 you should use @code{pragma Time_Slice} with a
26077 value greater than @code{0.0}, or else use the corresponding @option{-T}
26080 @node Solaris-Specific Considerations
26081 @section Solaris-Specific Considerations
26082 @cindex Solaris Sparc threads libraries
26085 This section addresses some topics related to the various threads libraries
26089 * Solaris Threads Issues::
26092 @node Solaris Threads Issues
26093 @subsection Solaris Threads Issues
26096 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26097 library based on POSIX threads --- @emph{rts-pthread}.
26098 @cindex rts-pthread threads library
26099 This run-time library has the advantage of being mostly shared across all
26100 POSIX-compliant thread implementations, and it also provides under
26101 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26102 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26103 and @code{PTHREAD_PRIO_PROTECT}
26104 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26105 semantics that can be selected using the predefined pragma
26106 @code{Locking_Policy}
26107 @cindex pragma Locking_Policy (under rts-pthread)
26109 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26110 @cindex @code{Inheritance_Locking} (under rts-pthread)
26111 @cindex @code{Ceiling_Locking} (under rts-pthread)
26113 As explained above, the native run-time library is based on the Solaris thread
26114 library (@code{libthread}) and is the default library.
26116 When the Solaris threads library is used (this is the default), programs
26117 compiled with GNAT can automatically take advantage of
26118 and can thus execute on multiple processors.
26119 The user can alternatively specify a processor on which the program should run
26120 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26122 setting the environment variable @env{GNAT_PROCESSOR}
26123 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26124 to one of the following:
26128 Use the default configuration (run the program on all
26129 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26133 Let the run-time implementation choose one processor and run the program on
26136 @item 0 .. Last_Proc
26137 Run the program on the specified processor.
26138 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26139 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26142 @node Linux-Specific Considerations
26143 @section Linux-Specific Considerations
26144 @cindex Linux threads libraries
26147 On GNU/Linux without NPTL support (usually system with GNU C Library
26148 older than 2.3), the signal model is not POSIX compliant, which means
26149 that to send a signal to the process, you need to send the signal to all
26150 threads, e.g.@: by using @code{killpg()}.
26152 @node AIX-Specific Considerations
26153 @section AIX-Specific Considerations
26154 @cindex AIX resolver library
26157 On AIX, the resolver library initializes some internal structure on
26158 the first call to @code{get*by*} functions, which are used to implement
26159 @code{GNAT.Sockets.Get_Host_By_Name} and
26160 @code{GNAT.Sockets.Get_Host_By_Address}.
26161 If such initialization occurs within an Ada task, and the stack size for
26162 the task is the default size, a stack overflow may occur.
26164 To avoid this overflow, the user should either ensure that the first call
26165 to @code{GNAT.Sockets.Get_Host_By_Name} or
26166 @code{GNAT.Sockets.Get_Host_By_Addrss}
26167 occurs in the environment task, or use @code{pragma Storage_Size} to
26168 specify a sufficiently large size for the stack of the task that contains
26171 @node Irix-Specific Considerations
26172 @section Irix-Specific Considerations
26173 @cindex Irix libraries
26176 The GCC support libraries coming with the Irix compiler have moved to
26177 their canonical place with respect to the general Irix ABI related
26178 conventions. Running applications built with the default shared GNAT
26179 run-time now requires the LD_LIBRARY_PATH environment variable to
26180 include this location. A possible way to achieve this is to issue the
26181 following command line on a bash prompt:
26185 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26189 @node RTX-Specific Considerations
26190 @section RTX-Specific Considerations
26191 @cindex RTX libraries
26194 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26195 API. Applications can be built to work in two different modes:
26199 Windows executables that run in Ring 3 to utilize memory protection
26200 (@emph{rts-rtx-w32}).
26203 Real-time subsystem (RTSS) executables that run in Ring 0, where
26204 performance can be optimized with RTSS applications taking precedent
26205 over all Windows applications (@emph{rts-rtx-rtss}).
26209 @c *******************************
26210 @node Example of Binder Output File
26211 @appendix Example of Binder Output File
26214 This Appendix displays the source code for @command{gnatbind}'s output
26215 file generated for a simple ``Hello World'' program.
26216 Comments have been added for clarification purposes.
26218 @smallexample @c adanocomment
26222 -- The package is called Ada_Main unless this name is actually used
26223 -- as a unit name in the partition, in which case some other unique
26227 package ada_main is
26229 Elab_Final_Code : Integer;
26230 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26232 -- The main program saves the parameters (argument count,
26233 -- argument values, environment pointer) in global variables
26234 -- for later access by other units including
26235 -- Ada.Command_Line.
26237 gnat_argc : Integer;
26238 gnat_argv : System.Address;
26239 gnat_envp : System.Address;
26241 -- The actual variables are stored in a library routine. This
26242 -- is useful for some shared library situations, where there
26243 -- are problems if variables are not in the library.
26245 pragma Import (C, gnat_argc);
26246 pragma Import (C, gnat_argv);
26247 pragma Import (C, gnat_envp);
26249 -- The exit status is similarly an external location
26251 gnat_exit_status : Integer;
26252 pragma Import (C, gnat_exit_status);
26254 GNAT_Version : constant String :=
26255 "GNAT Version: 6.0.0w (20061115)";
26256 pragma Export (C, GNAT_Version, "__gnat_version");
26258 -- This is the generated adafinal routine that performs
26259 -- finalization at the end of execution. In the case where
26260 -- Ada is the main program, this main program makes a call
26261 -- to adafinal at program termination.
26263 procedure adafinal;
26264 pragma Export (C, adafinal, "adafinal");
26266 -- This is the generated adainit routine that performs
26267 -- initialization at the start of execution. In the case
26268 -- where Ada is the main program, this main program makes
26269 -- a call to adainit at program startup.
26272 pragma Export (C, adainit, "adainit");
26274 -- This routine is called at the start of execution. It is
26275 -- a dummy routine that is used by the debugger to breakpoint
26276 -- at the start of execution.
26278 procedure Break_Start;
26279 pragma Import (C, Break_Start, "__gnat_break_start");
26281 -- This is the actual generated main program (it would be
26282 -- suppressed if the no main program switch were used). As
26283 -- required by standard system conventions, this program has
26284 -- the external name main.
26288 argv : System.Address;
26289 envp : System.Address)
26291 pragma Export (C, main, "main");
26293 -- The following set of constants give the version
26294 -- identification values for every unit in the bound
26295 -- partition. This identification is computed from all
26296 -- dependent semantic units, and corresponds to the
26297 -- string that would be returned by use of the
26298 -- Body_Version or Version attributes.
26300 type Version_32 is mod 2 ** 32;
26301 u00001 : constant Version_32 := 16#7880BEB3#;
26302 u00002 : constant Version_32 := 16#0D24CBD0#;
26303 u00003 : constant Version_32 := 16#3283DBEB#;
26304 u00004 : constant Version_32 := 16#2359F9ED#;
26305 u00005 : constant Version_32 := 16#664FB847#;
26306 u00006 : constant Version_32 := 16#68E803DF#;
26307 u00007 : constant Version_32 := 16#5572E604#;
26308 u00008 : constant Version_32 := 16#46B173D8#;
26309 u00009 : constant Version_32 := 16#156A40CF#;
26310 u00010 : constant Version_32 := 16#033DABE0#;
26311 u00011 : constant Version_32 := 16#6AB38FEA#;
26312 u00012 : constant Version_32 := 16#22B6217D#;
26313 u00013 : constant Version_32 := 16#68A22947#;
26314 u00014 : constant Version_32 := 16#18CC4A56#;
26315 u00015 : constant Version_32 := 16#08258E1B#;
26316 u00016 : constant Version_32 := 16#367D5222#;
26317 u00017 : constant Version_32 := 16#20C9ECA4#;
26318 u00018 : constant Version_32 := 16#50D32CB6#;
26319 u00019 : constant Version_32 := 16#39A8BB77#;
26320 u00020 : constant Version_32 := 16#5CF8FA2B#;
26321 u00021 : constant Version_32 := 16#2F1EB794#;
26322 u00022 : constant Version_32 := 16#31AB6444#;
26323 u00023 : constant Version_32 := 16#1574B6E9#;
26324 u00024 : constant Version_32 := 16#5109C189#;
26325 u00025 : constant Version_32 := 16#56D770CD#;
26326 u00026 : constant Version_32 := 16#02F9DE3D#;
26327 u00027 : constant Version_32 := 16#08AB6B2C#;
26328 u00028 : constant Version_32 := 16#3FA37670#;
26329 u00029 : constant Version_32 := 16#476457A0#;
26330 u00030 : constant Version_32 := 16#731E1B6E#;
26331 u00031 : constant Version_32 := 16#23C2E789#;
26332 u00032 : constant Version_32 := 16#0F1BD6A1#;
26333 u00033 : constant Version_32 := 16#7C25DE96#;
26334 u00034 : constant Version_32 := 16#39ADFFA2#;
26335 u00035 : constant Version_32 := 16#571DE3E7#;
26336 u00036 : constant Version_32 := 16#5EB646AB#;
26337 u00037 : constant Version_32 := 16#4249379B#;
26338 u00038 : constant Version_32 := 16#0357E00A#;
26339 u00039 : constant Version_32 := 16#3784FB72#;
26340 u00040 : constant Version_32 := 16#2E723019#;
26341 u00041 : constant Version_32 := 16#623358EA#;
26342 u00042 : constant Version_32 := 16#107F9465#;
26343 u00043 : constant Version_32 := 16#6843F68A#;
26344 u00044 : constant Version_32 := 16#63305874#;
26345 u00045 : constant Version_32 := 16#31E56CE1#;
26346 u00046 : constant Version_32 := 16#02917970#;
26347 u00047 : constant Version_32 := 16#6CCBA70E#;
26348 u00048 : constant Version_32 := 16#41CD4204#;
26349 u00049 : constant Version_32 := 16#572E3F58#;
26350 u00050 : constant Version_32 := 16#20729FF5#;
26351 u00051 : constant Version_32 := 16#1D4F93E8#;
26352 u00052 : constant Version_32 := 16#30B2EC3D#;
26353 u00053 : constant Version_32 := 16#34054F96#;
26354 u00054 : constant Version_32 := 16#5A199860#;
26355 u00055 : constant Version_32 := 16#0E7F912B#;
26356 u00056 : constant Version_32 := 16#5760634A#;
26357 u00057 : constant Version_32 := 16#5D851835#;
26359 -- The following Export pragmas export the version numbers
26360 -- with symbolic names ending in B (for body) or S
26361 -- (for spec) so that they can be located in a link. The
26362 -- information provided here is sufficient to track down
26363 -- the exact versions of units used in a given build.
26365 pragma Export (C, u00001, "helloB");
26366 pragma Export (C, u00002, "system__standard_libraryB");
26367 pragma Export (C, u00003, "system__standard_libraryS");
26368 pragma Export (C, u00004, "adaS");
26369 pragma Export (C, u00005, "ada__text_ioB");
26370 pragma Export (C, u00006, "ada__text_ioS");
26371 pragma Export (C, u00007, "ada__exceptionsB");
26372 pragma Export (C, u00008, "ada__exceptionsS");
26373 pragma Export (C, u00009, "gnatS");
26374 pragma Export (C, u00010, "gnat__heap_sort_aB");
26375 pragma Export (C, u00011, "gnat__heap_sort_aS");
26376 pragma Export (C, u00012, "systemS");
26377 pragma Export (C, u00013, "system__exception_tableB");
26378 pragma Export (C, u00014, "system__exception_tableS");
26379 pragma Export (C, u00015, "gnat__htableB");
26380 pragma Export (C, u00016, "gnat__htableS");
26381 pragma Export (C, u00017, "system__exceptionsS");
26382 pragma Export (C, u00018, "system__machine_state_operationsB");
26383 pragma Export (C, u00019, "system__machine_state_operationsS");
26384 pragma Export (C, u00020, "system__machine_codeS");
26385 pragma Export (C, u00021, "system__storage_elementsB");
26386 pragma Export (C, u00022, "system__storage_elementsS");
26387 pragma Export (C, u00023, "system__secondary_stackB");
26388 pragma Export (C, u00024, "system__secondary_stackS");
26389 pragma Export (C, u00025, "system__parametersB");
26390 pragma Export (C, u00026, "system__parametersS");
26391 pragma Export (C, u00027, "system__soft_linksB");
26392 pragma Export (C, u00028, "system__soft_linksS");
26393 pragma Export (C, u00029, "system__stack_checkingB");
26394 pragma Export (C, u00030, "system__stack_checkingS");
26395 pragma Export (C, u00031, "system__tracebackB");
26396 pragma Export (C, u00032, "system__tracebackS");
26397 pragma Export (C, u00033, "ada__streamsS");
26398 pragma Export (C, u00034, "ada__tagsB");
26399 pragma Export (C, u00035, "ada__tagsS");
26400 pragma Export (C, u00036, "system__string_opsB");
26401 pragma Export (C, u00037, "system__string_opsS");
26402 pragma Export (C, u00038, "interfacesS");
26403 pragma Export (C, u00039, "interfaces__c_streamsB");
26404 pragma Export (C, u00040, "interfaces__c_streamsS");
26405 pragma Export (C, u00041, "system__file_ioB");
26406 pragma Export (C, u00042, "system__file_ioS");
26407 pragma Export (C, u00043, "ada__finalizationB");
26408 pragma Export (C, u00044, "ada__finalizationS");
26409 pragma Export (C, u00045, "system__finalization_rootB");
26410 pragma Export (C, u00046, "system__finalization_rootS");
26411 pragma Export (C, u00047, "system__finalization_implementationB");
26412 pragma Export (C, u00048, "system__finalization_implementationS");
26413 pragma Export (C, u00049, "system__string_ops_concat_3B");
26414 pragma Export (C, u00050, "system__string_ops_concat_3S");
26415 pragma Export (C, u00051, "system__stream_attributesB");
26416 pragma Export (C, u00052, "system__stream_attributesS");
26417 pragma Export (C, u00053, "ada__io_exceptionsS");
26418 pragma Export (C, u00054, "system__unsigned_typesS");
26419 pragma Export (C, u00055, "system__file_control_blockS");
26420 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26421 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26423 -- BEGIN ELABORATION ORDER
26426 -- gnat.heap_sort_a (spec)
26427 -- gnat.heap_sort_a (body)
26428 -- gnat.htable (spec)
26429 -- gnat.htable (body)
26430 -- interfaces (spec)
26432 -- system.machine_code (spec)
26433 -- system.parameters (spec)
26434 -- system.parameters (body)
26435 -- interfaces.c_streams (spec)
26436 -- interfaces.c_streams (body)
26437 -- system.standard_library (spec)
26438 -- ada.exceptions (spec)
26439 -- system.exception_table (spec)
26440 -- system.exception_table (body)
26441 -- ada.io_exceptions (spec)
26442 -- system.exceptions (spec)
26443 -- system.storage_elements (spec)
26444 -- system.storage_elements (body)
26445 -- system.machine_state_operations (spec)
26446 -- system.machine_state_operations (body)
26447 -- system.secondary_stack (spec)
26448 -- system.stack_checking (spec)
26449 -- system.soft_links (spec)
26450 -- system.soft_links (body)
26451 -- system.stack_checking (body)
26452 -- system.secondary_stack (body)
26453 -- system.standard_library (body)
26454 -- system.string_ops (spec)
26455 -- system.string_ops (body)
26458 -- ada.streams (spec)
26459 -- system.finalization_root (spec)
26460 -- system.finalization_root (body)
26461 -- system.string_ops_concat_3 (spec)
26462 -- system.string_ops_concat_3 (body)
26463 -- system.traceback (spec)
26464 -- system.traceback (body)
26465 -- ada.exceptions (body)
26466 -- system.unsigned_types (spec)
26467 -- system.stream_attributes (spec)
26468 -- system.stream_attributes (body)
26469 -- system.finalization_implementation (spec)
26470 -- system.finalization_implementation (body)
26471 -- ada.finalization (spec)
26472 -- ada.finalization (body)
26473 -- ada.finalization.list_controller (spec)
26474 -- ada.finalization.list_controller (body)
26475 -- system.file_control_block (spec)
26476 -- system.file_io (spec)
26477 -- system.file_io (body)
26478 -- ada.text_io (spec)
26479 -- ada.text_io (body)
26481 -- END ELABORATION ORDER
26485 -- The following source file name pragmas allow the generated file
26486 -- names to be unique for different main programs. They are needed
26487 -- since the package name will always be Ada_Main.
26489 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26490 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26492 -- Generated package body for Ada_Main starts here
26494 package body ada_main is
26496 -- The actual finalization is performed by calling the
26497 -- library routine in System.Standard_Library.Adafinal
26499 procedure Do_Finalize;
26500 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26507 procedure adainit is
26509 -- These booleans are set to True once the associated unit has
26510 -- been elaborated. It is also used to avoid elaborating the
26511 -- same unit twice.
26514 pragma Import (Ada, E040, "interfaces__c_streams_E");
26517 pragma Import (Ada, E008, "ada__exceptions_E");
26520 pragma Import (Ada, E014, "system__exception_table_E");
26523 pragma Import (Ada, E053, "ada__io_exceptions_E");
26526 pragma Import (Ada, E017, "system__exceptions_E");
26529 pragma Import (Ada, E024, "system__secondary_stack_E");
26532 pragma Import (Ada, E030, "system__stack_checking_E");
26535 pragma Import (Ada, E028, "system__soft_links_E");
26538 pragma Import (Ada, E035, "ada__tags_E");
26541 pragma Import (Ada, E033, "ada__streams_E");
26544 pragma Import (Ada, E046, "system__finalization_root_E");
26547 pragma Import (Ada, E048, "system__finalization_implementation_E");
26550 pragma Import (Ada, E044, "ada__finalization_E");
26553 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26556 pragma Import (Ada, E055, "system__file_control_block_E");
26559 pragma Import (Ada, E042, "system__file_io_E");
26562 pragma Import (Ada, E006, "ada__text_io_E");
26564 -- Set_Globals is a library routine that stores away the
26565 -- value of the indicated set of global values in global
26566 -- variables within the library.
26568 procedure Set_Globals
26569 (Main_Priority : Integer;
26570 Time_Slice_Value : Integer;
26571 WC_Encoding : Character;
26572 Locking_Policy : Character;
26573 Queuing_Policy : Character;
26574 Task_Dispatching_Policy : Character;
26575 Adafinal : System.Address;
26576 Unreserve_All_Interrupts : Integer;
26577 Exception_Tracebacks : Integer);
26578 @findex __gnat_set_globals
26579 pragma Import (C, Set_Globals, "__gnat_set_globals");
26581 -- SDP_Table_Build is a library routine used to build the
26582 -- exception tables. See unit Ada.Exceptions in files
26583 -- a-except.ads/adb for full details of how zero cost
26584 -- exception handling works. This procedure, the call to
26585 -- it, and the two following tables are all omitted if the
26586 -- build is in longjmp/setjmp exception mode.
26588 @findex SDP_Table_Build
26589 @findex Zero Cost Exceptions
26590 procedure SDP_Table_Build
26591 (SDP_Addresses : System.Address;
26592 SDP_Count : Natural;
26593 Elab_Addresses : System.Address;
26594 Elab_Addr_Count : Natural);
26595 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26597 -- Table of Unit_Exception_Table addresses. Used for zero
26598 -- cost exception handling to build the top level table.
26600 ST : aliased constant array (1 .. 23) of System.Address := (
26602 Ada.Text_Io'UET_Address,
26603 Ada.Exceptions'UET_Address,
26604 Gnat.Heap_Sort_A'UET_Address,
26605 System.Exception_Table'UET_Address,
26606 System.Machine_State_Operations'UET_Address,
26607 System.Secondary_Stack'UET_Address,
26608 System.Parameters'UET_Address,
26609 System.Soft_Links'UET_Address,
26610 System.Stack_Checking'UET_Address,
26611 System.Traceback'UET_Address,
26612 Ada.Streams'UET_Address,
26613 Ada.Tags'UET_Address,
26614 System.String_Ops'UET_Address,
26615 Interfaces.C_Streams'UET_Address,
26616 System.File_Io'UET_Address,
26617 Ada.Finalization'UET_Address,
26618 System.Finalization_Root'UET_Address,
26619 System.Finalization_Implementation'UET_Address,
26620 System.String_Ops_Concat_3'UET_Address,
26621 System.Stream_Attributes'UET_Address,
26622 System.File_Control_Block'UET_Address,
26623 Ada.Finalization.List_Controller'UET_Address);
26625 -- Table of addresses of elaboration routines. Used for
26626 -- zero cost exception handling to make sure these
26627 -- addresses are included in the top level procedure
26630 EA : aliased constant array (1 .. 23) of System.Address := (
26631 adainit'Code_Address,
26632 Do_Finalize'Code_Address,
26633 Ada.Exceptions'Elab_Spec'Address,
26634 System.Exceptions'Elab_Spec'Address,
26635 Interfaces.C_Streams'Elab_Spec'Address,
26636 System.Exception_Table'Elab_Body'Address,
26637 Ada.Io_Exceptions'Elab_Spec'Address,
26638 System.Stack_Checking'Elab_Spec'Address,
26639 System.Soft_Links'Elab_Body'Address,
26640 System.Secondary_Stack'Elab_Body'Address,
26641 Ada.Tags'Elab_Spec'Address,
26642 Ada.Tags'Elab_Body'Address,
26643 Ada.Streams'Elab_Spec'Address,
26644 System.Finalization_Root'Elab_Spec'Address,
26645 Ada.Exceptions'Elab_Body'Address,
26646 System.Finalization_Implementation'Elab_Spec'Address,
26647 System.Finalization_Implementation'Elab_Body'Address,
26648 Ada.Finalization'Elab_Spec'Address,
26649 Ada.Finalization.List_Controller'Elab_Spec'Address,
26650 System.File_Control_Block'Elab_Spec'Address,
26651 System.File_Io'Elab_Body'Address,
26652 Ada.Text_Io'Elab_Spec'Address,
26653 Ada.Text_Io'Elab_Body'Address);
26655 -- Start of processing for adainit
26659 -- Call SDP_Table_Build to build the top level procedure
26660 -- table for zero cost exception handling (omitted in
26661 -- longjmp/setjmp mode).
26663 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
26665 -- Call Set_Globals to record various information for
26666 -- this partition. The values are derived by the binder
26667 -- from information stored in the ali files by the compiler.
26669 @findex __gnat_set_globals
26671 (Main_Priority => -1,
26672 -- Priority of main program, -1 if no pragma Priority used
26674 Time_Slice_Value => -1,
26675 -- Time slice from Time_Slice pragma, -1 if none used
26677 WC_Encoding => 'b',
26678 -- Wide_Character encoding used, default is brackets
26680 Locking_Policy => ' ',
26681 -- Locking_Policy used, default of space means not
26682 -- specified, otherwise it is the first character of
26683 -- the policy name.
26685 Queuing_Policy => ' ',
26686 -- Queuing_Policy used, default of space means not
26687 -- specified, otherwise it is the first character of
26688 -- the policy name.
26690 Task_Dispatching_Policy => ' ',
26691 -- Task_Dispatching_Policy used, default of space means
26692 -- not specified, otherwise first character of the
26695 Adafinal => System.Null_Address,
26696 -- Address of Adafinal routine, not used anymore
26698 Unreserve_All_Interrupts => 0,
26699 -- Set true if pragma Unreserve_All_Interrupts was used
26701 Exception_Tracebacks => 0);
26702 -- Indicates if exception tracebacks are enabled
26704 Elab_Final_Code := 1;
26706 -- Now we have the elaboration calls for all units in the partition.
26707 -- The Elab_Spec and Elab_Body attributes generate references to the
26708 -- implicit elaboration procedures generated by the compiler for
26709 -- each unit that requires elaboration.
26712 Interfaces.C_Streams'Elab_Spec;
26716 Ada.Exceptions'Elab_Spec;
26719 System.Exception_Table'Elab_Body;
26723 Ada.Io_Exceptions'Elab_Spec;
26727 System.Exceptions'Elab_Spec;
26731 System.Stack_Checking'Elab_Spec;
26734 System.Soft_Links'Elab_Body;
26739 System.Secondary_Stack'Elab_Body;
26743 Ada.Tags'Elab_Spec;
26746 Ada.Tags'Elab_Body;
26750 Ada.Streams'Elab_Spec;
26754 System.Finalization_Root'Elab_Spec;
26758 Ada.Exceptions'Elab_Body;
26762 System.Finalization_Implementation'Elab_Spec;
26765 System.Finalization_Implementation'Elab_Body;
26769 Ada.Finalization'Elab_Spec;
26773 Ada.Finalization.List_Controller'Elab_Spec;
26777 System.File_Control_Block'Elab_Spec;
26781 System.File_Io'Elab_Body;
26785 Ada.Text_Io'Elab_Spec;
26788 Ada.Text_Io'Elab_Body;
26792 Elab_Final_Code := 0;
26800 procedure adafinal is
26809 -- main is actually a function, as in the ANSI C standard,
26810 -- defined to return the exit status. The three parameters
26811 -- are the argument count, argument values and environment
26814 @findex Main Program
26817 argv : System.Address;
26818 envp : System.Address)
26821 -- The initialize routine performs low level system
26822 -- initialization using a standard library routine which
26823 -- sets up signal handling and performs any other
26824 -- required setup. The routine can be found in file
26827 @findex __gnat_initialize
26828 procedure initialize;
26829 pragma Import (C, initialize, "__gnat_initialize");
26831 -- The finalize routine performs low level system
26832 -- finalization using a standard library routine. The
26833 -- routine is found in file a-final.c and in the standard
26834 -- distribution is a dummy routine that does nothing, so
26835 -- really this is a hook for special user finalization.
26837 @findex __gnat_finalize
26838 procedure finalize;
26839 pragma Import (C, finalize, "__gnat_finalize");
26841 -- We get to the main program of the partition by using
26842 -- pragma Import because if we try to with the unit and
26843 -- call it Ada style, then not only do we waste time
26844 -- recompiling it, but also, we don't really know the right
26845 -- switches (e.g.@: identifier character set) to be used
26848 procedure Ada_Main_Program;
26849 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
26851 -- Start of processing for main
26854 -- Save global variables
26860 -- Call low level system initialization
26864 -- Call our generated Ada initialization routine
26868 -- This is the point at which we want the debugger to get
26873 -- Now we call the main program of the partition
26877 -- Perform Ada finalization
26881 -- Perform low level system finalization
26885 -- Return the proper exit status
26886 return (gnat_exit_status);
26889 -- This section is entirely comments, so it has no effect on the
26890 -- compilation of the Ada_Main package. It provides the list of
26891 -- object files and linker options, as well as some standard
26892 -- libraries needed for the link. The gnatlink utility parses
26893 -- this b~hello.adb file to read these comment lines to generate
26894 -- the appropriate command line arguments for the call to the
26895 -- system linker. The BEGIN/END lines are used for sentinels for
26896 -- this parsing operation.
26898 -- The exact file names will of course depend on the environment,
26899 -- host/target and location of files on the host system.
26901 @findex Object file list
26902 -- BEGIN Object file/option list
26905 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
26906 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
26907 -- END Object file/option list
26913 The Ada code in the above example is exactly what is generated by the
26914 binder. We have added comments to more clearly indicate the function
26915 of each part of the generated @code{Ada_Main} package.
26917 The code is standard Ada in all respects, and can be processed by any
26918 tools that handle Ada. In particular, it is possible to use the debugger
26919 in Ada mode to debug the generated @code{Ada_Main} package. For example,
26920 suppose that for reasons that you do not understand, your program is crashing
26921 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
26922 you can place a breakpoint on the call:
26924 @smallexample @c ada
26925 Ada.Text_Io'Elab_Body;
26929 and trace the elaboration routine for this package to find out where
26930 the problem might be (more usually of course you would be debugging
26931 elaboration code in your own application).
26933 @node Elaboration Order Handling in GNAT
26934 @appendix Elaboration Order Handling in GNAT
26935 @cindex Order of elaboration
26936 @cindex Elaboration control
26939 * Elaboration Code::
26940 * Checking the Elaboration Order::
26941 * Controlling the Elaboration Order::
26942 * Controlling Elaboration in GNAT - Internal Calls::
26943 * Controlling Elaboration in GNAT - External Calls::
26944 * Default Behavior in GNAT - Ensuring Safety::
26945 * Treatment of Pragma Elaborate::
26946 * Elaboration Issues for Library Tasks::
26947 * Mixing Elaboration Models::
26948 * What to Do If the Default Elaboration Behavior Fails::
26949 * Elaboration for Access-to-Subprogram Values::
26950 * Summary of Procedures for Elaboration Control::
26951 * Other Elaboration Order Considerations::
26955 This chapter describes the handling of elaboration code in Ada and
26956 in GNAT, and discusses how the order of elaboration of program units can
26957 be controlled in GNAT, either automatically or with explicit programming
26960 @node Elaboration Code
26961 @section Elaboration Code
26964 Ada provides rather general mechanisms for executing code at elaboration
26965 time, that is to say before the main program starts executing. Such code arises
26969 @item Initializers for variables.
26970 Variables declared at the library level, in package specs or bodies, can
26971 require initialization that is performed at elaboration time, as in:
26972 @smallexample @c ada
26974 Sqrt_Half : Float := Sqrt (0.5);
26978 @item Package initialization code
26979 Code in a @code{BEGIN-END} section at the outer level of a package body is
26980 executed as part of the package body elaboration code.
26982 @item Library level task allocators
26983 Tasks that are declared using task allocators at the library level
26984 start executing immediately and hence can execute at elaboration time.
26988 Subprogram calls are possible in any of these contexts, which means that
26989 any arbitrary part of the program may be executed as part of the elaboration
26990 code. It is even possible to write a program which does all its work at
26991 elaboration time, with a null main program, although stylistically this
26992 would usually be considered an inappropriate way to structure
26995 An important concern arises in the context of elaboration code:
26996 we have to be sure that it is executed in an appropriate order. What we
26997 have is a series of elaboration code sections, potentially one section
26998 for each unit in the program. It is important that these execute
26999 in the correct order. Correctness here means that, taking the above
27000 example of the declaration of @code{Sqrt_Half},
27001 if some other piece of
27002 elaboration code references @code{Sqrt_Half},
27003 then it must run after the
27004 section of elaboration code that contains the declaration of
27007 There would never be any order of elaboration problem if we made a rule
27008 that whenever you @code{with} a unit, you must elaborate both the spec and body
27009 of that unit before elaborating the unit doing the @code{with}'ing:
27011 @smallexample @c ada
27015 package Unit_2 is @dots{}
27021 would require that both the body and spec of @code{Unit_1} be elaborated
27022 before the spec of @code{Unit_2}. However, a rule like that would be far too
27023 restrictive. In particular, it would make it impossible to have routines
27024 in separate packages that were mutually recursive.
27026 You might think that a clever enough compiler could look at the actual
27027 elaboration code and determine an appropriate correct order of elaboration,
27028 but in the general case, this is not possible. Consider the following
27031 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27033 the variable @code{Sqrt_1}, which is declared in the elaboration code
27034 of the body of @code{Unit_1}:
27036 @smallexample @c ada
27038 Sqrt_1 : Float := Sqrt (0.1);
27043 The elaboration code of the body of @code{Unit_1} also contains:
27045 @smallexample @c ada
27048 if expression_1 = 1 then
27049 Q := Unit_2.Func_2;
27056 @code{Unit_2} is exactly parallel,
27057 it has a procedure @code{Func_2} that references
27058 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27059 the body @code{Unit_2}:
27061 @smallexample @c ada
27063 Sqrt_2 : Float := Sqrt (0.1);
27068 The elaboration code of the body of @code{Unit_2} also contains:
27070 @smallexample @c ada
27073 if expression_2 = 2 then
27074 Q := Unit_1.Func_1;
27081 Now the question is, which of the following orders of elaboration is
27106 If you carefully analyze the flow here, you will see that you cannot tell
27107 at compile time the answer to this question.
27108 If @code{expression_1} is not equal to 1,
27109 and @code{expression_2} is not equal to 2,
27110 then either order is acceptable, because neither of the function calls is
27111 executed. If both tests evaluate to true, then neither order is acceptable
27112 and in fact there is no correct order.
27114 If one of the two expressions is true, and the other is false, then one
27115 of the above orders is correct, and the other is incorrect. For example,
27116 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27117 then the call to @code{Func_1}
27118 will occur, but not the call to @code{Func_2.}
27119 This means that it is essential
27120 to elaborate the body of @code{Unit_1} before
27121 the body of @code{Unit_2}, so the first
27122 order of elaboration is correct and the second is wrong.
27124 By making @code{expression_1} and @code{expression_2}
27125 depend on input data, or perhaps
27126 the time of day, we can make it impossible for the compiler or binder
27127 to figure out which of these expressions will be true, and hence it
27128 is impossible to guarantee a safe order of elaboration at run time.
27130 @node Checking the Elaboration Order
27131 @section Checking the Elaboration Order
27134 In some languages that involve the same kind of elaboration problems,
27135 e.g.@: Java and C++, the programmer is expected to worry about these
27136 ordering problems himself, and it is common to
27137 write a program in which an incorrect elaboration order gives
27138 surprising results, because it references variables before they
27140 Ada is designed to be a safe language, and a programmer-beware approach is
27141 clearly not sufficient. Consequently, the language provides three lines
27145 @item Standard rules
27146 Some standard rules restrict the possible choice of elaboration
27147 order. In particular, if you @code{with} a unit, then its spec is always
27148 elaborated before the unit doing the @code{with}. Similarly, a parent
27149 spec is always elaborated before the child spec, and finally
27150 a spec is always elaborated before its corresponding body.
27152 @item Dynamic elaboration checks
27153 @cindex Elaboration checks
27154 @cindex Checks, elaboration
27155 Dynamic checks are made at run time, so that if some entity is accessed
27156 before it is elaborated (typically by means of a subprogram call)
27157 then the exception (@code{Program_Error}) is raised.
27159 @item Elaboration control
27160 Facilities are provided for the programmer to specify the desired order
27164 Let's look at these facilities in more detail. First, the rules for
27165 dynamic checking. One possible rule would be simply to say that the
27166 exception is raised if you access a variable which has not yet been
27167 elaborated. The trouble with this approach is that it could require
27168 expensive checks on every variable reference. Instead Ada has two
27169 rules which are a little more restrictive, but easier to check, and
27173 @item Restrictions on calls
27174 A subprogram can only be called at elaboration time if its body
27175 has been elaborated. The rules for elaboration given above guarantee
27176 that the spec of the subprogram has been elaborated before the
27177 call, but not the body. If this rule is violated, then the
27178 exception @code{Program_Error} is raised.
27180 @item Restrictions on instantiations
27181 A generic unit can only be instantiated if the body of the generic
27182 unit has been elaborated. Again, the rules for elaboration given above
27183 guarantee that the spec of the generic unit has been elaborated
27184 before the instantiation, but not the body. If this rule is
27185 violated, then the exception @code{Program_Error} is raised.
27189 The idea is that if the body has been elaborated, then any variables
27190 it references must have been elaborated; by checking for the body being
27191 elaborated we guarantee that none of its references causes any
27192 trouble. As we noted above, this is a little too restrictive, because a
27193 subprogram that has no non-local references in its body may in fact be safe
27194 to call. However, it really would be unsafe to rely on this, because
27195 it would mean that the caller was aware of details of the implementation
27196 in the body. This goes against the basic tenets of Ada.
27198 A plausible implementation can be described as follows.
27199 A Boolean variable is associated with each subprogram
27200 and each generic unit. This variable is initialized to False, and is set to
27201 True at the point body is elaborated. Every call or instantiation checks the
27202 variable, and raises @code{Program_Error} if the variable is False.
27204 Note that one might think that it would be good enough to have one Boolean
27205 variable for each package, but that would not deal with cases of trying
27206 to call a body in the same package as the call
27207 that has not been elaborated yet.
27208 Of course a compiler may be able to do enough analysis to optimize away
27209 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27210 does such optimizations, but still the easiest conceptual model is to
27211 think of there being one variable per subprogram.
27213 @node Controlling the Elaboration Order
27214 @section Controlling the Elaboration Order
27217 In the previous section we discussed the rules in Ada which ensure
27218 that @code{Program_Error} is raised if an incorrect elaboration order is
27219 chosen. This prevents erroneous executions, but we need mechanisms to
27220 specify a correct execution and avoid the exception altogether.
27221 To achieve this, Ada provides a number of features for controlling
27222 the order of elaboration. We discuss these features in this section.
27224 First, there are several ways of indicating to the compiler that a given
27225 unit has no elaboration problems:
27228 @item packages that do not require a body
27229 A library package that does not require a body does not permit
27230 a body (this rule was introduced in Ada 95).
27231 Thus if we have a such a package, as in:
27233 @smallexample @c ada
27236 package Definitions is
27238 type m is new integer;
27240 type a is array (1 .. 10) of m;
27241 type b is array (1 .. 20) of m;
27249 A package that @code{with}'s @code{Definitions} may safely instantiate
27250 @code{Definitions.Subp} because the compiler can determine that there
27251 definitely is no package body to worry about in this case
27254 @cindex pragma Pure
27256 Places sufficient restrictions on a unit to guarantee that
27257 no call to any subprogram in the unit can result in an
27258 elaboration problem. This means that the compiler does not need
27259 to worry about the point of elaboration of such units, and in
27260 particular, does not need to check any calls to any subprograms
27263 @item pragma Preelaborate
27264 @findex Preelaborate
27265 @cindex pragma Preelaborate
27266 This pragma places slightly less stringent restrictions on a unit than
27268 but these restrictions are still sufficient to ensure that there
27269 are no elaboration problems with any calls to the unit.
27271 @item pragma Elaborate_Body
27272 @findex Elaborate_Body
27273 @cindex pragma Elaborate_Body
27274 This pragma requires that the body of a unit be elaborated immediately
27275 after its spec. Suppose a unit @code{A} has such a pragma,
27276 and unit @code{B} does
27277 a @code{with} of unit @code{A}. Recall that the standard rules require
27278 the spec of unit @code{A}
27279 to be elaborated before the @code{with}'ing unit; given the pragma in
27280 @code{A}, we also know that the body of @code{A}
27281 will be elaborated before @code{B}, so
27282 that calls to @code{A} are safe and do not need a check.
27287 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27289 @code{Elaborate_Body} does not guarantee that the program is
27290 free of elaboration problems, because it may not be possible
27291 to satisfy the requested elaboration order.
27292 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27294 marks @code{Unit_1} as @code{Elaborate_Body},
27295 and not @code{Unit_2,} then the order of
27296 elaboration will be:
27308 Now that means that the call to @code{Func_1} in @code{Unit_2}
27309 need not be checked,
27310 it must be safe. But the call to @code{Func_2} in
27311 @code{Unit_1} may still fail if
27312 @code{Expression_1} is equal to 1,
27313 and the programmer must still take
27314 responsibility for this not being the case.
27316 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27317 eliminated, except for calls entirely within a body, which are
27318 in any case fully under programmer control. However, using the pragma
27319 everywhere is not always possible.
27320 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27321 we marked both of them as having pragma @code{Elaborate_Body}, then
27322 clearly there would be no possible elaboration order.
27324 The above pragmas allow a server to guarantee safe use by clients, and
27325 clearly this is the preferable approach. Consequently a good rule
27326 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27327 and if this is not possible,
27328 mark them as @code{Elaborate_Body} if possible.
27329 As we have seen, there are situations where neither of these
27330 three pragmas can be used.
27331 So we also provide methods for clients to control the
27332 order of elaboration of the servers on which they depend:
27335 @item pragma Elaborate (unit)
27337 @cindex pragma Elaborate
27338 This pragma is placed in the context clause, after a @code{with} clause,
27339 and it requires that the body of the named unit be elaborated before
27340 the unit in which the pragma occurs. The idea is to use this pragma
27341 if the current unit calls at elaboration time, directly or indirectly,
27342 some subprogram in the named unit.
27344 @item pragma Elaborate_All (unit)
27345 @findex Elaborate_All
27346 @cindex pragma Elaborate_All
27347 This is a stronger version of the Elaborate pragma. Consider the
27351 Unit A @code{with}'s unit B and calls B.Func in elab code
27352 Unit B @code{with}'s unit C, and B.Func calls C.Func
27356 Now if we put a pragma @code{Elaborate (B)}
27357 in unit @code{A}, this ensures that the
27358 body of @code{B} is elaborated before the call, but not the
27359 body of @code{C}, so
27360 the call to @code{C.Func} could still cause @code{Program_Error} to
27363 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27364 not only that the body of the named unit be elaborated before the
27365 unit doing the @code{with}, but also the bodies of all units that the
27366 named unit uses, following @code{with} links transitively. For example,
27367 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27369 not only that the body of @code{B} be elaborated before @code{A},
27371 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27375 We are now in a position to give a usage rule in Ada for avoiding
27376 elaboration problems, at least if dynamic dispatching and access to
27377 subprogram values are not used. We will handle these cases separately
27380 The rule is simple. If a unit has elaboration code that can directly or
27381 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27382 a generic package in a @code{with}'ed unit,
27383 then if the @code{with}'ed unit does not have
27384 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27385 a pragma @code{Elaborate_All}
27386 for the @code{with}'ed unit. By following this rule a client is
27387 assured that calls can be made without risk of an exception.
27389 For generic subprogram instantiations, the rule can be relaxed to
27390 require only a pragma @code{Elaborate} since elaborating the body
27391 of a subprogram cannot cause any transitive elaboration (we are
27392 not calling the subprogram in this case, just elaborating its
27395 If this rule is not followed, then a program may be in one of four
27399 @item No order exists
27400 No order of elaboration exists which follows the rules, taking into
27401 account any @code{Elaborate}, @code{Elaborate_All},
27402 or @code{Elaborate_Body} pragmas. In
27403 this case, an Ada compiler must diagnose the situation at bind
27404 time, and refuse to build an executable program.
27406 @item One or more orders exist, all incorrect
27407 One or more acceptable elaboration orders exist, and all of them
27408 generate an elaboration order problem. In this case, the binder
27409 can build an executable program, but @code{Program_Error} will be raised
27410 when the program is run.
27412 @item Several orders exist, some right, some incorrect
27413 One or more acceptable elaboration orders exists, and some of them
27414 work, and some do not. The programmer has not controlled
27415 the order of elaboration, so the binder may or may not pick one of
27416 the correct orders, and the program may or may not raise an
27417 exception when it is run. This is the worst case, because it means
27418 that the program may fail when moved to another compiler, or even
27419 another version of the same compiler.
27421 @item One or more orders exists, all correct
27422 One ore more acceptable elaboration orders exist, and all of them
27423 work. In this case the program runs successfully. This state of
27424 affairs can be guaranteed by following the rule we gave above, but
27425 may be true even if the rule is not followed.
27429 Note that one additional advantage of following our rules on the use
27430 of @code{Elaborate} and @code{Elaborate_All}
27431 is that the program continues to stay in the ideal (all orders OK) state
27432 even if maintenance
27433 changes some bodies of some units. Conversely, if a program that does
27434 not follow this rule happens to be safe at some point, this state of affairs
27435 may deteriorate silently as a result of maintenance changes.
27437 You may have noticed that the above discussion did not mention
27438 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27439 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27440 code in the body makes calls to some other unit, so it is still necessary
27441 to use @code{Elaborate_All} on such units.
27443 @node Controlling Elaboration in GNAT - Internal Calls
27444 @section Controlling Elaboration in GNAT - Internal Calls
27447 In the case of internal calls, i.e., calls within a single package, the
27448 programmer has full control over the order of elaboration, and it is up
27449 to the programmer to elaborate declarations in an appropriate order. For
27452 @smallexample @c ada
27455 function One return Float;
27459 function One return Float is
27468 will obviously raise @code{Program_Error} at run time, because function
27469 One will be called before its body is elaborated. In this case GNAT will
27470 generate a warning that the call will raise @code{Program_Error}:
27476 2. function One return Float;
27478 4. Q : Float := One;
27480 >>> warning: cannot call "One" before body is elaborated
27481 >>> warning: Program_Error will be raised at run time
27484 6. function One return Float is
27497 Note that in this particular case, it is likely that the call is safe, because
27498 the function @code{One} does not access any global variables.
27499 Nevertheless in Ada, we do not want the validity of the check to depend on
27500 the contents of the body (think about the separate compilation case), so this
27501 is still wrong, as we discussed in the previous sections.
27503 The error is easily corrected by rearranging the declarations so that the
27504 body of @code{One} appears before the declaration containing the call
27505 (note that in Ada 95 and Ada 2005,
27506 declarations can appear in any order, so there is no restriction that
27507 would prevent this reordering, and if we write:
27509 @smallexample @c ada
27512 function One return Float;
27514 function One return Float is
27525 then all is well, no warning is generated, and no
27526 @code{Program_Error} exception
27528 Things are more complicated when a chain of subprograms is executed:
27530 @smallexample @c ada
27533 function A return Integer;
27534 function B return Integer;
27535 function C return Integer;
27537 function B return Integer is begin return A; end;
27538 function C return Integer is begin return B; end;
27542 function A return Integer is begin return 1; end;
27548 Now the call to @code{C}
27549 at elaboration time in the declaration of @code{X} is correct, because
27550 the body of @code{C} is already elaborated,
27551 and the call to @code{B} within the body of
27552 @code{C} is correct, but the call
27553 to @code{A} within the body of @code{B} is incorrect, because the body
27554 of @code{A} has not been elaborated, so @code{Program_Error}
27555 will be raised on the call to @code{A}.
27556 In this case GNAT will generate a
27557 warning that @code{Program_Error} may be
27558 raised at the point of the call. Let's look at the warning:
27564 2. function A return Integer;
27565 3. function B return Integer;
27566 4. function C return Integer;
27568 6. function B return Integer is begin return A; end;
27570 >>> warning: call to "A" before body is elaborated may
27571 raise Program_Error
27572 >>> warning: "B" called at line 7
27573 >>> warning: "C" called at line 9
27575 7. function C return Integer is begin return B; end;
27577 9. X : Integer := C;
27579 11. function A return Integer is begin return 1; end;
27589 Note that the message here says ``may raise'', instead of the direct case,
27590 where the message says ``will be raised''. That's because whether
27592 actually called depends in general on run-time flow of control.
27593 For example, if the body of @code{B} said
27595 @smallexample @c ada
27598 function B return Integer is
27600 if some-condition-depending-on-input-data then
27611 then we could not know until run time whether the incorrect call to A would
27612 actually occur, so @code{Program_Error} might
27613 or might not be raised. It is possible for a compiler to
27614 do a better job of analyzing bodies, to
27615 determine whether or not @code{Program_Error}
27616 might be raised, but it certainly
27617 couldn't do a perfect job (that would require solving the halting problem
27618 and is provably impossible), and because this is a warning anyway, it does
27619 not seem worth the effort to do the analysis. Cases in which it
27620 would be relevant are rare.
27622 In practice, warnings of either of the forms given
27623 above will usually correspond to
27624 real errors, and should be examined carefully and eliminated.
27625 In the rare case where a warning is bogus, it can be suppressed by any of
27626 the following methods:
27630 Compile with the @option{-gnatws} switch set
27633 Suppress @code{Elaboration_Check} for the called subprogram
27636 Use pragma @code{Warnings_Off} to turn warnings off for the call
27640 For the internal elaboration check case,
27641 GNAT by default generates the
27642 necessary run-time checks to ensure
27643 that @code{Program_Error} is raised if any
27644 call fails an elaboration check. Of course this can only happen if a
27645 warning has been issued as described above. The use of pragma
27646 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
27647 some of these checks, meaning that it may be possible (but is not
27648 guaranteed) for a program to be able to call a subprogram whose body
27649 is not yet elaborated, without raising a @code{Program_Error} exception.
27651 @node Controlling Elaboration in GNAT - External Calls
27652 @section Controlling Elaboration in GNAT - External Calls
27655 The previous section discussed the case in which the execution of a
27656 particular thread of elaboration code occurred entirely within a
27657 single unit. This is the easy case to handle, because a programmer
27658 has direct and total control over the order of elaboration, and
27659 furthermore, checks need only be generated in cases which are rare
27660 and which the compiler can easily detect.
27661 The situation is more complex when separate compilation is taken into account.
27662 Consider the following:
27664 @smallexample @c ada
27668 function Sqrt (Arg : Float) return Float;
27671 package body Math is
27672 function Sqrt (Arg : Float) return Float is
27681 X : Float := Math.Sqrt (0.5);
27694 where @code{Main} is the main program. When this program is executed, the
27695 elaboration code must first be executed, and one of the jobs of the
27696 binder is to determine the order in which the units of a program are
27697 to be elaborated. In this case we have four units: the spec and body
27699 the spec of @code{Stuff} and the body of @code{Main}).
27700 In what order should the four separate sections of elaboration code
27703 There are some restrictions in the order of elaboration that the binder
27704 can choose. In particular, if unit U has a @code{with}
27705 for a package @code{X}, then you
27706 are assured that the spec of @code{X}
27707 is elaborated before U , but you are
27708 not assured that the body of @code{X}
27709 is elaborated before U.
27710 This means that in the above case, the binder is allowed to choose the
27721 but that's not good, because now the call to @code{Math.Sqrt}
27722 that happens during
27723 the elaboration of the @code{Stuff}
27724 spec happens before the body of @code{Math.Sqrt} is
27725 elaborated, and hence causes @code{Program_Error} exception to be raised.
27726 At first glance, one might say that the binder is misbehaving, because
27727 obviously you want to elaborate the body of something you @code{with}
27729 that is not a general rule that can be followed in all cases. Consider
27731 @smallexample @c ada
27734 package X is @dots{}
27736 package Y is @dots{}
27739 package body Y is @dots{}
27742 package body X is @dots{}
27748 This is a common arrangement, and, apart from the order of elaboration
27749 problems that might arise in connection with elaboration code, this works fine.
27750 A rule that says that you must first elaborate the body of anything you
27751 @code{with} cannot work in this case:
27752 the body of @code{X} @code{with}'s @code{Y},
27753 which means you would have to
27754 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
27756 you have to elaborate the body of @code{X} first, but @dots{} and we have a
27757 loop that cannot be broken.
27759 It is true that the binder can in many cases guess an order of elaboration
27760 that is unlikely to cause a @code{Program_Error}
27761 exception to be raised, and it tries to do so (in the
27762 above example of @code{Math/Stuff/Spec}, the GNAT binder will
27764 elaborate the body of @code{Math} right after its spec, so all will be well).
27766 However, a program that blindly relies on the binder to be helpful can
27767 get into trouble, as we discussed in the previous sections, so
27769 provides a number of facilities for assisting the programmer in
27770 developing programs that are robust with respect to elaboration order.
27772 @node Default Behavior in GNAT - Ensuring Safety
27773 @section Default Behavior in GNAT - Ensuring Safety
27776 The default behavior in GNAT ensures elaboration safety. In its
27777 default mode GNAT implements the
27778 rule we previously described as the right approach. Let's restate it:
27782 @emph{If a unit has elaboration code that can directly or indirectly make a
27783 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
27784 package in a @code{with}'ed unit, then if the @code{with}'ed unit
27785 does not have pragma @code{Pure} or
27786 @code{Preelaborate}, then the client should have an
27787 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
27789 @emph{In the case of instantiating a generic subprogram, it is always
27790 sufficient to have only an @code{Elaborate} pragma for the
27791 @code{with}'ed unit.}
27795 By following this rule a client is assured that calls and instantiations
27796 can be made without risk of an exception.
27798 In this mode GNAT traces all calls that are potentially made from
27799 elaboration code, and puts in any missing implicit @code{Elaborate}
27800 and @code{Elaborate_All} pragmas.
27801 The advantage of this approach is that no elaboration problems
27802 are possible if the binder can find an elaboration order that is
27803 consistent with these implicit @code{Elaborate} and
27804 @code{Elaborate_All} pragmas. The
27805 disadvantage of this approach is that no such order may exist.
27807 If the binder does not generate any diagnostics, then it means that it has
27808 found an elaboration order that is guaranteed to be safe. However, the binder
27809 may still be relying on implicitly generated @code{Elaborate} and
27810 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
27813 If it is important to guarantee portability, then the compilations should
27816 (warn on elaboration problems) switch. This will cause warning messages
27817 to be generated indicating the missing @code{Elaborate} and
27818 @code{Elaborate_All} pragmas.
27819 Consider the following source program:
27821 @smallexample @c ada
27826 m : integer := k.r;
27833 where it is clear that there
27834 should be a pragma @code{Elaborate_All}
27835 for unit @code{k}. An implicit pragma will be generated, and it is
27836 likely that the binder will be able to honor it. However, if you want
27837 to port this program to some other Ada compiler than GNAT.
27838 it is safer to include the pragma explicitly in the source. If this
27839 unit is compiled with the
27841 switch, then the compiler outputs a warning:
27848 3. m : integer := k.r;
27850 >>> warning: call to "r" may raise Program_Error
27851 >>> warning: missing pragma Elaborate_All for "k"
27859 and these warnings can be used as a guide for supplying manually
27860 the missing pragmas. It is usually a bad idea to use this warning
27861 option during development. That's because it will warn you when
27862 you need to put in a pragma, but cannot warn you when it is time
27863 to take it out. So the use of pragma @code{Elaborate_All} may lead to
27864 unnecessary dependencies and even false circularities.
27866 This default mode is more restrictive than the Ada Reference
27867 Manual, and it is possible to construct programs which will compile
27868 using the dynamic model described there, but will run into a
27869 circularity using the safer static model we have described.
27871 Of course any Ada compiler must be able to operate in a mode
27872 consistent with the requirements of the Ada Reference Manual,
27873 and in particular must have the capability of implementing the
27874 standard dynamic model of elaboration with run-time checks.
27876 In GNAT, this standard mode can be achieved either by the use of
27877 the @option{-gnatE} switch on the compiler (@command{gcc} or
27878 @command{gnatmake}) command, or by the use of the configuration pragma:
27880 @smallexample @c ada
27881 pragma Elaboration_Checks (RM);
27885 Either approach will cause the unit affected to be compiled using the
27886 standard dynamic run-time elaboration checks described in the Ada
27887 Reference Manual. The static model is generally preferable, since it
27888 is clearly safer to rely on compile and link time checks rather than
27889 run-time checks. However, in the case of legacy code, it may be
27890 difficult to meet the requirements of the static model. This
27891 issue is further discussed in
27892 @ref{What to Do If the Default Elaboration Behavior Fails}.
27894 Note that the static model provides a strict subset of the allowed
27895 behavior and programs of the Ada Reference Manual, so if you do
27896 adhere to the static model and no circularities exist,
27897 then you are assured that your program will
27898 work using the dynamic model, providing that you remove any
27899 pragma Elaborate statements from the source.
27901 @node Treatment of Pragma Elaborate
27902 @section Treatment of Pragma Elaborate
27903 @cindex Pragma Elaborate
27906 The use of @code{pragma Elaborate}
27907 should generally be avoided in Ada 95 and Ada 2005 programs,
27908 since there is no guarantee that transitive calls
27909 will be properly handled. Indeed at one point, this pragma was placed
27910 in Annex J (Obsolescent Features), on the grounds that it is never useful.
27912 Now that's a bit restrictive. In practice, the case in which
27913 @code{pragma Elaborate} is useful is when the caller knows that there
27914 are no transitive calls, or that the called unit contains all necessary
27915 transitive @code{pragma Elaborate} statements, and legacy code often
27916 contains such uses.
27918 Strictly speaking the static mode in GNAT should ignore such pragmas,
27919 since there is no assurance at compile time that the necessary safety
27920 conditions are met. In practice, this would cause GNAT to be incompatible
27921 with correctly written Ada 83 code that had all necessary
27922 @code{pragma Elaborate} statements in place. Consequently, we made the
27923 decision that GNAT in its default mode will believe that if it encounters
27924 a @code{pragma Elaborate} then the programmer knows what they are doing,
27925 and it will trust that no elaboration errors can occur.
27927 The result of this decision is two-fold. First to be safe using the
27928 static mode, you should remove all @code{pragma Elaborate} statements.
27929 Second, when fixing circularities in existing code, you can selectively
27930 use @code{pragma Elaborate} statements to convince the static mode of
27931 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
27934 When using the static mode with @option{-gnatwl}, any use of
27935 @code{pragma Elaborate} will generate a warning about possible
27938 @node Elaboration Issues for Library Tasks
27939 @section Elaboration Issues for Library Tasks
27940 @cindex Library tasks, elaboration issues
27941 @cindex Elaboration of library tasks
27944 In this section we examine special elaboration issues that arise for
27945 programs that declare library level tasks.
27947 Generally the model of execution of an Ada program is that all units are
27948 elaborated, and then execution of the program starts. However, the
27949 declaration of library tasks definitely does not fit this model. The
27950 reason for this is that library tasks start as soon as they are declared
27951 (more precisely, as soon as the statement part of the enclosing package
27952 body is reached), that is to say before elaboration
27953 of the program is complete. This means that if such a task calls a
27954 subprogram, or an entry in another task, the callee may or may not be
27955 elaborated yet, and in the standard
27956 Reference Manual model of dynamic elaboration checks, you can even
27957 get timing dependent Program_Error exceptions, since there can be
27958 a race between the elaboration code and the task code.
27960 The static model of elaboration in GNAT seeks to avoid all such
27961 dynamic behavior, by being conservative, and the conservative
27962 approach in this particular case is to assume that all the code
27963 in a task body is potentially executed at elaboration time if
27964 a task is declared at the library level.
27966 This can definitely result in unexpected circularities. Consider
27967 the following example
27969 @smallexample @c ada
27975 type My_Int is new Integer;
27977 function Ident (M : My_Int) return My_Int;
27981 package body Decls is
27982 task body Lib_Task is
27988 function Ident (M : My_Int) return My_Int is
27996 procedure Put_Val (Arg : Decls.My_Int);
28000 package body Utils is
28001 procedure Put_Val (Arg : Decls.My_Int) is
28003 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28010 Decls.Lib_Task.Start;
28015 If the above example is compiled in the default static elaboration
28016 mode, then a circularity occurs. The circularity comes from the call
28017 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28018 this call occurs in elaboration code, we need an implicit pragma
28019 @code{Elaborate_All} for @code{Utils}. This means that not only must
28020 the spec and body of @code{Utils} be elaborated before the body
28021 of @code{Decls}, but also the spec and body of any unit that is
28022 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28023 the body of @code{Decls}. This is the transitive implication of
28024 pragma @code{Elaborate_All} and it makes sense, because in general
28025 the body of @code{Put_Val} might have a call to something in a
28026 @code{with'ed} unit.
28028 In this case, the body of Utils (actually its spec) @code{with's}
28029 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28030 must be elaborated before itself, in case there is a call from the
28031 body of @code{Utils}.
28033 Here is the exact chain of events we are worrying about:
28037 In the body of @code{Decls} a call is made from within the body of a library
28038 task to a subprogram in the package @code{Utils}. Since this call may
28039 occur at elaboration time (given that the task is activated at elaboration
28040 time), we have to assume the worst, i.e., that the
28041 call does happen at elaboration time.
28044 This means that the body and spec of @code{Util} must be elaborated before
28045 the body of @code{Decls} so that this call does not cause an access before
28049 Within the body of @code{Util}, specifically within the body of
28050 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28054 One such @code{with}'ed package is package @code{Decls}, so there
28055 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28056 In fact there is such a call in this example, but we would have to
28057 assume that there was such a call even if it were not there, since
28058 we are not supposed to write the body of @code{Decls} knowing what
28059 is in the body of @code{Utils}; certainly in the case of the
28060 static elaboration model, the compiler does not know what is in
28061 other bodies and must assume the worst.
28064 This means that the spec and body of @code{Decls} must also be
28065 elaborated before we elaborate the unit containing the call, but
28066 that unit is @code{Decls}! This means that the body of @code{Decls}
28067 must be elaborated before itself, and that's a circularity.
28071 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28072 the body of @code{Decls} you will get a true Ada Reference Manual
28073 circularity that makes the program illegal.
28075 In practice, we have found that problems with the static model of
28076 elaboration in existing code often arise from library tasks, so
28077 we must address this particular situation.
28079 Note that if we compile and run the program above, using the dynamic model of
28080 elaboration (that is to say use the @option{-gnatE} switch),
28081 then it compiles, binds,
28082 links, and runs, printing the expected result of 2. Therefore in some sense
28083 the circularity here is only apparent, and we need to capture
28084 the properties of this program that distinguish it from other library-level
28085 tasks that have real elaboration problems.
28087 We have four possible answers to this question:
28092 Use the dynamic model of elaboration.
28094 If we use the @option{-gnatE} switch, then as noted above, the program works.
28095 Why is this? If we examine the task body, it is apparent that the task cannot
28097 @code{accept} statement until after elaboration has been completed, because
28098 the corresponding entry call comes from the main program, not earlier.
28099 This is why the dynamic model works here. But that's really giving
28100 up on a precise analysis, and we prefer to take this approach only if we cannot
28102 problem in any other manner. So let us examine two ways to reorganize
28103 the program to avoid the potential elaboration problem.
28106 Split library tasks into separate packages.
28108 Write separate packages, so that library tasks are isolated from
28109 other declarations as much as possible. Let us look at a variation on
28112 @smallexample @c ada
28120 package body Decls1 is
28121 task body Lib_Task is
28129 type My_Int is new Integer;
28130 function Ident (M : My_Int) return My_Int;
28134 package body Decls2 is
28135 function Ident (M : My_Int) return My_Int is
28143 procedure Put_Val (Arg : Decls2.My_Int);
28147 package body Utils is
28148 procedure Put_Val (Arg : Decls2.My_Int) is
28150 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28157 Decls1.Lib_Task.Start;
28162 All we have done is to split @code{Decls} into two packages, one
28163 containing the library task, and one containing everything else. Now
28164 there is no cycle, and the program compiles, binds, links and executes
28165 using the default static model of elaboration.
28168 Declare separate task types.
28170 A significant part of the problem arises because of the use of the
28171 single task declaration form. This means that the elaboration of
28172 the task type, and the elaboration of the task itself (i.e.@: the
28173 creation of the task) happen at the same time. A good rule
28174 of style in Ada is to always create explicit task types. By
28175 following the additional step of placing task objects in separate
28176 packages from the task type declaration, many elaboration problems
28177 are avoided. Here is another modified example of the example program:
28179 @smallexample @c ada
28181 task type Lib_Task_Type is
28185 type My_Int is new Integer;
28187 function Ident (M : My_Int) return My_Int;
28191 package body Decls is
28192 task body Lib_Task_Type is
28198 function Ident (M : My_Int) return My_Int is
28206 procedure Put_Val (Arg : Decls.My_Int);
28210 package body Utils is
28211 procedure Put_Val (Arg : Decls.My_Int) is
28213 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28219 Lib_Task : Decls.Lib_Task_Type;
28225 Declst.Lib_Task.Start;
28230 What we have done here is to replace the @code{task} declaration in
28231 package @code{Decls} with a @code{task type} declaration. Then we
28232 introduce a separate package @code{Declst} to contain the actual
28233 task object. This separates the elaboration issues for
28234 the @code{task type}
28235 declaration, which causes no trouble, from the elaboration issues
28236 of the task object, which is also unproblematic, since it is now independent
28237 of the elaboration of @code{Utils}.
28238 This separation of concerns also corresponds to
28239 a generally sound engineering principle of separating declarations
28240 from instances. This version of the program also compiles, binds, links,
28241 and executes, generating the expected output.
28244 Use No_Entry_Calls_In_Elaboration_Code restriction.
28245 @cindex No_Entry_Calls_In_Elaboration_Code
28247 The previous two approaches described how a program can be restructured
28248 to avoid the special problems caused by library task bodies. in practice,
28249 however, such restructuring may be difficult to apply to existing legacy code,
28250 so we must consider solutions that do not require massive rewriting.
28252 Let us consider more carefully why our original sample program works
28253 under the dynamic model of elaboration. The reason is that the code
28254 in the task body blocks immediately on the @code{accept}
28255 statement. Now of course there is nothing to prohibit elaboration
28256 code from making entry calls (for example from another library level task),
28257 so we cannot tell in isolation that
28258 the task will not execute the accept statement during elaboration.
28260 However, in practice it is very unusual to see elaboration code
28261 make any entry calls, and the pattern of tasks starting
28262 at elaboration time and then immediately blocking on @code{accept} or
28263 @code{select} statements is very common. What this means is that
28264 the compiler is being too pessimistic when it analyzes the
28265 whole package body as though it might be executed at elaboration
28268 If we know that the elaboration code contains no entry calls, (a very safe
28269 assumption most of the time, that could almost be made the default
28270 behavior), then we can compile all units of the program under control
28271 of the following configuration pragma:
28274 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28278 This pragma can be placed in the @file{gnat.adc} file in the usual
28279 manner. If we take our original unmodified program and compile it
28280 in the presence of a @file{gnat.adc} containing the above pragma,
28281 then once again, we can compile, bind, link, and execute, obtaining
28282 the expected result. In the presence of this pragma, the compiler does
28283 not trace calls in a task body, that appear after the first @code{accept}
28284 or @code{select} statement, and therefore does not report a potential
28285 circularity in the original program.
28287 The compiler will check to the extent it can that the above
28288 restriction is not violated, but it is not always possible to do a
28289 complete check at compile time, so it is important to use this
28290 pragma only if the stated restriction is in fact met, that is to say
28291 no task receives an entry call before elaboration of all units is completed.
28295 @node Mixing Elaboration Models
28296 @section Mixing Elaboration Models
28298 So far, we have assumed that the entire program is either compiled
28299 using the dynamic model or static model, ensuring consistency. It
28300 is possible to mix the two models, but rules have to be followed
28301 if this mixing is done to ensure that elaboration checks are not
28304 The basic rule is that @emph{a unit compiled with the static model cannot
28305 be @code{with'ed} by a unit compiled with the dynamic model}. The
28306 reason for this is that in the static model, a unit assumes that
28307 its clients guarantee to use (the equivalent of) pragma
28308 @code{Elaborate_All} so that no elaboration checks are required
28309 in inner subprograms, and this assumption is violated if the
28310 client is compiled with dynamic checks.
28312 The precise rule is as follows. A unit that is compiled with dynamic
28313 checks can only @code{with} a unit that meets at least one of the
28314 following criteria:
28319 The @code{with'ed} unit is itself compiled with dynamic elaboration
28320 checks (that is with the @option{-gnatE} switch.
28323 The @code{with'ed} unit is an internal GNAT implementation unit from
28324 the System, Interfaces, Ada, or GNAT hierarchies.
28327 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28330 The @code{with'ing} unit (that is the client) has an explicit pragma
28331 @code{Elaborate_All} for the @code{with'ed} unit.
28336 If this rule is violated, that is if a unit with dynamic elaboration
28337 checks @code{with's} a unit that does not meet one of the above four
28338 criteria, then the binder (@code{gnatbind}) will issue a warning
28339 similar to that in the following example:
28342 warning: "x.ads" has dynamic elaboration checks and with's
28343 warning: "y.ads" which has static elaboration checks
28347 These warnings indicate that the rule has been violated, and that as a result
28348 elaboration checks may be missed in the resulting executable file.
28349 This warning may be suppressed using the @option{-ws} binder switch
28350 in the usual manner.
28352 One useful application of this mixing rule is in the case of a subsystem
28353 which does not itself @code{with} units from the remainder of the
28354 application. In this case, the entire subsystem can be compiled with
28355 dynamic checks to resolve a circularity in the subsystem, while
28356 allowing the main application that uses this subsystem to be compiled
28357 using the more reliable default static model.
28359 @node What to Do If the Default Elaboration Behavior Fails
28360 @section What to Do If the Default Elaboration Behavior Fails
28363 If the binder cannot find an acceptable order, it outputs detailed
28364 diagnostics. For example:
28370 error: elaboration circularity detected
28371 info: "proc (body)" must be elaborated before "pack (body)"
28372 info: reason: Elaborate_All probably needed in unit "pack (body)"
28373 info: recompile "pack (body)" with -gnatwl
28374 info: for full details
28375 info: "proc (body)"
28376 info: is needed by its spec:
28377 info: "proc (spec)"
28378 info: which is withed by:
28379 info: "pack (body)"
28380 info: "pack (body)" must be elaborated before "proc (body)"
28381 info: reason: pragma Elaborate in unit "proc (body)"
28387 In this case we have a cycle that the binder cannot break. On the one
28388 hand, there is an explicit pragma Elaborate in @code{proc} for
28389 @code{pack}. This means that the body of @code{pack} must be elaborated
28390 before the body of @code{proc}. On the other hand, there is elaboration
28391 code in @code{pack} that calls a subprogram in @code{proc}. This means
28392 that for maximum safety, there should really be a pragma
28393 Elaborate_All in @code{pack} for @code{proc} which would require that
28394 the body of @code{proc} be elaborated before the body of
28395 @code{pack}. Clearly both requirements cannot be satisfied.
28396 Faced with a circularity of this kind, you have three different options.
28399 @item Fix the program
28400 The most desirable option from the point of view of long-term maintenance
28401 is to rearrange the program so that the elaboration problems are avoided.
28402 One useful technique is to place the elaboration code into separate
28403 child packages. Another is to move some of the initialization code to
28404 explicitly called subprograms, where the program controls the order
28405 of initialization explicitly. Although this is the most desirable option,
28406 it may be impractical and involve too much modification, especially in
28407 the case of complex legacy code.
28409 @item Perform dynamic checks
28410 If the compilations are done using the
28412 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28413 manner. Dynamic checks are generated for all calls that could possibly result
28414 in raising an exception. With this switch, the compiler does not generate
28415 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28416 exactly as specified in the @cite{Ada Reference Manual}.
28417 The binder will generate
28418 an executable program that may or may not raise @code{Program_Error}, and then
28419 it is the programmer's job to ensure that it does not raise an exception. Note
28420 that it is important to compile all units with the switch, it cannot be used
28423 @item Suppress checks
28424 The drawback of dynamic checks is that they generate a
28425 significant overhead at run time, both in space and time. If you
28426 are absolutely sure that your program cannot raise any elaboration
28427 exceptions, and you still want to use the dynamic elaboration model,
28428 then you can use the configuration pragma
28429 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28430 example this pragma could be placed in the @file{gnat.adc} file.
28432 @item Suppress checks selectively
28433 When you know that certain calls or instantiations in elaboration code cannot
28434 possibly lead to an elaboration error, and the binder nevertheless complains
28435 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28436 elaboration circularities, it is possible to remove those warnings locally and
28437 obtain a program that will bind. Clearly this can be unsafe, and it is the
28438 responsibility of the programmer to make sure that the resulting program has no
28439 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28440 used with different granularity to suppress warnings and break elaboration
28445 Place the pragma that names the called subprogram in the declarative part
28446 that contains the call.
28449 Place the pragma in the declarative part, without naming an entity. This
28450 disables warnings on all calls in the corresponding declarative region.
28453 Place the pragma in the package spec that declares the called subprogram,
28454 and name the subprogram. This disables warnings on all elaboration calls to
28458 Place the pragma in the package spec that declares the called subprogram,
28459 without naming any entity. This disables warnings on all elaboration calls to
28460 all subprograms declared in this spec.
28462 @item Use Pragma Elaborate
28463 As previously described in section @xref{Treatment of Pragma Elaborate},
28464 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28465 that no elaboration checks are required on calls to the designated unit.
28466 There may be cases in which the caller knows that no transitive calls
28467 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28468 case where @code{pragma Elaborate_All} would cause a circularity.
28472 These five cases are listed in order of decreasing safety, and therefore
28473 require increasing programmer care in their application. Consider the
28476 @smallexample @c adanocomment
28478 function F1 return Integer;
28483 function F2 return Integer;
28484 function Pure (x : integer) return integer;
28485 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28486 -- pragma Suppress (Elaboration_Check); -- (4)
28490 package body Pack1 is
28491 function F1 return Integer is
28495 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28498 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28499 -- pragma Suppress(Elaboration_Check); -- (2)
28501 X1 := Pack2.F2 + 1; -- Elab. call (2)
28506 package body Pack2 is
28507 function F2 return Integer is
28511 function Pure (x : integer) return integer is
28513 return x ** 3 - 3 * x;
28517 with Pack1, Ada.Text_IO;
28520 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28523 In the absence of any pragmas, an attempt to bind this program produces
28524 the following diagnostics:
28530 error: elaboration circularity detected
28531 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28532 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28533 info: recompile "pack1 (body)" with -gnatwl for full details
28534 info: "pack1 (body)"
28535 info: must be elaborated along with its spec:
28536 info: "pack1 (spec)"
28537 info: which is withed by:
28538 info: "pack2 (body)"
28539 info: which must be elaborated along with its spec:
28540 info: "pack2 (spec)"
28541 info: which is withed by:
28542 info: "pack1 (body)"
28545 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28546 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28547 F2 is safe, even though F2 calls F1, because the call appears after the
28548 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28549 remove the warning on the call. It is also possible to use pragma (2)
28550 because there are no other potentially unsafe calls in the block.
28553 The call to @code{Pure} is safe because this function does not depend on the
28554 state of @code{Pack2}. Therefore any call to this function is safe, and it
28555 is correct to place pragma (3) in the corresponding package spec.
28558 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28559 warnings on all calls to functions declared therein. Note that this is not
28560 necessarily safe, and requires more detailed examination of the subprogram
28561 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28562 be already elaborated.
28566 It is hard to generalize on which of these four approaches should be
28567 taken. Obviously if it is possible to fix the program so that the default
28568 treatment works, this is preferable, but this may not always be practical.
28569 It is certainly simple enough to use
28571 but the danger in this case is that, even if the GNAT binder
28572 finds a correct elaboration order, it may not always do so,
28573 and certainly a binder from another Ada compiler might not. A
28574 combination of testing and analysis (for which the warnings generated
28577 switch can be useful) must be used to ensure that the program is free
28578 of errors. One switch that is useful in this testing is the
28579 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28582 Normally the binder tries to find an order that has the best chance
28583 of avoiding elaboration problems. However, if this switch is used, the binder
28584 plays a devil's advocate role, and tries to choose the order that
28585 has the best chance of failing. If your program works even with this
28586 switch, then it has a better chance of being error free, but this is still
28589 For an example of this approach in action, consider the C-tests (executable
28590 tests) from the ACVC suite. If these are compiled and run with the default
28591 treatment, then all but one of them succeed without generating any error
28592 diagnostics from the binder. However, there is one test that fails, and
28593 this is not surprising, because the whole point of this test is to ensure
28594 that the compiler can handle cases where it is impossible to determine
28595 a correct order statically, and it checks that an exception is indeed
28596 raised at run time.
28598 This one test must be compiled and run using the
28600 switch, and then it passes. Alternatively, the entire suite can
28601 be run using this switch. It is never wrong to run with the dynamic
28602 elaboration switch if your code is correct, and we assume that the
28603 C-tests are indeed correct (it is less efficient, but efficiency is
28604 not a factor in running the ACVC tests.)
28606 @node Elaboration for Access-to-Subprogram Values
28607 @section Elaboration for Access-to-Subprogram Values
28608 @cindex Access-to-subprogram
28611 Access-to-subprogram types (introduced in Ada 95) complicate
28612 the handling of elaboration. The trouble is that it becomes
28613 impossible to tell at compile time which procedure
28614 is being called. This means that it is not possible for the binder
28615 to analyze the elaboration requirements in this case.
28617 If at the point at which the access value is created
28618 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
28619 the body of the subprogram is
28620 known to have been elaborated, then the access value is safe, and its use
28621 does not require a check. This may be achieved by appropriate arrangement
28622 of the order of declarations if the subprogram is in the current unit,
28623 or, if the subprogram is in another unit, by using pragma
28624 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
28625 on the referenced unit.
28627 If the referenced body is not known to have been elaborated at the point
28628 the access value is created, then any use of the access value must do a
28629 dynamic check, and this dynamic check will fail and raise a
28630 @code{Program_Error} exception if the body has not been elaborated yet.
28631 GNAT will generate the necessary checks, and in addition, if the
28633 switch is set, will generate warnings that such checks are required.
28635 The use of dynamic dispatching for tagged types similarly generates
28636 a requirement for dynamic checks, and premature calls to any primitive
28637 operation of a tagged type before the body of the operation has been
28638 elaborated, will result in the raising of @code{Program_Error}.
28640 @node Summary of Procedures for Elaboration Control
28641 @section Summary of Procedures for Elaboration Control
28642 @cindex Elaboration control
28645 First, compile your program with the default options, using none of
28646 the special elaboration control switches. If the binder successfully
28647 binds your program, then you can be confident that, apart from issues
28648 raised by the use of access-to-subprogram types and dynamic dispatching,
28649 the program is free of elaboration errors. If it is important that the
28650 program be portable, then use the
28652 switch to generate warnings about missing @code{Elaborate} or
28653 @code{Elaborate_All} pragmas, and supply the missing pragmas.
28655 If the program fails to bind using the default static elaboration
28656 handling, then you can fix the program to eliminate the binder
28657 message, or recompile the entire program with the
28658 @option{-gnatE} switch to generate dynamic elaboration checks,
28659 and, if you are sure there really are no elaboration problems,
28660 use a global pragma @code{Suppress (Elaboration_Check)}.
28662 @node Other Elaboration Order Considerations
28663 @section Other Elaboration Order Considerations
28665 This section has been entirely concerned with the issue of finding a valid
28666 elaboration order, as defined by the Ada Reference Manual. In a case
28667 where several elaboration orders are valid, the task is to find one
28668 of the possible valid elaboration orders (and the static model in GNAT
28669 will ensure that this is achieved).
28671 The purpose of the elaboration rules in the Ada Reference Manual is to
28672 make sure that no entity is accessed before it has been elaborated. For
28673 a subprogram, this means that the spec and body must have been elaborated
28674 before the subprogram is called. For an object, this means that the object
28675 must have been elaborated before its value is read or written. A violation
28676 of either of these two requirements is an access before elaboration order,
28677 and this section has been all about avoiding such errors.
28679 In the case where more than one order of elaboration is possible, in the
28680 sense that access before elaboration errors are avoided, then any one of
28681 the orders is ``correct'' in the sense that it meets the requirements of
28682 the Ada Reference Manual, and no such error occurs.
28684 However, it may be the case for a given program, that there are
28685 constraints on the order of elaboration that come not from consideration
28686 of avoiding elaboration errors, but rather from extra-lingual logic
28687 requirements. Consider this example:
28689 @smallexample @c ada
28690 with Init_Constants;
28691 package Constants is
28696 package Init_Constants is
28697 procedure P; -- require a body
28698 end Init_Constants;
28701 package body Init_Constants is
28702 procedure P is begin null; end;
28706 end Init_Constants;
28710 Z : Integer := Constants.X + Constants.Y;
28714 with Text_IO; use Text_IO;
28717 Put_Line (Calc.Z'Img);
28722 In this example, there is more than one valid order of elaboration. For
28723 example both the following are correct orders:
28726 Init_Constants spec
28729 Init_Constants body
28734 Init_Constants spec
28735 Init_Constants body
28742 There is no language rule to prefer one or the other, both are correct
28743 from an order of elaboration point of view. But the programmatic effects
28744 of the two orders are very different. In the first, the elaboration routine
28745 of @code{Calc} initializes @code{Z} to zero, and then the main program
28746 runs with this value of zero. But in the second order, the elaboration
28747 routine of @code{Calc} runs after the body of Init_Constants has set
28748 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
28751 One could perhaps by applying pretty clever non-artificial intelligence
28752 to the situation guess that it is more likely that the second order of
28753 elaboration is the one desired, but there is no formal linguistic reason
28754 to prefer one over the other. In fact in this particular case, GNAT will
28755 prefer the second order, because of the rule that bodies are elaborated
28756 as soon as possible, but it's just luck that this is what was wanted
28757 (if indeed the second order was preferred).
28759 If the program cares about the order of elaboration routines in a case like
28760 this, it is important to specify the order required. In this particular
28761 case, that could have been achieved by adding to the spec of Calc:
28763 @smallexample @c ada
28764 pragma Elaborate_All (Constants);
28768 which requires that the body (if any) and spec of @code{Constants},
28769 as well as the body and spec of any unit @code{with}'ed by
28770 @code{Constants} be elaborated before @code{Calc} is elaborated.
28772 Clearly no automatic method can always guess which alternative you require,
28773 and if you are working with legacy code that had constraints of this kind
28774 which were not properly specified by adding @code{Elaborate} or
28775 @code{Elaborate_All} pragmas, then indeed it is possible that two different
28776 compilers can choose different orders.
28778 However, GNAT does attempt to diagnose the common situation where there
28779 are uninitialized variables in the visible part of a package spec, and the
28780 corresponding package body has an elaboration block that directly or
28781 indirectly initialized one or more of these variables. This is the situation
28782 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
28783 a warning that suggests this addition if it detects this situation.
28785 The @code{gnatbind}
28786 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
28787 out problems. This switch causes bodies to be elaborated as late as possible
28788 instead of as early as possible. In the example above, it would have forced
28789 the choice of the first elaboration order. If you get different results
28790 when using this switch, and particularly if one set of results is right,
28791 and one is wrong as far as you are concerned, it shows that you have some
28792 missing @code{Elaborate} pragmas. For the example above, we have the
28796 gnatmake -f -q main
28799 gnatmake -f -q main -bargs -p
28805 It is of course quite unlikely that both these results are correct, so
28806 it is up to you in a case like this to investigate the source of the
28807 difference, by looking at the two elaboration orders that are chosen,
28808 and figuring out which is correct, and then adding the necessary
28809 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
28813 @c *******************************
28814 @node Conditional Compilation
28815 @appendix Conditional Compilation
28816 @c *******************************
28817 @cindex Conditional compilation
28820 It is often necessary to arrange for a single source program
28821 to serve multiple purposes, where it is compiled in different
28822 ways to achieve these different goals. Some examples of the
28823 need for this feature are
28826 @item Adapting a program to a different hardware environment
28827 @item Adapting a program to a different target architecture
28828 @item Turning debugging features on and off
28829 @item Arranging for a program to compile with different compilers
28833 In C, or C++, the typical approach would be to use the preprocessor
28834 that is defined as part of the language. The Ada language does not
28835 contain such a feature. This is not an oversight, but rather a very
28836 deliberate design decision, based on the experience that overuse of
28837 the preprocessing features in C and C++ can result in programs that
28838 are extremely difficult to maintain. For example, if we have ten
28839 switches that can be on or off, this means that there are a thousand
28840 separate programs, any one of which might not even be syntactically
28841 correct, and even if syntactically correct, the resulting program
28842 might not work correctly. Testing all combinations can quickly become
28845 Nevertheless, the need to tailor programs certainly exists, and in
28846 this Appendix we will discuss how this can
28847 be achieved using Ada in general, and GNAT in particular.
28850 * Use of Boolean Constants::
28851 * Debugging - A Special Case::
28852 * Conditionalizing Declarations::
28853 * Use of Alternative Implementations::
28857 @node Use of Boolean Constants
28858 @section Use of Boolean Constants
28861 In the case where the difference is simply which code
28862 sequence is executed, the cleanest solution is to use Boolean
28863 constants to control which code is executed.
28865 @smallexample @c ada
28867 FP_Initialize_Required : constant Boolean := True;
28869 if FP_Initialize_Required then
28876 Not only will the code inside the @code{if} statement not be executed if
28877 the constant Boolean is @code{False}, but it will also be completely
28878 deleted from the program.
28879 However, the code is only deleted after the @code{if} statement
28880 has been checked for syntactic and semantic correctness.
28881 (In contrast, with preprocessors the code is deleted before the
28882 compiler ever gets to see it, so it is not checked until the switch
28884 @cindex Preprocessors (contrasted with conditional compilation)
28886 Typically the Boolean constants will be in a separate package,
28889 @smallexample @c ada
28892 FP_Initialize_Required : constant Boolean := True;
28893 Reset_Available : constant Boolean := False;
28900 The @code{Config} package exists in multiple forms for the various targets,
28901 with an appropriate script selecting the version of @code{Config} needed.
28902 Then any other unit requiring conditional compilation can do a @code{with}
28903 of @code{Config} to make the constants visible.
28906 @node Debugging - A Special Case
28907 @section Debugging - A Special Case
28910 A common use of conditional code is to execute statements (for example
28911 dynamic checks, or output of intermediate results) under control of a
28912 debug switch, so that the debugging behavior can be turned on and off.
28913 This can be done using a Boolean constant to control whether the code
28916 @smallexample @c ada
28919 Put_Line ("got to the first stage!");
28927 @smallexample @c ada
28929 if Debugging and then Temperature > 999.0 then
28930 raise Temperature_Crazy;
28936 Since this is a common case, there are special features to deal with
28937 this in a convenient manner. For the case of tests, Ada 2005 has added
28938 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
28939 @cindex pragma @code{Assert}
28940 on the @code{Assert} pragma that has always been available in GNAT, so this
28941 feature may be used with GNAT even if you are not using Ada 2005 features.
28942 The use of pragma @code{Assert} is described in
28943 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
28944 example, the last test could be written:
28946 @smallexample @c ada
28947 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
28953 @smallexample @c ada
28954 pragma Assert (Temperature <= 999.0);
28958 In both cases, if assertions are active and the temperature is excessive,
28959 the exception @code{Assert_Failure} will be raised, with the given string in
28960 the first case or a string indicating the location of the pragma in the second
28961 case used as the exception message.
28963 You can turn assertions on and off by using the @code{Assertion_Policy}
28965 @cindex pragma @code{Assertion_Policy}
28966 This is an Ada 2005 pragma which is implemented in all modes by
28967 GNAT, but only in the latest versions of GNAT which include Ada 2005
28968 capability. Alternatively, you can use the @option{-gnata} switch
28969 @cindex @option{-gnata} switch
28970 to enable assertions from the command line (this is recognized by all versions
28973 For the example above with the @code{Put_Line}, the GNAT-specific pragma
28974 @code{Debug} can be used:
28975 @cindex pragma @code{Debug}
28977 @smallexample @c ada
28978 pragma Debug (Put_Line ("got to the first stage!"));
28982 If debug pragmas are enabled, the argument, which must be of the form of
28983 a procedure call, is executed (in this case, @code{Put_Line} will be called).
28984 Only one call can be present, but of course a special debugging procedure
28985 containing any code you like can be included in the program and then
28986 called in a pragma @code{Debug} argument as needed.
28988 One advantage of pragma @code{Debug} over the @code{if Debugging then}
28989 construct is that pragma @code{Debug} can appear in declarative contexts,
28990 such as at the very beginning of a procedure, before local declarations have
28993 Debug pragmas are enabled using either the @option{-gnata} switch that also
28994 controls assertions, or with a separate Debug_Policy pragma.
28995 @cindex pragma @code{Debug_Policy}
28996 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
28997 in Ada 95 and Ada 83 programs as well), and is analogous to
28998 pragma @code{Assertion_Policy} to control assertions.
29000 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29001 and thus they can appear in @file{gnat.adc} if you are not using a
29002 project file, or in the file designated to contain configuration pragmas
29004 They then apply to all subsequent compilations. In practice the use of
29005 the @option{-gnata} switch is often the most convenient method of controlling
29006 the status of these pragmas.
29008 Note that a pragma is not a statement, so in contexts where a statement
29009 sequence is required, you can't just write a pragma on its own. You have
29010 to add a @code{null} statement.
29012 @smallexample @c ada
29015 @dots{} -- some statements
29017 pragma Assert (Num_Cases < 10);
29024 @node Conditionalizing Declarations
29025 @section Conditionalizing Declarations
29028 In some cases, it may be necessary to conditionalize declarations to meet
29029 different requirements. For example we might want a bit string whose length
29030 is set to meet some hardware message requirement.
29032 In some cases, it may be possible to do this using declare blocks controlled
29033 by conditional constants:
29035 @smallexample @c ada
29037 if Small_Machine then
29039 X : Bit_String (1 .. 10);
29045 X : Large_Bit_String (1 .. 1000);
29054 Note that in this approach, both declarations are analyzed by the
29055 compiler so this can only be used where both declarations are legal,
29056 even though one of them will not be used.
29058 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29059 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29060 that are parameterized by these constants. For example
29062 @smallexample @c ada
29065 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29071 If @code{Bits_Per_Word} is set to 32, this generates either
29073 @smallexample @c ada
29076 Field1 at 0 range 0 .. 32;
29082 for the big endian case, or
29084 @smallexample @c ada
29087 Field1 at 0 range 10 .. 32;
29093 for the little endian case. Since a powerful subset of Ada expression
29094 notation is usable for creating static constants, clever use of this
29095 feature can often solve quite difficult problems in conditionalizing
29096 compilation (note incidentally that in Ada 95, the little endian
29097 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29098 need to define this one yourself).
29101 @node Use of Alternative Implementations
29102 @section Use of Alternative Implementations
29105 In some cases, none of the approaches described above are adequate. This
29106 can occur for example if the set of declarations required is radically
29107 different for two different configurations.
29109 In this situation, the official Ada way of dealing with conditionalizing
29110 such code is to write separate units for the different cases. As long as
29111 this does not result in excessive duplication of code, this can be done
29112 without creating maintenance problems. The approach is to share common
29113 code as far as possible, and then isolate the code and declarations
29114 that are different. Subunits are often a convenient method for breaking
29115 out a piece of a unit that is to be conditionalized, with separate files
29116 for different versions of the subunit for different targets, where the
29117 build script selects the right one to give to the compiler.
29118 @cindex Subunits (and conditional compilation)
29120 As an example, consider a situation where a new feature in Ada 2005
29121 allows something to be done in a really nice way. But your code must be able
29122 to compile with an Ada 95 compiler. Conceptually you want to say:
29124 @smallexample @c ada
29127 @dots{} neat Ada 2005 code
29129 @dots{} not quite as neat Ada 95 code
29135 where @code{Ada_2005} is a Boolean constant.
29137 But this won't work when @code{Ada_2005} is set to @code{False},
29138 since the @code{then} clause will be illegal for an Ada 95 compiler.
29139 (Recall that although such unreachable code would eventually be deleted
29140 by the compiler, it still needs to be legal. If it uses features
29141 introduced in Ada 2005, it will be illegal in Ada 95.)
29143 So instead we write
29145 @smallexample @c ada
29146 procedure Insert is separate;
29150 Then we have two files for the subunit @code{Insert}, with the two sets of
29152 If the package containing this is called @code{File_Queries}, then we might
29156 @item @file{file_queries-insert-2005.adb}
29157 @item @file{file_queries-insert-95.adb}
29161 and the build script renames the appropriate file to
29164 file_queries-insert.adb
29168 and then carries out the compilation.
29170 This can also be done with project files' naming schemes. For example:
29172 @smallexample @c project
29173 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29177 Note also that with project files it is desirable to use a different extension
29178 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29179 conflict may arise through another commonly used feature: to declare as part
29180 of the project a set of directories containing all the sources obeying the
29181 default naming scheme.
29183 The use of alternative units is certainly feasible in all situations,
29184 and for example the Ada part of the GNAT run-time is conditionalized
29185 based on the target architecture using this approach. As a specific example,
29186 consider the implementation of the AST feature in VMS. There is one
29194 which is the same for all architectures, and three bodies:
29198 used for all non-VMS operating systems
29199 @item s-asthan-vms-alpha.adb
29200 used for VMS on the Alpha
29201 @item s-asthan-vms-ia64.adb
29202 used for VMS on the ia64
29206 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29207 this operating system feature is not available, and the two remaining
29208 versions interface with the corresponding versions of VMS to provide
29209 VMS-compatible AST handling. The GNAT build script knows the architecture
29210 and operating system, and automatically selects the right version,
29211 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29213 Another style for arranging alternative implementations is through Ada's
29214 access-to-subprogram facility.
29215 In case some functionality is to be conditionally included,
29216 you can declare an access-to-procedure variable @code{Ref} that is initialized
29217 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29219 In some library package, set @code{Ref} to @code{Proc'Access} for some
29220 procedure @code{Proc} that performs the relevant processing.
29221 The initialization only occurs if the library package is included in the
29223 The same idea can also be implemented using tagged types and dispatching
29227 @node Preprocessing
29228 @section Preprocessing
29229 @cindex Preprocessing
29232 Although it is quite possible to conditionalize code without the use of
29233 C-style preprocessing, as described earlier in this section, it is
29234 nevertheless convenient in some cases to use the C approach. Moreover,
29235 older Ada compilers have often provided some preprocessing capability,
29236 so legacy code may depend on this approach, even though it is not
29239 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29240 extent on the various preprocessors that have been used
29241 with legacy code on other compilers, to enable easier transition).
29243 The preprocessor may be used in two separate modes. It can be used quite
29244 separately from the compiler, to generate a separate output source file
29245 that is then fed to the compiler as a separate step. This is the
29246 @code{gnatprep} utility, whose use is fully described in
29247 @ref{Preprocessing Using gnatprep}.
29248 @cindex @code{gnatprep}
29250 The preprocessing language allows such constructs as
29254 #if DEBUG or PRIORITY > 4 then
29255 bunch of declarations
29257 completely different bunch of declarations
29263 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29264 defined either on the command line or in a separate file.
29266 The other way of running the preprocessor is even closer to the C style and
29267 often more convenient. In this approach the preprocessing is integrated into
29268 the compilation process. The compiler is fed the preprocessor input which
29269 includes @code{#if} lines etc, and then the compiler carries out the
29270 preprocessing internally and processes the resulting output.
29271 For more details on this approach, see @ref{Integrated Preprocessing}.
29274 @c *******************************
29275 @node Inline Assembler
29276 @appendix Inline Assembler
29277 @c *******************************
29280 If you need to write low-level software that interacts directly
29281 with the hardware, Ada provides two ways to incorporate assembly
29282 language code into your program. First, you can import and invoke
29283 external routines written in assembly language, an Ada feature fully
29284 supported by GNAT@. However, for small sections of code it may be simpler
29285 or more efficient to include assembly language statements directly
29286 in your Ada source program, using the facilities of the implementation-defined
29287 package @code{System.Machine_Code}, which incorporates the gcc
29288 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29289 including the following:
29292 @item No need to use non-Ada tools
29293 @item Consistent interface over different targets
29294 @item Automatic usage of the proper calling conventions
29295 @item Access to Ada constants and variables
29296 @item Definition of intrinsic routines
29297 @item Possibility of inlining a subprogram comprising assembler code
29298 @item Code optimizer can take Inline Assembler code into account
29301 This chapter presents a series of examples to show you how to use
29302 the Inline Assembler. Although it focuses on the Intel x86,
29303 the general approach applies also to other processors.
29304 It is assumed that you are familiar with Ada
29305 and with assembly language programming.
29308 * Basic Assembler Syntax::
29309 * A Simple Example of Inline Assembler::
29310 * Output Variables in Inline Assembler::
29311 * Input Variables in Inline Assembler::
29312 * Inlining Inline Assembler Code::
29313 * Other Asm Functionality::
29316 @c ---------------------------------------------------------------------------
29317 @node Basic Assembler Syntax
29318 @section Basic Assembler Syntax
29321 The assembler used by GNAT and gcc is based not on the Intel assembly
29322 language, but rather on a language that descends from the AT&T Unix
29323 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29324 The following table summarizes the main features of @emph{as} syntax
29325 and points out the differences from the Intel conventions.
29326 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29327 pre-processor) documentation for further information.
29330 @item Register names
29331 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29333 Intel: No extra punctuation; for example @code{eax}
29335 @item Immediate operand
29336 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29338 Intel: No extra punctuation; for example @code{4}
29341 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29343 Intel: No extra punctuation; for example @code{loc}
29345 @item Memory contents
29346 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29348 Intel: Square brackets; for example @code{[loc]}
29350 @item Register contents
29351 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29353 Intel: Square brackets; for example @code{[eax]}
29355 @item Hexadecimal numbers
29356 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29358 Intel: Trailing ``h''; for example @code{A0h}
29361 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29364 Intel: Implicit, deduced by assembler; for example @code{mov}
29366 @item Instruction repetition
29367 gcc / @emph{as}: Split into two lines; for example
29373 Intel: Keep on one line; for example @code{rep stosl}
29375 @item Order of operands
29376 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29378 Intel: Destination first; for example @code{mov eax, 4}
29381 @c ---------------------------------------------------------------------------
29382 @node A Simple Example of Inline Assembler
29383 @section A Simple Example of Inline Assembler
29386 The following example will generate a single assembly language statement,
29387 @code{nop}, which does nothing. Despite its lack of run-time effect,
29388 the example will be useful in illustrating the basics of
29389 the Inline Assembler facility.
29391 @smallexample @c ada
29393 with System.Machine_Code; use System.Machine_Code;
29394 procedure Nothing is
29401 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29402 here it takes one parameter, a @emph{template string} that must be a static
29403 expression and that will form the generated instruction.
29404 @code{Asm} may be regarded as a compile-time procedure that parses
29405 the template string and additional parameters (none here),
29406 from which it generates a sequence of assembly language instructions.
29408 The examples in this chapter will illustrate several of the forms
29409 for invoking @code{Asm}; a complete specification of the syntax
29410 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29413 Under the standard GNAT conventions, the @code{Nothing} procedure
29414 should be in a file named @file{nothing.adb}.
29415 You can build the executable in the usual way:
29419 However, the interesting aspect of this example is not its run-time behavior
29420 but rather the generated assembly code.
29421 To see this output, invoke the compiler as follows:
29423 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29425 where the options are:
29429 compile only (no bind or link)
29431 generate assembler listing
29432 @item -fomit-frame-pointer
29433 do not set up separate stack frames
29435 do not add runtime checks
29438 This gives a human-readable assembler version of the code. The resulting
29439 file will have the same name as the Ada source file, but with a @code{.s}
29440 extension. In our example, the file @file{nothing.s} has the following
29445 .file "nothing.adb"
29447 ___gnu_compiled_ada:
29450 .globl __ada_nothing
29462 The assembly code you included is clearly indicated by
29463 the compiler, between the @code{#APP} and @code{#NO_APP}
29464 delimiters. The character before the 'APP' and 'NOAPP'
29465 can differ on different targets. For example, GNU/Linux uses '#APP' while
29466 on NT you will see '/APP'.
29468 If you make a mistake in your assembler code (such as using the
29469 wrong size modifier, or using a wrong operand for the instruction) GNAT
29470 will report this error in a temporary file, which will be deleted when
29471 the compilation is finished. Generating an assembler file will help
29472 in such cases, since you can assemble this file separately using the
29473 @emph{as} assembler that comes with gcc.
29475 Assembling the file using the command
29478 as @file{nothing.s}
29481 will give you error messages whose lines correspond to the assembler
29482 input file, so you can easily find and correct any mistakes you made.
29483 If there are no errors, @emph{as} will generate an object file
29484 @file{nothing.out}.
29486 @c ---------------------------------------------------------------------------
29487 @node Output Variables in Inline Assembler
29488 @section Output Variables in Inline Assembler
29491 The examples in this section, showing how to access the processor flags,
29492 illustrate how to specify the destination operands for assembly language
29495 @smallexample @c ada
29497 with Interfaces; use Interfaces;
29498 with Ada.Text_IO; use Ada.Text_IO;
29499 with System.Machine_Code; use System.Machine_Code;
29500 procedure Get_Flags is
29501 Flags : Unsigned_32;
29504 Asm ("pushfl" & LF & HT & -- push flags on stack
29505 "popl %%eax" & LF & HT & -- load eax with flags
29506 "movl %%eax, %0", -- store flags in variable
29507 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29508 Put_Line ("Flags register:" & Flags'Img);
29513 In order to have a nicely aligned assembly listing, we have separated
29514 multiple assembler statements in the Asm template string with linefeed
29515 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29516 The resulting section of the assembly output file is:
29523 movl %eax, -40(%ebp)
29528 It would have been legal to write the Asm invocation as:
29531 Asm ("pushfl popl %%eax movl %%eax, %0")
29534 but in the generated assembler file, this would come out as:
29538 pushfl popl %eax movl %eax, -40(%ebp)
29542 which is not so convenient for the human reader.
29544 We use Ada comments
29545 at the end of each line to explain what the assembler instructions
29546 actually do. This is a useful convention.
29548 When writing Inline Assembler instructions, you need to precede each register
29549 and variable name with a percent sign. Since the assembler already requires
29550 a percent sign at the beginning of a register name, you need two consecutive
29551 percent signs for such names in the Asm template string, thus @code{%%eax}.
29552 In the generated assembly code, one of the percent signs will be stripped off.
29554 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29555 variables: operands you later define using @code{Input} or @code{Output}
29556 parameters to @code{Asm}.
29557 An output variable is illustrated in
29558 the third statement in the Asm template string:
29562 The intent is to store the contents of the eax register in a variable that can
29563 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29564 necessarily work, since the compiler might optimize by using a register
29565 to hold Flags, and the expansion of the @code{movl} instruction would not be
29566 aware of this optimization. The solution is not to store the result directly
29567 but rather to advise the compiler to choose the correct operand form;
29568 that is the purpose of the @code{%0} output variable.
29570 Information about the output variable is supplied in the @code{Outputs}
29571 parameter to @code{Asm}:
29573 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29576 The output is defined by the @code{Asm_Output} attribute of the target type;
29577 the general format is
29579 Type'Asm_Output (constraint_string, variable_name)
29582 The constraint string directs the compiler how
29583 to store/access the associated variable. In the example
29585 Unsigned_32'Asm_Output ("=m", Flags);
29587 the @code{"m"} (memory) constraint tells the compiler that the variable
29588 @code{Flags} should be stored in a memory variable, thus preventing
29589 the optimizer from keeping it in a register. In contrast,
29591 Unsigned_32'Asm_Output ("=r", Flags);
29593 uses the @code{"r"} (register) constraint, telling the compiler to
29594 store the variable in a register.
29596 If the constraint is preceded by the equal character (@strong{=}), it tells
29597 the compiler that the variable will be used to store data into it.
29599 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29600 allowing the optimizer to choose whatever it deems best.
29602 There are a fairly large number of constraints, but the ones that are
29603 most useful (for the Intel x86 processor) are the following:
29609 global (i.e.@: can be stored anywhere)
29627 use one of eax, ebx, ecx or edx
29629 use one of eax, ebx, ecx, edx, esi or edi
29632 The full set of constraints is described in the gcc and @emph{as}
29633 documentation; note that it is possible to combine certain constraints
29634 in one constraint string.
29636 You specify the association of an output variable with an assembler operand
29637 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
29639 @smallexample @c ada
29641 Asm ("pushfl" & LF & HT & -- push flags on stack
29642 "popl %%eax" & LF & HT & -- load eax with flags
29643 "movl %%eax, %0", -- store flags in variable
29644 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29648 @code{%0} will be replaced in the expanded code by the appropriate operand,
29650 the compiler decided for the @code{Flags} variable.
29652 In general, you may have any number of output variables:
29655 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29657 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29658 of @code{Asm_Output} attributes
29662 @smallexample @c ada
29664 Asm ("movl %%eax, %0" & LF & HT &
29665 "movl %%ebx, %1" & LF & HT &
29667 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29668 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29669 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29673 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29674 in the Ada program.
29676 As a variation on the @code{Get_Flags} example, we can use the constraints
29677 string to direct the compiler to store the eax register into the @code{Flags}
29678 variable, instead of including the store instruction explicitly in the
29679 @code{Asm} template string:
29681 @smallexample @c ada
29683 with Interfaces; use Interfaces;
29684 with Ada.Text_IO; use Ada.Text_IO;
29685 with System.Machine_Code; use System.Machine_Code;
29686 procedure Get_Flags_2 is
29687 Flags : Unsigned_32;
29690 Asm ("pushfl" & LF & HT & -- push flags on stack
29691 "popl %%eax", -- save flags in eax
29692 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29693 Put_Line ("Flags register:" & Flags'Img);
29699 The @code{"a"} constraint tells the compiler that the @code{Flags}
29700 variable will come from the eax register. Here is the resulting code:
29708 movl %eax,-40(%ebp)
29713 The compiler generated the store of eax into Flags after
29714 expanding the assembler code.
29716 Actually, there was no need to pop the flags into the eax register;
29717 more simply, we could just pop the flags directly into the program variable:
29719 @smallexample @c ada
29721 with Interfaces; use Interfaces;
29722 with Ada.Text_IO; use Ada.Text_IO;
29723 with System.Machine_Code; use System.Machine_Code;
29724 procedure Get_Flags_3 is
29725 Flags : Unsigned_32;
29728 Asm ("pushfl" & LF & HT & -- push flags on stack
29729 "pop %0", -- save flags in Flags
29730 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29731 Put_Line ("Flags register:" & Flags'Img);
29736 @c ---------------------------------------------------------------------------
29737 @node Input Variables in Inline Assembler
29738 @section Input Variables in Inline Assembler
29741 The example in this section illustrates how to specify the source operands
29742 for assembly language statements.
29743 The program simply increments its input value by 1:
29745 @smallexample @c ada
29747 with Interfaces; use Interfaces;
29748 with Ada.Text_IO; use Ada.Text_IO;
29749 with System.Machine_Code; use System.Machine_Code;
29750 procedure Increment is
29752 function Incr (Value : Unsigned_32) return Unsigned_32 is
29753 Result : Unsigned_32;
29756 Inputs => Unsigned_32'Asm_Input ("a", Value),
29757 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29761 Value : Unsigned_32;
29765 Put_Line ("Value before is" & Value'Img);
29766 Value := Incr (Value);
29767 Put_Line ("Value after is" & Value'Img);
29772 The @code{Outputs} parameter to @code{Asm} specifies
29773 that the result will be in the eax register and that it is to be stored
29774 in the @code{Result} variable.
29776 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29777 but with an @code{Asm_Input} attribute.
29778 The @code{"="} constraint, indicating an output value, is not present.
29780 You can have multiple input variables, in the same way that you can have more
29781 than one output variable.
29783 The parameter count (%0, %1) etc, now starts at the first input
29784 statement, and continues with the output statements.
29785 When both parameters use the same variable, the
29786 compiler will treat them as the same %n operand, which is the case here.
29788 Just as the @code{Outputs} parameter causes the register to be stored into the
29789 target variable after execution of the assembler statements, so does the
29790 @code{Inputs} parameter cause its variable to be loaded into the register
29791 before execution of the assembler statements.
29793 Thus the effect of the @code{Asm} invocation is:
29795 @item load the 32-bit value of @code{Value} into eax
29796 @item execute the @code{incl %eax} instruction
29797 @item store the contents of eax into the @code{Result} variable
29800 The resulting assembler file (with @option{-O2} optimization) contains:
29803 _increment__incr.1:
29816 @c ---------------------------------------------------------------------------
29817 @node Inlining Inline Assembler Code
29818 @section Inlining Inline Assembler Code
29821 For a short subprogram such as the @code{Incr} function in the previous
29822 section, the overhead of the call and return (creating / deleting the stack
29823 frame) can be significant, compared to the amount of code in the subprogram
29824 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29825 which directs the compiler to expand invocations of the subprogram at the
29826 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29827 Here is the resulting program:
29829 @smallexample @c ada
29831 with Interfaces; use Interfaces;
29832 with Ada.Text_IO; use Ada.Text_IO;
29833 with System.Machine_Code; use System.Machine_Code;
29834 procedure Increment_2 is
29836 function Incr (Value : Unsigned_32) return Unsigned_32 is
29837 Result : Unsigned_32;
29840 Inputs => Unsigned_32'Asm_Input ("a", Value),
29841 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29844 pragma Inline (Increment);
29846 Value : Unsigned_32;
29850 Put_Line ("Value before is" & Value'Img);
29851 Value := Increment (Value);
29852 Put_Line ("Value after is" & Value'Img);
29857 Compile the program with both optimization (@option{-O2}) and inlining
29858 (@option{-gnatn}) enabled.
29860 The @code{Incr} function is still compiled as usual, but at the
29861 point in @code{Increment} where our function used to be called:
29866 call _increment__incr.1
29871 the code for the function body directly appears:
29884 thus saving the overhead of stack frame setup and an out-of-line call.
29886 @c ---------------------------------------------------------------------------
29887 @node Other Asm Functionality
29888 @section Other @code{Asm} Functionality
29891 This section describes two important parameters to the @code{Asm}
29892 procedure: @code{Clobber}, which identifies register usage;
29893 and @code{Volatile}, which inhibits unwanted optimizations.
29896 * The Clobber Parameter::
29897 * The Volatile Parameter::
29900 @c ---------------------------------------------------------------------------
29901 @node The Clobber Parameter
29902 @subsection The @code{Clobber} Parameter
29905 One of the dangers of intermixing assembly language and a compiled language
29906 such as Ada is that the compiler needs to be aware of which registers are
29907 being used by the assembly code. In some cases, such as the earlier examples,
29908 the constraint string is sufficient to indicate register usage (e.g.,
29910 the eax register). But more generally, the compiler needs an explicit
29911 identification of the registers that are used by the Inline Assembly
29914 Using a register that the compiler doesn't know about
29915 could be a side effect of an instruction (like @code{mull}
29916 storing its result in both eax and edx).
29917 It can also arise from explicit register usage in your
29918 assembly code; for example:
29921 Asm ("movl %0, %%ebx" & LF & HT &
29923 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29924 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
29928 where the compiler (since it does not analyze the @code{Asm} template string)
29929 does not know you are using the ebx register.
29931 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29932 to identify the registers that will be used by your assembly code:
29936 Asm ("movl %0, %%ebx" & LF & HT &
29938 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29939 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29944 The Clobber parameter is a static string expression specifying the
29945 register(s) you are using. Note that register names are @emph{not} prefixed
29946 by a percent sign. Also, if more than one register is used then their names
29947 are separated by commas; e.g., @code{"eax, ebx"}
29949 The @code{Clobber} parameter has several additional uses:
29951 @item Use ``register'' name @code{cc} to indicate that flags might have changed
29952 @item Use ``register'' name @code{memory} if you changed a memory location
29955 @c ---------------------------------------------------------------------------
29956 @node The Volatile Parameter
29957 @subsection The @code{Volatile} Parameter
29958 @cindex Volatile parameter
29961 Compiler optimizations in the presence of Inline Assembler may sometimes have
29962 unwanted effects. For example, when an @code{Asm} invocation with an input
29963 variable is inside a loop, the compiler might move the loading of the input
29964 variable outside the loop, regarding it as a one-time initialization.
29966 If this effect is not desired, you can disable such optimizations by setting
29967 the @code{Volatile} parameter to @code{True}; for example:
29969 @smallexample @c ada
29971 Asm ("movl %0, %%ebx" & LF & HT &
29973 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29974 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29980 By default, @code{Volatile} is set to @code{False} unless there is no
29981 @code{Outputs} parameter.
29983 Although setting @code{Volatile} to @code{True} prevents unwanted
29984 optimizations, it will also disable other optimizations that might be
29985 important for efficiency. In general, you should set @code{Volatile}
29986 to @code{True} only if the compiler's optimizations have created
29988 @c END OF INLINE ASSEMBLER CHAPTER
29989 @c ===============================
29991 @c ***********************************
29992 @c * Compatibility and Porting Guide *
29993 @c ***********************************
29994 @node Compatibility and Porting Guide
29995 @appendix Compatibility and Porting Guide
29998 This chapter describes the compatibility issues that may arise between
29999 GNAT and other Ada compilation systems (including those for Ada 83),
30000 and shows how GNAT can expedite porting
30001 applications developed in other Ada environments.
30004 * Compatibility with Ada 83::
30005 * Compatibility between Ada 95 and Ada 2005::
30006 * Implementation-dependent characteristics::
30007 * Compatibility with Other Ada Systems::
30008 * Representation Clauses::
30010 @c Brief section is only in non-VMS version
30011 @c Full chapter is in VMS version
30012 * Compatibility with HP Ada 83::
30015 * Transitioning to 64-Bit GNAT for OpenVMS::
30019 @node Compatibility with Ada 83
30020 @section Compatibility with Ada 83
30021 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30024 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30025 particular, the design intention was that the difficulties associated
30026 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30027 that occur when moving from one Ada 83 system to another.
30029 However, there are a number of points at which there are minor
30030 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30031 full details of these issues,
30032 and should be consulted for a complete treatment.
30034 following subsections treat the most likely issues to be encountered.
30037 * Legal Ada 83 programs that are illegal in Ada 95::
30038 * More deterministic semantics::
30039 * Changed semantics::
30040 * Other language compatibility issues::
30043 @node Legal Ada 83 programs that are illegal in Ada 95
30044 @subsection Legal Ada 83 programs that are illegal in Ada 95
30046 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30047 Ada 95 and thus also in Ada 2005:
30050 @item Character literals
30051 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30052 @code{Wide_Character} as a new predefined character type, some uses of
30053 character literals that were legal in Ada 83 are illegal in Ada 95.
30055 @smallexample @c ada
30056 for Char in 'A' .. 'Z' loop @dots{} end loop;
30060 The problem is that @code{'A'} and @code{'Z'} could be from either
30061 @code{Character} or @code{Wide_Character}. The simplest correction
30062 is to make the type explicit; e.g.:
30063 @smallexample @c ada
30064 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30067 @item New reserved words
30068 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30069 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30070 Existing Ada 83 code using any of these identifiers must be edited to
30071 use some alternative name.
30073 @item Freezing rules
30074 The rules in Ada 95 are slightly different with regard to the point at
30075 which entities are frozen, and representation pragmas and clauses are
30076 not permitted past the freeze point. This shows up most typically in
30077 the form of an error message complaining that a representation item
30078 appears too late, and the appropriate corrective action is to move
30079 the item nearer to the declaration of the entity to which it refers.
30081 A particular case is that representation pragmas
30084 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30086 cannot be applied to a subprogram body. If necessary, a separate subprogram
30087 declaration must be introduced to which the pragma can be applied.
30089 @item Optional bodies for library packages
30090 In Ada 83, a package that did not require a package body was nevertheless
30091 allowed to have one. This lead to certain surprises in compiling large
30092 systems (situations in which the body could be unexpectedly ignored by the
30093 binder). In Ada 95, if a package does not require a body then it is not
30094 permitted to have a body. To fix this problem, simply remove a redundant
30095 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30096 into the spec that makes the body required. One approach is to add a private
30097 part to the package declaration (if necessary), and define a parameterless
30098 procedure called @code{Requires_Body}, which must then be given a dummy
30099 procedure body in the package body, which then becomes required.
30100 Another approach (assuming that this does not introduce elaboration
30101 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30102 since one effect of this pragma is to require the presence of a package body.
30104 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30105 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30106 @code{Constraint_Error}.
30107 This means that it is illegal to have separate exception handlers for
30108 the two exceptions. The fix is simply to remove the handler for the
30109 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30110 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30112 @item Indefinite subtypes in generics
30113 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30114 as the actual for a generic formal private type, but then the instantiation
30115 would be illegal if there were any instances of declarations of variables
30116 of this type in the generic body. In Ada 95, to avoid this clear violation
30117 of the methodological principle known as the ``contract model'',
30118 the generic declaration explicitly indicates whether
30119 or not such instantiations are permitted. If a generic formal parameter
30120 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30121 type name, then it can be instantiated with indefinite types, but no
30122 stand-alone variables can be declared of this type. Any attempt to declare
30123 such a variable will result in an illegality at the time the generic is
30124 declared. If the @code{(<>)} notation is not used, then it is illegal
30125 to instantiate the generic with an indefinite type.
30126 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30127 It will show up as a compile time error, and
30128 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30131 @node More deterministic semantics
30132 @subsection More deterministic semantics
30136 Conversions from real types to integer types round away from 0. In Ada 83
30137 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30138 implementation freedom was intended to support unbiased rounding in
30139 statistical applications, but in practice it interfered with portability.
30140 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30141 is required. Numeric code may be affected by this change in semantics.
30142 Note, though, that this issue is no worse than already existed in Ada 83
30143 when porting code from one vendor to another.
30146 The Real-Time Annex introduces a set of policies that define the behavior of
30147 features that were implementation dependent in Ada 83, such as the order in
30148 which open select branches are executed.
30151 @node Changed semantics
30152 @subsection Changed semantics
30155 The worst kind of incompatibility is one where a program that is legal in
30156 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30157 possible in Ada 83. Fortunately this is extremely rare, but the one
30158 situation that you should be alert to is the change in the predefined type
30159 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30162 @item Range of type @code{Character}
30163 The range of @code{Standard.Character} is now the full 256 characters
30164 of Latin-1, whereas in most Ada 83 implementations it was restricted
30165 to 128 characters. Although some of the effects of
30166 this change will be manifest in compile-time rejection of legal
30167 Ada 83 programs it is possible for a working Ada 83 program to have
30168 a different effect in Ada 95, one that was not permitted in Ada 83.
30169 As an example, the expression
30170 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30171 delivers @code{255} as its value.
30172 In general, you should look at the logic of any
30173 character-processing Ada 83 program and see whether it needs to be adapted
30174 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30175 character handling package that may be relevant if code needs to be adapted
30176 to account for the additional Latin-1 elements.
30177 The desirable fix is to
30178 modify the program to accommodate the full character set, but in some cases
30179 it may be convenient to define a subtype or derived type of Character that
30180 covers only the restricted range.
30184 @node Other language compatibility issues
30185 @subsection Other language compatibility issues
30188 @item @option{-gnat83} switch
30189 All implementations of GNAT provide a switch that causes GNAT to operate
30190 in Ada 83 mode. In this mode, some but not all compatibility problems
30191 of the type described above are handled automatically. For example, the
30192 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30193 as identifiers as in Ada 83.
30195 in practice, it is usually advisable to make the necessary modifications
30196 to the program to remove the need for using this switch.
30197 See @ref{Compiling Different Versions of Ada}.
30199 @item Support for removed Ada 83 pragmas and attributes
30200 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30201 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30202 compilers are allowed, but not required, to implement these missing
30203 elements. In contrast with some other compilers, GNAT implements all
30204 such pragmas and attributes, eliminating this compatibility concern. These
30205 include @code{pragma Interface} and the floating point type attributes
30206 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30210 @node Compatibility between Ada 95 and Ada 2005
30211 @section Compatibility between Ada 95 and Ada 2005
30212 @cindex Compatibility between Ada 95 and Ada 2005
30215 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30216 a number of incompatibilities. Several are enumerated below;
30217 for a complete description please see the
30218 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30219 @cite{Rationale for Ada 2005}.
30222 @item New reserved words.
30223 The words @code{interface}, @code{overriding} and @code{synchronized} are
30224 reserved in Ada 2005.
30225 A pre-Ada 2005 program that uses any of these as an identifier will be
30228 @item New declarations in predefined packages.
30229 A number of packages in the predefined environment contain new declarations:
30230 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30231 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30232 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30233 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30234 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30235 If an Ada 95 program does a @code{with} and @code{use} of any of these
30236 packages, the new declarations may cause name clashes.
30238 @item Access parameters.
30239 A nondispatching subprogram with an access parameter cannot be renamed
30240 as a dispatching operation. This was permitted in Ada 95.
30242 @item Access types, discriminants, and constraints.
30243 Rule changes in this area have led to some incompatibilities; for example,
30244 constrained subtypes of some access types are not permitted in Ada 2005.
30246 @item Aggregates for limited types.
30247 The allowance of aggregates for limited types in Ada 2005 raises the
30248 possibility of ambiguities in legal Ada 95 programs, since additional types
30249 now need to be considered in expression resolution.
30251 @item Fixed-point multiplication and division.
30252 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30253 were legal in Ada 95 and invoked the predefined versions of these operations,
30255 The ambiguity may be resolved either by applying a type conversion to the
30256 expression, or by explicitly invoking the operation from package
30259 @item Return-by-reference types.
30260 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30261 can declare a function returning a value from an anonymous access type.
30265 @node Implementation-dependent characteristics
30266 @section Implementation-dependent characteristics
30268 Although the Ada language defines the semantics of each construct as
30269 precisely as practical, in some situations (for example for reasons of
30270 efficiency, or where the effect is heavily dependent on the host or target
30271 platform) the implementation is allowed some freedom. In porting Ada 83
30272 code to GNAT, you need to be aware of whether / how the existing code
30273 exercised such implementation dependencies. Such characteristics fall into
30274 several categories, and GNAT offers specific support in assisting the
30275 transition from certain Ada 83 compilers.
30278 * Implementation-defined pragmas::
30279 * Implementation-defined attributes::
30281 * Elaboration order::
30282 * Target-specific aspects::
30285 @node Implementation-defined pragmas
30286 @subsection Implementation-defined pragmas
30289 Ada compilers are allowed to supplement the language-defined pragmas, and
30290 these are a potential source of non-portability. All GNAT-defined pragmas
30291 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30292 Reference Manual}, and these include several that are specifically
30293 intended to correspond to other vendors' Ada 83 pragmas.
30294 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30295 For compatibility with HP Ada 83, GNAT supplies the pragmas
30296 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30297 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30298 and @code{Volatile}.
30299 Other relevant pragmas include @code{External} and @code{Link_With}.
30300 Some vendor-specific
30301 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30303 avoiding compiler rejection of units that contain such pragmas; they are not
30304 relevant in a GNAT context and hence are not otherwise implemented.
30306 @node Implementation-defined attributes
30307 @subsection Implementation-defined attributes
30309 Analogous to pragmas, the set of attributes may be extended by an
30310 implementation. All GNAT-defined attributes are described in
30311 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30312 Manual}, and these include several that are specifically intended
30313 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30314 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30315 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30319 @subsection Libraries
30321 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30322 code uses vendor-specific libraries then there are several ways to manage
30323 this in Ada 95 or Ada 2005:
30326 If the source code for the libraries (specs and bodies) are
30327 available, then the libraries can be migrated in the same way as the
30330 If the source code for the specs but not the bodies are
30331 available, then you can reimplement the bodies.
30333 Some features introduced by Ada 95 obviate the need for library support. For
30334 example most Ada 83 vendors supplied a package for unsigned integers. The
30335 Ada 95 modular type feature is the preferred way to handle this need, so
30336 instead of migrating or reimplementing the unsigned integer package it may
30337 be preferable to retrofit the application using modular types.
30340 @node Elaboration order
30341 @subsection Elaboration order
30343 The implementation can choose any elaboration order consistent with the unit
30344 dependency relationship. This freedom means that some orders can result in
30345 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30346 to invoke a subprogram its body has been elaborated, or to instantiate a
30347 generic before the generic body has been elaborated. By default GNAT
30348 attempts to choose a safe order (one that will not encounter access before
30349 elaboration problems) by implicitly inserting @code{Elaborate} or
30350 @code{Elaborate_All} pragmas where
30351 needed. However, this can lead to the creation of elaboration circularities
30352 and a resulting rejection of the program by gnatbind. This issue is
30353 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30354 In brief, there are several
30355 ways to deal with this situation:
30359 Modify the program to eliminate the circularities, e.g.@: by moving
30360 elaboration-time code into explicitly-invoked procedures
30362 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30363 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30364 @code{Elaborate_All}
30365 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30366 (by selectively suppressing elaboration checks via pragma
30367 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30370 @node Target-specific aspects
30371 @subsection Target-specific aspects
30373 Low-level applications need to deal with machine addresses, data
30374 representations, interfacing with assembler code, and similar issues. If
30375 such an Ada 83 application is being ported to different target hardware (for
30376 example where the byte endianness has changed) then you will need to
30377 carefully examine the program logic; the porting effort will heavily depend
30378 on the robustness of the original design. Moreover, Ada 95 (and thus
30379 Ada 2005) are sometimes
30380 incompatible with typical Ada 83 compiler practices regarding implicit
30381 packing, the meaning of the Size attribute, and the size of access values.
30382 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30384 @node Compatibility with Other Ada Systems
30385 @section Compatibility with Other Ada Systems
30388 If programs avoid the use of implementation dependent and
30389 implementation defined features, as documented in the @cite{Ada
30390 Reference Manual}, there should be a high degree of portability between
30391 GNAT and other Ada systems. The following are specific items which
30392 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30393 compilers, but do not affect porting code to GNAT@.
30394 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30395 the following issues may or may not arise for Ada 2005 programs
30396 when other compilers appear.)
30399 @item Ada 83 Pragmas and Attributes
30400 Ada 95 compilers are allowed, but not required, to implement the missing
30401 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30402 GNAT implements all such pragmas and attributes, eliminating this as
30403 a compatibility concern, but some other Ada 95 compilers reject these
30404 pragmas and attributes.
30406 @item Specialized Needs Annexes
30407 GNAT implements the full set of special needs annexes. At the
30408 current time, it is the only Ada 95 compiler to do so. This means that
30409 programs making use of these features may not be portable to other Ada
30410 95 compilation systems.
30412 @item Representation Clauses
30413 Some other Ada 95 compilers implement only the minimal set of
30414 representation clauses required by the Ada 95 reference manual. GNAT goes
30415 far beyond this minimal set, as described in the next section.
30418 @node Representation Clauses
30419 @section Representation Clauses
30422 The Ada 83 reference manual was quite vague in describing both the minimal
30423 required implementation of representation clauses, and also their precise
30424 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30425 minimal set of capabilities required is still quite limited.
30427 GNAT implements the full required set of capabilities in
30428 Ada 95 and Ada 2005, but also goes much further, and in particular
30429 an effort has been made to be compatible with existing Ada 83 usage to the
30430 greatest extent possible.
30432 A few cases exist in which Ada 83 compiler behavior is incompatible with
30433 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30434 intentional or accidental dependence on specific implementation dependent
30435 characteristics of these Ada 83 compilers. The following is a list of
30436 the cases most likely to arise in existing Ada 83 code.
30439 @item Implicit Packing
30440 Some Ada 83 compilers allowed a Size specification to cause implicit
30441 packing of an array or record. This could cause expensive implicit
30442 conversions for change of representation in the presence of derived
30443 types, and the Ada design intends to avoid this possibility.
30444 Subsequent AI's were issued to make it clear that such implicit
30445 change of representation in response to a Size clause is inadvisable,
30446 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30447 Reference Manuals as implementation advice that is followed by GNAT@.
30448 The problem will show up as an error
30449 message rejecting the size clause. The fix is simply to provide
30450 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30451 a Component_Size clause.
30453 @item Meaning of Size Attribute
30454 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30455 the minimal number of bits required to hold values of the type. For example,
30456 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30457 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30458 some 32 in this situation. This problem will usually show up as a compile
30459 time error, but not always. It is a good idea to check all uses of the
30460 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30461 Object_Size can provide a useful way of duplicating the behavior of
30462 some Ada 83 compiler systems.
30464 @item Size of Access Types
30465 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30466 and that therefore it will be the same size as a System.Address value. This
30467 assumption is true for GNAT in most cases with one exception. For the case of
30468 a pointer to an unconstrained array type (where the bounds may vary from one
30469 value of the access type to another), the default is to use a ``fat pointer'',
30470 which is represented as two separate pointers, one to the bounds, and one to
30471 the array. This representation has a number of advantages, including improved
30472 efficiency. However, it may cause some difficulties in porting existing Ada 83
30473 code which makes the assumption that, for example, pointers fit in 32 bits on
30474 a machine with 32-bit addressing.
30476 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30477 access types in this case (where the designated type is an unconstrained array
30478 type). These thin pointers are indeed the same size as a System.Address value.
30479 To specify a thin pointer, use a size clause for the type, for example:
30481 @smallexample @c ada
30482 type X is access all String;
30483 for X'Size use Standard'Address_Size;
30487 which will cause the type X to be represented using a single pointer.
30488 When using this representation, the bounds are right behind the array.
30489 This representation is slightly less efficient, and does not allow quite
30490 such flexibility in the use of foreign pointers or in using the
30491 Unrestricted_Access attribute to create pointers to non-aliased objects.
30492 But for any standard portable use of the access type it will work in
30493 a functionally correct manner and allow porting of existing code.
30494 Note that another way of forcing a thin pointer representation
30495 is to use a component size clause for the element size in an array,
30496 or a record representation clause for an access field in a record.
30500 @c This brief section is only in the non-VMS version
30501 @c The complete chapter on HP Ada is in the VMS version
30502 @node Compatibility with HP Ada 83
30503 @section Compatibility with HP Ada 83
30506 The VMS version of GNAT fully implements all the pragmas and attributes
30507 provided by HP Ada 83, as well as providing the standard HP Ada 83
30508 libraries, including Starlet. In addition, data layouts and parameter
30509 passing conventions are highly compatible. This means that porting
30510 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30511 most other porting efforts. The following are some of the most
30512 significant differences between GNAT and HP Ada 83.
30515 @item Default floating-point representation
30516 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30517 it is VMS format. GNAT does implement the necessary pragmas
30518 (Long_Float, Float_Representation) for changing this default.
30521 The package System in GNAT exactly corresponds to the definition in the
30522 Ada 95 reference manual, which means that it excludes many of the
30523 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30524 that contains the additional definitions, and a special pragma,
30525 Extend_System allows this package to be treated transparently as an
30526 extension of package System.
30529 The definitions provided by Aux_DEC are exactly compatible with those
30530 in the HP Ada 83 version of System, with one exception.
30531 HP Ada provides the following declarations:
30533 @smallexample @c ada
30534 TO_ADDRESS (INTEGER)
30535 TO_ADDRESS (UNSIGNED_LONGWORD)
30536 TO_ADDRESS (@i{universal_integer})
30540 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30541 an extension to Ada 83 not strictly compatible with the reference manual.
30542 In GNAT, we are constrained to be exactly compatible with the standard,
30543 and this means we cannot provide this capability. In HP Ada 83, the
30544 point of this definition is to deal with a call like:
30546 @smallexample @c ada
30547 TO_ADDRESS (16#12777#);
30551 Normally, according to the Ada 83 standard, one would expect this to be
30552 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30553 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30554 definition using @i{universal_integer} takes precedence.
30556 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30557 is not possible to be 100% compatible. Since there are many programs using
30558 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30559 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30560 declarations provided in the GNAT version of AUX_Dec are:
30562 @smallexample @c ada
30563 function To_Address (X : Integer) return Address;
30564 pragma Pure_Function (To_Address);
30566 function To_Address_Long (X : Unsigned_Longword)
30568 pragma Pure_Function (To_Address_Long);
30572 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30573 change the name to TO_ADDRESS_LONG@.
30575 @item Task_Id values
30576 The Task_Id values assigned will be different in the two systems, and GNAT
30577 does not provide a specified value for the Task_Id of the environment task,
30578 which in GNAT is treated like any other declared task.
30582 For full details on these and other less significant compatibility issues,
30583 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30584 Overview and Comparison on HP Platforms}.
30586 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30587 attributes are recognized, although only a subset of them can sensibly
30588 be implemented. The description of pragmas in @ref{Implementation
30589 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30590 indicates whether or not they are applicable to non-VMS systems.
30594 @node Transitioning to 64-Bit GNAT for OpenVMS
30595 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30598 This section is meant to assist users of pre-2006 @value{EDITION}
30599 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30600 the version of the GNAT technology supplied in 2006 and later for
30601 OpenVMS on both Alpha and I64.
30604 * Introduction to transitioning::
30605 * Migration of 32 bit code::
30606 * Taking advantage of 64 bit addressing::
30607 * Technical details::
30610 @node Introduction to transitioning
30611 @subsection Introduction
30614 64-bit @value{EDITION} for Open VMS has been designed to meet
30619 Providing a full conforming implementation of Ada 95 and Ada 2005
30622 Allowing maximum backward compatibility, thus easing migration of existing
30626 Supplying a path for exploiting the full 64-bit address range
30630 Ada's strong typing semantics has made it
30631 impractical to have different 32-bit and 64-bit modes. As soon as
30632 one object could possibly be outside the 32-bit address space, this
30633 would make it necessary for the @code{System.Address} type to be 64 bits.
30634 In particular, this would cause inconsistencies if 32-bit code is
30635 called from 64-bit code that raises an exception.
30637 This issue has been resolved by always using 64-bit addressing
30638 at the system level, but allowing for automatic conversions between
30639 32-bit and 64-bit addresses where required. Thus users who
30640 do not currently require 64-bit addressing capabilities, can
30641 recompile their code with only minimal changes (and indeed
30642 if the code is written in portable Ada, with no assumptions about
30643 the size of the @code{Address} type, then no changes at all are necessary).
30645 this approach provides a simple, gradual upgrade path to future
30646 use of larger memories than available for 32-bit systems.
30647 Also, newly written applications or libraries will by default
30648 be fully compatible with future systems exploiting 64-bit
30649 addressing capabilities.
30651 @ref{Migration of 32 bit code}, will focus on porting applications
30652 that do not require more than 2 GB of
30653 addressable memory. This code will be referred to as
30654 @emph{32-bit code}.
30655 For applications intending to exploit the full 64-bit address space,
30656 @ref{Taking advantage of 64 bit addressing},
30657 will consider further changes that may be required.
30658 Such code will be referred to below as @emph{64-bit code}.
30660 @node Migration of 32 bit code
30661 @subsection Migration of 32-bit code
30666 * Unchecked conversions::
30667 * Predefined constants::
30668 * Interfacing with C::
30669 * Experience with source compatibility::
30672 @node Address types
30673 @subsubsection Address types
30676 To solve the problem of mixing 64-bit and 32-bit addressing,
30677 while maintaining maximum backward compatibility, the following
30678 approach has been taken:
30682 @code{System.Address} always has a size of 64 bits
30685 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
30689 Since @code{System.Short_Address} is a subtype of @code{System.Address},
30690 a @code{Short_Address}
30691 may be used where an @code{Address} is required, and vice versa, without
30692 needing explicit type conversions.
30693 By virtue of the Open VMS parameter passing conventions,
30695 and exported subprograms that have 32-bit address parameters are
30696 compatible with those that have 64-bit address parameters.
30697 (See @ref{Making code 64 bit clean} for details.)
30699 The areas that may need attention are those where record types have
30700 been defined that contain components of the type @code{System.Address}, and
30701 where objects of this type are passed to code expecting a record layout with
30704 Different compilers on different platforms cannot be
30705 expected to represent the same type in the same way,
30706 since alignment constraints
30707 and other system-dependent properties affect the compiler's decision.
30708 For that reason, Ada code
30709 generally uses representation clauses to specify the expected
30710 layout where required.
30712 If such a representation clause uses 32 bits for a component having
30713 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
30714 will detect that error and produce a specific diagnostic message.
30715 The developer should then determine whether the representation
30716 should be 64 bits or not and make either of two changes:
30717 change the size to 64 bits and leave the type as @code{System.Address}, or
30718 leave the size as 32 bits and change the type to @code{System.Short_Address}.
30719 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
30720 required in any code setting or accessing the field; the compiler will
30721 automatically perform any needed conversions between address
30725 @subsubsection Access types
30728 By default, objects designated by access values are always
30729 allocated in the 32-bit
30730 address space. Thus legacy code will never contain
30731 any objects that are not addressable with 32-bit addresses, and
30732 the compiler will never raise exceptions as result of mixing
30733 32-bit and 64-bit addresses.
30735 However, the access values themselves are represented in 64 bits, for optimum
30736 performance and future compatibility with 64-bit code. As was
30737 the case with @code{System.Address}, the compiler will give an error message
30738 if an object or record component has a representation clause that
30739 requires the access value to fit in 32 bits. In such a situation,
30740 an explicit size clause for the access type, specifying 32 bits,
30741 will have the desired effect.
30743 General access types (declared with @code{access all}) can never be
30744 32 bits, as values of such types must be able to refer to any object
30745 of the designated type,
30746 including objects residing outside the 32-bit address range.
30747 Existing Ada 83 code will not contain such type definitions,
30748 however, since general access types were introduced in Ada 95.
30750 @node Unchecked conversions
30751 @subsubsection Unchecked conversions
30754 In the case of an @code{Unchecked_Conversion} where the source type is a
30755 64-bit access type or the type @code{System.Address}, and the target
30756 type is a 32-bit type, the compiler will generate a warning.
30757 Even though the generated code will still perform the required
30758 conversions, it is highly recommended in these cases to use
30759 respectively a 32-bit access type or @code{System.Short_Address}
30760 as the source type.
30762 @node Predefined constants
30763 @subsubsection Predefined constants
30766 The following table shows the correspondence between pre-2006 versions of
30767 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
30770 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
30771 @item @b{Constant} @tab @b{Old} @tab @b{New}
30772 @item @code{System.Word_Size} @tab 32 @tab 64
30773 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
30774 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
30775 @item @code{System.Address_Size} @tab 32 @tab 64
30779 If you need to refer to the specific
30780 memory size of a 32-bit implementation, instead of the
30781 actual memory size, use @code{System.Short_Memory_Size}
30782 rather than @code{System.Memory_Size}.
30783 Similarly, references to @code{System.Address_Size} may need
30784 to be replaced by @code{System.Short_Address'Size}.
30785 The program @command{gnatfind} may be useful for locating
30786 references to the above constants, so that you can verify that they
30789 @node Interfacing with C
30790 @subsubsection Interfacing with C
30793 In order to minimize the impact of the transition to 64-bit addresses on
30794 legacy programs, some fundamental types in the @code{Interfaces.C}
30795 package hierarchy continue to be represented in 32 bits.
30796 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
30797 This eases integration with the default HP C layout choices, for example
30798 as found in the system routines in @code{DECC$SHR.EXE}.
30799 Because of this implementation choice, the type fully compatible with
30800 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
30801 Depending on the context the compiler will issue a
30802 warning or an error when type @code{Address} is used, alerting the user to a
30803 potential problem. Otherwise 32-bit programs that use
30804 @code{Interfaces.C} should normally not require code modifications
30806 The other issue arising with C interfacing concerns pragma @code{Convention}.
30807 For VMS 64-bit systems, there is an issue of the appropriate default size
30808 of C convention pointers in the absence of an explicit size clause. The HP
30809 C compiler can choose either 32 or 64 bits depending on compiler options.
30810 GNAT chooses 32-bits rather than 64-bits in the default case where no size
30811 clause is given. This proves a better choice for porting 32-bit legacy
30812 applications. In order to have a 64-bit representation, it is necessary to
30813 specify a size representation clause. For example:
30815 @smallexample @c ada
30816 type int_star is access Interfaces.C.int;
30817 pragma Convention(C, int_star);
30818 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
30821 @node Experience with source compatibility
30822 @subsubsection Experience with source compatibility
30825 The Security Server and STARLET on I64 provide an interesting ``test case''
30826 for source compatibility issues, since it is in such system code
30827 where assumptions about @code{Address} size might be expected to occur.
30828 Indeed, there were a small number of occasions in the Security Server
30829 file @file{jibdef.ads}
30830 where a representation clause for a record type specified
30831 32 bits for a component of type @code{Address}.
30832 All of these errors were detected by the compiler.
30833 The repair was obvious and immediate; to simply replace @code{Address} by
30834 @code{Short_Address}.
30836 In the case of STARLET, there were several record types that should
30837 have had representation clauses but did not. In these record types
30838 there was an implicit assumption that an @code{Address} value occupied
30840 These compiled without error, but their usage resulted in run-time error
30841 returns from STARLET system calls.
30842 Future GNAT technology enhancements may include a tool that detects and flags
30843 these sorts of potential source code porting problems.
30845 @c ****************************************
30846 @node Taking advantage of 64 bit addressing
30847 @subsection Taking advantage of 64-bit addressing
30850 * Making code 64 bit clean::
30851 * Allocating memory from the 64 bit storage pool::
30852 * Restrictions on use of 64 bit objects::
30853 * Using 64 bit storage pools by default::
30854 * General access types::
30855 * STARLET and other predefined libraries::
30858 @node Making code 64 bit clean
30859 @subsubsection Making code 64-bit clean
30862 In order to prevent problems that may occur when (parts of) a
30863 system start using memory outside the 32-bit address range,
30864 we recommend some additional guidelines:
30868 For imported subprograms that take parameters of the
30869 type @code{System.Address}, ensure that these subprograms can
30870 indeed handle 64-bit addresses. If not, or when in doubt,
30871 change the subprogram declaration to specify
30872 @code{System.Short_Address} instead.
30875 Resolve all warnings related to size mismatches in
30876 unchecked conversions. Failing to do so causes
30877 erroneous execution if the source object is outside
30878 the 32-bit address space.
30881 (optional) Explicitly use the 32-bit storage pool
30882 for access types used in a 32-bit context, or use
30883 generic access types where possible
30884 (@pxref{Restrictions on use of 64 bit objects}).
30888 If these rules are followed, the compiler will automatically insert
30889 any necessary checks to ensure that no addresses or access values
30890 passed to 32-bit code ever refer to objects outside the 32-bit
30892 Any attempt to do this will raise @code{Constraint_Error}.
30894 @node Allocating memory from the 64 bit storage pool
30895 @subsubsection Allocating memory from the 64-bit storage pool
30898 For any access type @code{T} that potentially requires memory allocations
30899 beyond the 32-bit address space,
30900 use the following representation clause:
30902 @smallexample @c ada
30903 for T'Storage_Pool use System.Pool_64;
30906 @node Restrictions on use of 64 bit objects
30907 @subsubsection Restrictions on use of 64-bit objects
30910 Taking the address of an object allocated from a 64-bit storage pool,
30911 and then passing this address to a subprogram expecting
30912 @code{System.Short_Address},
30913 or assigning it to a variable of type @code{Short_Address}, will cause
30914 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
30915 (@pxref{Making code 64 bit clean}), or checks are suppressed,
30916 no exception is raised and execution
30917 will become erroneous.
30919 @node Using 64 bit storage pools by default
30920 @subsubsection Using 64-bit storage pools by default
30923 In some cases it may be desirable to have the compiler allocate
30924 from 64-bit storage pools by default. This may be the case for
30925 libraries that are 64-bit clean, but may be used in both 32-bit
30926 and 64-bit contexts. For these cases the following configuration
30927 pragma may be specified:
30929 @smallexample @c ada
30930 pragma Pool_64_Default;
30934 Any code compiled in the context of this pragma will by default
30935 use the @code{System.Pool_64} storage pool. This default may be overridden
30936 for a specific access type @code{T} by the representation clause:
30938 @smallexample @c ada
30939 for T'Storage_Pool use System.Pool_32;
30943 Any object whose address may be passed to a subprogram with a
30944 @code{Short_Address} argument, or assigned to a variable of type
30945 @code{Short_Address}, needs to be allocated from this pool.
30947 @node General access types
30948 @subsubsection General access types
30951 Objects designated by access values from a
30952 general access type (declared with @code{access all}) are never allocated
30953 from a 64-bit storage pool. Code that uses general access types will
30954 accept objects allocated in either 32-bit or 64-bit address spaces,
30955 but never allocate objects outside the 32-bit address space.
30956 Using general access types ensures maximum compatibility with both
30957 32-bit and 64-bit code.
30959 @node STARLET and other predefined libraries
30960 @subsubsection STARLET and other predefined libraries
30963 All code that comes as part of GNAT is 64-bit clean, but the
30964 restrictions given in @ref{Restrictions on use of 64 bit objects},
30965 still apply. Look at the package
30966 specs to see in which contexts objects allocated
30967 in 64-bit address space are acceptable.
30969 @node Technical details
30970 @subsection Technical details
30973 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
30974 Ada standard with respect to the type of @code{System.Address}. Previous
30975 versions of GNAT Pro have defined this type as private and implemented it as a
30978 In order to allow defining @code{System.Short_Address} as a proper subtype,
30979 and to match the implicit sign extension in parameter passing,
30980 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
30981 visible (i.e., non-private) integer type.
30982 Standard operations on the type, such as the binary operators ``+'', ``-'',
30983 etc., that take @code{Address} operands and return an @code{Address} result,
30984 have been hidden by declaring these
30985 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
30986 ambiguities that would otherwise result from overloading.
30987 (Note that, although @code{Address} is a visible integer type,
30988 good programming practice dictates against exploiting the type's
30989 integer properties such as literals, since this will compromise
30992 Defining @code{Address} as a visible integer type helps achieve
30993 maximum compatibility for existing Ada code,
30994 without sacrificing the capabilities of the 64-bit architecture.
30997 @c ************************************************
30999 @node Microsoft Windows Topics
31000 @appendix Microsoft Windows Topics
31006 This chapter describes topics that are specific to the Microsoft Windows
31007 platforms (NT, 2000, and XP Professional).
31010 * Using GNAT on Windows::
31011 * Using a network installation of GNAT::
31012 * CONSOLE and WINDOWS subsystems::
31013 * Temporary Files::
31014 * Mixed-Language Programming on Windows::
31015 * Windows Calling Conventions::
31016 * Introduction to Dynamic Link Libraries (DLLs)::
31017 * Using DLLs with GNAT::
31018 * Building DLLs with GNAT::
31019 * Building DLLs with GNAT Project files::
31020 * Building DLLs with gnatdll::
31021 * GNAT and Windows Resources::
31022 * Debugging a DLL::
31023 * Setting Stack Size from gnatlink::
31024 * Setting Heap Size from gnatlink::
31027 @node Using GNAT on Windows
31028 @section Using GNAT on Windows
31031 One of the strengths of the GNAT technology is that its tool set
31032 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31033 @code{gdb} debugger, etc.) is used in the same way regardless of the
31036 On Windows this tool set is complemented by a number of Microsoft-specific
31037 tools that have been provided to facilitate interoperability with Windows
31038 when this is required. With these tools:
31043 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31047 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31048 relocatable and non-relocatable DLLs are supported).
31051 You can build Ada DLLs for use in other applications. These applications
31052 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31053 relocatable and non-relocatable Ada DLLs are supported.
31056 You can include Windows resources in your Ada application.
31059 You can use or create COM/DCOM objects.
31063 Immediately below are listed all known general GNAT-for-Windows restrictions.
31064 Other restrictions about specific features like Windows Resources and DLLs
31065 are listed in separate sections below.
31070 It is not possible to use @code{GetLastError} and @code{SetLastError}
31071 when tasking, protected records, or exceptions are used. In these
31072 cases, in order to implement Ada semantics, the GNAT run-time system
31073 calls certain Win32 routines that set the last error variable to 0 upon
31074 success. It should be possible to use @code{GetLastError} and
31075 @code{SetLastError} when tasking, protected record, and exception
31076 features are not used, but it is not guaranteed to work.
31079 It is not possible to link against Microsoft libraries except for
31080 import libraries. The library must be built to be compatible with
31081 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31082 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31083 not be compatible with the GNAT runtime. Even if the library is
31084 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31087 When the compilation environment is located on FAT32 drives, users may
31088 experience recompilations of the source files that have not changed if
31089 Daylight Saving Time (DST) state has changed since the last time files
31090 were compiled. NTFS drives do not have this problem.
31093 No components of the GNAT toolset use any entries in the Windows
31094 registry. The only entries that can be created are file associations and
31095 PATH settings, provided the user has chosen to create them at installation
31096 time, as well as some minimal book-keeping information needed to correctly
31097 uninstall or integrate different GNAT products.
31100 @node Using a network installation of GNAT
31101 @section Using a network installation of GNAT
31104 Make sure the system on which GNAT is installed is accessible from the
31105 current machine, i.e., the install location is shared over the network.
31106 Shared resources are accessed on Windows by means of UNC paths, which
31107 have the format @code{\\server\sharename\path}
31109 In order to use such a network installation, simply add the UNC path of the
31110 @file{bin} directory of your GNAT installation in front of your PATH. For
31111 example, if GNAT is installed in @file{\GNAT} directory of a share location
31112 called @file{c-drive} on a machine @file{LOKI}, the following command will
31115 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31117 Be aware that every compilation using the network installation results in the
31118 transfer of large amounts of data across the network and will likely cause
31119 serious performance penalty.
31121 @node CONSOLE and WINDOWS subsystems
31122 @section CONSOLE and WINDOWS subsystems
31123 @cindex CONSOLE Subsystem
31124 @cindex WINDOWS Subsystem
31128 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31129 (which is the default subsystem) will always create a console when
31130 launching the application. This is not something desirable when the
31131 application has a Windows GUI. To get rid of this console the
31132 application must be using the @code{WINDOWS} subsystem. To do so
31133 the @option{-mwindows} linker option must be specified.
31136 $ gnatmake winprog -largs -mwindows
31139 @node Temporary Files
31140 @section Temporary Files
31141 @cindex Temporary files
31144 It is possible to control where temporary files gets created by setting
31145 the @env{TMP} environment variable. The file will be created:
31148 @item Under the directory pointed to by the @env{TMP} environment variable if
31149 this directory exists.
31151 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31152 set (or not pointing to a directory) and if this directory exists.
31154 @item Under the current working directory otherwise.
31158 This allows you to determine exactly where the temporary
31159 file will be created. This is particularly useful in networked
31160 environments where you may not have write access to some
31163 @node Mixed-Language Programming on Windows
31164 @section Mixed-Language Programming on Windows
31167 Developing pure Ada applications on Windows is no different than on
31168 other GNAT-supported platforms. However, when developing or porting an
31169 application that contains a mix of Ada and C/C++, the choice of your
31170 Windows C/C++ development environment conditions your overall
31171 interoperability strategy.
31173 If you use @command{gcc} to compile the non-Ada part of your application,
31174 there are no Windows-specific restrictions that affect the overall
31175 interoperability with your Ada code. If you plan to use
31176 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31177 the following limitations:
31181 You cannot link your Ada code with an object or library generated with
31182 Microsoft tools if these use the @code{.tls} section (Thread Local
31183 Storage section) since the GNAT linker does not yet support this section.
31186 You cannot link your Ada code with an object or library generated with
31187 Microsoft tools if these use I/O routines other than those provided in
31188 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31189 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31190 libraries can cause a conflict with @code{msvcrt.dll} services. For
31191 instance Visual C++ I/O stream routines conflict with those in
31196 If you do want to use the Microsoft tools for your non-Ada code and hit one
31197 of the above limitations, you have two choices:
31201 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31202 application. In this case, use the Microsoft or whatever environment to
31203 build the DLL and use GNAT to build your executable
31204 (@pxref{Using DLLs with GNAT}).
31207 Or you can encapsulate your Ada code in a DLL to be linked with the
31208 other part of your application. In this case, use GNAT to build the DLL
31209 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31210 environment to build your executable.
31213 @node Windows Calling Conventions
31214 @section Windows Calling Conventions
31219 * C Calling Convention::
31220 * Stdcall Calling Convention::
31221 * Win32 Calling Convention::
31222 * DLL Calling Convention::
31226 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31227 (callee), there are several ways to push @code{G}'s parameters on the
31228 stack and there are several possible scenarios to clean up the stack
31229 upon @code{G}'s return. A calling convention is an agreed upon software
31230 protocol whereby the responsibilities between the caller (@code{F}) and
31231 the callee (@code{G}) are clearly defined. Several calling conventions
31232 are available for Windows:
31236 @code{C} (Microsoft defined)
31239 @code{Stdcall} (Microsoft defined)
31242 @code{Win32} (GNAT specific)
31245 @code{DLL} (GNAT specific)
31248 @node C Calling Convention
31249 @subsection @code{C} Calling Convention
31252 This is the default calling convention used when interfacing to C/C++
31253 routines compiled with either @command{gcc} or Microsoft Visual C++.
31255 In the @code{C} calling convention subprogram parameters are pushed on the
31256 stack by the caller from right to left. The caller itself is in charge of
31257 cleaning up the stack after the call. In addition, the name of a routine
31258 with @code{C} calling convention is mangled by adding a leading underscore.
31260 The name to use on the Ada side when importing (or exporting) a routine
31261 with @code{C} calling convention is the name of the routine. For
31262 instance the C function:
31265 int get_val (long);
31269 should be imported from Ada as follows:
31271 @smallexample @c ada
31273 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31274 pragma Import (C, Get_Val, External_Name => "get_val");
31279 Note that in this particular case the @code{External_Name} parameter could
31280 have been omitted since, when missing, this parameter is taken to be the
31281 name of the Ada entity in lower case. When the @code{Link_Name} parameter
31282 is missing, as in the above example, this parameter is set to be the
31283 @code{External_Name} with a leading underscore.
31285 When importing a variable defined in C, you should always use the @code{C}
31286 calling convention unless the object containing the variable is part of a
31287 DLL (in which case you should use the @code{Stdcall} calling
31288 convention, @pxref{Stdcall Calling Convention}).
31290 @node Stdcall Calling Convention
31291 @subsection @code{Stdcall} Calling Convention
31294 This convention, which was the calling convention used for Pascal
31295 programs, is used by Microsoft for all the routines in the Win32 API for
31296 efficiency reasons. It must be used to import any routine for which this
31297 convention was specified.
31299 In the @code{Stdcall} calling convention subprogram parameters are pushed
31300 on the stack by the caller from right to left. The callee (and not the
31301 caller) is in charge of cleaning the stack on routine exit. In addition,
31302 the name of a routine with @code{Stdcall} calling convention is mangled by
31303 adding a leading underscore (as for the @code{C} calling convention) and a
31304 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31305 bytes) of the parameters passed to the routine.
31307 The name to use on the Ada side when importing a C routine with a
31308 @code{Stdcall} calling convention is the name of the C routine. The leading
31309 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31310 the compiler. For instance the Win32 function:
31313 @b{APIENTRY} int get_val (long);
31317 should be imported from Ada as follows:
31319 @smallexample @c ada
31321 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31322 pragma Import (Stdcall, Get_Val);
31323 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31328 As for the @code{C} calling convention, when the @code{External_Name}
31329 parameter is missing, it is taken to be the name of the Ada entity in lower
31330 case. If instead of writing the above import pragma you write:
31332 @smallexample @c ada
31334 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31335 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31340 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31341 of specifying the @code{External_Name} parameter you specify the
31342 @code{Link_Name} as in the following example:
31344 @smallexample @c ada
31346 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31347 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31352 then the imported routine is @code{retrieve_val}, that is, there is no
31353 decoration at all. No leading underscore and no Stdcall suffix
31354 @code{@@}@code{@var{nn}}.
31357 This is especially important as in some special cases a DLL's entry
31358 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31359 name generated for a call has it.
31362 It is also possible to import variables defined in a DLL by using an
31363 import pragma for a variable. As an example, if a DLL contains a
31364 variable defined as:
31371 then, to access this variable from Ada you should write:
31373 @smallexample @c ada
31375 My_Var : Interfaces.C.int;
31376 pragma Import (Stdcall, My_Var);
31381 Note that to ease building cross-platform bindings this convention
31382 will be handled as a @code{C} calling convention on non-Windows platforms.
31384 @node Win32 Calling Convention
31385 @subsection @code{Win32} Calling Convention
31388 This convention, which is GNAT-specific is fully equivalent to the
31389 @code{Stdcall} calling convention described above.
31391 @node DLL Calling Convention
31392 @subsection @code{DLL} Calling Convention
31395 This convention, which is GNAT-specific is fully equivalent to the
31396 @code{Stdcall} calling convention described above.
31398 @node Introduction to Dynamic Link Libraries (DLLs)
31399 @section Introduction to Dynamic Link Libraries (DLLs)
31403 A Dynamically Linked Library (DLL) is a library that can be shared by
31404 several applications running under Windows. A DLL can contain any number of
31405 routines and variables.
31407 One advantage of DLLs is that you can change and enhance them without
31408 forcing all the applications that depend on them to be relinked or
31409 recompiled. However, you should be aware than all calls to DLL routines are
31410 slower since, as you will understand below, such calls are indirect.
31412 To illustrate the remainder of this section, suppose that an application
31413 wants to use the services of a DLL @file{API.dll}. To use the services
31414 provided by @file{API.dll} you must statically link against the DLL or
31415 an import library which contains a jump table with an entry for each
31416 routine and variable exported by the DLL. In the Microsoft world this
31417 import library is called @file{API.lib}. When using GNAT this import
31418 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31419 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31421 After you have linked your application with the DLL or the import library
31422 and you run your application, here is what happens:
31426 Your application is loaded into memory.
31429 The DLL @file{API.dll} is mapped into the address space of your
31430 application. This means that:
31434 The DLL will use the stack of the calling thread.
31437 The DLL will use the virtual address space of the calling process.
31440 The DLL will allocate memory from the virtual address space of the calling
31444 Handles (pointers) can be safely exchanged between routines in the DLL
31445 routines and routines in the application using the DLL.
31449 The entries in the jump table (from the import library @file{libAPI.dll.a}
31450 or @file{API.lib} or automatically created when linking against a DLL)
31451 which is part of your application are initialized with the addresses
31452 of the routines and variables in @file{API.dll}.
31455 If present in @file{API.dll}, routines @code{DllMain} or
31456 @code{DllMainCRTStartup} are invoked. These routines typically contain
31457 the initialization code needed for the well-being of the routines and
31458 variables exported by the DLL.
31462 There is an additional point which is worth mentioning. In the Windows
31463 world there are two kind of DLLs: relocatable and non-relocatable
31464 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31465 in the target application address space. If the addresses of two
31466 non-relocatable DLLs overlap and these happen to be used by the same
31467 application, a conflict will occur and the application will run
31468 incorrectly. Hence, when possible, it is always preferable to use and
31469 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31470 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31471 User's Guide) removes the debugging symbols from the DLL but the DLL can
31472 still be relocated.
31474 As a side note, an interesting difference between Microsoft DLLs and
31475 Unix shared libraries, is the fact that on most Unix systems all public
31476 routines are exported by default in a Unix shared library, while under
31477 Windows it is possible (but not required) to list exported routines in
31478 a definition file (@pxref{The Definition File}).
31480 @node Using DLLs with GNAT
31481 @section Using DLLs with GNAT
31484 * Creating an Ada Spec for the DLL Services::
31485 * Creating an Import Library::
31489 To use the services of a DLL, say @file{API.dll}, in your Ada application
31494 The Ada spec for the routines and/or variables you want to access in
31495 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31496 header files provided with the DLL.
31499 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31500 mentioned an import library is a statically linked library containing the
31501 import table which will be filled at load time to point to the actual
31502 @file{API.dll} routines. Sometimes you don't have an import library for the
31503 DLL you want to use. The following sections will explain how to build
31504 one. Note that this is optional.
31507 The actual DLL, @file{API.dll}.
31511 Once you have all the above, to compile an Ada application that uses the
31512 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31513 you simply issue the command
31516 $ gnatmake my_ada_app -largs -lAPI
31520 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31521 tells the GNAT linker to look first for a library named @file{API.lib}
31522 (Microsoft-style name) and if not found for a libraries named
31523 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31524 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31525 contains the following pragma
31527 @smallexample @c ada
31528 pragma Linker_Options ("-lAPI");
31532 you do not have to add @option{-largs -lAPI} at the end of the
31533 @command{gnatmake} command.
31535 If any one of the items above is missing you will have to create it
31536 yourself. The following sections explain how to do so using as an
31537 example a fictitious DLL called @file{API.dll}.
31539 @node Creating an Ada Spec for the DLL Services
31540 @subsection Creating an Ada Spec for the DLL Services
31543 A DLL typically comes with a C/C++ header file which provides the
31544 definitions of the routines and variables exported by the DLL. The Ada
31545 equivalent of this header file is a package spec that contains definitions
31546 for the imported entities. If the DLL you intend to use does not come with
31547 an Ada spec you have to generate one such spec yourself. For example if
31548 the header file of @file{API.dll} is a file @file{api.h} containing the
31549 following two definitions:
31561 then the equivalent Ada spec could be:
31563 @smallexample @c ada
31566 with Interfaces.C.Strings;
31571 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31574 pragma Import (C, Get);
31575 pragma Import (DLL, Some_Var);
31582 Note that a variable is
31583 @strong{always imported with a Stdcall convention}. A function
31584 can have @code{C} or @code{Stdcall} convention.
31585 (@pxref{Windows Calling Conventions}).
31587 @node Creating an Import Library
31588 @subsection Creating an Import Library
31589 @cindex Import library
31592 * The Definition File::
31593 * GNAT-Style Import Library::
31594 * Microsoft-Style Import Library::
31598 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31599 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31600 with @file{API.dll} you can skip this section. You can also skip this
31601 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31602 as in this case it is possible to link directly against the
31603 DLL. Otherwise read on.
31605 @node The Definition File
31606 @subsubsection The Definition File
31607 @cindex Definition file
31611 As previously mentioned, and unlike Unix systems, the list of symbols
31612 that are exported from a DLL must be provided explicitly in Windows.
31613 The main goal of a definition file is precisely that: list the symbols
31614 exported by a DLL. A definition file (usually a file with a @code{.def}
31615 suffix) has the following structure:
31620 @r{[}LIBRARY @var{name}@r{]}
31621 @r{[}DESCRIPTION @var{string}@r{]}
31631 @item LIBRARY @var{name}
31632 This section, which is optional, gives the name of the DLL.
31634 @item DESCRIPTION @var{string}
31635 This section, which is optional, gives a description string that will be
31636 embedded in the import library.
31639 This section gives the list of exported symbols (procedures, functions or
31640 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
31641 section of @file{API.def} looks like:
31655 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
31656 (@pxref{Windows Calling Conventions}) for a Stdcall
31657 calling convention function in the exported symbols list.
31660 There can actually be other sections in a definition file, but these
31661 sections are not relevant to the discussion at hand.
31663 @node GNAT-Style Import Library
31664 @subsubsection GNAT-Style Import Library
31667 To create a static import library from @file{API.dll} with the GNAT tools
31668 you should proceed as follows:
31672 Create the definition file @file{API.def} (@pxref{The Definition File}).
31673 For that use the @code{dll2def} tool as follows:
31676 $ dll2def API.dll > API.def
31680 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
31681 to standard output the list of entry points in the DLL. Note that if
31682 some routines in the DLL have the @code{Stdcall} convention
31683 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
31684 suffix then you'll have to edit @file{api.def} to add it, and specify
31685 @option{-k} to @command{gnatdll} when creating the import library.
31688 Here are some hints to find the right @code{@@}@var{nn} suffix.
31692 If you have the Microsoft import library (.lib), it is possible to get
31693 the right symbols by using Microsoft @code{dumpbin} tool (see the
31694 corresponding Microsoft documentation for further details).
31697 $ dumpbin /exports api.lib
31701 If you have a message about a missing symbol at link time the compiler
31702 tells you what symbol is expected. You just have to go back to the
31703 definition file and add the right suffix.
31707 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
31708 (@pxref{Using gnatdll}) as follows:
31711 $ gnatdll -e API.def -d API.dll
31715 @code{gnatdll} takes as input a definition file @file{API.def} and the
31716 name of the DLL containing the services listed in the definition file
31717 @file{API.dll}. The name of the static import library generated is
31718 computed from the name of the definition file as follows: if the
31719 definition file name is @var{xyz}@code{.def}, the import library name will
31720 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
31721 @option{-e} could have been removed because the name of the definition
31722 file (before the ``@code{.def}'' suffix) is the same as the name of the
31723 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
31726 @node Microsoft-Style Import Library
31727 @subsubsection Microsoft-Style Import Library
31730 With GNAT you can either use a GNAT-style or Microsoft-style import
31731 library. A Microsoft import library is needed only if you plan to make an
31732 Ada DLL available to applications developed with Microsoft
31733 tools (@pxref{Mixed-Language Programming on Windows}).
31735 To create a Microsoft-style import library for @file{API.dll} you
31736 should proceed as follows:
31740 Create the definition file @file{API.def} from the DLL. For this use either
31741 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
31742 tool (see the corresponding Microsoft documentation for further details).
31745 Build the actual import library using Microsoft's @code{lib} utility:
31748 $ lib -machine:IX86 -def:API.def -out:API.lib
31752 If you use the above command the definition file @file{API.def} must
31753 contain a line giving the name of the DLL:
31760 See the Microsoft documentation for further details about the usage of
31764 @node Building DLLs with GNAT
31765 @section Building DLLs with GNAT
31766 @cindex DLLs, building
31769 This section explain how to build DLLs using the GNAT built-in DLL
31770 support. With the following procedure it is straight forward to build
31771 and use DLLs with GNAT.
31775 @item building object files
31777 The first step is to build all objects files that are to be included
31778 into the DLL. This is done by using the standard @command{gnatmake} tool.
31780 @item building the DLL
31782 To build the DLL you must use @command{gcc}'s @option{-shared}
31783 option. It is quite simple to use this method:
31786 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
31789 It is important to note that in this case all symbols found in the
31790 object files are automatically exported. It is possible to restrict
31791 the set of symbols to export by passing to @command{gcc} a definition
31792 file, @pxref{The Definition File}. For example:
31795 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
31798 If you use a definition file you must export the elaboration procedures
31799 for every package that required one. Elaboration procedures are named
31800 using the package name followed by "_E".
31802 @item preparing DLL to be used
31804 For the DLL to be used by client programs the bodies must be hidden
31805 from it and the .ali set with read-only attribute. This is very important
31806 otherwise GNAT will recompile all packages and will not actually use
31807 the code in the DLL. For example:
31811 $ copy *.ads *.ali api.dll apilib
31812 $ attrib +R apilib\*.ali
31817 At this point it is possible to use the DLL by directly linking
31818 against it. Note that you must use the GNAT shared runtime when using
31819 GNAT shared libraries. This is achieved by using @option{-shared} binder's
31823 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
31826 @node Building DLLs with GNAT Project files
31827 @section Building DLLs with GNAT Project files
31828 @cindex DLLs, building
31831 There is nothing specific to Windows in the build process.
31832 @pxref{Library Projects}.
31835 Due to a system limitation, it is not possible under Windows to create threads
31836 when inside the @code{DllMain} routine which is used for auto-initialization
31837 of shared libraries, so it is not possible to have library level tasks in SALs.
31839 @node Building DLLs with gnatdll
31840 @section Building DLLs with gnatdll
31841 @cindex DLLs, building
31844 * Limitations When Using Ada DLLs from Ada::
31845 * Exporting Ada Entities::
31846 * Ada DLLs and Elaboration::
31847 * Ada DLLs and Finalization::
31848 * Creating a Spec for Ada DLLs::
31849 * Creating the Definition File::
31854 Note that it is preferred to use the built-in GNAT DLL support
31855 (@pxref{Building DLLs with GNAT}) or GNAT Project files
31856 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
31858 This section explains how to build DLLs containing Ada code using
31859 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
31860 remainder of this section.
31862 The steps required to build an Ada DLL that is to be used by Ada as well as
31863 non-Ada applications are as follows:
31867 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
31868 @code{Stdcall} calling convention to avoid any Ada name mangling for the
31869 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
31870 skip this step if you plan to use the Ada DLL only from Ada applications.
31873 Your Ada code must export an initialization routine which calls the routine
31874 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
31875 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
31876 routine exported by the Ada DLL must be invoked by the clients of the DLL
31877 to initialize the DLL.
31880 When useful, the DLL should also export a finalization routine which calls
31881 routine @code{adafinal} generated by @command{gnatbind} to perform the
31882 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
31883 The finalization routine exported by the Ada DLL must be invoked by the
31884 clients of the DLL when the DLL services are no further needed.
31887 You must provide a spec for the services exported by the Ada DLL in each
31888 of the programming languages to which you plan to make the DLL available.
31891 You must provide a definition file listing the exported entities
31892 (@pxref{The Definition File}).
31895 Finally you must use @code{gnatdll} to produce the DLL and the import
31896 library (@pxref{Using gnatdll}).
31900 Note that a relocatable DLL stripped using the @code{strip}
31901 binutils tool will not be relocatable anymore. To build a DLL without
31902 debug information pass @code{-largs -s} to @code{gnatdll}. This
31903 restriction does not apply to a DLL built using a Library Project.
31904 @pxref{Library Projects}.
31906 @node Limitations When Using Ada DLLs from Ada
31907 @subsection Limitations When Using Ada DLLs from Ada
31910 When using Ada DLLs from Ada applications there is a limitation users
31911 should be aware of. Because on Windows the GNAT run time is not in a DLL of
31912 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
31913 each Ada DLL includes the services of the GNAT run time that are necessary
31914 to the Ada code inside the DLL. As a result, when an Ada program uses an
31915 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
31916 one in the main program.
31918 It is therefore not possible to exchange GNAT run-time objects between the
31919 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
31920 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
31923 It is completely safe to exchange plain elementary, array or record types,
31924 Windows object handles, etc.
31926 @node Exporting Ada Entities
31927 @subsection Exporting Ada Entities
31928 @cindex Export table
31931 Building a DLL is a way to encapsulate a set of services usable from any
31932 application. As a result, the Ada entities exported by a DLL should be
31933 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
31934 any Ada name mangling. As an example here is an Ada package
31935 @code{API}, spec and body, exporting two procedures, a function, and a
31938 @smallexample @c ada
31941 with Interfaces.C; use Interfaces;
31943 Count : C.int := 0;
31944 function Factorial (Val : C.int) return C.int;
31946 procedure Initialize_API;
31947 procedure Finalize_API;
31948 -- Initialization & Finalization routines. More in the next section.
31950 pragma Export (C, Initialize_API);
31951 pragma Export (C, Finalize_API);
31952 pragma Export (C, Count);
31953 pragma Export (C, Factorial);
31959 @smallexample @c ada
31962 package body API is
31963 function Factorial (Val : C.int) return C.int is
31966 Count := Count + 1;
31967 for K in 1 .. Val loop
31973 procedure Initialize_API is
31975 pragma Import (C, Adainit);
31978 end Initialize_API;
31980 procedure Finalize_API is
31981 procedure Adafinal;
31982 pragma Import (C, Adafinal);
31992 If the Ada DLL you are building will only be used by Ada applications
31993 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
31994 convention. As an example, the previous package could be written as
31997 @smallexample @c ada
32001 Count : Integer := 0;
32002 function Factorial (Val : Integer) return Integer;
32004 procedure Initialize_API;
32005 procedure Finalize_API;
32006 -- Initialization and Finalization routines.
32012 @smallexample @c ada
32015 package body API is
32016 function Factorial (Val : Integer) return Integer is
32017 Fact : Integer := 1;
32019 Count := Count + 1;
32020 for K in 1 .. Val loop
32027 -- The remainder of this package body is unchanged.
32034 Note that if you do not export the Ada entities with a @code{C} or
32035 @code{Stdcall} convention you will have to provide the mangled Ada names
32036 in the definition file of the Ada DLL
32037 (@pxref{Creating the Definition File}).
32039 @node Ada DLLs and Elaboration
32040 @subsection Ada DLLs and Elaboration
32041 @cindex DLLs and elaboration
32044 The DLL that you are building contains your Ada code as well as all the
32045 routines in the Ada library that are needed by it. The first thing a
32046 user of your DLL must do is elaborate the Ada code
32047 (@pxref{Elaboration Order Handling in GNAT}).
32049 To achieve this you must export an initialization routine
32050 (@code{Initialize_API} in the previous example), which must be invoked
32051 before using any of the DLL services. This elaboration routine must call
32052 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32053 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32054 @code{Initialize_Api} for an example. Note that the GNAT binder is
32055 automatically invoked during the DLL build process by the @code{gnatdll}
32056 tool (@pxref{Using gnatdll}).
32058 When a DLL is loaded, Windows systematically invokes a routine called
32059 @code{DllMain}. It would therefore be possible to call @code{adainit}
32060 directly from @code{DllMain} without having to provide an explicit
32061 initialization routine. Unfortunately, it is not possible to call
32062 @code{adainit} from the @code{DllMain} if your program has library level
32063 tasks because access to the @code{DllMain} entry point is serialized by
32064 the system (that is, only a single thread can execute ``through'' it at a
32065 time), which means that the GNAT run time will deadlock waiting for the
32066 newly created task to complete its initialization.
32068 @node Ada DLLs and Finalization
32069 @subsection Ada DLLs and Finalization
32070 @cindex DLLs and finalization
32073 When the services of an Ada DLL are no longer needed, the client code should
32074 invoke the DLL finalization routine, if available. The DLL finalization
32075 routine is in charge of releasing all resources acquired by the DLL. In the
32076 case of the Ada code contained in the DLL, this is achieved by calling
32077 routine @code{adafinal} generated by the GNAT binder
32078 (@pxref{Binding with Non-Ada Main Programs}).
32079 See the body of @code{Finalize_Api} for an
32080 example. As already pointed out the GNAT binder is automatically invoked
32081 during the DLL build process by the @code{gnatdll} tool
32082 (@pxref{Using gnatdll}).
32084 @node Creating a Spec for Ada DLLs
32085 @subsection Creating a Spec for Ada DLLs
32088 To use the services exported by the Ada DLL from another programming
32089 language (e.g.@: C), you have to translate the specs of the exported Ada
32090 entities in that language. For instance in the case of @code{API.dll},
32091 the corresponding C header file could look like:
32096 extern int *_imp__count;
32097 #define count (*_imp__count)
32098 int factorial (int);
32104 It is important to understand that when building an Ada DLL to be used by
32105 other Ada applications, you need two different specs for the packages
32106 contained in the DLL: one for building the DLL and the other for using
32107 the DLL. This is because the @code{DLL} calling convention is needed to
32108 use a variable defined in a DLL, but when building the DLL, the variable
32109 must have either the @code{Ada} or @code{C} calling convention. As an
32110 example consider a DLL comprising the following package @code{API}:
32112 @smallexample @c ada
32116 Count : Integer := 0;
32118 -- Remainder of the package omitted.
32125 After producing a DLL containing package @code{API}, the spec that
32126 must be used to import @code{API.Count} from Ada code outside of the
32129 @smallexample @c ada
32134 pragma Import (DLL, Count);
32140 @node Creating the Definition File
32141 @subsection Creating the Definition File
32144 The definition file is the last file needed to build the DLL. It lists
32145 the exported symbols. As an example, the definition file for a DLL
32146 containing only package @code{API} (where all the entities are exported
32147 with a @code{C} calling convention) is:
32162 If the @code{C} calling convention is missing from package @code{API},
32163 then the definition file contains the mangled Ada names of the above
32164 entities, which in this case are:
32173 api__initialize_api
32178 @node Using gnatdll
32179 @subsection Using @code{gnatdll}
32183 * gnatdll Example::
32184 * gnatdll behind the Scenes::
32189 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32190 and non-Ada sources that make up your DLL have been compiled.
32191 @code{gnatdll} is actually in charge of two distinct tasks: build the
32192 static import library for the DLL and the actual DLL. The form of the
32193 @code{gnatdll} command is
32197 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32202 where @var{list-of-files} is a list of ALI and object files. The object
32203 file list must be the exact list of objects corresponding to the non-Ada
32204 sources whose services are to be included in the DLL. The ALI file list
32205 must be the exact list of ALI files for the corresponding Ada sources
32206 whose services are to be included in the DLL. If @var{list-of-files} is
32207 missing, only the static import library is generated.
32210 You may specify any of the following switches to @code{gnatdll}:
32213 @item -a@ovar{address}
32214 @cindex @option{-a} (@code{gnatdll})
32215 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32216 specified the default address @var{0x11000000} will be used. By default,
32217 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32218 advise the reader to build relocatable DLL.
32220 @item -b @var{address}
32221 @cindex @option{-b} (@code{gnatdll})
32222 Set the relocatable DLL base address. By default the address is
32225 @item -bargs @var{opts}
32226 @cindex @option{-bargs} (@code{gnatdll})
32227 Binder options. Pass @var{opts} to the binder.
32229 @item -d @var{dllfile}
32230 @cindex @option{-d} (@code{gnatdll})
32231 @var{dllfile} is the name of the DLL. This switch must be present for
32232 @code{gnatdll} to do anything. The name of the generated import library is
32233 obtained algorithmically from @var{dllfile} as shown in the following
32234 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32235 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32236 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32237 as shown in the following example:
32238 if @var{dllfile} is @code{xyz.dll}, the definition
32239 file used is @code{xyz.def}.
32241 @item -e @var{deffile}
32242 @cindex @option{-e} (@code{gnatdll})
32243 @var{deffile} is the name of the definition file.
32246 @cindex @option{-g} (@code{gnatdll})
32247 Generate debugging information. This information is stored in the object
32248 file and copied from there to the final DLL file by the linker,
32249 where it can be read by the debugger. You must use the
32250 @option{-g} switch if you plan on using the debugger or the symbolic
32254 @cindex @option{-h} (@code{gnatdll})
32255 Help mode. Displays @code{gnatdll} switch usage information.
32258 @cindex @option{-I} (@code{gnatdll})
32259 Direct @code{gnatdll} to search the @var{dir} directory for source and
32260 object files needed to build the DLL.
32261 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32264 @cindex @option{-k} (@code{gnatdll})
32265 Removes the @code{@@}@var{nn} suffix from the import library's exported
32266 names, but keeps them for the link names. You must specify this
32267 option if you want to use a @code{Stdcall} function in a DLL for which
32268 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32269 of the Windows NT DLL for example. This option has no effect when
32270 @option{-n} option is specified.
32272 @item -l @var{file}
32273 @cindex @option{-l} (@code{gnatdll})
32274 The list of ALI and object files used to build the DLL are listed in
32275 @var{file}, instead of being given in the command line. Each line in
32276 @var{file} contains the name of an ALI or object file.
32279 @cindex @option{-n} (@code{gnatdll})
32280 No Import. Do not create the import library.
32283 @cindex @option{-q} (@code{gnatdll})
32284 Quiet mode. Do not display unnecessary messages.
32287 @cindex @option{-v} (@code{gnatdll})
32288 Verbose mode. Display extra information.
32290 @item -largs @var{opts}
32291 @cindex @option{-largs} (@code{gnatdll})
32292 Linker options. Pass @var{opts} to the linker.
32295 @node gnatdll Example
32296 @subsubsection @code{gnatdll} Example
32299 As an example the command to build a relocatable DLL from @file{api.adb}
32300 once @file{api.adb} has been compiled and @file{api.def} created is
32303 $ gnatdll -d api.dll api.ali
32307 The above command creates two files: @file{libapi.dll.a} (the import
32308 library) and @file{api.dll} (the actual DLL). If you want to create
32309 only the DLL, just type:
32312 $ gnatdll -d api.dll -n api.ali
32316 Alternatively if you want to create just the import library, type:
32319 $ gnatdll -d api.dll
32322 @node gnatdll behind the Scenes
32323 @subsubsection @code{gnatdll} behind the Scenes
32326 This section details the steps involved in creating a DLL. @code{gnatdll}
32327 does these steps for you. Unless you are interested in understanding what
32328 goes on behind the scenes, you should skip this section.
32330 We use the previous example of a DLL containing the Ada package @code{API},
32331 to illustrate the steps necessary to build a DLL. The starting point is a
32332 set of objects that will make up the DLL and the corresponding ALI
32333 files. In the case of this example this means that @file{api.o} and
32334 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32339 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32340 the information necessary to generate relocation information for the
32346 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32351 In addition to the base file, the @command{gnatlink} command generates an
32352 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32353 asks @command{gnatlink} to generate the routines @code{DllMain} and
32354 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32355 is loaded into memory.
32358 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32359 export table (@file{api.exp}). The export table contains the relocation
32360 information in a form which can be used during the final link to ensure
32361 that the Windows loader is able to place the DLL anywhere in memory.
32365 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32366 --output-exp api.exp
32371 @code{gnatdll} builds the base file using the new export table. Note that
32372 @command{gnatbind} must be called once again since the binder generated file
32373 has been deleted during the previous call to @command{gnatlink}.
32378 $ gnatlink api -o api.jnk api.exp -mdll
32379 -Wl,--base-file,api.base
32384 @code{gnatdll} builds the new export table using the new base file and
32385 generates the DLL import library @file{libAPI.dll.a}.
32389 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32390 --output-exp api.exp --output-lib libAPI.a
32395 Finally @code{gnatdll} builds the relocatable DLL using the final export
32401 $ gnatlink api api.exp -o api.dll -mdll
32406 @node Using dlltool
32407 @subsubsection Using @code{dlltool}
32410 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32411 DLLs and static import libraries. This section summarizes the most
32412 common @code{dlltool} switches. The form of the @code{dlltool} command
32416 $ dlltool @ovar{switches}
32420 @code{dlltool} switches include:
32423 @item --base-file @var{basefile}
32424 @cindex @option{--base-file} (@command{dlltool})
32425 Read the base file @var{basefile} generated by the linker. This switch
32426 is used to create a relocatable DLL.
32428 @item --def @var{deffile}
32429 @cindex @option{--def} (@command{dlltool})
32430 Read the definition file.
32432 @item --dllname @var{name}
32433 @cindex @option{--dllname} (@command{dlltool})
32434 Gives the name of the DLL. This switch is used to embed the name of the
32435 DLL in the static import library generated by @code{dlltool} with switch
32436 @option{--output-lib}.
32439 @cindex @option{-k} (@command{dlltool})
32440 Kill @code{@@}@var{nn} from exported names
32441 (@pxref{Windows Calling Conventions}
32442 for a discussion about @code{Stdcall}-style symbols.
32445 @cindex @option{--help} (@command{dlltool})
32446 Prints the @code{dlltool} switches with a concise description.
32448 @item --output-exp @var{exportfile}
32449 @cindex @option{--output-exp} (@command{dlltool})
32450 Generate an export file @var{exportfile}. The export file contains the
32451 export table (list of symbols in the DLL) and is used to create the DLL.
32453 @item --output-lib @var{libfile}
32454 @cindex @option{--output-lib} (@command{dlltool})
32455 Generate a static import library @var{libfile}.
32458 @cindex @option{-v} (@command{dlltool})
32461 @item --as @var{assembler-name}
32462 @cindex @option{--as} (@command{dlltool})
32463 Use @var{assembler-name} as the assembler. The default is @code{as}.
32466 @node GNAT and Windows Resources
32467 @section GNAT and Windows Resources
32468 @cindex Resources, windows
32471 * Building Resources::
32472 * Compiling Resources::
32473 * Using Resources::
32477 Resources are an easy way to add Windows specific objects to your
32478 application. The objects that can be added as resources include:
32507 This section explains how to build, compile and use resources.
32509 @node Building Resources
32510 @subsection Building Resources
32511 @cindex Resources, building
32514 A resource file is an ASCII file. By convention resource files have an
32515 @file{.rc} extension.
32516 The easiest way to build a resource file is to use Microsoft tools
32517 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32518 @code{dlgedit.exe} to build dialogs.
32519 It is always possible to build an @file{.rc} file yourself by writing a
32522 It is not our objective to explain how to write a resource file. A
32523 complete description of the resource script language can be found in the
32524 Microsoft documentation.
32526 @node Compiling Resources
32527 @subsection Compiling Resources
32530 @cindex Resources, compiling
32533 This section describes how to build a GNAT-compatible (COFF) object file
32534 containing the resources. This is done using the Resource Compiler
32535 @code{windres} as follows:
32538 $ windres -i myres.rc -o myres.o
32542 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32543 file. You can specify an alternate preprocessor (usually named
32544 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32545 parameter. A list of all possible options may be obtained by entering
32546 the command @code{windres} @option{--help}.
32548 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32549 to produce a @file{.res} file (binary resource file). See the
32550 corresponding Microsoft documentation for further details. In this case
32551 you need to use @code{windres} to translate the @file{.res} file to a
32552 GNAT-compatible object file as follows:
32555 $ windres -i myres.res -o myres.o
32558 @node Using Resources
32559 @subsection Using Resources
32560 @cindex Resources, using
32563 To include the resource file in your program just add the
32564 GNAT-compatible object file for the resource(s) to the linker
32565 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32569 $ gnatmake myprog -largs myres.o
32572 @node Debugging a DLL
32573 @section Debugging a DLL
32574 @cindex DLL debugging
32577 * Program and DLL Both Built with GCC/GNAT::
32578 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32582 Debugging a DLL is similar to debugging a standard program. But
32583 we have to deal with two different executable parts: the DLL and the
32584 program that uses it. We have the following four possibilities:
32588 The program and the DLL are built with @code{GCC/GNAT}.
32590 The program is built with foreign tools and the DLL is built with
32593 The program is built with @code{GCC/GNAT} and the DLL is built with
32599 In this section we address only cases one and two above.
32600 There is no point in trying to debug
32601 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32602 information in it. To do so you must use a debugger compatible with the
32603 tools suite used to build the DLL.
32605 @node Program and DLL Both Built with GCC/GNAT
32606 @subsection Program and DLL Both Built with GCC/GNAT
32609 This is the simplest case. Both the DLL and the program have @code{GDB}
32610 compatible debugging information. It is then possible to break anywhere in
32611 the process. Let's suppose here that the main procedure is named
32612 @code{ada_main} and that in the DLL there is an entry point named
32616 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32617 program must have been built with the debugging information (see GNAT -g
32618 switch). Here are the step-by-step instructions for debugging it:
32621 @item Launch @code{GDB} on the main program.
32627 @item Start the program and stop at the beginning of the main procedure
32634 This step is required to be able to set a breakpoint inside the DLL. As long
32635 as the program is not run, the DLL is not loaded. This has the
32636 consequence that the DLL debugging information is also not loaded, so it is not
32637 possible to set a breakpoint in the DLL.
32639 @item Set a breakpoint inside the DLL
32642 (gdb) break ada_dll
32649 At this stage a breakpoint is set inside the DLL. From there on
32650 you can use the standard approach to debug the whole program
32651 (@pxref{Running and Debugging Ada Programs}).
32654 @c This used to work, probably because the DLLs were non-relocatable
32655 @c keep this section around until the problem is sorted out.
32657 To break on the @code{DllMain} routine it is not possible to follow
32658 the procedure above. At the time the program stop on @code{ada_main}
32659 the @code{DllMain} routine as already been called. Either you can use
32660 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
32663 @item Launch @code{GDB} on the main program.
32669 @item Load DLL symbols
32672 (gdb) add-sym api.dll
32675 @item Set a breakpoint inside the DLL
32678 (gdb) break ada_dll.adb:45
32681 Note that at this point it is not possible to break using the routine symbol
32682 directly as the program is not yet running. The solution is to break
32683 on the proper line (break in @file{ada_dll.adb} line 45).
32685 @item Start the program
32694 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
32695 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
32698 * Debugging the DLL Directly::
32699 * Attaching to a Running Process::
32703 In this case things are slightly more complex because it is not possible to
32704 start the main program and then break at the beginning to load the DLL and the
32705 associated DLL debugging information. It is not possible to break at the
32706 beginning of the program because there is no @code{GDB} debugging information,
32707 and therefore there is no direct way of getting initial control. This
32708 section addresses this issue by describing some methods that can be used
32709 to break somewhere in the DLL to debug it.
32712 First suppose that the main procedure is named @code{main} (this is for
32713 example some C code built with Microsoft Visual C) and that there is a
32714 DLL named @code{test.dll} containing an Ada entry point named
32718 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
32719 been built with debugging information (see GNAT -g option).
32721 @node Debugging the DLL Directly
32722 @subsubsection Debugging the DLL Directly
32726 Find out the executable starting address
32729 $ objdump --file-header main.exe
32732 The starting address is reported on the last line. For example:
32735 main.exe: file format pei-i386
32736 architecture: i386, flags 0x0000010a:
32737 EXEC_P, HAS_DEBUG, D_PAGED
32738 start address 0x00401010
32742 Launch the debugger on the executable.
32749 Set a breakpoint at the starting address, and launch the program.
32752 $ (gdb) break *0x00401010
32756 The program will stop at the given address.
32759 Set a breakpoint on a DLL subroutine.
32762 (gdb) break ada_dll.adb:45
32765 Or if you want to break using a symbol on the DLL, you need first to
32766 select the Ada language (language used by the DLL).
32769 (gdb) set language ada
32770 (gdb) break ada_dll
32774 Continue the program.
32781 This will run the program until it reaches the breakpoint that has been
32782 set. From that point you can use the standard way to debug a program
32783 as described in (@pxref{Running and Debugging Ada Programs}).
32788 It is also possible to debug the DLL by attaching to a running process.
32790 @node Attaching to a Running Process
32791 @subsubsection Attaching to a Running Process
32792 @cindex DLL debugging, attach to process
32795 With @code{GDB} it is always possible to debug a running process by
32796 attaching to it. It is possible to debug a DLL this way. The limitation
32797 of this approach is that the DLL must run long enough to perform the
32798 attach operation. It may be useful for instance to insert a time wasting
32799 loop in the code of the DLL to meet this criterion.
32803 @item Launch the main program @file{main.exe}.
32809 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
32810 that the process PID for @file{main.exe} is 208.
32818 @item Attach to the running process to be debugged.
32824 @item Load the process debugging information.
32827 (gdb) symbol-file main.exe
32830 @item Break somewhere in the DLL.
32833 (gdb) break ada_dll
32836 @item Continue process execution.
32845 This last step will resume the process execution, and stop at
32846 the breakpoint we have set. From there you can use the standard
32847 approach to debug a program as described in
32848 (@pxref{Running and Debugging Ada Programs}).
32850 @node Setting Stack Size from gnatlink
32851 @section Setting Stack Size from @command{gnatlink}
32854 It is possible to specify the program stack size at link time. On modern
32855 versions of Windows, starting with XP, this is mostly useful to set the size of
32856 the main stack (environment task). The other task stacks are set with pragma
32857 Storage_Size or with the @command{gnatbind -d} command.
32859 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
32860 reserve size of individual tasks, the link-time stack size applies to all
32861 tasks, and pragma Storage_Size has no effect.
32862 In particular, Stack Overflow checks are made against this
32863 link-time specified size.
32865 This setting can be done with
32866 @command{gnatlink} using either:
32870 @item using @option{-Xlinker} linker option
32873 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
32876 This sets the stack reserve size to 0x10000 bytes and the stack commit
32877 size to 0x1000 bytes.
32879 @item using @option{-Wl} linker option
32882 $ gnatlink hello -Wl,--stack=0x1000000
32885 This sets the stack reserve size to 0x1000000 bytes. Note that with
32886 @option{-Wl} option it is not possible to set the stack commit size
32887 because the coma is a separator for this option.
32891 @node Setting Heap Size from gnatlink
32892 @section Setting Heap Size from @command{gnatlink}
32895 Under Windows systems, it is possible to specify the program heap size from
32896 @command{gnatlink} using either:
32900 @item using @option{-Xlinker} linker option
32903 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
32906 This sets the heap reserve size to 0x10000 bytes and the heap commit
32907 size to 0x1000 bytes.
32909 @item using @option{-Wl} linker option
32912 $ gnatlink hello -Wl,--heap=0x1000000
32915 This sets the heap reserve size to 0x1000000 bytes. Note that with
32916 @option{-Wl} option it is not possible to set the heap commit size
32917 because the coma is a separator for this option.
32923 @c **********************************
32924 @c * GNU Free Documentation License *
32925 @c **********************************
32927 @c GNU Free Documentation License
32929 @node Index,,GNU Free Documentation License, Top
32935 @c Put table of contents at end, otherwise it precedes the "title page" in
32936 @c the .txt version
32937 @c Edit the pdf file to move the contents to the beginning, after the title