1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
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14 @setfilename gnat_ugn.info
17 Copyright @copyright{} 1995-2009 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.2 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
71 @c cause the document build to fail.
73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
81 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
84 @c This flag is used where the text refers to conditions that exist when the
85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * Generating Ada Bindings for C and C++ headers::
191 * Other Utility Programs::
192 * Running and Debugging Ada Programs::
194 * Code Coverage and Profiling::
197 * Compatibility with HP Ada::
199 * Platform-Specific Information for the Run-Time Libraries::
200 * Example of Binder Output File::
201 * Elaboration Order Handling in GNAT::
202 * Conditional Compilation::
204 * Compatibility and Porting Guide::
206 * Microsoft Windows Topics::
208 * GNU Free Documentation License::
211 --- The Detailed Node Listing ---
215 * What This Guide Contains::
216 * What You Should Know before Reading This Guide::
217 * Related Information::
220 Getting Started with GNAT
223 * Running a Simple Ada Program::
224 * Running a Program with Multiple Units::
225 * Using the gnatmake Utility::
227 * Editing with Emacs::
230 * Introduction to GPS::
233 The GNAT Compilation Model
235 * Source Representation::
236 * Foreign Language Representation::
237 * File Naming Rules::
238 * Using Other File Names::
239 * Alternative File Naming Schemes::
240 * Generating Object Files::
241 * Source Dependencies::
242 * The Ada Library Information Files::
243 * Binding an Ada Program::
244 * Mixed Language Programming::
246 * Building Mixed Ada & C++ Programs::
247 * Comparison between GNAT and C/C++ Compilation Models::
249 * Comparison between GNAT and Conventional Ada Library Models::
251 * Placement of temporary files::
254 Foreign Language Representation
257 * Other 8-Bit Codes::
258 * Wide Character Encodings::
260 Compiling Ada Programs With gcc
262 * Compiling Programs::
264 * Search Paths and the Run-Time Library (RTL)::
265 * Order of Compilation Issues::
270 * Output and Error Message Control::
271 * Warning Message Control::
272 * Debugging and Assertion Control::
273 * Validity Checking::
276 * Using gcc for Syntax Checking::
277 * Using gcc for Semantic Checking::
278 * Compiling Different Versions of Ada::
279 * Character Set Control::
280 * File Naming Control::
281 * Subprogram Inlining Control::
282 * Auxiliary Output Control::
283 * Debugging Control::
284 * Exception Handling Control::
285 * Units to Sources Mapping Files::
286 * Integrated Preprocessing::
291 Binding Ada Programs With gnatbind
294 * Switches for gnatbind::
295 * Command-Line Access::
296 * Search Paths for gnatbind::
297 * Examples of gnatbind Usage::
299 Switches for gnatbind
301 * Consistency-Checking Modes::
302 * Binder Error Message Control::
303 * Elaboration Control::
305 * Binding with Non-Ada Main Programs::
306 * Binding Programs with No Main Subprogram::
308 Linking Using gnatlink
311 * Switches for gnatlink::
313 The GNAT Make Program gnatmake
316 * Switches for gnatmake::
317 * Mode Switches for gnatmake::
318 * Notes on the Command Line::
319 * How gnatmake Works::
320 * Examples of gnatmake Usage::
322 Improving Performance
323 * Performance Considerations::
324 * Text_IO Suggestions::
325 * Reducing Size of Ada Executables with gnatelim::
326 * Reducing Size of Executables with unused subprogram/data elimination::
328 Performance Considerations
329 * Controlling Run-Time Checks::
330 * Use of Restrictions::
331 * Optimization Levels::
332 * Debugging Optimized Code::
333 * Inlining of Subprograms::
334 * Other Optimization Switches::
335 * Optimization and Strict Aliasing::
337 * Coverage Analysis::
340 Reducing Size of Ada Executables with gnatelim
343 * Correcting the List of Eliminate Pragmas::
344 * Making Your Executables Smaller::
345 * Summary of the gnatelim Usage Cycle::
347 Reducing Size of Executables with unused subprogram/data elimination
348 * About unused subprogram/data elimination::
349 * Compilation options::
351 Renaming Files Using gnatchop
353 * Handling Files with Multiple Units::
354 * Operating gnatchop in Compilation Mode::
355 * Command Line for gnatchop::
356 * Switches for gnatchop::
357 * Examples of gnatchop Usage::
359 Configuration Pragmas
361 * Handling of Configuration Pragmas::
362 * The Configuration Pragmas Files::
364 Handling Arbitrary File Naming Conventions Using gnatname
366 * Arbitrary File Naming Conventions::
368 * Switches for gnatname::
369 * Examples of gnatname Usage::
374 * Examples of Project Files::
375 * Project File Syntax::
376 * Objects and Sources in Project Files::
377 * Importing Projects::
378 * Project Extension::
379 * Project Hierarchy Extension::
380 * External References in Project Files::
381 * Packages in Project Files::
382 * Variables from Imported Projects::
385 * Stand-alone Library Projects::
386 * Switches Related to Project Files::
387 * Tools Supporting Project Files::
388 * An Extended Example::
389 * Project File Complete Syntax::
391 The Cross-Referencing Tools gnatxref and gnatfind
393 * 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++ constructors::
2980 * Interfacing with C++ at the Class Level::
2983 @node Interfacing to C++
2984 @subsection Interfacing to C++
2987 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2988 generating code that is compatible with the G++ Application Binary
2989 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2992 Interfacing can be done at 3 levels: simple data, subprograms, and
2993 classes. In the first two cases, GNAT offers a specific @code{Convention
2994 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2995 Usually, C++ mangles the names of subprograms. To generate proper mangled
2996 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2997 This problem can also be addressed manually in two ways:
3001 by modifying the C++ code in order to force a C convention using
3002 the @code{extern "C"} syntax.
3005 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
3006 Link_Name argument of the pragma import.
3010 Interfacing at the class level can be achieved by using the GNAT specific
3011 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3012 gnat_rm, GNAT Reference Manual}, for additional information.
3014 @node Linking a Mixed C++ & Ada Program
3015 @subsection Linking a Mixed C++ & Ada Program
3018 Usually the linker of the C++ development system must be used to link
3019 mixed applications because most C++ systems will resolve elaboration
3020 issues (such as calling constructors on global class instances)
3021 transparently during the link phase. GNAT has been adapted to ease the
3022 use of a foreign linker for the last phase. Three cases can be
3027 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3028 The C++ linker can simply be called by using the C++ specific driver
3031 Note that if the C++ code uses inline functions, you will need to
3032 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3033 order to provide an existing function implementation that the Ada code can
3037 $ g++ -c -fkeep-inline-functions file1.C
3038 $ g++ -c -fkeep-inline-functions file2.C
3039 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3043 Using GNAT and G++ from two different GCC installations: If both
3044 compilers are on the @env{PATH}, the previous method may be used. It is
3045 important to note that environment variables such as
3046 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3047 @env{GCC_ROOT} will affect both compilers
3048 at the same time and may make one of the two compilers operate
3049 improperly if set during invocation of the wrong compiler. It is also
3050 very important that the linker uses the proper @file{libgcc.a} GCC
3051 library -- that is, the one from the C++ compiler installation. The
3052 implicit link command as suggested in the @command{gnatmake} command
3053 from the former example can be replaced by an explicit link command with
3054 the full-verbosity option in order to verify which library is used:
3057 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3059 If there is a problem due to interfering environment variables, it can
3060 be worked around by using an intermediate script. The following example
3061 shows the proper script to use when GNAT has not been installed at its
3062 default location and g++ has been installed at its default location:
3070 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3074 Using a non-GNU C++ compiler: The commands previously described can be
3075 used to insure that the C++ linker is used. Nonetheless, you need to add
3076 a few more parameters to the link command line, depending on the exception
3079 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3080 to the libgcc libraries are required:
3085 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3086 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3089 Where CC is the name of the non-GNU C++ compiler.
3091 If the @code{zero cost} exception mechanism is used, and the platform
3092 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3093 paths to more objects are required:
3098 CC `gcc -print-file-name=crtbegin.o` $* \
3099 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3100 `gcc -print-file-name=crtend.o`
3101 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3104 If the @code{zero cost} exception mechanism is used, and the platform
3105 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3106 Tru64 or AIX), the simple approach described above will not work and
3107 a pre-linking phase using GNAT will be necessary.
3111 Another alternative is to use the @command{gprbuild} multi-language builder
3112 which has a large knowledge base and knows how to link Ada and C++ code
3113 together automatically in most cases.
3115 @node A Simple Example
3116 @subsection A Simple Example
3118 The following example, provided as part of the GNAT examples, shows how
3119 to achieve procedural interfacing between Ada and C++ in both
3120 directions. The C++ class A has two methods. The first method is exported
3121 to Ada by the means of an extern C wrapper function. The second method
3122 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3123 a limited record with a layout comparable to the C++ class. The Ada
3124 subprogram, in turn, calls the C++ method. So, starting from the C++
3125 main program, the process passes back and forth between the two
3129 Here are the compilation commands:
3131 $ gnatmake -c simple_cpp_interface
3134 $ gnatbind -n simple_cpp_interface
3135 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3136 -lstdc++ ex7.o cpp_main.o
3140 Here are the corresponding sources:
3148 void adainit (void);
3149 void adafinal (void);
3150 void method1 (A *t);
3172 class A : public Origin @{
3174 void method1 (void);
3175 void method2 (int v);
3185 extern "C" @{ void ada_method2 (A *t, int v);@}
3187 void A::method1 (void)
3190 printf ("in A::method1, a_value = %d \n",a_value);
3194 void A::method2 (int v)
3196 ada_method2 (this, v);
3197 printf ("in A::method2, a_value = %d \n",a_value);
3204 printf ("in A::A, a_value = %d \n",a_value);
3208 @smallexample @c ada
3210 package body Simple_Cpp_Interface is
3212 procedure Ada_Method2 (This : in out A; V : Integer) is
3218 end Simple_Cpp_Interface;
3221 package Simple_Cpp_Interface is
3224 Vptr : System.Address;
3228 pragma Convention (C, A);
3230 procedure Method1 (This : in out A);
3231 pragma Import (C, Method1);
3233 procedure Ada_Method2 (This : in out A; V : Integer);
3234 pragma Export (C, Ada_Method2);
3236 end Simple_Cpp_Interface;
3239 @node Interfacing with C++ constructors
3240 @subsection Interfacing with C++ constructors
3243 In order to interface with C++ constructors GNAT provides the
3244 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3245 gnat_rm, GNAT Reference Manual}, for additional information).
3246 In this section we present some common uses of C++ constructors
3247 in mixed-languages programs in GNAT.
3249 Let us assume that we need to interface with the following
3257 @b{virtual} int Get_Value ();
3258 Root(); // Default constructor
3259 Root(int v); // 1st non-default constructor
3260 Root(int v, int w); // 2nd non-default constructor
3264 For this purpose we can write the following package spec (further
3265 information on how to build this spec is available in
3266 @ref{Interfacing with C++ at the Class Level} and
3267 @ref{Generating Ada Bindings for C and C++ headers}).
3269 @smallexample @c ada
3270 with Interfaces.C; use Interfaces.C;
3272 type Root is tagged limited record
3276 pragma Import (CPP, Root);
3278 function Get_Value (Obj : Root) return int;
3279 pragma Import (CPP, Get_Value);
3281 function Constructor return Root;
3282 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3284 function Constructor (v : Integer) return Root;
3285 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3287 function Constructor (v, w : Integer) return Root;
3288 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3292 On the Ada side the constructor is represented by a function (whose
3293 name is arbitrary) that returns the classwide type corresponding to
3294 the imported C++ class. Although the constructor is described as a
3295 function, it is typically a procedure with an extra implicit argument
3296 (the object being initialized) at the implementation level. GNAT
3297 issues the appropriate call, whatever it is, to get the object
3298 properly initialized.
3300 Constructors can only appear in the following contexts:
3304 On the right side of an initialization of an object of type @var{T}.
3306 On the right side of an initialization of a record component of type @var{T}.
3308 In an Ada 2005 limited aggregate.
3310 In an Ada 2005 nested limited aggregate.
3312 In an Ada 2005 limited aggregate that initializes an object built in
3313 place by an extended return statement.
3317 In a declaration of an object whose type is a class imported from C++,
3318 either the default C++ constructor is implicitly called by GNAT, or
3319 else the required C++ constructor must be explicitly called in the
3320 expression that initializes the object. For example:
3322 @smallexample @c ada
3324 Obj2 : Root := Constructor;
3325 Obj3 : Root := Constructor (v => 10);
3326 Obj4 : Root := Constructor (30, 40);
3329 The first two declarations are equivalent: in both cases the default C++
3330 constructor is invoked (in the former case the call to the constructor is
3331 implicit, and in the latter case the call is explicit in the object
3332 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3333 that takes an integer argument, and @code{Obj4} is initialized by the
3334 non-default C++ constructor that takes two integers.
3336 Let us derive the imported C++ class in the Ada side. For example:
3338 @smallexample @c ada
3339 type DT is new Root with record
3340 C_Value : Natural := 2009;
3344 In this case the components DT inherited from the C++ side must be
3345 initialized by a C++ constructor, and the additional Ada components
3346 of type DT are initialized by GNAT. The initialization of such an
3347 object is done either by default, or by means of a function returning
3348 an aggregate of type DT, or by means of an extension aggregate.
3350 @smallexample @c ada
3352 Obj6 : DT := Function_Returning_DT (50);
3353 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3356 The declaration of @code{Obj5} invokes the default constructors: the
3357 C++ default constructor of the parent type takes care of the initialization
3358 of the components inherited from Root, and GNAT takes care of the default
3359 initialization of the additional Ada components of type DT (that is,
3360 @code{C_Value} is initialized to value 2009). The order of invocation of
3361 the constructors is consistent with the order of elaboration required by
3362 Ada and C++. That is, the constructor of the parent type is always called
3363 before the constructor of the derived type.
3365 Let us now consider a record that has components whose type is imported
3366 from C++. For example:
3368 @smallexample @c ada
3369 type Rec1 is limited record
3370 Data1 : Root := Constructor (10);
3371 Value : Natural := 1000;
3374 type Rec2 (D : Integer := 20) is limited record
3376 Data2 : Root := Constructor (D, 30);
3380 The initialization of an object of type @code{Rec2} will call the
3381 non-default C++ constructors specified for the imported components.
3384 @smallexample @c ada
3388 Using Ada 2005 we can use limited aggregates to initialize an object
3389 invoking C++ constructors that differ from those specified in the type
3390 declarations. For example:
3392 @smallexample @c ada
3393 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3398 The above declaration uses an Ada 2005 limited aggregate to
3399 initialize @code{Obj9}, and the C++ constructor that has two integer
3400 arguments is invoked to initialize the @code{Data1} component instead
3401 of the constructor specified in the declaration of type @code{Rec1}. In
3402 Ada 2005 the box in the aggregate indicates that unspecified components
3403 are initialized using the expression (if any) available in the component
3404 declaration. That is, in this case discriminant @code{D} is initialized
3405 to value @code{20}, @code{Value} is initialized to value 1000, and the
3406 non-default C++ constructor that handles two integers takes care of
3407 initializing component @code{Data2} with values @code{20,30}.
3409 In Ada 2005 we can use the extended return statement to build the Ada
3410 equivalent to C++ non-default constructors. For example:
3412 @smallexample @c ada
3413 function Constructor (V : Integer) return Rec2 is
3415 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3418 -- Further actions required for construction of
3419 -- objects of type Rec2
3425 In this example the extended return statement construct is used to
3426 build in place the returned object whose components are initialized
3427 by means of a limited aggregate. Any further action associated with
3428 the constructor can be placed inside the construct.
3430 @node Interfacing with C++ at the Class Level
3431 @subsection Interfacing with C++ at the Class Level
3433 In this section we demonstrate the GNAT features for interfacing with
3434 C++ by means of an example making use of Ada 2005 abstract interface
3435 types. This example consists of a classification of animals; classes
3436 have been used to model our main classification of animals, and
3437 interfaces provide support for the management of secondary
3438 classifications. We first demonstrate a case in which the types and
3439 constructors are defined on the C++ side and imported from the Ada
3440 side, and latter the reverse case.
3442 The root of our derivation will be the @code{Animal} class, with a
3443 single private attribute (the @code{Age} of the animal) and two public
3444 primitives to set and get the value of this attribute.
3449 @b{virtual} void Set_Age (int New_Age);
3450 @b{virtual} int Age ();
3456 Abstract interface types are defined in C++ by means of classes with pure
3457 virtual functions and no data members. In our example we will use two
3458 interfaces that provide support for the common management of @code{Carnivore}
3459 and @code{Domestic} animals:
3462 @b{class} Carnivore @{
3464 @b{virtual} int Number_Of_Teeth () = 0;
3467 @b{class} Domestic @{
3469 @b{virtual void} Set_Owner (char* Name) = 0;
3473 Using these declarations, we can now say that a @code{Dog} is an animal that is
3474 both Carnivore and Domestic, that is:
3477 @b{class} Dog : Animal, Carnivore, Domestic @{
3479 @b{virtual} int Number_Of_Teeth ();
3480 @b{virtual} void Set_Owner (char* Name);
3482 Dog(); // Constructor
3489 In the following examples we will assume that the previous declarations are
3490 located in a file named @code{animals.h}. The following package demonstrates
3491 how to import these C++ declarations from the Ada side:
3493 @smallexample @c ada
3494 with Interfaces.C.Strings; use Interfaces.C.Strings;
3496 type Carnivore is interface;
3497 pragma Convention (C_Plus_Plus, Carnivore);
3498 function Number_Of_Teeth (X : Carnivore)
3499 return Natural is abstract;
3501 type Domestic is interface;
3502 pragma Convention (C_Plus_Plus, Set_Owner);
3504 (X : in out Domestic;
3505 Name : Chars_Ptr) is abstract;
3507 type Animal is tagged record
3510 pragma Import (C_Plus_Plus, Animal);
3512 procedure Set_Age (X : in out Animal; Age : Integer);
3513 pragma Import (C_Plus_Plus, Set_Age);
3515 function Age (X : Animal) return Integer;
3516 pragma Import (C_Plus_Plus, Age);
3518 type Dog is new Animal and Carnivore and Domestic with record
3519 Tooth_Count : Natural;
3520 Owner : String (1 .. 30);
3522 pragma Import (C_Plus_Plus, Dog);
3524 function Number_Of_Teeth (A : Dog) return Integer;
3525 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3527 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3528 pragma Import (C_Plus_Plus, Set_Owner);
3530 function New_Dog return Dog;
3531 pragma CPP_Constructor (New_Dog);
3532 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3536 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3537 interfacing with these C++ classes is easy. The only requirement is that all
3538 the primitives and components must be declared exactly in the same order in
3541 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3542 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3543 the arguments to the called primitives will be the same as for C++. For the
3544 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3545 to indicate that they have been defined on the C++ side; this is required
3546 because the dispatch table associated with these tagged types will be built
3547 in the C++ side and therefore will not contain the predefined Ada primitives
3548 which Ada would otherwise expect.
3550 As the reader can see there is no need to indicate the C++ mangled names
3551 associated with each subprogram because it is assumed that all the calls to
3552 these primitives will be dispatching calls. The only exception is the
3553 constructor, which must be registered with the compiler by means of
3554 @code{pragma CPP_Constructor} and needs to provide its associated C++
3555 mangled name because the Ada compiler generates direct calls to it.
3557 With the above packages we can now declare objects of type Dog on the Ada side
3558 and dispatch calls to the corresponding subprograms on the C++ side. We can
3559 also extend the tagged type Dog with further fields and primitives, and
3560 override some of its C++ primitives on the Ada side. For example, here we have
3561 a type derivation defined on the Ada side that inherits all the dispatching
3562 primitives of the ancestor from the C++ side.
3565 @b{with} Animals; @b{use} Animals;
3566 @b{package} Vaccinated_Animals @b{is}
3567 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3568 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3569 @b{end} Vaccinated_Animals;
3572 It is important to note that, because of the ABI compatibility, the programmer
3573 does not need to add any further information to indicate either the object
3574 layout or the dispatch table entry associated with each dispatching operation.
3576 Now let us define all the types and constructors on the Ada side and export
3577 them to C++, using the same hierarchy of our previous example:
3579 @smallexample @c ada
3580 with Interfaces.C.Strings;
3581 use Interfaces.C.Strings;
3583 type Carnivore is interface;
3584 pragma Convention (C_Plus_Plus, Carnivore);
3585 function Number_Of_Teeth (X : Carnivore)
3586 return Natural is abstract;
3588 type Domestic is interface;
3589 pragma Convention (C_Plus_Plus, Set_Owner);
3591 (X : in out Domestic;
3592 Name : Chars_Ptr) is abstract;
3594 type Animal is tagged record
3597 pragma Convention (C_Plus_Plus, Animal);
3599 procedure Set_Age (X : in out Animal; Age : Integer);
3600 pragma Export (C_Plus_Plus, Set_Age);
3602 function Age (X : Animal) return Integer;
3603 pragma Export (C_Plus_Plus, Age);
3605 type Dog is new Animal and Carnivore and Domestic with record
3606 Tooth_Count : Natural;
3607 Owner : String (1 .. 30);
3609 pragma Convention (C_Plus_Plus, Dog);
3611 function Number_Of_Teeth (A : Dog) return Integer;
3612 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3614 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3615 pragma Export (C_Plus_Plus, Set_Owner);
3617 function New_Dog return Dog'Class;
3618 pragma Export (C_Plus_Plus, New_Dog);
3622 Compared with our previous example the only difference is the use of
3623 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3624 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3625 nothing else to be done; as explained above, the only requirement is that all
3626 the primitives and components are declared in exactly the same order.
3628 For completeness, let us see a brief C++ main program that uses the
3629 declarations available in @code{animals.h} (presented in our first example) to
3630 import and use the declarations from the Ada side, properly initializing and
3631 finalizing the Ada run-time system along the way:
3634 @b{#include} "animals.h"
3635 @b{#include} <iostream>
3636 @b{using namespace} std;
3638 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3639 void Check_Domestic (Domestic *obj) @{@dots{}@}
3640 void Check_Animal (Animal *obj) @{@dots{}@}
3641 void Check_Dog (Dog *obj) @{@dots{}@}
3644 void adainit (void);
3645 void adafinal (void);
3651 Dog *obj = new_dog(); // Ada constructor
3652 Check_Carnivore (obj); // Check secondary DT
3653 Check_Domestic (obj); // Check secondary DT
3654 Check_Animal (obj); // Check primary DT
3655 Check_Dog (obj); // Check primary DT
3660 adainit (); test(); adafinal ();
3665 @node Comparison between GNAT and C/C++ Compilation Models
3666 @section Comparison between GNAT and C/C++ Compilation Models
3669 The GNAT model of compilation is close to the C and C++ models. You can
3670 think of Ada specs as corresponding to header files in C. As in C, you
3671 don't need to compile specs; they are compiled when they are used. The
3672 Ada @code{with} is similar in effect to the @code{#include} of a C
3675 One notable difference is that, in Ada, you may compile specs separately
3676 to check them for semantic and syntactic accuracy. This is not always
3677 possible with C headers because they are fragments of programs that have
3678 less specific syntactic or semantic rules.
3680 The other major difference is the requirement for running the binder,
3681 which performs two important functions. First, it checks for
3682 consistency. In C or C++, the only defense against assembling
3683 inconsistent programs lies outside the compiler, in a makefile, for
3684 example. The binder satisfies the Ada requirement that it be impossible
3685 to construct an inconsistent program when the compiler is used in normal
3688 @cindex Elaboration order control
3689 The other important function of the binder is to deal with elaboration
3690 issues. There are also elaboration issues in C++ that are handled
3691 automatically. This automatic handling has the advantage of being
3692 simpler to use, but the C++ programmer has no control over elaboration.
3693 Where @code{gnatbind} might complain there was no valid order of
3694 elaboration, a C++ compiler would simply construct a program that
3695 malfunctioned at run time.
3698 @node Comparison between GNAT and Conventional Ada Library Models
3699 @section Comparison between GNAT and Conventional Ada Library Models
3702 This section is intended for Ada programmers who have
3703 used an Ada compiler implementing the traditional Ada library
3704 model, as described in the Ada Reference Manual.
3706 @cindex GNAT library
3707 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3708 source files themselves acts as the library. Compiling Ada programs does
3709 not generate any centralized information, but rather an object file and
3710 a ALI file, which are of interest only to the binder and linker.
3711 In a traditional system, the compiler reads information not only from
3712 the source file being compiled, but also from the centralized library.
3713 This means that the effect of a compilation depends on what has been
3714 previously compiled. In particular:
3718 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3719 to the version of the unit most recently compiled into the library.
3722 Inlining is effective only if the necessary body has already been
3723 compiled into the library.
3726 Compiling a unit may obsolete other units in the library.
3730 In GNAT, compiling one unit never affects the compilation of any other
3731 units because the compiler reads only source files. Only changes to source
3732 files can affect the results of a compilation. In particular:
3736 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3737 to the source version of the unit that is currently accessible to the
3742 Inlining requires the appropriate source files for the package or
3743 subprogram bodies to be available to the compiler. Inlining is always
3744 effective, independent of the order in which units are complied.
3747 Compiling a unit never affects any other compilations. The editing of
3748 sources may cause previous compilations to be out of date if they
3749 depended on the source file being modified.
3753 The most important result of these differences is that order of compilation
3754 is never significant in GNAT. There is no situation in which one is
3755 required to do one compilation before another. What shows up as order of
3756 compilation requirements in the traditional Ada library becomes, in
3757 GNAT, simple source dependencies; in other words, there is only a set
3758 of rules saying what source files must be present when a file is
3762 @node Placement of temporary files
3763 @section Placement of temporary files
3764 @cindex Temporary files (user control over placement)
3767 GNAT creates temporary files in the directory designated by the environment
3768 variable @env{TMPDIR}.
3769 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3770 for detailed information on how environment variables are resolved.
3771 For most users the easiest way to make use of this feature is to simply
3772 define @env{TMPDIR} as a job level logical name).
3773 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3774 for compiler temporary files, then you can include something like the
3775 following command in your @file{LOGIN.COM} file:
3778 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3782 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3783 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3784 designated by @env{TEMP}.
3785 If none of these environment variables are defined then GNAT uses the
3786 directory designated by the logical name @code{SYS$SCRATCH:}
3787 (by default the user's home directory). If all else fails
3788 GNAT uses the current directory for temporary files.
3791 @c *************************
3792 @node Compiling Using gcc
3793 @chapter Compiling Using @command{gcc}
3796 This chapter discusses how to compile Ada programs using the @command{gcc}
3797 command. It also describes the set of switches
3798 that can be used to control the behavior of the compiler.
3800 * Compiling Programs::
3801 * Switches for gcc::
3802 * Search Paths and the Run-Time Library (RTL)::
3803 * Order of Compilation Issues::
3807 @node Compiling Programs
3808 @section Compiling Programs
3811 The first step in creating an executable program is to compile the units
3812 of the program using the @command{gcc} command. You must compile the
3817 the body file (@file{.adb}) for a library level subprogram or generic
3821 the spec file (@file{.ads}) for a library level package or generic
3822 package that has no body
3825 the body file (@file{.adb}) for a library level package
3826 or generic package that has a body
3831 You need @emph{not} compile the following files
3836 the spec of a library unit which has a body
3843 because they are compiled as part of compiling related units. GNAT
3845 when the corresponding body is compiled, and subunits when the parent is
3848 @cindex cannot generate code
3849 If you attempt to compile any of these files, you will get one of the
3850 following error messages (where @var{fff} is the name of the file you compiled):
3853 cannot generate code for file @var{fff} (package spec)
3854 to check package spec, use -gnatc
3856 cannot generate code for file @var{fff} (missing subunits)
3857 to check parent unit, use -gnatc
3859 cannot generate code for file @var{fff} (subprogram spec)
3860 to check subprogram spec, use -gnatc
3862 cannot generate code for file @var{fff} (subunit)
3863 to check subunit, use -gnatc
3867 As indicated by the above error messages, if you want to submit
3868 one of these files to the compiler to check for correct semantics
3869 without generating code, then use the @option{-gnatc} switch.
3871 The basic command for compiling a file containing an Ada unit is
3874 $ gcc -c @ovar{switches} @file{file name}
3878 where @var{file name} is the name of the Ada file (usually
3880 @file{.ads} for a spec or @file{.adb} for a body).
3883 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3885 The result of a successful compilation is an object file, which has the
3886 same name as the source file but an extension of @file{.o} and an Ada
3887 Library Information (ALI) file, which also has the same name as the
3888 source file, but with @file{.ali} as the extension. GNAT creates these
3889 two output files in the current directory, but you may specify a source
3890 file in any directory using an absolute or relative path specification
3891 containing the directory information.
3894 @command{gcc} is actually a driver program that looks at the extensions of
3895 the file arguments and loads the appropriate compiler. For example, the
3896 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3897 These programs are in directories known to the driver program (in some
3898 configurations via environment variables you set), but need not be in
3899 your path. The @command{gcc} driver also calls the assembler and any other
3900 utilities needed to complete the generation of the required object
3903 It is possible to supply several file names on the same @command{gcc}
3904 command. This causes @command{gcc} to call the appropriate compiler for
3905 each file. For example, the following command lists three separate
3906 files to be compiled:
3909 $ gcc -c x.adb y.adb z.c
3913 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3914 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3915 The compiler generates three object files @file{x.o}, @file{y.o} and
3916 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3917 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3920 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3923 @node Switches for gcc
3924 @section Switches for @command{gcc}
3927 The @command{gcc} command accepts switches that control the
3928 compilation process. These switches are fully described in this section.
3929 First we briefly list all the switches, in alphabetical order, then we
3930 describe the switches in more detail in functionally grouped sections.
3932 More switches exist for GCC than those documented here, especially
3933 for specific targets. However, their use is not recommended as
3934 they may change code generation in ways that are incompatible with
3935 the Ada run-time library, or can cause inconsistencies between
3939 * Output and Error Message Control::
3940 * Warning Message Control::
3941 * Debugging and Assertion Control::
3942 * Validity Checking::
3945 * Using gcc for Syntax Checking::
3946 * Using gcc for Semantic Checking::
3947 * Compiling Different Versions of Ada::
3948 * Character Set Control::
3949 * File Naming Control::
3950 * Subprogram Inlining Control::
3951 * Auxiliary Output Control::
3952 * Debugging Control::
3953 * Exception Handling Control::
3954 * Units to Sources Mapping Files::
3955 * Integrated Preprocessing::
3956 * Code Generation Control::
3965 @cindex @option{-b} (@command{gcc})
3966 @item -b @var{target}
3967 Compile your program to run on @var{target}, which is the name of a
3968 system configuration. You must have a GNAT cross-compiler built if
3969 @var{target} is not the same as your host system.
3972 @cindex @option{-B} (@command{gcc})
3973 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3974 from @var{dir} instead of the default location. Only use this switch
3975 when multiple versions of the GNAT compiler are available.
3976 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3977 GNU Compiler Collection (GCC)}, for further details. You would normally
3978 use the @option{-b} or @option{-V} switch instead.
3981 @cindex @option{-c} (@command{gcc})
3982 Compile. Always use this switch when compiling Ada programs.
3984 Note: for some other languages when using @command{gcc}, notably in
3985 the case of C and C++, it is possible to use
3986 use @command{gcc} without a @option{-c} switch to
3987 compile and link in one step. In the case of GNAT, you
3988 cannot use this approach, because the binder must be run
3989 and @command{gcc} cannot be used to run the GNAT binder.
3993 @cindex @option{-fno-inline} (@command{gcc})
3994 Suppresses all back-end inlining, even if other optimization or inlining
3996 This includes suppression of inlining that results
3997 from the use of the pragma @code{Inline_Always}.
3998 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3999 are ignored, and @option{-gnatn} and @option{-gnatN} have no
4000 effect if this switch is present.
4002 @item -fno-inline-functions
4003 @cindex @option{-fno-inline-functions} (@command{gcc})
4004 Suppresses automatic inlining of simple subprograms, which is enabled
4005 if @option{-O3} is used.
4007 @item -fno-inline-small-functions
4008 @cindex @option{-fno-inline-small-functions} (@command{gcc})
4009 Suppresses automatic inlining of small subprograms, which is enabled
4010 if @option{-O2} is used.
4012 @item -fno-inline-functions-called-once
4013 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
4014 Suppresses inlining of subprograms local to the unit and called once
4015 from within it, which is enabled if @option{-O1} is used.
4018 @cindex @option{-fno-ivopts} (@command{gcc})
4019 Suppresses high-level loop induction variable optimizations, which are
4020 enabled if @option{-O1} is used. These optimizations are generally
4021 profitable but, for some specific cases of loops with numerous uses
4022 of the iteration variable that follow a common pattern, they may end
4023 up destroying the regularity that could be exploited at a lower level
4024 and thus producing inferior code.
4026 @item -fno-strict-aliasing
4027 @cindex @option{-fno-strict-aliasing} (@command{gcc})
4028 Causes the compiler to avoid assumptions regarding non-aliasing
4029 of objects of different types. See
4030 @ref{Optimization and Strict Aliasing} for details.
4033 @cindex @option{-fstack-check} (@command{gcc})
4034 Activates stack checking.
4035 See @ref{Stack Overflow Checking} for details.
4038 @cindex @option{-fstack-usage} (@command{gcc})
4039 Makes the compiler output stack usage information for the program, on a
4040 per-function basis. See @ref{Static Stack Usage Analysis} for details.
4042 @item -fcallgraph-info@r{[}=su@r{]}
4043 @cindex @option{-fcallgraph-info} (@command{gcc})
4044 Makes the compiler output callgraph information for the program, on a
4045 per-file basis. The information is generated in the VCG format. It can
4046 be decorated with stack-usage per-node information.
4049 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4050 Generate debugging information. This information is stored in the object
4051 file and copied from there to the final executable file by the linker,
4052 where it can be read by the debugger. You must use the
4053 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4056 @cindex @option{-gnat83} (@command{gcc})
4057 Enforce Ada 83 restrictions.
4060 @cindex @option{-gnat95} (@command{gcc})
4061 Enforce Ada 95 restrictions.
4064 @cindex @option{-gnat05} (@command{gcc})
4065 Allow full Ada 2005 features.
4068 @cindex @option{-gnata} (@command{gcc})
4069 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4070 activated. Note that these pragmas can also be controlled using the
4071 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4072 It also activates pragmas @code{Check}, @code{Precondition}, and
4073 @code{Postcondition}. Note that these pragmas can also be controlled
4074 using the configuration pragma @code{Check_Policy}.
4077 @cindex @option{-gnatA} (@command{gcc})
4078 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4082 @cindex @option{-gnatb} (@command{gcc})
4083 Generate brief messages to @file{stderr} even if verbose mode set.
4086 @cindex @option{-gnatB} (@command{gcc})
4087 Assume no invalid (bad) values except for 'Valid attribute use.
4090 @cindex @option{-gnatc} (@command{gcc})
4091 Check syntax and semantics only (no code generation attempted).
4094 @cindex @option{-gnatd} (@command{gcc})
4095 Specify debug options for the compiler. The string of characters after
4096 the @option{-gnatd} specify the specific debug options. The possible
4097 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4098 compiler source file @file{debug.adb} for details of the implemented
4099 debug options. Certain debug options are relevant to applications
4100 programmers, and these are documented at appropriate points in this
4105 @cindex @option{-gnatD[nn]} (@command{gcc})
4108 @item /XDEBUG /LXDEBUG=nnn
4110 Create expanded source files for source level debugging. This switch
4111 also suppress generation of cross-reference information
4112 (see @option{-gnatx}).
4114 @item -gnatec=@var{path}
4115 @cindex @option{-gnatec} (@command{gcc})
4116 Specify a configuration pragma file
4118 (the equal sign is optional)
4120 (@pxref{The Configuration Pragmas Files}).
4122 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4123 @cindex @option{-gnateD} (@command{gcc})
4124 Defines a symbol, associated with @var{value}, for preprocessing.
4125 (@pxref{Integrated Preprocessing}).
4128 @cindex @option{-gnatef} (@command{gcc})
4129 Display full source path name in brief error messages.
4132 @cindex @option{-gnateG} (@command{gcc})
4133 Save result of preprocessing in a text file.
4135 @item -gnatem=@var{path}
4136 @cindex @option{-gnatem} (@command{gcc})
4137 Specify a mapping file
4139 (the equal sign is optional)
4141 (@pxref{Units to Sources Mapping Files}).
4143 @item -gnatep=@var{file}
4144 @cindex @option{-gnatep} (@command{gcc})
4145 Specify a preprocessing data file
4147 (the equal sign is optional)
4149 (@pxref{Integrated Preprocessing}).
4152 @cindex @option{-gnatE} (@command{gcc})
4153 Full dynamic elaboration checks.
4156 @cindex @option{-gnatf} (@command{gcc})
4157 Full errors. Multiple errors per line, all undefined references, do not
4158 attempt to suppress cascaded errors.
4161 @cindex @option{-gnatF} (@command{gcc})
4162 Externals names are folded to all uppercase.
4164 @item ^-gnatg^/GNAT_INTERNAL^
4165 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4166 Internal GNAT implementation mode. This should not be used for
4167 applications programs, it is intended only for use by the compiler
4168 and its run-time library. For documentation, see the GNAT sources.
4169 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4170 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4171 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4172 so that all standard warnings and all standard style options are turned on.
4173 All warnings and style error messages are treated as errors.
4177 @cindex @option{-gnatG[nn]} (@command{gcc})
4180 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4182 List generated expanded code in source form.
4184 @item ^-gnath^/HELP^
4185 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4186 Output usage information. The output is written to @file{stdout}.
4188 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4189 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4190 Identifier character set
4192 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4194 For details of the possible selections for @var{c},
4195 see @ref{Character Set Control}.
4197 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4198 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4199 Ignore representation clauses. When this switch is used,
4200 representation clauses are treated as comments. This is useful
4201 when initially porting code where you want to ignore rep clause
4202 problems, and also for compiling foreign code (particularly
4203 for use with ASIS). The representation clauses that are ignored
4204 are: enumeration_representation_clause, record_representation_clause,
4205 and attribute_definition_clause for the following attributes:
4206 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4207 Object_Size, Size, Small, Stream_Size, and Value_Size.
4208 Note that this option should be used only for compiling -- the
4209 code is likely to malfunction at run time.
4212 @cindex @option{-gnatjnn} (@command{gcc})
4213 Reformat error messages to fit on nn character lines
4215 @item -gnatk=@var{n}
4216 @cindex @option{-gnatk} (@command{gcc})
4217 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4220 @cindex @option{-gnatl} (@command{gcc})
4221 Output full source listing with embedded error messages.
4224 @cindex @option{-gnatL} (@command{gcc})
4225 Used in conjunction with -gnatG or -gnatD to intersperse original
4226 source lines (as comment lines with line numbers) in the expanded
4229 @item -gnatm=@var{n}
4230 @cindex @option{-gnatm} (@command{gcc})
4231 Limit number of detected error or warning messages to @var{n}
4232 where @var{n} is in the range 1..999999. The default setting if
4233 no switch is given is 9999. If the number of warnings reaches this
4234 limit, then a message is output and further warnings are suppressed,
4235 but the compilation is continued. If the number of error messages
4236 reaches this limit, then a message is output and the compilation
4237 is abandoned. The equal sign here is optional. A value of zero
4238 means that no limit applies.
4241 @cindex @option{-gnatn} (@command{gcc})
4242 Activate inlining for subprograms for which
4243 pragma @code{inline} is specified. This inlining is performed
4244 by the GCC back-end.
4247 @cindex @option{-gnatN} (@command{gcc})
4248 Activate front end inlining for subprograms for which
4249 pragma @code{Inline} is specified. This inlining is performed
4250 by the front end and will be visible in the
4251 @option{-gnatG} output.
4253 When using a gcc-based back end (in practice this means using any version
4254 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4255 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4256 Historically front end inlining was more extensive than the gcc back end
4257 inlining, but that is no longer the case.
4260 @cindex @option{-gnato} (@command{gcc})
4261 Enable numeric overflow checking (which is not normally enabled by
4262 default). Note that division by zero is a separate check that is not
4263 controlled by this switch (division by zero checking is on by default).
4266 @cindex @option{-gnatp} (@command{gcc})
4267 Suppress all checks. See @ref{Run-Time Checks} for details.
4270 @cindex @option{-gnatP} (@command{gcc})
4271 Enable polling. This is required on some systems (notably Windows NT) to
4272 obtain asynchronous abort and asynchronous transfer of control capability.
4273 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4277 @cindex @option{-gnatq} (@command{gcc})
4278 Don't quit. Try semantics, even if parse errors.
4281 @cindex @option{-gnatQ} (@command{gcc})
4282 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4285 @cindex @option{-gnatr} (@command{gcc})
4286 Treat pragma Restrictions as Restriction_Warnings.
4288 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4289 @cindex @option{-gnatR} (@command{gcc})
4290 Output representation information for declared types and objects.
4293 @cindex @option{-gnats} (@command{gcc})
4297 @cindex @option{-gnatS} (@command{gcc})
4298 Print package Standard.
4301 @cindex @option{-gnatt} (@command{gcc})
4302 Generate tree output file.
4304 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4305 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4306 All compiler tables start at @var{nnn} times usual starting size.
4309 @cindex @option{-gnatu} (@command{gcc})
4310 List units for this compilation.
4313 @cindex @option{-gnatU} (@command{gcc})
4314 Tag all error messages with the unique string ``error:''
4317 @cindex @option{-gnatv} (@command{gcc})
4318 Verbose mode. Full error output with source lines to @file{stdout}.
4321 @cindex @option{-gnatV} (@command{gcc})
4322 Control level of validity checking. See separate section describing
4325 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4326 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4328 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4329 the exact warnings that
4330 are enabled or disabled (@pxref{Warning Message Control}).
4332 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4333 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4334 Wide character encoding method
4336 (@var{e}=n/h/u/s/e/8).
4339 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4343 @cindex @option{-gnatx} (@command{gcc})
4344 Suppress generation of cross-reference information.
4346 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4347 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4348 Enable built-in style checks (@pxref{Style Checking}).
4350 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4351 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4352 Distribution stub generation and compilation
4354 (@var{m}=r/c for receiver/caller stubs).
4357 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4358 to be generated and compiled).
4361 @item ^-I^/SEARCH=^@var{dir}
4362 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4364 Direct GNAT to search the @var{dir} directory for source files needed by
4365 the current compilation
4366 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4368 @item ^-I-^/NOCURRENT_DIRECTORY^
4369 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4371 Except for the source file named in the command line, do not look for source
4372 files in the directory containing the source file named in the command line
4373 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4377 @cindex @option{-mbig-switch} (@command{gcc})
4378 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4379 This standard gcc switch causes the compiler to use larger offsets in its
4380 jump table representation for @code{case} statements.
4381 This may result in less efficient code, but is sometimes necessary
4382 (for example on HP-UX targets)
4383 @cindex HP-UX and @option{-mbig-switch} option
4384 in order to compile large and/or nested @code{case} statements.
4387 @cindex @option{-o} (@command{gcc})
4388 This switch is used in @command{gcc} to redirect the generated object file
4389 and its associated ALI file. Beware of this switch with GNAT, because it may
4390 cause the object file and ALI file to have different names which in turn
4391 may confuse the binder and the linker.
4395 @cindex @option{-nostdinc} (@command{gcc})
4396 Inhibit the search of the default location for the GNAT Run Time
4397 Library (RTL) source files.
4400 @cindex @option{-nostdlib} (@command{gcc})
4401 Inhibit the search of the default location for the GNAT Run Time
4402 Library (RTL) ALI files.
4406 @cindex @option{-O} (@command{gcc})
4407 @var{n} controls the optimization level.
4411 No optimization, the default setting if no @option{-O} appears
4414 Normal optimization, the default if you specify @option{-O} without
4415 an operand. A good compromise between code quality and compilation
4419 Extensive optimization, may improve execution time, possibly at the cost of
4420 substantially increased compilation time.
4423 Same as @option{-O2}, and also includes inline expansion for small subprograms
4427 Optimize space usage
4431 See also @ref{Optimization Levels}.
4436 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4437 Equivalent to @option{/OPTIMIZE=NONE}.
4438 This is the default behavior in the absence of an @option{/OPTIMIZE}
4441 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4442 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4443 Selects the level of optimization for your program. The supported
4444 keywords are as follows:
4447 Perform most optimizations, including those that
4449 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4450 without keyword options.
4453 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4456 Perform some optimizations, but omit ones that are costly.
4459 Same as @code{SOME}.
4462 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4463 automatic inlining of small subprograms within a unit
4466 Try to unroll loops. This keyword may be specified together with
4467 any keyword above other than @code{NONE}. Loop unrolling
4468 usually, but not always, improves the performance of programs.
4471 Optimize space usage
4475 See also @ref{Optimization Levels}.
4479 @item -pass-exit-codes
4480 @cindex @option{-pass-exit-codes} (@command{gcc})
4481 Catch exit codes from the compiler and use the most meaningful as
4485 @item --RTS=@var{rts-path}
4486 @cindex @option{--RTS} (@command{gcc})
4487 Specifies the default location of the runtime library. Same meaning as the
4488 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4491 @cindex @option{^-S^/ASM^} (@command{gcc})
4492 ^Used in place of @option{-c} to^Used to^
4493 cause the assembler source file to be
4494 generated, using @file{^.s^.S^} as the extension,
4495 instead of the object file.
4496 This may be useful if you need to examine the generated assembly code.
4498 @item ^-fverbose-asm^/VERBOSE_ASM^
4499 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4500 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4501 to cause the generated assembly code file to be annotated with variable
4502 names, making it significantly easier to follow.
4505 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4506 Show commands generated by the @command{gcc} driver. Normally used only for
4507 debugging purposes or if you need to be sure what version of the
4508 compiler you are executing.
4512 @cindex @option{-V} (@command{gcc})
4513 Execute @var{ver} version of the compiler. This is the @command{gcc}
4514 version, not the GNAT version.
4517 @item ^-w^/NO_BACK_END_WARNINGS^
4518 @cindex @option{-w} (@command{gcc})
4519 Turn off warnings generated by the back end of the compiler. Use of
4520 this switch also causes the default for front end warnings to be set
4521 to suppress (as though @option{-gnatws} had appeared at the start of
4527 @c Combining qualifiers does not work on VMS
4528 You may combine a sequence of GNAT switches into a single switch. For
4529 example, the combined switch
4531 @cindex Combining GNAT switches
4537 is equivalent to specifying the following sequence of switches:
4540 -gnato -gnatf -gnati3
4545 The following restrictions apply to the combination of switches
4550 The switch @option{-gnatc} if combined with other switches must come
4551 first in the string.
4554 The switch @option{-gnats} if combined with other switches must come
4555 first in the string.
4559 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4560 may not be combined with any other switches.
4564 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4565 switch), then all further characters in the switch are interpreted
4566 as style modifiers (see description of @option{-gnaty}).
4569 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4570 switch), then all further characters in the switch are interpreted
4571 as debug flags (see description of @option{-gnatd}).
4574 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4575 switch), then all further characters in the switch are interpreted
4576 as warning mode modifiers (see description of @option{-gnatw}).
4579 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4580 switch), then all further characters in the switch are interpreted
4581 as validity checking options (see description of @option{-gnatV}).
4585 @node Output and Error Message Control
4586 @subsection Output and Error Message Control
4590 The standard default format for error messages is called ``brief format''.
4591 Brief format messages are written to @file{stderr} (the standard error
4592 file) and have the following form:
4595 e.adb:3:04: Incorrect spelling of keyword "function"
4596 e.adb:4:20: ";" should be "is"
4600 The first integer after the file name is the line number in the file,
4601 and the second integer is the column number within the line.
4603 @code{GPS} can parse the error messages
4604 and point to the referenced character.
4606 The following switches provide control over the error message
4612 @cindex @option{-gnatv} (@command{gcc})
4615 The v stands for verbose.
4617 The effect of this setting is to write long-format error
4618 messages to @file{stdout} (the standard output file.
4619 The same program compiled with the
4620 @option{-gnatv} switch would generate:
4624 3. funcion X (Q : Integer)
4626 >>> Incorrect spelling of keyword "function"
4629 >>> ";" should be "is"
4634 The vertical bar indicates the location of the error, and the @samp{>>>}
4635 prefix can be used to search for error messages. When this switch is
4636 used the only source lines output are those with errors.
4639 @cindex @option{-gnatl} (@command{gcc})
4641 The @code{l} stands for list.
4643 This switch causes a full listing of
4644 the file to be generated. In the case where a body is
4645 compiled, the corresponding spec is also listed, along
4646 with any subunits. Typical output from compiling a package
4647 body @file{p.adb} might look like:
4649 @smallexample @c ada
4653 1. package body p is
4655 3. procedure a is separate;
4666 2. pragma Elaborate_Body
4690 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4691 standard output is redirected, a brief summary is written to
4692 @file{stderr} (standard error) giving the number of error messages and
4693 warning messages generated.
4695 @item -^gnatl^OUTPUT_FILE^=file
4696 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4697 This has the same effect as @option{-gnatl} except that the output is
4698 written to a file instead of to standard output. If the given name
4699 @file{fname} does not start with a period, then it is the full name
4700 of the file to be written. If @file{fname} is an extension, it is
4701 appended to the name of the file being compiled. For example, if
4702 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4703 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4706 @cindex @option{-gnatU} (@command{gcc})
4707 This switch forces all error messages to be preceded by the unique
4708 string ``error:''. This means that error messages take a few more
4709 characters in space, but allows easy searching for and identification
4713 @cindex @option{-gnatb} (@command{gcc})
4715 The @code{b} stands for brief.
4717 This switch causes GNAT to generate the
4718 brief format error messages to @file{stderr} (the standard error
4719 file) as well as the verbose
4720 format message or full listing (which as usual is written to
4721 @file{stdout} (the standard output file).
4723 @item -gnatm=@var{n}
4724 @cindex @option{-gnatm} (@command{gcc})
4726 The @code{m} stands for maximum.
4728 @var{n} is a decimal integer in the
4729 range of 1 to 999999 and limits the number of error or warning
4730 messages to be generated. For example, using
4731 @option{-gnatm2} might yield
4734 e.adb:3:04: Incorrect spelling of keyword "function"
4735 e.adb:5:35: missing ".."
4736 fatal error: maximum number of errors detected
4737 compilation abandoned
4741 The default setting if
4742 no switch is given is 9999. If the number of warnings reaches this
4743 limit, then a message is output and further warnings are suppressed,
4744 but the compilation is continued. If the number of error messages
4745 reaches this limit, then a message is output and the compilation
4746 is abandoned. A value of zero means that no limit applies.
4749 Note that the equal sign is optional, so the switches
4750 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4753 @cindex @option{-gnatf} (@command{gcc})
4754 @cindex Error messages, suppressing
4756 The @code{f} stands for full.
4758 Normally, the compiler suppresses error messages that are likely to be
4759 redundant. This switch causes all error
4760 messages to be generated. In particular, in the case of
4761 references to undefined variables. If a given variable is referenced
4762 several times, the normal format of messages is
4764 e.adb:7:07: "V" is undefined (more references follow)
4768 where the parenthetical comment warns that there are additional
4769 references to the variable @code{V}. Compiling the same program with the
4770 @option{-gnatf} switch yields
4773 e.adb:7:07: "V" is undefined
4774 e.adb:8:07: "V" is undefined
4775 e.adb:8:12: "V" is undefined
4776 e.adb:8:16: "V" is undefined
4777 e.adb:9:07: "V" is undefined
4778 e.adb:9:12: "V" is undefined
4782 The @option{-gnatf} switch also generates additional information for
4783 some error messages. Some examples are:
4787 Details on possibly non-portable unchecked conversion
4789 List possible interpretations for ambiguous calls
4791 Additional details on incorrect parameters
4795 @cindex @option{-gnatjnn} (@command{gcc})
4796 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4797 with continuation lines are treated as though the continuation lines were
4798 separate messages (and so a warning with two continuation lines counts as
4799 three warnings, and is listed as three separate messages).
4801 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4802 messages are output in a different manner. A message and all its continuation
4803 lines are treated as a unit, and count as only one warning or message in the
4804 statistics totals. Furthermore, the message is reformatted so that no line
4805 is longer than nn characters.
4808 @cindex @option{-gnatq} (@command{gcc})
4810 The @code{q} stands for quit (really ``don't quit'').
4812 In normal operation mode, the compiler first parses the program and
4813 determines if there are any syntax errors. If there are, appropriate
4814 error messages are generated and compilation is immediately terminated.
4816 GNAT to continue with semantic analysis even if syntax errors have been
4817 found. This may enable the detection of more errors in a single run. On
4818 the other hand, the semantic analyzer is more likely to encounter some
4819 internal fatal error when given a syntactically invalid tree.
4822 @cindex @option{-gnatQ} (@command{gcc})
4823 In normal operation mode, the @file{ALI} file is not generated if any
4824 illegalities are detected in the program. The use of @option{-gnatQ} forces
4825 generation of the @file{ALI} file. This file is marked as being in
4826 error, so it cannot be used for binding purposes, but it does contain
4827 reasonably complete cross-reference information, and thus may be useful
4828 for use by tools (e.g., semantic browsing tools or integrated development
4829 environments) that are driven from the @file{ALI} file. This switch
4830 implies @option{-gnatq}, since the semantic phase must be run to get a
4831 meaningful ALI file.
4833 In addition, if @option{-gnatt} is also specified, then the tree file is
4834 generated even if there are illegalities. It may be useful in this case
4835 to also specify @option{-gnatq} to ensure that full semantic processing
4836 occurs. The resulting tree file can be processed by ASIS, for the purpose
4837 of providing partial information about illegal units, but if the error
4838 causes the tree to be badly malformed, then ASIS may crash during the
4841 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4842 being in error, @command{gnatmake} will attempt to recompile the source when it
4843 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4845 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4846 since ALI files are never generated if @option{-gnats} is set.
4850 @node Warning Message Control
4851 @subsection Warning Message Control
4852 @cindex Warning messages
4854 In addition to error messages, which correspond to illegalities as defined
4855 in the Ada Reference Manual, the compiler detects two kinds of warning
4858 First, the compiler considers some constructs suspicious and generates a
4859 warning message to alert you to a possible error. Second, if the
4860 compiler detects a situation that is sure to raise an exception at
4861 run time, it generates a warning message. The following shows an example
4862 of warning messages:
4864 e.adb:4:24: warning: creation of object may raise Storage_Error
4865 e.adb:10:17: warning: static value out of range
4866 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4870 GNAT considers a large number of situations as appropriate
4871 for the generation of warning messages. As always, warnings are not
4872 definite indications of errors. For example, if you do an out-of-range
4873 assignment with the deliberate intention of raising a
4874 @code{Constraint_Error} exception, then the warning that may be
4875 issued does not indicate an error. Some of the situations for which GNAT
4876 issues warnings (at least some of the time) are given in the following
4877 list. This list is not complete, and new warnings are often added to
4878 subsequent versions of GNAT. The list is intended to give a general idea
4879 of the kinds of warnings that are generated.
4883 Possible infinitely recursive calls
4886 Out-of-range values being assigned
4889 Possible order of elaboration problems
4892 Assertions (pragma Assert) that are sure to fail
4898 Address clauses with possibly unaligned values, or where an attempt is
4899 made to overlay a smaller variable with a larger one.
4902 Fixed-point type declarations with a null range
4905 Direct_IO or Sequential_IO instantiated with a type that has access values
4908 Variables that are never assigned a value
4911 Variables that are referenced before being initialized
4914 Task entries with no corresponding @code{accept} statement
4917 Duplicate accepts for the same task entry in a @code{select}
4920 Objects that take too much storage
4923 Unchecked conversion between types of differing sizes
4926 Missing @code{return} statement along some execution path in a function
4929 Incorrect (unrecognized) pragmas
4932 Incorrect external names
4935 Allocation from empty storage pool
4938 Potentially blocking operation in protected type
4941 Suspicious parenthesization of expressions
4944 Mismatching bounds in an aggregate
4947 Attempt to return local value by reference
4950 Premature instantiation of a generic body
4953 Attempt to pack aliased components
4956 Out of bounds array subscripts
4959 Wrong length on string assignment
4962 Violations of style rules if style checking is enabled
4965 Unused @code{with} clauses
4968 @code{Bit_Order} usage that does not have any effect
4971 @code{Standard.Duration} used to resolve universal fixed expression
4974 Dereference of possibly null value
4977 Declaration that is likely to cause storage error
4980 Internal GNAT unit @code{with}'ed by application unit
4983 Values known to be out of range at compile time
4986 Unreferenced labels and variables
4989 Address overlays that could clobber memory
4992 Unexpected initialization when address clause present
4995 Bad alignment for address clause
4998 Useless type conversions
5001 Redundant assignment statements and other redundant constructs
5004 Useless exception handlers
5007 Accidental hiding of name by child unit
5010 Access before elaboration detected at compile time
5013 A range in a @code{for} loop that is known to be null or might be null
5018 The following section lists compiler switches that are available
5019 to control the handling of warning messages. It is also possible
5020 to exercise much finer control over what warnings are issued and
5021 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5022 gnat_rm, GNAT Reference manual}.
5027 @emph{Activate all optional errors.}
5028 @cindex @option{-gnatwa} (@command{gcc})
5029 This switch activates most optional warning messages, see remaining list
5030 in this section for details on optional warning messages that can be
5031 individually controlled. The warnings that are not turned on by this
5033 @option{-gnatwd} (implicit dereferencing),
5034 @option{-gnatwh} (hiding),
5035 @option{-gnatwl} (elaboration warnings),
5036 @option{-gnatw.o} (warn on values set by out parameters ignored)
5037 and @option{-gnatwt} (tracking of deleted conditional code).
5038 All other optional warnings are turned on.
5041 @emph{Suppress all optional errors.}
5042 @cindex @option{-gnatwA} (@command{gcc})
5043 This switch suppresses all optional warning messages, see remaining list
5044 in this section for details on optional warning messages that can be
5045 individually controlled.
5048 @emph{Activate warnings on failing assertions.}
5049 @cindex @option{-gnatw.a} (@command{gcc})
5050 @cindex Assert failures
5051 This switch activates warnings for assertions where the compiler can tell at
5052 compile time that the assertion will fail. Note that this warning is given
5053 even if assertions are disabled. The default is that such warnings are
5057 @emph{Suppress warnings on failing assertions.}
5058 @cindex @option{-gnatw.A} (@command{gcc})
5059 @cindex Assert failures
5060 This switch suppresses warnings for assertions where the compiler can tell at
5061 compile time that the assertion will fail.
5064 @emph{Activate warnings on bad fixed values.}
5065 @cindex @option{-gnatwb} (@command{gcc})
5066 @cindex Bad fixed values
5067 @cindex Fixed-point Small value
5069 This switch activates warnings for static fixed-point expressions whose
5070 value is not an exact multiple of Small. Such values are implementation
5071 dependent, since an implementation is free to choose either of the multiples
5072 that surround the value. GNAT always chooses the closer one, but this is not
5073 required behavior, and it is better to specify a value that is an exact
5074 multiple, ensuring predictable execution. The default is that such warnings
5078 @emph{Suppress warnings on bad fixed values.}
5079 @cindex @option{-gnatwB} (@command{gcc})
5080 This switch suppresses warnings for static fixed-point expressions whose
5081 value is not an exact multiple of Small.
5084 @emph{Activate warnings on biased representation.}
5085 @cindex @option{-gnatw.b} (@command{gcc})
5086 @cindex Biased representation
5087 This switch activates warnings when a size clause, value size clause, component
5088 clause, or component size clause forces the use of biased representation for an
5089 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5090 to represent 10/11). The default is that such warnings are generated.
5093 @emph{Suppress warnings on biased representation.}
5094 @cindex @option{-gnatwB} (@command{gcc})
5095 This switch suppresses warnings for representation clauses that force the use
5096 of biased representation.
5099 @emph{Activate warnings on conditionals.}
5100 @cindex @option{-gnatwc} (@command{gcc})
5101 @cindex Conditionals, constant
5102 This switch activates warnings for conditional expressions used in
5103 tests that are known to be True or False at compile time. The default
5104 is that such warnings are not generated.
5105 Note that this warning does
5106 not get issued for the use of boolean variables or constants whose
5107 values are known at compile time, since this is a standard technique
5108 for conditional compilation in Ada, and this would generate too many
5109 false positive warnings.
5111 This warning option also activates a special test for comparisons using
5112 the operators ``>='' and`` <=''.
5113 If the compiler can tell that only the equality condition is possible,
5114 then it will warn that the ``>'' or ``<'' part of the test
5115 is useless and that the operator could be replaced by ``=''.
5116 An example would be comparing a @code{Natural} variable <= 0.
5118 This warning option also generates warnings if
5119 one or both tests is optimized away in a membership test for integer
5120 values if the result can be determined at compile time. Range tests on
5121 enumeration types are not included, since it is common for such tests
5122 to include an end point.
5124 This warning can also be turned on using @option{-gnatwa}.
5127 @emph{Suppress warnings on conditionals.}
5128 @cindex @option{-gnatwC} (@command{gcc})
5129 This switch suppresses warnings for conditional expressions used in
5130 tests that are known to be True or False at compile time.
5133 @emph{Activate warnings on missing component clauses.}
5134 @cindex @option{-gnatw.c} (@command{gcc})
5135 @cindex Component clause, missing
5136 This switch activates warnings for record components where a record
5137 representation clause is present and has component clauses for the
5138 majority, but not all, of the components. A warning is given for each
5139 component for which no component clause is present.
5141 This warning can also be turned on using @option{-gnatwa}.
5144 @emph{Suppress warnings on missing component clauses.}
5145 @cindex @option{-gnatwC} (@command{gcc})
5146 This switch suppresses warnings for record components that are
5147 missing a component clause in the situation described above.
5150 @emph{Activate warnings on implicit dereferencing.}
5151 @cindex @option{-gnatwd} (@command{gcc})
5152 If this switch is set, then the use of a prefix of an access type
5153 in an indexed component, slice, or selected component without an
5154 explicit @code{.all} will generate a warning. With this warning
5155 enabled, access checks occur only at points where an explicit
5156 @code{.all} appears in the source code (assuming no warnings are
5157 generated as a result of this switch). The default is that such
5158 warnings are not generated.
5159 Note that @option{-gnatwa} does not affect the setting of
5160 this warning option.
5163 @emph{Suppress warnings on implicit dereferencing.}
5164 @cindex @option{-gnatwD} (@command{gcc})
5165 @cindex Implicit dereferencing
5166 @cindex Dereferencing, implicit
5167 This switch suppresses warnings for implicit dereferences in
5168 indexed components, slices, and selected components.
5171 @emph{Treat warnings as errors.}
5172 @cindex @option{-gnatwe} (@command{gcc})
5173 @cindex Warnings, treat as error
5174 This switch causes warning messages to be treated as errors.
5175 The warning string still appears, but the warning messages are counted
5176 as errors, and prevent the generation of an object file.
5179 @emph{Activate every optional warning}
5180 @cindex @option{-gnatw.e} (@command{gcc})
5181 @cindex Warnings, activate every optional warning
5182 This switch activates all optional warnings, including those which
5183 are not activated by @code{-gnatwa}.
5186 @emph{Activate warnings on unreferenced formals.}
5187 @cindex @option{-gnatwf} (@command{gcc})
5188 @cindex Formals, unreferenced
5189 This switch causes a warning to be generated if a formal parameter
5190 is not referenced in the body of the subprogram. This warning can
5191 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5192 default is that these warnings are not generated.
5195 @emph{Suppress warnings on unreferenced formals.}
5196 @cindex @option{-gnatwF} (@command{gcc})
5197 This switch suppresses warnings for unreferenced formal
5198 parameters. Note that the
5199 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5200 effect of warning on unreferenced entities other than subprogram
5204 @emph{Activate warnings on unrecognized pragmas.}
5205 @cindex @option{-gnatwg} (@command{gcc})
5206 @cindex Pragmas, unrecognized
5207 This switch causes a warning to be generated if an unrecognized
5208 pragma is encountered. Apart from issuing this warning, the
5209 pragma is ignored and has no effect. This warning can
5210 also be turned on using @option{-gnatwa}. The default
5211 is that such warnings are issued (satisfying the Ada Reference
5212 Manual requirement that such warnings appear).
5215 @emph{Suppress warnings on unrecognized pragmas.}
5216 @cindex @option{-gnatwG} (@command{gcc})
5217 This switch suppresses warnings for unrecognized pragmas.
5220 @emph{Activate warnings on hiding.}
5221 @cindex @option{-gnatwh} (@command{gcc})
5222 @cindex Hiding of Declarations
5223 This switch activates warnings on hiding declarations.
5224 A declaration is considered hiding
5225 if it is for a non-overloadable entity, and it declares an entity with the
5226 same name as some other entity that is directly or use-visible. The default
5227 is that such warnings are not generated.
5228 Note that @option{-gnatwa} does not affect the setting of this warning option.
5231 @emph{Suppress warnings on hiding.}
5232 @cindex @option{-gnatwH} (@command{gcc})
5233 This switch suppresses warnings on hiding declarations.
5236 @emph{Activate warnings on implementation units.}
5237 @cindex @option{-gnatwi} (@command{gcc})
5238 This switch activates warnings for a @code{with} of an internal GNAT
5239 implementation unit, defined as any unit from the @code{Ada},
5240 @code{Interfaces}, @code{GNAT},
5241 ^^@code{DEC},^ or @code{System}
5242 hierarchies that is not
5243 documented in either the Ada Reference Manual or the GNAT
5244 Programmer's Reference Manual. Such units are intended only
5245 for internal implementation purposes and should not be @code{with}'ed
5246 by user programs. The default is that such warnings are generated
5247 This warning can also be turned on using @option{-gnatwa}.
5250 @emph{Disable warnings on implementation units.}
5251 @cindex @option{-gnatwI} (@command{gcc})
5252 This switch disables warnings for a @code{with} of an internal GNAT
5253 implementation unit.
5256 @emph{Activate warnings on obsolescent features (Annex J).}
5257 @cindex @option{-gnatwj} (@command{gcc})
5258 @cindex Features, obsolescent
5259 @cindex Obsolescent features
5260 If this warning option is activated, then warnings are generated for
5261 calls to subprograms marked with @code{pragma Obsolescent} and
5262 for use of features in Annex J of the Ada Reference Manual. In the
5263 case of Annex J, not all features are flagged. In particular use
5264 of the renamed packages (like @code{Text_IO}) and use of package
5265 @code{ASCII} are not flagged, since these are very common and
5266 would generate many annoying positive warnings. The default is that
5267 such warnings are not generated. This warning is also turned on by
5268 the use of @option{-gnatwa}.
5270 In addition to the above cases, warnings are also generated for
5271 GNAT features that have been provided in past versions but which
5272 have been superseded (typically by features in the new Ada standard).
5273 For example, @code{pragma Ravenscar} will be flagged since its
5274 function is replaced by @code{pragma Profile(Ravenscar)}.
5276 Note that this warning option functions differently from the
5277 restriction @code{No_Obsolescent_Features} in two respects.
5278 First, the restriction applies only to annex J features.
5279 Second, the restriction does flag uses of package @code{ASCII}.
5282 @emph{Suppress warnings on obsolescent features (Annex J).}
5283 @cindex @option{-gnatwJ} (@command{gcc})
5284 This switch disables warnings on use of obsolescent features.
5287 @emph{Activate warnings on variables that could be constants.}
5288 @cindex @option{-gnatwk} (@command{gcc})
5289 This switch activates warnings for variables that are initialized but
5290 never modified, and then could be declared constants. The default is that
5291 such warnings are not given.
5292 This warning can also be turned on using @option{-gnatwa}.
5295 @emph{Suppress warnings on variables that could be constants.}
5296 @cindex @option{-gnatwK} (@command{gcc})
5297 This switch disables warnings on variables that could be declared constants.
5300 @emph{Activate warnings for elaboration pragmas.}
5301 @cindex @option{-gnatwl} (@command{gcc})
5302 @cindex Elaboration, warnings
5303 This switch activates warnings on missing
5304 @code{Elaborate_All} and @code{Elaborate} pragmas.
5305 See the section in this guide on elaboration checking for details on
5306 when such pragmas should be used. In dynamic elaboration mode, this switch
5307 generations warnings about the need to add elaboration pragmas. Note however,
5308 that if you blindly follow these warnings, and add @code{Elaborate_All}
5309 warnings wherever they are recommended, you basically end up with the
5310 equivalent of the static elaboration model, which may not be what you want for
5311 legacy code for which the static model does not work.
5313 For the static model, the messages generated are labeled "info:" (for
5314 information messages). They are not warnings to add elaboration pragmas,
5315 merely informational messages showing what implicit elaboration pragmas
5316 have been added, for use in analyzing elaboration circularity problems.
5318 Warnings are also generated if you
5319 are using the static mode of elaboration, and a @code{pragma Elaborate}
5320 is encountered. The default is that such warnings
5322 This warning is not automatically turned on by the use of @option{-gnatwa}.
5325 @emph{Suppress warnings for elaboration pragmas.}
5326 @cindex @option{-gnatwL} (@command{gcc})
5327 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5328 See the section in this guide on elaboration checking for details on
5329 when such pragmas should be used.
5332 @emph{Activate warnings on modified but unreferenced variables.}
5333 @cindex @option{-gnatwm} (@command{gcc})
5334 This switch activates warnings for variables that are assigned (using
5335 an initialization value or with one or more assignment statements) but
5336 whose value is never read. The warning is suppressed for volatile
5337 variables and also for variables that are renamings of other variables
5338 or for which an address clause is given.
5339 This warning can also be turned on using @option{-gnatwa}.
5340 The default is that these warnings are not given.
5343 @emph{Disable warnings on modified but unreferenced variables.}
5344 @cindex @option{-gnatwM} (@command{gcc})
5345 This switch disables warnings for variables that are assigned or
5346 initialized, but never read.
5349 @emph{Activate warnings on suspicious modulus values.}
5350 @cindex @option{-gnatw.m} (@command{gcc})
5351 This switch activates warnings for modulus values that seem suspicious.
5352 The cases caught are where the size is the same as the modulus (e.g.
5353 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5354 with no size clause. The guess in both cases is that 2**x was intended
5355 rather than x. The default is that these warnings are given.
5358 @emph{Disable warnings on suspicious modulus values.}
5359 @cindex @option{-gnatw.M} (@command{gcc})
5360 This switch disables warnings for suspicious modulus values.
5363 @emph{Set normal warnings mode.}
5364 @cindex @option{-gnatwn} (@command{gcc})
5365 This switch sets normal warning mode, in which enabled warnings are
5366 issued and treated as warnings rather than errors. This is the default
5367 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5368 an explicit @option{-gnatws} or
5369 @option{-gnatwe}. It also cancels the effect of the
5370 implicit @option{-gnatwe} that is activated by the
5371 use of @option{-gnatg}.
5374 @emph{Activate warnings on address clause overlays.}
5375 @cindex @option{-gnatwo} (@command{gcc})
5376 @cindex Address Clauses, warnings
5377 This switch activates warnings for possibly unintended initialization
5378 effects of defining address clauses that cause one variable to overlap
5379 another. The default is that such warnings are generated.
5380 This warning can also be turned on using @option{-gnatwa}.
5383 @emph{Suppress warnings on address clause overlays.}
5384 @cindex @option{-gnatwO} (@command{gcc})
5385 This switch suppresses warnings on possibly unintended initialization
5386 effects of defining address clauses that cause one variable to overlap
5390 @emph{Activate warnings on modified but unreferenced out parameters.}
5391 @cindex @option{-gnatw.o} (@command{gcc})
5392 This switch activates warnings for variables that are modified by using
5393 them as actuals for a call to a procedure with an out mode formal, where
5394 the resulting assigned value is never read. It is applicable in the case
5395 where there is more than one out mode formal. If there is only one out
5396 mode formal, the warning is issued by default (controlled by -gnatwu).
5397 The warning is suppressed for volatile
5398 variables and also for variables that are renamings of other variables
5399 or for which an address clause is given.
5400 The default is that these warnings are not given. Note that this warning
5401 is not included in -gnatwa, it must be activated explicitly.
5404 @emph{Disable warnings on modified but unreferenced out parameters.}
5405 @cindex @option{-gnatw.O} (@command{gcc})
5406 This switch suppresses warnings for variables that are modified by using
5407 them as actuals for a call to a procedure with an out mode formal, where
5408 the resulting assigned value is never read.
5411 @emph{Activate warnings on ineffective pragma Inlines.}
5412 @cindex @option{-gnatwp} (@command{gcc})
5413 @cindex Inlining, warnings
5414 This switch activates warnings for failure of front end inlining
5415 (activated by @option{-gnatN}) to inline a particular call. There are
5416 many reasons for not being able to inline a call, including most
5417 commonly that the call is too complex to inline. The default is
5418 that such warnings are not given.
5419 This warning can also be turned on using @option{-gnatwa}.
5420 Warnings on ineffective inlining by the gcc back-end can be activated
5421 separately, using the gcc switch -Winline.
5424 @emph{Suppress warnings on ineffective pragma Inlines.}
5425 @cindex @option{-gnatwP} (@command{gcc})
5426 This switch suppresses warnings on ineffective pragma Inlines. If the
5427 inlining mechanism cannot inline a call, it will simply ignore the
5431 @emph{Activate warnings on parameter ordering.}
5432 @cindex @option{-gnatw.p} (@command{gcc})
5433 @cindex Parameter order, warnings
5434 This switch activates warnings for cases of suspicious parameter
5435 ordering when the list of arguments are all simple identifiers that
5436 match the names of the formals, but are in a different order. The
5437 warning is suppressed if any use of named parameter notation is used,
5438 so this is the appropriate way to suppress a false positive (and
5439 serves to emphasize that the "misordering" is deliberate). The
5441 that such warnings are not given.
5442 This warning can also be turned on using @option{-gnatwa}.
5445 @emph{Suppress warnings on parameter ordering.}
5446 @cindex @option{-gnatw.P} (@command{gcc})
5447 This switch suppresses warnings on cases of suspicious parameter
5451 @emph{Activate warnings on questionable missing parentheses.}
5452 @cindex @option{-gnatwq} (@command{gcc})
5453 @cindex Parentheses, warnings
5454 This switch activates warnings for cases where parentheses are not used and
5455 the result is potential ambiguity from a readers point of view. For example
5456 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5457 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5458 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5459 follow the rule of always parenthesizing to make the association clear, and
5460 this warning switch warns if such parentheses are not present. The default
5461 is that these warnings are given.
5462 This warning can also be turned on using @option{-gnatwa}.
5465 @emph{Suppress warnings on questionable missing parentheses.}
5466 @cindex @option{-gnatwQ} (@command{gcc})
5467 This switch suppresses warnings for cases where the association is not
5468 clear and the use of parentheses is preferred.
5471 @emph{Activate warnings on redundant constructs.}
5472 @cindex @option{-gnatwr} (@command{gcc})
5473 This switch activates warnings for redundant constructs. The following
5474 is the current list of constructs regarded as redundant:
5478 Assignment of an item to itself.
5480 Type conversion that converts an expression to its own type.
5482 Use of the attribute @code{Base} where @code{typ'Base} is the same
5485 Use of pragma @code{Pack} when all components are placed by a record
5486 representation clause.
5488 Exception handler containing only a reraise statement (raise with no
5489 operand) which has no effect.
5491 Use of the operator abs on an operand that is known at compile time
5494 Comparison of boolean expressions to an explicit True value.
5497 This warning can also be turned on using @option{-gnatwa}.
5498 The default is that warnings for redundant constructs are not given.
5501 @emph{Suppress warnings on redundant constructs.}
5502 @cindex @option{-gnatwR} (@command{gcc})
5503 This switch suppresses warnings for redundant constructs.
5506 @emph{Activate warnings for object renaming function.}
5507 @cindex @option{-gnatw.r} (@command{gcc})
5508 This switch activates warnings for an object renaming that renames a
5509 function call, which is equivalent to a constant declaration (as
5510 opposed to renaming the function itself). The default is that these
5511 warnings are given. This warning can also be turned on using
5515 @emph{Suppress warnings for object renaming function.}
5516 @cindex @option{-gnatwT} (@command{gcc})
5517 This switch suppresses warnings for object renaming function.
5520 @emph{Suppress all warnings.}
5521 @cindex @option{-gnatws} (@command{gcc})
5522 This switch completely suppresses the
5523 output of all warning messages from the GNAT front end.
5524 Note that it does not suppress warnings from the @command{gcc} back end.
5525 To suppress these back end warnings as well, use the switch @option{-w}
5526 in addition to @option{-gnatws}.
5529 @emph{Activate warnings for tracking of deleted conditional code.}
5530 @cindex @option{-gnatwt} (@command{gcc})
5531 @cindex Deactivated code, warnings
5532 @cindex Deleted code, warnings
5533 This switch activates warnings for tracking of code in conditionals (IF and
5534 CASE statements) that is detected to be dead code which cannot be executed, and
5535 which is removed by the front end. This warning is off by default, and is not
5536 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5537 useful for detecting deactivated code in certified applications.
5540 @emph{Suppress warnings for tracking of deleted conditional code.}
5541 @cindex @option{-gnatwT} (@command{gcc})
5542 This switch suppresses warnings for tracking of deleted conditional code.
5545 @emph{Activate warnings on unused entities.}
5546 @cindex @option{-gnatwu} (@command{gcc})
5547 This switch activates warnings to be generated for entities that
5548 are declared but not referenced, and for units that are @code{with}'ed
5550 referenced. In the case of packages, a warning is also generated if
5551 no entities in the package are referenced. This means that if the package
5552 is referenced but the only references are in @code{use}
5553 clauses or @code{renames}
5554 declarations, a warning is still generated. A warning is also generated
5555 for a generic package that is @code{with}'ed but never instantiated.
5556 In the case where a package or subprogram body is compiled, and there
5557 is a @code{with} on the corresponding spec
5558 that is only referenced in the body,
5559 a warning is also generated, noting that the
5560 @code{with} can be moved to the body. The default is that
5561 such warnings are not generated.
5562 This switch also activates warnings on unreferenced formals
5563 (it includes the effect of @option{-gnatwf}).
5564 This warning can also be turned on using @option{-gnatwa}.
5567 @emph{Suppress warnings on unused entities.}
5568 @cindex @option{-gnatwU} (@command{gcc})
5569 This switch suppresses warnings for unused entities and packages.
5570 It also turns off warnings on unreferenced formals (and thus includes
5571 the effect of @option{-gnatwF}).
5574 @emph{Activate warnings on unassigned variables.}
5575 @cindex @option{-gnatwv} (@command{gcc})
5576 @cindex Unassigned variable warnings
5577 This switch activates warnings for access to variables which
5578 may not be properly initialized. The default is that
5579 such warnings are generated.
5580 This warning can also be turned on using @option{-gnatwa}.
5583 @emph{Suppress warnings on unassigned variables.}
5584 @cindex @option{-gnatwV} (@command{gcc})
5585 This switch suppresses warnings for access to variables which
5586 may not be properly initialized.
5587 For variables of a composite type, the warning can also be suppressed in
5588 Ada 2005 by using a default initialization with a box. For example, if
5589 Table is an array of records whose components are only partially uninitialized,
5590 then the following code:
5592 @smallexample @c ada
5593 Tab : Table := (others => <>);
5596 will suppress warnings on subsequent statements that access components
5600 @emph{Activate warnings on wrong low bound assumption.}
5601 @cindex @option{-gnatww} (@command{gcc})
5602 @cindex String indexing warnings
5603 This switch activates warnings for indexing an unconstrained string parameter
5604 with a literal or S'Length. This is a case where the code is assuming that the
5605 low bound is one, which is in general not true (for example when a slice is
5606 passed). The default is that such warnings are generated.
5607 This warning can also be turned on using @option{-gnatwa}.
5610 @emph{Suppress warnings on wrong low bound assumption.}
5611 @cindex @option{-gnatwW} (@command{gcc})
5612 This switch suppresses warnings for indexing an unconstrained string parameter
5613 with a literal or S'Length. Note that this warning can also be suppressed
5614 in a particular case by adding an
5615 assertion that the lower bound is 1,
5616 as shown in the following example.
5618 @smallexample @c ada
5619 procedure K (S : String) is
5620 pragma Assert (S'First = 1);
5625 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5626 @cindex @option{-gnatw.w} (@command{gcc})
5627 @cindex Warnings Off control
5628 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5629 where either the pragma is entirely useless (because it suppresses no
5630 warnings), or it could be replaced by @code{pragma Unreferenced} or
5631 @code{pragma Unmodified}.The default is that these warnings are not given.
5632 Note that this warning is not included in -gnatwa, it must be
5633 activated explicitly.
5636 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5637 @cindex @option{-gnatw.W} (@command{gcc})
5638 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5641 @emph{Activate warnings on Export/Import pragmas.}
5642 @cindex @option{-gnatwx} (@command{gcc})
5643 @cindex Export/Import pragma warnings
5644 This switch activates warnings on Export/Import pragmas when
5645 the compiler detects a possible conflict between the Ada and
5646 foreign language calling sequences. For example, the use of
5647 default parameters in a convention C procedure is dubious
5648 because the C compiler cannot supply the proper default, so
5649 a warning is issued. The default is that such warnings are
5651 This warning can also be turned on using @option{-gnatwa}.
5654 @emph{Suppress warnings on Export/Import pragmas.}
5655 @cindex @option{-gnatwX} (@command{gcc})
5656 This switch suppresses warnings on Export/Import pragmas.
5657 The sense of this is that you are telling the compiler that
5658 you know what you are doing in writing the pragma, and it
5659 should not complain at you.
5662 @emph{Activate warnings for No_Exception_Propagation mode.}
5663 @cindex @option{-gnatwm} (@command{gcc})
5664 This switch activates warnings for exception usage when pragma Restrictions
5665 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5666 explicit exception raises which are not covered by a local handler, and for
5667 exception handlers which do not cover a local raise. The default is that these
5668 warnings are not given.
5671 @emph{Disable warnings for No_Exception_Propagation mode.}
5672 This switch disables warnings for exception usage when pragma Restrictions
5673 (No_Exception_Propagation) is in effect.
5676 @emph{Activate warnings for Ada 2005 compatibility issues.}
5677 @cindex @option{-gnatwy} (@command{gcc})
5678 @cindex Ada 2005 compatibility issues warnings
5679 For the most part Ada 2005 is upwards compatible with Ada 95,
5680 but there are some exceptions (for example the fact that
5681 @code{interface} is now a reserved word in Ada 2005). This
5682 switch activates several warnings to help in identifying
5683 and correcting such incompatibilities. The default is that
5684 these warnings are generated. Note that at one point Ada 2005
5685 was called Ada 0Y, hence the choice of character.
5686 This warning can also be turned on using @option{-gnatwa}.
5689 @emph{Disable warnings for Ada 2005 compatibility issues.}
5690 @cindex @option{-gnatwY} (@command{gcc})
5691 @cindex Ada 2005 compatibility issues warnings
5692 This switch suppresses several warnings intended to help in identifying
5693 incompatibilities between Ada 95 and Ada 2005.
5696 @emph{Activate warnings on unchecked conversions.}
5697 @cindex @option{-gnatwz} (@command{gcc})
5698 @cindex Unchecked_Conversion warnings
5699 This switch activates warnings for unchecked conversions
5700 where the types are known at compile time to have different
5702 is that such warnings are generated. Warnings are also
5703 generated for subprogram pointers with different conventions,
5704 and, on VMS only, for data pointers with different conventions.
5705 This warning can also be turned on using @option{-gnatwa}.
5708 @emph{Suppress warnings on unchecked conversions.}
5709 @cindex @option{-gnatwZ} (@command{gcc})
5710 This switch suppresses warnings for unchecked conversions
5711 where the types are known at compile time to have different
5712 sizes or conventions.
5714 @item ^-Wunused^WARNINGS=UNUSED^
5715 @cindex @option{-Wunused}
5716 The warnings controlled by the @option{-gnatw} switch are generated by
5717 the front end of the compiler. The @option{GCC} back end can provide
5718 additional warnings and they are controlled by the @option{-W} switch.
5719 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5720 warnings for entities that are declared but not referenced.
5722 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5723 @cindex @option{-Wuninitialized}
5724 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5725 the back end warning for uninitialized variables. This switch must be
5726 used in conjunction with an optimization level greater than zero.
5728 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5729 @cindex @option{-Wall}
5730 This switch enables all the above warnings from the @option{GCC} back end.
5731 The code generator detects a number of warning situations that are missed
5732 by the @option{GNAT} front end, and this switch can be used to activate them.
5733 The use of this switch also sets the default front end warning mode to
5734 @option{-gnatwa}, that is, most front end warnings activated as well.
5736 @item ^-w^/NO_BACK_END_WARNINGS^
5738 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5739 The use of this switch also sets the default front end warning mode to
5740 @option{-gnatws}, that is, front end warnings suppressed as well.
5746 A string of warning parameters can be used in the same parameter. For example:
5753 will turn on all optional warnings except for elaboration pragma warnings,
5754 and also specify that warnings should be treated as errors.
5756 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5781 @node Debugging and Assertion Control
5782 @subsection Debugging and Assertion Control
5786 @cindex @option{-gnata} (@command{gcc})
5792 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5793 are ignored. This switch, where @samp{a} stands for assert, causes
5794 @code{Assert} and @code{Debug} pragmas to be activated.
5796 The pragmas have the form:
5800 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5801 @var{static-string-expression}@r{]})
5802 @b{pragma} Debug (@var{procedure call})
5807 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5808 If the result is @code{True}, the pragma has no effect (other than
5809 possible side effects from evaluating the expression). If the result is
5810 @code{False}, the exception @code{Assert_Failure} declared in the package
5811 @code{System.Assertions} is
5812 raised (passing @var{static-string-expression}, if present, as the
5813 message associated with the exception). If no string expression is
5814 given the default is a string giving the file name and line number
5817 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5818 @code{pragma Debug} may appear within a declaration sequence, allowing
5819 debugging procedures to be called between declarations.
5822 @item /DEBUG@r{[}=debug-level@r{]}
5824 Specifies how much debugging information is to be included in
5825 the resulting object file where 'debug-level' is one of the following:
5828 Include both debugger symbol records and traceback
5830 This is the default setting.
5832 Include both debugger symbol records and traceback in
5835 Excludes both debugger symbol records and traceback
5836 the object file. Same as /NODEBUG.
5838 Includes only debugger symbol records in the object
5839 file. Note that this doesn't include traceback information.
5844 @node Validity Checking
5845 @subsection Validity Checking
5846 @findex Validity Checking
5849 The Ada Reference Manual has specific requirements for checking
5850 for invalid values. In particular, RM 13.9.1 requires that the
5851 evaluation of invalid values (for example from unchecked conversions),
5852 not result in erroneous execution. In GNAT, the result of such an
5853 evaluation in normal default mode is to either use the value
5854 unmodified, or to raise Constraint_Error in those cases where use
5855 of the unmodified value would cause erroneous execution. The cases
5856 where unmodified values might lead to erroneous execution are case
5857 statements (where a wild jump might result from an invalid value),
5858 and subscripts on the left hand side (where memory corruption could
5859 occur as a result of an invalid value).
5861 The @option{-gnatB} switch tells the compiler to assume that all
5862 values are valid (that is, within their declared subtype range)
5863 except in the context of a use of the Valid attribute. This means
5864 the compiler can generate more efficient code, since the range
5865 of values is better known at compile time.
5867 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5870 The @code{x} argument is a string of letters that
5871 indicate validity checks that are performed or not performed in addition
5872 to the default checks described above.
5875 The options allowed for this qualifier
5876 indicate validity checks that are performed or not performed in addition
5877 to the default checks described above.
5883 @emph{All validity checks.}
5884 @cindex @option{-gnatVa} (@command{gcc})
5885 All validity checks are turned on.
5887 That is, @option{-gnatVa} is
5888 equivalent to @option{gnatVcdfimorst}.
5892 @emph{Validity checks for copies.}
5893 @cindex @option{-gnatVc} (@command{gcc})
5894 The right hand side of assignments, and the initializing values of
5895 object declarations are validity checked.
5898 @emph{Default (RM) validity checks.}
5899 @cindex @option{-gnatVd} (@command{gcc})
5900 Some validity checks are done by default following normal Ada semantics
5902 A check is done in case statements that the expression is within the range
5903 of the subtype. If it is not, Constraint_Error is raised.
5904 For assignments to array components, a check is done that the expression used
5905 as index is within the range. If it is not, Constraint_Error is raised.
5906 Both these validity checks may be turned off using switch @option{-gnatVD}.
5907 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5908 switch @option{-gnatVd} will leave the checks turned on.
5909 Switch @option{-gnatVD} should be used only if you are sure that all such
5910 expressions have valid values. If you use this switch and invalid values
5911 are present, then the program is erroneous, and wild jumps or memory
5912 overwriting may occur.
5915 @emph{Validity checks for elementary components.}
5916 @cindex @option{-gnatVe} (@command{gcc})
5917 In the absence of this switch, assignments to record or array components are
5918 not validity checked, even if validity checks for assignments generally
5919 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5920 require valid data, but assignment of individual components does. So for
5921 example, there is a difference between copying the elements of an array with a
5922 slice assignment, compared to assigning element by element in a loop. This
5923 switch allows you to turn off validity checking for components, even when they
5924 are assigned component by component.
5927 @emph{Validity checks for floating-point values.}
5928 @cindex @option{-gnatVf} (@command{gcc})
5929 In the absence of this switch, validity checking occurs only for discrete
5930 values. If @option{-gnatVf} is specified, then validity checking also applies
5931 for floating-point values, and NaNs and infinities are considered invalid,
5932 as well as out of range values for constrained types. Note that this means
5933 that standard IEEE infinity mode is not allowed. The exact contexts
5934 in which floating-point values are checked depends on the setting of other
5935 options. For example,
5936 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5937 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5938 (the order does not matter) specifies that floating-point parameters of mode
5939 @code{in} should be validity checked.
5942 @emph{Validity checks for @code{in} mode parameters}
5943 @cindex @option{-gnatVi} (@command{gcc})
5944 Arguments for parameters of mode @code{in} are validity checked in function
5945 and procedure calls at the point of call.
5948 @emph{Validity checks for @code{in out} mode parameters.}
5949 @cindex @option{-gnatVm} (@command{gcc})
5950 Arguments for parameters of mode @code{in out} are validity checked in
5951 procedure calls at the point of call. The @code{'m'} here stands for
5952 modify, since this concerns parameters that can be modified by the call.
5953 Note that there is no specific option to test @code{out} parameters,
5954 but any reference within the subprogram will be tested in the usual
5955 manner, and if an invalid value is copied back, any reference to it
5956 will be subject to validity checking.
5959 @emph{No validity checks.}
5960 @cindex @option{-gnatVn} (@command{gcc})
5961 This switch turns off all validity checking, including the default checking
5962 for case statements and left hand side subscripts. Note that the use of
5963 the switch @option{-gnatp} suppresses all run-time checks, including
5964 validity checks, and thus implies @option{-gnatVn}. When this switch
5965 is used, it cancels any other @option{-gnatV} previously issued.
5968 @emph{Validity checks for operator and attribute operands.}
5969 @cindex @option{-gnatVo} (@command{gcc})
5970 Arguments for predefined operators and attributes are validity checked.
5971 This includes all operators in package @code{Standard},
5972 the shift operators defined as intrinsic in package @code{Interfaces}
5973 and operands for attributes such as @code{Pos}. Checks are also made
5974 on individual component values for composite comparisons, and on the
5975 expressions in type conversions and qualified expressions. Checks are
5976 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5979 @emph{Validity checks for parameters.}
5980 @cindex @option{-gnatVp} (@command{gcc})
5981 This controls the treatment of parameters within a subprogram (as opposed
5982 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5983 of parameters on a call. If either of these call options is used, then
5984 normally an assumption is made within a subprogram that the input arguments
5985 have been validity checking at the point of call, and do not need checking
5986 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5987 is not made, and parameters are not assumed to be valid, so their validity
5988 will be checked (or rechecked) within the subprogram.
5991 @emph{Validity checks for function returns.}
5992 @cindex @option{-gnatVr} (@command{gcc})
5993 The expression in @code{return} statements in functions is validity
5997 @emph{Validity checks for subscripts.}
5998 @cindex @option{-gnatVs} (@command{gcc})
5999 All subscripts expressions are checked for validity, whether they appear
6000 on the right side or left side (in default mode only left side subscripts
6001 are validity checked).
6004 @emph{Validity checks for tests.}
6005 @cindex @option{-gnatVt} (@command{gcc})
6006 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6007 statements are checked, as well as guard expressions in entry calls.
6012 The @option{-gnatV} switch may be followed by
6013 ^a string of letters^a list of options^
6014 to turn on a series of validity checking options.
6016 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6017 specifies that in addition to the default validity checking, copies and
6018 function return expressions are to be validity checked.
6019 In order to make it easier
6020 to specify the desired combination of effects,
6022 the upper case letters @code{CDFIMORST} may
6023 be used to turn off the corresponding lower case option.
6026 the prefix @code{NO} on an option turns off the corresponding validity
6029 @item @code{NOCOPIES}
6030 @item @code{NODEFAULT}
6031 @item @code{NOFLOATS}
6032 @item @code{NOIN_PARAMS}
6033 @item @code{NOMOD_PARAMS}
6034 @item @code{NOOPERANDS}
6035 @item @code{NORETURNS}
6036 @item @code{NOSUBSCRIPTS}
6037 @item @code{NOTESTS}
6041 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6042 turns on all validity checking options except for
6043 checking of @code{@b{in out}} procedure arguments.
6045 The specification of additional validity checking generates extra code (and
6046 in the case of @option{-gnatVa} the code expansion can be substantial).
6047 However, these additional checks can be very useful in detecting
6048 uninitialized variables, incorrect use of unchecked conversion, and other
6049 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6050 is useful in conjunction with the extra validity checking, since this
6051 ensures that wherever possible uninitialized variables have invalid values.
6053 See also the pragma @code{Validity_Checks} which allows modification of
6054 the validity checking mode at the program source level, and also allows for
6055 temporary disabling of validity checks.
6057 @node Style Checking
6058 @subsection Style Checking
6059 @findex Style checking
6062 The @option{-gnaty^x^(option,option,@dots{})^} switch
6063 @cindex @option{-gnaty} (@command{gcc})
6064 causes the compiler to
6065 enforce specified style rules. A limited set of style rules has been used
6066 in writing the GNAT sources themselves. This switch allows user programs
6067 to activate all or some of these checks. If the source program fails a
6068 specified style check, an appropriate warning message is given, preceded by
6069 the character sequence ``(style)''.
6071 @code{(option,option,@dots{})} is a sequence of keywords
6074 The string @var{x} is a sequence of letters or digits
6076 indicating the particular style
6077 checks to be performed. The following checks are defined:
6082 @emph{Specify indentation level.}
6083 If a digit from 1-9 appears
6084 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6085 then proper indentation is checked, with the digit indicating the
6086 indentation level required. A value of zero turns off this style check.
6087 The general style of required indentation is as specified by
6088 the examples in the Ada Reference Manual. Full line comments must be
6089 aligned with the @code{--} starting on a column that is a multiple of
6090 the alignment level, or they may be aligned the same way as the following
6091 non-blank line (this is useful when full line comments appear in the middle
6095 @emph{Check attribute casing.}
6096 Attribute names, including the case of keywords such as @code{digits}
6097 used as attributes 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 ^A^ARRAY_INDEXES^
6102 @emph{Use of array index numbers in array attributes.}
6103 When using the array attributes First, Last, Range,
6104 or Length, the index number must be omitted for one-dimensional arrays
6105 and is required for multi-dimensional arrays.
6108 @emph{Blanks not allowed at statement end.}
6109 Trailing blanks are not allowed at the end of statements. The purpose of this
6110 rule, together with h (no horizontal tabs), is to enforce a canonical format
6111 for the use of blanks to separate source tokens.
6114 @emph{Check comments.}
6115 Comments must meet the following set of rules:
6120 The ``@code{--}'' that starts the column must either start in column one,
6121 or else at least one blank must precede this sequence.
6124 Comments that follow other tokens on a line must have at least one blank
6125 following the ``@code{--}'' at the start of the comment.
6128 Full line comments must have two blanks following the ``@code{--}'' that
6129 starts the comment, with the following exceptions.
6132 A line consisting only of the ``@code{--}'' characters, possibly preceded
6133 by blanks is permitted.
6136 A comment starting with ``@code{--x}'' where @code{x} is a special character
6138 This allows proper processing of the output generated by specialized tools
6139 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6141 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6142 special character is defined as being in one of the ASCII ranges
6143 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6144 Note that this usage is not permitted
6145 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6148 A line consisting entirely of minus signs, possibly preceded by blanks, is
6149 permitted. This allows the construction of box comments where lines of minus
6150 signs are used to form the top and bottom of the box.
6153 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6154 least one blank follows the initial ``@code{--}''. Together with the preceding
6155 rule, this allows the construction of box comments, as shown in the following
6158 ---------------------------
6159 -- This is a box comment --
6160 -- with two text lines. --
6161 ---------------------------
6165 @item ^d^DOS_LINE_ENDINGS^
6166 @emph{Check no DOS line terminators present.}
6167 All lines must be terminated by a single ASCII.LF
6168 character (in particular the DOS line terminator sequence CR/LF is not
6172 @emph{Check end/exit labels.}
6173 Optional labels on @code{end} statements ending subprograms and on
6174 @code{exit} statements exiting named loops, are required to be present.
6177 @emph{No form feeds or vertical tabs.}
6178 Neither form feeds nor vertical tab characters are permitted
6182 @emph{GNAT style mode}
6183 The set of style check switches is set to match that used by the GNAT sources.
6184 This may be useful when developing code that is eventually intended to be
6185 incorporated into GNAT. For further details, see GNAT sources.
6188 @emph{No horizontal tabs.}
6189 Horizontal tab characters are not permitted in the source text.
6190 Together with the b (no blanks at end of line) check, this
6191 enforces a canonical form for the use of blanks to separate
6195 @emph{Check if-then layout.}
6196 The keyword @code{then} must appear either on the same
6197 line as corresponding @code{if}, or on a line on its own, lined
6198 up under the @code{if} with at least one non-blank line in between
6199 containing all or part of the condition to be tested.
6202 @emph{check mode IN keywords}
6203 Mode @code{in} (the default mode) is not
6204 allowed to be given explicitly. @code{in out} is fine,
6205 but not @code{in} on its own.
6208 @emph{Check keyword casing.}
6209 All keywords must be in lower case (with the exception of keywords
6210 such as @code{digits} used as attribute names to which this check
6214 @emph{Check layout.}
6215 Layout of statement and declaration constructs must follow the
6216 recommendations in the Ada Reference Manual, as indicated by the
6217 form of the syntax rules. For example an @code{else} keyword must
6218 be lined up with the corresponding @code{if} keyword.
6220 There are two respects in which the style rule enforced by this check
6221 option are more liberal than those in the Ada Reference Manual. First
6222 in the case of record declarations, it is permissible to put the
6223 @code{record} keyword on the same line as the @code{type} keyword, and
6224 then the @code{end} in @code{end record} must line up under @code{type}.
6225 This is also permitted when the type declaration is split on two lines.
6226 For example, any of the following three layouts is acceptable:
6228 @smallexample @c ada
6251 Second, in the case of a block statement, a permitted alternative
6252 is to put the block label on the same line as the @code{declare} or
6253 @code{begin} keyword, and then line the @code{end} keyword up under
6254 the block label. For example both the following are permitted:
6256 @smallexample @c ada
6274 The same alternative format is allowed for loops. For example, both of
6275 the following are permitted:
6277 @smallexample @c ada
6279 Clear : while J < 10 loop
6290 @item ^Lnnn^MAX_NESTING=nnn^
6291 @emph{Set maximum nesting level}
6292 The maximum level of nesting of constructs (including subprograms, loops,
6293 blocks, packages, and conditionals) may not exceed the given value
6294 @option{nnn}. A value of zero disconnects this style check.
6296 @item ^m^LINE_LENGTH^
6297 @emph{Check maximum line length.}
6298 The length of source lines must not exceed 79 characters, including
6299 any trailing blanks. The value of 79 allows convenient display on an
6300 80 character wide device or window, allowing for possible special
6301 treatment of 80 character lines. Note that this count is of
6302 characters in the source text. This means that a tab character counts
6303 as one character in this count but a wide character sequence counts as
6304 a single character (however many bytes are needed in the encoding).
6306 @item ^Mnnn^MAX_LENGTH=nnn^
6307 @emph{Set maximum line length.}
6308 The length of lines must not exceed the
6309 given value @option{nnn}. The maximum value that can be specified is 32767.
6311 @item ^n^STANDARD_CASING^
6312 @emph{Check casing of entities in Standard.}
6313 Any identifier from Standard must be cased
6314 to match the presentation in the Ada Reference Manual (for example,
6315 @code{Integer} and @code{ASCII.NUL}).
6318 @emph{Turn off all style checks}
6319 All style check options are turned off.
6321 @item ^o^ORDERED_SUBPROGRAMS^
6322 @emph{Check order of subprogram bodies.}
6323 All subprogram bodies in a given scope
6324 (e.g.@: a package body) must be in alphabetical order. The ordering
6325 rule uses normal Ada rules for comparing strings, ignoring casing
6326 of letters, except that if there is a trailing numeric suffix, then
6327 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6330 @item ^O^OVERRIDING_INDICATORS^
6331 @emph{Check that overriding subprograms are explicitly marked as such.}
6332 The declaration of a primitive operation of a type extension that overrides
6333 an inherited operation must carry an overriding indicator.
6336 @emph{Check pragma casing.}
6337 Pragma names must be written in mixed case, that is, the
6338 initial letter and any letter following an underscore must be uppercase.
6339 All other letters must be lowercase.
6341 @item ^r^REFERENCES^
6342 @emph{Check references.}
6343 All identifier references must be cased in the same way as the
6344 corresponding declaration. No specific casing style is imposed on
6345 identifiers. The only requirement is for consistency of references
6348 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6349 @emph{Check no statements after THEN/ELSE.}
6350 No statements are allowed
6351 on the same line as a THEN or ELSE keyword following the
6352 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6353 and a special exception allows a pragma to appear after ELSE.
6356 @emph{Check separate specs.}
6357 Separate declarations (``specs'') are required for subprograms (a
6358 body is not allowed to serve as its own declaration). The only
6359 exception is that parameterless library level procedures are
6360 not required to have a separate declaration. This exception covers
6361 the most frequent form of main program procedures.
6364 @emph{Check token spacing.}
6365 The following token spacing rules are enforced:
6370 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6373 The token @code{=>} must be surrounded by spaces.
6376 The token @code{<>} must be preceded by a space or a left parenthesis.
6379 Binary operators other than @code{**} must be surrounded by spaces.
6380 There is no restriction on the layout of the @code{**} binary operator.
6383 Colon must be surrounded by spaces.
6386 Colon-equal (assignment, initialization) must be surrounded by spaces.
6389 Comma must be the first non-blank character on the line, or be
6390 immediately preceded by a non-blank character, and must be followed
6394 If the token preceding a left parenthesis ends with a letter or digit, then
6395 a space must separate the two tokens.
6398 A right parenthesis must either be the first non-blank character on
6399 a line, or it must be preceded by a non-blank character.
6402 A semicolon must not be preceded by a space, and must not be followed by
6403 a non-blank character.
6406 A unary plus or minus may not be followed by a space.
6409 A vertical bar must be surrounded by spaces.
6412 @item ^u^UNNECESSARY_BLANK_LINES^
6413 @emph{Check unnecessary blank lines.}
6414 Unnecessary blank lines are not allowed. A blank line is considered
6415 unnecessary if it appears at the end of the file, or if more than
6416 one blank line occurs in sequence.
6418 @item ^x^XTRA_PARENS^
6419 @emph{Check extra parentheses.}
6420 Unnecessary extra level of parentheses (C-style) are not allowed
6421 around conditions in @code{if} statements, @code{while} statements and
6422 @code{exit} statements.
6424 @item ^y^ALL_BUILTIN^
6425 @emph{Set all standard style check options}
6426 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6427 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6428 @option{-gnatyS}, @option{-gnatyLnnn},
6429 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6433 @emph{Remove style check options}
6434 This causes any subsequent options in the string to act as canceling the
6435 corresponding style check option. To cancel maximum nesting level control,
6436 use @option{L} parameter witout any integer value after that, because any
6437 digit following @option{-} in the parameter string of the @option{-gnaty}
6438 option will be threated as canceling indentation check. The same is true
6439 for @option{M} parameter. @option{y} and @option{N} parameters are not
6440 allowed after @option{-}.
6443 This causes any subsequent options in the string to enable the corresponding
6444 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6450 @emph{Removing style check options}
6451 If the name of a style check is preceded by @option{NO} then the corresponding
6452 style check is turned off. For example @option{NOCOMMENTS} turns off style
6453 checking for comments.
6458 In the above rules, appearing in column one is always permitted, that is,
6459 counts as meeting either a requirement for a required preceding space,
6460 or as meeting a requirement for no preceding space.
6462 Appearing at the end of a line is also always permitted, that is, counts
6463 as meeting either a requirement for a following space, or as meeting
6464 a requirement for no following space.
6467 If any of these style rules is violated, a message is generated giving
6468 details on the violation. The initial characters of such messages are
6469 always ``@code{(style)}''. Note that these messages are treated as warning
6470 messages, so they normally do not prevent the generation of an object
6471 file. The @option{-gnatwe} switch can be used to treat warning messages,
6472 including style messages, as fatal errors.
6476 @option{-gnaty} on its own (that is not
6477 followed by any letters or digits), then the effect is equivalent
6478 to the use of @option{-gnatyy}, as described above, that is all
6479 built-in standard style check options are enabled.
6483 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6484 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6485 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6497 clears any previously set style checks.
6499 @node Run-Time Checks
6500 @subsection Run-Time Checks
6501 @cindex Division by zero
6502 @cindex Access before elaboration
6503 @cindex Checks, division by zero
6504 @cindex Checks, access before elaboration
6505 @cindex Checks, stack overflow checking
6508 By default, the following checks are suppressed: integer overflow
6509 checks, stack overflow checks, and checks for access before
6510 elaboration on subprogram calls. All other checks, including range
6511 checks and array bounds checks, are turned on by default. The
6512 following @command{gcc} switches refine this default behavior.
6517 @cindex @option{-gnatp} (@command{gcc})
6518 @cindex Suppressing checks
6519 @cindex Checks, suppressing
6521 This switch causes the unit to be compiled
6522 as though @code{pragma Suppress (All_checks)}
6523 had been present in the source. Validity checks are also eliminated (in
6524 other words @option{-gnatp} also implies @option{-gnatVn}.
6525 Use this switch to improve the performance
6526 of the code at the expense of safety in the presence of invalid data or
6529 Note that when checks are suppressed, the compiler is allowed, but not
6530 required, to omit the checking code. If the run-time cost of the
6531 checking code is zero or near-zero, the compiler will generate it even
6532 if checks are suppressed. In particular, if the compiler can prove
6533 that a certain check will necessarily fail, it will generate code to
6534 do an unconditional ``raise'', even if checks are suppressed. The
6535 compiler warns in this case. Another case in which checks may not be
6536 eliminated is when they are embedded in certain run time routines such
6537 as math library routines.
6539 Of course, run-time checks are omitted whenever the compiler can prove
6540 that they will not fail, whether or not checks are suppressed.
6542 Note that if you suppress a check that would have failed, program
6543 execution is erroneous, which means the behavior is totally
6544 unpredictable. The program might crash, or print wrong answers, or
6545 do anything else. It might even do exactly what you wanted it to do
6546 (and then it might start failing mysteriously next week or next
6547 year). The compiler will generate code based on the assumption that
6548 the condition being checked is true, which can result in disaster if
6549 that assumption is wrong.
6552 @cindex @option{-gnato} (@command{gcc})
6553 @cindex Overflow checks
6554 @cindex Check, overflow
6555 Enables overflow checking for integer operations.
6556 This causes GNAT to generate slower and larger executable
6557 programs by adding code to check for overflow (resulting in raising
6558 @code{Constraint_Error} as required by standard Ada
6559 semantics). These overflow checks correspond to situations in which
6560 the true value of the result of an operation may be outside the base
6561 range of the result type. The following example shows the distinction:
6563 @smallexample @c ada
6564 X1 : Integer := "Integer'Last";
6565 X2 : Integer range 1 .. 5 := "5";
6566 X3 : Integer := "Integer'Last";
6567 X4 : Integer range 1 .. 5 := "5";
6568 F : Float := "2.0E+20";
6577 Note that if explicit values are assigned at compile time, the
6578 compiler may be able to detect overflow at compile time, in which case
6579 no actual run-time checking code is required, and Constraint_Error
6580 will be raised unconditionally, with or without
6581 @option{-gnato}. That's why the assigned values in the above fragment
6582 are in quotes, the meaning is "assign a value not known to the
6583 compiler that happens to be equal to ...". The remaining discussion
6584 assumes that the compiler cannot detect the values at compile time.
6586 Here the first addition results in a value that is outside the base range
6587 of Integer, and hence requires an overflow check for detection of the
6588 constraint error. Thus the first assignment to @code{X1} raises a
6589 @code{Constraint_Error} exception only if @option{-gnato} is set.
6591 The second increment operation results in a violation of the explicit
6592 range constraint; such range checks are performed by default, and are
6593 unaffected by @option{-gnato}.
6595 The two conversions of @code{F} both result in values that are outside
6596 the base range of type @code{Integer} and thus will raise
6597 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6598 The fact that the result of the second conversion is assigned to
6599 variable @code{X4} with a restricted range is irrelevant, since the problem
6600 is in the conversion, not the assignment.
6602 Basically the rule is that in the default mode (@option{-gnato} not
6603 used), the generated code assures that all integer variables stay
6604 within their declared ranges, or within the base range if there is
6605 no declared range. This prevents any serious problems like indexes
6606 out of range for array operations.
6608 What is not checked in default mode is an overflow that results in
6609 an in-range, but incorrect value. In the above example, the assignments
6610 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6611 range of the target variable, but the result is wrong in the sense that
6612 it is too large to be represented correctly. Typically the assignment
6613 to @code{X1} will result in wrap around to the largest negative number.
6614 The conversions of @code{F} will result in some @code{Integer} value
6615 and if that integer value is out of the @code{X4} range then the
6616 subsequent assignment would generate an exception.
6618 @findex Machine_Overflows
6619 Note that the @option{-gnato} switch does not affect the code generated
6620 for any floating-point operations; it applies only to integer
6622 For floating-point, GNAT has the @code{Machine_Overflows}
6623 attribute set to @code{False} and the normal mode of operation is to
6624 generate IEEE NaN and infinite values on overflow or invalid operations
6625 (such as dividing 0.0 by 0.0).
6627 The reason that we distinguish overflow checking from other kinds of
6628 range constraint checking is that a failure of an overflow check, unlike
6629 for example the failure of a range check, can result in an incorrect
6630 value, but cannot cause random memory destruction (like an out of range
6631 subscript), or a wild jump (from an out of range case value). Overflow
6632 checking is also quite expensive in time and space, since in general it
6633 requires the use of double length arithmetic.
6635 Note again that @option{-gnato} is off by default, so overflow checking is
6636 not performed in default mode. This means that out of the box, with the
6637 default settings, GNAT does not do all the checks expected from the
6638 language description in the Ada Reference Manual. If you want all constraint
6639 checks to be performed, as described in this Manual, then you must
6640 explicitly use the -gnato switch either on the @command{gnatmake} or
6641 @command{gcc} command.
6644 @cindex @option{-gnatE} (@command{gcc})
6645 @cindex Elaboration checks
6646 @cindex Check, elaboration
6647 Enables dynamic checks for access-before-elaboration
6648 on subprogram calls and generic instantiations.
6649 Note that @option{-gnatE} is not necessary for safety, because in the
6650 default mode, GNAT ensures statically that the checks would not fail.
6651 For full details of the effect and use of this switch,
6652 @xref{Compiling Using gcc}.
6655 @cindex @option{-fstack-check} (@command{gcc})
6656 @cindex Stack Overflow Checking
6657 @cindex Checks, stack overflow checking
6658 Activates stack overflow checking. For full details of the effect and use of
6659 this switch see @ref{Stack Overflow Checking}.
6664 The setting of these switches only controls the default setting of the
6665 checks. You may modify them using either @code{Suppress} (to remove
6666 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6669 @node Using gcc for Syntax Checking
6670 @subsection Using @command{gcc} for Syntax Checking
6673 @cindex @option{-gnats} (@command{gcc})
6677 The @code{s} stands for ``syntax''.
6680 Run GNAT in syntax checking only mode. For
6681 example, the command
6684 $ gcc -c -gnats x.adb
6688 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6689 series of files in a single command
6691 , and can use wild cards to specify such a group of files.
6692 Note that you must specify the @option{-c} (compile
6693 only) flag in addition to the @option{-gnats} flag.
6696 You may use other switches in conjunction with @option{-gnats}. In
6697 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6698 format of any generated error messages.
6700 When the source file is empty or contains only empty lines and/or comments,
6701 the output is a warning:
6704 $ gcc -c -gnats -x ada toto.txt
6705 toto.txt:1:01: warning: empty file, contains no compilation units
6709 Otherwise, the output is simply the error messages, if any. No object file or
6710 ALI file is generated by a syntax-only compilation. Also, no units other
6711 than the one specified are accessed. For example, if a unit @code{X}
6712 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6713 check only mode does not access the source file containing unit
6716 @cindex Multiple units, syntax checking
6717 Normally, GNAT allows only a single unit in a source file. However, this
6718 restriction does not apply in syntax-check-only mode, and it is possible
6719 to check a file containing multiple compilation units concatenated
6720 together. This is primarily used by the @code{gnatchop} utility
6721 (@pxref{Renaming Files Using gnatchop}).
6724 @node Using gcc for Semantic Checking
6725 @subsection Using @command{gcc} for Semantic Checking
6728 @cindex @option{-gnatc} (@command{gcc})
6732 The @code{c} stands for ``check''.
6734 Causes the compiler to operate in semantic check mode,
6735 with full checking for all illegalities specified in the
6736 Ada Reference Manual, but without generation of any object code
6737 (no object file is generated).
6739 Because dependent files must be accessed, you must follow the GNAT
6740 semantic restrictions on file structuring to operate in this mode:
6744 The needed source files must be accessible
6745 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6748 Each file must contain only one compilation unit.
6751 The file name and unit name must match (@pxref{File Naming Rules}).
6754 The output consists of error messages as appropriate. No object file is
6755 generated. An @file{ALI} file is generated for use in the context of
6756 cross-reference tools, but this file is marked as not being suitable
6757 for binding (since no object file is generated).
6758 The checking corresponds exactly to the notion of
6759 legality in the Ada Reference Manual.
6761 Any unit can be compiled in semantics-checking-only mode, including
6762 units that would not normally be compiled (subunits,
6763 and specifications where a separate body is present).
6766 @node Compiling Different Versions of Ada
6767 @subsection Compiling Different Versions of Ada
6770 The switches described in this section allow you to explicitly specify
6771 the version of the Ada language that your programs are written in.
6772 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6773 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6774 indicate Ada 83 compatibility mode.
6777 @cindex Compatibility with Ada 83
6779 @item -gnat83 (Ada 83 Compatibility Mode)
6780 @cindex @option{-gnat83} (@command{gcc})
6781 @cindex ACVC, Ada 83 tests
6785 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6786 specifies that the program is to be compiled in Ada 83 mode. With
6787 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6788 semantics where this can be done easily.
6789 It is not possible to guarantee this switch does a perfect
6790 job; some subtle tests, such as are
6791 found in earlier ACVC tests (and that have been removed from the ACATS suite
6792 for Ada 95), might not compile correctly.
6793 Nevertheless, this switch may be useful in some circumstances, for example
6794 where, due to contractual reasons, existing code needs to be maintained
6795 using only Ada 83 features.
6797 With few exceptions (most notably the need to use @code{<>} on
6798 @cindex Generic formal parameters
6799 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6800 reserved words, and the use of packages
6801 with optional bodies), it is not necessary to specify the
6802 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6803 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6804 a correct Ada 83 program is usually also a correct program
6805 in these later versions of the language standard.
6806 For further information, please refer to @ref{Compatibility and Porting Guide}.
6808 @item -gnat95 (Ada 95 mode)
6809 @cindex @option{-gnat95} (@command{gcc})
6813 This switch directs the compiler to implement the Ada 95 version of the
6815 Since Ada 95 is almost completely upwards
6816 compatible with Ada 83, Ada 83 programs may generally be compiled using
6817 this switch (see the description of the @option{-gnat83} switch for further
6818 information about Ada 83 mode).
6819 If an Ada 2005 program is compiled in Ada 95 mode,
6820 uses of the new Ada 2005 features will cause error
6821 messages or warnings.
6823 This switch also can be used to cancel the effect of a previous
6824 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6826 @item -gnat05 (Ada 2005 mode)
6827 @cindex @option{-gnat05} (@command{gcc})
6828 @cindex Ada 2005 mode
6831 This switch directs the compiler to implement the Ada 2005 version of the
6833 Since Ada 2005 is almost completely upwards
6834 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6835 may generally be compiled using this switch (see the description of the
6836 @option{-gnat83} and @option{-gnat95} switches for further
6839 For information about the approved ``Ada Issues'' that have been incorporated
6840 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6841 Included with GNAT releases is a file @file{features-ada0y} that describes
6842 the set of implemented Ada 2005 features.
6846 @node Character Set Control
6847 @subsection Character Set Control
6849 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6850 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6853 Normally GNAT recognizes the Latin-1 character set in source program
6854 identifiers, as described in the Ada Reference Manual.
6856 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6857 single character ^^or word^ indicating the character set, as follows:
6861 ISO 8859-1 (Latin-1) identifiers
6864 ISO 8859-2 (Latin-2) letters allowed in identifiers
6867 ISO 8859-3 (Latin-3) letters allowed in identifiers
6870 ISO 8859-4 (Latin-4) letters allowed in identifiers
6873 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6876 ISO 8859-15 (Latin-9) letters allowed in identifiers
6879 IBM PC letters (code page 437) allowed in identifiers
6882 IBM PC letters (code page 850) allowed in identifiers
6884 @item ^f^FULL_UPPER^
6885 Full upper-half codes allowed in identifiers
6888 No upper-half codes allowed in identifiers
6891 Wide-character codes (that is, codes greater than 255)
6892 allowed in identifiers
6895 @xref{Foreign Language Representation}, for full details on the
6896 implementation of these character sets.
6898 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6899 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6900 Specify the method of encoding for wide characters.
6901 @var{e} is one of the following:
6906 Hex encoding (brackets coding also recognized)
6909 Upper half encoding (brackets encoding also recognized)
6912 Shift/JIS encoding (brackets encoding also recognized)
6915 EUC encoding (brackets encoding also recognized)
6918 UTF-8 encoding (brackets encoding also recognized)
6921 Brackets encoding only (default value)
6923 For full details on these encoding
6924 methods see @ref{Wide Character Encodings}.
6925 Note that brackets coding is always accepted, even if one of the other
6926 options is specified, so for example @option{-gnatW8} specifies that both
6927 brackets and UTF-8 encodings will be recognized. The units that are
6928 with'ed directly or indirectly will be scanned using the specified
6929 representation scheme, and so if one of the non-brackets scheme is
6930 used, it must be used consistently throughout the program. However,
6931 since brackets encoding is always recognized, it may be conveniently
6932 used in standard libraries, allowing these libraries to be used with
6933 any of the available coding schemes.
6936 If no @option{-gnatW?} parameter is present, then the default
6937 representation is normally Brackets encoding only. However, if the
6938 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6939 byte order mark or BOM for UTF-8), then these three characters are
6940 skipped and the default representation for the file is set to UTF-8.
6942 Note that the wide character representation that is specified (explicitly
6943 or by default) for the main program also acts as the default encoding used
6944 for Wide_Text_IO files if not specifically overridden by a WCEM form
6948 @node File Naming Control
6949 @subsection File Naming Control
6952 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6953 @cindex @option{-gnatk} (@command{gcc})
6954 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6955 1-999, indicates the maximum allowable length of a file name (not
6956 including the @file{.ads} or @file{.adb} extension). The default is not
6957 to enable file name krunching.
6959 For the source file naming rules, @xref{File Naming Rules}.
6962 @node Subprogram Inlining Control
6963 @subsection Subprogram Inlining Control
6968 @cindex @option{-gnatn} (@command{gcc})
6970 The @code{n} here is intended to suggest the first syllable of the
6973 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6974 inlining to actually occur, optimization must be enabled. To enable
6975 inlining of subprograms specified by pragma @code{Inline},
6976 you must also specify this switch.
6977 In the absence of this switch, GNAT does not attempt
6978 inlining and does not need to access the bodies of
6979 subprograms for which @code{pragma Inline} is specified if they are not
6980 in the current unit.
6982 If you specify this switch the compiler will access these bodies,
6983 creating an extra source dependency for the resulting object file, and
6984 where possible, the call will be inlined.
6985 For further details on when inlining is possible
6986 see @ref{Inlining of Subprograms}.
6989 @cindex @option{-gnatN} (@command{gcc})
6990 This switch activates front-end inlining which also
6991 generates additional dependencies.
6993 When using a gcc-based back end (in practice this means using any version
6994 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
6995 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
6996 Historically front end inlining was more extensive than the gcc back end
6997 inlining, but that is no longer the case.
7000 @node Auxiliary Output Control
7001 @subsection Auxiliary Output Control
7005 @cindex @option{-gnatt} (@command{gcc})
7006 @cindex Writing internal trees
7007 @cindex Internal trees, writing to file
7008 Causes GNAT to write the internal tree for a unit to a file (with the
7009 extension @file{.adt}.
7010 This not normally required, but is used by separate analysis tools.
7012 these tools do the necessary compilations automatically, so you should
7013 not have to specify this switch in normal operation.
7014 Note that the combination of switches @option{-gnatct}
7015 generates a tree in the form required by ASIS applications.
7018 @cindex @option{-gnatu} (@command{gcc})
7019 Print a list of units required by this compilation on @file{stdout}.
7020 The listing includes all units on which the unit being compiled depends
7021 either directly or indirectly.
7024 @item -pass-exit-codes
7025 @cindex @option{-pass-exit-codes} (@command{gcc})
7026 If this switch is not used, the exit code returned by @command{gcc} when
7027 compiling multiple files indicates whether all source files have
7028 been successfully used to generate object files or not.
7030 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7031 exit status and allows an integrated development environment to better
7032 react to a compilation failure. Those exit status are:
7036 There was an error in at least one source file.
7038 At least one source file did not generate an object file.
7040 The compiler died unexpectedly (internal error for example).
7042 An object file has been generated for every source file.
7047 @node Debugging Control
7048 @subsection Debugging Control
7052 @cindex Debugging options
7055 @cindex @option{-gnatd} (@command{gcc})
7056 Activate internal debugging switches. @var{x} is a letter or digit, or
7057 string of letters or digits, which specifies the type of debugging
7058 outputs desired. Normally these are used only for internal development
7059 or system debugging purposes. You can find full documentation for these
7060 switches in the body of the @code{Debug} unit in the compiler source
7061 file @file{debug.adb}.
7065 @cindex @option{-gnatG} (@command{gcc})
7066 This switch causes the compiler to generate auxiliary output containing
7067 a pseudo-source listing of the generated expanded code. Like most Ada
7068 compilers, GNAT works by first transforming the high level Ada code into
7069 lower level constructs. For example, tasking operations are transformed
7070 into calls to the tasking run-time routines. A unique capability of GNAT
7071 is to list this expanded code in a form very close to normal Ada source.
7072 This is very useful in understanding the implications of various Ada
7073 usage on the efficiency of the generated code. There are many cases in
7074 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7075 generate a lot of run-time code. By using @option{-gnatG} you can identify
7076 these cases, and consider whether it may be desirable to modify the coding
7077 approach to improve efficiency.
7079 The optional parameter @code{nn} if present after -gnatG specifies an
7080 alternative maximum line length that overrides the normal default of 72.
7081 This value is in the range 40-999999, values less than 40 being silently
7082 reset to 40. The equal sign is optional.
7084 The format of the output is very similar to standard Ada source, and is
7085 easily understood by an Ada programmer. The following special syntactic
7086 additions correspond to low level features used in the generated code that
7087 do not have any exact analogies in pure Ada source form. The following
7088 is a partial list of these special constructions. See the spec
7089 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7091 If the switch @option{-gnatL} is used in conjunction with
7092 @cindex @option{-gnatL} (@command{gcc})
7093 @option{-gnatG}, then the original source lines are interspersed
7094 in the expanded source (as comment lines with the original line number).
7097 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7098 Shows the storage pool being used for an allocator.
7100 @item at end @var{procedure-name};
7101 Shows the finalization (cleanup) procedure for a scope.
7103 @item (if @var{expr} then @var{expr} else @var{expr})
7104 Conditional expression equivalent to the @code{x?y:z} construction in C.
7106 @item @var{target}^^^(@var{source})
7107 A conversion with floating-point truncation instead of rounding.
7109 @item @var{target}?(@var{source})
7110 A conversion that bypasses normal Ada semantic checking. In particular
7111 enumeration types and fixed-point types are treated simply as integers.
7113 @item @var{target}?^^^(@var{source})
7114 Combines the above two cases.
7116 @item @var{x} #/ @var{y}
7117 @itemx @var{x} #mod @var{y}
7118 @itemx @var{x} #* @var{y}
7119 @itemx @var{x} #rem @var{y}
7120 A division or multiplication of fixed-point values which are treated as
7121 integers without any kind of scaling.
7123 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7124 Shows the storage pool associated with a @code{free} statement.
7126 @item [subtype or type declaration]
7127 Used to list an equivalent declaration for an internally generated
7128 type that is referenced elsewhere in the listing.
7130 @item freeze @var{type-name} @ovar{actions}
7131 Shows the point at which @var{type-name} is frozen, with possible
7132 associated actions to be performed at the freeze point.
7134 @item reference @var{itype}
7135 Reference (and hence definition) to internal type @var{itype}.
7137 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7138 Intrinsic function call.
7140 @item @var{label-name} : label
7141 Declaration of label @var{labelname}.
7143 @item #$ @var{subprogram-name}
7144 An implicit call to a run-time support routine
7145 (to meet the requirement of H.3.1(9) in a
7148 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7149 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7150 @var{expr}, but handled more efficiently).
7152 @item [constraint_error]
7153 Raise the @code{Constraint_Error} exception.
7155 @item @var{expression}'reference
7156 A pointer to the result of evaluating @var{expression}.
7158 @item @var{target-type}!(@var{source-expression})
7159 An unchecked conversion of @var{source-expression} to @var{target-type}.
7161 @item [@var{numerator}/@var{denominator}]
7162 Used to represent internal real literals (that) have no exact
7163 representation in base 2-16 (for example, the result of compile time
7164 evaluation of the expression 1.0/27.0).
7168 @cindex @option{-gnatD} (@command{gcc})
7169 When used in conjunction with @option{-gnatG}, this switch causes
7170 the expanded source, as described above for
7171 @option{-gnatG} to be written to files with names
7172 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7173 instead of to the standard output file. For
7174 example, if the source file name is @file{hello.adb}, then a file
7175 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7176 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7177 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7178 you to do source level debugging using the generated code which is
7179 sometimes useful for complex code, for example to find out exactly
7180 which part of a complex construction raised an exception. This switch
7181 also suppress generation of cross-reference information (see
7182 @option{-gnatx}) since otherwise the cross-reference information
7183 would refer to the @file{^.dg^.DG^} file, which would cause
7184 confusion since this is not the original source file.
7186 Note that @option{-gnatD} actually implies @option{-gnatG}
7187 automatically, so it is not necessary to give both options.
7188 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7190 If the switch @option{-gnatL} is used in conjunction with
7191 @cindex @option{-gnatL} (@command{gcc})
7192 @option{-gnatDG}, then the original source lines are interspersed
7193 in the expanded source (as comment lines with the original line number).
7195 The optional parameter @code{nn} if present after -gnatD specifies an
7196 alternative maximum line length that overrides the normal default of 72.
7197 This value is in the range 40-999999, values less than 40 being silently
7198 reset to 40. The equal sign is optional.
7201 @cindex @option{-gnatr} (@command{gcc})
7202 @cindex pragma Restrictions
7203 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7204 so that violation of restrictions causes warnings rather than illegalities.
7205 This is useful during the development process when new restrictions are added
7206 or investigated. The switch also causes pragma Profile to be treated as
7207 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7208 restriction warnings rather than restrictions.
7211 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7212 @cindex @option{-gnatR} (@command{gcc})
7213 This switch controls output from the compiler of a listing showing
7214 representation information for declared types and objects. For
7215 @option{-gnatR0}, no information is output (equivalent to omitting
7216 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7217 so @option{-gnatR} with no parameter has the same effect), size and alignment
7218 information is listed for declared array and record types. For
7219 @option{-gnatR2}, size and alignment information is listed for all
7220 declared types and objects. Finally @option{-gnatR3} includes symbolic
7221 expressions for values that are computed at run time for
7222 variant records. These symbolic expressions have a mostly obvious
7223 format with #n being used to represent the value of the n'th
7224 discriminant. See source files @file{repinfo.ads/adb} in the
7225 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7226 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7227 the output is to a file with the name @file{^file.rep^file_REP^} where
7228 file is the name of the corresponding source file.
7231 @item /REPRESENTATION_INFO
7232 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7233 This qualifier controls output from the compiler of a listing showing
7234 representation information for declared types and objects. For
7235 @option{/REPRESENTATION_INFO=NONE}, no information is output
7236 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7237 @option{/REPRESENTATION_INFO} without option is equivalent to
7238 @option{/REPRESENTATION_INFO=ARRAYS}.
7239 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7240 information is listed for declared array and record types. For
7241 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7242 is listed for all expression information for values that are computed
7243 at run time for variant records. These symbolic expressions have a mostly
7244 obvious format with #n being used to represent the value of the n'th
7245 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7246 @code{GNAT} sources for full details on the format of
7247 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7248 If _FILE is added at the end of an option
7249 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7250 then the output is to a file with the name @file{file_REP} where
7251 file is the name of the corresponding source file.
7253 Note that it is possible for record components to have zero size. In
7254 this case, the component clause uses an obvious extension of permitted
7255 Ada syntax, for example @code{at 0 range 0 .. -1}.
7257 Representation information requires that code be generated (since it is the
7258 code generator that lays out complex data structures). If an attempt is made
7259 to output representation information when no code is generated, for example
7260 when a subunit is compiled on its own, then no information can be generated
7261 and the compiler outputs a message to this effect.
7264 @cindex @option{-gnatS} (@command{gcc})
7265 The use of the switch @option{-gnatS} for an
7266 Ada compilation will cause the compiler to output a
7267 representation of package Standard in a form very
7268 close to standard Ada. It is not quite possible to
7269 do this entirely in standard Ada (since new
7270 numeric base types cannot be created in standard
7271 Ada), but the output is easily
7272 readable to any Ada programmer, and is useful to
7273 determine the characteristics of target dependent
7274 types in package Standard.
7277 @cindex @option{-gnatx} (@command{gcc})
7278 Normally the compiler generates full cross-referencing information in
7279 the @file{ALI} file. This information is used by a number of tools,
7280 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7281 suppresses this information. This saves some space and may slightly
7282 speed up compilation, but means that these tools cannot be used.
7285 @node Exception Handling Control
7286 @subsection Exception Handling Control
7289 GNAT uses two methods for handling exceptions at run-time. The
7290 @code{setjmp/longjmp} method saves the context when entering
7291 a frame with an exception handler. Then when an exception is
7292 raised, the context can be restored immediately, without the
7293 need for tracing stack frames. This method provides very fast
7294 exception propagation, but introduces significant overhead for
7295 the use of exception handlers, even if no exception is raised.
7297 The other approach is called ``zero cost'' exception handling.
7298 With this method, the compiler builds static tables to describe
7299 the exception ranges. No dynamic code is required when entering
7300 a frame containing an exception handler. When an exception is
7301 raised, the tables are used to control a back trace of the
7302 subprogram invocation stack to locate the required exception
7303 handler. This method has considerably poorer performance for
7304 the propagation of exceptions, but there is no overhead for
7305 exception handlers if no exception is raised. Note that in this
7306 mode and in the context of mixed Ada and C/C++ programming,
7307 to propagate an exception through a C/C++ code, the C/C++ code
7308 must be compiled with the @option{-funwind-tables} GCC's
7311 The following switches may be used to control which of the
7312 two exception handling methods is used.
7318 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7319 This switch causes the setjmp/longjmp run-time (when available) to be used
7320 for exception handling. If the default
7321 mechanism for the target is zero cost exceptions, then
7322 this switch can be used to modify this default, and must be
7323 used for all units in the partition.
7324 This option is rarely used. One case in which it may be
7325 advantageous is if you have an application where exception
7326 raising is common and the overall performance of the
7327 application is improved by favoring exception propagation.
7330 @cindex @option{--RTS=zcx} (@command{gnatmake})
7331 @cindex Zero Cost Exceptions
7332 This switch causes the zero cost approach to be used
7333 for exception handling. If this is the default mechanism for the
7334 target (see below), then this switch is unneeded. If the default
7335 mechanism for the target is setjmp/longjmp exceptions, then
7336 this switch can be used to modify this default, and must be
7337 used for all units in the partition.
7338 This option can only be used if the zero cost approach
7339 is available for the target in use, otherwise it will generate an error.
7343 The same option @option{--RTS} must be used both for @command{gcc}
7344 and @command{gnatbind}. Passing this option to @command{gnatmake}
7345 (@pxref{Switches for gnatmake}) will ensure the required consistency
7346 through the compilation and binding steps.
7348 @node Units to Sources Mapping Files
7349 @subsection Units to Sources Mapping Files
7353 @item -gnatem^^=^@var{path}
7354 @cindex @option{-gnatem} (@command{gcc})
7355 A mapping file is a way to communicate to the compiler two mappings:
7356 from unit names to file names (without any directory information) and from
7357 file names to path names (with full directory information). These mappings
7358 are used by the compiler to short-circuit the path search.
7360 The use of mapping files is not required for correct operation of the
7361 compiler, but mapping files can improve efficiency, particularly when
7362 sources are read over a slow network connection. In normal operation,
7363 you need not be concerned with the format or use of mapping files,
7364 and the @option{-gnatem} switch is not a switch that you would use
7365 explicitly. it is intended only for use by automatic tools such as
7366 @command{gnatmake} running under the project file facility. The
7367 description here of the format of mapping files is provided
7368 for completeness and for possible use by other tools.
7370 A mapping file is a sequence of sets of three lines. In each set,
7371 the first line is the unit name, in lower case, with ``@code{%s}''
7373 specs and ``@code{%b}'' appended for bodies; the second line is the
7374 file name; and the third line is the path name.
7380 /gnat/project1/sources/main.2.ada
7383 When the switch @option{-gnatem} is specified, the compiler will create
7384 in memory the two mappings from the specified file. If there is any problem
7385 (nonexistent file, truncated file or duplicate entries), no mapping will
7388 Several @option{-gnatem} switches may be specified; however, only the last
7389 one on the command line will be taken into account.
7391 When using a project file, @command{gnatmake} create a temporary mapping file
7392 and communicates it to the compiler using this switch.
7396 @node Integrated Preprocessing
7397 @subsection Integrated Preprocessing
7400 GNAT sources may be preprocessed immediately before compilation.
7401 In this case, the actual
7402 text of the source is not the text of the source file, but is derived from it
7403 through a process called preprocessing. Integrated preprocessing is specified
7404 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7405 indicates, through a text file, the preprocessing data to be used.
7406 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7409 Note that when integrated preprocessing is used, the output from the
7410 preprocessor is not written to any external file. Instead it is passed
7411 internally to the compiler. If you need to preserve the result of
7412 preprocessing in a file, then you should use @command{gnatprep}
7413 to perform the desired preprocessing in stand-alone mode.
7416 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7417 used when Integrated Preprocessing is used. The reason is that preprocessing
7418 with another Preprocessing Data file without changing the sources will
7419 not trigger recompilation without this switch.
7422 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7423 always trigger recompilation for sources that are preprocessed,
7424 because @command{gnatmake} cannot compute the checksum of the source after
7428 The actual preprocessing function is described in details in section
7429 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7430 preprocessing is triggered and parameterized.
7434 @item -gnatep=@var{file}
7435 @cindex @option{-gnatep} (@command{gcc})
7436 This switch indicates to the compiler the file name (without directory
7437 information) of the preprocessor data file to use. The preprocessor data file
7438 should be found in the source directories.
7441 A preprocessing data file is a text file with significant lines indicating
7442 how should be preprocessed either a specific source or all sources not
7443 mentioned in other lines. A significant line is a nonempty, non-comment line.
7444 Comments are similar to Ada comments.
7447 Each significant line starts with either a literal string or the character '*'.
7448 A literal string is the file name (without directory information) of the source
7449 to preprocess. A character '*' indicates the preprocessing for all the sources
7450 that are not specified explicitly on other lines (order of the lines is not
7451 significant). It is an error to have two lines with the same file name or two
7452 lines starting with the character '*'.
7455 After the file name or the character '*', another optional literal string
7456 indicating the file name of the definition file to be used for preprocessing
7457 (@pxref{Form of Definitions File}). The definition files are found by the
7458 compiler in one of the source directories. In some cases, when compiling
7459 a source in a directory other than the current directory, if the definition
7460 file is in the current directory, it may be necessary to add the current
7461 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7462 the compiler would not find the definition file.
7465 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7466 be found. Those ^switches^switches^ are:
7471 Causes both preprocessor lines and the lines deleted by
7472 preprocessing to be replaced by blank lines, preserving the line number.
7473 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7474 it cancels the effect of @option{-c}.
7477 Causes both preprocessor lines and the lines deleted
7478 by preprocessing to be retained as comments marked
7479 with the special string ``@code{--! }''.
7481 @item -Dsymbol=value
7482 Define or redefine a symbol, associated with value. A symbol is an Ada
7483 identifier, or an Ada reserved word, with the exception of @code{if},
7484 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7485 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7486 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7487 same name defined in a definition file.
7490 Causes a sorted list of symbol names and values to be
7491 listed on the standard output file.
7494 Causes undefined symbols to be treated as having the value @code{FALSE}
7496 of a preprocessor test. In the absence of this option, an undefined symbol in
7497 a @code{#if} or @code{#elsif} test will be treated as an error.
7502 Examples of valid lines in a preprocessor data file:
7505 "toto.adb" "prep.def" -u
7506 -- preprocess "toto.adb", using definition file "prep.def",
7507 -- undefined symbol are False.
7510 -- preprocess all other sources without a definition file;
7511 -- suppressed lined are commented; symbol VERSION has the value V101.
7513 "titi.adb" "prep2.def" -s
7514 -- preprocess "titi.adb", using definition file "prep2.def";
7515 -- list all symbols with their values.
7518 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7519 @cindex @option{-gnateD} (@command{gcc})
7520 Define or redefine a preprocessing symbol, associated with value. If no value
7521 is given on the command line, then the value of the symbol is @code{True}.
7522 A symbol is an identifier, following normal Ada (case-insensitive)
7523 rules for its syntax, and value is any sequence (including an empty sequence)
7524 of characters from the set (letters, digits, period, underline).
7525 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7526 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7529 A symbol declared with this ^switch^switch^ on the command line replaces a
7530 symbol with the same name either in a definition file or specified with a
7531 ^switch^switch^ -D in the preprocessor data file.
7534 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7537 When integrated preprocessing is performed and the preprocessor modifies
7538 the source text, write the result of this preprocessing into a file
7539 <source>^.prep^_prep^.
7543 @node Code Generation Control
7544 @subsection Code Generation Control
7548 The GCC technology provides a wide range of target dependent
7549 @option{-m} switches for controlling
7550 details of code generation with respect to different versions of
7551 architectures. This includes variations in instruction sets (e.g.@:
7552 different members of the power pc family), and different requirements
7553 for optimal arrangement of instructions (e.g.@: different members of
7554 the x86 family). The list of available @option{-m} switches may be
7555 found in the GCC documentation.
7557 Use of these @option{-m} switches may in some cases result in improved
7560 The GNAT Pro technology is tested and qualified without any
7561 @option{-m} switches,
7562 so generally the most reliable approach is to avoid the use of these
7563 switches. However, we generally expect most of these switches to work
7564 successfully with GNAT Pro, and many customers have reported successful
7565 use of these options.
7567 Our general advice is to avoid the use of @option{-m} switches unless
7568 special needs lead to requirements in this area. In particular,
7569 there is no point in using @option{-m} switches to improve performance
7570 unless you actually see a performance improvement.
7574 @subsection Return Codes
7575 @cindex Return Codes
7576 @cindex @option{/RETURN_CODES=VMS}
7579 On VMS, GNAT compiled programs return POSIX-style codes by default,
7580 e.g.@: @option{/RETURN_CODES=POSIX}.
7582 To enable VMS style return codes, use GNAT BIND and LINK with the option
7583 @option{/RETURN_CODES=VMS}. For example:
7586 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7587 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7591 Programs built with /RETURN_CODES=VMS are suitable to be called in
7592 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7593 are suitable for spawning with appropriate GNAT RTL routines.
7597 @node Search Paths and the Run-Time Library (RTL)
7598 @section Search Paths and the Run-Time Library (RTL)
7601 With the GNAT source-based library system, the compiler must be able to
7602 find source files for units that are needed by the unit being compiled.
7603 Search paths are used to guide this process.
7605 The compiler compiles one source file whose name must be given
7606 explicitly on the command line. In other words, no searching is done
7607 for this file. To find all other source files that are needed (the most
7608 common being the specs of units), the compiler examines the following
7609 directories, in the following order:
7613 The directory containing the source file of the main unit being compiled
7614 (the file name on the command line).
7617 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7618 @command{gcc} command line, in the order given.
7621 @findex ADA_PRJ_INCLUDE_FILE
7622 Each of the directories listed in the text file whose name is given
7623 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7626 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7627 driver when project files are used. It should not normally be set
7631 @findex ADA_INCLUDE_PATH
7632 Each of the directories listed in the value of the
7633 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7635 Construct this value
7636 exactly as the @env{PATH} environment variable: a list of directory
7637 names separated by colons (semicolons when working with the NT version).
7640 Normally, define this value as a logical name containing a comma separated
7641 list of directory names.
7643 This variable can also be defined by means of an environment string
7644 (an argument to the HP C exec* set of functions).
7648 DEFINE ANOTHER_PATH FOO:[BAG]
7649 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7652 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7653 first, followed by the standard Ada
7654 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7655 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7656 (Text_IO, Sequential_IO, etc)
7657 instead of the standard Ada packages. Thus, in order to get the standard Ada
7658 packages by default, ADA_INCLUDE_PATH must be redefined.
7662 The content of the @file{ada_source_path} file which is part of the GNAT
7663 installation tree and is used to store standard libraries such as the
7664 GNAT Run Time Library (RTL) source files.
7666 @ref{Installing a library}
7671 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7672 inhibits the use of the directory
7673 containing the source file named in the command line. You can still
7674 have this directory on your search path, but in this case it must be
7675 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7677 Specifying the switch @option{-nostdinc}
7678 inhibits the search of the default location for the GNAT Run Time
7679 Library (RTL) source files.
7681 The compiler outputs its object files and ALI files in the current
7684 Caution: The object file can be redirected with the @option{-o} switch;
7685 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7686 so the @file{ALI} file will not go to the right place. Therefore, you should
7687 avoid using the @option{-o} switch.
7691 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7692 children make up the GNAT RTL, together with the simple @code{System.IO}
7693 package used in the @code{"Hello World"} example. The sources for these units
7694 are needed by the compiler and are kept together in one directory. Not
7695 all of the bodies are needed, but all of the sources are kept together
7696 anyway. In a normal installation, you need not specify these directory
7697 names when compiling or binding. Either the environment variables or
7698 the built-in defaults cause these files to be found.
7700 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7701 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7702 consisting of child units of @code{GNAT}. This is a collection of generally
7703 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7704 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7706 Besides simplifying access to the RTL, a major use of search paths is
7707 in compiling sources from multiple directories. This can make
7708 development environments much more flexible.
7710 @node Order of Compilation Issues
7711 @section Order of Compilation Issues
7714 If, in our earlier example, there was a spec for the @code{hello}
7715 procedure, it would be contained in the file @file{hello.ads}; yet this
7716 file would not have to be explicitly compiled. This is the result of the
7717 model we chose to implement library management. Some of the consequences
7718 of this model are as follows:
7722 There is no point in compiling specs (except for package
7723 specs with no bodies) because these are compiled as needed by clients. If
7724 you attempt a useless compilation, you will receive an error message.
7725 It is also useless to compile subunits because they are compiled as needed
7729 There are no order of compilation requirements: performing a
7730 compilation never obsoletes anything. The only way you can obsolete
7731 something and require recompilations is to modify one of the
7732 source files on which it depends.
7735 There is no library as such, apart from the ALI files
7736 (@pxref{The Ada Library Information Files}, for information on the format
7737 of these files). For now we find it convenient to create separate ALI files,
7738 but eventually the information therein may be incorporated into the object
7742 When you compile a unit, the source files for the specs of all units
7743 that it @code{with}'s, all its subunits, and the bodies of any generics it
7744 instantiates must be available (reachable by the search-paths mechanism
7745 described above), or you will receive a fatal error message.
7752 The following are some typical Ada compilation command line examples:
7755 @item $ gcc -c xyz.adb
7756 Compile body in file @file{xyz.adb} with all default options.
7759 @item $ gcc -c -O2 -gnata xyz-def.adb
7762 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7765 Compile the child unit package in file @file{xyz-def.adb} with extensive
7766 optimizations, and pragma @code{Assert}/@code{Debug} statements
7769 @item $ gcc -c -gnatc abc-def.adb
7770 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7774 @node Binding Using gnatbind
7775 @chapter Binding Using @code{gnatbind}
7779 * Running gnatbind::
7780 * Switches for gnatbind::
7781 * Command-Line Access::
7782 * Search Paths for gnatbind::
7783 * Examples of gnatbind Usage::
7787 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7788 to bind compiled GNAT objects.
7790 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7791 driver (see @ref{The GNAT Driver and Project Files}).
7793 The @code{gnatbind} program performs four separate functions:
7797 Checks that a program is consistent, in accordance with the rules in
7798 Chapter 10 of the Ada Reference Manual. In particular, error
7799 messages are generated if a program uses inconsistent versions of a
7803 Checks that an acceptable order of elaboration exists for the program
7804 and issues an error message if it cannot find an order of elaboration
7805 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7808 Generates a main program incorporating the given elaboration order.
7809 This program is a small Ada package (body and spec) that
7810 must be subsequently compiled
7811 using the GNAT compiler. The necessary compilation step is usually
7812 performed automatically by @command{gnatlink}. The two most important
7813 functions of this program
7814 are to call the elaboration routines of units in an appropriate order
7815 and to call the main program.
7818 Determines the set of object files required by the given main program.
7819 This information is output in the forms of comments in the generated program,
7820 to be read by the @command{gnatlink} utility used to link the Ada application.
7823 @node Running gnatbind
7824 @section Running @code{gnatbind}
7827 The form of the @code{gnatbind} command is
7830 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7834 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7835 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7836 package in two files whose names are
7837 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7838 For example, if given the
7839 parameter @file{hello.ali}, for a main program contained in file
7840 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7841 and @file{b~hello.adb}.
7843 When doing consistency checking, the binder takes into consideration
7844 any source files it can locate. For example, if the binder determines
7845 that the given main program requires the package @code{Pack}, whose
7847 file is @file{pack.ali} and whose corresponding source spec file is
7848 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7849 (using the same search path conventions as previously described for the
7850 @command{gcc} command). If it can locate this source file, it checks that
7852 or source checksums of the source and its references to in @file{ALI} files
7853 match. In other words, any @file{ALI} files that mentions this spec must have
7854 resulted from compiling this version of the source file (or in the case
7855 where the source checksums match, a version close enough that the
7856 difference does not matter).
7858 @cindex Source files, use by binder
7859 The effect of this consistency checking, which includes source files, is
7860 that the binder ensures that the program is consistent with the latest
7861 version of the source files that can be located at bind time. Editing a
7862 source file without compiling files that depend on the source file cause
7863 error messages to be generated by the binder.
7865 For example, suppose you have a main program @file{hello.adb} and a
7866 package @code{P}, from file @file{p.ads} and you perform the following
7871 Enter @code{gcc -c hello.adb} to compile the main program.
7874 Enter @code{gcc -c p.ads} to compile package @code{P}.
7877 Edit file @file{p.ads}.
7880 Enter @code{gnatbind hello}.
7884 At this point, the file @file{p.ali} contains an out-of-date time stamp
7885 because the file @file{p.ads} has been edited. The attempt at binding
7886 fails, and the binder generates the following error messages:
7889 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7890 error: "p.ads" has been modified and must be recompiled
7894 Now both files must be recompiled as indicated, and then the bind can
7895 succeed, generating a main program. You need not normally be concerned
7896 with the contents of this file, but for reference purposes a sample
7897 binder output file is given in @ref{Example of Binder Output File}.
7899 In most normal usage, the default mode of @command{gnatbind} which is to
7900 generate the main package in Ada, as described in the previous section.
7901 In particular, this means that any Ada programmer can read and understand
7902 the generated main program. It can also be debugged just like any other
7903 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7904 @command{gnatbind} and @command{gnatlink}.
7906 However for some purposes it may be convenient to generate the main
7907 program in C rather than Ada. This may for example be helpful when you
7908 are generating a mixed language program with the main program in C. The
7909 GNAT compiler itself is an example.
7910 The use of the @option{^-C^/BIND_FILE=C^} switch
7911 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7912 be generated in C (and compiled using the gnu C compiler).
7914 @node Switches for gnatbind
7915 @section Switches for @command{gnatbind}
7918 The following switches are available with @code{gnatbind}; details will
7919 be presented in subsequent sections.
7922 * Consistency-Checking Modes::
7923 * Binder Error Message Control::
7924 * Elaboration Control::
7926 * Binding with Non-Ada Main Programs::
7927 * Binding Programs with No Main Subprogram::
7934 @cindex @option{--version} @command{gnatbind}
7935 Display Copyright and version, then exit disregarding all other options.
7938 @cindex @option{--help} @command{gnatbind}
7939 If @option{--version} was not used, display usage, then exit disregarding
7943 @cindex @option{-a} @command{gnatbind}
7944 Indicates that, if supported by the platform, the adainit procedure should
7945 be treated as an initialisation routine by the linker (a constructor). This
7946 is intended to be used by the Project Manager to automatically initialize
7947 shared Stand-Alone Libraries.
7949 @item ^-aO^/OBJECT_SEARCH^
7950 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7951 Specify directory to be searched for ALI files.
7953 @item ^-aI^/SOURCE_SEARCH^
7954 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7955 Specify directory to be searched for source file.
7957 @item ^-A^/BIND_FILE=ADA^
7958 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7959 Generate binder program in Ada (default)
7961 @item ^-b^/REPORT_ERRORS=BRIEF^
7962 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7963 Generate brief messages to @file{stderr} even if verbose mode set.
7965 @item ^-c^/NOOUTPUT^
7966 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7967 Check only, no generation of binder output file.
7969 @item ^-C^/BIND_FILE=C^
7970 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7971 Generate binder program in C
7973 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7974 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7975 This switch can be used to change the default task stack size value
7976 to a specified size @var{nn}, which is expressed in bytes by default, or
7977 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7979 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7980 in effect, to completing all task specs with
7981 @smallexample @c ada
7982 pragma Storage_Size (nn);
7984 When they do not already have such a pragma.
7986 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7987 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7988 This switch can be used to change the default secondary stack size value
7989 to a specified size @var{nn}, which is expressed in bytes by default, or
7990 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7993 The secondary stack is used to deal with functions that return a variable
7994 sized result, for example a function returning an unconstrained
7995 String. There are two ways in which this secondary stack is allocated.
7997 For most targets, the secondary stack is growing on demand and is allocated
7998 as a chain of blocks in the heap. The -D option is not very
7999 relevant. It only give some control over the size of the allocated
8000 blocks (whose size is the minimum of the default secondary stack size value,
8001 and the actual size needed for the current allocation request).
8003 For certain targets, notably VxWorks 653,
8004 the secondary stack is allocated by carving off a fixed ratio chunk of the
8005 primary task stack. The -D option is used to define the
8006 size of the environment task's secondary stack.
8008 @item ^-e^/ELABORATION_DEPENDENCIES^
8009 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8010 Output complete list of elaboration-order dependencies.
8012 @item ^-E^/STORE_TRACEBACKS^
8013 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8014 Store tracebacks in exception occurrences when the target supports it.
8015 This is the default with the zero cost exception mechanism.
8017 @c The following may get moved to an appendix
8018 This option is currently supported on the following targets:
8019 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8021 See also the packages @code{GNAT.Traceback} and
8022 @code{GNAT.Traceback.Symbolic} for more information.
8024 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8025 @command{gcc} option.
8028 @item ^-F^/FORCE_ELABS_FLAGS^
8029 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8030 Force the checks of elaboration flags. @command{gnatbind} does not normally
8031 generate checks of elaboration flags for the main executable, except when
8032 a Stand-Alone Library is used. However, there are cases when this cannot be
8033 detected by gnatbind. An example is importing an interface of a Stand-Alone
8034 Library through a pragma Import and only specifying through a linker switch
8035 this Stand-Alone Library. This switch is used to guarantee that elaboration
8036 flag checks are generated.
8039 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8040 Output usage (help) information
8043 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8044 Specify directory to be searched for source and ALI files.
8046 @item ^-I-^/NOCURRENT_DIRECTORY^
8047 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8048 Do not look for sources in the current directory where @code{gnatbind} was
8049 invoked, and do not look for ALI files in the directory containing the
8050 ALI file named in the @code{gnatbind} command line.
8052 @item ^-l^/ORDER_OF_ELABORATION^
8053 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8054 Output chosen elaboration order.
8056 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8057 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8058 Bind the units for library building. In this case the adainit and
8059 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8060 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8061 ^@var{xxx}final^@var{XXX}FINAL^.
8062 Implies ^-n^/NOCOMPILE^.
8064 (@xref{GNAT and Libraries}, for more details.)
8067 On OpenVMS, these init and final procedures are exported in uppercase
8068 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8069 the init procedure will be "TOTOINIT" and the exported name of the final
8070 procedure will be "TOTOFINAL".
8073 @item ^-Mxyz^/RENAME_MAIN=xyz^
8074 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8075 Rename generated main program from main to xyz. This option is
8076 supported on cross environments only.
8078 @item ^-m^/ERROR_LIMIT=^@var{n}
8079 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8080 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8081 in the range 1..999999. The default value if no switch is
8082 given is 9999. If the number of warnings reaches this limit, then a
8083 message is output and further warnings are suppressed, the bind
8084 continues in this case. If the number of errors reaches this
8085 limit, then a message is output and the bind is abandoned.
8086 A value of zero means that no limit is enforced. The equal
8090 Furthermore, under Windows, the sources pointed to by the libraries path
8091 set in the registry are not searched for.
8095 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8099 @cindex @option{-nostdinc} (@command{gnatbind})
8100 Do not look for sources in the system default directory.
8103 @cindex @option{-nostdlib} (@command{gnatbind})
8104 Do not look for library files in the system default directory.
8106 @item --RTS=@var{rts-path}
8107 @cindex @option{--RTS} (@code{gnatbind})
8108 Specifies the default location of the runtime library. Same meaning as the
8109 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8111 @item ^-o ^/OUTPUT=^@var{file}
8112 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8113 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8114 Note that if this option is used, then linking must be done manually,
8115 gnatlink cannot be used.
8117 @item ^-O^/OBJECT_LIST^
8118 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8121 @item ^-p^/PESSIMISTIC_ELABORATION^
8122 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8123 Pessimistic (worst-case) elaboration order
8126 @cindex @option{^-R^-R^} (@command{gnatbind})
8127 Output closure source list.
8129 @item ^-s^/READ_SOURCES=ALL^
8130 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8131 Require all source files to be present.
8133 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8134 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8135 Specifies the value to be used when detecting uninitialized scalar
8136 objects with pragma Initialize_Scalars.
8137 The @var{xxx} ^string specified with the switch^option^ may be either
8139 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8140 @item ``@option{^lo^LOW^}'' for the lowest possible value
8141 @item ``@option{^hi^HIGH^}'' for the highest possible value
8142 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8143 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8146 In addition, you can specify @option{-Sev} to indicate that the value is
8147 to be set at run time. In this case, the program will look for an environment
8148 @cindex GNAT_INIT_SCALARS
8149 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8150 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8151 If no environment variable is found, or if it does not have a valid value,
8152 then the default is @option{in} (invalid values).
8156 @cindex @option{-static} (@code{gnatbind})
8157 Link against a static GNAT run time.
8160 @cindex @option{-shared} (@code{gnatbind})
8161 Link against a shared GNAT run time when available.
8164 @item ^-t^/NOTIME_STAMP_CHECK^
8165 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8166 Tolerate time stamp and other consistency errors
8168 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8169 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8170 Set the time slice value to @var{n} milliseconds. If the system supports
8171 the specification of a specific time slice value, then the indicated value
8172 is used. If the system does not support specific time slice values, but
8173 does support some general notion of round-robin scheduling, then any
8174 nonzero value will activate round-robin scheduling.
8176 A value of zero is treated specially. It turns off time
8177 slicing, and in addition, indicates to the tasking run time that the
8178 semantics should match as closely as possible the Annex D
8179 requirements of the Ada RM, and in particular sets the default
8180 scheduling policy to @code{FIFO_Within_Priorities}.
8182 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8183 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8184 Enable dynamic stack usage, with @var{n} results stored and displayed
8185 at program termination. A result is generated when a task
8186 terminates. Results that can't be stored are displayed on the fly, at
8187 task termination. This option is currently not supported on Itanium
8188 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8190 @item ^-v^/REPORT_ERRORS=VERBOSE^
8191 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8192 Verbose mode. Write error messages, header, summary output to
8197 @cindex @option{-w} (@code{gnatbind})
8198 Warning mode (@var{x}=s/e for suppress/treat as error)
8202 @item /WARNINGS=NORMAL
8203 @cindex @option{/WARNINGS} (@code{gnatbind})
8204 Normal warnings mode. Warnings are issued but ignored
8206 @item /WARNINGS=SUPPRESS
8207 @cindex @option{/WARNINGS} (@code{gnatbind})
8208 All warning messages are suppressed
8210 @item /WARNINGS=ERROR
8211 @cindex @option{/WARNINGS} (@code{gnatbind})
8212 Warning messages are treated as fatal errors
8215 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8216 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8217 Override default wide character encoding for standard Text_IO files.
8219 @item ^-x^/READ_SOURCES=NONE^
8220 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8221 Exclude source files (check object consistency only).
8224 @item /READ_SOURCES=AVAILABLE
8225 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8226 Default mode, in which sources are checked for consistency only if
8230 @item ^-y^/ENABLE_LEAP_SECONDS^
8231 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8232 Enable leap seconds support in @code{Ada.Calendar} and its children.
8234 @item ^-z^/ZERO_MAIN^
8235 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8241 You may obtain this listing of switches by running @code{gnatbind} with
8245 @node Consistency-Checking Modes
8246 @subsection Consistency-Checking Modes
8249 As described earlier, by default @code{gnatbind} checks
8250 that object files are consistent with one another and are consistent
8251 with any source files it can locate. The following switches control binder
8256 @item ^-s^/READ_SOURCES=ALL^
8257 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8258 Require source files to be present. In this mode, the binder must be
8259 able to locate all source files that are referenced, in order to check
8260 their consistency. In normal mode, if a source file cannot be located it
8261 is simply ignored. If you specify this switch, a missing source
8264 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8265 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8266 Override default wide character encoding for standard Text_IO files.
8267 Normally the default wide character encoding method used for standard
8268 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8269 the main source input (see description of switch
8270 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8271 use of this switch for the binder (which has the same set of
8272 possible arguments) overrides this default as specified.
8274 @item ^-x^/READ_SOURCES=NONE^
8275 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8276 Exclude source files. In this mode, the binder only checks that ALI
8277 files are consistent with one another. Source files are not accessed.
8278 The binder runs faster in this mode, and there is still a guarantee that
8279 the resulting program is self-consistent.
8280 If a source file has been edited since it was last compiled, and you
8281 specify this switch, the binder will not detect that the object
8282 file is out of date with respect to the source file. Note that this is the
8283 mode that is automatically used by @command{gnatmake} because in this
8284 case the checking against sources has already been performed by
8285 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8288 @item /READ_SOURCES=AVAILABLE
8289 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8290 This is the default mode in which source files are checked if they are
8291 available, and ignored if they are not available.
8295 @node Binder Error Message Control
8296 @subsection Binder Error Message Control
8299 The following switches provide control over the generation of error
8300 messages from the binder:
8304 @item ^-v^/REPORT_ERRORS=VERBOSE^
8305 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8306 Verbose mode. In the normal mode, brief error messages are generated to
8307 @file{stderr}. If this switch is present, a header is written
8308 to @file{stdout} and any error messages are directed to @file{stdout}.
8309 All that is written to @file{stderr} is a brief summary message.
8311 @item ^-b^/REPORT_ERRORS=BRIEF^
8312 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8313 Generate brief error messages to @file{stderr} even if verbose mode is
8314 specified. This is relevant only when used with the
8315 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8319 @cindex @option{-m} (@code{gnatbind})
8320 Limits the number of error messages to @var{n}, a decimal integer in the
8321 range 1-999. The binder terminates immediately if this limit is reached.
8324 @cindex @option{-M} (@code{gnatbind})
8325 Renames the generated main program from @code{main} to @code{xxx}.
8326 This is useful in the case of some cross-building environments, where
8327 the actual main program is separate from the one generated
8331 @item ^-ws^/WARNINGS=SUPPRESS^
8332 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8334 Suppress all warning messages.
8336 @item ^-we^/WARNINGS=ERROR^
8337 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8338 Treat any warning messages as fatal errors.
8341 @item /WARNINGS=NORMAL
8342 Standard mode with warnings generated, but warnings do not get treated
8346 @item ^-t^/NOTIME_STAMP_CHECK^
8347 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8348 @cindex Time stamp checks, in binder
8349 @cindex Binder consistency checks
8350 @cindex Consistency checks, in binder
8351 The binder performs a number of consistency checks including:
8355 Check that time stamps of a given source unit are consistent
8357 Check that checksums of a given source unit are consistent
8359 Check that consistent versions of @code{GNAT} were used for compilation
8361 Check consistency of configuration pragmas as required
8365 Normally failure of such checks, in accordance with the consistency
8366 requirements of the Ada Reference Manual, causes error messages to be
8367 generated which abort the binder and prevent the output of a binder
8368 file and subsequent link to obtain an executable.
8370 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8371 into warnings, so that
8372 binding and linking can continue to completion even in the presence of such
8373 errors. The result may be a failed link (due to missing symbols), or a
8374 non-functional executable which has undefined semantics.
8375 @emph{This means that
8376 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8380 @node Elaboration Control
8381 @subsection Elaboration Control
8384 The following switches provide additional control over the elaboration
8385 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8388 @item ^-p^/PESSIMISTIC_ELABORATION^
8389 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8390 Normally the binder attempts to choose an elaboration order that is
8391 likely to minimize the likelihood of an elaboration order error resulting
8392 in raising a @code{Program_Error} exception. This switch reverses the
8393 action of the binder, and requests that it deliberately choose an order
8394 that is likely to maximize the likelihood of an elaboration error.
8395 This is useful in ensuring portability and avoiding dependence on
8396 accidental fortuitous elaboration ordering.
8398 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8400 elaboration checking is used (@option{-gnatE} switch used for compilation).
8401 This is because in the default static elaboration mode, all necessary
8402 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8403 These implicit pragmas are still respected by the binder in
8404 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8405 safe elaboration order is assured.
8408 @node Output Control
8409 @subsection Output Control
8412 The following switches allow additional control over the output
8413 generated by the binder.
8418 @item ^-A^/BIND_FILE=ADA^
8419 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8420 Generate binder program in Ada (default). The binder program is named
8421 @file{b~@var{mainprog}.adb} by default. This can be changed with
8422 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8424 @item ^-c^/NOOUTPUT^
8425 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8426 Check only. Do not generate the binder output file. In this mode the
8427 binder performs all error checks but does not generate an output file.
8429 @item ^-C^/BIND_FILE=C^
8430 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8431 Generate binder program in C. The binder program is named
8432 @file{b_@var{mainprog}.c}.
8433 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8436 @item ^-e^/ELABORATION_DEPENDENCIES^
8437 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8438 Output complete list of elaboration-order dependencies, showing the
8439 reason for each dependency. This output can be rather extensive but may
8440 be useful in diagnosing problems with elaboration order. The output is
8441 written to @file{stdout}.
8444 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8445 Output usage information. The output is written to @file{stdout}.
8447 @item ^-K^/LINKER_OPTION_LIST^
8448 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8449 Output linker options to @file{stdout}. Includes library search paths,
8450 contents of pragmas Ident and Linker_Options, and libraries added
8453 @item ^-l^/ORDER_OF_ELABORATION^
8454 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8455 Output chosen elaboration order. The output is written to @file{stdout}.
8457 @item ^-O^/OBJECT_LIST^
8458 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8459 Output full names of all the object files that must be linked to provide
8460 the Ada component of the program. The output is written to @file{stdout}.
8461 This list includes the files explicitly supplied and referenced by the user
8462 as well as implicitly referenced run-time unit files. The latter are
8463 omitted if the corresponding units reside in shared libraries. The
8464 directory names for the run-time units depend on the system configuration.
8466 @item ^-o ^/OUTPUT=^@var{file}
8467 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8468 Set name of output file to @var{file} instead of the normal
8469 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8470 binder generated body filename. In C mode you would normally give
8471 @var{file} an extension of @file{.c} because it will be a C source program.
8472 Note that if this option is used, then linking must be done manually.
8473 It is not possible to use gnatlink in this case, since it cannot locate
8476 @item ^-r^/RESTRICTION_LIST^
8477 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8478 Generate list of @code{pragma Restrictions} that could be applied to
8479 the current unit. This is useful for code audit purposes, and also may
8480 be used to improve code generation in some cases.
8484 @node Binding with Non-Ada Main Programs
8485 @subsection Binding with Non-Ada Main Programs
8488 In our description so far we have assumed that the main
8489 program is in Ada, and that the task of the binder is to generate a
8490 corresponding function @code{main} that invokes this Ada main
8491 program. GNAT also supports the building of executable programs where
8492 the main program is not in Ada, but some of the called routines are
8493 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8494 The following switch is used in this situation:
8498 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8499 No main program. The main program is not in Ada.
8503 In this case, most of the functions of the binder are still required,
8504 but instead of generating a main program, the binder generates a file
8505 containing the following callable routines:
8510 You must call this routine to initialize the Ada part of the program by
8511 calling the necessary elaboration routines. A call to @code{adainit} is
8512 required before the first call to an Ada subprogram.
8514 Note that it is assumed that the basic execution environment must be setup
8515 to be appropriate for Ada execution at the point where the first Ada
8516 subprogram is called. In particular, if the Ada code will do any
8517 floating-point operations, then the FPU must be setup in an appropriate
8518 manner. For the case of the x86, for example, full precision mode is
8519 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8520 that the FPU is in the right state.
8524 You must call this routine to perform any library-level finalization
8525 required by the Ada subprograms. A call to @code{adafinal} is required
8526 after the last call to an Ada subprogram, and before the program
8531 If the @option{^-n^/NOMAIN^} switch
8532 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8533 @cindex Binder, multiple input files
8534 is given, more than one ALI file may appear on
8535 the command line for @code{gnatbind}. The normal @dfn{closure}
8536 calculation is performed for each of the specified units. Calculating
8537 the closure means finding out the set of units involved by tracing
8538 @code{with} references. The reason it is necessary to be able to
8539 specify more than one ALI file is that a given program may invoke two or
8540 more quite separate groups of Ada units.
8542 The binder takes the name of its output file from the last specified ALI
8543 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8544 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8545 The output is an Ada unit in source form that can
8546 be compiled with GNAT unless the -C switch is used in which case the
8547 output is a C source file, which must be compiled using the C compiler.
8548 This compilation occurs automatically as part of the @command{gnatlink}
8551 Currently the GNAT run time requires a FPU using 80 bits mode
8552 precision. Under targets where this is not the default it is required to
8553 call GNAT.Float_Control.Reset before using floating point numbers (this
8554 include float computation, float input and output) in the Ada code. A
8555 side effect is that this could be the wrong mode for the foreign code
8556 where floating point computation could be broken after this call.
8558 @node Binding Programs with No Main Subprogram
8559 @subsection Binding Programs with No Main Subprogram
8562 It is possible to have an Ada program which does not have a main
8563 subprogram. This program will call the elaboration routines of all the
8564 packages, then the finalization routines.
8566 The following switch is used to bind programs organized in this manner:
8569 @item ^-z^/ZERO_MAIN^
8570 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8571 Normally the binder checks that the unit name given on the command line
8572 corresponds to a suitable main subprogram. When this switch is used,
8573 a list of ALI files can be given, and the execution of the program
8574 consists of elaboration of these units in an appropriate order. Note
8575 that the default wide character encoding method for standard Text_IO
8576 files is always set to Brackets if this switch is set (you can use
8578 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8581 @node Command-Line Access
8582 @section Command-Line Access
8585 The package @code{Ada.Command_Line} provides access to the command-line
8586 arguments and program name. In order for this interface to operate
8587 correctly, the two variables
8599 are declared in one of the GNAT library routines. These variables must
8600 be set from the actual @code{argc} and @code{argv} values passed to the
8601 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8602 generates the C main program to automatically set these variables.
8603 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8604 set these variables. If they are not set, the procedures in
8605 @code{Ada.Command_Line} will not be available, and any attempt to use
8606 them will raise @code{Constraint_Error}. If command line access is
8607 required, your main program must set @code{gnat_argc} and
8608 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8611 @node Search Paths for gnatbind
8612 @section Search Paths for @code{gnatbind}
8615 The binder takes the name of an ALI file as its argument and needs to
8616 locate source files as well as other ALI files to verify object consistency.
8618 For source files, it follows exactly the same search rules as @command{gcc}
8619 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8620 directories searched are:
8624 The directory containing the ALI file named in the command line, unless
8625 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8628 All directories specified by @option{^-I^/SEARCH^}
8629 switches on the @code{gnatbind}
8630 command line, in the order given.
8633 @findex ADA_PRJ_OBJECTS_FILE
8634 Each of the directories listed in the text file whose name is given
8635 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8638 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8639 driver when project files are used. It should not normally be set
8643 @findex ADA_OBJECTS_PATH
8644 Each of the directories listed in the value of the
8645 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8647 Construct this value
8648 exactly as the @env{PATH} environment variable: a list of directory
8649 names separated by colons (semicolons when working with the NT version
8653 Normally, define this value as a logical name containing a comma separated
8654 list of directory names.
8656 This variable can also be defined by means of an environment string
8657 (an argument to the HP C exec* set of functions).
8661 DEFINE ANOTHER_PATH FOO:[BAG]
8662 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8665 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8666 first, followed by the standard Ada
8667 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8668 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8669 (Text_IO, Sequential_IO, etc)
8670 instead of the standard Ada packages. Thus, in order to get the standard Ada
8671 packages by default, ADA_OBJECTS_PATH must be redefined.
8675 The content of the @file{ada_object_path} file which is part of the GNAT
8676 installation tree and is used to store standard libraries such as the
8677 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8680 @ref{Installing a library}
8685 In the binder the switch @option{^-I^/SEARCH^}
8686 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8687 is used to specify both source and
8688 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8689 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8690 instead if you want to specify
8691 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8692 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8693 if you want to specify library paths
8694 only. This means that for the binder
8695 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8696 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8697 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8698 The binder generates the bind file (a C language source file) in the
8699 current working directory.
8705 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8706 children make up the GNAT Run-Time Library, together with the package
8707 GNAT and its children, which contain a set of useful additional
8708 library functions provided by GNAT. The sources for these units are
8709 needed by the compiler and are kept together in one directory. The ALI
8710 files and object files generated by compiling the RTL are needed by the
8711 binder and the linker and are kept together in one directory, typically
8712 different from the directory containing the sources. In a normal
8713 installation, you need not specify these directory names when compiling
8714 or binding. Either the environment variables or the built-in defaults
8715 cause these files to be found.
8717 Besides simplifying access to the RTL, a major use of search paths is
8718 in compiling sources from multiple directories. This can make
8719 development environments much more flexible.
8721 @node Examples of gnatbind Usage
8722 @section Examples of @code{gnatbind} Usage
8725 This section contains a number of examples of using the GNAT binding
8726 utility @code{gnatbind}.
8729 @item gnatbind hello
8730 The main program @code{Hello} (source program in @file{hello.adb}) is
8731 bound using the standard switch settings. The generated main program is
8732 @file{b~hello.adb}. This is the normal, default use of the binder.
8735 @item gnatbind hello -o mainprog.adb
8738 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8740 The main program @code{Hello} (source program in @file{hello.adb}) is
8741 bound using the standard switch settings. The generated main program is
8742 @file{mainprog.adb} with the associated spec in
8743 @file{mainprog.ads}. Note that you must specify the body here not the
8744 spec, in the case where the output is in Ada. Note that if this option
8745 is used, then linking must be done manually, since gnatlink will not
8746 be able to find the generated file.
8749 @item gnatbind main -C -o mainprog.c -x
8752 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8754 The main program @code{Main} (source program in
8755 @file{main.adb}) is bound, excluding source files from the
8756 consistency checking, generating
8757 the file @file{mainprog.c}.
8760 @item gnatbind -x main_program -C -o mainprog.c
8761 This command is exactly the same as the previous example. Switches may
8762 appear anywhere in the command line, and single letter switches may be
8763 combined into a single switch.
8767 @item gnatbind -n math dbase -C -o ada-control.c
8770 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8772 The main program is in a language other than Ada, but calls to
8773 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8774 to @code{gnatbind} generates the file @file{ada-control.c} containing
8775 the @code{adainit} and @code{adafinal} routines to be called before and
8776 after accessing the Ada units.
8779 @c ------------------------------------
8780 @node Linking Using gnatlink
8781 @chapter Linking Using @command{gnatlink}
8782 @c ------------------------------------
8786 This chapter discusses @command{gnatlink}, a tool that links
8787 an Ada program and builds an executable file. This utility
8788 invokes the system linker ^(via the @command{gcc} command)^^
8789 with a correct list of object files and library references.
8790 @command{gnatlink} automatically determines the list of files and
8791 references for the Ada part of a program. It uses the binder file
8792 generated by the @command{gnatbind} to determine this list.
8794 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8795 driver (see @ref{The GNAT Driver and Project Files}).
8798 * Running gnatlink::
8799 * Switches for gnatlink::
8802 @node Running gnatlink
8803 @section Running @command{gnatlink}
8806 The form of the @command{gnatlink} command is
8809 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8810 @ovar{non-Ada objects} @ovar{linker options}
8814 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8816 or linker options) may be in any order, provided that no non-Ada object may
8817 be mistaken for a main @file{ALI} file.
8818 Any file name @file{F} without the @file{.ali}
8819 extension will be taken as the main @file{ALI} file if a file exists
8820 whose name is the concatenation of @file{F} and @file{.ali}.
8823 @file{@var{mainprog}.ali} references the ALI file of the main program.
8824 The @file{.ali} extension of this file can be omitted. From this
8825 reference, @command{gnatlink} locates the corresponding binder file
8826 @file{b~@var{mainprog}.adb} and, using the information in this file along
8827 with the list of non-Ada objects and linker options, constructs a
8828 linker command file to create the executable.
8830 The arguments other than the @command{gnatlink} switches and the main
8831 @file{ALI} file are passed to the linker uninterpreted.
8832 They typically include the names of
8833 object files for units written in other languages than Ada and any library
8834 references required to resolve references in any of these foreign language
8835 units, or in @code{Import} pragmas in any Ada units.
8837 @var{linker options} is an optional list of linker specific
8839 The default linker called by gnatlink is @command{gcc} which in
8840 turn calls the appropriate system linker.
8841 Standard options for the linker such as @option{-lmy_lib} or
8842 @option{-Ldir} can be added as is.
8843 For options that are not recognized by
8844 @command{gcc} as linker options, use the @command{gcc} switches
8845 @option{-Xlinker} or @option{-Wl,}.
8846 Refer to the GCC documentation for
8847 details. Here is an example showing how to generate a linker map:
8850 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8853 Using @var{linker options} it is possible to set the program stack and
8856 See @ref{Setting Stack Size from gnatlink} and
8857 @ref{Setting Heap Size from gnatlink}.
8860 @command{gnatlink} determines the list of objects required by the Ada
8861 program and prepends them to the list of objects passed to the linker.
8862 @command{gnatlink} also gathers any arguments set by the use of
8863 @code{pragma Linker_Options} and adds them to the list of arguments
8864 presented to the linker.
8867 @command{gnatlink} accepts the following types of extra files on the command
8868 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8869 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8870 handled according to their extension.
8873 @node Switches for gnatlink
8874 @section Switches for @command{gnatlink}
8877 The following switches are available with the @command{gnatlink} utility:
8883 @cindex @option{--version} @command{gnatlink}
8884 Display Copyright and version, then exit disregarding all other options.
8887 @cindex @option{--help} @command{gnatlink}
8888 If @option{--version} was not used, display usage, then exit disregarding
8891 @item ^-A^/BIND_FILE=ADA^
8892 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8893 The binder has generated code in Ada. This is the default.
8895 @item ^-C^/BIND_FILE=C^
8896 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8897 If instead of generating a file in Ada, the binder has generated one in
8898 C, then the linker needs to know about it. Use this switch to signal
8899 to @command{gnatlink} that the binder has generated C code rather than
8902 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8903 @cindex Command line length
8904 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8905 On some targets, the command line length is limited, and @command{gnatlink}
8906 will generate a separate file for the linker if the list of object files
8908 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8909 to be generated even if
8910 the limit is not exceeded. This is useful in some cases to deal with
8911 special situations where the command line length is exceeded.
8914 @cindex Debugging information, including
8915 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8916 The option to include debugging information causes the Ada bind file (in
8917 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8918 @option{^-g^/DEBUG^}.
8919 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8920 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8921 Without @option{^-g^/DEBUG^}, the binder removes these files by
8922 default. The same procedure apply if a C bind file was generated using
8923 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8924 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8926 @item ^-n^/NOCOMPILE^
8927 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8928 Do not compile the file generated by the binder. This may be used when
8929 a link is rerun with different options, but there is no need to recompile
8933 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8934 Causes additional information to be output, including a full list of the
8935 included object files. This switch option is most useful when you want
8936 to see what set of object files are being used in the link step.
8938 @item ^-v -v^/VERBOSE/VERBOSE^
8939 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8940 Very verbose mode. Requests that the compiler operate in verbose mode when
8941 it compiles the binder file, and that the system linker run in verbose mode.
8943 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8944 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8945 @var{exec-name} specifies an alternate name for the generated
8946 executable program. If this switch is omitted, the executable has the same
8947 name as the main unit. For example, @code{gnatlink try.ali} creates
8948 an executable called @file{^try^TRY.EXE^}.
8951 @item -b @var{target}
8952 @cindex @option{-b} (@command{gnatlink})
8953 Compile your program to run on @var{target}, which is the name of a
8954 system configuration. You must have a GNAT cross-compiler built if
8955 @var{target} is not the same as your host system.
8958 @cindex @option{-B} (@command{gnatlink})
8959 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8960 from @var{dir} instead of the default location. Only use this switch
8961 when multiple versions of the GNAT compiler are available.
8962 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8963 for further details. You would normally use the @option{-b} or
8964 @option{-V} switch instead.
8966 @item --GCC=@var{compiler_name}
8967 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8968 Program used for compiling the binder file. The default is
8969 @command{gcc}. You need to use quotes around @var{compiler_name} if
8970 @code{compiler_name} contains spaces or other separator characters.
8971 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8972 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8973 inserted after your command name. Thus in the above example the compiler
8974 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8975 A limitation of this syntax is that the name and path name of the executable
8976 itself must not include any embedded spaces. If the compiler executable is
8977 different from the default one (gcc or <prefix>-gcc), then the back-end
8978 switches in the ALI file are not used to compile the binder generated source.
8979 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8980 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8981 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8982 is taken into account. However, all the additional switches are also taken
8984 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8985 @option{--GCC="bar -x -y -z -t"}.
8987 @item --LINK=@var{name}
8988 @cindex @option{--LINK=} (@command{gnatlink})
8989 @var{name} is the name of the linker to be invoked. This is especially
8990 useful in mixed language programs since languages such as C++ require
8991 their own linker to be used. When this switch is omitted, the default
8992 name for the linker is @command{gcc}. When this switch is used, the
8993 specified linker is called instead of @command{gcc} with exactly the same
8994 parameters that would have been passed to @command{gcc} so if the desired
8995 linker requires different parameters it is necessary to use a wrapper
8996 script that massages the parameters before invoking the real linker. It
8997 may be useful to control the exact invocation by using the verbose
9003 @item /DEBUG=TRACEBACK
9004 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9005 This qualifier causes sufficient information to be included in the
9006 executable file to allow a traceback, but does not include the full
9007 symbol information needed by the debugger.
9009 @item /IDENTIFICATION="<string>"
9010 @code{"<string>"} specifies the string to be stored in the image file
9011 identification field in the image header.
9012 It overrides any pragma @code{Ident} specified string.
9014 @item /NOINHIBIT-EXEC
9015 Generate the executable file even if there are linker warnings.
9017 @item /NOSTART_FILES
9018 Don't link in the object file containing the ``main'' transfer address.
9019 Used when linking with a foreign language main program compiled with an
9023 Prefer linking with object libraries over sharable images, even without
9029 @node The GNAT Make Program gnatmake
9030 @chapter The GNAT Make Program @command{gnatmake}
9034 * Running gnatmake::
9035 * Switches for gnatmake::
9036 * Mode Switches for gnatmake::
9037 * Notes on the Command Line::
9038 * How gnatmake Works::
9039 * Examples of gnatmake Usage::
9042 A typical development cycle when working on an Ada program consists of
9043 the following steps:
9047 Edit some sources to fix bugs.
9053 Compile all sources affected.
9063 The third step can be tricky, because not only do the modified files
9064 @cindex Dependency rules
9065 have to be compiled, but any files depending on these files must also be
9066 recompiled. The dependency rules in Ada can be quite complex, especially
9067 in the presence of overloading, @code{use} clauses, generics and inlined
9070 @command{gnatmake} automatically takes care of the third and fourth steps
9071 of this process. It determines which sources need to be compiled,
9072 compiles them, and binds and links the resulting object files.
9074 Unlike some other Ada make programs, the dependencies are always
9075 accurately recomputed from the new sources. The source based approach of
9076 the GNAT compilation model makes this possible. This means that if
9077 changes to the source program cause corresponding changes in
9078 dependencies, they will always be tracked exactly correctly by
9081 @node Running gnatmake
9082 @section Running @command{gnatmake}
9085 The usual form of the @command{gnatmake} command is
9088 $ gnatmake @ovar{switches} @var{file_name}
9089 @ovar{file_names} @ovar{mode_switches}
9093 The only required argument is one @var{file_name}, which specifies
9094 a compilation unit that is a main program. Several @var{file_names} can be
9095 specified: this will result in several executables being built.
9096 If @code{switches} are present, they can be placed before the first
9097 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9098 If @var{mode_switches} are present, they must always be placed after
9099 the last @var{file_name} and all @code{switches}.
9101 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9102 extension may be omitted from the @var{file_name} arguments. However, if
9103 you are using non-standard extensions, then it is required that the
9104 extension be given. A relative or absolute directory path can be
9105 specified in a @var{file_name}, in which case, the input source file will
9106 be searched for in the specified directory only. Otherwise, the input
9107 source file will first be searched in the directory where
9108 @command{gnatmake} was invoked and if it is not found, it will be search on
9109 the source path of the compiler as described in
9110 @ref{Search Paths and the Run-Time Library (RTL)}.
9112 All @command{gnatmake} output (except when you specify
9113 @option{^-M^/DEPENDENCIES_LIST^}) is to
9114 @file{stderr}. The output produced by the
9115 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9118 @node Switches for gnatmake
9119 @section Switches for @command{gnatmake}
9122 You may specify any of the following switches to @command{gnatmake}:
9128 @cindex @option{--version} @command{gnatmake}
9129 Display Copyright and version, then exit disregarding all other options.
9132 @cindex @option{--help} @command{gnatmake}
9133 If @option{--version} was not used, display usage, then exit disregarding
9137 @item --GCC=@var{compiler_name}
9138 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9139 Program used for compiling. The default is `@command{gcc}'. You need to use
9140 quotes around @var{compiler_name} if @code{compiler_name} contains
9141 spaces or other separator characters. As an example @option{--GCC="foo -x
9142 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9143 compiler. A limitation of this syntax is that the name and path name of
9144 the executable itself must not include any embedded spaces. Note that
9145 switch @option{-c} is always inserted after your command name. Thus in the
9146 above example the compiler command that will be used by @command{gnatmake}
9147 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9148 used, only the last @var{compiler_name} is taken into account. However,
9149 all the additional switches are also taken into account. Thus,
9150 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9151 @option{--GCC="bar -x -y -z -t"}.
9153 @item --GNATBIND=@var{binder_name}
9154 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9155 Program used for binding. The default is `@code{gnatbind}'. You need to
9156 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9157 or other separator characters. As an example @option{--GNATBIND="bar -x
9158 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9159 binder. Binder switches that are normally appended by @command{gnatmake}
9160 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9161 A limitation of this syntax is that the name and path name of the executable
9162 itself must not include any embedded spaces.
9164 @item --GNATLINK=@var{linker_name}
9165 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9166 Program used for linking. The default is `@command{gnatlink}'. You need to
9167 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9168 or other separator characters. As an example @option{--GNATLINK="lan -x
9169 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9170 linker. Linker switches that are normally appended by @command{gnatmake} to
9171 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9172 A limitation of this syntax is that the name and path name of the executable
9173 itself must not include any embedded spaces.
9177 @item ^-a^/ALL_FILES^
9178 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9179 Consider all files in the make process, even the GNAT internal system
9180 files (for example, the predefined Ada library files), as well as any
9181 locked files. Locked files are files whose ALI file is write-protected.
9183 @command{gnatmake} does not check these files,
9184 because the assumption is that the GNAT internal files are properly up
9185 to date, and also that any write protected ALI files have been properly
9186 installed. Note that if there is an installation problem, such that one
9187 of these files is not up to date, it will be properly caught by the
9189 You may have to specify this switch if you are working on GNAT
9190 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9191 in conjunction with @option{^-f^/FORCE_COMPILE^}
9192 if you need to recompile an entire application,
9193 including run-time files, using special configuration pragmas,
9194 such as a @code{Normalize_Scalars} pragma.
9197 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9200 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9203 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9206 @item ^-b^/ACTIONS=BIND^
9207 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9208 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9209 compilation and binding, but no link.
9210 Can be combined with @option{^-l^/ACTIONS=LINK^}
9211 to do binding and linking. When not combined with
9212 @option{^-c^/ACTIONS=COMPILE^}
9213 all the units in the closure of the main program must have been previously
9214 compiled and must be up to date. The root unit specified by @var{file_name}
9215 may be given without extension, with the source extension or, if no GNAT
9216 Project File is specified, with the ALI file extension.
9218 @item ^-c^/ACTIONS=COMPILE^
9219 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9220 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9221 is also specified. Do not perform linking, except if both
9222 @option{^-b^/ACTIONS=BIND^} and
9223 @option{^-l^/ACTIONS=LINK^} are also specified.
9224 If the root unit specified by @var{file_name} is not a main unit, this is the
9225 default. Otherwise @command{gnatmake} will attempt binding and linking
9226 unless all objects are up to date and the executable is more recent than
9230 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9231 Use a temporary mapping file. A mapping file is a way to communicate to the
9232 compiler two mappings: from unit names to file names (without any directory
9233 information) and from file names to path names (with full directory
9234 information). These mappings are used by the compiler to short-circuit the path
9235 search. When @command{gnatmake} is invoked with this switch, it will create
9236 a temporary mapping file, initially populated by the project manager,
9237 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
9238 Each invocation of the compiler will add the newly accessed sources to the
9239 mapping file. This will improve the source search during the next invocation
9242 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9243 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9244 Use a specific mapping file. The file, specified as a path name (absolute or
9245 relative) by this switch, should already exist, otherwise the switch is
9246 ineffective. The specified mapping file will be communicated to the compiler.
9247 This switch is not compatible with a project file
9248 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9249 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9251 @item ^-d^/DISPLAY_PROGRESS^
9252 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9253 Display progress for each source, up to date or not, as a single line
9256 completed x out of y (zz%)
9259 If the file needs to be compiled this is displayed after the invocation of
9260 the compiler. These lines are displayed even in quiet output mode.
9262 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9263 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9264 Put all object files and ALI file in directory @var{dir}.
9265 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9266 and ALI files go in the current working directory.
9268 This switch cannot be used when using a project file.
9272 @cindex @option{-eL} (@command{gnatmake})
9273 Follow all symbolic links when processing project files.
9276 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9277 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9278 Output the commands for the compiler, the binder and the linker
9279 on ^standard output^SYS$OUTPUT^,
9280 instead of ^standard error^SYS$ERROR^.
9282 @item ^-f^/FORCE_COMPILE^
9283 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9284 Force recompilations. Recompile all sources, even though some object
9285 files may be up to date, but don't recompile predefined or GNAT internal
9286 files or locked files (files with a write-protected ALI file),
9287 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9289 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9290 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9291 When using project files, if some errors or warnings are detected during
9292 parsing and verbose mode is not in effect (no use of switch
9293 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9294 file, rather than its simple file name.
9297 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9298 Enable debugging. This switch is simply passed to the compiler and to the
9301 @item ^-i^/IN_PLACE^
9302 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9303 In normal mode, @command{gnatmake} compiles all object files and ALI files
9304 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9305 then instead object files and ALI files that already exist are overwritten
9306 in place. This means that once a large project is organized into separate
9307 directories in the desired manner, then @command{gnatmake} will automatically
9308 maintain and update this organization. If no ALI files are found on the
9309 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9310 the new object and ALI files are created in the
9311 directory containing the source being compiled. If another organization
9312 is desired, where objects and sources are kept in different directories,
9313 a useful technique is to create dummy ALI files in the desired directories.
9314 When detecting such a dummy file, @command{gnatmake} will be forced to
9315 recompile the corresponding source file, and it will be put the resulting
9316 object and ALI files in the directory where it found the dummy file.
9318 @item ^-j^/PROCESSES=^@var{n}
9319 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9320 @cindex Parallel make
9321 Use @var{n} processes to carry out the (re)compilations. On a
9322 multiprocessor machine compilations will occur in parallel. In the
9323 event of compilation errors, messages from various compilations might
9324 get interspersed (but @command{gnatmake} will give you the full ordered
9325 list of failing compiles at the end). If this is problematic, rerun
9326 the make process with n set to 1 to get a clean list of messages.
9328 @item ^-k^/CONTINUE_ON_ERROR^
9329 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9330 Keep going. Continue as much as possible after a compilation error. To
9331 ease the programmer's task in case of compilation errors, the list of
9332 sources for which the compile fails is given when @command{gnatmake}
9335 If @command{gnatmake} is invoked with several @file{file_names} and with this
9336 switch, if there are compilation errors when building an executable,
9337 @command{gnatmake} will not attempt to build the following executables.
9339 @item ^-l^/ACTIONS=LINK^
9340 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9341 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9342 and linking. Linking will not be performed if combined with
9343 @option{^-c^/ACTIONS=COMPILE^}
9344 but not with @option{^-b^/ACTIONS=BIND^}.
9345 When not combined with @option{^-b^/ACTIONS=BIND^}
9346 all the units in the closure of the main program must have been previously
9347 compiled and must be up to date, and the main program needs to have been bound.
9348 The root unit specified by @var{file_name}
9349 may be given without extension, with the source extension or, if no GNAT
9350 Project File is specified, with the ALI file extension.
9352 @item ^-m^/MINIMAL_RECOMPILATION^
9353 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9354 Specify that the minimum necessary amount of recompilations
9355 be performed. In this mode @command{gnatmake} ignores time
9356 stamp differences when the only
9357 modifications to a source file consist in adding/removing comments,
9358 empty lines, spaces or tabs. This means that if you have changed the
9359 comments in a source file or have simply reformatted it, using this
9360 switch will tell @command{gnatmake} not to recompile files that depend on it
9361 (provided other sources on which these files depend have undergone no
9362 semantic modifications). Note that the debugging information may be
9363 out of date with respect to the sources if the @option{-m} switch causes
9364 a compilation to be switched, so the use of this switch represents a
9365 trade-off between compilation time and accurate debugging information.
9367 @item ^-M^/DEPENDENCIES_LIST^
9368 @cindex Dependencies, producing list
9369 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9370 Check if all objects are up to date. If they are, output the object
9371 dependences to @file{stdout} in a form that can be directly exploited in
9372 a @file{Makefile}. By default, each source file is prefixed with its
9373 (relative or absolute) directory name. This name is whatever you
9374 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9375 and @option{^-I^/SEARCH^} switches. If you use
9376 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9377 @option{^-q^/QUIET^}
9378 (see below), only the source file names,
9379 without relative paths, are output. If you just specify the
9380 @option{^-M^/DEPENDENCIES_LIST^}
9381 switch, dependencies of the GNAT internal system files are omitted. This
9382 is typically what you want. If you also specify
9383 the @option{^-a^/ALL_FILES^} switch,
9384 dependencies of the GNAT internal files are also listed. Note that
9385 dependencies of the objects in external Ada libraries (see switch
9386 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9389 @item ^-n^/DO_OBJECT_CHECK^
9390 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9391 Don't compile, bind, or link. Checks if all objects are up to date.
9392 If they are not, the full name of the first file that needs to be
9393 recompiled is printed.
9394 Repeated use of this option, followed by compiling the indicated source
9395 file, will eventually result in recompiling all required units.
9397 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9398 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9399 Output executable name. The name of the final executable program will be
9400 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9401 name for the executable will be the name of the input file in appropriate form
9402 for an executable file on the host system.
9404 This switch cannot be used when invoking @command{gnatmake} with several
9407 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9408 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9409 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9410 automatically missing object directories, library directories and exec
9413 @item ^-P^/PROJECT_FILE=^@var{project}
9414 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9415 Use project file @var{project}. Only one such switch can be used.
9416 @xref{gnatmake and Project Files}.
9419 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9420 Quiet. When this flag is not set, the commands carried out by
9421 @command{gnatmake} are displayed.
9423 @item ^-s^/SWITCH_CHECK/^
9424 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9425 Recompile if compiler switches have changed since last compilation.
9426 All compiler switches but -I and -o are taken into account in the
9428 orders between different ``first letter'' switches are ignored, but
9429 orders between same switches are taken into account. For example,
9430 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9431 is equivalent to @option{-O -g}.
9433 This switch is recommended when Integrated Preprocessing is used.
9436 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9437 Unique. Recompile at most the main files. It implies -c. Combined with
9438 -f, it is equivalent to calling the compiler directly. Note that using
9439 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9440 (@pxref{Project Files and Main Subprograms}).
9442 @item ^-U^/ALL_PROJECTS^
9443 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9444 When used without a project file or with one or several mains on the command
9445 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9446 on the command line, all sources of all project files are checked and compiled
9447 if not up to date, and libraries are rebuilt, if necessary.
9450 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9451 Verbose. Display the reason for all recompilations @command{gnatmake}
9452 decides are necessary, with the highest verbosity level.
9454 @item ^-vl^/LOW_VERBOSITY^
9455 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9456 Verbosity level Low. Display fewer lines than in verbosity Medium.
9458 @item ^-vm^/MEDIUM_VERBOSITY^
9459 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9460 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9462 @item ^-vh^/HIGH_VERBOSITY^
9463 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9464 Verbosity level High. Equivalent to ^-v^/REASONS^.
9466 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9467 Indicate the verbosity of the parsing of GNAT project files.
9468 @xref{Switches Related to Project Files}.
9470 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9471 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9472 Indicate that sources that are not part of any Project File may be compiled.
9473 Normally, when using Project Files, only sources that are part of a Project
9474 File may be compile. When this switch is used, a source outside of all Project
9475 Files may be compiled. The ALI file and the object file will be put in the
9476 object directory of the main Project. The compilation switches used will only
9477 be those specified on the command line. Even when
9478 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9479 command line need to be sources of a project file.
9481 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9482 Indicate that external variable @var{name} has the value @var{value}.
9483 The Project Manager will use this value for occurrences of
9484 @code{external(name)} when parsing the project file.
9485 @xref{Switches Related to Project Files}.
9488 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9489 No main subprogram. Bind and link the program even if the unit name
9490 given on the command line is a package name. The resulting executable
9491 will execute the elaboration routines of the package and its closure,
9492 then the finalization routines.
9497 @item @command{gcc} @asis{switches}
9499 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9500 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9503 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9504 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9505 automatically treated as a compiler switch, and passed on to all
9506 compilations that are carried out.
9511 Source and library search path switches:
9515 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9516 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9517 When looking for source files also look in directory @var{dir}.
9518 The order in which source files search is undertaken is
9519 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9521 @item ^-aL^/SKIP_MISSING=^@var{dir}
9522 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9523 Consider @var{dir} as being an externally provided Ada library.
9524 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9525 files have been located in directory @var{dir}. This allows you to have
9526 missing bodies for the units in @var{dir} and to ignore out of date bodies
9527 for the same units. You still need to specify
9528 the location of the specs for these units by using the switches
9529 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9530 or @option{^-I^/SEARCH=^@var{dir}}.
9531 Note: this switch is provided for compatibility with previous versions
9532 of @command{gnatmake}. The easier method of causing standard libraries
9533 to be excluded from consideration is to write-protect the corresponding
9536 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9537 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9538 When searching for library and object files, look in directory
9539 @var{dir}. The order in which library files are searched is described in
9540 @ref{Search Paths for gnatbind}.
9542 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9543 @cindex Search paths, for @command{gnatmake}
9544 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9545 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9546 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9548 @item ^-I^/SEARCH=^@var{dir}
9549 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9550 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9551 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9553 @item ^-I-^/NOCURRENT_DIRECTORY^
9554 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9555 @cindex Source files, suppressing search
9556 Do not look for source files in the directory containing the source
9557 file named in the command line.
9558 Do not look for ALI or object files in the directory
9559 where @command{gnatmake} was invoked.
9561 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9562 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9563 @cindex Linker libraries
9564 Add directory @var{dir} to the list of directories in which the linker
9565 will search for libraries. This is equivalent to
9566 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9568 Furthermore, under Windows, the sources pointed to by the libraries path
9569 set in the registry are not searched for.
9573 @cindex @option{-nostdinc} (@command{gnatmake})
9574 Do not look for source files in the system default directory.
9577 @cindex @option{-nostdlib} (@command{gnatmake})
9578 Do not look for library files in the system default directory.
9580 @item --RTS=@var{rts-path}
9581 @cindex @option{--RTS} (@command{gnatmake})
9582 Specifies the default location of the runtime library. GNAT looks for the
9584 in the following directories, and stops as soon as a valid runtime is found
9585 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9586 @file{ada_object_path} present):
9589 @item <current directory>/$rts_path
9591 @item <default-search-dir>/$rts_path
9593 @item <default-search-dir>/rts-$rts_path
9597 The selected path is handled like a normal RTS path.
9601 @node Mode Switches for gnatmake
9602 @section Mode Switches for @command{gnatmake}
9605 The mode switches (referred to as @code{mode_switches}) allow the
9606 inclusion of switches that are to be passed to the compiler itself, the
9607 binder or the linker. The effect of a mode switch is to cause all
9608 subsequent switches up to the end of the switch list, or up to the next
9609 mode switch, to be interpreted as switches to be passed on to the
9610 designated component of GNAT.
9614 @item -cargs @var{switches}
9615 @cindex @option{-cargs} (@command{gnatmake})
9616 Compiler switches. Here @var{switches} is a list of switches
9617 that are valid switches for @command{gcc}. They will be passed on to
9618 all compile steps performed by @command{gnatmake}.
9620 @item -bargs @var{switches}
9621 @cindex @option{-bargs} (@command{gnatmake})
9622 Binder switches. Here @var{switches} is a list of switches
9623 that are valid switches for @code{gnatbind}. They will be passed on to
9624 all bind steps performed by @command{gnatmake}.
9626 @item -largs @var{switches}
9627 @cindex @option{-largs} (@command{gnatmake})
9628 Linker switches. Here @var{switches} is a list of switches
9629 that are valid switches for @command{gnatlink}. They will be passed on to
9630 all link steps performed by @command{gnatmake}.
9632 @item -margs @var{switches}
9633 @cindex @option{-margs} (@command{gnatmake})
9634 Make switches. The switches are directly interpreted by @command{gnatmake},
9635 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9639 @node Notes on the Command Line
9640 @section Notes on the Command Line
9643 This section contains some additional useful notes on the operation
9644 of the @command{gnatmake} command.
9648 @cindex Recompilation, by @command{gnatmake}
9649 If @command{gnatmake} finds no ALI files, it recompiles the main program
9650 and all other units required by the main program.
9651 This means that @command{gnatmake}
9652 can be used for the initial compile, as well as during subsequent steps of
9653 the development cycle.
9656 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9657 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9658 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9662 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9663 is used to specify both source and
9664 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9665 instead if you just want to specify
9666 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9667 if you want to specify library paths
9671 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9672 This may conveniently be used to exclude standard libraries from
9673 consideration and in particular it means that the use of the
9674 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9675 unless @option{^-a^/ALL_FILES^} is also specified.
9678 @command{gnatmake} has been designed to make the use of Ada libraries
9679 particularly convenient. Assume you have an Ada library organized
9680 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9681 of your Ada compilation units,
9682 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9683 specs of these units, but no bodies. Then to compile a unit
9684 stored in @code{main.adb}, which uses this Ada library you would just type
9688 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9691 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9692 /SKIP_MISSING=@i{[OBJ_DIR]} main
9697 Using @command{gnatmake} along with the
9698 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9699 switch provides a mechanism for avoiding unnecessary recompilations. Using
9701 you can update the comments/format of your
9702 source files without having to recompile everything. Note, however, that
9703 adding or deleting lines in a source files may render its debugging
9704 info obsolete. If the file in question is a spec, the impact is rather
9705 limited, as that debugging info will only be useful during the
9706 elaboration phase of your program. For bodies the impact can be more
9707 significant. In all events, your debugger will warn you if a source file
9708 is more recent than the corresponding object, and alert you to the fact
9709 that the debugging information may be out of date.
9712 @node How gnatmake Works
9713 @section How @command{gnatmake} Works
9716 Generally @command{gnatmake} automatically performs all necessary
9717 recompilations and you don't need to worry about how it works. However,
9718 it may be useful to have some basic understanding of the @command{gnatmake}
9719 approach and in particular to understand how it uses the results of
9720 previous compilations without incorrectly depending on them.
9722 First a definition: an object file is considered @dfn{up to date} if the
9723 corresponding ALI file exists and if all the source files listed in the
9724 dependency section of this ALI file have time stamps matching those in
9725 the ALI file. This means that neither the source file itself nor any
9726 files that it depends on have been modified, and hence there is no need
9727 to recompile this file.
9729 @command{gnatmake} works by first checking if the specified main unit is up
9730 to date. If so, no compilations are required for the main unit. If not,
9731 @command{gnatmake} compiles the main program to build a new ALI file that
9732 reflects the latest sources. Then the ALI file of the main unit is
9733 examined to find all the source files on which the main program depends,
9734 and @command{gnatmake} recursively applies the above procedure on all these
9737 This process ensures that @command{gnatmake} only trusts the dependencies
9738 in an existing ALI file if they are known to be correct. Otherwise it
9739 always recompiles to determine a new, guaranteed accurate set of
9740 dependencies. As a result the program is compiled ``upside down'' from what may
9741 be more familiar as the required order of compilation in some other Ada
9742 systems. In particular, clients are compiled before the units on which
9743 they depend. The ability of GNAT to compile in any order is critical in
9744 allowing an order of compilation to be chosen that guarantees that
9745 @command{gnatmake} will recompute a correct set of new dependencies if
9748 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9749 imported by several of the executables, it will be recompiled at most once.
9751 Note: when using non-standard naming conventions
9752 (@pxref{Using Other File Names}), changing through a configuration pragmas
9753 file the version of a source and invoking @command{gnatmake} to recompile may
9754 have no effect, if the previous version of the source is still accessible
9755 by @command{gnatmake}. It may be necessary to use the switch
9756 ^-f^/FORCE_COMPILE^.
9758 @node Examples of gnatmake Usage
9759 @section Examples of @command{gnatmake} Usage
9762 @item gnatmake hello.adb
9763 Compile all files necessary to bind and link the main program
9764 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9765 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9767 @item gnatmake main1 main2 main3
9768 Compile all files necessary to bind and link the main programs
9769 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9770 (containing unit @code{Main2}) and @file{main3.adb}
9771 (containing unit @code{Main3}) and bind and link the resulting object files
9772 to generate three executable files @file{^main1^MAIN1.EXE^},
9773 @file{^main2^MAIN2.EXE^}
9774 and @file{^main3^MAIN3.EXE^}.
9777 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9781 @item gnatmake Main_Unit /QUIET
9782 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9783 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9785 Compile all files necessary to bind and link the main program unit
9786 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9787 be done with optimization level 2 and the order of elaboration will be
9788 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9789 displaying commands it is executing.
9792 @c *************************
9793 @node Improving Performance
9794 @chapter Improving Performance
9795 @cindex Improving performance
9798 This chapter presents several topics related to program performance.
9799 It first describes some of the tradeoffs that need to be considered
9800 and some of the techniques for making your program run faster.
9801 It then documents the @command{gnatelim} tool and unused subprogram/data
9802 elimination feature, which can reduce the size of program executables.
9804 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9805 driver (see @ref{The GNAT Driver and Project Files}).
9809 * Performance Considerations::
9810 * Text_IO Suggestions::
9811 * Reducing Size of Ada Executables with gnatelim::
9812 * Reducing Size of Executables with unused subprogram/data elimination::
9816 @c *****************************
9817 @node Performance Considerations
9818 @section Performance Considerations
9821 The GNAT system provides a number of options that allow a trade-off
9826 performance of the generated code
9829 speed of compilation
9832 minimization of dependences and recompilation
9835 the degree of run-time checking.
9839 The defaults (if no options are selected) aim at improving the speed
9840 of compilation and minimizing dependences, at the expense of performance
9841 of the generated code:
9848 no inlining of subprogram calls
9851 all run-time checks enabled except overflow and elaboration checks
9855 These options are suitable for most program development purposes. This
9856 chapter describes how you can modify these choices, and also provides
9857 some guidelines on debugging optimized code.
9860 * Controlling Run-Time Checks::
9861 * Use of Restrictions::
9862 * Optimization Levels::
9863 * Debugging Optimized Code::
9864 * Inlining of Subprograms::
9865 * Other Optimization Switches::
9866 * Optimization and Strict Aliasing::
9869 * Coverage Analysis::
9873 @node Controlling Run-Time Checks
9874 @subsection Controlling Run-Time Checks
9877 By default, GNAT generates all run-time checks, except integer overflow
9878 checks, stack overflow checks, and checks for access before elaboration on
9879 subprogram calls. The latter are not required in default mode, because all
9880 necessary checking is done at compile time.
9881 @cindex @option{-gnatp} (@command{gcc})
9882 @cindex @option{-gnato} (@command{gcc})
9883 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9884 be modified. @xref{Run-Time Checks}.
9886 Our experience is that the default is suitable for most development
9889 We treat integer overflow specially because these
9890 are quite expensive and in our experience are not as important as other
9891 run-time checks in the development process. Note that division by zero
9892 is not considered an overflow check, and divide by zero checks are
9893 generated where required by default.
9895 Elaboration checks are off by default, and also not needed by default, since
9896 GNAT uses a static elaboration analysis approach that avoids the need for
9897 run-time checking. This manual contains a full chapter discussing the issue
9898 of elaboration checks, and if the default is not satisfactory for your use,
9899 you should read this chapter.
9901 For validity checks, the minimal checks required by the Ada Reference
9902 Manual (for case statements and assignments to array elements) are on
9903 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9904 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9905 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9906 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9907 are also suppressed entirely if @option{-gnatp} is used.
9909 @cindex Overflow checks
9910 @cindex Checks, overflow
9913 @cindex pragma Suppress
9914 @cindex pragma Unsuppress
9915 Note that the setting of the switches controls the default setting of
9916 the checks. They may be modified using either @code{pragma Suppress} (to
9917 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9918 checks) in the program source.
9920 @node Use of Restrictions
9921 @subsection Use of Restrictions
9924 The use of pragma Restrictions allows you to control which features are
9925 permitted in your program. Apart from the obvious point that if you avoid
9926 relatively expensive features like finalization (enforceable by the use
9927 of pragma Restrictions (No_Finalization), the use of this pragma does not
9928 affect the generated code in most cases.
9930 One notable exception to this rule is that the possibility of task abort
9931 results in some distributed overhead, particularly if finalization or
9932 exception handlers are used. The reason is that certain sections of code
9933 have to be marked as non-abortable.
9935 If you use neither the @code{abort} statement, nor asynchronous transfer
9936 of control (@code{select @dots{} then abort}), then this distributed overhead
9937 is removed, which may have a general positive effect in improving
9938 overall performance. Especially code involving frequent use of tasking
9939 constructs and controlled types will show much improved performance.
9940 The relevant restrictions pragmas are
9942 @smallexample @c ada
9943 pragma Restrictions (No_Abort_Statements);
9944 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9948 It is recommended that these restriction pragmas be used if possible. Note
9949 that this also means that you can write code without worrying about the
9950 possibility of an immediate abort at any point.
9952 @node Optimization Levels
9953 @subsection Optimization Levels
9954 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9957 Without any optimization ^option,^qualifier,^
9958 the compiler's goal is to reduce the cost of
9959 compilation and to make debugging produce the expected results.
9960 Statements are independent: if you stop the program with a breakpoint between
9961 statements, you can then assign a new value to any variable or change
9962 the program counter to any other statement in the subprogram and get exactly
9963 the results you would expect from the source code.
9965 Turning on optimization makes the compiler attempt to improve the
9966 performance and/or code size at the expense of compilation time and
9967 possibly the ability to debug the program.
9970 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9971 the last such option is the one that is effective.
9974 The default is optimization off. This results in the fastest compile
9975 times, but GNAT makes absolutely no attempt to optimize, and the
9976 generated programs are considerably larger and slower than when
9977 optimization is enabled. You can use the
9979 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9980 @option{-O2}, @option{-O3}, and @option{-Os})
9983 @code{OPTIMIZE} qualifier
9985 to @command{gcc} to control the optimization level:
9988 @item ^-O0^/OPTIMIZE=NONE^
9989 No optimization (the default);
9990 generates unoptimized code but has
9991 the fastest compilation time.
9993 Note that many other compilers do fairly extensive optimization
9994 even if ``no optimization'' is specified. With gcc, it is
9995 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9996 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9997 really does mean no optimization at all. This difference between
9998 gcc and other compilers should be kept in mind when doing
9999 performance comparisons.
10001 @item ^-O1^/OPTIMIZE=SOME^
10002 Moderate optimization;
10003 optimizes reasonably well but does not
10004 degrade compilation time significantly.
10006 @item ^-O2^/OPTIMIZE=ALL^
10008 @itemx /OPTIMIZE=DEVELOPMENT
10011 generates highly optimized code and has
10012 the slowest compilation time.
10014 @item ^-O3^/OPTIMIZE=INLINING^
10015 Full optimization as in @option{-O2},
10016 and also attempts automatic inlining of small
10017 subprograms within a unit (@pxref{Inlining of Subprograms}).
10019 @item ^-Os^/OPTIMIZE=SPACE^
10020 Optimize space usage of resulting program.
10024 Higher optimization levels perform more global transformations on the
10025 program and apply more expensive analysis algorithms in order to generate
10026 faster and more compact code. The price in compilation time, and the
10027 resulting improvement in execution time,
10028 both depend on the particular application and the hardware environment.
10029 You should experiment to find the best level for your application.
10031 Since the precise set of optimizations done at each level will vary from
10032 release to release (and sometime from target to target), it is best to think
10033 of the optimization settings in general terms.
10034 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10035 the GNU Compiler Collection (GCC)}, for details about
10036 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10037 individually enable or disable specific optimizations.
10039 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10040 been tested extensively at all optimization levels. There are some bugs
10041 which appear only with optimization turned on, but there have also been
10042 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10043 level of optimization does not improve the reliability of the code
10044 generator, which in practice is highly reliable at all optimization
10047 Note regarding the use of @option{-O3}: The use of this optimization level
10048 is generally discouraged with GNAT, since it often results in larger
10049 executables which run more slowly. See further discussion of this point
10050 in @ref{Inlining of Subprograms}.
10052 @node Debugging Optimized Code
10053 @subsection Debugging Optimized Code
10054 @cindex Debugging optimized code
10055 @cindex Optimization and debugging
10058 Although it is possible to do a reasonable amount of debugging at
10060 nonzero optimization levels,
10061 the higher the level the more likely that
10064 @option{/OPTIMIZE} settings other than @code{NONE},
10065 such settings will make it more likely that
10067 source-level constructs will have been eliminated by optimization.
10068 For example, if a loop is strength-reduced, the loop
10069 control variable may be completely eliminated and thus cannot be
10070 displayed in the debugger.
10071 This can only happen at @option{-O2} or @option{-O3}.
10072 Explicit temporary variables that you code might be eliminated at
10073 ^level^setting^ @option{-O1} or higher.
10075 The use of the @option{^-g^/DEBUG^} switch,
10076 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10077 which is needed for source-level debugging,
10078 affects the size of the program executable on disk,
10079 and indeed the debugging information can be quite large.
10080 However, it has no effect on the generated code (and thus does not
10081 degrade performance)
10083 Since the compiler generates debugging tables for a compilation unit before
10084 it performs optimizations, the optimizing transformations may invalidate some
10085 of the debugging data. You therefore need to anticipate certain
10086 anomalous situations that may arise while debugging optimized code.
10087 These are the most common cases:
10091 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10093 the PC bouncing back and forth in the code. This may result from any of
10094 the following optimizations:
10098 @i{Common subexpression elimination:} using a single instance of code for a
10099 quantity that the source computes several times. As a result you
10100 may not be able to stop on what looks like a statement.
10103 @i{Invariant code motion:} moving an expression that does not change within a
10104 loop, to the beginning of the loop.
10107 @i{Instruction scheduling:} moving instructions so as to
10108 overlap loads and stores (typically) with other code, or in
10109 general to move computations of values closer to their uses. Often
10110 this causes you to pass an assignment statement without the assignment
10111 happening and then later bounce back to the statement when the
10112 value is actually needed. Placing a breakpoint on a line of code
10113 and then stepping over it may, therefore, not always cause all the
10114 expected side-effects.
10118 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10119 two identical pieces of code are merged and the program counter suddenly
10120 jumps to a statement that is not supposed to be executed, simply because
10121 it (and the code following) translates to the same thing as the code
10122 that @emph{was} supposed to be executed. This effect is typically seen in
10123 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10124 a @code{break} in a C @code{^switch^switch^} statement.
10127 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10128 There are various reasons for this effect:
10132 In a subprogram prologue, a parameter may not yet have been moved to its
10136 A variable may be dead, and its register re-used. This is
10137 probably the most common cause.
10140 As mentioned above, the assignment of a value to a variable may
10144 A variable may be eliminated entirely by value propagation or
10145 other means. In this case, GCC may incorrectly generate debugging
10146 information for the variable
10150 In general, when an unexpected value appears for a local variable or parameter
10151 you should first ascertain if that value was actually computed by
10152 your program, as opposed to being incorrectly reported by the debugger.
10154 array elements in an object designated by an access value
10155 are generally less of a problem, once you have ascertained that the access
10157 Typically, this means checking variables in the preceding code and in the
10158 calling subprogram to verify that the value observed is explainable from other
10159 values (one must apply the procedure recursively to those
10160 other values); or re-running the code and stopping a little earlier
10161 (perhaps before the call) and stepping to better see how the variable obtained
10162 the value in question; or continuing to step @emph{from} the point of the
10163 strange value to see if code motion had simply moved the variable's
10168 In light of such anomalies, a recommended technique is to use @option{-O0}
10169 early in the software development cycle, when extensive debugging capabilities
10170 are most needed, and then move to @option{-O1} and later @option{-O2} as
10171 the debugger becomes less critical.
10172 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10173 a release management issue.
10175 Note that if you use @option{-g} you can then use the @command{strip} program
10176 on the resulting executable,
10177 which removes both debugging information and global symbols.
10180 @node Inlining of Subprograms
10181 @subsection Inlining of Subprograms
10184 A call to a subprogram in the current unit is inlined if all the
10185 following conditions are met:
10189 The optimization level is at least @option{-O1}.
10192 The called subprogram is suitable for inlining: It must be small enough
10193 and not contain something that @command{gcc} cannot support in inlined
10197 @cindex pragma Inline
10199 Either @code{pragma Inline} applies to the subprogram, or it is local
10200 to the unit and called once from within it, or it is small and automatic
10201 inlining (optimization level @option{-O3}) is specified.
10205 Calls to subprograms in @code{with}'ed units are normally not inlined.
10206 To achieve actual inlining (that is, replacement of the call by the code
10207 in the body of the subprogram), the following conditions must all be true.
10211 The optimization level is at least @option{-O1}.
10214 The called subprogram is suitable for inlining: It must be small enough
10215 and not contain something that @command{gcc} cannot support in inlined
10219 The call appears in a body (not in a package spec).
10222 There is a @code{pragma Inline} for the subprogram.
10225 @cindex @option{-gnatn} (@command{gcc})
10226 The @option{^-gnatn^/INLINE^} switch
10227 is used in the @command{gcc} command line
10230 Even if all these conditions are met, it may not be possible for
10231 the compiler to inline the call, due to the length of the body,
10232 or features in the body that make it impossible for the compiler
10233 to do the inlining.
10235 Note that specifying the @option{-gnatn} switch causes additional
10236 compilation dependencies. Consider the following:
10238 @smallexample @c ada
10258 With the default behavior (no @option{-gnatn} switch specified), the
10259 compilation of the @code{Main} procedure depends only on its own source,
10260 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10261 means that editing the body of @code{R} does not require recompiling
10264 On the other hand, the call @code{R.Q} is not inlined under these
10265 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10266 is compiled, the call will be inlined if the body of @code{Q} is small
10267 enough, but now @code{Main} depends on the body of @code{R} in
10268 @file{r.adb} as well as on the spec. This means that if this body is edited,
10269 the main program must be recompiled. Note that this extra dependency
10270 occurs whether or not the call is in fact inlined by @command{gcc}.
10272 The use of front end inlining with @option{-gnatN} generates similar
10273 additional dependencies.
10275 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10276 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10277 can be used to prevent
10278 all inlining. This switch overrides all other conditions and ensures
10279 that no inlining occurs. The extra dependences resulting from
10280 @option{-gnatn} will still be active, even if
10281 this switch is used to suppress the resulting inlining actions.
10283 @cindex @option{-fno-inline-functions} (@command{gcc})
10284 Note: The @option{-fno-inline-functions} switch can be used to prevent
10285 automatic inlining of small subprograms if @option{-O3} is used.
10287 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10288 Note: The @option{-fno-inline-functions-called-once} switch
10289 can be used to prevent inlining of subprograms local to the unit
10290 and called once from within it if @option{-O1} is used.
10292 Note regarding the use of @option{-O3}: There is no difference in inlining
10293 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10294 pragma @code{Inline} assuming the use of @option{-gnatn}
10295 or @option{-gnatN} (the switches that activate inlining). If you have used
10296 pragma @code{Inline} in appropriate cases, then it is usually much better
10297 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10298 in this case only has the effect of inlining subprograms you did not
10299 think should be inlined. We often find that the use of @option{-O3} slows
10300 down code by performing excessive inlining, leading to increased instruction
10301 cache pressure from the increased code size. So the bottom line here is
10302 that you should not automatically assume that @option{-O3} is better than
10303 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10304 it actually improves performance.
10306 @node Other Optimization Switches
10307 @subsection Other Optimization Switches
10308 @cindex Optimization Switches
10310 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10311 @command{gcc} optimization switches are potentially usable. These switches
10312 have not been extensively tested with GNAT but can generally be expected
10313 to work. Examples of switches in this category are
10314 @option{-funroll-loops} and
10315 the various target-specific @option{-m} options (in particular, it has been
10316 observed that @option{-march=pentium4} can significantly improve performance
10317 on appropriate machines). For full details of these switches, see
10318 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10319 the GNU Compiler Collection (GCC)}.
10321 @node Optimization and Strict Aliasing
10322 @subsection Optimization and Strict Aliasing
10324 @cindex Strict Aliasing
10325 @cindex No_Strict_Aliasing
10328 The strong typing capabilities of Ada allow an optimizer to generate
10329 efficient code in situations where other languages would be forced to
10330 make worst case assumptions preventing such optimizations. Consider
10331 the following example:
10333 @smallexample @c ada
10336 type Int1 is new Integer;
10337 type Int2 is new Integer;
10338 type Int1A is access Int1;
10339 type Int2A is access Int2;
10346 for J in Data'Range loop
10347 if Data (J) = Int1V.all then
10348 Int2V.all := Int2V.all + 1;
10357 In this example, since the variable @code{Int1V} can only access objects
10358 of type @code{Int1}, and @code{Int2V} can only access objects of type
10359 @code{Int2}, there is no possibility that the assignment to
10360 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10361 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10362 for all iterations of the loop and avoid the extra memory reference
10363 required to dereference it each time through the loop.
10365 This kind of optimization, called strict aliasing analysis, is
10366 triggered by specifying an optimization level of @option{-O2} or
10367 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10368 when access values are involved.
10370 However, although this optimization is always correct in terms of
10371 the formal semantics of the Ada Reference Manual, difficulties can
10372 arise if features like @code{Unchecked_Conversion} are used to break
10373 the typing system. Consider the following complete program example:
10375 @smallexample @c ada
10378 type int1 is new integer;
10379 type int2 is new integer;
10380 type a1 is access int1;
10381 type a2 is access int2;
10386 function to_a2 (Input : a1) return a2;
10389 with Unchecked_Conversion;
10391 function to_a2 (Input : a1) return a2 is
10393 new Unchecked_Conversion (a1, a2);
10395 return to_a2u (Input);
10401 with Text_IO; use Text_IO;
10403 v1 : a1 := new int1;
10404 v2 : a2 := to_a2 (v1);
10408 put_line (int1'image (v1.all));
10414 This program prints out 0 in @option{-O0} or @option{-O1}
10415 mode, but it prints out 1 in @option{-O2} mode. That's
10416 because in strict aliasing mode, the compiler can and
10417 does assume that the assignment to @code{v2.all} could not
10418 affect the value of @code{v1.all}, since different types
10421 This behavior is not a case of non-conformance with the standard, since
10422 the Ada RM specifies that an unchecked conversion where the resulting
10423 bit pattern is not a correct value of the target type can result in an
10424 abnormal value and attempting to reference an abnormal value makes the
10425 execution of a program erroneous. That's the case here since the result
10426 does not point to an object of type @code{int2}. This means that the
10427 effect is entirely unpredictable.
10429 However, although that explanation may satisfy a language
10430 lawyer, in practice an applications programmer expects an
10431 unchecked conversion involving pointers to create true
10432 aliases and the behavior of printing 1 seems plain wrong.
10433 In this case, the strict aliasing optimization is unwelcome.
10435 Indeed the compiler recognizes this possibility, and the
10436 unchecked conversion generates a warning:
10439 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10440 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10441 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10445 Unfortunately the problem is recognized when compiling the body of
10446 package @code{p2}, but the actual "bad" code is generated while
10447 compiling the body of @code{m} and this latter compilation does not see
10448 the suspicious @code{Unchecked_Conversion}.
10450 As implied by the warning message, there are approaches you can use to
10451 avoid the unwanted strict aliasing optimization in a case like this.
10453 One possibility is to simply avoid the use of @option{-O2}, but
10454 that is a bit drastic, since it throws away a number of useful
10455 optimizations that do not involve strict aliasing assumptions.
10457 A less drastic approach is to compile the program using the
10458 option @option{-fno-strict-aliasing}. Actually it is only the
10459 unit containing the dereferencing of the suspicious pointer
10460 that needs to be compiled. So in this case, if we compile
10461 unit @code{m} with this switch, then we get the expected
10462 value of zero printed. Analyzing which units might need
10463 the switch can be painful, so a more reasonable approach
10464 is to compile the entire program with options @option{-O2}
10465 and @option{-fno-strict-aliasing}. If the performance is
10466 satisfactory with this combination of options, then the
10467 advantage is that the entire issue of possible "wrong"
10468 optimization due to strict aliasing is avoided.
10470 To avoid the use of compiler switches, the configuration
10471 pragma @code{No_Strict_Aliasing} with no parameters may be
10472 used to specify that for all access types, the strict
10473 aliasing optimization should be suppressed.
10475 However, these approaches are still overkill, in that they causes
10476 all manipulations of all access values to be deoptimized. A more
10477 refined approach is to concentrate attention on the specific
10478 access type identified as problematic.
10480 First, if a careful analysis of uses of the pointer shows
10481 that there are no possible problematic references, then
10482 the warning can be suppressed by bracketing the
10483 instantiation of @code{Unchecked_Conversion} to turn
10486 @smallexample @c ada
10487 pragma Warnings (Off);
10489 new Unchecked_Conversion (a1, a2);
10490 pragma Warnings (On);
10494 Of course that approach is not appropriate for this particular
10495 example, since indeed there is a problematic reference. In this
10496 case we can take one of two other approaches.
10498 The first possibility is to move the instantiation of unchecked
10499 conversion to the unit in which the type is declared. In
10500 this example, we would move the instantiation of
10501 @code{Unchecked_Conversion} from the body of package
10502 @code{p2} to the spec of package @code{p1}. Now the
10503 warning disappears. That's because any use of the
10504 access type knows there is a suspicious unchecked
10505 conversion, and the strict aliasing optimization
10506 is automatically suppressed for the type.
10508 If it is not practical to move the unchecked conversion to the same unit
10509 in which the destination access type is declared (perhaps because the
10510 source type is not visible in that unit), you may use pragma
10511 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10512 same declarative sequence as the declaration of the access type:
10514 @smallexample @c ada
10515 type a2 is access int2;
10516 pragma No_Strict_Aliasing (a2);
10520 Here again, the compiler now knows that the strict aliasing optimization
10521 should be suppressed for any reference to type @code{a2} and the
10522 expected behavior is obtained.
10524 Finally, note that although the compiler can generate warnings for
10525 simple cases of unchecked conversions, there are tricker and more
10526 indirect ways of creating type incorrect aliases which the compiler
10527 cannot detect. Examples are the use of address overlays and unchecked
10528 conversions involving composite types containing access types as
10529 components. In such cases, no warnings are generated, but there can
10530 still be aliasing problems. One safe coding practice is to forbid the
10531 use of address clauses for type overlaying, and to allow unchecked
10532 conversion only for primitive types. This is not really a significant
10533 restriction since any possible desired effect can be achieved by
10534 unchecked conversion of access values.
10536 The aliasing analysis done in strict aliasing mode can certainly
10537 have significant benefits. We have seen cases of large scale
10538 application code where the time is increased by up to 5% by turning
10539 this optimization off. If you have code that includes significant
10540 usage of unchecked conversion, you might want to just stick with
10541 @option{-O1} and avoid the entire issue. If you get adequate
10542 performance at this level of optimization level, that's probably
10543 the safest approach. If tests show that you really need higher
10544 levels of optimization, then you can experiment with @option{-O2}
10545 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10546 has on size and speed of the code. If you really need to use
10547 @option{-O2} with strict aliasing in effect, then you should
10548 review any uses of unchecked conversion of access types,
10549 particularly if you are getting the warnings described above.
10552 @node Coverage Analysis
10553 @subsection Coverage Analysis
10556 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10557 the user to determine the distribution of execution time across a program,
10558 @pxref{Profiling} for details of usage.
10562 @node Text_IO Suggestions
10563 @section @code{Text_IO} Suggestions
10564 @cindex @code{Text_IO} and performance
10567 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10568 the requirement of maintaining page and line counts. If performance
10569 is critical, a recommendation is to use @code{Stream_IO} instead of
10570 @code{Text_IO} for volume output, since this package has less overhead.
10572 If @code{Text_IO} must be used, note that by default output to the standard
10573 output and standard error files is unbuffered (this provides better
10574 behavior when output statements are used for debugging, or if the
10575 progress of a program is observed by tracking the output, e.g. by
10576 using the Unix @command{tail -f} command to watch redirected output.
10578 If you are generating large volumes of output with @code{Text_IO} and
10579 performance is an important factor, use a designated file instead
10580 of the standard output file, or change the standard output file to
10581 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10585 @node Reducing Size of Ada Executables with gnatelim
10586 @section Reducing Size of Ada Executables with @code{gnatelim}
10590 This section describes @command{gnatelim}, a tool which detects unused
10591 subprograms and helps the compiler to create a smaller executable for your
10596 * Running gnatelim::
10597 * Correcting the List of Eliminate Pragmas::
10598 * Making Your Executables Smaller::
10599 * Summary of the gnatelim Usage Cycle::
10602 @node About gnatelim
10603 @subsection About @code{gnatelim}
10606 When a program shares a set of Ada
10607 packages with other programs, it may happen that this program uses
10608 only a fraction of the subprograms defined in these packages. The code
10609 created for these unused subprograms increases the size of the executable.
10611 @code{gnatelim} tracks unused subprograms in an Ada program and
10612 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10613 subprograms that are declared but never called. By placing the list of
10614 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10615 recompiling your program, you may decrease the size of its executable,
10616 because the compiler will not generate the code for 'eliminated' subprograms.
10617 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10618 information about this pragma.
10620 @code{gnatelim} needs as its input data the name of the main subprogram
10621 and a bind file for a main subprogram.
10623 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10624 the main subprogram. @code{gnatelim} can work with both Ada and C
10625 bind files; when both are present, it uses the Ada bind file.
10626 The following commands will build the program and create the bind file:
10629 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10630 $ gnatbind main_prog
10633 Note that @code{gnatelim} needs neither object nor ALI files.
10635 @node Running gnatelim
10636 @subsection Running @code{gnatelim}
10639 @code{gnatelim} has the following command-line interface:
10642 $ gnatelim @ovar{options} name
10646 @code{name} should be a name of a source file that contains the main subprogram
10647 of a program (partition).
10649 @code{gnatelim} has the following switches:
10654 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10655 Quiet mode: by default @code{gnatelim} outputs to the standard error
10656 stream the number of program units left to be processed. This option turns
10659 @item ^-v^/VERBOSE^
10660 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10661 Verbose mode: @code{gnatelim} version information is printed as Ada
10662 comments to the standard output stream. Also, in addition to the number of
10663 program units left @code{gnatelim} will output the name of the current unit
10667 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10668 Also look for subprograms from the GNAT run time that can be eliminated. Note
10669 that when @file{gnat.adc} is produced using this switch, the entire program
10670 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10672 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10673 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10674 When looking for source files also look in directory @var{dir}. Specifying
10675 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10676 sources in the current directory.
10678 @item ^-b^/BIND_FILE=^@var{bind_file}
10679 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10680 Specifies @var{bind_file} as the bind file to process. If not set, the name
10681 of the bind file is computed from the full expanded Ada name
10682 of a main subprogram.
10684 @item ^-C^/CONFIG_FILE=^@var{config_file}
10685 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10686 Specifies a file @var{config_file} that contains configuration pragmas. The
10687 file must be specified with full path.
10689 @item ^--GCC^/COMPILER^=@var{compiler_name}
10690 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10691 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10692 available on the path.
10694 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10695 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10696 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10697 available on the path.
10701 @code{gnatelim} sends its output to the standard output stream, and all the
10702 tracing and debug information is sent to the standard error stream.
10703 In order to produce a proper GNAT configuration file
10704 @file{gnat.adc}, redirection must be used:
10708 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10711 $ gnatelim main_prog.adb > gnat.adc
10720 $ gnatelim main_prog.adb >> gnat.adc
10724 in order to append the @code{gnatelim} output to the existing contents of
10728 @node Correcting the List of Eliminate Pragmas
10729 @subsection Correcting the List of Eliminate Pragmas
10732 In some rare cases @code{gnatelim} may try to eliminate
10733 subprograms that are actually called in the program. In this case, the
10734 compiler will generate an error message of the form:
10737 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10741 You will need to manually remove the wrong @code{Eliminate} pragmas from
10742 the @file{gnat.adc} file. You should recompile your program
10743 from scratch after that, because you need a consistent @file{gnat.adc} file
10744 during the entire compilation.
10746 @node Making Your Executables Smaller
10747 @subsection Making Your Executables Smaller
10750 In order to get a smaller executable for your program you now have to
10751 recompile the program completely with the new @file{gnat.adc} file
10752 created by @code{gnatelim} in your current directory:
10755 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10759 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10760 recompile everything
10761 with the set of pragmas @code{Eliminate} that you have obtained with
10762 @command{gnatelim}).
10764 Be aware that the set of @code{Eliminate} pragmas is specific to each
10765 program. It is not recommended to merge sets of @code{Eliminate}
10766 pragmas created for different programs in one @file{gnat.adc} file.
10768 @node Summary of the gnatelim Usage Cycle
10769 @subsection Summary of the gnatelim Usage Cycle
10772 Here is a quick summary of the steps to be taken in order to reduce
10773 the size of your executables with @code{gnatelim}. You may use
10774 other GNAT options to control the optimization level,
10775 to produce the debugging information, to set search path, etc.
10779 Produce a bind file
10782 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10783 $ gnatbind main_prog
10787 Generate a list of @code{Eliminate} pragmas
10790 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10793 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10798 Recompile the application
10801 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10806 @node Reducing Size of Executables with unused subprogram/data elimination
10807 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10808 @findex unused subprogram/data elimination
10811 This section describes how you can eliminate unused subprograms and data from
10812 your executable just by setting options at compilation time.
10815 * About unused subprogram/data elimination::
10816 * Compilation options::
10817 * Example of unused subprogram/data elimination::
10820 @node About unused subprogram/data elimination
10821 @subsection About unused subprogram/data elimination
10824 By default, an executable contains all code and data of its composing objects
10825 (directly linked or coming from statically linked libraries), even data or code
10826 never used by this executable.
10828 This feature will allow you to eliminate such unused code from your
10829 executable, making it smaller (in disk and in memory).
10831 This functionality is available on all Linux platforms except for the IA-64
10832 architecture and on all cross platforms using the ELF binary file format.
10833 In both cases GNU binutils version 2.16 or later are required to enable it.
10835 @node Compilation options
10836 @subsection Compilation options
10839 The operation of eliminating the unused code and data from the final executable
10840 is directly performed by the linker.
10842 In order to do this, it has to work with objects compiled with the
10844 @option{-ffunction-sections} @option{-fdata-sections}.
10845 @cindex @option{-ffunction-sections} (@command{gcc})
10846 @cindex @option{-fdata-sections} (@command{gcc})
10847 These options are usable with C and Ada files.
10848 They will place respectively each
10849 function or data in a separate section in the resulting object file.
10851 Once the objects and static libraries are created with these options, the
10852 linker can perform the dead code elimination. You can do this by setting
10853 the @option{-Wl,--gc-sections} option to gcc command or in the
10854 @option{-largs} section of @command{gnatmake}. This will perform a
10855 garbage collection of code and data never referenced.
10857 If the linker performs a partial link (@option{-r} ld linker option), then you
10858 will need to provide one or several entry point using the
10859 @option{-e} / @option{--entry} ld option.
10861 Note that objects compiled without the @option{-ffunction-sections} and
10862 @option{-fdata-sections} options can still be linked with the executable.
10863 However, no dead code elimination will be performed on those objects (they will
10866 The GNAT static library is now compiled with -ffunction-sections and
10867 -fdata-sections on some platforms. This allows you to eliminate the unused code
10868 and data of the GNAT library from your executable.
10870 @node Example of unused subprogram/data elimination
10871 @subsection Example of unused subprogram/data elimination
10874 Here is a simple example:
10876 @smallexample @c ada
10885 Used_Data : Integer;
10886 Unused_Data : Integer;
10888 procedure Used (Data : Integer);
10889 procedure Unused (Data : Integer);
10892 package body Aux is
10893 procedure Used (Data : Integer) is
10898 procedure Unused (Data : Integer) is
10900 Unused_Data := Data;
10906 @code{Unused} and @code{Unused_Data} are never referenced in this code
10907 excerpt, and hence they may be safely removed from the final executable.
10912 $ nm test | grep used
10913 020015f0 T aux__unused
10914 02005d88 B aux__unused_data
10915 020015cc T aux__used
10916 02005d84 B aux__used_data
10918 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10919 -largs -Wl,--gc-sections
10921 $ nm test | grep used
10922 02005350 T aux__used
10923 0201ffe0 B aux__used_data
10927 It can be observed that the procedure @code{Unused} and the object
10928 @code{Unused_Data} are removed by the linker when using the
10929 appropriate options.
10931 @c ********************************
10932 @node Renaming Files Using gnatchop
10933 @chapter Renaming Files Using @code{gnatchop}
10937 This chapter discusses how to handle files with multiple units by using
10938 the @code{gnatchop} utility. This utility is also useful in renaming
10939 files to meet the standard GNAT default file naming conventions.
10942 * Handling Files with Multiple Units::
10943 * Operating gnatchop in Compilation Mode::
10944 * Command Line for gnatchop::
10945 * Switches for gnatchop::
10946 * Examples of gnatchop Usage::
10949 @node Handling Files with Multiple Units
10950 @section Handling Files with Multiple Units
10953 The basic compilation model of GNAT requires that a file submitted to the
10954 compiler have only one unit and there be a strict correspondence
10955 between the file name and the unit name.
10957 The @code{gnatchop} utility allows both of these rules to be relaxed,
10958 allowing GNAT to process files which contain multiple compilation units
10959 and files with arbitrary file names. @code{gnatchop}
10960 reads the specified file and generates one or more output files,
10961 containing one unit per file. The unit and the file name correspond,
10962 as required by GNAT.
10964 If you want to permanently restructure a set of ``foreign'' files so that
10965 they match the GNAT rules, and do the remaining development using the
10966 GNAT structure, you can simply use @command{gnatchop} once, generate the
10967 new set of files and work with them from that point on.
10969 Alternatively, if you want to keep your files in the ``foreign'' format,
10970 perhaps to maintain compatibility with some other Ada compilation
10971 system, you can set up a procedure where you use @command{gnatchop} each
10972 time you compile, regarding the source files that it writes as temporary
10973 files that you throw away.
10975 Note that if your file containing multiple units starts with a byte order
10976 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
10977 will each start with a copy of this BOM, meaning that they can be compiled
10978 automatically in UTF-8 mode without needing to specify an explicit encoding.
10980 @node Operating gnatchop in Compilation Mode
10981 @section Operating gnatchop in Compilation Mode
10984 The basic function of @code{gnatchop} is to take a file with multiple units
10985 and split it into separate files. The boundary between files is reasonably
10986 clear, except for the issue of comments and pragmas. In default mode, the
10987 rule is that any pragmas between units belong to the previous unit, except
10988 that configuration pragmas always belong to the following unit. Any comments
10989 belong to the following unit. These rules
10990 almost always result in the right choice of
10991 the split point without needing to mark it explicitly and most users will
10992 find this default to be what they want. In this default mode it is incorrect to
10993 submit a file containing only configuration pragmas, or one that ends in
10994 configuration pragmas, to @code{gnatchop}.
10996 However, using a special option to activate ``compilation mode'',
10998 can perform another function, which is to provide exactly the semantics
10999 required by the RM for handling of configuration pragmas in a compilation.
11000 In the absence of configuration pragmas (at the main file level), this
11001 option has no effect, but it causes such configuration pragmas to be handled
11002 in a quite different manner.
11004 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11005 only configuration pragmas, then this file is appended to the
11006 @file{gnat.adc} file in the current directory. This behavior provides
11007 the required behavior described in the RM for the actions to be taken
11008 on submitting such a file to the compiler, namely that these pragmas
11009 should apply to all subsequent compilations in the same compilation
11010 environment. Using GNAT, the current directory, possibly containing a
11011 @file{gnat.adc} file is the representation
11012 of a compilation environment. For more information on the
11013 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11015 Second, in compilation mode, if @code{gnatchop}
11016 is given a file that starts with
11017 configuration pragmas, and contains one or more units, then these
11018 configuration pragmas are prepended to each of the chopped files. This
11019 behavior provides the required behavior described in the RM for the
11020 actions to be taken on compiling such a file, namely that the pragmas
11021 apply to all units in the compilation, but not to subsequently compiled
11024 Finally, if configuration pragmas appear between units, they are appended
11025 to the previous unit. This results in the previous unit being illegal,
11026 since the compiler does not accept configuration pragmas that follow
11027 a unit. This provides the required RM behavior that forbids configuration
11028 pragmas other than those preceding the first compilation unit of a
11031 For most purposes, @code{gnatchop} will be used in default mode. The
11032 compilation mode described above is used only if you need exactly
11033 accurate behavior with respect to compilations, and you have files
11034 that contain multiple units and configuration pragmas. In this
11035 circumstance the use of @code{gnatchop} with the compilation mode
11036 switch provides the required behavior, and is for example the mode
11037 in which GNAT processes the ACVC tests.
11039 @node Command Line for gnatchop
11040 @section Command Line for @code{gnatchop}
11043 The @code{gnatchop} command has the form:
11046 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11051 The only required argument is the file name of the file to be chopped.
11052 There are no restrictions on the form of this file name. The file itself
11053 contains one or more Ada units, in normal GNAT format, concatenated
11054 together. As shown, more than one file may be presented to be chopped.
11056 When run in default mode, @code{gnatchop} generates one output file in
11057 the current directory for each unit in each of the files.
11059 @var{directory}, if specified, gives the name of the directory to which
11060 the output files will be written. If it is not specified, all files are
11061 written to the current directory.
11063 For example, given a
11064 file called @file{hellofiles} containing
11066 @smallexample @c ada
11071 with Text_IO; use Text_IO;
11074 Put_Line ("Hello");
11084 $ gnatchop ^hellofiles^HELLOFILES.^
11088 generates two files in the current directory, one called
11089 @file{hello.ads} containing the single line that is the procedure spec,
11090 and the other called @file{hello.adb} containing the remaining text. The
11091 original file is not affected. The generated files can be compiled in
11095 When gnatchop is invoked on a file that is empty or that contains only empty
11096 lines and/or comments, gnatchop will not fail, but will not produce any
11099 For example, given a
11100 file called @file{toto.txt} containing
11102 @smallexample @c ada
11114 $ gnatchop ^toto.txt^TOT.TXT^
11118 will not produce any new file and will result in the following warnings:
11121 toto.txt:1:01: warning: empty file, contains no compilation units
11122 no compilation units found
11123 no source files written
11126 @node Switches for gnatchop
11127 @section Switches for @code{gnatchop}
11130 @command{gnatchop} recognizes the following switches:
11136 @cindex @option{--version} @command{gnatchop}
11137 Display Copyright and version, then exit disregarding all other options.
11140 @cindex @option{--help} @command{gnatchop}
11141 If @option{--version} was not used, display usage, then exit disregarding
11144 @item ^-c^/COMPILATION^
11145 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11146 Causes @code{gnatchop} to operate in compilation mode, in which
11147 configuration pragmas are handled according to strict RM rules. See
11148 previous section for a full description of this mode.
11151 @item -gnat@var{xxx}
11152 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11153 used to parse the given file. Not all @var{xxx} options make sense,
11154 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11155 process a source file that uses Latin-2 coding for identifiers.
11159 Causes @code{gnatchop} to generate a brief help summary to the standard
11160 output file showing usage information.
11162 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11163 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11164 Limit generated file names to the specified number @code{mm}
11166 This is useful if the
11167 resulting set of files is required to be interoperable with systems
11168 which limit the length of file names.
11170 If no value is given, or
11171 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11172 a default of 39, suitable for OpenVMS Alpha
11173 Systems, is assumed
11176 No space is allowed between the @option{-k} and the numeric value. The numeric
11177 value may be omitted in which case a default of @option{-k8},
11179 with DOS-like file systems, is used. If no @option{-k} switch
11181 there is no limit on the length of file names.
11184 @item ^-p^/PRESERVE^
11185 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11186 Causes the file ^modification^creation^ time stamp of the input file to be
11187 preserved and used for the time stamp of the output file(s). This may be
11188 useful for preserving coherency of time stamps in an environment where
11189 @code{gnatchop} is used as part of a standard build process.
11192 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11193 Causes output of informational messages indicating the set of generated
11194 files to be suppressed. Warnings and error messages are unaffected.
11196 @item ^-r^/REFERENCE^
11197 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11198 @findex Source_Reference
11199 Generate @code{Source_Reference} pragmas. Use this switch if the output
11200 files are regarded as temporary and development is to be done in terms
11201 of the original unchopped file. This switch causes
11202 @code{Source_Reference} pragmas to be inserted into each of the
11203 generated files to refers back to the original file name and line number.
11204 The result is that all error messages refer back to the original
11206 In addition, the debugging information placed into the object file (when
11207 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11209 also refers back to this original file so that tools like profilers and
11210 debuggers will give information in terms of the original unchopped file.
11212 If the original file to be chopped itself contains
11213 a @code{Source_Reference}
11214 pragma referencing a third file, then gnatchop respects
11215 this pragma, and the generated @code{Source_Reference} pragmas
11216 in the chopped file refer to the original file, with appropriate
11217 line numbers. This is particularly useful when @code{gnatchop}
11218 is used in conjunction with @code{gnatprep} to compile files that
11219 contain preprocessing statements and multiple units.
11221 @item ^-v^/VERBOSE^
11222 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11223 Causes @code{gnatchop} to operate in verbose mode. The version
11224 number and copyright notice are output, as well as exact copies of
11225 the gnat1 commands spawned to obtain the chop control information.
11227 @item ^-w^/OVERWRITE^
11228 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11229 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11230 fatal error if there is already a file with the same name as a
11231 file it would otherwise output, in other words if the files to be
11232 chopped contain duplicated units. This switch bypasses this
11233 check, and causes all but the last instance of such duplicated
11234 units to be skipped.
11237 @item --GCC=@var{xxxx}
11238 @cindex @option{--GCC=} (@code{gnatchop})
11239 Specify the path of the GNAT parser to be used. When this switch is used,
11240 no attempt is made to add the prefix to the GNAT parser executable.
11244 @node Examples of gnatchop Usage
11245 @section Examples of @code{gnatchop} Usage
11249 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11252 @item gnatchop -w hello_s.ada prerelease/files
11255 Chops the source file @file{hello_s.ada}. The output files will be
11256 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11258 files with matching names in that directory (no files in the current
11259 directory are modified).
11261 @item gnatchop ^archive^ARCHIVE.^
11262 Chops the source file @file{^archive^ARCHIVE.^}
11263 into the current directory. One
11264 useful application of @code{gnatchop} is in sending sets of sources
11265 around, for example in email messages. The required sources are simply
11266 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11268 @command{gnatchop} is used at the other end to reconstitute the original
11271 @item gnatchop file1 file2 file3 direc
11272 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11273 the resulting files in the directory @file{direc}. Note that if any units
11274 occur more than once anywhere within this set of files, an error message
11275 is generated, and no files are written. To override this check, use the
11276 @option{^-w^/OVERWRITE^} switch,
11277 in which case the last occurrence in the last file will
11278 be the one that is output, and earlier duplicate occurrences for a given
11279 unit will be skipped.
11282 @node Configuration Pragmas
11283 @chapter Configuration Pragmas
11284 @cindex Configuration pragmas
11285 @cindex Pragmas, configuration
11288 Configuration pragmas include those pragmas described as
11289 such in the Ada Reference Manual, as well as
11290 implementation-dependent pragmas that are configuration pragmas.
11291 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11292 for details on these additional GNAT-specific configuration pragmas.
11293 Most notably, the pragma @code{Source_File_Name}, which allows
11294 specifying non-default names for source files, is a configuration
11295 pragma. The following is a complete list of configuration pragmas
11296 recognized by GNAT:
11308 Compile_Time_Warning
11310 Component_Alignment
11317 External_Name_Casing
11320 Float_Representation
11333 Priority_Specific_Dispatching
11336 Propagate_Exceptions
11339 Restricted_Run_Time
11341 Restrictions_Warnings
11344 Source_File_Name_Project
11347 Suppress_Exception_Locations
11348 Task_Dispatching_Policy
11354 Wide_Character_Encoding
11359 * Handling of Configuration Pragmas::
11360 * The Configuration Pragmas Files::
11363 @node Handling of Configuration Pragmas
11364 @section Handling of Configuration Pragmas
11366 Configuration pragmas may either appear at the start of a compilation
11367 unit, in which case they apply only to that unit, or they may apply to
11368 all compilations performed in a given compilation environment.
11370 GNAT also provides the @code{gnatchop} utility to provide an automatic
11371 way to handle configuration pragmas following the semantics for
11372 compilations (that is, files with multiple units), described in the RM.
11373 See @ref{Operating gnatchop in Compilation Mode} for details.
11374 However, for most purposes, it will be more convenient to edit the
11375 @file{gnat.adc} file that contains configuration pragmas directly,
11376 as described in the following section.
11378 @node The Configuration Pragmas Files
11379 @section The Configuration Pragmas Files
11380 @cindex @file{gnat.adc}
11383 In GNAT a compilation environment is defined by the current
11384 directory at the time that a compile command is given. This current
11385 directory is searched for a file whose name is @file{gnat.adc}. If
11386 this file is present, it is expected to contain one or more
11387 configuration pragmas that will be applied to the current compilation.
11388 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11391 Configuration pragmas may be entered into the @file{gnat.adc} file
11392 either by running @code{gnatchop} on a source file that consists only of
11393 configuration pragmas, or more conveniently by
11394 direct editing of the @file{gnat.adc} file, which is a standard format
11397 In addition to @file{gnat.adc}, additional files containing configuration
11398 pragmas may be applied to the current compilation using the switch
11399 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11400 contains only configuration pragmas. These configuration pragmas are
11401 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11402 is present and switch @option{-gnatA} is not used).
11404 It is allowed to specify several switches @option{-gnatec}, all of which
11405 will be taken into account.
11407 If you are using project file, a separate mechanism is provided using
11408 project attributes, see @ref{Specifying Configuration Pragmas} for more
11412 Of special interest to GNAT OpenVMS Alpha is the following
11413 configuration pragma:
11415 @smallexample @c ada
11417 pragma Extend_System (Aux_DEC);
11422 In the presence of this pragma, GNAT adds to the definition of the
11423 predefined package SYSTEM all the additional types and subprograms that are
11424 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11427 @node Handling Arbitrary File Naming Conventions Using gnatname
11428 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11429 @cindex Arbitrary File Naming Conventions
11432 * Arbitrary File Naming Conventions::
11433 * Running gnatname::
11434 * Switches for gnatname::
11435 * Examples of gnatname Usage::
11438 @node Arbitrary File Naming Conventions
11439 @section Arbitrary File Naming Conventions
11442 The GNAT compiler must be able to know the source file name of a compilation
11443 unit. When using the standard GNAT default file naming conventions
11444 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11445 does not need additional information.
11448 When the source file names do not follow the standard GNAT default file naming
11449 conventions, the GNAT compiler must be given additional information through
11450 a configuration pragmas file (@pxref{Configuration Pragmas})
11452 When the non-standard file naming conventions are well-defined,
11453 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11454 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11455 if the file naming conventions are irregular or arbitrary, a number
11456 of pragma @code{Source_File_Name} for individual compilation units
11458 To help maintain the correspondence between compilation unit names and
11459 source file names within the compiler,
11460 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11463 @node Running gnatname
11464 @section Running @code{gnatname}
11467 The usual form of the @code{gnatname} command is
11470 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11471 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11475 All of the arguments are optional. If invoked without any argument,
11476 @code{gnatname} will display its usage.
11479 When used with at least one naming pattern, @code{gnatname} will attempt to
11480 find all the compilation units in files that follow at least one of the
11481 naming patterns. To find these compilation units,
11482 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11486 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11487 Each Naming Pattern is enclosed between double quotes.
11488 A Naming Pattern is a regular expression similar to the wildcard patterns
11489 used in file names by the Unix shells or the DOS prompt.
11492 @code{gnatname} may be called with several sections of directories/patterns.
11493 Sections are separated by switch @code{--and}. In each section, there must be
11494 at least one pattern. If no directory is specified in a section, the current
11495 directory (or the project directory is @code{-P} is used) is implied.
11496 The options other that the directory switches and the patterns apply globally
11497 even if they are in different sections.
11500 Examples of Naming Patterns are
11509 For a more complete description of the syntax of Naming Patterns,
11510 see the second kind of regular expressions described in @file{g-regexp.ads}
11511 (the ``Glob'' regular expressions).
11514 When invoked with no switch @code{-P}, @code{gnatname} will create a
11515 configuration pragmas file @file{gnat.adc} in the current working directory,
11516 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11519 @node Switches for gnatname
11520 @section Switches for @code{gnatname}
11523 Switches for @code{gnatname} must precede any specified Naming Pattern.
11526 You may specify any of the following switches to @code{gnatname}:
11532 @cindex @option{--version} @command{gnatname}
11533 Display Copyright and version, then exit disregarding all other options.
11536 @cindex @option{--help} @command{gnatname}
11537 If @option{--version} was not used, display usage, then exit disregarding
11541 Start another section of directories/patterns.
11543 @item ^-c^/CONFIG_FILE=^@file{file}
11544 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11545 Create a configuration pragmas file @file{file} (instead of the default
11548 There may be zero, one or more space between @option{-c} and
11551 @file{file} may include directory information. @file{file} must be
11552 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11553 When a switch @option{^-c^/CONFIG_FILE^} is
11554 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11556 @item ^-d^/SOURCE_DIRS=^@file{dir}
11557 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11558 Look for source files in directory @file{dir}. There may be zero, one or more
11559 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11560 When a switch @option{^-d^/SOURCE_DIRS^}
11561 is specified, the current working directory will not be searched for source
11562 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11563 or @option{^-D^/DIR_FILES^} switch.
11564 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11565 If @file{dir} is a relative path, it is relative to the directory of
11566 the configuration pragmas file specified with switch
11567 @option{^-c^/CONFIG_FILE^},
11568 or to the directory of the project file specified with switch
11569 @option{^-P^/PROJECT_FILE^} or,
11570 if neither switch @option{^-c^/CONFIG_FILE^}
11571 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11572 current working directory. The directory
11573 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11575 @item ^-D^/DIRS_FILE=^@file{file}
11576 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11577 Look for source files in all directories listed in text file @file{file}.
11578 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11580 @file{file} must be an existing, readable text file.
11581 Each nonempty line in @file{file} must be a directory.
11582 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11583 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11586 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11587 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11588 Foreign patterns. Using this switch, it is possible to add sources of languages
11589 other than Ada to the list of sources of a project file.
11590 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11593 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11596 will look for Ada units in all files with the @file{.ada} extension,
11597 and will add to the list of file for project @file{prj.gpr} the C files
11598 with extension @file{.^c^C^}.
11601 @cindex @option{^-h^/HELP^} (@code{gnatname})
11602 Output usage (help) information. The output is written to @file{stdout}.
11604 @item ^-P^/PROJECT_FILE=^@file{proj}
11605 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11606 Create or update project file @file{proj}. There may be zero, one or more space
11607 between @option{-P} and @file{proj}. @file{proj} may include directory
11608 information. @file{proj} must be writable.
11609 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11610 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11611 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11613 @item ^-v^/VERBOSE^
11614 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11615 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11616 This includes name of the file written, the name of the directories to search
11617 and, for each file in those directories whose name matches at least one of
11618 the Naming Patterns, an indication of whether the file contains a unit,
11619 and if so the name of the unit.
11621 @item ^-v -v^/VERBOSE /VERBOSE^
11622 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11623 Very Verbose mode. In addition to the output produced in verbose mode,
11624 for each file in the searched directories whose name matches none of
11625 the Naming Patterns, an indication is given that there is no match.
11627 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11628 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11629 Excluded patterns. Using this switch, it is possible to exclude some files
11630 that would match the name patterns. For example,
11632 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11635 will look for Ada units in all files with the @file{.ada} extension,
11636 except those whose names end with @file{_nt.ada}.
11640 @node Examples of gnatname Usage
11641 @section Examples of @code{gnatname} Usage
11645 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11651 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11656 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11657 and be writable. In addition, the directory
11658 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11659 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11662 Note the optional spaces after @option{-c} and @option{-d}.
11667 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11668 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11671 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11672 /EXCLUDED_PATTERN=*_nt_body.ada
11673 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11674 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11678 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11679 even in conjunction with one or several switches
11680 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11681 are used in this example.
11683 @c *****************************************
11684 @c * G N A T P r o j e c t M a n a g e r *
11685 @c *****************************************
11686 @node GNAT Project Manager
11687 @chapter GNAT Project Manager
11691 * Examples of Project Files::
11692 * Project File Syntax::
11693 * Objects and Sources in Project Files::
11694 * Importing Projects::
11695 * Project Extension::
11696 * Project Hierarchy Extension::
11697 * External References in Project Files::
11698 * Packages in Project Files::
11699 * Variables from Imported Projects::
11701 * Library Projects::
11702 * Stand-alone Library Projects::
11703 * Switches Related to Project Files::
11704 * Tools Supporting Project Files::
11705 * An Extended Example::
11706 * Project File Complete Syntax::
11709 @c ****************
11710 @c * Introduction *
11711 @c ****************
11714 @section Introduction
11717 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11718 you to manage complex builds involving a number of source files, directories,
11719 and compilation options for different system configurations. In particular,
11720 project files allow you to specify:
11723 The directory or set of directories containing the source files, and/or the
11724 names of the specific source files themselves
11726 The directory in which the compiler's output
11727 (@file{ALI} files, object files, tree files) is to be placed
11729 The directory in which the executable programs is to be placed
11731 ^Switch^Switch^ settings for any of the project-enabled tools
11732 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11733 @code{gnatfind}); you can apply these settings either globally or to individual
11736 The source files containing the main subprogram(s) to be built
11738 The source programming language(s) (currently Ada and/or C)
11740 Source file naming conventions; you can specify these either globally or for
11741 individual compilation units
11748 @node Project Files
11749 @subsection Project Files
11752 Project files are written in a syntax close to that of Ada, using familiar
11753 notions such as packages, context clauses, declarations, default values,
11754 assignments, and inheritance. Finally, project files can be built
11755 hierarchically from other project files, simplifying complex system
11756 integration and project reuse.
11758 A @dfn{project} is a specific set of values for various compilation properties.
11759 The settings for a given project are described by means of
11760 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11761 Property values in project files are either strings or lists of strings.
11762 Properties that are not explicitly set receive default values. A project
11763 file may interrogate the values of @dfn{external variables} (user-defined
11764 command-line switches or environment variables), and it may specify property
11765 settings conditionally, based on the value of such variables.
11767 In simple cases, a project's source files depend only on other source files
11768 in the same project, or on the predefined libraries. (@emph{Dependence} is
11770 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11771 the Project Manager also allows more sophisticated arrangements,
11772 where the source files in one project depend on source files in other
11776 One project can @emph{import} other projects containing needed source files.
11778 You can organize GNAT projects in a hierarchy: a @emph{child} project
11779 can extend a @emph{parent} project, inheriting the parent's source files and
11780 optionally overriding any of them with alternative versions
11784 More generally, the Project Manager lets you structure large development
11785 efforts into hierarchical subsystems, where build decisions are delegated
11786 to the subsystem level, and thus different compilation environments
11787 (^switch^switch^ settings) used for different subsystems.
11789 The Project Manager is invoked through the
11790 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11791 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11793 There may be zero, one or more spaces between @option{-P} and
11794 @option{@emph{projectfile}}.
11796 If you want to define (on the command line) an external variable that is
11797 queried by the project file, you must use the
11798 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11799 The Project Manager parses and interprets the project file, and drives the
11800 invoked tool based on the project settings.
11802 The Project Manager supports a wide range of development strategies,
11803 for systems of all sizes. Here are some typical practices that are
11807 Using a common set of source files, but generating object files in different
11808 directories via different ^switch^switch^ settings
11810 Using a mostly-shared set of source files, but with different versions of
11815 The destination of an executable can be controlled inside a project file
11816 using the @option{^-o^-o^}
11818 In the absence of such a ^switch^switch^ either inside
11819 the project file or on the command line, any executable files generated by
11820 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11821 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11822 in the object directory of the project.
11824 You can use project files to achieve some of the effects of a source
11825 versioning system (for example, defining separate projects for
11826 the different sets of sources that comprise different releases) but the
11827 Project Manager is independent of any source configuration management tools
11828 that might be used by the developers.
11830 The next section introduces the main features of GNAT's project facility
11831 through a sequence of examples; subsequent sections will present the syntax
11832 and semantics in more detail. A more formal description of the project
11833 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11836 @c *****************************
11837 @c * Examples of Project Files *
11838 @c *****************************
11840 @node Examples of Project Files
11841 @section Examples of Project Files
11843 This section illustrates some of the typical uses of project files and
11844 explains their basic structure and behavior.
11847 * Common Sources with Different ^Switches^Switches^ and Directories::
11848 * Using External Variables::
11849 * Importing Other Projects::
11850 * Extending a Project::
11853 @node Common Sources with Different ^Switches^Switches^ and Directories
11854 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11858 * Specifying the Object Directory::
11859 * Specifying the Exec Directory::
11860 * Project File Packages::
11861 * Specifying ^Switch^Switch^ Settings::
11862 * Main Subprograms::
11863 * Executable File Names::
11864 * Source File Naming Conventions::
11865 * Source Language(s)::
11869 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11870 @file{proc.adb} are in the @file{/common} directory. The file
11871 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11872 package @code{Pack}. We want to compile these source files under two sets
11873 of ^switches^switches^:
11876 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11877 and the @option{^-gnata^-gnata^},
11878 @option{^-gnato^-gnato^},
11879 and @option{^-gnatE^-gnatE^} switches to the
11880 compiler; the compiler's output is to appear in @file{/common/debug}
11882 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11883 to the compiler; the compiler's output is to appear in @file{/common/release}
11887 The GNAT project files shown below, respectively @file{debug.gpr} and
11888 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11901 ^/common/debug^[COMMON.DEBUG]^
11906 ^/common/release^[COMMON.RELEASE]^
11911 Here are the corresponding project files:
11913 @smallexample @c projectfile
11916 for Object_Dir use "debug";
11917 for Main use ("proc");
11920 for ^Default_Switches^Default_Switches^ ("Ada")
11922 for Executable ("proc.adb") use "proc1";
11927 package Compiler is
11928 for ^Default_Switches^Default_Switches^ ("Ada")
11929 use ("-fstack-check",
11932 "^-gnatE^-gnatE^");
11938 @smallexample @c projectfile
11941 for Object_Dir use "release";
11942 for Exec_Dir use ".";
11943 for Main use ("proc");
11945 package Compiler is
11946 for ^Default_Switches^Default_Switches^ ("Ada")
11954 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11955 insensitive), and analogously the project defined by @file{release.gpr} is
11956 @code{"Release"}. For consistency the file should have the same name as the
11957 project, and the project file's extension should be @code{"gpr"}. These
11958 conventions are not required, but a warning is issued if they are not followed.
11960 If the current directory is @file{^/temp^[TEMP]^}, then the command
11962 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11966 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11967 as well as the @code{^proc1^PROC1.EXE^} executable,
11968 using the ^switch^switch^ settings defined in the project file.
11970 Likewise, the command
11972 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11976 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11977 and the @code{^proc^PROC.EXE^}
11978 executable in @file{^/common^[COMMON]^},
11979 using the ^switch^switch^ settings from the project file.
11982 @unnumberedsubsubsec Source Files
11985 If a project file does not explicitly specify a set of source directories or
11986 a set of source files, then by default the project's source files are the
11987 Ada source files in the project file directory. Thus @file{pack.ads},
11988 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11990 @node Specifying the Object Directory
11991 @unnumberedsubsubsec Specifying the Object Directory
11994 Several project properties are modeled by Ada-style @emph{attributes};
11995 a property is defined by supplying the equivalent of an Ada attribute
11996 definition clause in the project file.
11997 A project's object directory is another such a property; the corresponding
11998 attribute is @code{Object_Dir}, and its value is also a string expression,
11999 specified either as absolute or relative. In the later case,
12000 it is relative to the project file directory. Thus the compiler's
12001 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
12002 (for the @code{Debug} project)
12003 and to @file{^/common/release^[COMMON.RELEASE]^}
12004 (for the @code{Release} project).
12005 If @code{Object_Dir} is not specified, then the default is the project file
12008 @node Specifying the Exec Directory
12009 @unnumberedsubsubsec Specifying the Exec Directory
12012 A project's exec directory is another property; the corresponding
12013 attribute is @code{Exec_Dir}, and its value is also a string expression,
12014 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12015 then the default is the object directory (which may also be the project file
12016 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12017 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12018 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12019 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12021 @node Project File Packages
12022 @unnumberedsubsubsec Project File Packages
12025 A GNAT tool that is integrated with the Project Manager is modeled by a
12026 corresponding package in the project file. In the example above,
12027 The @code{Debug} project defines the packages @code{Builder}
12028 (for @command{gnatmake}) and @code{Compiler};
12029 the @code{Release} project defines only the @code{Compiler} package.
12031 The Ada-like package syntax is not to be taken literally. Although packages in
12032 project files bear a surface resemblance to packages in Ada source code, the
12033 notation is simply a way to convey a grouping of properties for a named
12034 entity. Indeed, the package names permitted in project files are restricted
12035 to a predefined set, corresponding to the project-aware tools, and the contents
12036 of packages are limited to a small set of constructs.
12037 The packages in the example above contain attribute definitions.
12039 @node Specifying ^Switch^Switch^ Settings
12040 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12043 ^Switch^Switch^ settings for a project-aware tool can be specified through
12044 attributes in the package that corresponds to the tool.
12045 The example above illustrates one of the relevant attributes,
12046 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12047 in both project files.
12048 Unlike simple attributes like @code{Source_Dirs},
12049 @code{^Default_Switches^Default_Switches^} is
12050 known as an @emph{associative array}. When you define this attribute, you must
12051 supply an ``index'' (a literal string), and the effect of the attribute
12052 definition is to set the value of the array at the specified index.
12053 For the @code{^Default_Switches^Default_Switches^} attribute,
12054 the index is a programming language (in our case, Ada),
12055 and the value specified (after @code{use}) must be a list
12056 of string expressions.
12058 The attributes permitted in project files are restricted to a predefined set.
12059 Some may appear at project level, others in packages.
12060 For any attribute that is an associative array, the index must always be a
12061 literal string, but the restrictions on this string (e.g., a file name or a
12062 language name) depend on the individual attribute.
12063 Also depending on the attribute, its specified value will need to be either a
12064 string or a string list.
12066 In the @code{Debug} project, we set the switches for two tools,
12067 @command{gnatmake} and the compiler, and thus we include the two corresponding
12068 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12069 attribute with index @code{"Ada"}.
12070 Note that the package corresponding to
12071 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12072 similar, but only includes the @code{Compiler} package.
12074 In project @code{Debug} above, the ^switches^switches^ starting with
12075 @option{-gnat} that are specified in package @code{Compiler}
12076 could have been placed in package @code{Builder}, since @command{gnatmake}
12077 transmits all such ^switches^switches^ to the compiler.
12079 @node Main Subprograms
12080 @unnumberedsubsubsec Main Subprograms
12083 One of the specifiable properties of a project is a list of files that contain
12084 main subprograms. This property is captured in the @code{Main} attribute,
12085 whose value is a list of strings. If a project defines the @code{Main}
12086 attribute, it is not necessary to identify the main subprogram(s) when
12087 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12089 @node Executable File Names
12090 @unnumberedsubsubsec Executable File Names
12093 By default, the executable file name corresponding to a main source is
12094 deduced from the main source file name. Through the attributes
12095 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12096 it is possible to change this default.
12097 In project @code{Debug} above, the executable file name
12098 for main source @file{^proc.adb^PROC.ADB^} is
12099 @file{^proc1^PROC1.EXE^}.
12100 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12101 of the executable files, when no attribute @code{Executable} applies:
12102 its value replace the platform-specific executable suffix.
12103 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12104 specify a non-default executable file name when several mains are built at once
12105 in a single @command{gnatmake} command.
12107 @node Source File Naming Conventions
12108 @unnumberedsubsubsec Source File Naming Conventions
12111 Since the project files above do not specify any source file naming
12112 conventions, the GNAT defaults are used. The mechanism for defining source
12113 file naming conventions -- a package named @code{Naming} --
12114 is described below (@pxref{Naming Schemes}).
12116 @node Source Language(s)
12117 @unnumberedsubsubsec Source Language(s)
12120 Since the project files do not specify a @code{Languages} attribute, by
12121 default the GNAT tools assume that the language of the project file is Ada.
12122 More generally, a project can comprise source files
12123 in Ada, C, and/or other languages.
12125 @node Using External Variables
12126 @subsection Using External Variables
12129 Instead of supplying different project files for debug and release, we can
12130 define a single project file that queries an external variable (set either
12131 on the command line or via an ^environment variable^logical name^) in order to
12132 conditionally define the appropriate settings. Again, assume that the
12133 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12134 located in directory @file{^/common^[COMMON]^}. The following project file,
12135 @file{build.gpr}, queries the external variable named @code{STYLE} and
12136 defines an object directory and ^switch^switch^ settings based on whether
12137 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12138 the default is @code{"deb"}.
12140 @smallexample @c projectfile
12143 for Main use ("proc");
12145 type Style_Type is ("deb", "rel");
12146 Style : Style_Type := external ("STYLE", "deb");
12150 for Object_Dir use "debug";
12153 for Object_Dir use "release";
12154 for Exec_Dir use ".";
12163 for ^Default_Switches^Default_Switches^ ("Ada")
12165 for Executable ("proc") use "proc1";
12174 package Compiler is
12178 for ^Default_Switches^Default_Switches^ ("Ada")
12179 use ("^-gnata^-gnata^",
12181 "^-gnatE^-gnatE^");
12184 for ^Default_Switches^Default_Switches^ ("Ada")
12195 @code{Style_Type} is an example of a @emph{string type}, which is the project
12196 file analog of an Ada enumeration type but whose components are string literals
12197 rather than identifiers. @code{Style} is declared as a variable of this type.
12199 The form @code{external("STYLE", "deb")} is known as an
12200 @emph{external reference}; its first argument is the name of an
12201 @emph{external variable}, and the second argument is a default value to be
12202 used if the external variable doesn't exist. You can define an external
12203 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12204 or you can use ^an environment variable^a logical name^
12205 as an external variable.
12207 Each @code{case} construct is expanded by the Project Manager based on the
12208 value of @code{Style}. Thus the command
12211 gnatmake -P/common/build.gpr -XSTYLE=deb
12217 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12222 is equivalent to the @command{gnatmake} invocation using the project file
12223 @file{debug.gpr} in the earlier example. So is the command
12225 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12229 since @code{"deb"} is the default for @code{STYLE}.
12235 gnatmake -P/common/build.gpr -XSTYLE=rel
12241 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12246 is equivalent to the @command{gnatmake} invocation using the project file
12247 @file{release.gpr} in the earlier example.
12249 @node Importing Other Projects
12250 @subsection Importing Other Projects
12251 @cindex @code{ADA_PROJECT_PATH}
12254 A compilation unit in a source file in one project may depend on compilation
12255 units in source files in other projects. To compile this unit under
12256 control of a project file, the
12257 dependent project must @emph{import} the projects containing the needed source
12259 This effect is obtained using syntax similar to an Ada @code{with} clause,
12260 but where @code{with}ed entities are strings that denote project files.
12262 As an example, suppose that the two projects @code{GUI_Proj} and
12263 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12264 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12265 and @file{^/comm^[COMM]^}, respectively.
12266 Suppose that the source files for @code{GUI_Proj} are
12267 @file{gui.ads} and @file{gui.adb}, and that the source files for
12268 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12269 files is located in its respective project file directory. Schematically:
12288 We want to develop an application in directory @file{^/app^[APP]^} that
12289 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12290 the corresponding project files (e.g.@: the ^switch^switch^ settings
12291 and object directory).
12292 Skeletal code for a main procedure might be something like the following:
12294 @smallexample @c ada
12297 procedure App_Main is
12306 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12309 @smallexample @c projectfile
12311 with "/gui/gui_proj", "/comm/comm_proj";
12312 project App_Proj is
12313 for Main use ("app_main");
12319 Building an executable is achieved through the command:
12321 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12324 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12325 in the directory where @file{app_proj.gpr} resides.
12327 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12328 (as illustrated above) the @code{with} clause can omit the extension.
12330 Our example specified an absolute path for each imported project file.
12331 Alternatively, the directory name of an imported object can be omitted
12335 The imported project file is in the same directory as the importing project
12338 You have defined ^an environment variable^a logical name^
12339 that includes the directory containing
12340 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
12341 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12342 directory names separated by colons (semicolons on Windows).
12346 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12347 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12350 @smallexample @c projectfile
12352 with "gui_proj", "comm_proj";
12353 project App_Proj is
12354 for Main use ("app_main");
12360 Importing other projects can create ambiguities.
12361 For example, the same unit might be present in different imported projects, or
12362 it might be present in both the importing project and in an imported project.
12363 Both of these conditions are errors. Note that in the current version of
12364 the Project Manager, it is illegal to have an ambiguous unit even if the
12365 unit is never referenced by the importing project. This restriction may be
12366 relaxed in a future release.
12368 @node Extending a Project
12369 @subsection Extending a Project
12372 In large software systems it is common to have multiple
12373 implementations of a common interface; in Ada terms, multiple versions of a
12374 package body for the same spec. For example, one implementation
12375 might be safe for use in tasking programs, while another might only be used
12376 in sequential applications. This can be modeled in GNAT using the concept
12377 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12378 another project (the ``parent'') then by default all source files of the
12379 parent project are inherited by the child, but the child project can
12380 override any of the parent's source files with new versions, and can also
12381 add new files. This facility is the project analog of a type extension in
12382 Object-Oriented Programming. Project hierarchies are permitted (a child
12383 project may be the parent of yet another project), and a project that
12384 inherits one project can also import other projects.
12386 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12387 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12388 @file{pack.adb}, and @file{proc.adb}:
12401 Note that the project file can simply be empty (that is, no attribute or
12402 package is defined):
12404 @smallexample @c projectfile
12406 project Seq_Proj is
12412 implying that its source files are all the Ada source files in the project
12415 Suppose we want to supply an alternate version of @file{pack.adb}, in
12416 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12417 @file{pack.ads} and @file{proc.adb}. We can define a project
12418 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12422 ^/tasking^[TASKING]^
12428 project Tasking_Proj extends "/seq/seq_proj" is
12434 The version of @file{pack.adb} used in a build depends on which project file
12437 Note that we could have obtained the desired behavior using project import
12438 rather than project inheritance; a @code{base} project would contain the
12439 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12440 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12441 would import @code{base} and add a different version of @file{pack.adb}. The
12442 choice depends on whether other sources in the original project need to be
12443 overridden. If they do, then project extension is necessary, otherwise,
12444 importing is sufficient.
12447 In a project file that extends another project file, it is possible to
12448 indicate that an inherited source is not part of the sources of the extending
12449 project. This is necessary sometimes when a package spec has been overloaded
12450 and no longer requires a body: in this case, it is necessary to indicate that
12451 the inherited body is not part of the sources of the project, otherwise there
12452 will be a compilation error when compiling the spec.
12454 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12455 Its value is a string list: a list of file names. It is also possible to use
12456 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12457 the file name of a text file containing a list of file names, one per line.
12459 @smallexample @c @projectfile
12460 project B extends "a" is
12461 for Source_Files use ("pkg.ads");
12462 -- New spec of Pkg does not need a completion
12463 for Excluded_Source_Files use ("pkg.adb");
12467 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12468 is still needed: if it is possible to build using @command{gnatmake} when such
12469 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12470 it is possible to remove the source completely from a system that includes
12473 @c ***********************
12474 @c * Project File Syntax *
12475 @c ***********************
12477 @node Project File Syntax
12478 @section Project File Syntax
12482 * Qualified Projects::
12488 * Associative Array Attributes::
12489 * case Constructions::
12493 This section describes the structure of project files.
12495 A project may be an @emph{independent project}, entirely defined by a single
12496 project file. Any Ada source file in an independent project depends only
12497 on the predefined library and other Ada source files in the same project.
12500 A project may also @dfn{depend on} other projects, in either or both of
12501 the following ways:
12503 @item It may import any number of projects
12504 @item It may extend at most one other project
12508 The dependence relation is a directed acyclic graph (the subgraph reflecting
12509 the ``extends'' relation is a tree).
12511 A project's @dfn{immediate sources} are the source files directly defined by
12512 that project, either implicitly by residing in the project file's directory,
12513 or explicitly through any of the source-related attributes described below.
12514 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12515 of @var{proj} together with the immediate sources (unless overridden) of any
12516 project on which @var{proj} depends (either directly or indirectly).
12519 @subsection Basic Syntax
12522 As seen in the earlier examples, project files have an Ada-like syntax.
12523 The minimal project file is:
12524 @smallexample @c projectfile
12533 The identifier @code{Empty} is the name of the project.
12534 This project name must be present after the reserved
12535 word @code{end} at the end of the project file, followed by a semi-colon.
12537 Any name in a project file, such as the project name or a variable name,
12538 has the same syntax as an Ada identifier.
12540 The reserved words of project files are the Ada 95 reserved words plus
12541 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12542 reserved words currently used in project file syntax are:
12578 Comments in project files have the same syntax as in Ada, two consecutive
12579 hyphens through the end of the line.
12581 @node Qualified Projects
12582 @subsection Qualified Projects
12585 Before the reserved @code{project}, there may be one or two "qualifiers", that
12586 is identifiers or other reserved words, to qualify the project.
12588 The current list of qualifiers is:
12592 @code{abstract}: qualify a project with no sources. A qualified abstract
12593 project must either have no declaration of attributes @code{Source_Dirs},
12594 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12595 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12596 as empty. If it extends another project, the project it extends must also be a
12597 qualified abstract project.
12600 @code{standard}: a standard project is a non library project with sources.
12603 @code{aggregate}: for future extension
12606 @code{aggregate library}: for future extension
12609 @code{library}: a library project must declare both attributes
12610 @code{Library_Name} and @code{Library_Dir}.
12613 @code{configuration}: a configuration project cannot be in a project tree.
12617 @subsection Packages
12620 A project file may contain @emph{packages}. The name of a package must be one
12621 of the identifiers from the following list. A package
12622 with a given name may only appear once in a project file. Package names are
12623 case insensitive. The following package names are legal:
12639 @code{Cross_Reference}
12643 @code{Pretty_Printer}
12653 @code{Language_Processing}
12657 In its simplest form, a package may be empty:
12659 @smallexample @c projectfile
12669 A package may contain @emph{attribute declarations},
12670 @emph{variable declarations} and @emph{case constructions}, as will be
12673 When there is ambiguity between a project name and a package name,
12674 the name always designates the project. To avoid possible confusion, it is
12675 always a good idea to avoid naming a project with one of the
12676 names allowed for packages or any name that starts with @code{gnat}.
12679 @subsection Expressions
12682 An @emph{expression} is either a @emph{string expression} or a
12683 @emph{string list expression}.
12685 A @emph{string expression} is either a @emph{simple string expression} or a
12686 @emph{compound string expression}.
12688 A @emph{simple string expression} is one of the following:
12690 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12691 @item A string-valued variable reference (@pxref{Variables})
12692 @item A string-valued attribute reference (@pxref{Attributes})
12693 @item An external reference (@pxref{External References in Project Files})
12697 A @emph{compound string expression} is a concatenation of string expressions,
12698 using the operator @code{"&"}
12700 Path & "/" & File_Name & ".ads"
12704 A @emph{string list expression} is either a
12705 @emph{simple string list expression} or a
12706 @emph{compound string list expression}.
12708 A @emph{simple string list expression} is one of the following:
12710 @item A parenthesized list of zero or more string expressions,
12711 separated by commas
12713 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12716 @item A string list-valued variable reference
12717 @item A string list-valued attribute reference
12721 A @emph{compound string list expression} is the concatenation (using
12722 @code{"&"}) of a simple string list expression and an expression. Note that
12723 each term in a compound string list expression, except the first, may be
12724 either a string expression or a string list expression.
12726 @smallexample @c projectfile
12728 File_Name_List := () & File_Name; -- One string in this list
12729 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12731 Big_List := File_Name_List & Extended_File_Name_List;
12732 -- Concatenation of two string lists: three strings
12733 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12734 -- Illegal: must start with a string list
12739 @subsection String Types
12742 A @emph{string type declaration} introduces a discrete set of string literals.
12743 If a string variable is declared to have this type, its value
12744 is restricted to the given set of literals.
12746 Here is an example of a string type declaration:
12748 @smallexample @c projectfile
12749 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12753 Variables of a string type are called @emph{typed variables}; all other
12754 variables are called @emph{untyped variables}. Typed variables are
12755 particularly useful in @code{case} constructions, to support conditional
12756 attribute declarations.
12757 (@pxref{case Constructions}).
12759 The string literals in the list are case sensitive and must all be different.
12760 They may include any graphic characters allowed in Ada, including spaces.
12762 A string type may only be declared at the project level, not inside a package.
12764 A string type may be referenced by its name if it has been declared in the same
12765 project file, or by an expanded name whose prefix is the name of the project
12766 in which it is declared.
12769 @subsection Variables
12772 A variable may be declared at the project file level, or within a package.
12773 Here are some examples of variable declarations:
12775 @smallexample @c projectfile
12777 This_OS : OS := external ("OS"); -- a typed variable declaration
12778 That_OS := "GNU/Linux"; -- an untyped variable declaration
12783 The syntax of a @emph{typed variable declaration} is identical to the Ada
12784 syntax for an object declaration. By contrast, the syntax of an untyped
12785 variable declaration is identical to an Ada assignment statement. In fact,
12786 variable declarations in project files have some of the characteristics of
12787 an assignment, in that successive declarations for the same variable are
12788 allowed. Untyped variable declarations do establish the expected kind of the
12789 variable (string or string list), and successive declarations for it must
12790 respect the initial kind.
12793 A string variable declaration (typed or untyped) declares a variable
12794 whose value is a string. This variable may be used as a string expression.
12795 @smallexample @c projectfile
12796 File_Name := "readme.txt";
12797 Saved_File_Name := File_Name & ".saved";
12801 A string list variable declaration declares a variable whose value is a list
12802 of strings. The list may contain any number (zero or more) of strings.
12804 @smallexample @c projectfile
12806 List_With_One_Element := ("^-gnaty^-gnaty^");
12807 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12808 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12809 "pack2.ada", "util_.ada", "util.ada");
12813 The same typed variable may not be declared more than once at project level,
12814 and it may not be declared more than once in any package; it is in effect
12817 The same untyped variable may be declared several times. Declarations are
12818 elaborated in the order in which they appear, so the new value replaces
12819 the old one, and any subsequent reference to the variable uses the new value.
12820 However, as noted above, if a variable has been declared as a string, all
12822 declarations must give it a string value. Similarly, if a variable has
12823 been declared as a string list, all subsequent declarations
12824 must give it a string list value.
12826 A @emph{variable reference} may take several forms:
12829 @item The simple variable name, for a variable in the current package (if any)
12830 or in the current project
12831 @item An expanded name, whose prefix is a context name.
12835 A @emph{context} may be one of the following:
12838 @item The name of an existing package in the current project
12839 @item The name of an imported project of the current project
12840 @item The name of an ancestor project (i.e., a project extended by the current
12841 project, either directly or indirectly)
12842 @item An expanded name whose prefix is an imported/parent project name, and
12843 whose selector is a package name in that project.
12847 A variable reference may be used in an expression.
12850 @subsection Attributes
12853 A project (and its packages) may have @emph{attributes} that define
12854 the project's properties. Some attributes have values that are strings;
12855 others have values that are string lists.
12857 There are two categories of attributes: @emph{simple attributes}
12858 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12860 Legal project attribute names, and attribute names for each legal package are
12861 listed below. Attributes names are case-insensitive.
12863 The following attributes are defined on projects (all are simple attributes):
12865 @multitable @columnfractions .4 .3
12866 @item @emph{Attribute Name}
12868 @item @code{Source_Files}
12870 @item @code{Source_Dirs}
12872 @item @code{Source_List_File}
12874 @item @code{Object_Dir}
12876 @item @code{Exec_Dir}
12878 @item @code{Excluded_Source_Dirs}
12880 @item @code{Excluded_Source_Files}
12882 @item @code{Excluded_Source_List_File}
12884 @item @code{Languages}
12888 @item @code{Library_Dir}
12890 @item @code{Library_Name}
12892 @item @code{Library_Kind}
12894 @item @code{Library_Version}
12896 @item @code{Library_Interface}
12898 @item @code{Library_Auto_Init}
12900 @item @code{Library_Options}
12902 @item @code{Library_Src_Dir}
12904 @item @code{Library_ALI_Dir}
12906 @item @code{Library_GCC}
12908 @item @code{Library_Symbol_File}
12910 @item @code{Library_Symbol_Policy}
12912 @item @code{Library_Reference_Symbol_File}
12914 @item @code{Externally_Built}
12919 The following attributes are defined for package @code{Naming}
12920 (@pxref{Naming Schemes}):
12922 @multitable @columnfractions .4 .2 .2 .2
12923 @item Attribute Name @tab Category @tab Index @tab Value
12924 @item @code{Spec_Suffix}
12925 @tab associative array
12928 @item @code{Body_Suffix}
12929 @tab associative array
12932 @item @code{Separate_Suffix}
12933 @tab simple attribute
12936 @item @code{Casing}
12937 @tab simple attribute
12940 @item @code{Dot_Replacement}
12941 @tab simple attribute
12945 @tab associative array
12949 @tab associative array
12952 @item @code{Specification_Exceptions}
12953 @tab associative array
12956 @item @code{Implementation_Exceptions}
12957 @tab associative array
12963 The following attributes are defined for packages @code{Builder},
12964 @code{Compiler}, @code{Binder},
12965 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12966 (@pxref{^Switches^Switches^ and Project Files}).
12968 @multitable @columnfractions .4 .2 .2 .2
12969 @item Attribute Name @tab Category @tab Index @tab Value
12970 @item @code{^Default_Switches^Default_Switches^}
12971 @tab associative array
12974 @item @code{^Switches^Switches^}
12975 @tab associative array
12981 In addition, package @code{Compiler} has a single string attribute
12982 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12983 string attribute @code{Global_Configuration_Pragmas}.
12986 Each simple attribute has a default value: the empty string (for string-valued
12987 attributes) and the empty list (for string list-valued attributes).
12989 An attribute declaration defines a new value for an attribute.
12991 Examples of simple attribute declarations:
12993 @smallexample @c projectfile
12994 for Object_Dir use "objects";
12995 for Source_Dirs use ("units", "test/drivers");
12999 The syntax of a @dfn{simple attribute declaration} is similar to that of an
13000 attribute definition clause in Ada.
13002 Attributes references may be appear in expressions.
13003 The general form for such a reference is @code{<entity>'<attribute>}:
13004 Associative array attributes are functions. Associative
13005 array attribute references must have an argument that is a string literal.
13009 @smallexample @c projectfile
13011 Naming'Dot_Replacement
13012 Imported_Project'Source_Dirs
13013 Imported_Project.Naming'Casing
13014 Builder'^Default_Switches^Default_Switches^("Ada")
13018 The prefix of an attribute may be:
13020 @item @code{project} for an attribute of the current project
13021 @item The name of an existing package of the current project
13022 @item The name of an imported project
13023 @item The name of a parent project that is extended by the current project
13024 @item An expanded name whose prefix is imported/parent project name,
13025 and whose selector is a package name
13030 @smallexample @c projectfile
13033 for Source_Dirs use project'Source_Dirs & "units";
13034 for Source_Dirs use project'Source_Dirs & "test/drivers"
13040 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13041 has the default value: an empty string list. After this declaration,
13042 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13043 After the second attribute declaration @code{Source_Dirs} is a string list of
13044 two elements: @code{"units"} and @code{"test/drivers"}.
13046 Note: this example is for illustration only. In practice,
13047 the project file would contain only one attribute declaration:
13049 @smallexample @c projectfile
13050 for Source_Dirs use ("units", "test/drivers");
13053 @node Associative Array Attributes
13054 @subsection Associative Array Attributes
13057 Some attributes are defined as @emph{associative arrays}. An associative
13058 array may be regarded as a function that takes a string as a parameter
13059 and delivers a string or string list value as its result.
13061 Here are some examples of single associative array attribute associations:
13063 @smallexample @c projectfile
13064 for Body ("main") use "Main.ada";
13065 for ^Switches^Switches^ ("main.ada")
13067 "^-gnatv^-gnatv^");
13068 for ^Switches^Switches^ ("main.ada")
13069 use Builder'^Switches^Switches^ ("main.ada")
13074 Like untyped variables and simple attributes, associative array attributes
13075 may be declared several times. Each declaration supplies a new value for the
13076 attribute, and replaces the previous setting.
13079 An associative array attribute may be declared as a full associative array
13080 declaration, with the value of the same attribute in an imported or extended
13083 @smallexample @c projectfile
13085 for Default_Switches use Default.Builder'Default_Switches;
13090 In this example, @code{Default} must be either a project imported by the
13091 current project, or the project that the current project extends. If the
13092 attribute is in a package (in this case, in package @code{Builder}), the same
13093 package needs to be specified.
13096 A full associative array declaration replaces any other declaration for the
13097 attribute, including other full associative array declaration. Single
13098 associative array associations may be declare after a full associative
13099 declaration, modifying the value for a single association of the attribute.
13101 @node case Constructions
13102 @subsection @code{case} Constructions
13105 A @code{case} construction is used in a project file to effect conditional
13107 Here is a typical example:
13109 @smallexample @c projectfile
13112 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13114 OS : OS_Type := external ("OS", "GNU/Linux");
13118 package Compiler is
13120 when "GNU/Linux" | "Unix" =>
13121 for ^Default_Switches^Default_Switches^ ("Ada")
13122 use ("^-gnath^-gnath^");
13124 for ^Default_Switches^Default_Switches^ ("Ada")
13125 use ("^-gnatP^-gnatP^");
13134 The syntax of a @code{case} construction is based on the Ada case statement
13135 (although there is no @code{null} construction for empty alternatives).
13137 The case expression must be a typed string variable.
13138 Each alternative comprises the reserved word @code{when}, either a list of
13139 literal strings separated by the @code{"|"} character or the reserved word
13140 @code{others}, and the @code{"=>"} token.
13141 Each literal string must belong to the string type that is the type of the
13143 An @code{others} alternative, if present, must occur last.
13145 After each @code{=>}, there are zero or more constructions. The only
13146 constructions allowed in a case construction are other case constructions,
13147 attribute declarations and variable declarations. String type declarations and
13148 package declarations are not allowed. Variable declarations are restricted to
13149 variables that have already been declared before the case construction.
13151 The value of the case variable is often given by an external reference
13152 (@pxref{External References in Project Files}).
13154 @c ****************************************
13155 @c * Objects and Sources in Project Files *
13156 @c ****************************************
13158 @node Objects and Sources in Project Files
13159 @section Objects and Sources in Project Files
13162 * Object Directory::
13164 * Source Directories::
13165 * Source File Names::
13169 Each project has exactly one object directory and one or more source
13170 directories. The source directories must contain at least one source file,
13171 unless the project file explicitly specifies that no source files are present
13172 (@pxref{Source File Names}).
13174 @node Object Directory
13175 @subsection Object Directory
13178 The object directory for a project is the directory containing the compiler's
13179 output (such as @file{ALI} files and object files) for the project's immediate
13182 The object directory is given by the value of the attribute @code{Object_Dir}
13183 in the project file.
13185 @smallexample @c projectfile
13186 for Object_Dir use "objects";
13190 The attribute @code{Object_Dir} has a string value, the path name of the object
13191 directory. The path name may be absolute or relative to the directory of the
13192 project file. This directory must already exist, and be readable and writable.
13194 By default, when the attribute @code{Object_Dir} is not given an explicit value
13195 or when its value is the empty string, the object directory is the same as the
13196 directory containing the project file.
13198 @node Exec Directory
13199 @subsection Exec Directory
13202 The exec directory for a project is the directory containing the executables
13203 for the project's main subprograms.
13205 The exec directory is given by the value of the attribute @code{Exec_Dir}
13206 in the project file.
13208 @smallexample @c projectfile
13209 for Exec_Dir use "executables";
13213 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13214 directory. The path name may be absolute or relative to the directory of the
13215 project file. This directory must already exist, and be writable.
13217 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13218 or when its value is the empty string, the exec directory is the same as the
13219 object directory of the project file.
13221 @node Source Directories
13222 @subsection Source Directories
13225 The source directories of a project are specified by the project file
13226 attribute @code{Source_Dirs}.
13228 This attribute's value is a string list. If the attribute is not given an
13229 explicit value, then there is only one source directory, the one where the
13230 project file resides.
13232 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13235 @smallexample @c projectfile
13236 for Source_Dirs use ();
13240 indicates that the project contains no source files.
13242 Otherwise, each string in the string list designates one or more
13243 source directories.
13245 @smallexample @c projectfile
13246 for Source_Dirs use ("sources", "test/drivers");
13250 If a string in the list ends with @code{"/**"}, then the directory whose path
13251 name precedes the two asterisks, as well as all its subdirectories
13252 (recursively), are source directories.
13254 @smallexample @c projectfile
13255 for Source_Dirs use ("/system/sources/**");
13259 Here the directory @code{/system/sources} and all of its subdirectories
13260 (recursively) are source directories.
13262 To specify that the source directories are the directory of the project file
13263 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13264 @smallexample @c projectfile
13265 for Source_Dirs use ("./**");
13269 Each of the source directories must exist and be readable.
13271 @node Source File Names
13272 @subsection Source File Names
13275 In a project that contains source files, their names may be specified by the
13276 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13277 (a string). Source file names never include any directory information.
13279 If the attribute @code{Source_Files} is given an explicit value, then each
13280 element of the list is a source file name.
13282 @smallexample @c projectfile
13283 for Source_Files use ("main.adb");
13284 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13288 If the attribute @code{Source_Files} is not given an explicit value,
13289 but the attribute @code{Source_List_File} is given a string value,
13290 then the source file names are contained in the text file whose path name
13291 (absolute or relative to the directory of the project file) is the
13292 value of the attribute @code{Source_List_File}.
13294 Each line in the file that is not empty or is not a comment
13295 contains a source file name.
13297 @smallexample @c projectfile
13298 for Source_List_File use "source_list.txt";
13302 By default, if neither the attribute @code{Source_Files} nor the attribute
13303 @code{Source_List_File} is given an explicit value, then each file in the
13304 source directories that conforms to the project's naming scheme
13305 (@pxref{Naming Schemes}) is an immediate source of the project.
13307 A warning is issued if both attributes @code{Source_Files} and
13308 @code{Source_List_File} are given explicit values. In this case, the attribute
13309 @code{Source_Files} prevails.
13311 Each source file name must be the name of one existing source file
13312 in one of the source directories.
13314 A @code{Source_Files} attribute whose value is an empty list
13315 indicates that there are no source files in the project.
13317 If the order of the source directories is known statically, that is if
13318 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13319 be several files with the same source file name. In this case, only the file
13320 in the first directory is considered as an immediate source of the project
13321 file. If the order of the source directories is not known statically, it is
13322 an error to have several files with the same source file name.
13324 Projects can be specified to have no Ada source
13325 files: the value of @code{Source_Dirs} or @code{Source_Files} may be an empty
13326 list, or the @code{"Ada"} may be absent from @code{Languages}:
13328 @smallexample @c projectfile
13329 for Source_Dirs use ();
13330 for Source_Files use ();
13331 for Languages use ("C", "C++");
13335 Otherwise, a project must contain at least one immediate source.
13337 Projects with no source files are useful as template packages
13338 (@pxref{Packages in Project Files}) for other projects; in particular to
13339 define a package @code{Naming} (@pxref{Naming Schemes}).
13341 @c ****************************
13342 @c * Importing Projects *
13343 @c ****************************
13345 @node Importing Projects
13346 @section Importing Projects
13347 @cindex @code{ADA_PROJECT_PATH}
13350 An immediate source of a project P may depend on source files that
13351 are neither immediate sources of P nor in the predefined library.
13352 To get this effect, P must @emph{import} the projects that contain the needed
13355 @smallexample @c projectfile
13357 with "project1", "utilities.gpr";
13358 with "/namings/apex.gpr";
13365 As can be seen in this example, the syntax for importing projects is similar
13366 to the syntax for importing compilation units in Ada. However, project files
13367 use literal strings instead of names, and the @code{with} clause identifies
13368 project files rather than packages.
13370 Each literal string is the file name or path name (absolute or relative) of a
13371 project file. If a string corresponds to a file name, with no path or a
13372 relative path, then its location is determined by the @emph{project path}. The
13373 latter can be queried using @code{gnatls -v}. It contains:
13377 In first position, the directory containing the current project file.
13379 In last position, the default project directory. This default project directory
13380 is part of the GNAT installation and is the standard place to install project
13381 files giving access to standard support libraries.
13383 @ref{Installing a library}
13387 In between, all the directories referenced in the
13388 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13392 If a relative pathname is used, as in
13394 @smallexample @c projectfile
13399 then the full path for the project is constructed by concatenating this
13400 relative path to those in the project path, in order, until a matching file is
13401 found. Any symbolic link will be fully resolved in the directory of the
13402 importing project file before the imported project file is examined.
13404 If the @code{with}'ed project file name does not have an extension,
13405 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13406 then the file name as specified in the @code{with} clause (no extension) will
13407 be used. In the above example, if a file @code{project1.gpr} is found, then it
13408 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13409 then it will be used; if neither file exists, this is an error.
13411 A warning is issued if the name of the project file does not match the
13412 name of the project; this check is case insensitive.
13414 Any source file that is an immediate source of the imported project can be
13415 used by the immediate sources of the importing project, transitively. Thus
13416 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13417 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13418 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13419 because if and when @code{B} ceases to import @code{C}, some sources in
13420 @code{A} will no longer compile.
13422 A side effect of this capability is that normally cyclic dependencies are not
13423 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13424 is not allowed to import @code{A}. However, there are cases when cyclic
13425 dependencies would be beneficial. For these cases, another form of import
13426 between projects exists, the @code{limited with}: a project @code{A} that
13427 imports a project @code{B} with a straight @code{with} may also be imported,
13428 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13429 to @code{A} include at least one @code{limited with}.
13431 @smallexample @c 0projectfile
13437 limited with "../a/a.gpr";
13445 limited with "../a/a.gpr";
13451 In the above legal example, there are two project cycles:
13454 @item A -> C -> D -> A
13458 In each of these cycle there is one @code{limited with}: import of @code{A}
13459 from @code{B} and import of @code{A} from @code{D}.
13461 The difference between straight @code{with} and @code{limited with} is that
13462 the name of a project imported with a @code{limited with} cannot be used in the
13463 project that imports it. In particular, its packages cannot be renamed and
13464 its variables cannot be referred to.
13466 An exception to the above rules for @code{limited with} is that for the main
13467 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13468 @code{limited with} is equivalent to a straight @code{with}. For example,
13469 in the example above, projects @code{B} and @code{D} could not be main
13470 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13471 each have a @code{limited with} that is the only one in a cycle of importing
13474 @c *********************
13475 @c * Project Extension *
13476 @c *********************
13478 @node Project Extension
13479 @section Project Extension
13482 During development of a large system, it is sometimes necessary to use
13483 modified versions of some of the source files, without changing the original
13484 sources. This can be achieved through the @emph{project extension} facility.
13486 @smallexample @c projectfile
13487 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13491 A project extension declaration introduces an extending project
13492 (the @emph{child}) and a project being extended (the @emph{parent}).
13494 By default, a child project inherits all the sources of its parent.
13495 However, inherited sources can be overridden: a unit in a parent is hidden
13496 by a unit of the same name in the child.
13498 Inherited sources are considered to be sources (but not immediate sources)
13499 of the child project; see @ref{Project File Syntax}.
13501 An inherited source file retains any switches specified in the parent project.
13503 For example if the project @code{Utilities} contains the spec and the
13504 body of an Ada package @code{Util_IO}, then the project
13505 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13506 The original body of @code{Util_IO} will not be considered in program builds.
13507 However, the package spec will still be found in the project
13510 A child project can have only one parent, except when it is qualified as
13511 abstract. But it may import any number of other projects.
13513 A project is not allowed to import directly or indirectly at the same time a
13514 child project and any of its ancestors.
13516 @c *******************************
13517 @c * Project Hierarchy Extension *
13518 @c *******************************
13520 @node Project Hierarchy Extension
13521 @section Project Hierarchy Extension
13524 When extending a large system spanning multiple projects, it is often
13525 inconvenient to extend every project in the hierarchy that is impacted by a
13526 small change introduced. In such cases, it is possible to create a virtual
13527 extension of entire hierarchy using @code{extends all} relationship.
13529 When the project is extended using @code{extends all} inheritance, all projects
13530 that are imported by it, both directly and indirectly, are considered virtually
13531 extended. That is, the Project Manager creates "virtual projects"
13532 that extend every project in the hierarchy; all these virtual projects have
13533 no sources of their own and have as object directory the object directory of
13534 the root of "extending all" project.
13536 It is possible to explicitly extend one or more projects in the hierarchy
13537 in order to modify the sources. These extending projects must be imported by
13538 the "extending all" project, which will replace the corresponding virtual
13539 projects with the explicit ones.
13541 When building such a project hierarchy extension, the Project Manager will
13542 ensure that both modified sources and sources in virtual extending projects
13543 that depend on them, are recompiled.
13545 By means of example, consider the following hierarchy of projects.
13549 project A, containing package P1
13551 project B importing A and containing package P2 which depends on P1
13553 project C importing B and containing package P3 which depends on P2
13557 We want to modify packages P1 and P3.
13559 This project hierarchy will need to be extended as follows:
13563 Create project A1 that extends A, placing modified P1 there:
13565 @smallexample @c 0projectfile
13566 project A1 extends "(@dots{})/A" is
13571 Create project C1 that "extends all" C and imports A1, placing modified
13574 @smallexample @c 0projectfile
13575 with "(@dots{})/A1";
13576 project C1 extends all "(@dots{})/C" is
13581 When you build project C1, your entire modified project space will be
13582 recompiled, including the virtual project B1 that has been impacted by the
13583 "extending all" inheritance of project C.
13585 Note that if a Library Project in the hierarchy is virtually extended,
13586 the virtual project that extends the Library Project is not a Library Project.
13588 @c ****************************************
13589 @c * External References in Project Files *
13590 @c ****************************************
13592 @node External References in Project Files
13593 @section External References in Project Files
13596 A project file may contain references to external variables; such references
13597 are called @emph{external references}.
13599 An external variable is either defined as part of the environment (an
13600 environment variable in Unix, for example) or else specified on the command
13601 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13602 If both, then the command line value is used.
13604 The value of an external reference is obtained by means of the built-in
13605 function @code{external}, which returns a string value.
13606 This function has two forms:
13608 @item @code{external (external_variable_name)}
13609 @item @code{external (external_variable_name, default_value)}
13613 Each parameter must be a string literal. For example:
13615 @smallexample @c projectfile
13617 external ("OS", "GNU/Linux")
13621 In the form with one parameter, the function returns the value of
13622 the external variable given as parameter. If this name is not present in the
13623 environment, the function returns an empty string.
13625 In the form with two string parameters, the second argument is
13626 the value returned when the variable given as the first argument is not
13627 present in the environment. In the example above, if @code{"OS"} is not
13628 the name of ^an environment variable^a logical name^ and is not passed on
13629 the command line, then the returned value is @code{"GNU/Linux"}.
13631 An external reference may be part of a string expression or of a string
13632 list expression, and can therefore appear in a variable declaration or
13633 an attribute declaration.
13635 @smallexample @c projectfile
13637 type Mode_Type is ("Debug", "Release");
13638 Mode : Mode_Type := external ("MODE");
13645 @c *****************************
13646 @c * Packages in Project Files *
13647 @c *****************************
13649 @node Packages in Project Files
13650 @section Packages in Project Files
13653 A @emph{package} defines the settings for project-aware tools within a
13655 For each such tool one can declare a package; the names for these
13656 packages are preset (@pxref{Packages}).
13657 A package may contain variable declarations, attribute declarations, and case
13660 @smallexample @c projectfile
13663 package Builder is -- used by gnatmake
13664 for ^Default_Switches^Default_Switches^ ("Ada")
13673 The syntax of package declarations mimics that of package in Ada.
13675 Most of the packages have an attribute
13676 @code{^Default_Switches^Default_Switches^}.
13677 This attribute is an associative array, and its value is a string list.
13678 The index of the associative array is the name of a programming language (case
13679 insensitive). This attribute indicates the ^switch^switch^
13680 or ^switches^switches^ to be used
13681 with the corresponding tool.
13683 Some packages also have another attribute, @code{^Switches^Switches^},
13684 an associative array whose value is a string list.
13685 The index is the name of a source file.
13686 This attribute indicates the ^switch^switch^
13687 or ^switches^switches^ to be used by the corresponding
13688 tool when dealing with this specific file.
13690 Further information on these ^switch^switch^-related attributes is found in
13691 @ref{^Switches^Switches^ and Project Files}.
13693 A package may be declared as a @emph{renaming} of another package; e.g., from
13694 the project file for an imported project.
13696 @smallexample @c projectfile
13698 with "/global/apex.gpr";
13700 package Naming renames Apex.Naming;
13707 Packages that are renamed in other project files often come from project files
13708 that have no sources: they are just used as templates. Any modification in the
13709 template will be reflected automatically in all the project files that rename
13710 a package from the template.
13712 In addition to the tool-oriented packages, you can also declare a package
13713 named @code{Naming} to establish specialized source file naming conventions
13714 (@pxref{Naming Schemes}).
13716 @c ************************************
13717 @c * Variables from Imported Projects *
13718 @c ************************************
13720 @node Variables from Imported Projects
13721 @section Variables from Imported Projects
13724 An attribute or variable defined in an imported or parent project can
13725 be used in expressions in the importing / extending project.
13726 Such an attribute or variable is denoted by an expanded name whose prefix
13727 is either the name of the project or the expanded name of a package within
13730 @smallexample @c projectfile
13733 project Main extends "base" is
13734 Var1 := Imported.Var;
13735 Var2 := Base.Var & ".new";
13740 for ^Default_Switches^Default_Switches^ ("Ada")
13741 use Imported.Builder'Ada_^Switches^Switches^ &
13742 "^-gnatg^-gnatg^" &
13748 package Compiler is
13749 for ^Default_Switches^Default_Switches^ ("Ada")
13750 use Base.Compiler'Ada_^Switches^Switches^;
13761 The value of @code{Var1} is a copy of the variable @code{Var} defined
13762 in the project file @file{"imported.gpr"}
13764 the value of @code{Var2} is a copy of the value of variable @code{Var}
13765 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13767 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13768 @code{Builder} is a string list that includes in its value a copy of the value
13769 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13770 in project file @file{imported.gpr} plus two new elements:
13771 @option{"^-gnatg^-gnatg^"}
13772 and @option{"^-v^-v^"};
13774 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13775 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13776 defined in the @code{Compiler} package in project file @file{base.gpr},
13777 the project being extended.
13780 @c ******************
13781 @c * Naming Schemes *
13782 @c ******************
13784 @node Naming Schemes
13785 @section Naming Schemes
13788 Sometimes an Ada software system is ported from a foreign compilation
13789 environment to GNAT, and the file names do not use the default GNAT
13790 conventions. Instead of changing all the file names (which for a variety
13791 of reasons might not be possible), you can define the relevant file
13792 naming scheme in the @code{Naming} package in your project file.
13795 Note that the use of pragmas described in
13796 @ref{Alternative File Naming Schemes} by mean of a configuration
13797 pragmas file is not supported when using project files. You must use
13798 the features described in this paragraph. You can however use specify
13799 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13802 For example, the following
13803 package models the Apex file naming rules:
13805 @smallexample @c projectfile
13808 for Casing use "lowercase";
13809 for Dot_Replacement use ".";
13810 for Spec_Suffix ("Ada") use ".1.ada";
13811 for Body_Suffix ("Ada") use ".2.ada";
13818 For example, the following package models the HP Ada file naming rules:
13820 @smallexample @c projectfile
13823 for Casing use "lowercase";
13824 for Dot_Replacement use "__";
13825 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13826 for Body_Suffix ("Ada") use ".^ada^ada^";
13832 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13833 names in lower case)
13837 You can define the following attributes in package @code{Naming}:
13841 @item @code{Casing}
13842 This must be a string with one of the three values @code{"lowercase"},
13843 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13846 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13848 @item @code{Dot_Replacement}
13849 This must be a string whose value satisfies the following conditions:
13852 @item It must not be empty
13853 @item It cannot start or end with an alphanumeric character
13854 @item It cannot be a single underscore
13855 @item It cannot start with an underscore followed by an alphanumeric
13856 @item It cannot contain a dot @code{'.'} except if the entire string
13861 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13863 @item @code{Spec_Suffix}
13864 This is an associative array (indexed by the programming language name, case
13865 insensitive) whose value is a string that must satisfy the following
13869 @item It must not be empty
13870 @item It must include at least one dot
13873 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13874 @code{"^.ads^.ADS^"}.
13876 @item @code{Body_Suffix}
13877 This is an associative array (indexed by the programming language name, case
13878 insensitive) whose value is a string that must satisfy the following
13882 @item It must not be empty
13883 @item It must include at least one dot
13884 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13887 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13888 same string, then a file name that ends with the longest of these two suffixes
13889 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13890 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13892 If the suffix does not start with a '.', a file with a name exactly equal
13893 to the suffix will also be part of the project (for instance if you define
13894 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13895 of the project. This is not interesting in general when using projects to
13896 compile. However, it might become useful when a project is also used to
13897 find the list of source files in an editor, like the GNAT Programming System
13900 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13901 @code{"^.adb^.ADB^"}.
13903 @item @code{Separate_Suffix}
13904 This must be a string whose value satisfies the same conditions as
13905 @code{Body_Suffix}. The same "longest suffix" rules apply.
13908 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13909 value as @code{Body_Suffix ("Ada")}.
13913 You can use the associative array attribute @code{Spec} to define
13914 the source file name for an individual Ada compilation unit's spec. The array
13915 index must be a string literal that identifies the Ada unit (case insensitive).
13916 The value of this attribute must be a string that identifies the file that
13917 contains this unit's spec (case sensitive or insensitive depending on the
13920 @smallexample @c projectfile
13921 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13924 When the source file contains several units, you can indicate at what
13925 position the unit occurs in the file, with the following. The first unit
13926 in the file has index 1
13928 @smallexample @c projectfile
13929 for Body ("top") use "foo.a" at 1;
13930 for Body ("foo") use "foo.a" at 2;
13935 You can use the associative array attribute @code{Body} to
13936 define the source file name for an individual Ada compilation unit's body
13937 (possibly a subunit). The array index must be a string literal that identifies
13938 the Ada unit (case insensitive). The value of this attribute must be a string
13939 that identifies the file that contains this unit's body or subunit (case
13940 sensitive or insensitive depending on the operating system).
13942 @smallexample @c projectfile
13943 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13947 @c ********************
13948 @c * Library Projects *
13949 @c ********************
13951 @node Library Projects
13952 @section Library Projects
13955 @emph{Library projects} are projects whose object code is placed in a library.
13956 (Note that this facility is not yet supported on all platforms).
13958 @code{gnatmake} or @code{gprbuild} will collect all object files into a
13959 single archive, which might either be a shared or a static library. This
13960 library can later on be linked with multiple executables, potentially
13961 reducing their sizes.
13963 If your project file specifies languages other than Ada, but you are still
13964 using @code{gnatmake} to compile and link, the latter will not try to
13965 compile your sources other than Ada (you should use @code{gprbuild} if that
13966 is your intent). However, @code{gnatmake} will automatically link all object
13967 files found in the object directory, whether or not they were compiled from
13968 an Ada source file. This specific behavior only applies when multiple
13969 languages are specified.
13971 To create a library project, you need to define in its project file
13972 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13973 Additionally, you may define other library-related attributes such as
13974 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13975 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13977 The @code{Library_Name} attribute has a string value. There is no restriction
13978 on the name of a library. It is the responsibility of the developer to
13979 choose a name that will be accepted by the platform. It is recommended to
13980 choose names that could be Ada identifiers; such names are almost guaranteed
13981 to be acceptable on all platforms.
13983 The @code{Library_Dir} attribute has a string value that designates the path
13984 (absolute or relative) of the directory where the library will reside.
13985 It must designate an existing directory, and this directory must be writable,
13986 different from the project's object directory and from any source directory
13987 in the project tree.
13989 If both @code{Library_Name} and @code{Library_Dir} are specified and
13990 are legal, then the project file defines a library project. The optional
13991 library-related attributes are checked only for such project files.
13993 The @code{Library_Kind} attribute has a string value that must be one of the
13994 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13995 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13996 attribute is not specified, the library is a static library, that is
13997 an archive of object files that can be potentially linked into a
13998 static executable. Otherwise, the library may be dynamic or
13999 relocatable, that is a library that is loaded only at the start of execution.
14001 If you need to build both a static and a dynamic library, you should use two
14002 different object directories, since in some cases some extra code needs to
14003 be generated for the latter. For such cases, it is recommended to either use
14004 two different project files, or a single one which uses external variables
14005 to indicate what kind of library should be build.
14007 The @code{Library_ALI_Dir} attribute may be specified to indicate the
14008 directory where the ALI files of the library will be copied. When it is
14009 not specified, the ALI files are copied to the directory specified in
14010 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
14011 must be writable and different from the project's object directory and from
14012 any source directory in the project tree.
14014 The @code{Library_Version} attribute has a string value whose interpretation
14015 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14016 used only for dynamic/relocatable libraries as the internal name of the
14017 library (the @code{"soname"}). If the library file name (built from the
14018 @code{Library_Name}) is different from the @code{Library_Version}, then the
14019 library file will be a symbolic link to the actual file whose name will be
14020 @code{Library_Version}.
14024 @smallexample @c projectfile
14030 for Library_Dir use "lib_dir";
14031 for Library_Name use "dummy";
14032 for Library_Kind use "relocatable";
14033 for Library_Version use "libdummy.so." & Version;
14040 Directory @file{lib_dir} will contain the internal library file whose name
14041 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14042 @file{libdummy.so.1}.
14044 When @command{gnatmake} detects that a project file
14045 is a library project file, it will check all immediate sources of the project
14046 and rebuild the library if any of the sources have been recompiled.
14048 Standard project files can import library project files. In such cases,
14049 the libraries will only be rebuilt if some of its sources are recompiled
14050 because they are in the closure of some other source in an importing project.
14051 Sources of the library project files that are not in such a closure will
14052 not be checked, unless the full library is checked, because one of its sources
14053 needs to be recompiled.
14055 For instance, assume the project file @code{A} imports the library project file
14056 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14057 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14058 @file{l2.ads}, @file{l2.adb}.
14060 If @file{l1.adb} has been modified, then the library associated with @code{L}
14061 will be rebuilt when compiling all the immediate sources of @code{A} only
14062 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14065 To be sure that all the sources in the library associated with @code{L} are
14066 up to date, and that all the sources of project @code{A} are also up to date,
14067 the following two commands needs to be used:
14074 When a library is built or rebuilt, an attempt is made first to delete all
14075 files in the library directory.
14076 All @file{ALI} files will also be copied from the object directory to the
14077 library directory. To build executables, @command{gnatmake} will use the
14078 library rather than the individual object files.
14081 It is also possible to create library project files for third-party libraries
14082 that are precompiled and cannot be compiled locally thanks to the
14083 @code{externally_built} attribute. (See @ref{Installing a library}).
14086 @c *******************************
14087 @c * Stand-alone Library Projects *
14088 @c *******************************
14090 @node Stand-alone Library Projects
14091 @section Stand-alone Library Projects
14094 A Stand-alone Library is a library that contains the necessary code to
14095 elaborate the Ada units that are included in the library. A Stand-alone
14096 Library is suitable to be used in an executable when the main is not
14097 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14100 A Stand-alone Library Project is a Library Project where the library is
14101 a Stand-alone Library.
14103 To be a Stand-alone Library Project, in addition to the two attributes
14104 that make a project a Library Project (@code{Library_Name} and
14105 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14106 @code{Library_Interface} must be defined.
14108 @smallexample @c projectfile
14110 for Library_Dir use "lib_dir";
14111 for Library_Name use "dummy";
14112 for Library_Interface use ("int1", "int1.child");
14116 Attribute @code{Library_Interface} has a nonempty string list value,
14117 each string in the list designating a unit contained in an immediate source
14118 of the project file.
14120 When a Stand-alone Library is built, first the binder is invoked to build
14121 a package whose name depends on the library name
14122 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14123 This binder-generated package includes initialization and
14124 finalization procedures whose
14125 names depend on the library name (dummyinit and dummyfinal in the example
14126 above). The object corresponding to this package is included in the library.
14128 A dynamic or relocatable Stand-alone Library is automatically initialized
14129 if automatic initialization of Stand-alone Libraries is supported on the
14130 platform and if attribute @code{Library_Auto_Init} is not specified or
14131 is specified with the value "true". A static Stand-alone Library is never
14132 automatically initialized.
14134 Single string attribute @code{Library_Auto_Init} may be specified with only
14135 two possible values: "false" or "true" (case-insensitive). Specifying
14136 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14137 initialization of dynamic or relocatable libraries.
14139 When a non-automatically initialized Stand-alone Library is used
14140 in an executable, its initialization procedure must be called before
14141 any service of the library is used.
14142 When the main subprogram is in Ada, it may mean that the initialization
14143 procedure has to be called during elaboration of another package.
14145 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14146 (those that are listed in attribute @code{Library_Interface}) are copied to
14147 the Library Directory. As a consequence, only the Interface Units may be
14148 imported from Ada units outside of the library. If other units are imported,
14149 the binding phase will fail.
14151 When a Stand-Alone Library is bound, the switches that are specified in
14152 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14153 used in the call to @command{gnatbind}.
14155 The string list attribute @code{Library_Options} may be used to specified
14156 additional switches to the call to @command{gcc} to link the library.
14158 The attribute @code{Library_Src_Dir}, may be specified for a
14159 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14160 single string value. Its value must be the path (absolute or relative to the
14161 project directory) of an existing directory. This directory cannot be the
14162 object directory or one of the source directories, but it can be the same as
14163 the library directory. The sources of the Interface
14164 Units of the library, necessary to an Ada client of the library, will be
14165 copied to the designated directory, called Interface Copy directory.
14166 These sources includes the specs of the Interface Units, but they may also
14167 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14168 are used, or when there is a generic units in the spec. Before the sources
14169 are copied to the Interface Copy directory, an attempt is made to delete all
14170 files in the Interface Copy directory.
14172 @c *************************************
14173 @c * Switches Related to Project Files *
14174 @c *************************************
14175 @node Switches Related to Project Files
14176 @section Switches Related to Project Files
14179 The following switches are used by GNAT tools that support project files:
14183 @item ^-P^/PROJECT_FILE=^@var{project}
14184 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14185 Indicates the name of a project file. This project file will be parsed with
14186 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14187 if any, and using the external references indicated
14188 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14190 There may zero, one or more spaces between @option{-P} and @var{project}.
14194 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14197 Since the Project Manager parses the project file only after all the switches
14198 on the command line are checked, the order of the switches
14199 @option{^-P^/PROJECT_FILE^},
14200 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14201 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14203 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14204 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14205 Indicates that external variable @var{name} has the value @var{value}.
14206 The Project Manager will use this value for occurrences of
14207 @code{external(name)} when parsing the project file.
14211 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14212 put between quotes.
14220 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14221 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14222 @var{name}, only the last one is used.
14225 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14226 takes precedence over the value of the same name in the environment.
14228 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14229 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14230 Indicates the verbosity of the parsing of GNAT project files.
14233 @option{-vP0} means Default;
14234 @option{-vP1} means Medium;
14235 @option{-vP2} means High.
14239 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14244 The default is ^Default^DEFAULT^: no output for syntactically correct
14247 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14248 only the last one is used.
14250 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14251 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14252 Add directory <dir> at the beginning of the project search path, in order,
14253 after the current working directory.
14257 @cindex @option{-eL} (any project-aware tool)
14258 Follow all symbolic links when processing project files.
14261 @item ^--subdirs^/SUBDIRS^=<subdir>
14262 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14263 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14264 directories (except the source directories) are the subdirectories <subdir>
14265 of the directories specified in the project files. This applies in particular
14266 to object directories, library directories and exec directories. If the
14267 subdirectories do not exist, they are created automatically.
14271 @c **********************************
14272 @c * Tools Supporting Project Files *
14273 @c **********************************
14275 @node Tools Supporting Project Files
14276 @section Tools Supporting Project Files
14279 * gnatmake and Project Files::
14280 * The GNAT Driver and Project Files::
14283 @node gnatmake and Project Files
14284 @subsection gnatmake and Project Files
14287 This section covers several topics related to @command{gnatmake} and
14288 project files: defining ^switches^switches^ for @command{gnatmake}
14289 and for the tools that it invokes; specifying configuration pragmas;
14290 the use of the @code{Main} attribute; building and rebuilding library project
14294 * ^Switches^Switches^ and Project Files::
14295 * Specifying Configuration Pragmas::
14296 * Project Files and Main Subprograms::
14297 * Library Project Files::
14300 @node ^Switches^Switches^ and Project Files
14301 @subsubsection ^Switches^Switches^ and Project Files
14304 It is not currently possible to specify VMS style qualifiers in the project
14305 files; only Unix style ^switches^switches^ may be specified.
14309 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14310 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14311 attribute, a @code{^Switches^Switches^} attribute, or both;
14312 as their names imply, these ^switch^switch^-related
14313 attributes affect the ^switches^switches^ that are used for each of these GNAT
14315 @command{gnatmake} is invoked. As will be explained below, these
14316 component-specific ^switches^switches^ precede
14317 the ^switches^switches^ provided on the @command{gnatmake} command line.
14319 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14320 array indexed by language name (case insensitive) whose value is a string list.
14323 @smallexample @c projectfile
14325 package Compiler is
14326 for ^Default_Switches^Default_Switches^ ("Ada")
14327 use ("^-gnaty^-gnaty^",
14334 The @code{^Switches^Switches^} attribute is also an associative array,
14335 indexed by a file name (which may or may not be case sensitive, depending
14336 on the operating system) whose value is a string list. For example:
14338 @smallexample @c projectfile
14341 for ^Switches^Switches^ ("main1.adb")
14343 for ^Switches^Switches^ ("main2.adb")
14350 For the @code{Builder} package, the file names must designate source files
14351 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14352 file names must designate @file{ALI} or source files for main subprograms.
14353 In each case just the file name without an explicit extension is acceptable.
14355 For each tool used in a program build (@command{gnatmake}, the compiler, the
14356 binder, and the linker), the corresponding package @dfn{contributes} a set of
14357 ^switches^switches^ for each file on which the tool is invoked, based on the
14358 ^switch^switch^-related attributes defined in the package.
14359 In particular, the ^switches^switches^
14360 that each of these packages contributes for a given file @var{f} comprise:
14364 the value of attribute @code{^Switches^Switches^ (@var{f})},
14365 if it is specified in the package for the given file,
14367 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14368 if it is specified in the package.
14372 If neither of these attributes is defined in the package, then the package does
14373 not contribute any ^switches^switches^ for the given file.
14375 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14376 two sets, in the following order: those contributed for the file
14377 by the @code{Builder} package;
14378 and the switches passed on the command line.
14380 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14381 the ^switches^switches^ passed to the tool comprise three sets,
14382 in the following order:
14386 the applicable ^switches^switches^ contributed for the file
14387 by the @code{Builder} package in the project file supplied on the command line;
14390 those contributed for the file by the package (in the relevant project file --
14391 see below) corresponding to the tool; and
14394 the applicable switches passed on the command line.
14398 The term @emph{applicable ^switches^switches^} reflects the fact that
14399 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14400 tools, depending on the individual ^switch^switch^.
14402 @command{gnatmake} may invoke the compiler on source files from different
14403 projects. The Project Manager will use the appropriate project file to
14404 determine the @code{Compiler} package for each source file being compiled.
14405 Likewise for the @code{Binder} and @code{Linker} packages.
14407 As an example, consider the following package in a project file:
14409 @smallexample @c projectfile
14412 package Compiler is
14413 for ^Default_Switches^Default_Switches^ ("Ada")
14415 for ^Switches^Switches^ ("a.adb")
14417 for ^Switches^Switches^ ("b.adb")
14419 "^-gnaty^-gnaty^");
14426 If @command{gnatmake} is invoked with this project file, and it needs to
14427 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14428 @file{a.adb} will be compiled with the ^switch^switch^
14429 @option{^-O1^-O1^},
14430 @file{b.adb} with ^switches^switches^
14432 and @option{^-gnaty^-gnaty^},
14433 and @file{c.adb} with @option{^-g^-g^}.
14435 The following example illustrates the ordering of the ^switches^switches^
14436 contributed by different packages:
14438 @smallexample @c projectfile
14442 for ^Switches^Switches^ ("main.adb")
14450 package Compiler is
14451 for ^Switches^Switches^ ("main.adb")
14459 If you issue the command:
14462 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14466 then the compiler will be invoked on @file{main.adb} with the following
14467 sequence of ^switches^switches^
14470 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14473 with the last @option{^-O^-O^}
14474 ^switch^switch^ having precedence over the earlier ones;
14475 several other ^switches^switches^
14476 (such as @option{^-c^-c^}) are added implicitly.
14478 The ^switches^switches^
14480 and @option{^-O1^-O1^} are contributed by package
14481 @code{Builder}, @option{^-O2^-O2^} is contributed
14482 by the package @code{Compiler}
14483 and @option{^-O0^-O0^} comes from the command line.
14485 The @option{^-g^-g^}
14486 ^switch^switch^ will also be passed in the invocation of
14487 @command{Gnatlink.}
14489 A final example illustrates switch contributions from packages in different
14492 @smallexample @c projectfile
14495 for Source_Files use ("pack.ads", "pack.adb");
14496 package Compiler is
14497 for ^Default_Switches^Default_Switches^ ("Ada")
14498 use ("^-gnata^-gnata^");
14506 for Source_Files use ("foo_main.adb", "bar_main.adb");
14508 for ^Switches^Switches^ ("foo_main.adb")
14516 -- Ada source file:
14518 procedure Foo_Main is
14526 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14530 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14531 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14532 @option{^-gnato^-gnato^} (passed on the command line).
14533 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14534 are @option{^-g^-g^} from @code{Proj4.Builder},
14535 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14536 and @option{^-gnato^-gnato^} from the command line.
14539 When using @command{gnatmake} with project files, some ^switches^switches^ or
14540 arguments may be expressed as relative paths. As the working directory where
14541 compilation occurs may change, these relative paths are converted to absolute
14542 paths. For the ^switches^switches^ found in a project file, the relative paths
14543 are relative to the project file directory, for the switches on the command
14544 line, they are relative to the directory where @command{gnatmake} is invoked.
14545 The ^switches^switches^ for which this occurs are:
14551 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14553 ^-o^-o^, object files specified in package @code{Linker} or after
14554 -largs on the command line). The exception to this rule is the ^switch^switch^
14555 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14557 @node Specifying Configuration Pragmas
14558 @subsubsection Specifying Configuration Pragmas
14560 When using @command{gnatmake} with project files, if there exists a file
14561 @file{gnat.adc} that contains configuration pragmas, this file will be
14564 Configuration pragmas can be defined by means of the following attributes in
14565 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14566 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14568 Both these attributes are single string attributes. Their values is the path
14569 name of a file containing configuration pragmas. If a path name is relative,
14570 then it is relative to the project directory of the project file where the
14571 attribute is defined.
14573 When compiling a source, the configuration pragmas used are, in order,
14574 those listed in the file designated by attribute
14575 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14576 project file, if it is specified, and those listed in the file designated by
14577 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14578 the project file of the source, if it exists.
14580 @node Project Files and Main Subprograms
14581 @subsubsection Project Files and Main Subprograms
14584 When using a project file, you can invoke @command{gnatmake}
14585 with one or several main subprograms, by specifying their source files on the
14589 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14593 Each of these needs to be a source file of the same project, except
14594 when the switch ^-u^/UNIQUE^ is used.
14597 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14598 same project, one of the project in the tree rooted at the project specified
14599 on the command line. The package @code{Builder} of this common project, the
14600 "main project" is the one that is considered by @command{gnatmake}.
14603 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14604 imported directly or indirectly by the project specified on the command line.
14605 Note that if such a source file is not part of the project specified on the
14606 command line, the ^switches^switches^ found in package @code{Builder} of the
14607 project specified on the command line, if any, that are transmitted
14608 to the compiler will still be used, not those found in the project file of
14612 When using a project file, you can also invoke @command{gnatmake} without
14613 explicitly specifying any main, and the effect depends on whether you have
14614 defined the @code{Main} attribute. This attribute has a string list value,
14615 where each element in the list is the name of a source file (the file
14616 extension is optional) that contains a unit that can be a main subprogram.
14618 If the @code{Main} attribute is defined in a project file as a non-empty
14619 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14620 line, then invoking @command{gnatmake} with this project file but without any
14621 main on the command line is equivalent to invoking @command{gnatmake} with all
14622 the file names in the @code{Main} attribute on the command line.
14625 @smallexample @c projectfile
14628 for Main use ("main1", "main2", "main3");
14634 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14636 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14638 When the project attribute @code{Main} is not specified, or is specified
14639 as an empty string list, or when the switch @option{-u} is used on the command
14640 line, then invoking @command{gnatmake} with no main on the command line will
14641 result in all immediate sources of the project file being checked, and
14642 potentially recompiled. Depending on the presence of the switch @option{-u},
14643 sources from other project files on which the immediate sources of the main
14644 project file depend are also checked and potentially recompiled. In other
14645 words, the @option{-u} switch is applied to all of the immediate sources of the
14648 When no main is specified on the command line and attribute @code{Main} exists
14649 and includes several mains, or when several mains are specified on the
14650 command line, the default ^switches^switches^ in package @code{Builder} will
14651 be used for all mains, even if there are specific ^switches^switches^
14652 specified for one or several mains.
14654 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14655 the specific ^switches^switches^ for each main, if they are specified.
14657 @node Library Project Files
14658 @subsubsection Library Project Files
14661 When @command{gnatmake} is invoked with a main project file that is a library
14662 project file, it is not allowed to specify one or more mains on the command
14666 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14667 ^-l^/ACTION=LINK^ have special meanings.
14670 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14671 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14674 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14675 to @command{gnatmake} that the binder generated file should be compiled
14676 (in the case of a stand-alone library) and that the library should be built.
14680 @node The GNAT Driver and Project Files
14681 @subsection The GNAT Driver and Project Files
14684 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14685 can benefit from project files:
14686 @command{^gnatbind^gnatbind^},
14687 @command{^gnatcheck^gnatcheck^}),
14688 @command{^gnatclean^gnatclean^}),
14689 @command{^gnatelim^gnatelim^},
14690 @command{^gnatfind^gnatfind^},
14691 @command{^gnatlink^gnatlink^},
14692 @command{^gnatls^gnatls^},
14693 @command{^gnatmetric^gnatmetric^},
14694 @command{^gnatpp^gnatpp^},
14695 @command{^gnatstub^gnatstub^},
14696 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14697 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14698 They must be invoked through the @command{gnat} driver.
14700 The @command{gnat} driver is a wrapper that accepts a number of commands and
14701 calls the corresponding tool. It was designed initially for VMS platforms (to
14702 convert VMS qualifiers to Unix-style switches), but it is now available on all
14705 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14706 (case insensitive):
14710 BIND to invoke @command{^gnatbind^gnatbind^}
14712 CHOP to invoke @command{^gnatchop^gnatchop^}
14714 CLEAN to invoke @command{^gnatclean^gnatclean^}
14716 COMP or COMPILE to invoke the compiler
14718 ELIM to invoke @command{^gnatelim^gnatelim^}
14720 FIND to invoke @command{^gnatfind^gnatfind^}
14722 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14724 LINK to invoke @command{^gnatlink^gnatlink^}
14726 LS or LIST to invoke @command{^gnatls^gnatls^}
14728 MAKE to invoke @command{^gnatmake^gnatmake^}
14730 NAME to invoke @command{^gnatname^gnatname^}
14732 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14734 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14736 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14738 STUB to invoke @command{^gnatstub^gnatstub^}
14740 XREF to invoke @command{^gnatxref^gnatxref^}
14744 (note that the compiler is invoked using the command
14745 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14748 On non-VMS platforms, between @command{gnat} and the command, two
14749 special switches may be used:
14753 @command{-v} to display the invocation of the tool.
14755 @command{-dn} to prevent the @command{gnat} driver from removing
14756 the temporary files it has created. These temporary files are
14757 configuration files and temporary file list files.
14761 The command may be followed by switches and arguments for the invoked
14765 gnat bind -C main.ali
14771 Switches may also be put in text files, one switch per line, and the text
14772 files may be specified with their path name preceded by '@@'.
14775 gnat bind @@args.txt main.ali
14779 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14780 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14781 (@option{^-P^/PROJECT_FILE^},
14782 @option{^-X^/EXTERNAL_REFERENCE^} and
14783 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14784 the switches of the invoking tool.
14787 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14788 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14789 the immediate sources of the specified project file.
14792 When GNAT METRIC is used with a project file, but with no source
14793 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14794 with all the immediate sources of the specified project file and with
14795 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14799 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14800 a project file, no source is specified on the command line and
14801 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14802 the underlying tool (^gnatpp^gnatpp^ or
14803 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14804 not only for the immediate sources of the main project.
14806 (-U stands for Universal or Union of the project files of the project tree)
14810 For each of the following commands, there is optionally a corresponding
14811 package in the main project.
14815 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14818 package @code{Check} for command CHECK (invoking
14819 @code{^gnatcheck^gnatcheck^})
14822 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14825 package @code{Cross_Reference} for command XREF (invoking
14826 @code{^gnatxref^gnatxref^})
14829 package @code{Eliminate} for command ELIM (invoking
14830 @code{^gnatelim^gnatelim^})
14833 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14836 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14839 package @code{Gnatstub} for command STUB
14840 (invoking @code{^gnatstub^gnatstub^})
14843 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14846 package @code{Metrics} for command METRIC
14847 (invoking @code{^gnatmetric^gnatmetric^})
14850 package @code{Pretty_Printer} for command PP or PRETTY
14851 (invoking @code{^gnatpp^gnatpp^})
14856 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14857 a simple variable with a string list value. It contains ^switches^switches^
14858 for the invocation of @code{^gnatls^gnatls^}.
14860 @smallexample @c projectfile
14864 for ^Switches^Switches^
14873 All other packages have two attribute @code{^Switches^Switches^} and
14874 @code{^Default_Switches^Default_Switches^}.
14877 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14878 source file name, that has a string list value: the ^switches^switches^ to be
14879 used when the tool corresponding to the package is invoked for the specific
14883 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14884 indexed by the programming language that has a string list value.
14885 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14886 ^switches^switches^ for the invocation of the tool corresponding
14887 to the package, except if a specific @code{^Switches^Switches^} attribute
14888 is specified for the source file.
14890 @smallexample @c projectfile
14894 for Source_Dirs use ("./**");
14897 for ^Switches^Switches^ use
14904 package Compiler is
14905 for ^Default_Switches^Default_Switches^ ("Ada")
14906 use ("^-gnatv^-gnatv^",
14907 "^-gnatwa^-gnatwa^");
14913 for ^Default_Switches^Default_Switches^ ("Ada")
14921 for ^Default_Switches^Default_Switches^ ("Ada")
14923 for ^Switches^Switches^ ("main.adb")
14932 for ^Default_Switches^Default_Switches^ ("Ada")
14939 package Cross_Reference is
14940 for ^Default_Switches^Default_Switches^ ("Ada")
14945 end Cross_Reference;
14951 With the above project file, commands such as
14954 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14955 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14956 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14957 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14958 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14962 will set up the environment properly and invoke the tool with the switches
14963 found in the package corresponding to the tool:
14964 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14965 except @code{^Switches^Switches^ ("main.adb")}
14966 for @code{^gnatlink^gnatlink^}.
14967 It is also possible to invoke some of the tools,
14968 @code{^gnatcheck^gnatcheck^}),
14969 @code{^gnatmetric^gnatmetric^}),
14970 and @code{^gnatpp^gnatpp^})
14971 on a set of project units thanks to the combination of the switches
14972 @option{-P}, @option{-U} and possibly the main unit when one is interested
14973 in its closure. For instance,
14977 will compute the metrics for all the immediate units of project
14980 gnat metric -Pproj -U
14982 will compute the metrics for all the units of the closure of projects
14983 rooted at @code{proj}.
14985 gnat metric -Pproj -U main_unit
14987 will compute the metrics for the closure of units rooted at
14988 @code{main_unit}. This last possibility relies implicitly
14989 on @command{gnatbind}'s option @option{-R}.
14991 @c **********************
14992 @node An Extended Example
14993 @section An Extended Example
14996 Suppose that we have two programs, @var{prog1} and @var{prog2},
14997 whose sources are in corresponding directories. We would like
14998 to build them with a single @command{gnatmake} command, and we want to place
14999 their object files into @file{build} subdirectories of the source directories.
15000 Furthermore, we want to have to have two separate subdirectories
15001 in @file{build} -- @file{release} and @file{debug} -- which will contain
15002 the object files compiled with different set of compilation flags.
15004 In other words, we have the following structure:
15021 Here are the project files that we must place in a directory @file{main}
15022 to maintain this structure:
15026 @item We create a @code{Common} project with a package @code{Compiler} that
15027 specifies the compilation ^switches^switches^:
15032 @b{project} Common @b{is}
15034 @b{for} Source_Dirs @b{use} (); -- No source files
15038 @b{type} Build_Type @b{is} ("release", "debug");
15039 Build : Build_Type := External ("BUILD", "debug");
15042 @b{package} Compiler @b{is}
15043 @b{case} Build @b{is}
15044 @b{when} "release" =>
15045 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15046 @b{use} ("^-O2^-O2^");
15047 @b{when} "debug" =>
15048 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15049 @b{use} ("^-g^-g^");
15057 @item We create separate projects for the two programs:
15064 @b{project} Prog1 @b{is}
15066 @b{for} Source_Dirs @b{use} ("prog1");
15067 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15069 @b{package} Compiler @b{renames} Common.Compiler;
15080 @b{project} Prog2 @b{is}
15082 @b{for} Source_Dirs @b{use} ("prog2");
15083 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15085 @b{package} Compiler @b{renames} Common.Compiler;
15091 @item We create a wrapping project @code{Main}:
15100 @b{project} Main @b{is}
15102 @b{package} Compiler @b{renames} Common.Compiler;
15108 @item Finally we need to create a dummy procedure that @code{with}s (either
15109 explicitly or implicitly) all the sources of our two programs.
15114 Now we can build the programs using the command
15117 gnatmake ^-P^/PROJECT_FILE=^main dummy
15121 for the Debug mode, or
15125 gnatmake -Pmain -XBUILD=release
15131 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15136 for the Release mode.
15138 @c ********************************
15139 @c * Project File Complete Syntax *
15140 @c ********************************
15142 @node Project File Complete Syntax
15143 @section Project File Complete Syntax
15147 context_clause project_declaration
15153 @b{with} path_name @{ , path_name @} ;
15158 project_declaration ::=
15159 simple_project_declaration | project_extension
15161 simple_project_declaration ::=
15162 @b{project} <project_>simple_name @b{is}
15163 @{declarative_item@}
15164 @b{end} <project_>simple_name;
15166 project_extension ::=
15167 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15168 @{declarative_item@}
15169 @b{end} <project_>simple_name;
15171 declarative_item ::=
15172 package_declaration |
15173 typed_string_declaration |
15174 other_declarative_item
15176 package_declaration ::=
15177 package_spec | package_renaming
15180 @b{package} package_identifier @b{is}
15181 @{simple_declarative_item@}
15182 @b{end} package_identifier ;
15184 package_identifier ::=
15185 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15186 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15187 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15189 package_renaming ::==
15190 @b{package} package_identifier @b{renames}
15191 <project_>simple_name.package_identifier ;
15193 typed_string_declaration ::=
15194 @b{type} <typed_string_>_simple_name @b{is}
15195 ( string_literal @{, string_literal@} );
15197 other_declarative_item ::=
15198 attribute_declaration |
15199 typed_variable_declaration |
15200 variable_declaration |
15203 attribute_declaration ::=
15204 full_associative_array_declaration |
15205 @b{for} attribute_designator @b{use} expression ;
15207 full_associative_array_declaration ::=
15208 @b{for} <associative_array_attribute_>simple_name @b{use}
15209 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15211 attribute_designator ::=
15212 <simple_attribute_>simple_name |
15213 <associative_array_attribute_>simple_name ( string_literal )
15215 typed_variable_declaration ::=
15216 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15218 variable_declaration ::=
15219 <variable_>simple_name := expression;
15229 attribute_reference
15235 ( <string_>expression @{ , <string_>expression @} )
15238 @b{external} ( string_literal [, string_literal] )
15240 attribute_reference ::=
15241 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15243 attribute_prefix ::=
15245 <project_>simple_name | package_identifier |
15246 <project_>simple_name . package_identifier
15248 case_construction ::=
15249 @b{case} <typed_variable_>name @b{is}
15254 @b{when} discrete_choice_list =>
15255 @{case_construction | attribute_declaration@}
15257 discrete_choice_list ::=
15258 string_literal @{| string_literal@} |
15262 simple_name @{. simple_name@}
15265 identifier (same as Ada)
15269 @node The Cross-Referencing Tools gnatxref and gnatfind
15270 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15275 The compiler generates cross-referencing information (unless
15276 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15277 This information indicates where in the source each entity is declared and
15278 referenced. Note that entities in package Standard are not included, but
15279 entities in all other predefined units are included in the output.
15281 Before using any of these two tools, you need to compile successfully your
15282 application, so that GNAT gets a chance to generate the cross-referencing
15285 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15286 information to provide the user with the capability to easily locate the
15287 declaration and references to an entity. These tools are quite similar,
15288 the difference being that @code{gnatfind} is intended for locating
15289 definitions and/or references to a specified entity or entities, whereas
15290 @code{gnatxref} is oriented to generating a full report of all
15293 To use these tools, you must not compile your application using the
15294 @option{-gnatx} switch on the @command{gnatmake} command line
15295 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15296 information will not be generated.
15298 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15299 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15302 * gnatxref Switches::
15303 * gnatfind Switches::
15304 * Project Files for gnatxref and gnatfind::
15305 * Regular Expressions in gnatfind and gnatxref::
15306 * Examples of gnatxref Usage::
15307 * Examples of gnatfind Usage::
15310 @node gnatxref Switches
15311 @section @code{gnatxref} Switches
15314 The command invocation for @code{gnatxref} is:
15316 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15325 identifies the source files for which a report is to be generated. The
15326 ``with''ed units will be processed too. You must provide at least one file.
15328 These file names are considered to be regular expressions, so for instance
15329 specifying @file{source*.adb} is the same as giving every file in the current
15330 directory whose name starts with @file{source} and whose extension is
15333 You shouldn't specify any directory name, just base names. @command{gnatxref}
15334 and @command{gnatfind} will be able to locate these files by themselves using
15335 the source path. If you specify directories, no result is produced.
15340 The switches can be:
15344 @cindex @option{--version} @command{gnatxref}
15345 Display Copyright and version, then exit disregarding all other options.
15348 @cindex @option{--help} @command{gnatxref}
15349 If @option{--version} was not used, display usage, then exit disregarding
15352 @item ^-a^/ALL_FILES^
15353 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15354 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15355 the read-only files found in the library search path. Otherwise, these files
15356 will be ignored. This option can be used to protect Gnat sources or your own
15357 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15358 much faster, and their output much smaller. Read-only here refers to access
15359 or permissions status in the file system for the current user.
15362 @cindex @option{-aIDIR} (@command{gnatxref})
15363 When looking for source files also look in directory DIR. The order in which
15364 source file search is undertaken is the same as for @command{gnatmake}.
15367 @cindex @option{-aODIR} (@command{gnatxref})
15368 When searching for library and object files, look in directory
15369 DIR. The order in which library files are searched is the same as for
15370 @command{gnatmake}.
15373 @cindex @option{-nostdinc} (@command{gnatxref})
15374 Do not look for sources in the system default directory.
15377 @cindex @option{-nostdlib} (@command{gnatxref})
15378 Do not look for library files in the system default directory.
15380 @item --RTS=@var{rts-path}
15381 @cindex @option{--RTS} (@command{gnatxref})
15382 Specifies the default location of the runtime library. Same meaning as the
15383 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15385 @item ^-d^/DERIVED_TYPES^
15386 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15387 If this switch is set @code{gnatxref} will output the parent type
15388 reference for each matching derived types.
15390 @item ^-f^/FULL_PATHNAME^
15391 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15392 If this switch is set, the output file names will be preceded by their
15393 directory (if the file was found in the search path). If this switch is
15394 not set, the directory will not be printed.
15396 @item ^-g^/IGNORE_LOCALS^
15397 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15398 If this switch is set, information is output only for library-level
15399 entities, ignoring local entities. The use of this switch may accelerate
15400 @code{gnatfind} and @code{gnatxref}.
15403 @cindex @option{-IDIR} (@command{gnatxref})
15404 Equivalent to @samp{-aODIR -aIDIR}.
15407 @cindex @option{-pFILE} (@command{gnatxref})
15408 Specify a project file to use @xref{Project Files}.
15409 If you need to use the @file{.gpr}
15410 project files, you should use gnatxref through the GNAT driver
15411 (@command{gnat xref -Pproject}).
15413 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15414 project file in the current directory.
15416 If a project file is either specified or found by the tools, then the content
15417 of the source directory and object directory lines are added as if they
15418 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15419 and @samp{^-aO^OBJECT_SEARCH^}.
15421 Output only unused symbols. This may be really useful if you give your
15422 main compilation unit on the command line, as @code{gnatxref} will then
15423 display every unused entity and 'with'ed package.
15427 Instead of producing the default output, @code{gnatxref} will generate a
15428 @file{tags} file that can be used by vi. For examples how to use this
15429 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15430 to the standard output, thus you will have to redirect it to a file.
15436 All these switches may be in any order on the command line, and may even
15437 appear after the file names. They need not be separated by spaces, thus
15438 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15439 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15441 @node gnatfind Switches
15442 @section @code{gnatfind} Switches
15445 The command line for @code{gnatfind} is:
15448 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15449 @r{[}@var{file1} @var{file2} @dots{}]
15457 An entity will be output only if it matches the regular expression found
15458 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15460 Omitting the pattern is equivalent to specifying @samp{*}, which
15461 will match any entity. Note that if you do not provide a pattern, you
15462 have to provide both a sourcefile and a line.
15464 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15465 for matching purposes. At the current time there is no support for
15466 8-bit codes other than Latin-1, or for wide characters in identifiers.
15469 @code{gnatfind} will look for references, bodies or declarations
15470 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15471 and column @var{column}. See @ref{Examples of gnatfind Usage}
15472 for syntax examples.
15475 is a decimal integer identifying the line number containing
15476 the reference to the entity (or entities) to be located.
15479 is a decimal integer identifying the exact location on the
15480 line of the first character of the identifier for the
15481 entity reference. Columns are numbered from 1.
15483 @item file1 file2 @dots{}
15484 The search will be restricted to these source files. If none are given, then
15485 the search will be done for every library file in the search path.
15486 These file must appear only after the pattern or sourcefile.
15488 These file names are considered to be regular expressions, so for instance
15489 specifying @file{source*.adb} is the same as giving every file in the current
15490 directory whose name starts with @file{source} and whose extension is
15493 The location of the spec of the entity will always be displayed, even if it
15494 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15495 occurrences of the entity in the separate units of the ones given on the
15496 command line will also be displayed.
15498 Note that if you specify at least one file in this part, @code{gnatfind} may
15499 sometimes not be able to find the body of the subprograms.
15504 At least one of 'sourcefile' or 'pattern' has to be present on
15507 The following switches are available:
15511 @cindex @option{--version} @command{gnatfind}
15512 Display Copyright and version, then exit disregarding all other options.
15515 @cindex @option{--help} @command{gnatfind}
15516 If @option{--version} was not used, display usage, then exit disregarding
15519 @item ^-a^/ALL_FILES^
15520 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15521 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15522 the read-only files found in the library search path. Otherwise, these files
15523 will be ignored. This option can be used to protect Gnat sources or your own
15524 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15525 much faster, and their output much smaller. Read-only here refers to access
15526 or permission status in the file system for the current user.
15529 @cindex @option{-aIDIR} (@command{gnatfind})
15530 When looking for source files also look in directory DIR. The order in which
15531 source file search is undertaken is the same as for @command{gnatmake}.
15534 @cindex @option{-aODIR} (@command{gnatfind})
15535 When searching for library and object files, look in directory
15536 DIR. The order in which library files are searched is the same as for
15537 @command{gnatmake}.
15540 @cindex @option{-nostdinc} (@command{gnatfind})
15541 Do not look for sources in the system default directory.
15544 @cindex @option{-nostdlib} (@command{gnatfind})
15545 Do not look for library files in the system default directory.
15547 @item --RTS=@var{rts-path}
15548 @cindex @option{--RTS} (@command{gnatfind})
15549 Specifies the default location of the runtime library. Same meaning as the
15550 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15552 @item ^-d^/DERIVED_TYPE_INFORMATION^
15553 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15554 If this switch is set, then @code{gnatfind} will output the parent type
15555 reference for each matching derived types.
15557 @item ^-e^/EXPRESSIONS^
15558 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15559 By default, @code{gnatfind} accept the simple regular expression set for
15560 @samp{pattern}. If this switch is set, then the pattern will be
15561 considered as full Unix-style regular expression.
15563 @item ^-f^/FULL_PATHNAME^
15564 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15565 If this switch is set, the output file names will be preceded by their
15566 directory (if the file was found in the search path). If this switch is
15567 not set, the directory will not be printed.
15569 @item ^-g^/IGNORE_LOCALS^
15570 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15571 If this switch is set, information is output only for library-level
15572 entities, ignoring local entities. The use of this switch may accelerate
15573 @code{gnatfind} and @code{gnatxref}.
15576 @cindex @option{-IDIR} (@command{gnatfind})
15577 Equivalent to @samp{-aODIR -aIDIR}.
15580 @cindex @option{-pFILE} (@command{gnatfind})
15581 Specify a project file (@pxref{Project Files}) to use.
15582 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15583 project file in the current directory.
15585 If a project file is either specified or found by the tools, then the content
15586 of the source directory and object directory lines are added as if they
15587 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15588 @samp{^-aO^/OBJECT_SEARCH^}.
15590 @item ^-r^/REFERENCES^
15591 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15592 By default, @code{gnatfind} will output only the information about the
15593 declaration, body or type completion of the entities. If this switch is
15594 set, the @code{gnatfind} will locate every reference to the entities in
15595 the files specified on the command line (or in every file in the search
15596 path if no file is given on the command line).
15598 @item ^-s^/PRINT_LINES^
15599 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15600 If this switch is set, then @code{gnatfind} will output the content
15601 of the Ada source file lines were the entity was found.
15603 @item ^-t^/TYPE_HIERARCHY^
15604 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15605 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15606 the specified type. It act like -d option but recursively from parent
15607 type to parent type. When this switch is set it is not possible to
15608 specify more than one file.
15613 All these switches may be in any order on the command line, and may even
15614 appear after the file names. They need not be separated by spaces, thus
15615 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15616 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15618 As stated previously, gnatfind will search in every directory in the
15619 search path. You can force it to look only in the current directory if
15620 you specify @code{*} at the end of the command line.
15622 @node Project Files for gnatxref and gnatfind
15623 @section Project Files for @command{gnatxref} and @command{gnatfind}
15626 Project files allow a programmer to specify how to compile its
15627 application, where to find sources, etc. These files are used
15629 primarily by GPS, but they can also be used
15632 @code{gnatxref} and @code{gnatfind}.
15634 A project file name must end with @file{.gpr}. If a single one is
15635 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15636 extract the information from it. If multiple project files are found, none of
15637 them is read, and you have to use the @samp{-p} switch to specify the one
15640 The following lines can be included, even though most of them have default
15641 values which can be used in most cases.
15642 The lines can be entered in any order in the file.
15643 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15644 each line. If you have multiple instances, only the last one is taken into
15649 [default: @code{"^./^[]^"}]
15650 specifies a directory where to look for source files. Multiple @code{src_dir}
15651 lines can be specified and they will be searched in the order they
15655 [default: @code{"^./^[]^"}]
15656 specifies a directory where to look for object and library files. Multiple
15657 @code{obj_dir} lines can be specified, and they will be searched in the order
15660 @item comp_opt=SWITCHES
15661 [default: @code{""}]
15662 creates a variable which can be referred to subsequently by using
15663 the @code{$@{comp_opt@}} notation. This is intended to store the default
15664 switches given to @command{gnatmake} and @command{gcc}.
15666 @item bind_opt=SWITCHES
15667 [default: @code{""}]
15668 creates a variable which can be referred to subsequently by using
15669 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15670 switches given to @command{gnatbind}.
15672 @item link_opt=SWITCHES
15673 [default: @code{""}]
15674 creates a variable which can be referred to subsequently by using
15675 the @samp{$@{link_opt@}} notation. This is intended to store the default
15676 switches given to @command{gnatlink}.
15678 @item main=EXECUTABLE
15679 [default: @code{""}]
15680 specifies the name of the executable for the application. This variable can
15681 be referred to in the following lines by using the @samp{$@{main@}} notation.
15684 @item comp_cmd=COMMAND
15685 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15688 @item comp_cmd=COMMAND
15689 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15691 specifies the command used to compile a single file in the application.
15694 @item make_cmd=COMMAND
15695 [default: @code{"GNAT MAKE $@{main@}
15696 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15697 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15698 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15701 @item make_cmd=COMMAND
15702 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15703 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15704 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15706 specifies the command used to recompile the whole application.
15708 @item run_cmd=COMMAND
15709 [default: @code{"$@{main@}"}]
15710 specifies the command used to run the application.
15712 @item debug_cmd=COMMAND
15713 [default: @code{"gdb $@{main@}"}]
15714 specifies the command used to debug the application
15719 @command{gnatxref} and @command{gnatfind} only take into account the
15720 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15722 @node Regular Expressions in gnatfind and gnatxref
15723 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15726 As specified in the section about @command{gnatfind}, the pattern can be a
15727 regular expression. Actually, there are to set of regular expressions
15728 which are recognized by the program:
15731 @item globbing patterns
15732 These are the most usual regular expression. They are the same that you
15733 generally used in a Unix shell command line, or in a DOS session.
15735 Here is a more formal grammar:
15742 term ::= elmt -- matches elmt
15743 term ::= elmt elmt -- concatenation (elmt then elmt)
15744 term ::= * -- any string of 0 or more characters
15745 term ::= ? -- matches any character
15746 term ::= [char @{char@}] -- matches any character listed
15747 term ::= [char - char] -- matches any character in range
15751 @item full regular expression
15752 The second set of regular expressions is much more powerful. This is the
15753 type of regular expressions recognized by utilities such a @file{grep}.
15755 The following is the form of a regular expression, expressed in Ada
15756 reference manual style BNF is as follows
15763 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15765 term ::= item @{item@} -- concatenation (item then item)
15767 item ::= elmt -- match elmt
15768 item ::= elmt * -- zero or more elmt's
15769 item ::= elmt + -- one or more elmt's
15770 item ::= elmt ? -- matches elmt or nothing
15773 elmt ::= nschar -- matches given character
15774 elmt ::= [nschar @{nschar@}] -- matches any character listed
15775 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15776 elmt ::= [char - char] -- matches chars in given range
15777 elmt ::= \ char -- matches given character
15778 elmt ::= . -- matches any single character
15779 elmt ::= ( regexp ) -- parens used for grouping
15781 char ::= any character, including special characters
15782 nschar ::= any character except ()[].*+?^^^
15786 Following are a few examples:
15790 will match any of the two strings @samp{abcde} and @samp{fghi},
15793 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15794 @samp{abcccd}, and so on,
15797 will match any string which has only lowercase characters in it (and at
15798 least one character.
15803 @node Examples of gnatxref Usage
15804 @section Examples of @code{gnatxref} Usage
15806 @subsection General Usage
15809 For the following examples, we will consider the following units:
15811 @smallexample @c ada
15817 3: procedure Foo (B : in Integer);
15824 1: package body Main is
15825 2: procedure Foo (B : in Integer) is
15836 2: procedure Print (B : Integer);
15845 The first thing to do is to recompile your application (for instance, in
15846 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15847 the cross-referencing information.
15848 You can then issue any of the following commands:
15850 @item gnatxref main.adb
15851 @code{gnatxref} generates cross-reference information for main.adb
15852 and every unit 'with'ed by main.adb.
15854 The output would be:
15862 Decl: main.ads 3:20
15863 Body: main.adb 2:20
15864 Ref: main.adb 4:13 5:13 6:19
15867 Ref: main.adb 6:8 7:8
15877 Decl: main.ads 3:15
15878 Body: main.adb 2:15
15881 Body: main.adb 1:14
15884 Ref: main.adb 6:12 7:12
15888 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15889 its body is in main.adb, line 1, column 14 and is not referenced any where.
15891 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15892 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15894 @item gnatxref package1.adb package2.ads
15895 @code{gnatxref} will generates cross-reference information for
15896 package1.adb, package2.ads and any other package 'with'ed by any
15902 @subsection Using gnatxref with vi
15904 @code{gnatxref} can generate a tags file output, which can be used
15905 directly from @command{vi}. Note that the standard version of @command{vi}
15906 will not work properly with overloaded symbols. Consider using another
15907 free implementation of @command{vi}, such as @command{vim}.
15910 $ gnatxref -v gnatfind.adb > tags
15914 will generate the tags file for @code{gnatfind} itself (if the sources
15915 are in the search path!).
15917 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15918 (replacing @var{entity} by whatever you are looking for), and vi will
15919 display a new file with the corresponding declaration of entity.
15922 @node Examples of gnatfind Usage
15923 @section Examples of @code{gnatfind} Usage
15927 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15928 Find declarations for all entities xyz referenced at least once in
15929 main.adb. The references are search in every library file in the search
15932 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15935 The output will look like:
15937 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15938 ^directory/^[directory]^main.adb:24:10: xyz <= body
15939 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15943 that is to say, one of the entities xyz found in main.adb is declared at
15944 line 12 of main.ads (and its body is in main.adb), and another one is
15945 declared at line 45 of foo.ads
15947 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15948 This is the same command as the previous one, instead @code{gnatfind} will
15949 display the content of the Ada source file lines.
15951 The output will look like:
15954 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15956 ^directory/^[directory]^main.adb:24:10: xyz <= body
15958 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15963 This can make it easier to find exactly the location your are looking
15966 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15967 Find references to all entities containing an x that are
15968 referenced on line 123 of main.ads.
15969 The references will be searched only in main.ads and foo.adb.
15971 @item gnatfind main.ads:123
15972 Find declarations and bodies for all entities that are referenced on
15973 line 123 of main.ads.
15975 This is the same as @code{gnatfind "*":main.adb:123}.
15977 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15978 Find the declaration for the entity referenced at column 45 in
15979 line 123 of file main.adb in directory mydir. Note that it
15980 is usual to omit the identifier name when the column is given,
15981 since the column position identifies a unique reference.
15983 The column has to be the beginning of the identifier, and should not
15984 point to any character in the middle of the identifier.
15988 @c *********************************
15989 @node The GNAT Pretty-Printer gnatpp
15990 @chapter The GNAT Pretty-Printer @command{gnatpp}
15992 @cindex Pretty-Printer
15995 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15996 for source reformatting / pretty-printing.
15997 It takes an Ada source file as input and generates a reformatted
15999 You can specify various style directives via switches; e.g.,
16000 identifier case conventions, rules of indentation, and comment layout.
16002 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
16003 tree for the input source and thus requires the input to be syntactically and
16004 semantically legal.
16005 If this condition is not met, @command{gnatpp} will terminate with an
16006 error message; no output file will be generated.
16008 If the source files presented to @command{gnatpp} contain
16009 preprocessing directives, then the output file will
16010 correspond to the generated source after all
16011 preprocessing is carried out. There is no way
16012 using @command{gnatpp} to obtain pretty printed files that
16013 include the preprocessing directives.
16015 If the compilation unit
16016 contained in the input source depends semantically upon units located
16017 outside the current directory, you have to provide the source search path
16018 when invoking @command{gnatpp}, if these units are contained in files with
16019 names that do not follow the GNAT file naming rules, you have to provide
16020 the configuration file describing the corresponding naming scheme;
16021 see the description of the @command{gnatpp}
16022 switches below. Another possibility is to use a project file and to
16023 call @command{gnatpp} through the @command{gnat} driver
16025 The @command{gnatpp} command has the form
16028 $ gnatpp @ovar{switches} @var{filename}
16035 @var{switches} is an optional sequence of switches defining such properties as
16036 the formatting rules, the source search path, and the destination for the
16040 @var{filename} is the name (including the extension) of the source file to
16041 reformat; ``wildcards'' or several file names on the same gnatpp command are
16042 allowed. The file name may contain path information; it does not have to
16043 follow the GNAT file naming rules
16047 * Switches for gnatpp::
16048 * Formatting Rules::
16051 @node Switches for gnatpp
16052 @section Switches for @command{gnatpp}
16055 The following subsections describe the various switches accepted by
16056 @command{gnatpp}, organized by category.
16059 You specify a switch by supplying a name and generally also a value.
16060 In many cases the values for a switch with a given name are incompatible with
16062 (for example the switch that controls the casing of a reserved word may have
16063 exactly one value: upper case, lower case, or
16064 mixed case) and thus exactly one such switch can be in effect for an
16065 invocation of @command{gnatpp}.
16066 If more than one is supplied, the last one is used.
16067 However, some values for the same switch are mutually compatible.
16068 You may supply several such switches to @command{gnatpp}, but then
16069 each must be specified in full, with both the name and the value.
16070 Abbreviated forms (the name appearing once, followed by each value) are
16072 For example, to set
16073 the alignment of the assignment delimiter both in declarations and in
16074 assignment statements, you must write @option{-A2A3}
16075 (or @option{-A2 -A3}), but not @option{-A23}.
16079 In many cases the set of options for a given qualifier are incompatible with
16080 each other (for example the qualifier that controls the casing of a reserved
16081 word may have exactly one option, which specifies either upper case, lower
16082 case, or mixed case), and thus exactly one such option can be in effect for
16083 an invocation of @command{gnatpp}.
16084 If more than one is supplied, the last one is used.
16085 However, some qualifiers have options that are mutually compatible,
16086 and then you may then supply several such options when invoking
16090 In most cases, it is obvious whether or not the
16091 ^values for a switch with a given name^options for a given qualifier^
16092 are compatible with each other.
16093 When the semantics might not be evident, the summaries below explicitly
16094 indicate the effect.
16097 * Alignment Control::
16099 * Construct Layout Control::
16100 * General Text Layout Control::
16101 * Other Formatting Options::
16102 * Setting the Source Search Path::
16103 * Output File Control::
16104 * Other gnatpp Switches::
16107 @node Alignment Control
16108 @subsection Alignment Control
16109 @cindex Alignment control in @command{gnatpp}
16112 Programs can be easier to read if certain constructs are vertically aligned.
16113 By default all alignments are set ON.
16114 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16115 OFF, and then use one or more of the other
16116 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16117 to activate alignment for specific constructs.
16120 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16124 Set all alignments to ON
16127 @item ^-A0^/ALIGN=OFF^
16128 Set all alignments to OFF
16130 @item ^-A1^/ALIGN=COLONS^
16131 Align @code{:} in declarations
16133 @item ^-A2^/ALIGN=DECLARATIONS^
16134 Align @code{:=} in initializations in declarations
16136 @item ^-A3^/ALIGN=STATEMENTS^
16137 Align @code{:=} in assignment statements
16139 @item ^-A4^/ALIGN=ARROWS^
16140 Align @code{=>} in associations
16142 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16143 Align @code{at} keywords in the component clauses in record
16144 representation clauses
16148 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16151 @node Casing Control
16152 @subsection Casing Control
16153 @cindex Casing control in @command{gnatpp}
16156 @command{gnatpp} allows you to specify the casing for reserved words,
16157 pragma names, attribute designators and identifiers.
16158 For identifiers you may define a
16159 general rule for name casing but also override this rule
16160 via a set of dictionary files.
16162 Three types of casing are supported: lower case, upper case, and mixed case.
16163 Lower and upper case are self-explanatory (but since some letters in
16164 Latin1 and other GNAT-supported character sets
16165 exist only in lower-case form, an upper case conversion will have no
16167 ``Mixed case'' means that the first letter, and also each letter immediately
16168 following an underscore, are converted to their uppercase forms;
16169 all the other letters are converted to their lowercase forms.
16172 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16173 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16174 Attribute designators are lower case
16176 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16177 Attribute designators are upper case
16179 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16180 Attribute designators are mixed case (this is the default)
16182 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16183 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16184 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16185 lower case (this is the default)
16187 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16188 Keywords are upper case
16190 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16191 @item ^-nD^/NAME_CASING=AS_DECLARED^
16192 Name casing for defining occurrences are as they appear in the source file
16193 (this is the default)
16195 @item ^-nU^/NAME_CASING=UPPER_CASE^
16196 Names are in upper case
16198 @item ^-nL^/NAME_CASING=LOWER_CASE^
16199 Names are in lower case
16201 @item ^-nM^/NAME_CASING=MIXED_CASE^
16202 Names are in mixed case
16204 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16205 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16206 Pragma names are lower case
16208 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16209 Pragma names are upper case
16211 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16212 Pragma names are mixed case (this is the default)
16214 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16215 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16216 Use @var{file} as a @emph{dictionary file} that defines
16217 the casing for a set of specified names,
16218 thereby overriding the effect on these names by
16219 any explicit or implicit
16220 ^-n^/NAME_CASING^ switch.
16221 To supply more than one dictionary file,
16222 use ^several @option{-D} switches^a list of files as options^.
16225 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16226 to define the casing for the Ada predefined names and
16227 the names declared in the GNAT libraries.
16229 @item ^-D-^/SPECIFIC_CASING^
16230 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16231 Do not use the default dictionary file;
16232 instead, use the casing
16233 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16238 The structure of a dictionary file, and details on the conventions
16239 used in the default dictionary file, are defined in @ref{Name Casing}.
16241 The @option{^-D-^/SPECIFIC_CASING^} and
16242 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16245 @node Construct Layout Control
16246 @subsection Construct Layout Control
16247 @cindex Layout control in @command{gnatpp}
16250 This group of @command{gnatpp} switches controls the layout of comments and
16251 complex syntactic constructs. See @ref{Formatting Comments} for details
16255 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16256 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16257 All the comments remain unchanged
16259 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16260 GNAT-style comment line indentation (this is the default).
16262 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16263 Reference-manual comment line indentation.
16265 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16266 GNAT-style comment beginning
16268 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16269 Reformat comment blocks
16271 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16272 Keep unchanged special form comments
16274 Reformat comment blocks
16276 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16277 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16278 GNAT-style layout (this is the default)
16280 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16283 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16286 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16288 All the VT characters are removed from the comment text. All the HT characters
16289 are expanded with the sequences of space characters to get to the next tab
16292 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16293 @item ^--no-separate-is^/NO_SEPARATE_IS^
16294 Do not place the keyword @code{is} on a separate line in a subprogram body in
16295 case if the spec occupies more then one line.
16297 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16298 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16299 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16300 keyword @code{then} in IF statements on a separate line.
16302 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16303 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16304 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16305 keyword @code{then} in IF statements on a separate line. This option is
16306 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16308 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16309 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16310 Start each USE clause in a context clause from a separate line.
16312 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16313 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16314 Use a separate line for a loop or block statement name, but do not use an extra
16315 indentation level for the statement itself.
16321 The @option{-c1} and @option{-c2} switches are incompatible.
16322 The @option{-c3} and @option{-c4} switches are compatible with each other and
16323 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16324 the other comment formatting switches.
16326 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16331 For the @option{/COMMENTS_LAYOUT} qualifier:
16334 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16336 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16337 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16341 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16342 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16345 @node General Text Layout Control
16346 @subsection General Text Layout Control
16349 These switches allow control over line length and indentation.
16352 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16353 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16354 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16356 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16357 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16358 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16360 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16361 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16362 Indentation level for continuation lines (relative to the line being
16363 continued), @var{nnn} from 1@dots{}9.
16365 value is one less then the (normal) indentation level, unless the
16366 indentation is set to 1 (in which case the default value for continuation
16367 line indentation is also 1)
16370 @node Other Formatting Options
16371 @subsection Other Formatting Options
16374 These switches control the inclusion of missing end/exit labels, and
16375 the indentation level in @b{case} statements.
16378 @item ^-e^/NO_MISSED_LABELS^
16379 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16380 Do not insert missing end/exit labels. An end label is the name of
16381 a construct that may optionally be repeated at the end of the
16382 construct's declaration;
16383 e.g., the names of packages, subprograms, and tasks.
16384 An exit label is the name of a loop that may appear as target
16385 of an exit statement within the loop.
16386 By default, @command{gnatpp} inserts these end/exit labels when
16387 they are absent from the original source. This option suppresses such
16388 insertion, so that the formatted source reflects the original.
16390 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16391 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16392 Insert a Form Feed character after a pragma Page.
16394 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16395 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16396 Do not use an additional indentation level for @b{case} alternatives
16397 and variants if there are @var{nnn} or more (the default
16399 If @var{nnn} is 0, an additional indentation level is
16400 used for @b{case} alternatives and variants regardless of their number.
16403 @node Setting the Source Search Path
16404 @subsection Setting the Source Search Path
16407 To define the search path for the input source file, @command{gnatpp}
16408 uses the same switches as the GNAT compiler, with the same effects.
16411 @item ^-I^/SEARCH=^@var{dir}
16412 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16413 The same as the corresponding gcc switch
16415 @item ^-I-^/NOCURRENT_DIRECTORY^
16416 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16417 The same as the corresponding gcc switch
16419 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16420 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16421 The same as the corresponding gcc switch
16423 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16424 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16425 The same as the corresponding gcc switch
16429 @node Output File Control
16430 @subsection Output File Control
16433 By default the output is sent to the file whose name is obtained by appending
16434 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16435 (if the file with this name already exists, it is unconditionally overwritten).
16436 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16437 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16439 The output may be redirected by the following switches:
16442 @item ^-pipe^/STANDARD_OUTPUT^
16443 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16444 Send the output to @code{Standard_Output}
16446 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16447 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16448 Write the output into @var{output_file}.
16449 If @var{output_file} already exists, @command{gnatpp} terminates without
16450 reading or processing the input file.
16452 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16453 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16454 Write the output into @var{output_file}, overwriting the existing file
16455 (if one is present).
16457 @item ^-r^/REPLACE^
16458 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16459 Replace the input source file with the reformatted output, and copy the
16460 original input source into the file whose name is obtained by appending the
16461 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16462 If a file with this name already exists, @command{gnatpp} terminates without
16463 reading or processing the input file.
16465 @item ^-rf^/OVERRIDING_REPLACE^
16466 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16467 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16468 already exists, it is overwritten.
16470 @item ^-rnb^/REPLACE_NO_BACKUP^
16471 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16472 Replace the input source file with the reformatted output without
16473 creating any backup copy of the input source.
16475 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16476 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16477 Specifies the format of the reformatted output file. The @var{xxx}
16478 ^string specified with the switch^option^ may be either
16480 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16481 @item ``@option{^crlf^CRLF^}''
16482 the same as @option{^crlf^CRLF^}
16483 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16484 @item ``@option{^lf^LF^}''
16485 the same as @option{^unix^UNIX^}
16488 @item ^-W^/RESULT_ENCODING=^@var{e}
16489 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16490 Specify the wide character encoding method used to write the code in the
16492 @var{e} is one of the following:
16500 Upper half encoding
16502 @item ^s^SHIFT_JIS^
16512 Brackets encoding (default value)
16518 Options @option{^-pipe^/STANDARD_OUTPUT^},
16519 @option{^-o^/OUTPUT^} and
16520 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16521 contains only one file to reformat.
16523 @option{^--eol^/END_OF_LINE^}
16525 @option{^-W^/RESULT_ENCODING^}
16526 cannot be used together
16527 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16529 @node Other gnatpp Switches
16530 @subsection Other @code{gnatpp} Switches
16533 The additional @command{gnatpp} switches are defined in this subsection.
16536 @item ^-files @var{filename}^/FILES=@var{output_file}^
16537 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16538 Take the argument source files from the specified file. This file should be an
16539 ordinary textual file containing file names separated by spaces or
16540 line breaks. You can use this switch more then once in the same call to
16541 @command{gnatpp}. You also can combine this switch with explicit list of
16544 @item ^-v^/VERBOSE^
16545 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16547 @command{gnatpp} generates version information and then
16548 a trace of the actions it takes to produce or obtain the ASIS tree.
16550 @item ^-w^/WARNINGS^
16551 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16553 @command{gnatpp} generates a warning whenever it cannot provide
16554 a required layout in the result source.
16557 @node Formatting Rules
16558 @section Formatting Rules
16561 The following subsections show how @command{gnatpp} treats ``white space'',
16562 comments, program layout, and name casing.
16563 They provide the detailed descriptions of the switches shown above.
16566 * White Space and Empty Lines::
16567 * Formatting Comments::
16568 * Construct Layout::
16572 @node White Space and Empty Lines
16573 @subsection White Space and Empty Lines
16576 @command{gnatpp} does not have an option to control space characters.
16577 It will add or remove spaces according to the style illustrated by the
16578 examples in the @cite{Ada Reference Manual}.
16580 The only format effectors
16581 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16582 that will appear in the output file are platform-specific line breaks,
16583 and also format effectors within (but not at the end of) comments.
16584 In particular, each horizontal tab character that is not inside
16585 a comment will be treated as a space and thus will appear in the
16586 output file as zero or more spaces depending on
16587 the reformatting of the line in which it appears.
16588 The only exception is a Form Feed character, which is inserted after a
16589 pragma @code{Page} when @option{-ff} is set.
16591 The output file will contain no lines with trailing ``white space'' (spaces,
16594 Empty lines in the original source are preserved
16595 only if they separate declarations or statements.
16596 In such contexts, a
16597 sequence of two or more empty lines is replaced by exactly one empty line.
16598 Note that a blank line will be removed if it separates two ``comment blocks''
16599 (a comment block is a sequence of whole-line comments).
16600 In order to preserve a visual separation between comment blocks, use an
16601 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16602 Likewise, if for some reason you wish to have a sequence of empty lines,
16603 use a sequence of empty comments instead.
16605 @node Formatting Comments
16606 @subsection Formatting Comments
16609 Comments in Ada code are of two kinds:
16612 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16613 ``white space'') on a line
16616 an @emph{end-of-line comment}, which follows some other Ada lexical element
16621 The indentation of a whole-line comment is that of either
16622 the preceding or following line in
16623 the formatted source, depending on switch settings as will be described below.
16625 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16626 between the end of the preceding Ada lexical element and the beginning
16627 of the comment as appear in the original source,
16628 unless either the comment has to be split to
16629 satisfy the line length limitation, or else the next line contains a
16630 whole line comment that is considered a continuation of this end-of-line
16631 comment (because it starts at the same position).
16633 cases, the start of the end-of-line comment is moved right to the nearest
16634 multiple of the indentation level.
16635 This may result in a ``line overflow'' (the right-shifted comment extending
16636 beyond the maximum line length), in which case the comment is split as
16639 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16640 (GNAT-style comment line indentation)
16641 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16642 (reference-manual comment line indentation).
16643 With reference-manual style, a whole-line comment is indented as if it
16644 were a declaration or statement at the same place
16645 (i.e., according to the indentation of the preceding line(s)).
16646 With GNAT style, a whole-line comment that is immediately followed by an
16647 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16648 word @b{begin}, is indented based on the construct that follows it.
16651 @smallexample @c ada
16663 Reference-manual indentation produces:
16665 @smallexample @c ada
16677 while GNAT-style indentation produces:
16679 @smallexample @c ada
16691 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16692 (GNAT style comment beginning) has the following
16697 For each whole-line comment that does not end with two hyphens,
16698 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16699 to ensure that there are at least two spaces between these hyphens and the
16700 first non-blank character of the comment.
16704 For an end-of-line comment, if in the original source the next line is a
16705 whole-line comment that starts at the same position
16706 as the end-of-line comment,
16707 then the whole-line comment (and all whole-line comments
16708 that follow it and that start at the same position)
16709 will start at this position in the output file.
16712 That is, if in the original source we have:
16714 @smallexample @c ada
16717 A := B + C; -- B must be in the range Low1..High1
16718 -- C must be in the range Low2..High2
16719 --B+C will be in the range Low1+Low2..High1+High2
16725 Then in the formatted source we get
16727 @smallexample @c ada
16730 A := B + C; -- B must be in the range Low1..High1
16731 -- C must be in the range Low2..High2
16732 -- B+C will be in the range Low1+Low2..High1+High2
16738 A comment that exceeds the line length limit will be split.
16740 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16741 the line belongs to a reformattable block, splitting the line generates a
16742 @command{gnatpp} warning.
16743 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16744 comments may be reformatted in typical
16745 word processor style (that is, moving words between lines and putting as
16746 many words in a line as possible).
16749 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16750 that has a special format (that is, a character that is neither a letter nor digit
16751 not white space nor line break immediately following the leading @code{--} of
16752 the comment) should be without any change moved from the argument source
16753 into reformatted source. This switch allows to preserve comments that are used
16754 as a special marks in the code (e.g.@: SPARK annotation).
16756 @node Construct Layout
16757 @subsection Construct Layout
16760 In several cases the suggested layout in the Ada Reference Manual includes
16761 an extra level of indentation that many programmers prefer to avoid. The
16762 affected cases include:
16766 @item Record type declaration (RM 3.8)
16768 @item Record representation clause (RM 13.5.1)
16770 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16772 @item Block statement in case if a block has a statement identifier (RM 5.6)
16776 In compact mode (when GNAT style layout or compact layout is set),
16777 the pretty printer uses one level of indentation instead
16778 of two. This is achieved in the record definition and record representation
16779 clause cases by putting the @code{record} keyword on the same line as the
16780 start of the declaration or representation clause, and in the block and loop
16781 case by putting the block or loop header on the same line as the statement
16785 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16786 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16787 layout on the one hand, and uncompact layout
16788 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16789 can be illustrated by the following examples:
16793 @multitable @columnfractions .5 .5
16794 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16797 @smallexample @c ada
16804 @smallexample @c ada
16813 @smallexample @c ada
16815 a at 0 range 0 .. 31;
16816 b at 4 range 0 .. 31;
16820 @smallexample @c ada
16823 a at 0 range 0 .. 31;
16824 b at 4 range 0 .. 31;
16829 @smallexample @c ada
16837 @smallexample @c ada
16847 @smallexample @c ada
16848 Clear : for J in 1 .. 10 loop
16853 @smallexample @c ada
16855 for J in 1 .. 10 loop
16866 GNAT style, compact layout Uncompact layout
16868 type q is record type q is
16869 a : integer; record
16870 b : integer; a : integer;
16871 end record; b : integer;
16874 for q use record for q use
16875 a at 0 range 0 .. 31; record
16876 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16877 end record; b at 4 range 0 .. 31;
16880 Block : declare Block :
16881 A : Integer := 3; declare
16882 begin A : Integer := 3;
16884 end Block; Proc (A, A);
16887 Clear : for J in 1 .. 10 loop Clear :
16888 A (J) := 0; for J in 1 .. 10 loop
16889 end loop Clear; A (J) := 0;
16896 A further difference between GNAT style layout and compact layout is that
16897 GNAT style layout inserts empty lines as separation for
16898 compound statements, return statements and bodies.
16900 Note that the layout specified by
16901 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16902 for named block and loop statements overrides the layout defined by these
16903 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16904 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16905 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16908 @subsection Name Casing
16911 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16912 the same casing as the corresponding defining identifier.
16914 You control the casing for defining occurrences via the
16915 @option{^-n^/NAME_CASING^} switch.
16917 With @option{-nD} (``as declared'', which is the default),
16920 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16922 defining occurrences appear exactly as in the source file
16923 where they are declared.
16924 The other ^values for this switch^options for this qualifier^ ---
16925 @option{^-nU^UPPER_CASE^},
16926 @option{^-nL^LOWER_CASE^},
16927 @option{^-nM^MIXED_CASE^} ---
16929 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16930 If @command{gnatpp} changes the casing of a defining
16931 occurrence, it analogously changes the casing of all the
16932 usage occurrences of this name.
16934 If the defining occurrence of a name is not in the source compilation unit
16935 currently being processed by @command{gnatpp}, the casing of each reference to
16936 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16937 switch (subject to the dictionary file mechanism described below).
16938 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16940 casing for the defining occurrence of the name.
16942 Some names may need to be spelled with casing conventions that are not
16943 covered by the upper-, lower-, and mixed-case transformations.
16944 You can arrange correct casing by placing such names in a
16945 @emph{dictionary file},
16946 and then supplying a @option{^-D^/DICTIONARY^} switch.
16947 The casing of names from dictionary files overrides
16948 any @option{^-n^/NAME_CASING^} switch.
16950 To handle the casing of Ada predefined names and the names from GNAT libraries,
16951 @command{gnatpp} assumes a default dictionary file.
16952 The name of each predefined entity is spelled with the same casing as is used
16953 for the entity in the @cite{Ada Reference Manual}.
16954 The name of each entity in the GNAT libraries is spelled with the same casing
16955 as is used in the declaration of that entity.
16957 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16958 default dictionary file.
16959 Instead, the casing for predefined and GNAT-defined names will be established
16960 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16961 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16962 will appear as just shown,
16963 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16964 To ensure that even such names are rendered in uppercase,
16965 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16966 (or else, less conveniently, place these names in upper case in a dictionary
16969 A dictionary file is
16970 a plain text file; each line in this file can be either a blank line
16971 (containing only space characters and ASCII.HT characters), an Ada comment
16972 line, or the specification of exactly one @emph{casing schema}.
16974 A casing schema is a string that has the following syntax:
16978 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16980 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16985 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16986 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16988 The casing schema string can be followed by white space and/or an Ada-style
16989 comment; any amount of white space is allowed before the string.
16991 If a dictionary file is passed as
16993 the value of a @option{-D@var{file}} switch
16996 an option to the @option{/DICTIONARY} qualifier
16999 simple name and every identifier, @command{gnatpp} checks if the dictionary
17000 defines the casing for the name or for some of its parts (the term ``subword''
17001 is used below to denote the part of a name which is delimited by ``_'' or by
17002 the beginning or end of the word and which does not contain any ``_'' inside):
17006 if the whole name is in the dictionary, @command{gnatpp} uses for this name
17007 the casing defined by the dictionary; no subwords are checked for this word
17010 for every subword @command{gnatpp} checks if the dictionary contains the
17011 corresponding string of the form @code{*@var{simple_identifier}*},
17012 and if it does, the casing of this @var{simple_identifier} is used
17016 if the whole name does not contain any ``_'' inside, and if for this name
17017 the dictionary contains two entries - one of the form @var{identifier},
17018 and another - of the form *@var{simple_identifier}*, then the first one
17019 is applied to define the casing of this name
17022 if more than one dictionary file is passed as @command{gnatpp} switches, each
17023 dictionary adds new casing exceptions and overrides all the existing casing
17024 exceptions set by the previous dictionaries
17027 when @command{gnatpp} checks if the word or subword is in the dictionary,
17028 this check is not case sensitive
17032 For example, suppose we have the following source to reformat:
17034 @smallexample @c ada
17037 name1 : integer := 1;
17038 name4_name3_name2 : integer := 2;
17039 name2_name3_name4 : Boolean;
17042 name2_name3_name4 := name4_name3_name2 > name1;
17048 And suppose we have two dictionaries:
17065 If @command{gnatpp} is called with the following switches:
17069 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17072 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17077 then we will get the following name casing in the @command{gnatpp} output:
17079 @smallexample @c ada
17082 NAME1 : Integer := 1;
17083 Name4_NAME3_Name2 : Integer := 2;
17084 Name2_NAME3_Name4 : Boolean;
17087 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17092 @c *********************************
17093 @node The GNAT Metric Tool gnatmetric
17094 @chapter The GNAT Metric Tool @command{gnatmetric}
17096 @cindex Metric tool
17099 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17100 for computing various program metrics.
17101 It takes an Ada source file as input and generates a file containing the
17102 metrics data as output. Various switches control which
17103 metrics are computed and output.
17105 @command{gnatmetric} generates and uses the ASIS
17106 tree for the input source and thus requires the input to be syntactically and
17107 semantically legal.
17108 If this condition is not met, @command{gnatmetric} will generate
17109 an error message; no metric information for this file will be
17110 computed and reported.
17112 If the compilation unit contained in the input source depends semantically
17113 upon units in files located outside the current directory, you have to provide
17114 the source search path when invoking @command{gnatmetric}.
17115 If it depends semantically upon units that are contained
17116 in files with names that do not follow the GNAT file naming rules, you have to
17117 provide the configuration file describing the corresponding naming scheme (see
17118 the description of the @command{gnatmetric} switches below.)
17119 Alternatively, you may use a project file and invoke @command{gnatmetric}
17120 through the @command{gnat} driver.
17122 The @command{gnatmetric} command has the form
17125 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17132 @var{switches} specify the metrics to compute and define the destination for
17136 Each @var{filename} is the name (including the extension) of a source
17137 file to process. ``Wildcards'' are allowed, and
17138 the file name may contain path information.
17139 If no @var{filename} is supplied, then the @var{switches} list must contain
17141 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17142 Including both a @option{-files} switch and one or more
17143 @var{filename} arguments is permitted.
17146 @samp{-cargs @var{gcc_switches}} is a list of switches for
17147 @command{gcc}. They will be passed on to all compiler invocations made by
17148 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17149 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17150 and use the @option{-gnatec} switch to set the configuration file.
17154 * Switches for gnatmetric::
17157 @node Switches for gnatmetric
17158 @section Switches for @command{gnatmetric}
17161 The following subsections describe the various switches accepted by
17162 @command{gnatmetric}, organized by category.
17165 * Output Files Control::
17166 * Disable Metrics For Local Units::
17167 * Specifying a set of metrics to compute::
17168 * Other gnatmetric Switches::
17169 * Generate project-wide metrics::
17172 @node Output Files Control
17173 @subsection Output File Control
17174 @cindex Output file control in @command{gnatmetric}
17177 @command{gnatmetric} has two output formats. It can generate a
17178 textual (human-readable) form, and also XML. By default only textual
17179 output is generated.
17181 When generating the output in textual form, @command{gnatmetric} creates
17182 for each Ada source file a corresponding text file
17183 containing the computed metrics, except for the case when the set of metrics
17184 specified by gnatmetric parameters consists only of metrics that are computed
17185 for the whole set of analyzed sources, but not for each Ada source.
17186 By default, this file is placed in the same directory as where the source
17187 file is located, and its name is obtained
17188 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17191 All the output information generated in XML format is placed in a single
17192 file. By default this file is placed in the current directory and has the
17193 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17195 Some of the computed metrics are summed over the units passed to
17196 @command{gnatmetric}; for example, the total number of lines of code.
17197 By default this information is sent to @file{stdout}, but a file
17198 can be specified with the @option{-og} switch.
17200 The following switches control the @command{gnatmetric} output:
17203 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17205 Generate the XML output
17207 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17209 Generate the XML output and the XML schema file that describes the structure
17210 of the XML metric report, this schema is assigned to the XML file. The schema
17211 file has the same name as the XML output file with @file{.xml} suffix replaced
17214 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17215 @item ^-nt^/NO_TEXT^
17216 Do not generate the output in text form (implies @option{^-x^/XML^})
17218 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17219 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17220 Put textual files with detailed metrics into @var{output_dir}
17222 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17223 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17224 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17225 in the name of the output file.
17227 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17228 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17229 Put global metrics into @var{file_name}
17231 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17232 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17233 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17235 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17236 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17237 Use ``short'' source file names in the output. (The @command{gnatmetric}
17238 output includes the name(s) of the Ada source file(s) from which the metrics
17239 are computed. By default each name includes the absolute path. The
17240 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17241 to exclude all directory information from the file names that are output.)
17245 @node Disable Metrics For Local Units
17246 @subsection Disable Metrics For Local Units
17247 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17250 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17252 unit per one source file. It computes line metrics for the whole source
17253 file, and it also computes syntax
17254 and complexity metrics for the file's outermost unit.
17256 By default, @command{gnatmetric} will also compute all metrics for certain
17257 kinds of locally declared program units:
17261 subprogram (and generic subprogram) bodies;
17264 package (and generic package) specs and bodies;
17267 task object and type specifications and bodies;
17270 protected object and type specifications and bodies.
17274 These kinds of entities will be referred to as
17275 @emph{eligible local program units}, or simply @emph{eligible local units},
17276 @cindex Eligible local unit (for @command{gnatmetric})
17277 in the discussion below.
17279 Note that a subprogram declaration, generic instantiation,
17280 or renaming declaration only receives metrics
17281 computation when it appear as the outermost entity
17284 Suppression of metrics computation for eligible local units can be
17285 obtained via the following switch:
17288 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17289 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17290 Do not compute detailed metrics for eligible local program units
17294 @node Specifying a set of metrics to compute
17295 @subsection Specifying a set of metrics to compute
17298 By default all the metrics are computed and reported. The switches
17299 described in this subsection allow you to control, on an individual
17300 basis, whether metrics are computed and
17301 reported. If at least one positive metric
17302 switch is specified (that is, a switch that defines that a given
17303 metric or set of metrics is to be computed), then only
17304 explicitly specified metrics are reported.
17307 * Line Metrics Control::
17308 * Syntax Metrics Control::
17309 * Complexity Metrics Control::
17310 * Object-Oriented Metrics Control::
17313 @node Line Metrics Control
17314 @subsubsection Line Metrics Control
17315 @cindex Line metrics control in @command{gnatmetric}
17318 For any (legal) source file, and for each of its
17319 eligible local program units, @command{gnatmetric} computes the following
17324 the total number of lines;
17327 the total number of code lines (i.e., non-blank lines that are not comments)
17330 the number of comment lines
17333 the number of code lines containing end-of-line comments;
17336 the comment percentage: the ratio between the number of lines that contain
17337 comments and the number of all non-blank lines, expressed as a percentage;
17340 the number of empty lines and lines containing only space characters and/or
17341 format effectors (blank lines)
17344 the average number of code lines in subprogram bodies, task bodies, entry
17345 bodies and statement sequences in package bodies (this metric is only computed
17346 across the whole set of the analyzed units)
17351 @command{gnatmetric} sums the values of the line metrics for all the
17352 files being processed and then generates the cumulative results. The tool
17353 also computes for all the files being processed the average number of code
17356 You can use the following switches to select the specific line metrics
17357 to be computed and reported.
17360 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17363 @cindex @option{--no-lines@var{x}}
17366 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17367 Report all the line metrics
17369 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17370 Do not report any of line metrics
17372 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17373 Report the number of all lines
17375 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17376 Do not report the number of all lines
17378 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17379 Report the number of code lines
17381 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17382 Do not report the number of code lines
17384 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17385 Report the number of comment lines
17387 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17388 Do not report the number of comment lines
17390 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17391 Report the number of code lines containing
17392 end-of-line comments
17394 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17395 Do not report the number of code lines containing
17396 end-of-line comments
17398 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17399 Report the comment percentage in the program text
17401 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17402 Do not report the comment percentage in the program text
17404 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17405 Report the number of blank lines
17407 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17408 Do not report the number of blank lines
17410 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17411 Report the average number of code lines in subprogram bodies, task bodies,
17412 entry bodies and statement sequences in package bodies. The metric is computed
17413 and reported for the whole set of processed Ada sources only.
17415 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17416 Do not report the average number of code lines in subprogram bodies,
17417 task bodies, entry bodies and statement sequences in package bodies.
17421 @node Syntax Metrics Control
17422 @subsubsection Syntax Metrics Control
17423 @cindex Syntax metrics control in @command{gnatmetric}
17426 @command{gnatmetric} computes various syntactic metrics for the
17427 outermost unit and for each eligible local unit:
17430 @item LSLOC (``Logical Source Lines Of Code'')
17431 The total number of declarations and the total number of statements
17433 @item Maximal static nesting level of inner program units
17435 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17436 package, a task unit, a protected unit, a
17437 protected entry, a generic unit, or an explicitly declared subprogram other
17438 than an enumeration literal.''
17440 @item Maximal nesting level of composite syntactic constructs
17441 This corresponds to the notion of the
17442 maximum nesting level in the GNAT built-in style checks
17443 (@pxref{Style Checking})
17447 For the outermost unit in the file, @command{gnatmetric} additionally computes
17448 the following metrics:
17451 @item Public subprograms
17452 This metric is computed for package specs. It is the
17453 number of subprograms and generic subprograms declared in the visible
17454 part (including the visible part of nested packages, protected objects, and
17457 @item All subprograms
17458 This metric is computed for bodies and subunits. The
17459 metric is equal to a total number of subprogram bodies in the compilation
17461 Neither generic instantiations nor renamings-as-a-body nor body stubs
17462 are counted. Any subprogram body is counted, independently of its nesting
17463 level and enclosing constructs. Generic bodies and bodies of protected
17464 subprograms are counted in the same way as ``usual'' subprogram bodies.
17467 This metric is computed for package specs and
17468 generic package declarations. It is the total number of types
17469 that can be referenced from outside this compilation unit, plus the
17470 number of types from all the visible parts of all the visible generic
17471 packages. Generic formal types are not counted. Only types, not subtypes,
17475 Along with the total number of public types, the following
17476 types are counted and reported separately:
17483 Root tagged types (abstract, non-abstract, private, non-private). Type
17484 extensions are @emph{not} counted
17487 Private types (including private extensions)
17498 This metric is computed for any compilation unit. It is equal to the total
17499 number of the declarations of different types given in the compilation unit.
17500 The private and the corresponding full type declaration are counted as one
17501 type declaration. Incomplete type declarations and generic formal types
17503 No distinction is made among different kinds of types (abstract,
17504 private etc.); the total number of types is computed and reported.
17509 By default, all the syntax metrics are computed and reported. You can use the
17510 following switches to select specific syntax metrics.
17514 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17517 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17520 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17521 Report all the syntax metrics
17523 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17524 Do not report any of syntax metrics
17526 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17527 Report the total number of declarations
17529 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17530 Do not report the total number of declarations
17532 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17533 Report the total number of statements
17535 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17536 Do not report the total number of statements
17538 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17539 Report the number of public subprograms in a compilation unit
17541 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17542 Do not report the number of public subprograms in a compilation unit
17544 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17545 Report the number of all the subprograms in a compilation unit
17547 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17548 Do not report the number of all the subprograms in a compilation unit
17550 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17551 Report the number of public types in a compilation unit
17553 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17554 Do not report the number of public types in a compilation unit
17556 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17557 Report the number of all the types in a compilation unit
17559 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17560 Do not report the number of all the types in a compilation unit
17562 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17563 Report the maximal program unit nesting level
17565 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17566 Do not report the maximal program unit nesting level
17568 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17569 Report the maximal construct nesting level
17571 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17572 Do not report the maximal construct nesting level
17576 @node Complexity Metrics Control
17577 @subsubsection Complexity Metrics Control
17578 @cindex Complexity metrics control in @command{gnatmetric}
17581 For a program unit that is an executable body (a subprogram body (including
17582 generic bodies), task body, entry body or a package body containing
17583 its own statement sequence) @command{gnatmetric} computes the following
17584 complexity metrics:
17588 McCabe cyclomatic complexity;
17591 McCabe essential complexity;
17594 maximal loop nesting level
17599 The McCabe complexity metrics are defined
17600 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17602 According to McCabe, both control statements and short-circuit control forms
17603 should be taken into account when computing cyclomatic complexity. For each
17604 body, we compute three metric values:
17608 the complexity introduced by control
17609 statements only, without taking into account short-circuit forms,
17612 the complexity introduced by short-circuit control forms only, and
17616 cyclomatic complexity, which is the sum of these two values.
17620 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17621 the code in the exception handlers and in all the nested program units.
17623 By default, all the complexity metrics are computed and reported.
17624 For more fine-grained control you can use
17625 the following switches:
17628 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17631 @cindex @option{--no-complexity@var{x}}
17634 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17635 Report all the complexity metrics
17637 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17638 Do not report any of complexity metrics
17640 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17641 Report the McCabe Cyclomatic Complexity
17643 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17644 Do not report the McCabe Cyclomatic Complexity
17646 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17647 Report the Essential Complexity
17649 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17650 Do not report the Essential Complexity
17652 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17653 Report maximal loop nesting level
17655 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17656 Do not report maximal loop nesting level
17658 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17659 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17660 task bodies, entry bodies and statement sequences in package bodies.
17661 The metric is computed and reported for whole set of processed Ada sources
17664 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17665 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17666 bodies, task bodies, entry bodies and statement sequences in package bodies
17668 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17669 @item ^-ne^/NO_EXITS_AS_GOTOS^
17670 Do not consider @code{exit} statements as @code{goto}s when
17671 computing Essential Complexity
17673 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17674 Report the extra exit points for subprogram bodies. As an exit point, this
17675 metric counts @code{return} statements and raise statements in case when the
17676 raised exception is not handled in the same body. In case of a function this
17677 metric subtracts 1 from the number of exit points, because a function body
17678 must contain at least one @code{return} statement.
17680 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17681 Do not report the extra exit points for subprogram bodies
17685 @node Object-Oriented Metrics Control
17686 @subsubsection Object-Oriented Metrics Control
17687 @cindex Object-Oriented metrics control in @command{gnatmetric}
17690 @cindex Coupling metrics (in in @command{gnatmetric})
17691 Coupling metrics are object-oriented metrics that measure the
17692 dependencies between a given class (or a group of classes) and the
17693 ``external world'' (that is, the other classes in the program). In this
17694 subsection the term ``class'' is used in its
17695 traditional object-oriented programming sense
17696 (an instantiable module that contains data and/or method members).
17697 A @emph{category} (of classes)
17698 is a group of closely related classes that are reused and/or
17701 A class @code{K}'s @emph{efferent coupling} is the number of classes
17702 that @code{K} depends upon.
17703 A category's efferent coupling is the number of classes outside the
17704 category that the classes inside the category depend upon.
17706 A class @code{K}'s @emph{afferent coupling} is the number of classes
17707 that depend upon @code{K}.
17708 A category's afferent coupling is the number of classes outside the
17709 category that depend on classes belonging to the category.
17711 Ada's implementation of the object-oriented paradigm does not use the
17712 traditional class notion, so the definition of the coupling
17713 metrics for Ada maps the class and class category notions
17714 onto Ada constructs.
17716 For the coupling metrics, several kinds of modules -- a library package,
17717 a library generic package, and a library generic package instantiation --
17718 that define a tagged type or an interface type are
17719 considered to be a class. A category consists of a library package (or
17720 a library generic package) that defines a tagged or an interface type,
17721 together with all its descendant (generic) packages that define tagged
17722 or interface types. For any package counted as a class,
17723 its body and subunits (if any) are considered
17724 together with its spec when counting the dependencies, and coupling
17725 metrics are reported for spec units only. For dependencies
17726 between classes, the Ada semantic dependencies are considered.
17727 For coupling metrics, only dependencies on units that are considered as
17728 classes, are considered.
17730 When computing coupling metrics, @command{gnatmetric} counts only
17731 dependencies between units that are arguments of the gnatmetric call.
17732 Coupling metrics are program-wide (or project-wide) metrics, so to
17733 get a valid result, you should call @command{gnatmetric} for
17734 the whole set of sources that make up your program. It can be done
17735 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17736 option (see See @ref{The GNAT Driver and Project Files} for details.
17738 By default, all the coupling metrics are disabled. You can use the following
17739 switches to specify the coupling metrics to be computed and reported:
17744 @cindex @option{--package@var{x}} (@command{gnatmetric})
17745 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17746 @cindex @option{--category@var{x}} (@command{gnatmetric})
17747 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17751 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17754 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17755 Report all the coupling metrics
17757 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17758 Do not report any of metrics
17760 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17761 Report package efferent coupling
17763 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17764 Do not report package efferent coupling
17766 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17767 Report package afferent coupling
17769 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17770 Do not report package afferent coupling
17772 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17773 Report category efferent coupling
17775 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17776 Do not report category efferent coupling
17778 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17779 Report category afferent coupling
17781 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17782 Do not report category afferent coupling
17786 @node Other gnatmetric Switches
17787 @subsection Other @code{gnatmetric} Switches
17790 Additional @command{gnatmetric} switches are as follows:
17793 @item ^-files @var{filename}^/FILES=@var{filename}^
17794 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17795 Take the argument source files from the specified file. This file should be an
17796 ordinary text file containing file names separated by spaces or
17797 line breaks. You can use this switch more then once in the same call to
17798 @command{gnatmetric}. You also can combine this switch with
17799 an explicit list of files.
17801 @item ^-v^/VERBOSE^
17802 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17804 @command{gnatmetric} generates version information and then
17805 a trace of sources being processed.
17807 @item ^-dv^/DEBUG_OUTPUT^
17808 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17810 @command{gnatmetric} generates various messages useful to understand what
17811 happens during the metrics computation
17814 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17818 @node Generate project-wide metrics
17819 @subsection Generate project-wide metrics
17821 In order to compute metrics on all units of a given project, you can use
17822 the @command{gnat} driver along with the @option{-P} option:
17828 If the project @code{proj} depends upon other projects, you can compute
17829 the metrics on the project closure using the @option{-U} option:
17831 gnat metric -Pproj -U
17835 Finally, if not all the units are relevant to a particular main
17836 program in the project closure, you can generate metrics for the set
17837 of units needed to create a given main program (unit closure) using
17838 the @option{-U} option followed by the name of the main unit:
17840 gnat metric -Pproj -U main
17844 @c ***********************************
17845 @node File Name Krunching Using gnatkr
17846 @chapter File Name Krunching Using @code{gnatkr}
17850 This chapter discusses the method used by the compiler to shorten
17851 the default file names chosen for Ada units so that they do not
17852 exceed the maximum length permitted. It also describes the
17853 @code{gnatkr} utility that can be used to determine the result of
17854 applying this shortening.
17858 * Krunching Method::
17859 * Examples of gnatkr Usage::
17863 @section About @code{gnatkr}
17866 The default file naming rule in GNAT
17867 is that the file name must be derived from
17868 the unit name. The exact default rule is as follows:
17871 Take the unit name and replace all dots by hyphens.
17873 If such a replacement occurs in the
17874 second character position of a name, and the first character is
17875 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17876 then replace the dot by the character
17877 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17878 instead of a minus.
17880 The reason for this exception is to avoid clashes
17881 with the standard names for children of System, Ada, Interfaces,
17882 and GNAT, which use the prefixes
17883 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17886 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17887 switch of the compiler activates a ``krunching''
17888 circuit that limits file names to nn characters (where nn is a decimal
17889 integer). For example, using OpenVMS,
17890 where the maximum file name length is
17891 39, the value of nn is usually set to 39, but if you want to generate
17892 a set of files that would be usable if ported to a system with some
17893 different maximum file length, then a different value can be specified.
17894 The default value of 39 for OpenVMS need not be specified.
17896 The @code{gnatkr} utility can be used to determine the krunched name for
17897 a given file, when krunched to a specified maximum length.
17900 @section Using @code{gnatkr}
17903 The @code{gnatkr} command has the form
17907 $ gnatkr @var{name} @ovar{length}
17913 $ gnatkr @var{name} /COUNT=nn
17918 @var{name} is the uncrunched file name, derived from the name of the unit
17919 in the standard manner described in the previous section (i.e., in particular
17920 all dots are replaced by hyphens). The file name may or may not have an
17921 extension (defined as a suffix of the form period followed by arbitrary
17922 characters other than period). If an extension is present then it will
17923 be preserved in the output. For example, when krunching @file{hellofile.ads}
17924 to eight characters, the result will be hellofil.ads.
17926 Note: for compatibility with previous versions of @code{gnatkr} dots may
17927 appear in the name instead of hyphens, but the last dot will always be
17928 taken as the start of an extension. So if @code{gnatkr} is given an argument
17929 such as @file{Hello.World.adb} it will be treated exactly as if the first
17930 period had been a hyphen, and for example krunching to eight characters
17931 gives the result @file{hellworl.adb}.
17933 Note that the result is always all lower case (except on OpenVMS where it is
17934 all upper case). Characters of the other case are folded as required.
17936 @var{length} represents the length of the krunched name. The default
17937 when no argument is given is ^8^39^ characters. A length of zero stands for
17938 unlimited, in other words do not chop except for system files where the
17939 implied crunching length is always eight characters.
17942 The output is the krunched name. The output has an extension only if the
17943 original argument was a file name with an extension.
17945 @node Krunching Method
17946 @section Krunching Method
17949 The initial file name is determined by the name of the unit that the file
17950 contains. The name is formed by taking the full expanded name of the
17951 unit and replacing the separating dots with hyphens and
17952 using ^lowercase^uppercase^
17953 for all letters, except that a hyphen in the second character position is
17954 replaced by a ^tilde^dollar sign^ if the first character is
17955 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17956 The extension is @code{.ads} for a
17957 spec and @code{.adb} for a body.
17958 Krunching does not affect the extension, but the file name is shortened to
17959 the specified length by following these rules:
17963 The name is divided into segments separated by hyphens, tildes or
17964 underscores and all hyphens, tildes, and underscores are
17965 eliminated. If this leaves the name short enough, we are done.
17968 If the name is too long, the longest segment is located (left-most
17969 if there are two of equal length), and shortened by dropping
17970 its last character. This is repeated until the name is short enough.
17972 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17973 to fit the name into 8 characters as required by some operating systems.
17976 our-strings-wide_fixed 22
17977 our strings wide fixed 19
17978 our string wide fixed 18
17979 our strin wide fixed 17
17980 our stri wide fixed 16
17981 our stri wide fixe 15
17982 our str wide fixe 14
17983 our str wid fixe 13
17989 Final file name: oustwifi.adb
17993 The file names for all predefined units are always krunched to eight
17994 characters. The krunching of these predefined units uses the following
17995 special prefix replacements:
17999 replaced by @file{^a^A^-}
18002 replaced by @file{^g^G^-}
18005 replaced by @file{^i^I^-}
18008 replaced by @file{^s^S^-}
18011 These system files have a hyphen in the second character position. That
18012 is why normal user files replace such a character with a
18013 ^tilde^dollar sign^, to
18014 avoid confusion with system file names.
18016 As an example of this special rule, consider
18017 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18020 ada-strings-wide_fixed 22
18021 a- strings wide fixed 18
18022 a- string wide fixed 17
18023 a- strin wide fixed 16
18024 a- stri wide fixed 15
18025 a- stri wide fixe 14
18026 a- str wide fixe 13
18032 Final file name: a-stwifi.adb
18036 Of course no file shortening algorithm can guarantee uniqueness over all
18037 possible unit names, and if file name krunching is used then it is your
18038 responsibility to ensure that no name clashes occur. The utility
18039 program @code{gnatkr} is supplied for conveniently determining the
18040 krunched name of a file.
18042 @node Examples of gnatkr Usage
18043 @section Examples of @code{gnatkr} Usage
18050 $ gnatkr very_long_unit_name.ads --> velounna.ads
18051 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18052 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18053 $ gnatkr grandparent-parent-child --> grparchi
18055 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18056 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18059 @node Preprocessing Using gnatprep
18060 @chapter Preprocessing Using @code{gnatprep}
18064 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18066 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18067 special GNAT features.
18068 For further discussion of conditional compilation in general, see
18069 @ref{Conditional Compilation}.
18072 * Preprocessing Symbols::
18074 * Switches for gnatprep::
18075 * Form of Definitions File::
18076 * Form of Input Text for gnatprep::
18079 @node Preprocessing Symbols
18080 @section Preprocessing Symbols
18083 Preprocessing symbols are defined in definition files and referred to in
18084 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18085 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18086 all characters need to be in the ASCII set (no accented letters).
18088 @node Using gnatprep
18089 @section Using @code{gnatprep}
18092 To call @code{gnatprep} use
18095 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18102 is an optional sequence of switches as described in the next section.
18105 is the full name of the input file, which is an Ada source
18106 file containing preprocessor directives.
18109 is the full name of the output file, which is an Ada source
18110 in standard Ada form. When used with GNAT, this file name will
18111 normally have an ads or adb suffix.
18114 is the full name of a text file containing definitions of
18115 preprocessing symbols to be referenced by the preprocessor. This argument is
18116 optional, and can be replaced by the use of the @option{-D} switch.
18120 @node Switches for gnatprep
18121 @section Switches for @code{gnatprep}
18126 @item ^-b^/BLANK_LINES^
18127 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18128 Causes both preprocessor lines and the lines deleted by
18129 preprocessing to be replaced by blank lines in the output source file,
18130 preserving line numbers in the output file.
18132 @item ^-c^/COMMENTS^
18133 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18134 Causes both preprocessor lines and the lines deleted
18135 by preprocessing to be retained in the output source as comments marked
18136 with the special string @code{"--! "}. This option will result in line numbers
18137 being preserved in the output file.
18139 @item ^-C^/REPLACE_IN_COMMENTS^
18140 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18141 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18142 If this option is specified, then comments are scanned and any $symbol
18143 substitutions performed as in program text. This is particularly useful
18144 when structured comments are used (e.g., when writing programs in the
18145 SPARK dialect of Ada). Note that this switch is not available when
18146 doing integrated preprocessing (it would be useless in this context
18147 since comments are ignored by the compiler in any case).
18149 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18150 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18151 Defines a new preprocessing symbol, associated with value. If no value is given
18152 on the command line, then symbol is considered to be @code{True}. This switch
18153 can be used in place of a definition file.
18157 @cindex @option{/REMOVE} (@command{gnatprep})
18158 This is the default setting which causes lines deleted by preprocessing
18159 to be entirely removed from the output file.
18162 @item ^-r^/REFERENCE^
18163 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18164 Causes a @code{Source_Reference} pragma to be generated that
18165 references the original input file, so that error messages will use
18166 the file name of this original file. The use of this switch implies
18167 that preprocessor lines are not to be removed from the file, so its
18168 use will force @option{^-b^/BLANK_LINES^} mode if
18169 @option{^-c^/COMMENTS^}
18170 has not been specified explicitly.
18172 Note that if the file to be preprocessed contains multiple units, then
18173 it will be necessary to @code{gnatchop} the output file from
18174 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18175 in the preprocessed file, it will be respected by
18176 @code{gnatchop ^-r^/REFERENCE^}
18177 so that the final chopped files will correctly refer to the original
18178 input source file for @code{gnatprep}.
18180 @item ^-s^/SYMBOLS^
18181 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18182 Causes a sorted list of symbol names and values to be
18183 listed on the standard output file.
18185 @item ^-u^/UNDEFINED^
18186 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18187 Causes undefined symbols to be treated as having the value FALSE in the context
18188 of a preprocessor test. In the absence of this option, an undefined symbol in
18189 a @code{#if} or @code{#elsif} test will be treated as an error.
18195 Note: if neither @option{-b} nor @option{-c} is present,
18196 then preprocessor lines and
18197 deleted lines are completely removed from the output, unless -r is
18198 specified, in which case -b is assumed.
18201 @node Form of Definitions File
18202 @section Form of Definitions File
18205 The definitions file contains lines of the form
18212 where symbol is a preprocessing symbol, and value is one of the following:
18216 Empty, corresponding to a null substitution
18218 A string literal using normal Ada syntax
18220 Any sequence of characters from the set
18221 (letters, digits, period, underline).
18225 Comment lines may also appear in the definitions file, starting with
18226 the usual @code{--},
18227 and comments may be added to the definitions lines.
18229 @node Form of Input Text for gnatprep
18230 @section Form of Input Text for @code{gnatprep}
18233 The input text may contain preprocessor conditional inclusion lines,
18234 as well as general symbol substitution sequences.
18236 The preprocessor conditional inclusion commands have the form
18241 #if @i{expression} @r{[}then@r{]}
18243 #elsif @i{expression} @r{[}then@r{]}
18245 #elsif @i{expression} @r{[}then@r{]}
18256 In this example, @i{expression} is defined by the following grammar:
18258 @i{expression} ::= <symbol>
18259 @i{expression} ::= <symbol> = "<value>"
18260 @i{expression} ::= <symbol> = <symbol>
18261 @i{expression} ::= <symbol> 'Defined
18262 @i{expression} ::= not @i{expression}
18263 @i{expression} ::= @i{expression} and @i{expression}
18264 @i{expression} ::= @i{expression} or @i{expression}
18265 @i{expression} ::= @i{expression} and then @i{expression}
18266 @i{expression} ::= @i{expression} or else @i{expression}
18267 @i{expression} ::= ( @i{expression} )
18270 The following restriction exists: it is not allowed to have "and" or "or"
18271 following "not" in the same expression without parentheses. For example, this
18278 This should be one of the following:
18286 For the first test (@i{expression} ::= <symbol>) the symbol must have
18287 either the value true or false, that is to say the right-hand of the
18288 symbol definition must be one of the (case-insensitive) literals
18289 @code{True} or @code{False}. If the value is true, then the
18290 corresponding lines are included, and if the value is false, they are
18293 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18294 the symbol has been defined in the definition file or by a @option{-D}
18295 switch on the command line. Otherwise, the test is false.
18297 The equality tests are case insensitive, as are all the preprocessor lines.
18299 If the symbol referenced is not defined in the symbol definitions file,
18300 then the effect depends on whether or not switch @option{-u}
18301 is specified. If so, then the symbol is treated as if it had the value
18302 false and the test fails. If this switch is not specified, then
18303 it is an error to reference an undefined symbol. It is also an error to
18304 reference a symbol that is defined with a value other than @code{True}
18307 The use of the @code{not} operator inverts the sense of this logical test.
18308 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18309 operators, without parentheses. For example, "if not X or Y then" is not
18310 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18312 The @code{then} keyword is optional as shown
18314 The @code{#} must be the first non-blank character on a line, but
18315 otherwise the format is free form. Spaces or tabs may appear between
18316 the @code{#} and the keyword. The keywords and the symbols are case
18317 insensitive as in normal Ada code. Comments may be used on a
18318 preprocessor line, but other than that, no other tokens may appear on a
18319 preprocessor line. Any number of @code{elsif} clauses can be present,
18320 including none at all. The @code{else} is optional, as in Ada.
18322 The @code{#} marking the start of a preprocessor line must be the first
18323 non-blank character on the line, i.e., it must be preceded only by
18324 spaces or horizontal tabs.
18326 Symbol substitution outside of preprocessor lines is obtained by using
18334 anywhere within a source line, except in a comment or within a
18335 string literal. The identifier
18336 following the @code{$} must match one of the symbols defined in the symbol
18337 definition file, and the result is to substitute the value of the
18338 symbol in place of @code{$symbol} in the output file.
18340 Note that although the substitution of strings within a string literal
18341 is not possible, it is possible to have a symbol whose defined value is
18342 a string literal. So instead of setting XYZ to @code{hello} and writing:
18345 Header : String := "$XYZ";
18349 you should set XYZ to @code{"hello"} and write:
18352 Header : String := $XYZ;
18356 and then the substitution will occur as desired.
18359 @node The GNAT Run-Time Library Builder gnatlbr
18360 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18362 @cindex Library builder
18365 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18366 supplied configuration pragmas.
18369 * Running gnatlbr::
18370 * Switches for gnatlbr::
18371 * Examples of gnatlbr Usage::
18374 @node Running gnatlbr
18375 @section Running @code{gnatlbr}
18378 The @code{gnatlbr} command has the form
18381 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18384 @node Switches for gnatlbr
18385 @section Switches for @code{gnatlbr}
18388 @code{gnatlbr} recognizes the following switches:
18392 @item /CREATE=directory
18393 @cindex @code{/CREATE} (@code{gnatlbr})
18394 Create the new run-time library in the specified directory.
18396 @item /SET=directory
18397 @cindex @code{/SET} (@code{gnatlbr})
18398 Make the library in the specified directory the current run-time library.
18400 @item /DELETE=directory
18401 @cindex @code{/DELETE} (@code{gnatlbr})
18402 Delete the run-time library in the specified directory.
18405 @cindex @code{/CONFIG} (@code{gnatlbr})
18406 With /CREATE: Use the configuration pragmas in the specified file when
18407 building the library.
18409 With /SET: Use the configuration pragmas in the specified file when
18414 @node Examples of gnatlbr Usage
18415 @section Example of @code{gnatlbr} Usage
18418 Contents of VAXFLOAT.ADC:
18419 pragma Float_Representation (VAX_Float);
18421 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18423 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18428 @node The GNAT Library Browser gnatls
18429 @chapter The GNAT Library Browser @code{gnatls}
18431 @cindex Library browser
18434 @code{gnatls} is a tool that outputs information about compiled
18435 units. It gives the relationship between objects, unit names and source
18436 files. It can also be used to check the source dependencies of a unit
18437 as well as various characteristics.
18439 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18440 driver (see @ref{The GNAT Driver and Project Files}).
18444 * Switches for gnatls::
18445 * Examples of gnatls Usage::
18448 @node Running gnatls
18449 @section Running @code{gnatls}
18452 The @code{gnatls} command has the form
18455 $ gnatls switches @var{object_or_ali_file}
18459 The main argument is the list of object or @file{ali} files
18460 (@pxref{The Ada Library Information Files})
18461 for which information is requested.
18463 In normal mode, without additional option, @code{gnatls} produces a
18464 four-column listing. Each line represents information for a specific
18465 object. The first column gives the full path of the object, the second
18466 column gives the name of the principal unit in this object, the third
18467 column gives the status of the source and the fourth column gives the
18468 full path of the source representing this unit.
18469 Here is a simple example of use:
18473 ^./^[]^demo1.o demo1 DIF demo1.adb
18474 ^./^[]^demo2.o demo2 OK demo2.adb
18475 ^./^[]^hello.o h1 OK hello.adb
18476 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18477 ^./^[]^instr.o instr OK instr.adb
18478 ^./^[]^tef.o tef DIF tef.adb
18479 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18480 ^./^[]^tgef.o tgef DIF tgef.adb
18484 The first line can be interpreted as follows: the main unit which is
18486 object file @file{demo1.o} is demo1, whose main source is in
18487 @file{demo1.adb}. Furthermore, the version of the source used for the
18488 compilation of demo1 has been modified (DIF). Each source file has a status
18489 qualifier which can be:
18492 @item OK (unchanged)
18493 The version of the source file used for the compilation of the
18494 specified unit corresponds exactly to the actual source file.
18496 @item MOK (slightly modified)
18497 The version of the source file used for the compilation of the
18498 specified unit differs from the actual source file but not enough to
18499 require recompilation. If you use gnatmake with the qualifier
18500 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18501 MOK will not be recompiled.
18503 @item DIF (modified)
18504 No version of the source found on the path corresponds to the source
18505 used to build this object.
18507 @item ??? (file not found)
18508 No source file was found for this unit.
18510 @item HID (hidden, unchanged version not first on PATH)
18511 The version of the source that corresponds exactly to the source used
18512 for compilation has been found on the path but it is hidden by another
18513 version of the same source that has been modified.
18517 @node Switches for gnatls
18518 @section Switches for @code{gnatls}
18521 @code{gnatls} recognizes the following switches:
18525 @cindex @option{--version} @command{gnatls}
18526 Display Copyright and version, then exit disregarding all other options.
18529 @cindex @option{--help} @command{gnatls}
18530 If @option{--version} was not used, display usage, then exit disregarding
18533 @item ^-a^/ALL_UNITS^
18534 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18535 Consider all units, including those of the predefined Ada library.
18536 Especially useful with @option{^-d^/DEPENDENCIES^}.
18538 @item ^-d^/DEPENDENCIES^
18539 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18540 List sources from which specified units depend on.
18542 @item ^-h^/OUTPUT=OPTIONS^
18543 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18544 Output the list of options.
18546 @item ^-o^/OUTPUT=OBJECTS^
18547 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18548 Only output information about object files.
18550 @item ^-s^/OUTPUT=SOURCES^
18551 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18552 Only output information about source files.
18554 @item ^-u^/OUTPUT=UNITS^
18555 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18556 Only output information about compilation units.
18558 @item ^-files^/FILES^=@var{file}
18559 @cindex @option{^-files^/FILES^} (@code{gnatls})
18560 Take as arguments the files listed in text file @var{file}.
18561 Text file @var{file} may contain empty lines that are ignored.
18562 Each nonempty line should contain the name of an existing file.
18563 Several such switches may be specified simultaneously.
18565 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18566 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18567 @itemx ^-I^/SEARCH=^@var{dir}
18568 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18570 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18571 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18572 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18573 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18574 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18575 flags (@pxref{Switches for gnatmake}).
18577 @item --RTS=@var{rts-path}
18578 @cindex @option{--RTS} (@code{gnatls})
18579 Specifies the default location of the runtime library. Same meaning as the
18580 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18582 @item ^-v^/OUTPUT=VERBOSE^
18583 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18584 Verbose mode. Output the complete source, object and project paths. Do not use
18585 the default column layout but instead use long format giving as much as
18586 information possible on each requested units, including special
18587 characteristics such as:
18590 @item Preelaborable
18591 The unit is preelaborable in the Ada sense.
18594 No elaboration code has been produced by the compiler for this unit.
18597 The unit is pure in the Ada sense.
18599 @item Elaborate_Body
18600 The unit contains a pragma Elaborate_Body.
18603 The unit contains a pragma Remote_Types.
18605 @item Shared_Passive
18606 The unit contains a pragma Shared_Passive.
18609 This unit is part of the predefined environment and cannot be modified
18612 @item Remote_Call_Interface
18613 The unit contains a pragma Remote_Call_Interface.
18619 @node Examples of gnatls Usage
18620 @section Example of @code{gnatls} Usage
18624 Example of using the verbose switch. Note how the source and
18625 object paths are affected by the -I switch.
18628 $ gnatls -v -I.. demo1.o
18630 GNATLS 5.03w (20041123-34)
18631 Copyright 1997-2004 Free Software Foundation, Inc.
18633 Source Search Path:
18634 <Current_Directory>
18636 /home/comar/local/adainclude/
18638 Object Search Path:
18639 <Current_Directory>
18641 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18643 Project Search Path:
18644 <Current_Directory>
18645 /home/comar/local/lib/gnat/
18650 Kind => subprogram body
18651 Flags => No_Elab_Code
18652 Source => demo1.adb modified
18656 The following is an example of use of the dependency list.
18657 Note the use of the -s switch
18658 which gives a straight list of source files. This can be useful for
18659 building specialized scripts.
18662 $ gnatls -d demo2.o
18663 ./demo2.o demo2 OK demo2.adb
18669 $ gnatls -d -s -a demo1.o
18671 /home/comar/local/adainclude/ada.ads
18672 /home/comar/local/adainclude/a-finali.ads
18673 /home/comar/local/adainclude/a-filico.ads
18674 /home/comar/local/adainclude/a-stream.ads
18675 /home/comar/local/adainclude/a-tags.ads
18678 /home/comar/local/adainclude/gnat.ads
18679 /home/comar/local/adainclude/g-io.ads
18681 /home/comar/local/adainclude/system.ads
18682 /home/comar/local/adainclude/s-exctab.ads
18683 /home/comar/local/adainclude/s-finimp.ads
18684 /home/comar/local/adainclude/s-finroo.ads
18685 /home/comar/local/adainclude/s-secsta.ads
18686 /home/comar/local/adainclude/s-stalib.ads
18687 /home/comar/local/adainclude/s-stoele.ads
18688 /home/comar/local/adainclude/s-stratt.ads
18689 /home/comar/local/adainclude/s-tasoli.ads
18690 /home/comar/local/adainclude/s-unstyp.ads
18691 /home/comar/local/adainclude/unchconv.ads
18697 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18699 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18700 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18701 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18702 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18703 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18707 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18708 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18710 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18711 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18712 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18713 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18714 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18715 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18716 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18717 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18718 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18719 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18720 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18724 @node Cleaning Up Using gnatclean
18725 @chapter Cleaning Up Using @code{gnatclean}
18727 @cindex Cleaning tool
18730 @code{gnatclean} is a tool that allows the deletion of files produced by the
18731 compiler, binder and linker, including ALI files, object files, tree files,
18732 expanded source files, library files, interface copy source files, binder
18733 generated files and executable files.
18736 * Running gnatclean::
18737 * Switches for gnatclean::
18738 @c * Examples of gnatclean Usage::
18741 @node Running gnatclean
18742 @section Running @code{gnatclean}
18745 The @code{gnatclean} command has the form:
18748 $ gnatclean switches @var{names}
18752 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18753 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18754 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18757 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18758 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18759 the linker. In informative-only mode, specified by switch
18760 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18761 normal mode is listed, but no file is actually deleted.
18763 @node Switches for gnatclean
18764 @section Switches for @code{gnatclean}
18767 @code{gnatclean} recognizes the following switches:
18771 @cindex @option{--version} @command{gnatclean}
18772 Display Copyright and version, then exit disregarding all other options.
18775 @cindex @option{--help} @command{gnatclean}
18776 If @option{--version} was not used, display usage, then exit disregarding
18779 @item ^-c^/COMPILER_FILES_ONLY^
18780 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18781 Only attempt to delete the files produced by the compiler, not those produced
18782 by the binder or the linker. The files that are not to be deleted are library
18783 files, interface copy files, binder generated files and executable files.
18785 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18786 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18787 Indicate that ALI and object files should normally be found in directory
18790 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18791 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18792 When using project files, if some errors or warnings are detected during
18793 parsing and verbose mode is not in effect (no use of switch
18794 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18795 file, rather than its simple file name.
18798 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18799 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18801 @item ^-n^/NODELETE^
18802 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18803 Informative-only mode. Do not delete any files. Output the list of the files
18804 that would have been deleted if this switch was not specified.
18806 @item ^-P^/PROJECT_FILE=^@var{project}
18807 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18808 Use project file @var{project}. Only one such switch can be used.
18809 When cleaning a project file, the files produced by the compilation of the
18810 immediate sources or inherited sources of the project files are to be
18811 deleted. This is not depending on the presence or not of executable names
18812 on the command line.
18815 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18816 Quiet output. If there are no errors, do not output anything, except in
18817 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18818 (switch ^-n^/NODELETE^).
18820 @item ^-r^/RECURSIVE^
18821 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18822 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18823 clean all imported and extended project files, recursively. If this switch
18824 is not specified, only the files related to the main project file are to be
18825 deleted. This switch has no effect if no project file is specified.
18827 @item ^-v^/VERBOSE^
18828 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18831 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18832 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18833 Indicates the verbosity of the parsing of GNAT project files.
18834 @xref{Switches Related to Project Files}.
18836 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18837 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18838 Indicates that external variable @var{name} has the value @var{value}.
18839 The Project Manager will use this value for occurrences of
18840 @code{external(name)} when parsing the project file.
18841 @xref{Switches Related to Project Files}.
18843 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18844 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18845 When searching for ALI and object files, look in directory
18848 @item ^-I^/SEARCH=^@var{dir}
18849 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18850 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18852 @item ^-I-^/NOCURRENT_DIRECTORY^
18853 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18854 @cindex Source files, suppressing search
18855 Do not look for ALI or object files in the directory
18856 where @code{gnatclean} was invoked.
18860 @c @node Examples of gnatclean Usage
18861 @c @section Examples of @code{gnatclean} Usage
18864 @node GNAT and Libraries
18865 @chapter GNAT and Libraries
18866 @cindex Library, building, installing, using
18869 This chapter describes how to build and use libraries with GNAT, and also shows
18870 how to recompile the GNAT run-time library. You should be familiar with the
18871 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18875 * Introduction to Libraries in GNAT::
18876 * General Ada Libraries::
18877 * Stand-alone Ada Libraries::
18878 * Rebuilding the GNAT Run-Time Library::
18881 @node Introduction to Libraries in GNAT
18882 @section Introduction to Libraries in GNAT
18885 A library is, conceptually, a collection of objects which does not have its
18886 own main thread of execution, but rather provides certain services to the
18887 applications that use it. A library can be either statically linked with the
18888 application, in which case its code is directly included in the application,
18889 or, on platforms that support it, be dynamically linked, in which case
18890 its code is shared by all applications making use of this library.
18892 GNAT supports both types of libraries.
18893 In the static case, the compiled code can be provided in different ways. The
18894 simplest approach is to provide directly the set of objects resulting from
18895 compilation of the library source files. Alternatively, you can group the
18896 objects into an archive using whatever commands are provided by the operating
18897 system. For the latter case, the objects are grouped into a shared library.
18899 In the GNAT environment, a library has three types of components:
18905 @xref{The Ada Library Information Files}.
18907 Object files, an archive or a shared library.
18911 A GNAT library may expose all its source files, which is useful for
18912 documentation purposes. Alternatively, it may expose only the units needed by
18913 an external user to make use of the library. That is to say, the specs
18914 reflecting the library services along with all the units needed to compile
18915 those specs, which can include generic bodies or any body implementing an
18916 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18917 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18919 All compilation units comprising an application, including those in a library,
18920 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18921 computes the elaboration order from the @file{ALI} files and this is why they
18922 constitute a mandatory part of GNAT libraries.
18923 @emph{Stand-alone libraries} are the exception to this rule because a specific
18924 library elaboration routine is produced independently of the application(s)
18927 @node General Ada Libraries
18928 @section General Ada Libraries
18931 * Building a library::
18932 * Installing a library::
18933 * Using a library::
18936 @node Building a library
18937 @subsection Building a library
18940 The easiest way to build a library is to use the Project Manager,
18941 which supports a special type of project called a @emph{Library Project}
18942 (@pxref{Library Projects}).
18944 A project is considered a library project, when two project-level attributes
18945 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18946 control different aspects of library configuration, additional optional
18947 project-level attributes can be specified:
18950 This attribute controls whether the library is to be static or dynamic
18952 @item Library_Version
18953 This attribute specifies the library version; this value is used
18954 during dynamic linking of shared libraries to determine if the currently
18955 installed versions of the binaries are compatible.
18957 @item Library_Options
18959 These attributes specify additional low-level options to be used during
18960 library generation, and redefine the actual application used to generate
18965 The GNAT Project Manager takes full care of the library maintenance task,
18966 including recompilation of the source files for which objects do not exist
18967 or are not up to date, assembly of the library archive, and installation of
18968 the library (i.e., copying associated source, object and @file{ALI} files
18969 to the specified location).
18971 Here is a simple library project file:
18972 @smallexample @c ada
18974 for Source_Dirs use ("src1", "src2");
18975 for Object_Dir use "obj";
18976 for Library_Name use "mylib";
18977 for Library_Dir use "lib";
18978 for Library_Kind use "dynamic";
18983 and the compilation command to build and install the library:
18985 @smallexample @c ada
18986 $ gnatmake -Pmy_lib
18990 It is not entirely trivial to perform manually all the steps required to
18991 produce a library. We recommend that you use the GNAT Project Manager
18992 for this task. In special cases where this is not desired, the necessary
18993 steps are discussed below.
18995 There are various possibilities for compiling the units that make up the
18996 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18997 with a conventional script. For simple libraries, it is also possible to create
18998 a dummy main program which depends upon all the packages that comprise the
18999 interface of the library. This dummy main program can then be given to
19000 @command{gnatmake}, which will ensure that all necessary objects are built.
19002 After this task is accomplished, you should follow the standard procedure
19003 of the underlying operating system to produce the static or shared library.
19005 Here is an example of such a dummy program:
19006 @smallexample @c ada
19008 with My_Lib.Service1;
19009 with My_Lib.Service2;
19010 with My_Lib.Service3;
19011 procedure My_Lib_Dummy is
19019 Here are the generic commands that will build an archive or a shared library.
19022 # compiling the library
19023 $ gnatmake -c my_lib_dummy.adb
19025 # we don't need the dummy object itself
19026 $ rm my_lib_dummy.o my_lib_dummy.ali
19028 # create an archive with the remaining objects
19029 $ ar rc libmy_lib.a *.o
19030 # some systems may require "ranlib" to be run as well
19032 # or create a shared library
19033 $ gcc -shared -o libmy_lib.so *.o
19034 # some systems may require the code to have been compiled with -fPIC
19036 # remove the object files that are now in the library
19039 # Make the ALI files read-only so that gnatmake will not try to
19040 # regenerate the objects that are in the library
19045 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19046 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19047 be accessed by the directive @option{-l@var{xxx}} at link time.
19049 @node Installing a library
19050 @subsection Installing a library
19051 @cindex @code{ADA_PROJECT_PATH}
19054 If you use project files, library installation is part of the library build
19055 process. Thus no further action is needed in order to make use of the
19056 libraries that are built as part of the general application build. A usable
19057 version of the library is installed in the directory specified by the
19058 @code{Library_Dir} attribute of the library project file.
19060 You may want to install a library in a context different from where the library
19061 is built. This situation arises with third party suppliers, who may want
19062 to distribute a library in binary form where the user is not expected to be
19063 able to recompile the library. The simplest option in this case is to provide
19064 a project file slightly different from the one used to build the library, by
19065 using the @code{externally_built} attribute. For instance, the project
19066 file used to build the library in the previous section can be changed into the
19067 following one when the library is installed:
19069 @smallexample @c projectfile
19071 for Source_Dirs use ("src1", "src2");
19072 for Library_Name use "mylib";
19073 for Library_Dir use "lib";
19074 for Library_Kind use "dynamic";
19075 for Externally_Built use "true";
19080 This project file assumes that the directories @file{src1},
19081 @file{src2}, and @file{lib} exist in
19082 the directory containing the project file. The @code{externally_built}
19083 attribute makes it clear to the GNAT builder that it should not attempt to
19084 recompile any of the units from this library. It allows the library provider to
19085 restrict the source set to the minimum necessary for clients to make use of the
19086 library as described in the first section of this chapter. It is the
19087 responsibility of the library provider to install the necessary sources, ALI
19088 files and libraries in the directories mentioned in the project file. For
19089 convenience, the user's library project file should be installed in a location
19090 that will be searched automatically by the GNAT
19091 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
19092 environment variable (@pxref{Importing Projects}), and also the default GNAT
19093 library location that can be queried with @command{gnatls -v} and is usually of
19094 the form $gnat_install_root/lib/gnat.
19096 When project files are not an option, it is also possible, but not recommended,
19097 to install the library so that the sources needed to use the library are on the
19098 Ada source path and the ALI files & libraries be on the Ada Object path (see
19099 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19100 administrator can place general-purpose libraries in the default compiler
19101 paths, by specifying the libraries' location in the configuration files
19102 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19103 must be located in the GNAT installation tree at the same place as the gcc spec
19104 file. The location of the gcc spec file can be determined as follows:
19110 The configuration files mentioned above have a simple format: each line
19111 must contain one unique directory name.
19112 Those names are added to the corresponding path
19113 in their order of appearance in the file. The names can be either absolute
19114 or relative; in the latter case, they are relative to where theses files
19117 The files @file{ada_source_path} and @file{ada_object_path} might not be
19119 GNAT installation, in which case, GNAT will look for its run-time library in
19120 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19121 objects and @file{ALI} files). When the files exist, the compiler does not
19122 look in @file{adainclude} and @file{adalib}, and thus the
19123 @file{ada_source_path} file
19124 must contain the location for the GNAT run-time sources (which can simply
19125 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19126 contain the location for the GNAT run-time objects (which can simply
19129 You can also specify a new default path to the run-time library at compilation
19130 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19131 the run-time library you want your program to be compiled with. This switch is
19132 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19133 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19135 It is possible to install a library before or after the standard GNAT
19136 library, by reordering the lines in the configuration files. In general, a
19137 library must be installed before the GNAT library if it redefines
19140 @node Using a library
19141 @subsection Using a library
19143 @noindent Once again, the project facility greatly simplifies the use of
19144 libraries. In this context, using a library is just a matter of adding a
19145 @code{with} clause in the user project. For instance, to make use of the
19146 library @code{My_Lib} shown in examples in earlier sections, you can
19149 @smallexample @c projectfile
19156 Even if you have a third-party, non-Ada library, you can still use GNAT's
19157 Project Manager facility to provide a wrapper for it. For example, the
19158 following project, when @code{with}ed by your main project, will link with the
19159 third-party library @file{liba.a}:
19161 @smallexample @c projectfile
19164 for Externally_Built use "true";
19165 for Source_Files use ();
19166 for Library_Dir use "lib";
19167 for Library_Name use "a";
19168 for Library_Kind use "static";
19172 This is an alternative to the use of @code{pragma Linker_Options}. It is
19173 especially interesting in the context of systems with several interdependent
19174 static libraries where finding a proper linker order is not easy and best be
19175 left to the tools having visibility over project dependence information.
19178 In order to use an Ada library manually, you need to make sure that this
19179 library is on both your source and object path
19180 (see @ref{Search Paths and the Run-Time Library (RTL)}
19181 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19182 in an archive or a shared library, you need to specify the desired
19183 library at link time.
19185 For example, you can use the library @file{mylib} installed in
19186 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19189 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19194 This can be expressed more simply:
19199 when the following conditions are met:
19202 @file{/dir/my_lib_src} has been added by the user to the environment
19203 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19204 @file{ada_source_path}
19206 @file{/dir/my_lib_obj} has been added by the user to the environment
19207 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19208 @file{ada_object_path}
19210 a pragma @code{Linker_Options} has been added to one of the sources.
19213 @smallexample @c ada
19214 pragma Linker_Options ("-lmy_lib");
19218 @node Stand-alone Ada Libraries
19219 @section Stand-alone Ada Libraries
19220 @cindex Stand-alone library, building, using
19223 * Introduction to Stand-alone Libraries::
19224 * Building a Stand-alone Library::
19225 * Creating a Stand-alone Library to be used in a non-Ada context::
19226 * Restrictions in Stand-alone Libraries::
19229 @node Introduction to Stand-alone Libraries
19230 @subsection Introduction to Stand-alone Libraries
19233 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19235 elaborate the Ada units that are included in the library. In contrast with
19236 an ordinary library, which consists of all sources, objects and @file{ALI}
19238 library, a SAL may specify a restricted subset of compilation units
19239 to serve as a library interface. In this case, the fully
19240 self-sufficient set of files will normally consist of an objects
19241 archive, the sources of interface units' specs, and the @file{ALI}
19242 files of interface units.
19243 If an interface spec contains a generic unit or an inlined subprogram,
19245 source must also be provided; if the units that must be provided in the source
19246 form depend on other units, the source and @file{ALI} files of those must
19249 The main purpose of a SAL is to minimize the recompilation overhead of client
19250 applications when a new version of the library is installed. Specifically,
19251 if the interface sources have not changed, client applications do not need to
19252 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19253 version, controlled by @code{Library_Version} attribute, is not changed,
19254 then the clients do not need to be relinked.
19256 SALs also allow the library providers to minimize the amount of library source
19257 text exposed to the clients. Such ``information hiding'' might be useful or
19258 necessary for various reasons.
19260 Stand-alone libraries are also well suited to be used in an executable whose
19261 main routine is not written in Ada.
19263 @node Building a Stand-alone Library
19264 @subsection Building a Stand-alone Library
19267 GNAT's Project facility provides a simple way of building and installing
19268 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19269 To be a Stand-alone Library Project, in addition to the two attributes
19270 that make a project a Library Project (@code{Library_Name} and
19271 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19272 @code{Library_Interface} must be defined. For example:
19274 @smallexample @c projectfile
19276 for Library_Dir use "lib_dir";
19277 for Library_Name use "dummy";
19278 for Library_Interface use ("int1", "int1.child");
19283 Attribute @code{Library_Interface} has a non-empty string list value,
19284 each string in the list designating a unit contained in an immediate source
19285 of the project file.
19287 When a Stand-alone Library is built, first the binder is invoked to build
19288 a package whose name depends on the library name
19289 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19290 This binder-generated package includes initialization and
19291 finalization procedures whose
19292 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19294 above). The object corresponding to this package is included in the library.
19296 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19297 calling of these procedures if a static SAL is built, or if a shared SAL
19299 with the project-level attribute @code{Library_Auto_Init} set to
19302 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19303 (those that are listed in attribute @code{Library_Interface}) are copied to
19304 the Library Directory. As a consequence, only the Interface Units may be
19305 imported from Ada units outside of the library. If other units are imported,
19306 the binding phase will fail.
19308 The attribute @code{Library_Src_Dir} may be specified for a
19309 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19310 single string value. Its value must be the path (absolute or relative to the
19311 project directory) of an existing directory. This directory cannot be the
19312 object directory or one of the source directories, but it can be the same as
19313 the library directory. The sources of the Interface
19314 Units of the library that are needed by an Ada client of the library will be
19315 copied to the designated directory, called the Interface Copy directory.
19316 These sources include the specs of the Interface Units, but they may also
19317 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19318 are used, or when there is a generic unit in the spec. Before the sources
19319 are copied to the Interface Copy directory, an attempt is made to delete all
19320 files in the Interface Copy directory.
19322 Building stand-alone libraries by hand is somewhat tedious, but for those
19323 occasions when it is necessary here are the steps that you need to perform:
19326 Compile all library sources.
19329 Invoke the binder with the switch @option{-n} (No Ada main program),
19330 with all the @file{ALI} files of the interfaces, and
19331 with the switch @option{-L} to give specific names to the @code{init}
19332 and @code{final} procedures. For example:
19334 gnatbind -n int1.ali int2.ali -Lsal1
19338 Compile the binder generated file:
19344 Link the dynamic library with all the necessary object files,
19345 indicating to the linker the names of the @code{init} (and possibly
19346 @code{final}) procedures for automatic initialization (and finalization).
19347 The built library should be placed in a directory different from
19348 the object directory.
19351 Copy the @code{ALI} files of the interface to the library directory,
19352 add in this copy an indication that it is an interface to a SAL
19353 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19354 with letter ``P'') and make the modified copy of the @file{ALI} file
19359 Using SALs is not different from using other libraries
19360 (see @ref{Using a library}).
19362 @node Creating a Stand-alone Library to be used in a non-Ada context
19363 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19366 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19369 The only extra step required is to ensure that library interface subprograms
19370 are compatible with the main program, by means of @code{pragma Export}
19371 or @code{pragma Convention}.
19373 Here is an example of simple library interface for use with C main program:
19375 @smallexample @c ada
19376 package Interface is
19378 procedure Do_Something;
19379 pragma Export (C, Do_Something, "do_something");
19381 procedure Do_Something_Else;
19382 pragma Export (C, Do_Something_Else, "do_something_else");
19388 On the foreign language side, you must provide a ``foreign'' view of the
19389 library interface; remember that it should contain elaboration routines in
19390 addition to interface subprograms.
19392 The example below shows the content of @code{mylib_interface.h} (note
19393 that there is no rule for the naming of this file, any name can be used)
19395 /* the library elaboration procedure */
19396 extern void mylibinit (void);
19398 /* the library finalization procedure */
19399 extern void mylibfinal (void);
19401 /* the interface exported by the library */
19402 extern void do_something (void);
19403 extern void do_something_else (void);
19407 Libraries built as explained above can be used from any program, provided
19408 that the elaboration procedures (named @code{mylibinit} in the previous
19409 example) are called before the library services are used. Any number of
19410 libraries can be used simultaneously, as long as the elaboration
19411 procedure of each library is called.
19413 Below is an example of a C program that uses the @code{mylib} library.
19416 #include "mylib_interface.h"
19421 /* First, elaborate the library before using it */
19424 /* Main program, using the library exported entities */
19426 do_something_else ();
19428 /* Library finalization at the end of the program */
19435 Note that invoking any library finalization procedure generated by
19436 @code{gnatbind} shuts down the Ada run-time environment.
19438 finalization of all Ada libraries must be performed at the end of the program.
19439 No call to these libraries or to the Ada run-time library should be made
19440 after the finalization phase.
19442 @node Restrictions in Stand-alone Libraries
19443 @subsection Restrictions in Stand-alone Libraries
19446 The pragmas listed below should be used with caution inside libraries,
19447 as they can create incompatibilities with other Ada libraries:
19449 @item pragma @code{Locking_Policy}
19450 @item pragma @code{Queuing_Policy}
19451 @item pragma @code{Task_Dispatching_Policy}
19452 @item pragma @code{Unreserve_All_Interrupts}
19456 When using a library that contains such pragmas, the user must make sure
19457 that all libraries use the same pragmas with the same values. Otherwise,
19458 @code{Program_Error} will
19459 be raised during the elaboration of the conflicting
19460 libraries. The usage of these pragmas and its consequences for the user
19461 should therefore be well documented.
19463 Similarly, the traceback in the exception occurrence mechanism should be
19464 enabled or disabled in a consistent manner across all libraries.
19465 Otherwise, Program_Error will be raised during the elaboration of the
19466 conflicting libraries.
19468 If the @code{Version} or @code{Body_Version}
19469 attributes are used inside a library, then you need to
19470 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19471 libraries, so that version identifiers can be properly computed.
19472 In practice these attributes are rarely used, so this is unlikely
19473 to be a consideration.
19475 @node Rebuilding the GNAT Run-Time Library
19476 @section Rebuilding the GNAT Run-Time Library
19477 @cindex GNAT Run-Time Library, rebuilding
19478 @cindex Building the GNAT Run-Time Library
19479 @cindex Rebuilding the GNAT Run-Time Library
19480 @cindex Run-Time Library, rebuilding
19483 It may be useful to recompile the GNAT library in various contexts, the
19484 most important one being the use of partition-wide configuration pragmas
19485 such as @code{Normalize_Scalars}. A special Makefile called
19486 @code{Makefile.adalib} is provided to that effect and can be found in
19487 the directory containing the GNAT library. The location of this
19488 directory depends on the way the GNAT environment has been installed and can
19489 be determined by means of the command:
19496 The last entry in the object search path usually contains the
19497 gnat library. This Makefile contains its own documentation and in
19498 particular the set of instructions needed to rebuild a new library and
19501 @node Using the GNU make Utility
19502 @chapter Using the GNU @code{make} Utility
19506 This chapter offers some examples of makefiles that solve specific
19507 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19508 make, make, GNU @code{make}}), nor does it try to replace the
19509 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19511 All the examples in this section are specific to the GNU version of
19512 make. Although @command{make} is a standard utility, and the basic language
19513 is the same, these examples use some advanced features found only in
19517 * Using gnatmake in a Makefile::
19518 * Automatically Creating a List of Directories::
19519 * Generating the Command Line Switches::
19520 * Overcoming Command Line Length Limits::
19523 @node Using gnatmake in a Makefile
19524 @section Using gnatmake in a Makefile
19529 Complex project organizations can be handled in a very powerful way by
19530 using GNU make combined with gnatmake. For instance, here is a Makefile
19531 which allows you to build each subsystem of a big project into a separate
19532 shared library. Such a makefile allows you to significantly reduce the link
19533 time of very big applications while maintaining full coherence at
19534 each step of the build process.
19536 The list of dependencies are handled automatically by
19537 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19538 the appropriate directories.
19540 Note that you should also read the example on how to automatically
19541 create the list of directories
19542 (@pxref{Automatically Creating a List of Directories})
19543 which might help you in case your project has a lot of subdirectories.
19548 @font@heightrm=cmr8
19551 ## This Makefile is intended to be used with the following directory
19553 ## - The sources are split into a series of csc (computer software components)
19554 ## Each of these csc is put in its own directory.
19555 ## Their name are referenced by the directory names.
19556 ## They will be compiled into shared library (although this would also work
19557 ## with static libraries
19558 ## - The main program (and possibly other packages that do not belong to any
19559 ## csc is put in the top level directory (where the Makefile is).
19560 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19561 ## \_ second_csc (sources) __ lib (will contain the library)
19563 ## Although this Makefile is build for shared library, it is easy to modify
19564 ## to build partial link objects instead (modify the lines with -shared and
19567 ## With this makefile, you can change any file in the system or add any new
19568 ## file, and everything will be recompiled correctly (only the relevant shared
19569 ## objects will be recompiled, and the main program will be re-linked).
19571 # The list of computer software component for your project. This might be
19572 # generated automatically.
19575 # Name of the main program (no extension)
19578 # If we need to build objects with -fPIC, uncomment the following line
19581 # The following variable should give the directory containing libgnat.so
19582 # You can get this directory through 'gnatls -v'. This is usually the last
19583 # directory in the Object_Path.
19586 # The directories for the libraries
19587 # (This macro expands the list of CSC to the list of shared libraries, you
19588 # could simply use the expanded form:
19589 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19590 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19592 $@{MAIN@}: objects $@{LIB_DIR@}
19593 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19594 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19597 # recompile the sources
19598 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19600 # Note: In a future version of GNAT, the following commands will be simplified
19601 # by a new tool, gnatmlib
19603 mkdir -p $@{dir $@@ @}
19604 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19605 cd $@{dir $@@ @} && cp -f ../*.ali .
19607 # The dependencies for the modules
19608 # Note that we have to force the expansion of *.o, since in some cases
19609 # make won't be able to do it itself.
19610 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19611 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19612 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19614 # Make sure all of the shared libraries are in the path before starting the
19617 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19620 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19621 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19622 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19623 $@{RM@} *.o *.ali $@{MAIN@}
19626 @node Automatically Creating a List of Directories
19627 @section Automatically Creating a List of Directories
19630 In most makefiles, you will have to specify a list of directories, and
19631 store it in a variable. For small projects, it is often easier to
19632 specify each of them by hand, since you then have full control over what
19633 is the proper order for these directories, which ones should be
19636 However, in larger projects, which might involve hundreds of
19637 subdirectories, it might be more convenient to generate this list
19640 The example below presents two methods. The first one, although less
19641 general, gives you more control over the list. It involves wildcard
19642 characters, that are automatically expanded by @command{make}. Its
19643 shortcoming is that you need to explicitly specify some of the
19644 organization of your project, such as for instance the directory tree
19645 depth, whether some directories are found in a separate tree, @enddots{}
19647 The second method is the most general one. It requires an external
19648 program, called @command{find}, which is standard on all Unix systems. All
19649 the directories found under a given root directory will be added to the
19655 @font@heightrm=cmr8
19658 # The examples below are based on the following directory hierarchy:
19659 # All the directories can contain any number of files
19660 # ROOT_DIRECTORY -> a -> aa -> aaa
19663 # -> b -> ba -> baa
19666 # This Makefile creates a variable called DIRS, that can be reused any time
19667 # you need this list (see the other examples in this section)
19669 # The root of your project's directory hierarchy
19673 # First method: specify explicitly the list of directories
19674 # This allows you to specify any subset of all the directories you need.
19677 DIRS := a/aa/ a/ab/ b/ba/
19680 # Second method: use wildcards
19681 # Note that the argument(s) to wildcard below should end with a '/'.
19682 # Since wildcards also return file names, we have to filter them out
19683 # to avoid duplicate directory names.
19684 # We thus use make's @code{dir} and @code{sort} functions.
19685 # It sets DIRs to the following value (note that the directories aaa and baa
19686 # are not given, unless you change the arguments to wildcard).
19687 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19690 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19691 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19694 # Third method: use an external program
19695 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19696 # This is the most complete command: it sets DIRs to the following value:
19697 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19700 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19704 @node Generating the Command Line Switches
19705 @section Generating the Command Line Switches
19708 Once you have created the list of directories as explained in the
19709 previous section (@pxref{Automatically Creating a List of Directories}),
19710 you can easily generate the command line arguments to pass to gnatmake.
19712 For the sake of completeness, this example assumes that the source path
19713 is not the same as the object path, and that you have two separate lists
19717 # see "Automatically creating a list of directories" to create
19722 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19723 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19726 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19729 @node Overcoming Command Line Length Limits
19730 @section Overcoming Command Line Length Limits
19733 One problem that might be encountered on big projects is that many
19734 operating systems limit the length of the command line. It is thus hard to give
19735 gnatmake the list of source and object directories.
19737 This example shows how you can set up environment variables, which will
19738 make @command{gnatmake} behave exactly as if the directories had been
19739 specified on the command line, but have a much higher length limit (or
19740 even none on most systems).
19742 It assumes that you have created a list of directories in your Makefile,
19743 using one of the methods presented in
19744 @ref{Automatically Creating a List of Directories}.
19745 For the sake of completeness, we assume that the object
19746 path (where the ALI files are found) is different from the sources patch.
19748 Note a small trick in the Makefile below: for efficiency reasons, we
19749 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19750 expanded immediately by @code{make}. This way we overcome the standard
19751 make behavior which is to expand the variables only when they are
19754 On Windows, if you are using the standard Windows command shell, you must
19755 replace colons with semicolons in the assignments to these variables.
19760 @font@heightrm=cmr8
19763 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19764 # This is the same thing as putting the -I arguments on the command line.
19765 # (the equivalent of using -aI on the command line would be to define
19766 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19767 # You can of course have different values for these variables.
19769 # Note also that we need to keep the previous values of these variables, since
19770 # they might have been set before running 'make' to specify where the GNAT
19771 # library is installed.
19773 # see "Automatically creating a list of directories" to create these
19779 space:=$@{empty@} $@{empty@}
19780 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19781 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19782 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19783 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19784 export ADA_INCLUDE_PATH
19785 export ADA_OBJECT_PATH
19792 @node Memory Management Issues
19793 @chapter Memory Management Issues
19796 This chapter describes some useful memory pools provided in the GNAT library
19797 and in particular the GNAT Debug Pool facility, which can be used to detect
19798 incorrect uses of access values (including ``dangling references'').
19800 It also describes the @command{gnatmem} tool, which can be used to track down
19805 * Some Useful Memory Pools::
19806 * The GNAT Debug Pool Facility::
19808 * The gnatmem Tool::
19812 @node Some Useful Memory Pools
19813 @section Some Useful Memory Pools
19814 @findex Memory Pool
19815 @cindex storage, pool
19818 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19819 storage pool. Allocations use the standard system call @code{malloc} while
19820 deallocations use the standard system call @code{free}. No reclamation is
19821 performed when the pool goes out of scope. For performance reasons, the
19822 standard default Ada allocators/deallocators do not use any explicit storage
19823 pools but if they did, they could use this storage pool without any change in
19824 behavior. That is why this storage pool is used when the user
19825 manages to make the default implicit allocator explicit as in this example:
19826 @smallexample @c ada
19827 type T1 is access Something;
19828 -- no Storage pool is defined for T2
19829 type T2 is access Something_Else;
19830 for T2'Storage_Pool use T1'Storage_Pool;
19831 -- the above is equivalent to
19832 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19836 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19837 pool. The allocation strategy is similar to @code{Pool_Local}'s
19838 except that the all
19839 storage allocated with this pool is reclaimed when the pool object goes out of
19840 scope. This pool provides a explicit mechanism similar to the implicit one
19841 provided by several Ada 83 compilers for allocations performed through a local
19842 access type and whose purpose was to reclaim memory when exiting the
19843 scope of a given local access. As an example, the following program does not
19844 leak memory even though it does not perform explicit deallocation:
19846 @smallexample @c ada
19847 with System.Pool_Local;
19848 procedure Pooloc1 is
19849 procedure Internal is
19850 type A is access Integer;
19851 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19852 for A'Storage_Pool use X;
19855 for I in 1 .. 50 loop
19860 for I in 1 .. 100 loop
19867 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19868 @code{Storage_Size} is specified for an access type.
19869 The whole storage for the pool is
19870 allocated at once, usually on the stack at the point where the access type is
19871 elaborated. It is automatically reclaimed when exiting the scope where the
19872 access type is defined. This package is not intended to be used directly by the
19873 user and it is implicitly used for each such declaration:
19875 @smallexample @c ada
19876 type T1 is access Something;
19877 for T1'Storage_Size use 10_000;
19880 @node The GNAT Debug Pool Facility
19881 @section The GNAT Debug Pool Facility
19883 @cindex storage, pool, memory corruption
19886 The use of unchecked deallocation and unchecked conversion can easily
19887 lead to incorrect memory references. The problems generated by such
19888 references are usually difficult to tackle because the symptoms can be
19889 very remote from the origin of the problem. In such cases, it is
19890 very helpful to detect the problem as early as possible. This is the
19891 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19893 In order to use the GNAT specific debugging pool, the user must
19894 associate a debug pool object with each of the access types that may be
19895 related to suspected memory problems. See Ada Reference Manual 13.11.
19896 @smallexample @c ada
19897 type Ptr is access Some_Type;
19898 Pool : GNAT.Debug_Pools.Debug_Pool;
19899 for Ptr'Storage_Pool use Pool;
19903 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19904 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19905 allow the user to redefine allocation and deallocation strategies. They
19906 also provide a checkpoint for each dereference, through the use of
19907 the primitive operation @code{Dereference} which is implicitly called at
19908 each dereference of an access value.
19910 Once an access type has been associated with a debug pool, operations on
19911 values of the type may raise four distinct exceptions,
19912 which correspond to four potential kinds of memory corruption:
19915 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19917 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19919 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19921 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19925 For types associated with a Debug_Pool, dynamic allocation is performed using
19926 the standard GNAT allocation routine. References to all allocated chunks of
19927 memory are kept in an internal dictionary. Several deallocation strategies are
19928 provided, whereupon the user can choose to release the memory to the system,
19929 keep it allocated for further invalid access checks, or fill it with an easily
19930 recognizable pattern for debug sessions. The memory pattern is the old IBM
19931 hexadecimal convention: @code{16#DEADBEEF#}.
19933 See the documentation in the file g-debpoo.ads for more information on the
19934 various strategies.
19936 Upon each dereference, a check is made that the access value denotes a
19937 properly allocated memory location. Here is a complete example of use of
19938 @code{Debug_Pools}, that includes typical instances of memory corruption:
19939 @smallexample @c ada
19943 with Gnat.Io; use Gnat.Io;
19944 with Unchecked_Deallocation;
19945 with Unchecked_Conversion;
19946 with GNAT.Debug_Pools;
19947 with System.Storage_Elements;
19948 with Ada.Exceptions; use Ada.Exceptions;
19949 procedure Debug_Pool_Test is
19951 type T is access Integer;
19952 type U is access all T;
19954 P : GNAT.Debug_Pools.Debug_Pool;
19955 for T'Storage_Pool use P;
19957 procedure Free is new Unchecked_Deallocation (Integer, T);
19958 function UC is new Unchecked_Conversion (U, T);
19961 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19971 Put_Line (Integer'Image(B.all));
19973 when E : others => Put_Line ("raised: " & Exception_Name (E));
19978 when E : others => Put_Line ("raised: " & Exception_Name (E));
19982 Put_Line (Integer'Image(B.all));
19984 when E : others => Put_Line ("raised: " & Exception_Name (E));
19989 when E : others => Put_Line ("raised: " & Exception_Name (E));
19992 end Debug_Pool_Test;
19996 The debug pool mechanism provides the following precise diagnostics on the
19997 execution of this erroneous program:
20000 Total allocated bytes : 0
20001 Total deallocated bytes : 0
20002 Current Water Mark: 0
20006 Total allocated bytes : 8
20007 Total deallocated bytes : 0
20008 Current Water Mark: 8
20011 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
20012 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
20013 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
20014 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20016 Total allocated bytes : 8
20017 Total deallocated bytes : 4
20018 Current Water Mark: 4
20023 @node The gnatmem Tool
20024 @section The @command{gnatmem} Tool
20028 The @code{gnatmem} utility monitors dynamic allocation and
20029 deallocation activity in a program, and displays information about
20030 incorrect deallocations and possible sources of memory leaks.
20031 It is designed to work in association with a static runtime library
20032 only and in this context provides three types of information:
20035 General information concerning memory management, such as the total
20036 number of allocations and deallocations, the amount of allocated
20037 memory and the high water mark, i.e.@: the largest amount of allocated
20038 memory in the course of program execution.
20041 Backtraces for all incorrect deallocations, that is to say deallocations
20042 which do not correspond to a valid allocation.
20045 Information on each allocation that is potentially the origin of a memory
20050 * Running gnatmem::
20051 * Switches for gnatmem::
20052 * Example of gnatmem Usage::
20055 @node Running gnatmem
20056 @subsection Running @code{gnatmem}
20059 @code{gnatmem} makes use of the output created by the special version of
20060 allocation and deallocation routines that record call information. This
20061 allows to obtain accurate dynamic memory usage history at a minimal cost to
20062 the execution speed. Note however, that @code{gnatmem} is not supported on
20063 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20064 Solaris and Windows NT/2000/XP (x86).
20067 The @code{gnatmem} command has the form
20070 $ gnatmem @ovar{switches} user_program
20074 The program must have been linked with the instrumented version of the
20075 allocation and deallocation routines. This is done by linking with the
20076 @file{libgmem.a} library. For correct symbolic backtrace information,
20077 the user program should be compiled with debugging options
20078 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20081 $ gnatmake -g my_program -largs -lgmem
20085 As library @file{libgmem.a} contains an alternate body for package
20086 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20087 when an executable is linked with library @file{libgmem.a}. It is then not
20088 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20091 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20092 This file contains information about all allocations and deallocations
20093 performed by the program. It is produced by the instrumented allocations and
20094 deallocations routines and will be used by @code{gnatmem}.
20096 In order to produce symbolic backtrace information for allocations and
20097 deallocations performed by the GNAT run-time library, you need to use a
20098 version of that library that has been compiled with the @option{-g} switch
20099 (see @ref{Rebuilding the GNAT Run-Time Library}).
20101 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20102 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20103 @option{-i} switch, gnatmem will assume that this file can be found in the
20104 current directory. For example, after you have executed @file{my_program},
20105 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20108 $ gnatmem my_program
20112 This will produce the output with the following format:
20114 *************** debut cc
20116 $ gnatmem my_program
20120 Total number of allocations : 45
20121 Total number of deallocations : 6
20122 Final Water Mark (non freed mem) : 11.29 Kilobytes
20123 High Water Mark : 11.40 Kilobytes
20128 Allocation Root # 2
20129 -------------------
20130 Number of non freed allocations : 11
20131 Final Water Mark (non freed mem) : 1.16 Kilobytes
20132 High Water Mark : 1.27 Kilobytes
20134 my_program.adb:23 my_program.alloc
20140 The first block of output gives general information. In this case, the
20141 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20142 Unchecked_Deallocation routine occurred.
20145 Subsequent paragraphs display information on all allocation roots.
20146 An allocation root is a specific point in the execution of the program
20147 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20148 construct. This root is represented by an execution backtrace (or subprogram
20149 call stack). By default the backtrace depth for allocations roots is 1, so
20150 that a root corresponds exactly to a source location. The backtrace can
20151 be made deeper, to make the root more specific.
20153 @node Switches for gnatmem
20154 @subsection Switches for @code{gnatmem}
20157 @code{gnatmem} recognizes the following switches:
20162 @cindex @option{-q} (@code{gnatmem})
20163 Quiet. Gives the minimum output needed to identify the origin of the
20164 memory leaks. Omits statistical information.
20167 @cindex @var{N} (@code{gnatmem})
20168 N is an integer literal (usually between 1 and 10) which controls the
20169 depth of the backtraces defining allocation root. The default value for
20170 N is 1. The deeper the backtrace, the more precise the localization of
20171 the root. Note that the total number of roots can depend on this
20172 parameter. This parameter must be specified @emph{before} the name of the
20173 executable to be analyzed, to avoid ambiguity.
20176 @cindex @option{-b} (@code{gnatmem})
20177 This switch has the same effect as just depth parameter.
20179 @item -i @var{file}
20180 @cindex @option{-i} (@code{gnatmem})
20181 Do the @code{gnatmem} processing starting from @file{file}, rather than
20182 @file{gmem.out} in the current directory.
20185 @cindex @option{-m} (@code{gnatmem})
20186 This switch causes @code{gnatmem} to mask the allocation roots that have less
20187 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20188 examine even the roots that didn't result in leaks.
20191 @cindex @option{-s} (@code{gnatmem})
20192 This switch causes @code{gnatmem} to sort the allocation roots according to the
20193 specified order of sort criteria, each identified by a single letter. The
20194 currently supported criteria are @code{n, h, w} standing respectively for
20195 number of unfreed allocations, high watermark, and final watermark
20196 corresponding to a specific root. The default order is @code{nwh}.
20200 @node Example of gnatmem Usage
20201 @subsection Example of @code{gnatmem} Usage
20204 The following example shows the use of @code{gnatmem}
20205 on a simple memory-leaking program.
20206 Suppose that we have the following Ada program:
20208 @smallexample @c ada
20211 with Unchecked_Deallocation;
20212 procedure Test_Gm is
20214 type T is array (1..1000) of Integer;
20215 type Ptr is access T;
20216 procedure Free is new Unchecked_Deallocation (T, Ptr);
20219 procedure My_Alloc is
20224 procedure My_DeAlloc is
20232 for I in 1 .. 5 loop
20233 for J in I .. 5 loop
20244 The program needs to be compiled with debugging option and linked with
20245 @code{gmem} library:
20248 $ gnatmake -g test_gm -largs -lgmem
20252 Then we execute the program as usual:
20259 Then @code{gnatmem} is invoked simply with
20265 which produces the following output (result may vary on different platforms):
20270 Total number of allocations : 18
20271 Total number of deallocations : 5
20272 Final Water Mark (non freed mem) : 53.00 Kilobytes
20273 High Water Mark : 56.90 Kilobytes
20275 Allocation Root # 1
20276 -------------------
20277 Number of non freed allocations : 11
20278 Final Water Mark (non freed mem) : 42.97 Kilobytes
20279 High Water Mark : 46.88 Kilobytes
20281 test_gm.adb:11 test_gm.my_alloc
20283 Allocation Root # 2
20284 -------------------
20285 Number of non freed allocations : 1
20286 Final Water Mark (non freed mem) : 10.02 Kilobytes
20287 High Water Mark : 10.02 Kilobytes
20289 s-secsta.adb:81 system.secondary_stack.ss_init
20291 Allocation Root # 3
20292 -------------------
20293 Number of non freed allocations : 1
20294 Final Water Mark (non freed mem) : 12 Bytes
20295 High Water Mark : 12 Bytes
20297 s-secsta.adb:181 system.secondary_stack.ss_init
20301 Note that the GNAT run time contains itself a certain number of
20302 allocations that have no corresponding deallocation,
20303 as shown here for root #2 and root
20304 #3. This is a normal behavior when the number of non-freed allocations
20305 is one, it allocates dynamic data structures that the run time needs for
20306 the complete lifetime of the program. Note also that there is only one
20307 allocation root in the user program with a single line back trace:
20308 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20309 program shows that 'My_Alloc' is called at 2 different points in the
20310 source (line 21 and line 24). If those two allocation roots need to be
20311 distinguished, the backtrace depth parameter can be used:
20314 $ gnatmem 3 test_gm
20318 which will give the following output:
20323 Total number of allocations : 18
20324 Total number of deallocations : 5
20325 Final Water Mark (non freed mem) : 53.00 Kilobytes
20326 High Water Mark : 56.90 Kilobytes
20328 Allocation Root # 1
20329 -------------------
20330 Number of non freed allocations : 10
20331 Final Water Mark (non freed mem) : 39.06 Kilobytes
20332 High Water Mark : 42.97 Kilobytes
20334 test_gm.adb:11 test_gm.my_alloc
20335 test_gm.adb:24 test_gm
20336 b_test_gm.c:52 main
20338 Allocation Root # 2
20339 -------------------
20340 Number of non freed allocations : 1
20341 Final Water Mark (non freed mem) : 10.02 Kilobytes
20342 High Water Mark : 10.02 Kilobytes
20344 s-secsta.adb:81 system.secondary_stack.ss_init
20345 s-secsta.adb:283 <system__secondary_stack___elabb>
20346 b_test_gm.c:33 adainit
20348 Allocation Root # 3
20349 -------------------
20350 Number of non freed allocations : 1
20351 Final Water Mark (non freed mem) : 3.91 Kilobytes
20352 High Water Mark : 3.91 Kilobytes
20354 test_gm.adb:11 test_gm.my_alloc
20355 test_gm.adb:21 test_gm
20356 b_test_gm.c:52 main
20358 Allocation Root # 4
20359 -------------------
20360 Number of non freed allocations : 1
20361 Final Water Mark (non freed mem) : 12 Bytes
20362 High Water Mark : 12 Bytes
20364 s-secsta.adb:181 system.secondary_stack.ss_init
20365 s-secsta.adb:283 <system__secondary_stack___elabb>
20366 b_test_gm.c:33 adainit
20370 The allocation root #1 of the first example has been split in 2 roots #1
20371 and #3 thanks to the more precise associated backtrace.
20375 @node Stack Related Facilities
20376 @chapter Stack Related Facilities
20379 This chapter describes some useful tools associated with stack
20380 checking and analysis. In
20381 particular, it deals with dynamic and static stack usage measurements.
20384 * Stack Overflow Checking::
20385 * Static Stack Usage Analysis::
20386 * Dynamic Stack Usage Analysis::
20389 @node Stack Overflow Checking
20390 @section Stack Overflow Checking
20391 @cindex Stack Overflow Checking
20392 @cindex -fstack-check
20395 For most operating systems, @command{gcc} does not perform stack overflow
20396 checking by default. This means that if the main environment task or
20397 some other task exceeds the available stack space, then unpredictable
20398 behavior will occur. Most native systems offer some level of protection by
20399 adding a guard page at the end of each task stack. This mechanism is usually
20400 not enough for dealing properly with stack overflow situations because
20401 a large local variable could ``jump'' above the guard page.
20402 Furthermore, when the
20403 guard page is hit, there may not be any space left on the stack for executing
20404 the exception propagation code. Enabling stack checking avoids
20407 To activate stack checking, compile all units with the gcc option
20408 @option{-fstack-check}. For example:
20411 gcc -c -fstack-check package1.adb
20415 Units compiled with this option will generate extra instructions to check
20416 that any use of the stack (for procedure calls or for declaring local
20417 variables in declare blocks) does not exceed the available stack space.
20418 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20420 For declared tasks, the stack size is controlled by the size
20421 given in an applicable @code{Storage_Size} pragma or by the value specified
20422 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20423 the default size as defined in the GNAT runtime otherwise.
20425 For the environment task, the stack size depends on
20426 system defaults and is unknown to the compiler. Stack checking
20427 may still work correctly if a fixed
20428 size stack is allocated, but this cannot be guaranteed.
20430 To ensure that a clean exception is signalled for stack
20431 overflow, set the environment variable
20432 @env{GNAT_STACK_LIMIT} to indicate the maximum
20433 stack area that can be used, as in:
20434 @cindex GNAT_STACK_LIMIT
20437 SET GNAT_STACK_LIMIT 1600
20441 The limit is given in kilobytes, so the above declaration would
20442 set the stack limit of the environment task to 1.6 megabytes.
20443 Note that the only purpose of this usage is to limit the amount
20444 of stack used by the environment task. If it is necessary to
20445 increase the amount of stack for the environment task, then this
20446 is an operating systems issue, and must be addressed with the
20447 appropriate operating systems commands.
20450 To have a fixed size stack in the environment task, the stack must be put
20451 in the P0 address space and its size specified. Use these switches to
20455 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20459 The quotes are required to keep case. The number after @samp{STACK=} is the
20460 size of the environmental task stack in pagelets (512 bytes). In this example
20461 the stack size is about 2 megabytes.
20464 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20465 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20466 more details about the @option{/p0image} qualifier and the @option{stack}
20470 @node Static Stack Usage Analysis
20471 @section Static Stack Usage Analysis
20472 @cindex Static Stack Usage Analysis
20473 @cindex -fstack-usage
20476 A unit compiled with @option{-fstack-usage} will generate an extra file
20478 the maximum amount of stack used, on a per-function basis.
20479 The file has the same
20480 basename as the target object file with a @file{.su} extension.
20481 Each line of this file is made up of three fields:
20485 The name of the function.
20489 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20492 The second field corresponds to the size of the known part of the function
20495 The qualifier @code{static} means that the function frame size
20497 It usually means that all local variables have a static size.
20498 In this case, the second field is a reliable measure of the function stack
20501 The qualifier @code{dynamic} means that the function frame size is not static.
20502 It happens mainly when some local variables have a dynamic size. When this
20503 qualifier appears alone, the second field is not a reliable measure
20504 of the function stack analysis. When it is qualified with @code{bounded}, it
20505 means that the second field is a reliable maximum of the function stack
20508 @node Dynamic Stack Usage Analysis
20509 @section Dynamic Stack Usage Analysis
20512 It is possible to measure the maximum amount of stack used by a task, by
20513 adding a switch to @command{gnatbind}, as:
20516 $ gnatbind -u0 file
20520 With this option, at each task termination, its stack usage is output on
20522 It is not always convenient to output the stack usage when the program
20523 is still running. Hence, it is possible to delay this output until program
20524 termination. for a given number of tasks specified as the argument of the
20525 @option{-u} option. For instance:
20528 $ gnatbind -u100 file
20532 will buffer the stack usage information of the first 100 tasks to terminate and
20533 output this info at program termination. Results are displayed in four
20537 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20544 is a number associated with each task.
20547 is the name of the task analyzed.
20550 is the maximum size for the stack.
20553 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20554 is not entirely analyzed, and it's not possible to know exactly how
20555 much has actually been used. The report thus contains the theoretical stack usage
20556 (Value) and the possible variation (Variation) around this value.
20561 The environment task stack, e.g., the stack that contains the main unit, is
20562 only processed when the environment variable GNAT_STACK_LIMIT is set.
20565 @c *********************************
20567 @c *********************************
20568 @node Verifying Properties Using gnatcheck
20569 @chapter Verifying Properties Using @command{gnatcheck}
20571 @cindex @command{gnatcheck}
20574 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20575 of Ada source files according to a given set of semantic rules.
20578 In order to check compliance with a given rule, @command{gnatcheck} has to
20579 semantically analyze the Ada sources.
20580 Therefore, checks can only be performed on
20581 legal Ada units. Moreover, when a unit depends semantically upon units located
20582 outside the current directory, the source search path has to be provided when
20583 calling @command{gnatcheck}, either through a specified project file or
20584 through @command{gnatcheck} switches as described below.
20586 A number of rules are predefined in @command{gnatcheck} and are described
20587 later in this chapter.
20588 You can also add new rules, by modifying the @command{gnatcheck} code and
20589 rebuilding the tool. In order to add a simple rule making some local checks,
20590 a small amount of straightforward ASIS-based programming is usually needed.
20592 Project support for @command{gnatcheck} is provided by the GNAT
20593 driver (see @ref{The GNAT Driver and Project Files}).
20595 Invoking @command{gnatcheck} on the command line has the form:
20598 $ gnatcheck @ovar{switches} @{@var{filename}@}
20599 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20600 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20607 @var{switches} specify the general tool options
20610 Each @var{filename} is the name (including the extension) of a source
20611 file to process. ``Wildcards'' are allowed, and
20612 the file name may contain path information.
20615 Each @var{arg_list_filename} is the name (including the extension) of a text
20616 file containing the names of the source files to process, separated by spaces
20620 @var{gcc_switches} is a list of switches for
20621 @command{gcc}. They will be passed on to all compiler invocations made by
20622 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20623 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20624 and use the @option{-gnatec} switch to set the configuration file.
20627 @var{rule_options} is a list of options for controlling a set of
20628 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20632 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20635 * Format of the Report File::
20636 * General gnatcheck Switches::
20637 * gnatcheck Rule Options::
20638 * Adding the Results of Compiler Checks to gnatcheck Output::
20639 * Project-Wide Checks::
20640 * Predefined Rules::
20643 @node Format of the Report File
20644 @section Format of the Report File
20645 @cindex Report file (for @code{gnatcheck})
20648 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20650 It also creates a text file that
20651 contains the complete report of the last gnatcheck run. By default this file is
20652 named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the current
20653 directory, @option{^-o^/OUTPUT^} option can be used to change the name and/or
20654 location of the report file. This report contains:
20656 @item a list of the Ada source files being checked,
20657 @item a list of enabled and disabled rules,
20658 @item a list of the diagnostic messages, ordered in three different ways
20659 and collected in three separate
20660 sections. Section 1 contains the raw list of diagnostic messages. It
20661 corresponds to the output going to @file{stdout}. Section 2 contains
20662 messages ordered by rules.
20663 Section 3 contains messages ordered by source files.
20666 @node General gnatcheck Switches
20667 @section General @command{gnatcheck} Switches
20670 The following switches control the general @command{gnatcheck} behavior
20674 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20676 Process all units including those with read-only ALI files such as
20677 those from GNAT Run-Time library.
20681 @cindex @option{-d} (@command{gnatcheck})
20686 @cindex @option{-dd} (@command{gnatcheck})
20688 Progress indicator mode (for use in GPS)
20691 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20693 List the predefined and user-defined rules. For more details see
20694 @ref{Predefined Rules}.
20696 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20698 Use full source locations references in the report file. For a construct from
20699 a generic instantiation a full source location is a chain from the location
20700 of this construct in the generic unit to the place where this unit is
20703 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20705 Duplicate all the output sent to Stderr into a log file. The log file is
20706 named @var{gnatcheck.log} and is located in the current directory.
20708 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20709 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20710 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20711 the default value is 500. Zero means that there is no limitation on
20712 the number of diagnostic messages to be printed into Stdout.
20714 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20716 Quiet mode. All the diagnoses about rule violations are placed in the
20717 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20719 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20721 Short format of the report file (no version information, no list of applied
20722 rules, no list of checked sources is included)
20724 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20725 @item ^-s1^/COMPILER_STYLE^
20726 Include the compiler-style section in the report file
20728 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20729 @item ^-s2^/BY_RULES^
20730 Include the section containing diagnoses ordered by rules in the report file
20732 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20733 @item ^-s3^/BY_FILES_BY_RULES^
20734 Include the section containing diagnoses ordered by files and then by rules
20737 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20739 Print out execution time.
20741 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20742 @item ^-v^/VERBOSE^
20743 Verbose mode; @command{gnatcheck} generates version information and then
20744 a trace of sources being processed.
20746 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20747 @item ^-o ^/OUTPUT=^@var{report_file}
20748 Set name of report file file to @var{report_file} .
20753 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20754 @option{^-s2^/BY_RULES^} or
20755 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20756 then the @command{gnatcheck} report file will only contain sections
20757 explicitly denoted by these options.
20759 @node gnatcheck Rule Options
20760 @section @command{gnatcheck} Rule Options
20763 The following options control the processing performed by
20764 @command{gnatcheck}.
20767 @cindex @option{+ALL} (@command{gnatcheck})
20769 Turn all the rule checks ON.
20771 @cindex @option{-ALL} (@command{gnatcheck})
20773 Turn all the rule checks OFF.
20775 @cindex @option{+R} (@command{gnatcheck})
20776 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20777 Turn on the check for a specified rule with the specified parameter, if any.
20778 @var{rule_id} must be the identifier of one of the currently implemented rules
20779 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20780 are not case-sensitive. The @var{param} item must
20781 be a string representing a valid parameter(s) for the specified rule.
20782 If it contains any space characters then this string must be enclosed in
20785 @cindex @option{-R} (@command{gnatcheck})
20786 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20787 Turn off the check for a specified rule with the specified parameter, if any.
20789 @cindex @option{-from} (@command{gnatcheck})
20790 @item -from=@var{rule_option_filename}
20791 Read the rule options from the text file @var{rule_option_filename}, referred as
20792 ``rule file'' below.
20797 The default behavior is that all the rule checks are disabled.
20799 A rule file is a text file containing a set of rule options.
20800 @cindex Rule file (for @code{gnatcheck})
20801 The file may contain empty lines and Ada-style comments (comment
20802 lines and end-of-line comments). The rule file has free format; that is,
20803 you do not have to start a new rule option on a new line.
20805 A rule file may contain other @option{-from=@var{rule_option_filename}}
20806 options, each such option being replaced with the content of the
20807 corresponding rule file during the rule files processing. In case a
20808 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20809 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20810 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20811 the processing of rule files is interrupted and a part of their content
20815 @node Adding the Results of Compiler Checks to gnatcheck Output
20816 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20819 The @command{gnatcheck} tool can include in the generated diagnostic messages
20821 the report file the results of the checks performed by the compiler. Though
20822 disabled by default, this effect may be obtained by using @option{+R} with
20823 the following rule identifiers and parameters:
20827 To record restrictions violations (that are performed by the compiler if the
20828 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20830 @code{Restrictions} with the same parameters as pragma
20831 @code{Restrictions} or @code{Restriction_Warnings}.
20834 To record compiler style checks(@pxref{Style Checking}), use the rule named
20835 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20836 which enables all the standard style checks that corresponds to @option{-gnatyy}
20837 GNAT style check option, or a string that has exactly the same
20838 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20839 @code{Style_Checks} (for further information about this pragma,
20840 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}). For example,
20841 @code{+RStyle_Checks:O} rule option activates and adds to @command{gnatcheck}
20842 output the compiler style check that corresponds to
20843 @code{-gnatyO} style check option.
20846 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20847 named @code{Warnings} with a parameter that is a valid
20848 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20849 (for further information about this pragma, @pxref{Pragma Warnings,,,
20850 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20851 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20852 all the specific warnings, but not suppresses the warning mode,
20853 and 'e' parameter, corresponding to @option{-gnatwe} that means
20854 "treat warnings as errors", does not have any effect.
20858 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20859 option with the corresponding restriction name as a parameter. @code{-R} is
20860 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20861 warnings and style checks, use the corresponding warning and style options.
20863 @node Project-Wide Checks
20864 @section Project-Wide Checks
20865 @cindex Project-wide checks (for @command{gnatcheck})
20868 In order to perform checks on all units of a given project, you can use
20869 the GNAT driver along with the @option{-P} option:
20871 gnat check -Pproj -rules -from=my_rules
20875 If the project @code{proj} depends upon other projects, you can perform
20876 checks on the project closure using the @option{-U} option:
20878 gnat check -Pproj -U -rules -from=my_rules
20882 Finally, if not all the units are relevant to a particular main
20883 program in the project closure, you can perform checks for the set
20884 of units needed to create a given main program (unit closure) using
20885 the @option{-U} option followed by the name of the main unit:
20887 gnat check -Pproj -U main -rules -from=my_rules
20891 @node Predefined Rules
20892 @section Predefined Rules
20893 @cindex Predefined rules (for @command{gnatcheck})
20896 @c (Jan 2007) Since the global rules are still under development and are not
20897 @c documented, there is no point in explaining the difference between
20898 @c global and local rules
20900 A rule in @command{gnatcheck} is either local or global.
20901 A @emph{local rule} is a rule that applies to a well-defined section
20902 of a program and that can be checked by analyzing only this section.
20903 A @emph{global rule} requires analysis of some global properties of the
20904 whole program (mostly related to the program call graph).
20905 As of @value{NOW}, the implementation of global rules should be
20906 considered to be at a preliminary stage. You can use the
20907 @option{+GLOBAL} option to enable all the global rules, and the
20908 @option{-GLOBAL} rule option to disable all the global rules.
20910 All the global rules in the list below are
20911 so indicated by marking them ``GLOBAL''.
20912 This +GLOBAL and -GLOBAL options are not
20913 included in the list of gnatcheck options above, because at the moment they
20914 are considered as a temporary debug options.
20916 @command{gnatcheck} performs rule checks for generic
20917 instances only for global rules. This limitation may be relaxed in a later
20922 The following subsections document the rules implemented in
20923 @command{gnatcheck}.
20924 The subsection title is the same as the rule identifier, which may be
20925 used as a parameter of the @option{+R} or @option{-R} options.
20929 * Abstract_Type_Declarations::
20930 * Anonymous_Arrays::
20931 * Anonymous_Subtypes::
20933 * Boolean_Relational_Operators::
20935 * Ceiling_Violations::
20937 * Controlled_Type_Declarations::
20938 * Declarations_In_Blocks::
20939 * Default_Parameters::
20940 * Discriminated_Records::
20941 * Enumeration_Ranges_In_CASE_Statements::
20942 * Exceptions_As_Control_Flow::
20943 * Exits_From_Conditional_Loops::
20944 * EXIT_Statements_With_No_Loop_Name::
20945 * Expanded_Loop_Exit_Names::
20946 * Explicit_Full_Discrete_Ranges::
20947 * Float_Equality_Checks::
20948 * Forbidden_Pragmas::
20949 * Function_Style_Procedures::
20950 * Generics_In_Subprograms::
20951 * GOTO_Statements::
20952 * Implicit_IN_Mode_Parameters::
20953 * Implicit_SMALL_For_Fixed_Point_Types::
20954 * Improperly_Located_Instantiations::
20955 * Improper_Returns::
20956 * Library_Level_Subprograms::
20959 * Improperly_Called_Protected_Entries::
20962 * Misnamed_Identifiers::
20963 * Multiple_Entries_In_Protected_Definitions::
20965 * Non_Qualified_Aggregates::
20966 * Non_Short_Circuit_Operators::
20967 * Non_SPARK_Attributes::
20968 * Non_Tagged_Derived_Types::
20969 * Non_Visible_Exceptions::
20970 * Numeric_Literals::
20971 * OTHERS_In_Aggregates::
20972 * OTHERS_In_CASE_Statements::
20973 * OTHERS_In_Exception_Handlers::
20974 * Outer_Loop_Exits::
20975 * Overloaded_Operators::
20976 * Overly_Nested_Control_Structures::
20977 * Parameters_Out_Of_Order::
20978 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20979 * Positional_Actuals_For_Defaulted_Parameters::
20980 * Positional_Components::
20981 * Positional_Generic_Parameters::
20982 * Positional_Parameters::
20983 * Predefined_Numeric_Types::
20984 * Raising_External_Exceptions::
20985 * Raising_Predefined_Exceptions::
20986 * Separate_Numeric_Error_Handlers::
20989 * Side_Effect_Functions::
20992 * Unassigned_OUT_Parameters::
20993 * Uncommented_BEGIN_In_Package_Bodies::
20994 * Unconditional_Exits::
20995 * Unconstrained_Array_Returns::
20996 * Universal_Ranges::
20997 * Unnamed_Blocks_And_Loops::
20999 * Unused_Subprograms::
21001 * USE_PACKAGE_Clauses::
21002 * Volatile_Objects_Without_Address_Clauses::
21006 @node Abstract_Type_Declarations
21007 @subsection @code{Abstract_Type_Declarations}
21008 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
21011 Flag all declarations of abstract types. For an abstract private
21012 type, both the private and full type declarations are flagged.
21014 This rule has no parameters.
21017 @node Anonymous_Arrays
21018 @subsection @code{Anonymous_Arrays}
21019 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21022 Flag all anonymous array type definitions (by Ada semantics these can only
21023 occur in object declarations).
21025 This rule has no parameters.
21027 @node Anonymous_Subtypes
21028 @subsection @code{Anonymous_Subtypes}
21029 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21032 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
21033 any instance of a subtype indication with a constraint, other than one
21034 that occurs immediately within a subtype declaration. Any use of a range
21035 other than as a constraint used immediately within a subtype declaration
21036 is considered as an anonymous subtype.
21038 An effect of this rule is that @code{for} loops such as the following are
21039 flagged (since @code{1..N} is formally a ``range''):
21041 @smallexample @c ada
21042 for I in 1 .. N loop
21048 Declaring an explicit subtype solves the problem:
21050 @smallexample @c ada
21051 subtype S is Integer range 1..N;
21059 This rule has no parameters.
21062 @subsection @code{Blocks}
21063 @cindex @code{Blocks} rule (for @command{gnatcheck})
21066 Flag each block statement.
21068 This rule has no parameters.
21070 @node Boolean_Relational_Operators
21071 @subsection @code{Boolean_Relational_Operators}
21072 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21075 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21076 ``>='', ``='' and ``/='') for the predefined Boolean type.
21077 (This rule is useful in enforcing the SPARK language restrictions.)
21079 Calls to predefined relational operators of any type derived from
21080 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21081 with these designators, and uses of operators that are renamings
21082 of the predefined relational operators for @code{Standard.Boolean},
21083 are likewise not detected.
21085 This rule has no parameters.
21088 @node Ceiling_Violations
21089 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
21090 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21093 Flag invocations of a protected operation by a task whose priority exceeds
21094 the protected object's ceiling.
21096 As of @value{NOW}, this rule has the following limitations:
21101 We consider only pragmas Priority and Interrupt_Priority as means to define
21102 a task/protected operation priority. We do not consider the effect of using
21103 Ada.Dynamic_Priorities.Set_Priority procedure;
21106 We consider only base task priorities, and no priority inheritance. That is,
21107 we do not make a difference between calls issued during task activation and
21108 execution of the sequence of statements from task body;
21111 Any situation when the priority of protected operation caller is set by a
21112 dynamic expression (that is, the corresponding Priority or
21113 Interrupt_Priority pragma has a non-static expression as an argument) we
21114 treat as a priority inconsistency (and, therefore, detect this situation).
21118 At the moment the notion of the main subprogram is not implemented in
21119 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21120 if this subprogram can be a main subprogram of a partition) changes the
21121 priority of an environment task. So if we have more then one such pragma in
21122 the set of processed sources, the pragma that is processed last, defines the
21123 priority of an environment task.
21125 This rule has no parameters.
21128 @node Controlled_Type_Declarations
21129 @subsection @code{Controlled_Type_Declarations}
21130 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21133 Flag all declarations of controlled types. A declaration of a private type
21134 is flagged if its full declaration declares a controlled type. A declaration
21135 of a derived type is flagged if its ancestor type is controlled. Subtype
21136 declarations are not checked. A declaration of a type that itself is not a
21137 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21138 component is not checked.
21140 This rule has no parameters.
21144 @node Declarations_In_Blocks
21145 @subsection @code{Declarations_In_Blocks}
21146 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21149 Flag all block statements containing local declarations. A @code{declare}
21150 block with an empty @i{declarative_part} or with a @i{declarative part}
21151 containing only pragmas and/or @code{use} clauses is not flagged.
21153 This rule has no parameters.
21156 @node Default_Parameters
21157 @subsection @code{Default_Parameters}
21158 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21161 Flag all default expressions for subprogram parameters. Parameter
21162 declarations of formal and generic subprograms are also checked.
21164 This rule has no parameters.
21167 @node Discriminated_Records
21168 @subsection @code{Discriminated_Records}
21169 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21172 Flag all declarations of record types with discriminants. Only the
21173 declarations of record and record extension types are checked. Incomplete,
21174 formal, private, derived and private extension type declarations are not
21175 checked. Task and protected type declarations also are not checked.
21177 This rule has no parameters.
21180 @node Enumeration_Ranges_In_CASE_Statements
21181 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21182 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21185 Flag each use of a range of enumeration literals as a choice in a
21186 @code{case} statement.
21187 All forms for specifying a range (explicit ranges
21188 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21189 An enumeration range is
21190 flagged even if contains exactly one enumeration value or no values at all. A
21191 type derived from an enumeration type is considered as an enumeration type.
21193 This rule helps prevent maintenance problems arising from adding an
21194 enumeration value to a type and having it implicitly handled by an existing
21195 @code{case} statement with an enumeration range that includes the new literal.
21197 This rule has no parameters.
21200 @node Exceptions_As_Control_Flow
21201 @subsection @code{Exceptions_As_Control_Flow}
21202 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21205 Flag each place where an exception is explicitly raised and handled in the
21206 same subprogram body. A @code{raise} statement in an exception handler,
21207 package body, task body or entry body is not flagged.
21209 The rule has no parameters.
21211 @node Exits_From_Conditional_Loops
21212 @subsection @code{Exits_From_Conditional_Loops}
21213 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21216 Flag any exit statement if it transfers the control out of a @code{for} loop
21217 or a @code{while} loop. This includes cases when the @code{exit} statement
21218 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21219 in some @code{for} or @code{while} loop, but transfers the control from some
21220 outer (inconditional) @code{loop} statement.
21222 The rule has no parameters.
21225 @node EXIT_Statements_With_No_Loop_Name
21226 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21227 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21230 Flag each @code{exit} statement that does not specify the name of the loop
21233 The rule has no parameters.
21236 @node Expanded_Loop_Exit_Names
21237 @subsection @code{Expanded_Loop_Exit_Names}
21238 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21241 Flag all expanded loop names in @code{exit} statements.
21243 This rule has no parameters.
21245 @node Explicit_Full_Discrete_Ranges
21246 @subsection @code{Explicit_Full_Discrete_Ranges}
21247 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21250 Flag each discrete range that has the form @code{A'First .. A'Last}.
21252 This rule has no parameters.
21254 @node Float_Equality_Checks
21255 @subsection @code{Float_Equality_Checks}
21256 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21259 Flag all calls to the predefined equality operations for floating-point types.
21260 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21261 User-defined equality operations are not flagged, nor are ``@code{=}''
21262 and ``@code{/=}'' operations for fixed-point types.
21264 This rule has no parameters.
21267 @node Forbidden_Pragmas
21268 @subsection @code{Forbidden_Pragmas}
21269 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21272 Flag each use of the specified pragmas. The pragmas to be detected
21273 are named in the rule's parameters.
21275 This rule has the following parameters:
21278 @item For the @option{+R} option
21281 @item @emph{Pragma_Name}
21282 Adds the specified pragma to the set of pragmas to be
21283 checked and sets the checks for all the specified pragmas
21284 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21285 does not correspond to any pragma name defined in the Ada
21286 standard or to the name of a GNAT-specific pragma defined
21287 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21288 Manual}, it is treated as the name of unknown pragma.
21291 All the GNAT-specific pragmas are detected; this sets
21292 the checks for all the specified pragmas ON.
21295 All pragmas are detected; this sets the rule ON.
21298 @item For the @option{-R} option
21300 @item @emph{Pragma_Name}
21301 Removes the specified pragma from the set of pragmas to be
21302 checked without affecting checks for
21303 other pragmas. @emph{Pragma_Name} is treated as a name
21304 of a pragma. If it does not correspond to any pragma
21305 defined in the Ada standard or to any name defined in
21306 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21307 this option is treated as turning OFF detection of all unknown pragmas.
21310 Turn OFF detection of all GNAT-specific pragmas
21313 Clear the list of the pragmas to be detected and
21319 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21320 the syntax of an Ada identifier and therefore can not be considered
21321 as a pragma name, a diagnostic message is generated and the corresponding
21322 parameter is ignored.
21324 When more then one parameter is given in the same rule option, the parameters
21325 must be separated by a comma.
21327 If more then one option for this rule is specified for the @command{gnatcheck}
21328 call, a new option overrides the previous one(s).
21330 The @option{+R} option with no parameters turns the rule ON with the set of
21331 pragmas to be detected defined by the previous rule options.
21332 (By default this set is empty, so if the only option specified for the rule is
21333 @option{+RForbidden_Pragmas} (with
21334 no parameter), then the rule is enabled, but it does not detect anything).
21335 The @option{-R} option with no parameter turns the rule OFF, but it does not
21336 affect the set of pragmas to be detected.
21341 @node Function_Style_Procedures
21342 @subsection @code{Function_Style_Procedures}
21343 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21346 Flag each procedure that can be rewritten as a function. A procedure can be
21347 converted into a function if it has exactly one parameter of mode @code{out}
21348 and no parameters of mode @code{in out}. Procedure declarations,
21349 formal procedure declarations, and generic procedure declarations are always
21351 bodies and body stubs are flagged only if they do not have corresponding
21352 separate declarations. Procedure renamings and procedure instantiations are
21355 If a procedure can be rewritten as a function, but its @code{out} parameter is
21356 of a limited type, it is not flagged.
21358 Protected procedures are not flagged. Null procedures also are not flagged.
21360 This rule has no parameters.
21363 @node Generics_In_Subprograms
21364 @subsection @code{Generics_In_Subprograms}
21365 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21368 Flag each declaration of a generic unit in a subprogram. Generic
21369 declarations in the bodies of generic subprograms are also flagged.
21370 A generic unit nested in another generic unit is not flagged.
21371 If a generic unit is
21372 declared in a local package that is declared in a subprogram body, the
21373 generic unit is flagged.
21375 This rule has no parameters.
21378 @node GOTO_Statements
21379 @subsection @code{GOTO_Statements}
21380 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21383 Flag each occurrence of a @code{goto} statement.
21385 This rule has no parameters.
21388 @node Implicit_IN_Mode_Parameters
21389 @subsection @code{Implicit_IN_Mode_Parameters}
21390 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21393 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21394 Note that @code{access} parameters, although they technically behave
21395 like @code{in} parameters, are not flagged.
21397 This rule has no parameters.
21400 @node Implicit_SMALL_For_Fixed_Point_Types
21401 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21402 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21405 Flag each fixed point type declaration that lacks an explicit
21406 representation clause to define its @code{'Small} value.
21407 Since @code{'Small} can be defined only for ordinary fixed point types,
21408 decimal fixed point type declarations are not checked.
21410 This rule has no parameters.
21413 @node Improperly_Located_Instantiations
21414 @subsection @code{Improperly_Located_Instantiations}
21415 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21418 Flag all generic instantiations in library-level package specs
21419 (including library generic packages) and in all subprogram bodies.
21421 Instantiations in task and entry bodies are not flagged. Instantiations in the
21422 bodies of protected subprograms are flagged.
21424 This rule has no parameters.
21428 @node Improper_Returns
21429 @subsection @code{Improper_Returns}
21430 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21433 Flag each explicit @code{return} statement in procedures, and
21434 multiple @code{return} statements in functions.
21435 Diagnostic messages are generated for all @code{return} statements
21436 in a procedure (thus each procedure must be written so that it
21437 returns implicitly at the end of its statement part),
21438 and for all @code{return} statements in a function after the first one.
21439 This rule supports the stylistic convention that each subprogram
21440 should have no more than one point of normal return.
21442 This rule has no parameters.
21445 @node Library_Level_Subprograms
21446 @subsection @code{Library_Level_Subprograms}
21447 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21450 Flag all library-level subprograms (including generic subprogram instantiations).
21452 This rule has no parameters.
21455 @node Local_Packages
21456 @subsection @code{Local_Packages}
21457 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21460 Flag all local packages declared in package and generic package
21462 Local packages in bodies are not flagged.
21464 This rule has no parameters.
21467 @node Improperly_Called_Protected_Entries
21468 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21469 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21472 Flag each protected entry that can be called from more than one task.
21474 This rule has no parameters.
21478 @subsection @code{Metrics}
21479 @cindex @code{Metrics} rule (for @command{gnatcheck})
21482 There is a set of checks based on computing a metric value and comparing the
21483 result with the specified upper (or lower, depending on a specific metric)
21484 value specified for a given metric. A construct is flagged if a given metric
21485 is applicable (can be computed) for it and the computed value is greater
21486 then (lover then) the specified upper (lower) bound.
21488 The name of any metric-based rule consists of the prefix @code{Metrics_}
21489 followed by the name of the corresponding metric (see the table below).
21490 For @option{+R} option, each metric-based rule has a numeric parameter
21491 specifying the bound (integer or real, depending on a metric), @option{-R}
21492 option for metric rules does not have a parameter.
21494 The following table shows the metric names for that the corresponding
21495 metrics-based checks are supported by gnatcheck, including the
21496 constraint that must be satisfied by the bound that is specified for the check
21497 and what bound - upper (U) or lower (L) - should be specified.
21499 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21501 @headitem Check Name @tab Description @tab Bounds Value
21504 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21506 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21507 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21508 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21509 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21513 The meaning and the computed values for all these metrics are exactly
21514 the same as for the corresponding metrics in @command{gnatmetric}.
21516 @emph{Example:} the rule
21518 +RMetrics_Cyclomatic_Complexity : 7
21521 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21523 To turn OFF the check for cyclomatic complexity metric, use the following option:
21525 -RMetrics_Cyclomatic_Complexity
21528 @node Misnamed_Identifiers
21529 @subsection @code{Misnamed_Identifiers}
21530 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21533 Flag the declaration of each identifier that does not have a suffix
21534 corresponding to the kind of entity being declared.
21535 The following declarations are checked:
21542 subtype declarations
21545 constant declarations (but not number declarations)
21548 package renaming declarations (but not generic package renaming
21553 This rule may have parameters. When used without parameters, the rule enforces
21554 the following checks:
21558 type-defining names end with @code{_T}, unless the type is an access type,
21559 in which case the suffix must be @code{_A}
21561 constant names end with @code{_C}
21563 names defining package renamings end with @code{_R}
21567 For a private or incomplete type declaration the following checks are
21568 made for the defining name suffix:
21572 For an incomplete type declaration: if the corresponding full type
21573 declaration is available, the defining identifier from the full type
21574 declaration is checked, but the defining identifier from the incomplete type
21575 declaration is not; otherwise the defining identifier from the incomplete
21576 type declaration is checked against the suffix specified for type
21580 For a private type declaration (including private extensions), the defining
21581 identifier from the private type declaration is checked against the type
21582 suffix (even if the corresponding full declaration is an access type
21583 declaration), and the defining identifier from the corresponding full type
21584 declaration is not checked.
21588 For a deferred constant, the defining name in the corresponding full constant
21589 declaration is not checked.
21591 Defining names of formal types are not checked.
21593 The rule may have the following parameters:
21597 For the @option{+R} option:
21600 Sets the default listed above for all the names to be checked.
21602 @item Type_Suffix=@emph{string}
21603 Specifies the suffix for a type name.
21605 @item Access_Suffix=@emph{string}
21606 Specifies the suffix for an access type name. If
21607 this parameter is set, it overrides for access
21608 types the suffix set by the @code{Type_Suffix} parameter.
21609 For access types, @emph{string} may have the following format:
21610 @emph{suffix1(suffix2)}. That means that an access type name
21611 should have the @emph{suffix1} suffix except for the case when
21612 the designated type is also an access type, in this case the
21613 type name should have the @emph{suffix1 & suffix2} suffix.
21615 @item Class_Access_Suffix=@emph{string}
21616 Specifies the suffix for the name of an access type that points to some class-wide
21617 type. If this parameter is set, it overrides for such access
21618 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
21621 @item Class_Subtype_Suffix=@emph{string}
21622 Specifies the suffix for the name of a subtype that denotes a class-wide type.
21624 @item Constant_Suffix=@emph{string}
21625 Specifies the suffix for a constant name.
21627 @item Renaming_Suffix=@emph{string}
21628 Specifies the suffix for a package renaming name.
21632 For the @option{-R} option:
21635 Remove all the suffixes specified for the
21636 identifier suffix checks, whether by default or
21637 as specified by other rule parameters. All the
21638 checks for this rule are disabled as a result.
21641 Removes the suffix specified for types. This
21642 disables checks for types but does not disable
21643 any other checks for this rule (including the
21644 check for access type names if @code{Access_Suffix} is
21647 @item Access_Suffix
21648 Removes the suffix specified for access types.
21649 This disables checks for access type names but
21650 does not disable any other checks for this rule.
21651 If @code{Type_Suffix} is set, access type names are
21652 checked as ordinary type names.
21654 @item Class_Access_Suffix
21655 Removes the suffix specified for access types pointing to class-wide
21656 type. This disables specific checks for names of access types pointing to
21657 class-wide types but does not disable any other checks for this rule.
21658 If @code{Type_Suffix} is set, access type names are
21659 checked as ordinary type names. If @code{Access_Suffix} is set, these
21660 access types are checked as any other access type name.
21662 @item Class_Subtype_Suffix=@emph{string}
21663 Removes the suffix specified for subtype names.
21664 This disables checks for subtype names but
21665 does not disable any other checks for this rule.
21667 @item Constant_Suffix
21668 Removes the suffix specified for constants. This
21669 disables checks for constant names but does not
21670 disable any other checks for this rule.
21672 @item Renaming_Suffix
21673 Removes the suffix specified for package
21674 renamings. This disables checks for package
21675 renamings but does not disable any other checks
21681 If more than one parameter is used, parameters must be separated by commas.
21683 If more than one option is specified for the @command{gnatcheck} invocation,
21684 a new option overrides the previous one(s).
21686 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21688 name suffixes specified by previous options used for this rule.
21690 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21691 all the checks but keeps
21692 all the suffixes specified by previous options used for this rule.
21694 The @emph{string} value must be a valid suffix for an Ada identifier (after
21695 trimming all the leading and trailing space characters, if any).
21696 Parameters are not case sensitive, except the @emph{string} part.
21698 If any error is detected in a rule parameter, the parameter is ignored.
21699 In such a case the options that are set for the rule are not
21704 @node Multiple_Entries_In_Protected_Definitions
21705 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21706 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21709 Flag each protected definition (i.e., each protected object/type declaration)
21710 that defines more than one entry.
21711 Diagnostic messages are generated for all the entry declarations
21712 except the first one. An entry family is counted as one entry. Entries from
21713 the private part of the protected definition are also checked.
21715 This rule has no parameters.
21718 @subsection @code{Name_Clashes}
21719 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21722 Check that certain names are not used as defining identifiers. To activate
21723 this rule, you need to supply a reference to the dictionary file(s) as a rule
21724 parameter(s) (more then one dictionary file can be specified). If no
21725 dictionary file is set, this rule will not cause anything to be flagged.
21726 Only defining occurrences, not references, are checked.
21727 The check is not case-sensitive.
21729 This rule is enabled by default, but without setting any corresponding
21730 dictionary file(s); thus the default effect is to do no checks.
21732 A dictionary file is a plain text file. The maximum line length for this file
21733 is 1024 characters. If the line is longer then this limit, extra characters
21736 Each line can be either an empty line, a comment line, or a line containing
21737 a list of identifiers separated by space or HT characters.
21738 A comment is an Ada-style comment (from @code{--} to end-of-line).
21739 Identifiers must follow the Ada syntax for identifiers.
21740 A line containing one or more identifiers may end with a comment.
21742 @node Non_Qualified_Aggregates
21743 @subsection @code{Non_Qualified_Aggregates}
21744 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21747 Flag each non-qualified aggregate.
21748 A non-qualified aggregate is an
21749 aggregate that is not the expression of a qualified expression. A
21750 string literal is not considered an aggregate, but an array
21751 aggregate of a string type is considered as a normal aggregate.
21752 Aggregates of anonymous array types are not flagged.
21754 This rule has no parameters.
21757 @node Non_Short_Circuit_Operators
21758 @subsection @code{Non_Short_Circuit_Operators}
21759 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21762 Flag all calls to predefined @code{and} and @code{or} operators for
21763 any boolean type. Calls to
21764 user-defined @code{and} and @code{or} and to operators defined by renaming
21765 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21766 operators for modular types or boolean array types are not flagged.
21768 This rule has no parameters.
21772 @node Non_SPARK_Attributes
21773 @subsection @code{Non_SPARK_Attributes}
21774 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21777 The SPARK language defines the following subset of Ada 95 attribute
21778 designators as those that can be used in SPARK programs. The use of
21779 any other attribute is flagged.
21782 @item @code{'Adjacent}
21785 @item @code{'Ceiling}
21786 @item @code{'Component_Size}
21787 @item @code{'Compose}
21788 @item @code{'Copy_Sign}
21789 @item @code{'Delta}
21790 @item @code{'Denorm}
21791 @item @code{'Digits}
21792 @item @code{'Exponent}
21793 @item @code{'First}
21794 @item @code{'Floor}
21796 @item @code{'Fraction}
21798 @item @code{'Leading_Part}
21799 @item @code{'Length}
21800 @item @code{'Machine}
21801 @item @code{'Machine_Emax}
21802 @item @code{'Machine_Emin}
21803 @item @code{'Machine_Mantissa}
21804 @item @code{'Machine_Overflows}
21805 @item @code{'Machine_Radix}
21806 @item @code{'Machine_Rounds}
21809 @item @code{'Model}
21810 @item @code{'Model_Emin}
21811 @item @code{'Model_Epsilon}
21812 @item @code{'Model_Mantissa}
21813 @item @code{'Model_Small}
21814 @item @code{'Modulus}
21817 @item @code{'Range}
21818 @item @code{'Remainder}
21819 @item @code{'Rounding}
21820 @item @code{'Safe_First}
21821 @item @code{'Safe_Last}
21822 @item @code{'Scaling}
21823 @item @code{'Signed_Zeros}
21825 @item @code{'Small}
21827 @item @code{'Truncation}
21828 @item @code{'Unbiased_Rounding}
21830 @item @code{'Valid}
21834 This rule has no parameters.
21837 @node Non_Tagged_Derived_Types
21838 @subsection @code{Non_Tagged_Derived_Types}
21839 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21842 Flag all derived type declarations that do not have a record extension part.
21844 This rule has no parameters.
21848 @node Non_Visible_Exceptions
21849 @subsection @code{Non_Visible_Exceptions}
21850 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21853 Flag constructs leading to the possibility of propagating an exception
21854 out of the scope in which the exception is declared.
21855 Two cases are detected:
21859 An exception declaration in a subprogram body, task body or block
21860 statement is flagged if the body or statement does not contain a handler for
21861 that exception or a handler with an @code{others} choice.
21864 A @code{raise} statement in an exception handler of a subprogram body,
21865 task body or block statement is flagged if it (re)raises a locally
21866 declared exception. This may occur under the following circumstances:
21869 it explicitly raises a locally declared exception, or
21871 it does not specify an exception name (i.e., it is simply @code{raise;})
21872 and the enclosing handler contains a locally declared exception in its
21878 Renamings of local exceptions are not flagged.
21880 This rule has no parameters.
21883 @node Numeric_Literals
21884 @subsection @code{Numeric_Literals}
21885 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21888 Flag each use of a numeric literal in an index expression, and in any
21889 circumstance except for the following:
21893 a literal occurring in the initialization expression for a constant
21894 declaration or a named number declaration, or
21897 an integer literal that is less than or equal to a value
21898 specified by the @option{N} rule parameter.
21902 This rule may have the following parameters for the @option{+R} option:
21906 @emph{N} is an integer literal used as the maximal value that is not flagged
21907 (i.e., integer literals not exceeding this value are allowed)
21910 All integer literals are flagged
21914 If no parameters are set, the maximum unflagged value is 1.
21916 The last specified check limit (or the fact that there is no limit at
21917 all) is used when multiple @option{+R} options appear.
21919 The @option{-R} option for this rule has no parameters.
21920 It disables the rule but retains the last specified maximum unflagged value.
21921 If the @option{+R} option subsequently appears, this value is used as the
21922 threshold for the check.
21925 @node OTHERS_In_Aggregates
21926 @subsection @code{OTHERS_In_Aggregates}
21927 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21930 Flag each use of an @code{others} choice in extension aggregates.
21931 In record and array aggregates, an @code{others} choice is flagged unless
21932 it is used to refer to all components, or to all but one component.
21934 If, in case of a named array aggregate, there are two associations, one
21935 with an @code{others} choice and another with a discrete range, the
21936 @code{others} choice is flagged even if the discrete range specifies
21937 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21939 This rule has no parameters.
21941 @node OTHERS_In_CASE_Statements
21942 @subsection @code{OTHERS_In_CASE_Statements}
21943 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21946 Flag any use of an @code{others} choice in a @code{case} statement.
21948 This rule has no parameters.
21950 @node OTHERS_In_Exception_Handlers
21951 @subsection @code{OTHERS_In_Exception_Handlers}
21952 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21955 Flag any use of an @code{others} choice in an exception handler.
21957 This rule has no parameters.
21960 @node Outer_Loop_Exits
21961 @subsection @code{Outer_Loop_Exits}
21962 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21965 Flag each @code{exit} statement containing a loop name that is not the name
21966 of the immediately enclosing @code{loop} statement.
21968 This rule has no parameters.
21971 @node Overloaded_Operators
21972 @subsection @code{Overloaded_Operators}
21973 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21976 Flag each function declaration that overloads an operator symbol.
21977 A function body is checked only if the body does not have a
21978 separate spec. Formal functions are also checked. For a
21979 renaming declaration, only renaming-as-declaration is checked
21981 This rule has no parameters.
21984 @node Overly_Nested_Control_Structures
21985 @subsection @code{Overly_Nested_Control_Structures}
21986 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21989 Flag each control structure whose nesting level exceeds the value provided
21990 in the rule parameter.
21992 The control structures checked are the following:
21995 @item @code{if} statement
21996 @item @code{case} statement
21997 @item @code{loop} statement
21998 @item Selective accept statement
21999 @item Timed entry call statement
22000 @item Conditional entry call
22001 @item Asynchronous select statement
22005 The rule has the following parameter for the @option{+R} option:
22009 Positive integer specifying the maximal control structure nesting
22010 level that is not flagged
22014 If the parameter for the @option{+R} option is not specified or
22015 if it is not a positive integer, @option{+R} option is ignored.
22017 If more then one option is specified for the gnatcheck call, the later option and
22018 new parameter override the previous one(s).
22021 @node Parameters_Out_Of_Order
22022 @subsection @code{Parameters_Out_Of_Order}
22023 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22026 Flag each subprogram and entry declaration whose formal parameters are not
22027 ordered according to the following scheme:
22031 @item @code{in} and @code{access} parameters first,
22032 then @code{in out} parameters,
22033 and then @code{out} parameters;
22035 @item for @code{in} mode, parameters with default initialization expressions
22040 Only the first violation of the described order is flagged.
22042 The following constructs are checked:
22045 @item subprogram declarations (including null procedures);
22046 @item generic subprogram declarations;
22047 @item formal subprogram declarations;
22048 @item entry declarations;
22049 @item subprogram bodies and subprogram body stubs that do not
22050 have separate specifications
22054 Subprogram renamings are not checked.
22056 This rule has no parameters.
22059 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22060 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22061 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22064 Flag each generic actual parameter corresponding to a generic formal
22065 parameter with a default initialization, if positional notation is used.
22067 This rule has no parameters.
22069 @node Positional_Actuals_For_Defaulted_Parameters
22070 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22071 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22074 Flag each actual parameter to a subprogram or entry call where the
22075 corresponding formal parameter has a default expression, if positional
22078 This rule has no parameters.
22080 @node Positional_Components
22081 @subsection @code{Positional_Components}
22082 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22085 Flag each array, record and extension aggregate that includes positional
22088 This rule has no parameters.
22091 @node Positional_Generic_Parameters
22092 @subsection @code{Positional_Generic_Parameters}
22093 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22096 Flag each instantiation using positional parameter notation.
22098 This rule has no parameters.
22101 @node Positional_Parameters
22102 @subsection @code{Positional_Parameters}
22103 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22106 Flag each subprogram or entry call using positional parameter notation,
22107 except for the following:
22111 Invocations of prefix or infix operators are not flagged
22113 If the called subprogram or entry has only one formal parameter,
22114 the call is not flagged;
22116 If a subprogram call uses the @emph{Object.Operation} notation, then
22119 the first parameter (that is, @emph{Object}) is not flagged;
22121 if the called subprogram has only two parameters, the second parameter
22122 of the call is not flagged;
22127 This rule has no parameters.
22132 @node Predefined_Numeric_Types
22133 @subsection @code{Predefined_Numeric_Types}
22134 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22137 Flag each explicit use of the name of any numeric type or subtype defined
22138 in package @code{Standard}.
22140 The rationale for this rule is to detect when the
22141 program may depend on platform-specific characteristics of the implementation
22142 of the predefined numeric types. Note that this rule is over-pessimistic;
22143 for example, a program that uses @code{String} indexing
22144 likely needs a variable of type @code{Integer}.
22145 Another example is the flagging of predefined numeric types with explicit
22148 @smallexample @c ada
22149 subtype My_Integer is Integer range Left .. Right;
22150 Vy_Var : My_Integer;
22154 This rule detects only numeric types and subtypes defined in
22155 @code{Standard}. The use of numeric types and subtypes defined in other
22156 predefined packages (such as @code{System.Any_Priority} or
22157 @code{Ada.Text_IO.Count}) is not flagged
22159 This rule has no parameters.
22163 @node Raising_External_Exceptions
22164 @subsection @code{Raising_External_Exceptions}
22165 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22168 Flag any @code{raise} statement, in a program unit declared in a library
22169 package or in a generic library package, for an exception that is
22170 neither a predefined exception nor an exception that is also declared (or
22171 renamed) in the visible part of the package.
22173 This rule has no parameters.
22177 @node Raising_Predefined_Exceptions
22178 @subsection @code{Raising_Predefined_Exceptions}
22179 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22182 Flag each @code{raise} statement that raises a predefined exception
22183 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22184 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22186 This rule has no parameters.
22188 @node Separate_Numeric_Error_Handlers
22189 @subsection @code{Separate_Numeric_Error_Handlers}
22190 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22193 Flags each exception handler that contains a choice for
22194 the predefined @code{Constraint_Error} exception, but does not contain
22195 the choice for the predefined @code{Numeric_Error} exception, or
22196 that contains the choice for @code{Numeric_Error}, but does not contain the
22197 choice for @code{Constraint_Error}.
22199 This rule has no parameters.
22203 @subsection @code{Recursion} (under construction, GLOBAL)
22204 @cindex @code{Recursion} rule (for @command{gnatcheck})
22207 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22208 calls, of recursive subprograms are detected.
22210 This rule has no parameters.
22214 @node Side_Effect_Functions
22215 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22216 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22219 Flag functions with side effects.
22221 We define a side effect as changing any data object that is not local for the
22222 body of this function.
22224 At the moment, we do NOT consider a side effect any input-output operations
22225 (changing a state or a content of any file).
22227 We do not consider protected functions for this rule (???)
22229 There are the following sources of side effect:
22232 @item Explicit (or direct) side-effect:
22236 direct assignment to a non-local variable;
22239 direct call to an entity that is known to change some data object that is
22240 not local for the body of this function (Note, that if F1 calls F2 and F2
22241 does have a side effect, this does not automatically mean that F1 also
22242 have a side effect, because it may be the case that F2 is declared in
22243 F1's body and it changes some data object that is global for F2, but
22247 @item Indirect side-effect:
22250 Subprogram calls implicitly issued by:
22253 computing initialization expressions from type declarations as a part
22254 of object elaboration or allocator evaluation;
22256 computing implicit parameters of subprogram or entry calls or generic
22261 activation of a task that change some non-local data object (directly or
22265 elaboration code of a package that is a result of a package instantiation;
22268 controlled objects;
22271 @item Situations when we can suspect a side-effect, but the full static check
22272 is either impossible or too hard:
22275 assignment to access variables or to the objects pointed by access
22279 call to a subprogram pointed by access-to-subprogram value
22287 This rule has no parameters.
22291 @subsection @code{Slices}
22292 @cindex @code{Slices} rule (for @command{gnatcheck})
22295 Flag all uses of array slicing
22297 This rule has no parameters.
22300 @node Unassigned_OUT_Parameters
22301 @subsection @code{Unassigned_OUT_Parameters}
22302 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22305 Flags procedures' @code{out} parameters that are not assigned, and
22306 identifies the contexts in which the assignments are missing.
22308 An @code{out} parameter is flagged in the statements in the procedure
22309 body's handled sequence of statements (before the procedure body's
22310 @code{exception} part, if any) if this sequence of statements contains
22311 no assignments to the parameter.
22313 An @code{out} parameter is flagged in an exception handler in the exception
22314 part of the procedure body's handled sequence of statements if the handler
22315 contains no assignment to the parameter.
22317 Bodies of generic procedures are also considered.
22319 The following are treated as assignments to an @code{out} parameter:
22323 an assignment statement, with the parameter or some component as the target;
22326 passing the parameter (or one of its components) as an @code{out} or
22327 @code{in out} parameter.
22331 This rule does not have any parameters.
22335 @node Uncommented_BEGIN_In_Package_Bodies
22336 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22337 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22340 Flags each package body with declarations and a statement part that does not
22341 include a trailing comment on the line containing the @code{begin} keyword;
22342 this trailing comment needs to specify the package name and nothing else.
22343 The @code{begin} is not flagged if the package body does not
22344 contain any declarations.
22346 If the @code{begin} keyword is placed on the
22347 same line as the last declaration or the first statement, it is flagged
22348 independently of whether the line contains a trailing comment. The
22349 diagnostic message is attached to the line containing the first statement.
22351 This rule has no parameters.
22353 @node Unconditional_Exits
22354 @subsection @code{Unconditional_Exits}
22355 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22358 Flag unconditional @code{exit} statements.
22360 This rule has no parameters.
22362 @node Unconstrained_Array_Returns
22363 @subsection @code{Unconstrained_Array_Returns}
22364 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22367 Flag each function returning an unconstrained array. Function declarations,
22368 function bodies (and body stubs) having no separate specifications,
22369 and generic function instantiations are checked.
22370 Generic function declarations, function calls and function renamings are
22373 This rule has no parameters.
22375 @node Universal_Ranges
22376 @subsection @code{Universal_Ranges}
22377 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22380 Flag discrete ranges that are a part of an index constraint, constrained
22381 array definition, or @code{for}-loop parameter specification, and whose bounds
22382 are both of type @i{universal_integer}. Ranges that have at least one
22383 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22384 or an expression of non-universal type) are not flagged.
22386 This rule has no parameters.
22389 @node Unnamed_Blocks_And_Loops
22390 @subsection @code{Unnamed_Blocks_And_Loops}
22391 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22394 Flag each unnamed block statement and loop statement.
22396 The rule has no parameters.
22401 @node Unused_Subprograms
22402 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22403 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22406 Flag all unused subprograms.
22408 This rule has no parameters.
22414 @node USE_PACKAGE_Clauses
22415 @subsection @code{USE_PACKAGE_Clauses}
22416 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22419 Flag all @code{use} clauses for packages; @code{use type} clauses are
22422 This rule has no parameters.
22426 @node Volatile_Objects_Without_Address_Clauses
22427 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22428 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22431 Flag each volatile object that does not have an address clause.
22433 The following check is made: if the pragma @code{Volatile} is applied to a
22434 data object or to its type, then an address clause must
22435 be supplied for this object.
22437 This rule does not check the components of data objects,
22438 array components that are volatile as a result of the pragma
22439 @code{Volatile_Components}, or objects that are volatile because
22440 they are atomic as a result of pragmas @code{Atomic} or
22441 @code{Atomic_Components}.
22443 Only variable declarations, and not constant declarations, are checked.
22445 This rule has no parameters.
22448 @c *********************************
22449 @node Creating Sample Bodies Using gnatstub
22450 @chapter Creating Sample Bodies Using @command{gnatstub}
22454 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22455 for library unit declarations.
22457 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22458 driver (see @ref{The GNAT Driver and Project Files}).
22460 To create a body stub, @command{gnatstub} has to compile the library
22461 unit declaration. Therefore, bodies can be created only for legal
22462 library units. Moreover, if a library unit depends semantically upon
22463 units located outside the current directory, you have to provide
22464 the source search path when calling @command{gnatstub}, see the description
22465 of @command{gnatstub} switches below.
22467 By default, all the program unit body stubs generated by @code{gnatstub}
22468 raise the predefined @code{Program_Error} exception, which will catch
22469 accidental calls of generated stubs. This behavior can be changed with
22470 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22473 * Running gnatstub::
22474 * Switches for gnatstub::
22477 @node Running gnatstub
22478 @section Running @command{gnatstub}
22481 @command{gnatstub} has the command-line interface of the form
22484 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22491 is the name of the source file that contains a library unit declaration
22492 for which a body must be created. The file name may contain the path
22494 The file name does not have to follow the GNAT file name conventions. If the
22496 does not follow GNAT file naming conventions, the name of the body file must
22498 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22499 If the file name follows the GNAT file naming
22500 conventions and the name of the body file is not provided,
22503 of the body file from the argument file name by replacing the @file{.ads}
22505 with the @file{.adb} suffix.
22508 indicates the directory in which the body stub is to be placed (the default
22513 is an optional sequence of switches as described in the next section
22516 @node Switches for gnatstub
22517 @section Switches for @command{gnatstub}
22523 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22524 If the destination directory already contains a file with the name of the
22526 for the argument spec file, replace it with the generated body stub.
22528 @item ^-hs^/HEADER=SPEC^
22529 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22530 Put the comment header (i.e., all the comments preceding the
22531 compilation unit) from the source of the library unit declaration
22532 into the body stub.
22534 @item ^-hg^/HEADER=GENERAL^
22535 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22536 Put a sample comment header into the body stub.
22538 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22539 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22540 Use the content of the file as the comment header for a generated body stub.
22544 @cindex @option{-IDIR} (@command{gnatstub})
22546 @cindex @option{-I-} (@command{gnatstub})
22549 @item /NOCURRENT_DIRECTORY
22550 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22552 ^These switches have ^This switch has^ the same meaning as in calls to
22554 ^They define ^It defines ^ the source search path in the call to
22555 @command{gcc} issued
22556 by @command{gnatstub} to compile an argument source file.
22558 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22559 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22560 This switch has the same meaning as in calls to @command{gcc}.
22561 It defines the additional configuration file to be passed to the call to
22562 @command{gcc} issued
22563 by @command{gnatstub} to compile an argument source file.
22565 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22566 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22567 (@var{n} is a non-negative integer). Set the maximum line length in the
22568 body stub to @var{n}; the default is 79. The maximum value that can be
22569 specified is 32767. Note that in the special case of configuration
22570 pragma files, the maximum is always 32767 regardless of whether or
22571 not this switch appears.
22573 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22574 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22575 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22576 the generated body sample to @var{n}.
22577 The default indentation is 3.
22579 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22580 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22581 Order local bodies alphabetically. (By default local bodies are ordered
22582 in the same way as the corresponding local specs in the argument spec file.)
22584 @item ^-i^/INDENTATION=^@var{n}
22585 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22586 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22588 @item ^-k^/TREE_FILE=SAVE^
22589 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22590 Do not remove the tree file (i.e., the snapshot of the compiler internal
22591 structures used by @command{gnatstub}) after creating the body stub.
22593 @item ^-l^/LINE_LENGTH=^@var{n}
22594 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22595 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22597 @item ^--no-exception^/NO_EXCEPTION^
22598 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22599 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22600 This is not always possible for function stubs.
22602 @item ^-o ^/BODY=^@var{body-name}
22603 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22604 Body file name. This should be set if the argument file name does not
22606 the GNAT file naming
22607 conventions. If this switch is omitted the default name for the body will be
22609 from the argument file name according to the GNAT file naming conventions.
22612 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22613 Quiet mode: do not generate a confirmation when a body is
22614 successfully created, and do not generate a message when a body is not
22618 @item ^-r^/TREE_FILE=REUSE^
22619 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22620 Reuse the tree file (if it exists) instead of creating it. Instead of
22621 creating the tree file for the library unit declaration, @command{gnatstub}
22622 tries to find it in the current directory and use it for creating
22623 a body. If the tree file is not found, no body is created. This option
22624 also implies @option{^-k^/SAVE^}, whether or not
22625 the latter is set explicitly.
22627 @item ^-t^/TREE_FILE=OVERWRITE^
22628 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22629 Overwrite the existing tree file. If the current directory already
22630 contains the file which, according to the GNAT file naming rules should
22631 be considered as a tree file for the argument source file,
22633 will refuse to create the tree file needed to create a sample body
22634 unless this option is set.
22636 @item ^-v^/VERBOSE^
22637 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22638 Verbose mode: generate version information.
22642 @c *********************************
22643 @node Generating Ada Bindings for C and C++ headers
22644 @chapter Generating Ada Bindings for C and C++ headers
22648 GNAT now comes with a new experimental binding generator for C and C++
22649 headers which is intended to do 95% of the tedious work of generating
22650 Ada specs from C or C++ header files. Note that this still is a work in
22651 progress, not designed to generate 100% correct Ada specs.
22653 The code generated is using the Ada 2005 syntax, which makes it
22654 easier to interface with other languages than previous versions of Ada.
22657 * Running the binding generator::
22658 * Generating bindings for C++ headers::
22662 @node Running the binding generator
22663 @section Running the binding generator
22666 The binding generator is part of the @command{gcc} compiler and can be
22667 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
22668 spec files for the header files specified on the command line, and all
22669 header files needed by these files transitivitely. For example:
22672 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
22673 $ gcc -c -gnat05 *.ads
22676 will generate, under GNU/Linux, the following files: @file{time_h.ads},
22677 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
22678 correspond to the files @file{/usr/include/time.h},
22679 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
22680 mode these Ada specs.
22682 The @code{-C} switch tells @command{gcc} to extract comments from headers,
22683 and will attempt to generate corresponding Ada comments.
22685 If you want to generate a single Ada file and not the transitive closure, you
22686 can use instead the @option{-fdump-ada-spec-slim} switch.
22688 Note that we recommend when possible to use the @command{g++} driver to
22689 generate bindings, even for most C headers, since this will in general
22690 generate better Ada specs. For generating bindings for C++ headers, it is
22691 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
22692 is equivalent in this case. If @command{g++} cannot work on your C headers
22693 because of incompatibilities between C and C++, then you can fallback to
22694 @command{gcc} instead.
22696 For an example of better bindings generated from the C++ front-end,
22697 the name of the parameters (when available) are actually ignored by the C
22698 front-end. Consider the following C header:
22701 extern void foo (int variable);
22704 with the C front-end, @code{variable} is ignored, and the above is handled as:
22707 extern void foo (int);
22710 generating a generic:
22713 procedure foo (param1 : int);
22716 with the C++ front-end, the name is available, and we generate:
22719 procedure foo (variable : int);
22722 In some cases, the generated bindings will be more complete or more meaningful
22723 when defining some macros, which you can do via the @option{-D} switch. This
22724 is for example the case with @file{Xlib.h} under GNU/Linux:
22727 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
22730 The above will generate more complete bindings than a straight call without
22731 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
22733 In other cases, it is not possible to parse a header file in a stand alone
22734 manner, because other include files need to be included first. In this
22735 case, the solution is to create a small header file including the needed
22736 @code{#include} and possible @code{#define} directives. For example, to
22737 generate Ada bindings for @file{readline/readline.h}, you need to first
22738 include @file{stdio.h}, so you can create a file with the following two
22739 lines in e.g. @file{readline1.h}:
22743 #include <readline/readline.h>
22746 and then generate Ada bindings from this file:
22749 $ g++ -c -fdump-ada-spec readline1.h
22752 @node Generating bindings for C++ headers
22753 @section Generating bindings for C++ headers
22756 Generating bindings for C++ headers is done using the same options, always
22757 with the @command{g++} compiler.
22759 In this mode, C++ classes will be mapped to Ada tagged types, constructors
22760 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
22761 multiple inheritance of abstract classes will be mapped to Ada interfaces
22762 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
22763 information on interfacing to C++).
22765 For example, given the following C++ header file:
22772 virtual int Number_Of_Teeth () = 0;
22777 virtual void Set_Owner (char* Name) = 0;
22783 virtual void Set_Age (int New_Age);
22786 class Dog : Animal, Carnivore, Domestic @{
22791 virtual int Number_Of_Teeth ();
22792 virtual void Set_Owner (char* Name);
22800 The corresponding Ada code is generated:
22802 @smallexample @c ada
22805 package Class_Carnivore is
22806 type Carnivore is limited interface;
22807 pragma Import (CPP, Carnivore);
22809 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
22811 use Class_Carnivore;
22813 package Class_Domestic is
22814 type Domestic is limited interface;
22815 pragma Import (CPP, Domestic);
22817 procedure Set_Owner
22818 (this : access Domestic;
22819 Name : Interfaces.C.Strings.chars_ptr) is abstract;
22821 use Class_Domestic;
22823 package Class_Animal is
22824 type Animal is tagged limited record
22825 Age_Count : aliased int;
22827 pragma Import (CPP, Animal);
22829 procedure Set_Age (this : access Animal; New_Age : int);
22830 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
22834 package Class_Dog is
22835 type Dog is new Animal and Carnivore and Domestic with record
22836 Tooth_Count : aliased int;
22837 Owner : Interfaces.C.Strings.chars_ptr;
22839 pragma Import (CPP, Dog);
22841 function Number_Of_Teeth (this : access Dog) return int;
22842 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
22844 procedure Set_Owner
22845 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
22846 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
22848 function New_Dog return Dog;
22849 pragma CPP_Constructor (New_Dog);
22850 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
22861 @item -fdump-ada-spec
22862 @cindex @option{-fdump-ada-spec} (@command{gcc})
22863 Generate Ada spec files for the given header files transitively (including
22864 all header files that these headers depend upon).
22866 @item -fdump-ada-spec-slim
22867 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
22868 Generate Ada spec files for the header files specified on the command line
22872 @cindex @option{-C} (@command{gcc})
22873 Extract comments from headers and generate Ada comments in the Ada spec files.
22876 @node Other Utility Programs
22877 @chapter Other Utility Programs
22880 This chapter discusses some other utility programs available in the Ada
22884 * Using Other Utility Programs with GNAT::
22885 * The External Symbol Naming Scheme of GNAT::
22886 * Converting Ada Files to html with gnathtml::
22887 * Installing gnathtml::
22894 @node Using Other Utility Programs with GNAT
22895 @section Using Other Utility Programs with GNAT
22898 The object files generated by GNAT are in standard system format and in
22899 particular the debugging information uses this format. This means
22900 programs generated by GNAT can be used with existing utilities that
22901 depend on these formats.
22904 In general, any utility program that works with C will also often work with
22905 Ada programs generated by GNAT. This includes software utilities such as
22906 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22910 @node The External Symbol Naming Scheme of GNAT
22911 @section The External Symbol Naming Scheme of GNAT
22914 In order to interpret the output from GNAT, when using tools that are
22915 originally intended for use with other languages, it is useful to
22916 understand the conventions used to generate link names from the Ada
22919 All link names are in all lowercase letters. With the exception of library
22920 procedure names, the mechanism used is simply to use the full expanded
22921 Ada name with dots replaced by double underscores. For example, suppose
22922 we have the following package spec:
22924 @smallexample @c ada
22935 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22936 the corresponding link name is @code{qrs__mn}.
22938 Of course if a @code{pragma Export} is used this may be overridden:
22940 @smallexample @c ada
22945 pragma Export (Var1, C, External_Name => "var1_name");
22947 pragma Export (Var2, C, Link_Name => "var2_link_name");
22954 In this case, the link name for @var{Var1} is whatever link name the
22955 C compiler would assign for the C function @var{var1_name}. This typically
22956 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22957 system conventions, but other possibilities exist. The link name for
22958 @var{Var2} is @var{var2_link_name}, and this is not operating system
22962 One exception occurs for library level procedures. A potential ambiguity
22963 arises between the required name @code{_main} for the C main program,
22964 and the name we would otherwise assign to an Ada library level procedure
22965 called @code{Main} (which might well not be the main program).
22967 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22968 names. So if we have a library level procedure such as
22970 @smallexample @c ada
22973 procedure Hello (S : String);
22979 the external name of this procedure will be @var{_ada_hello}.
22982 @node Converting Ada Files to html with gnathtml
22983 @section Converting Ada Files to HTML with @code{gnathtml}
22986 This @code{Perl} script allows Ada source files to be browsed using
22987 standard Web browsers. For installation procedure, see the section
22988 @xref{Installing gnathtml}.
22990 Ada reserved keywords are highlighted in a bold font and Ada comments in
22991 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22992 switch to suppress the generation of cross-referencing information, user
22993 defined variables and types will appear in a different color; you will
22994 be able to click on any identifier and go to its declaration.
22996 The command line is as follow:
22998 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
23002 You can pass it as many Ada files as you want. @code{gnathtml} will generate
23003 an html file for every ada file, and a global file called @file{index.htm}.
23004 This file is an index of every identifier defined in the files.
23006 The available ^switches^options^ are the following ones:
23010 @cindex @option{-83} (@code{gnathtml})
23011 Only the Ada 83 subset of keywords will be highlighted.
23013 @item -cc @var{color}
23014 @cindex @option{-cc} (@code{gnathtml})
23015 This option allows you to change the color used for comments. The default
23016 value is green. The color argument can be any name accepted by html.
23019 @cindex @option{-d} (@code{gnathtml})
23020 If the Ada files depend on some other files (for instance through
23021 @code{with} clauses, the latter files will also be converted to html.
23022 Only the files in the user project will be converted to html, not the files
23023 in the run-time library itself.
23026 @cindex @option{-D} (@code{gnathtml})
23027 This command is the same as @option{-d} above, but @command{gnathtml} will
23028 also look for files in the run-time library, and generate html files for them.
23030 @item -ext @var{extension}
23031 @cindex @option{-ext} (@code{gnathtml})
23032 This option allows you to change the extension of the generated HTML files.
23033 If you do not specify an extension, it will default to @file{htm}.
23036 @cindex @option{-f} (@code{gnathtml})
23037 By default, gnathtml will generate html links only for global entities
23038 ('with'ed units, global variables and types,@dots{}). If you specify
23039 @option{-f} on the command line, then links will be generated for local
23042 @item -l @var{number}
23043 @cindex @option{-l} (@code{gnathtml})
23044 If this ^switch^option^ is provided and @var{number} is not 0, then
23045 @code{gnathtml} will number the html files every @var{number} line.
23048 @cindex @option{-I} (@code{gnathtml})
23049 Specify a directory to search for library files (@file{.ALI} files) and
23050 source files. You can provide several -I switches on the command line,
23051 and the directories will be parsed in the order of the command line.
23054 @cindex @option{-o} (@code{gnathtml})
23055 Specify the output directory for html files. By default, gnathtml will
23056 saved the generated html files in a subdirectory named @file{html/}.
23058 @item -p @var{file}
23059 @cindex @option{-p} (@code{gnathtml})
23060 If you are using Emacs and the most recent Emacs Ada mode, which provides
23061 a full Integrated Development Environment for compiling, checking,
23062 running and debugging applications, you may use @file{.gpr} files
23063 to give the directories where Emacs can find sources and object files.
23065 Using this ^switch^option^, you can tell gnathtml to use these files.
23066 This allows you to get an html version of your application, even if it
23067 is spread over multiple directories.
23069 @item -sc @var{color}
23070 @cindex @option{-sc} (@code{gnathtml})
23071 This ^switch^option^ allows you to change the color used for symbol
23073 The default value is red. The color argument can be any name accepted by html.
23075 @item -t @var{file}
23076 @cindex @option{-t} (@code{gnathtml})
23077 This ^switch^option^ provides the name of a file. This file contains a list of
23078 file names to be converted, and the effect is exactly as though they had
23079 appeared explicitly on the command line. This
23080 is the recommended way to work around the command line length limit on some
23085 @node Installing gnathtml
23086 @section Installing @code{gnathtml}
23089 @code{Perl} needs to be installed on your machine to run this script.
23090 @code{Perl} is freely available for almost every architecture and
23091 Operating System via the Internet.
23093 On Unix systems, you may want to modify the first line of the script
23094 @code{gnathtml}, to explicitly tell the Operating system where Perl
23095 is. The syntax of this line is:
23097 #!full_path_name_to_perl
23101 Alternatively, you may run the script using the following command line:
23104 $ perl gnathtml.pl @ovar{switches} @var{files}
23113 The GNAT distribution provides an Ada 95 template for the HP Language
23114 Sensitive Editor (LSE), a component of DECset. In order to
23115 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23122 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23123 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23124 the collection phase with the /DEBUG qualifier.
23127 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23128 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23129 $ RUN/DEBUG <PROGRAM_NAME>
23135 @c ******************************
23136 @node Code Coverage and Profiling
23137 @chapter Code Coverage and Profiling
23138 @cindex Code Coverage
23142 This chapter describes how to use @code{gcov} - coverage testing tool - and
23143 @code{gprof} - profiler tool - on your Ada programs.
23146 * Code Coverage of Ada Programs using gcov::
23147 * Profiling an Ada Program using gprof::
23150 @node Code Coverage of Ada Programs using gcov
23151 @section Code Coverage of Ada Programs using gcov
23153 @cindex -fprofile-arcs
23154 @cindex -ftest-coverage
23156 @cindex Code Coverage
23159 @code{gcov} is a test coverage program: it analyzes the execution of a given
23160 program on selected tests, to help you determine the portions of the program
23161 that are still untested.
23163 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23164 User's Guide. You can refer to this documentation for a more complete
23167 This chapter provides a quick startup guide, and
23168 details some Gnat-specific features.
23171 * Quick startup guide::
23175 @node Quick startup guide
23176 @subsection Quick startup guide
23178 In order to perform coverage analysis of a program using @code{gcov}, 3
23183 Code instrumentation during the compilation process
23185 Execution of the instrumented program
23187 Execution of the @code{gcov} tool to generate the result.
23190 The code instrumentation needed by gcov is created at the object level:
23191 The source code is not modified in any way, because the instrumentation code is
23192 inserted by gcc during the compilation process. To compile your code with code
23193 coverage activated, you need to recompile your whole project using the
23195 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23196 @code{-fprofile-arcs}.
23199 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23200 -largs -fprofile-arcs
23203 This compilation process will create @file{.gcno} files together with
23204 the usual object files.
23206 Once the program is compiled with coverage instrumentation, you can
23207 run it as many times as needed - on portions of a test suite for
23208 example. The first execution will produce @file{.gcda} files at the
23209 same location as the @file{.gcno} files. The following executions
23210 will update those files, so that a cumulative result of the covered
23211 portions of the program is generated.
23213 Finally, you need to call the @code{gcov} tool. The different options of
23214 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23216 This will create annotated source files with a @file{.gcov} extension:
23217 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23219 @node Gnat specifics
23220 @subsection Gnat specifics
23222 Because Ada semantics, portions of the source code may be shared among
23223 several object files. This is the case for example when generics are
23224 involved, when inlining is active or when declarations generate initialisation
23225 calls. In order to take
23226 into account this shared code, you need to call @code{gcov} on all
23227 source files of the tested program at once.
23229 The list of source files might exceed the system's maximum command line
23230 length. In order to bypass this limitation, a new mechanism has been
23231 implemented in @code{gcov}: you can now list all your project's files into a
23232 text file, and provide this file to gcov as a parameter, preceded by a @@
23233 (e.g. @samp{gcov @@mysrclist.txt}).
23235 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23236 not supported as there can be unresolved symbols during the final link.
23238 @node Profiling an Ada Program using gprof
23239 @section Profiling an Ada Program using gprof
23245 This section is not meant to be an exhaustive documentation of @code{gprof}.
23246 Full documentation for it can be found in the GNU Profiler User's Guide
23247 documentation that is part of this GNAT distribution.
23249 Profiling a program helps determine the parts of a program that are executed
23250 most often, and are therefore the most time-consuming.
23252 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23253 better handle Ada programs and multitasking.
23254 It is currently supported on the following platforms
23259 solaris sparc/sparc64/x86
23265 In order to profile a program using @code{gprof}, 3 steps are needed:
23269 Code instrumentation, requiring a full recompilation of the project with the
23272 Execution of the program under the analysis conditions, i.e. with the desired
23275 Analysis of the results using the @code{gprof} tool.
23279 The following sections detail the different steps, and indicate how
23280 to interpret the results:
23282 * Compilation for profiling::
23283 * Program execution::
23285 * Interpretation of profiling results::
23288 @node Compilation for profiling
23289 @subsection Compilation for profiling
23293 In order to profile a program the first step is to tell the compiler
23294 to generate the necessary profiling information. The compiler switch to be used
23295 is @code{-pg}, which must be added to other compilation switches. This
23296 switch needs to be specified both during compilation and link stages, and can
23297 be specified once when using gnatmake:
23300 gnatmake -f -pg -P my_project
23304 Note that only the objects that were compiled with the @samp{-pg} switch will be
23305 profiled; if you need to profile your whole project, use the
23306 @samp{-f} gnatmake switch to force full recompilation.
23308 @node Program execution
23309 @subsection Program execution
23312 Once the program has been compiled for profiling, you can run it as usual.
23314 The only constraint imposed by profiling is that the program must terminate
23315 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23318 Once the program completes execution, a data file called @file{gmon.out} is
23319 generated in the directory where the program was launched from. If this file
23320 already exists, it will be overwritten.
23322 @node Running gprof
23323 @subsection Running gprof
23326 The @code{gprof} tool is called as follow:
23329 gprof my_prog gmon.out
23340 The complete form of the gprof command line is the following:
23343 gprof [^switches^options^] [executable [data-file]]
23347 @code{gprof} supports numerous ^switch^options^. The order of these
23348 ^switch^options^ does not matter. The full list of options can be found in
23349 the GNU Profiler User's Guide documentation that comes with this documentation.
23351 The following is the subset of those switches that is most relevant:
23355 @item --demangle[=@var{style}]
23356 @itemx --no-demangle
23357 @cindex @option{--demangle} (@code{gprof})
23358 These options control whether symbol names should be demangled when
23359 printing output. The default is to demangle C++ symbols. The
23360 @code{--no-demangle} option may be used to turn off demangling. Different
23361 compilers have different mangling styles. The optional demangling style
23362 argument can be used to choose an appropriate demangling style for your
23363 compiler, in particular Ada symbols generated by GNAT can be demangled using
23364 @code{--demangle=gnat}.
23366 @item -e @var{function_name}
23367 @cindex @option{-e} (@code{gprof})
23368 The @samp{-e @var{function}} option tells @code{gprof} not to print
23369 information about the function @var{function_name} (and its
23370 children@dots{}) in the call graph. The function will still be listed
23371 as a child of any functions that call it, but its index number will be
23372 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23373 given; only one @var{function_name} may be indicated with each @samp{-e}
23376 @item -E @var{function_name}
23377 @cindex @option{-E} (@code{gprof})
23378 The @code{-E @var{function}} option works like the @code{-e} option, but
23379 execution time spent in the function (and children who were not called from
23380 anywhere else), will not be used to compute the percentages-of-time for
23381 the call graph. More than one @samp{-E} option may be given; only one
23382 @var{function_name} may be indicated with each @samp{-E} option.
23384 @item -f @var{function_name}
23385 @cindex @option{-f} (@code{gprof})
23386 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23387 call graph to the function @var{function_name} and its children (and
23388 their children@dots{}). More than one @samp{-f} option may be given;
23389 only one @var{function_name} may be indicated with each @samp{-f}
23392 @item -F @var{function_name}
23393 @cindex @option{-F} (@code{gprof})
23394 The @samp{-F @var{function}} option works like the @code{-f} option, but
23395 only time spent in the function and its children (and their
23396 children@dots{}) will be used to determine total-time and
23397 percentages-of-time for the call graph. More than one @samp{-F} option
23398 may be given; only one @var{function_name} may be indicated with each
23399 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23403 @node Interpretation of profiling results
23404 @subsection Interpretation of profiling results
23408 The results of the profiling analysis are represented by two arrays: the
23409 'flat profile' and the 'call graph'. Full documentation of those outputs
23410 can be found in the GNU Profiler User's Guide.
23412 The flat profile shows the time spent in each function of the program, and how
23413 many time it has been called. This allows you to locate easily the most
23414 time-consuming functions.
23416 The call graph shows, for each subprogram, the subprograms that call it,
23417 and the subprograms that it calls. It also provides an estimate of the time
23418 spent in each of those callers/called subprograms.
23421 @c ******************************
23422 @node Running and Debugging Ada Programs
23423 @chapter Running and Debugging Ada Programs
23427 This chapter discusses how to debug Ada programs.
23429 It applies to GNAT on the Alpha OpenVMS platform;
23430 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23431 since HP has implemented Ada support in the OpenVMS debugger on I64.
23434 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23438 The illegality may be a violation of the static semantics of Ada. In
23439 that case GNAT diagnoses the constructs in the program that are illegal.
23440 It is then a straightforward matter for the user to modify those parts of
23444 The illegality may be a violation of the dynamic semantics of Ada. In
23445 that case the program compiles and executes, but may generate incorrect
23446 results, or may terminate abnormally with some exception.
23449 When presented with a program that contains convoluted errors, GNAT
23450 itself may terminate abnormally without providing full diagnostics on
23451 the incorrect user program.
23455 * The GNAT Debugger GDB::
23457 * Introduction to GDB Commands::
23458 * Using Ada Expressions::
23459 * Calling User-Defined Subprograms::
23460 * Using the Next Command in a Function::
23463 * Debugging Generic Units::
23464 * GNAT Abnormal Termination or Failure to Terminate::
23465 * Naming Conventions for GNAT Source Files::
23466 * Getting Internal Debugging Information::
23467 * Stack Traceback::
23473 @node The GNAT Debugger GDB
23474 @section The GNAT Debugger GDB
23477 @code{GDB} is a general purpose, platform-independent debugger that
23478 can be used to debug mixed-language programs compiled with @command{gcc},
23479 and in particular is capable of debugging Ada programs compiled with
23480 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23481 complex Ada data structures.
23483 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23485 located in the GNU:[DOCS] directory,
23487 for full details on the usage of @code{GDB}, including a section on
23488 its usage on programs. This manual should be consulted for full
23489 details. The section that follows is a brief introduction to the
23490 philosophy and use of @code{GDB}.
23492 When GNAT programs are compiled, the compiler optionally writes debugging
23493 information into the generated object file, including information on
23494 line numbers, and on declared types and variables. This information is
23495 separate from the generated code. It makes the object files considerably
23496 larger, but it does not add to the size of the actual executable that
23497 will be loaded into memory, and has no impact on run-time performance. The
23498 generation of debug information is triggered by the use of the
23499 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23500 used to carry out the compilations. It is important to emphasize that
23501 the use of these options does not change the generated code.
23503 The debugging information is written in standard system formats that
23504 are used by many tools, including debuggers and profilers. The format
23505 of the information is typically designed to describe C types and
23506 semantics, but GNAT implements a translation scheme which allows full
23507 details about Ada types and variables to be encoded into these
23508 standard C formats. Details of this encoding scheme may be found in
23509 the file exp_dbug.ads in the GNAT source distribution. However, the
23510 details of this encoding are, in general, of no interest to a user,
23511 since @code{GDB} automatically performs the necessary decoding.
23513 When a program is bound and linked, the debugging information is
23514 collected from the object files, and stored in the executable image of
23515 the program. Again, this process significantly increases the size of
23516 the generated executable file, but it does not increase the size of
23517 the executable program itself. Furthermore, if this program is run in
23518 the normal manner, it runs exactly as if the debug information were
23519 not present, and takes no more actual memory.
23521 However, if the program is run under control of @code{GDB}, the
23522 debugger is activated. The image of the program is loaded, at which
23523 point it is ready to run. If a run command is given, then the program
23524 will run exactly as it would have if @code{GDB} were not present. This
23525 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23526 entirely non-intrusive until a breakpoint is encountered. If no
23527 breakpoint is ever hit, the program will run exactly as it would if no
23528 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23529 the debugging information and can respond to user commands to inspect
23530 variables, and more generally to report on the state of execution.
23534 @section Running GDB
23537 This section describes how to initiate the debugger.
23538 @c The above sentence is really just filler, but it was otherwise
23539 @c clumsy to get the first paragraph nonindented given the conditional
23540 @c nature of the description
23543 The debugger can be launched from a @code{GPS} menu or
23544 directly from the command line. The description below covers the latter use.
23545 All the commands shown can be used in the @code{GPS} debug console window,
23546 but there are usually more GUI-based ways to achieve the same effect.
23549 The command to run @code{GDB} is
23552 $ ^gdb program^GDB PROGRAM^
23556 where @code{^program^PROGRAM^} is the name of the executable file. This
23557 activates the debugger and results in a prompt for debugger commands.
23558 The simplest command is simply @code{run}, which causes the program to run
23559 exactly as if the debugger were not present. The following section
23560 describes some of the additional commands that can be given to @code{GDB}.
23562 @c *******************************
23563 @node Introduction to GDB Commands
23564 @section Introduction to GDB Commands
23567 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23568 Debugging with GDB, gdb, Debugging with GDB},
23570 located in the GNU:[DOCS] directory,
23572 for extensive documentation on the use
23573 of these commands, together with examples of their use. Furthermore,
23574 the command @command{help} invoked from within GDB activates a simple help
23575 facility which summarizes the available commands and their options.
23576 In this section we summarize a few of the most commonly
23577 used commands to give an idea of what @code{GDB} is about. You should create
23578 a simple program with debugging information and experiment with the use of
23579 these @code{GDB} commands on the program as you read through the
23583 @item set args @var{arguments}
23584 The @var{arguments} list above is a list of arguments to be passed to
23585 the program on a subsequent run command, just as though the arguments
23586 had been entered on a normal invocation of the program. The @code{set args}
23587 command is not needed if the program does not require arguments.
23590 The @code{run} command causes execution of the program to start from
23591 the beginning. If the program is already running, that is to say if
23592 you are currently positioned at a breakpoint, then a prompt will ask
23593 for confirmation that you want to abandon the current execution and
23596 @item breakpoint @var{location}
23597 The breakpoint command sets a breakpoint, that is to say a point at which
23598 execution will halt and @code{GDB} will await further
23599 commands. @var{location} is
23600 either a line number within a file, given in the format @code{file:linenumber},
23601 or it is the name of a subprogram. If you request that a breakpoint be set on
23602 a subprogram that is overloaded, a prompt will ask you to specify on which of
23603 those subprograms you want to breakpoint. You can also
23604 specify that all of them should be breakpointed. If the program is run
23605 and execution encounters the breakpoint, then the program
23606 stops and @code{GDB} signals that the breakpoint was encountered by
23607 printing the line of code before which the program is halted.
23609 @item breakpoint exception @var{name}
23610 A special form of the breakpoint command which breakpoints whenever
23611 exception @var{name} is raised.
23612 If @var{name} is omitted,
23613 then a breakpoint will occur when any exception is raised.
23615 @item print @var{expression}
23616 This will print the value of the given expression. Most simple
23617 Ada expression formats are properly handled by @code{GDB}, so the expression
23618 can contain function calls, variables, operators, and attribute references.
23621 Continues execution following a breakpoint, until the next breakpoint or the
23622 termination of the program.
23625 Executes a single line after a breakpoint. If the next statement
23626 is a subprogram call, execution continues into (the first statement of)
23627 the called subprogram.
23630 Executes a single line. If this line is a subprogram call, executes and
23631 returns from the call.
23634 Lists a few lines around the current source location. In practice, it
23635 is usually more convenient to have a separate edit window open with the
23636 relevant source file displayed. Successive applications of this command
23637 print subsequent lines. The command can be given an argument which is a
23638 line number, in which case it displays a few lines around the specified one.
23641 Displays a backtrace of the call chain. This command is typically
23642 used after a breakpoint has occurred, to examine the sequence of calls that
23643 leads to the current breakpoint. The display includes one line for each
23644 activation record (frame) corresponding to an active subprogram.
23647 At a breakpoint, @code{GDB} can display the values of variables local
23648 to the current frame. The command @code{up} can be used to
23649 examine the contents of other active frames, by moving the focus up
23650 the stack, that is to say from callee to caller, one frame at a time.
23653 Moves the focus of @code{GDB} down from the frame currently being
23654 examined to the frame of its callee (the reverse of the previous command),
23656 @item frame @var{n}
23657 Inspect the frame with the given number. The value 0 denotes the frame
23658 of the current breakpoint, that is to say the top of the call stack.
23663 The above list is a very short introduction to the commands that
23664 @code{GDB} provides. Important additional capabilities, including conditional
23665 breakpoints, the ability to execute command sequences on a breakpoint,
23666 the ability to debug at the machine instruction level and many other
23667 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
23668 Debugging with GDB}. Note that most commands can be abbreviated
23669 (for example, c for continue, bt for backtrace).
23671 @node Using Ada Expressions
23672 @section Using Ada Expressions
23673 @cindex Ada expressions
23676 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23677 extensions. The philosophy behind the design of this subset is
23681 That @code{GDB} should provide basic literals and access to operations for
23682 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23683 leaving more sophisticated computations to subprograms written into the
23684 program (which therefore may be called from @code{GDB}).
23687 That type safety and strict adherence to Ada language restrictions
23688 are not particularly important to the @code{GDB} user.
23691 That brevity is important to the @code{GDB} user.
23695 Thus, for brevity, the debugger acts as if there were
23696 implicit @code{with} and @code{use} clauses in effect for all user-written
23697 packages, thus making it unnecessary to fully qualify most names with
23698 their packages, regardless of context. Where this causes ambiguity,
23699 @code{GDB} asks the user's intent.
23701 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23702 GDB, gdb, Debugging with GDB}.
23704 @node Calling User-Defined Subprograms
23705 @section Calling User-Defined Subprograms
23708 An important capability of @code{GDB} is the ability to call user-defined
23709 subprograms while debugging. This is achieved simply by entering
23710 a subprogram call statement in the form:
23713 call subprogram-name (parameters)
23717 The keyword @code{call} can be omitted in the normal case where the
23718 @code{subprogram-name} does not coincide with any of the predefined
23719 @code{GDB} commands.
23721 The effect is to invoke the given subprogram, passing it the
23722 list of parameters that is supplied. The parameters can be expressions and
23723 can include variables from the program being debugged. The
23724 subprogram must be defined
23725 at the library level within your program, and @code{GDB} will call the
23726 subprogram within the environment of your program execution (which
23727 means that the subprogram is free to access or even modify variables
23728 within your program).
23730 The most important use of this facility is in allowing the inclusion of
23731 debugging routines that are tailored to particular data structures
23732 in your program. Such debugging routines can be written to provide a suitably
23733 high-level description of an abstract type, rather than a low-level dump
23734 of its physical layout. After all, the standard
23735 @code{GDB print} command only knows the physical layout of your
23736 types, not their abstract meaning. Debugging routines can provide information
23737 at the desired semantic level and are thus enormously useful.
23739 For example, when debugging GNAT itself, it is crucial to have access to
23740 the contents of the tree nodes used to represent the program internally.
23741 But tree nodes are represented simply by an integer value (which in turn
23742 is an index into a table of nodes).
23743 Using the @code{print} command on a tree node would simply print this integer
23744 value, which is not very useful. But the PN routine (defined in file
23745 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23746 a useful high level representation of the tree node, which includes the
23747 syntactic category of the node, its position in the source, the integers
23748 that denote descendant nodes and parent node, as well as varied
23749 semantic information. To study this example in more detail, you might want to
23750 look at the body of the PN procedure in the stated file.
23752 @node Using the Next Command in a Function
23753 @section Using the Next Command in a Function
23756 When you use the @code{next} command in a function, the current source
23757 location will advance to the next statement as usual. A special case
23758 arises in the case of a @code{return} statement.
23760 Part of the code for a return statement is the ``epilog'' of the function.
23761 This is the code that returns to the caller. There is only one copy of
23762 this epilog code, and it is typically associated with the last return
23763 statement in the function if there is more than one return. In some
23764 implementations, this epilog is associated with the first statement
23767 The result is that if you use the @code{next} command from a return
23768 statement that is not the last return statement of the function you
23769 may see a strange apparent jump to the last return statement or to
23770 the start of the function. You should simply ignore this odd jump.
23771 The value returned is always that from the first return statement
23772 that was stepped through.
23774 @node Ada Exceptions
23775 @section Breaking on Ada Exceptions
23779 You can set breakpoints that trip when your program raises
23780 selected exceptions.
23783 @item break exception
23784 Set a breakpoint that trips whenever (any task in the) program raises
23787 @item break exception @var{name}
23788 Set a breakpoint that trips whenever (any task in the) program raises
23789 the exception @var{name}.
23791 @item break exception unhandled
23792 Set a breakpoint that trips whenever (any task in the) program raises an
23793 exception for which there is no handler.
23795 @item info exceptions
23796 @itemx info exceptions @var{regexp}
23797 The @code{info exceptions} command permits the user to examine all defined
23798 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23799 argument, prints out only those exceptions whose name matches @var{regexp}.
23807 @code{GDB} allows the following task-related commands:
23811 This command shows a list of current Ada tasks, as in the following example:
23818 ID TID P-ID Thread Pri State Name
23819 1 8088000 0 807e000 15 Child Activation Wait main_task
23820 2 80a4000 1 80ae000 15 Accept/Select Wait b
23821 3 809a800 1 80a4800 15 Child Activation Wait a
23822 * 4 80ae800 3 80b8000 15 Running c
23826 In this listing, the asterisk before the first task indicates it to be the
23827 currently running task. The first column lists the task ID that is used
23828 to refer to tasks in the following commands.
23830 @item break @var{linespec} task @var{taskid}
23831 @itemx break @var{linespec} task @var{taskid} if @dots{}
23832 @cindex Breakpoints and tasks
23833 These commands are like the @code{break @dots{} thread @dots{}}.
23834 @var{linespec} specifies source lines.
23836 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23837 to specify that you only want @code{GDB} to stop the program when a
23838 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23839 numeric task identifiers assigned by @code{GDB}, shown in the first
23840 column of the @samp{info tasks} display.
23842 If you do not specify @samp{task @var{taskid}} when you set a
23843 breakpoint, the breakpoint applies to @emph{all} tasks of your
23846 You can use the @code{task} qualifier on conditional breakpoints as
23847 well; in this case, place @samp{task @var{taskid}} before the
23848 breakpoint condition (before the @code{if}).
23850 @item task @var{taskno}
23851 @cindex Task switching
23853 This command allows to switch to the task referred by @var{taskno}. In
23854 particular, This allows to browse the backtrace of the specified
23855 task. It is advised to switch back to the original task before
23856 continuing execution otherwise the scheduling of the program may be
23861 For more detailed information on the tasking support,
23862 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23864 @node Debugging Generic Units
23865 @section Debugging Generic Units
23866 @cindex Debugging Generic Units
23870 GNAT always uses code expansion for generic instantiation. This means that
23871 each time an instantiation occurs, a complete copy of the original code is
23872 made, with appropriate substitutions of formals by actuals.
23874 It is not possible to refer to the original generic entities in
23875 @code{GDB}, but it is always possible to debug a particular instance of
23876 a generic, by using the appropriate expanded names. For example, if we have
23878 @smallexample @c ada
23883 generic package k is
23884 procedure kp (v1 : in out integer);
23888 procedure kp (v1 : in out integer) is
23894 package k1 is new k;
23895 package k2 is new k;
23897 var : integer := 1;
23910 Then to break on a call to procedure kp in the k2 instance, simply
23914 (gdb) break g.k2.kp
23918 When the breakpoint occurs, you can step through the code of the
23919 instance in the normal manner and examine the values of local variables, as for
23922 @node GNAT Abnormal Termination or Failure to Terminate
23923 @section GNAT Abnormal Termination or Failure to Terminate
23924 @cindex GNAT Abnormal Termination or Failure to Terminate
23927 When presented with programs that contain serious errors in syntax
23929 GNAT may on rare occasions experience problems in operation, such
23931 segmentation fault or illegal memory access, raising an internal
23932 exception, terminating abnormally, or failing to terminate at all.
23933 In such cases, you can activate
23934 various features of GNAT that can help you pinpoint the construct in your
23935 program that is the likely source of the problem.
23937 The following strategies are presented in increasing order of
23938 difficulty, corresponding to your experience in using GNAT and your
23939 familiarity with compiler internals.
23943 Run @command{gcc} with the @option{-gnatf}. This first
23944 switch causes all errors on a given line to be reported. In its absence,
23945 only the first error on a line is displayed.
23947 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23948 are encountered, rather than after compilation is terminated. If GNAT
23949 terminates prematurely or goes into an infinite loop, the last error
23950 message displayed may help to pinpoint the culprit.
23953 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23954 mode, @command{gcc} produces ongoing information about the progress of the
23955 compilation and provides the name of each procedure as code is
23956 generated. This switch allows you to find which Ada procedure was being
23957 compiled when it encountered a code generation problem.
23960 @cindex @option{-gnatdc} switch
23961 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23962 switch that does for the front-end what @option{^-v^VERBOSE^} does
23963 for the back end. The system prints the name of each unit,
23964 either a compilation unit or nested unit, as it is being analyzed.
23966 Finally, you can start
23967 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23968 front-end of GNAT, and can be run independently (normally it is just
23969 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23970 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23971 @code{where} command is the first line of attack; the variable
23972 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23973 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23974 which the execution stopped, and @code{input_file name} indicates the name of
23978 @node Naming Conventions for GNAT Source Files
23979 @section Naming Conventions for GNAT Source Files
23982 In order to examine the workings of the GNAT system, the following
23983 brief description of its organization may be helpful:
23987 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23990 All files prefixed with @file{^par^PAR^} are components of the parser. The
23991 numbers correspond to chapters of the Ada Reference Manual. For example,
23992 parsing of select statements can be found in @file{par-ch9.adb}.
23995 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23996 numbers correspond to chapters of the Ada standard. For example, all
23997 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23998 addition, some features of the language require sufficient special processing
23999 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
24000 dynamic dispatching, etc.
24003 All files prefixed with @file{^exp^EXP^} perform normalization and
24004 expansion of the intermediate representation (abstract syntax tree, or AST).
24005 these files use the same numbering scheme as the parser and semantics files.
24006 For example, the construction of record initialization procedures is done in
24007 @file{exp_ch3.adb}.
24010 The files prefixed with @file{^bind^BIND^} implement the binder, which
24011 verifies the consistency of the compilation, determines an order of
24012 elaboration, and generates the bind file.
24015 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24016 data structures used by the front-end.
24019 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24020 the abstract syntax tree as produced by the parser.
24023 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24024 all entities, computed during semantic analysis.
24027 Library management issues are dealt with in files with prefix
24033 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24034 defined in Annex A.
24039 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24040 defined in Annex B.
24044 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24045 both language-defined children and GNAT run-time routines.
24049 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24050 general-purpose packages, fully documented in their specs. All
24051 the other @file{.c} files are modifications of common @command{gcc} files.
24054 @node Getting Internal Debugging Information
24055 @section Getting Internal Debugging Information
24058 Most compilers have internal debugging switches and modes. GNAT
24059 does also, except GNAT internal debugging switches and modes are not
24060 secret. A summary and full description of all the compiler and binder
24061 debug flags are in the file @file{debug.adb}. You must obtain the
24062 sources of the compiler to see the full detailed effects of these flags.
24064 The switches that print the source of the program (reconstructed from
24065 the internal tree) are of general interest for user programs, as are the
24067 the full internal tree, and the entity table (the symbol table
24068 information). The reconstructed source provides a readable version of the
24069 program after the front-end has completed analysis and expansion,
24070 and is useful when studying the performance of specific constructs.
24071 For example, constraint checks are indicated, complex aggregates
24072 are replaced with loops and assignments, and tasking primitives
24073 are replaced with run-time calls.
24075 @node Stack Traceback
24076 @section Stack Traceback
24078 @cindex stack traceback
24079 @cindex stack unwinding
24082 Traceback is a mechanism to display the sequence of subprogram calls that
24083 leads to a specified execution point in a program. Often (but not always)
24084 the execution point is an instruction at which an exception has been raised.
24085 This mechanism is also known as @i{stack unwinding} because it obtains
24086 its information by scanning the run-time stack and recovering the activation
24087 records of all active subprograms. Stack unwinding is one of the most
24088 important tools for program debugging.
24090 The first entry stored in traceback corresponds to the deepest calling level,
24091 that is to say the subprogram currently executing the instruction
24092 from which we want to obtain the traceback.
24094 Note that there is no runtime performance penalty when stack traceback
24095 is enabled, and no exception is raised during program execution.
24098 * Non-Symbolic Traceback::
24099 * Symbolic Traceback::
24102 @node Non-Symbolic Traceback
24103 @subsection Non-Symbolic Traceback
24104 @cindex traceback, non-symbolic
24107 Note: this feature is not supported on all platforms. See
24108 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24112 * Tracebacks From an Unhandled Exception::
24113 * Tracebacks From Exception Occurrences (non-symbolic)::
24114 * Tracebacks From Anywhere in a Program (non-symbolic)::
24117 @node Tracebacks From an Unhandled Exception
24118 @subsubsection Tracebacks From an Unhandled Exception
24121 A runtime non-symbolic traceback is a list of addresses of call instructions.
24122 To enable this feature you must use the @option{-E}
24123 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24124 of exception information. You can retrieve this information using the
24125 @code{addr2line} tool.
24127 Here is a simple example:
24129 @smallexample @c ada
24135 raise Constraint_Error;
24150 $ gnatmake stb -bargs -E
24153 Execution terminated by unhandled exception
24154 Exception name: CONSTRAINT_ERROR
24156 Call stack traceback locations:
24157 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24161 As we see the traceback lists a sequence of addresses for the unhandled
24162 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24163 guess that this exception come from procedure P1. To translate these
24164 addresses into the source lines where the calls appear, the
24165 @code{addr2line} tool, described below, is invaluable. The use of this tool
24166 requires the program to be compiled with debug information.
24169 $ gnatmake -g stb -bargs -E
24172 Execution terminated by unhandled exception
24173 Exception name: CONSTRAINT_ERROR
24175 Call stack traceback locations:
24176 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24178 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24179 0x4011f1 0x77e892a4
24181 00401373 at d:/stb/stb.adb:5
24182 0040138B at d:/stb/stb.adb:10
24183 0040139C at d:/stb/stb.adb:14
24184 00401335 at d:/stb/b~stb.adb:104
24185 004011C4 at /build/@dots{}/crt1.c:200
24186 004011F1 at /build/@dots{}/crt1.c:222
24187 77E892A4 in ?? at ??:0
24191 The @code{addr2line} tool has several other useful options:
24195 to get the function name corresponding to any location
24197 @item --demangle=gnat
24198 to use the gnat decoding mode for the function names. Note that
24199 for binutils version 2.9.x the option is simply @option{--demangle}.
24203 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24204 0x40139c 0x401335 0x4011c4 0x4011f1
24206 00401373 in stb.p1 at d:/stb/stb.adb:5
24207 0040138B in stb.p2 at d:/stb/stb.adb:10
24208 0040139C in stb at d:/stb/stb.adb:14
24209 00401335 in main at d:/stb/b~stb.adb:104
24210 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24211 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24215 From this traceback we can see that the exception was raised in
24216 @file{stb.adb} at line 5, which was reached from a procedure call in
24217 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24218 which contains the call to the main program.
24219 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24220 and the output will vary from platform to platform.
24222 It is also possible to use @code{GDB} with these traceback addresses to debug
24223 the program. For example, we can break at a given code location, as reported
24224 in the stack traceback:
24230 Furthermore, this feature is not implemented inside Windows DLL. Only
24231 the non-symbolic traceback is reported in this case.
24234 (gdb) break *0x401373
24235 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24239 It is important to note that the stack traceback addresses
24240 do not change when debug information is included. This is particularly useful
24241 because it makes it possible to release software without debug information (to
24242 minimize object size), get a field report that includes a stack traceback
24243 whenever an internal bug occurs, and then be able to retrieve the sequence
24244 of calls with the same program compiled with debug information.
24246 @node Tracebacks From Exception Occurrences (non-symbolic)
24247 @subsubsection Tracebacks From Exception Occurrences
24250 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24251 The stack traceback is attached to the exception information string, and can
24252 be retrieved in an exception handler within the Ada program, by means of the
24253 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24255 @smallexample @c ada
24257 with Ada.Exceptions;
24262 use Ada.Exceptions;
24270 Text_IO.Put_Line (Exception_Information (E));
24284 This program will output:
24289 Exception name: CONSTRAINT_ERROR
24290 Message: stb.adb:12
24291 Call stack traceback locations:
24292 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24295 @node Tracebacks From Anywhere in a Program (non-symbolic)
24296 @subsubsection Tracebacks From Anywhere in a Program
24299 It is also possible to retrieve a stack traceback from anywhere in a
24300 program. For this you need to
24301 use the @code{GNAT.Traceback} API. This package includes a procedure called
24302 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24303 display procedures described below. It is not necessary to use the
24304 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24305 is invoked explicitly.
24308 In the following example we compute a traceback at a specific location in
24309 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24310 convert addresses to strings:
24312 @smallexample @c ada
24314 with GNAT.Traceback;
24315 with GNAT.Debug_Utilities;
24321 use GNAT.Traceback;
24324 TB : Tracebacks_Array (1 .. 10);
24325 -- We are asking for a maximum of 10 stack frames.
24327 -- Len will receive the actual number of stack frames returned.
24329 Call_Chain (TB, Len);
24331 Text_IO.Put ("In STB.P1 : ");
24333 for K in 1 .. Len loop
24334 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24355 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24356 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24360 You can then get further information by invoking the @code{addr2line}
24361 tool as described earlier (note that the hexadecimal addresses
24362 need to be specified in C format, with a leading ``0x'').
24364 @node Symbolic Traceback
24365 @subsection Symbolic Traceback
24366 @cindex traceback, symbolic
24369 A symbolic traceback is a stack traceback in which procedure names are
24370 associated with each code location.
24373 Note that this feature is not supported on all platforms. See
24374 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24375 list of currently supported platforms.
24378 Note that the symbolic traceback requires that the program be compiled
24379 with debug information. If it is not compiled with debug information
24380 only the non-symbolic information will be valid.
24383 * Tracebacks From Exception Occurrences (symbolic)::
24384 * Tracebacks From Anywhere in a Program (symbolic)::
24387 @node Tracebacks From Exception Occurrences (symbolic)
24388 @subsubsection Tracebacks From Exception Occurrences
24390 @smallexample @c ada
24392 with GNAT.Traceback.Symbolic;
24398 raise Constraint_Error;
24415 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24420 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24423 0040149F in stb.p1 at stb.adb:8
24424 004014B7 in stb.p2 at stb.adb:13
24425 004014CF in stb.p3 at stb.adb:18
24426 004015DD in ada.stb at stb.adb:22
24427 00401461 in main at b~stb.adb:168
24428 004011C4 in __mingw_CRTStartup at crt1.c:200
24429 004011F1 in mainCRTStartup at crt1.c:222
24430 77E892A4 in ?? at ??:0
24434 In the above example the ``.\'' syntax in the @command{gnatmake} command
24435 is currently required by @command{addr2line} for files that are in
24436 the current working directory.
24437 Moreover, the exact sequence of linker options may vary from platform
24439 The above @option{-largs} section is for Windows platforms. By contrast,
24440 under Unix there is no need for the @option{-largs} section.
24441 Differences across platforms are due to details of linker implementation.
24443 @node Tracebacks From Anywhere in a Program (symbolic)
24444 @subsubsection Tracebacks From Anywhere in a Program
24447 It is possible to get a symbolic stack traceback
24448 from anywhere in a program, just as for non-symbolic tracebacks.
24449 The first step is to obtain a non-symbolic
24450 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24451 information. Here is an example:
24453 @smallexample @c ada
24455 with GNAT.Traceback;
24456 with GNAT.Traceback.Symbolic;
24461 use GNAT.Traceback;
24462 use GNAT.Traceback.Symbolic;
24465 TB : Tracebacks_Array (1 .. 10);
24466 -- We are asking for a maximum of 10 stack frames.
24468 -- Len will receive the actual number of stack frames returned.
24470 Call_Chain (TB, Len);
24471 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24484 @c ******************************
24486 @node Compatibility with HP Ada
24487 @chapter Compatibility with HP Ada
24488 @cindex Compatibility
24493 @cindex Compatibility between GNAT and HP Ada
24494 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24495 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24496 GNAT is highly compatible
24497 with HP Ada, and it should generally be straightforward to port code
24498 from the HP Ada environment to GNAT. However, there are a few language
24499 and implementation differences of which the user must be aware. These
24500 differences are discussed in this chapter. In
24501 addition, the operating environment and command structure for the
24502 compiler are different, and these differences are also discussed.
24504 For further details on these and other compatibility issues,
24505 see Appendix E of the HP publication
24506 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24508 Except where otherwise indicated, the description of GNAT for OpenVMS
24509 applies to both the Alpha and I64 platforms.
24511 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24512 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24514 The discussion in this chapter addresses specifically the implementation
24515 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24516 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24517 GNAT always follows the Alpha implementation.
24519 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24520 attributes are recognized, although only a subset of them can sensibly
24521 be implemented. The description of pragmas in
24522 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24523 indicates whether or not they are applicable to non-VMS systems.
24526 * Ada Language Compatibility::
24527 * Differences in the Definition of Package System::
24528 * Language-Related Features::
24529 * The Package STANDARD::
24530 * The Package SYSTEM::
24531 * Tasking and Task-Related Features::
24532 * Pragmas and Pragma-Related Features::
24533 * Library of Predefined Units::
24535 * Main Program Definition::
24536 * Implementation-Defined Attributes::
24537 * Compiler and Run-Time Interfacing::
24538 * Program Compilation and Library Management::
24540 * Implementation Limits::
24541 * Tools and Utilities::
24544 @node Ada Language Compatibility
24545 @section Ada Language Compatibility
24548 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24549 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24550 with Ada 83, and therefore Ada 83 programs will compile
24551 and run under GNAT with
24552 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24553 provides details on specific incompatibilities.
24555 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24556 as well as the pragma @code{ADA_83}, to force the compiler to
24557 operate in Ada 83 mode. This mode does not guarantee complete
24558 conformance to Ada 83, but in practice is sufficient to
24559 eliminate most sources of incompatibilities.
24560 In particular, it eliminates the recognition of the
24561 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24562 in Ada 83 programs is legal, and handles the cases of packages
24563 with optional bodies, and generics that instantiate unconstrained
24564 types without the use of @code{(<>)}.
24566 @node Differences in the Definition of Package System
24567 @section Differences in the Definition of Package @code{System}
24570 An Ada compiler is allowed to add
24571 implementation-dependent declarations to package @code{System}.
24573 GNAT does not take advantage of this permission, and the version of
24574 @code{System} provided by GNAT exactly matches that defined in the Ada
24577 However, HP Ada adds an extensive set of declarations to package
24579 as fully documented in the HP Ada manuals. To minimize changes required
24580 for programs that make use of these extensions, GNAT provides the pragma
24581 @code{Extend_System} for extending the definition of package System. By using:
24582 @cindex pragma @code{Extend_System}
24583 @cindex @code{Extend_System} pragma
24585 @smallexample @c ada
24588 pragma Extend_System (Aux_DEC);
24594 the set of definitions in @code{System} is extended to include those in
24595 package @code{System.Aux_DEC}.
24596 @cindex @code{System.Aux_DEC} package
24597 @cindex @code{Aux_DEC} package (child of @code{System})
24598 These definitions are incorporated directly into package @code{System},
24599 as though they had been declared there. For a
24600 list of the declarations added, see the spec of this package,
24601 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24602 @cindex @file{s-auxdec.ads} file
24603 The pragma @code{Extend_System} is a configuration pragma, which means that
24604 it can be placed in the file @file{gnat.adc}, so that it will automatically
24605 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24606 for further details.
24608 An alternative approach that avoids the use of the non-standard
24609 @code{Extend_System} pragma is to add a context clause to the unit that
24610 references these facilities:
24612 @smallexample @c ada
24614 with System.Aux_DEC;
24615 use System.Aux_DEC;
24620 The effect is not quite semantically identical to incorporating
24621 the declarations directly into package @code{System},
24622 but most programs will not notice a difference
24623 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24624 to reference the entities directly in package @code{System}.
24625 For units containing such references,
24626 the prefixes must either be removed, or the pragma @code{Extend_System}
24629 @node Language-Related Features
24630 @section Language-Related Features
24633 The following sections highlight differences in types,
24634 representations of types, operations, alignment, and
24638 * Integer Types and Representations::
24639 * Floating-Point Types and Representations::
24640 * Pragmas Float_Representation and Long_Float::
24641 * Fixed-Point Types and Representations::
24642 * Record and Array Component Alignment::
24643 * Address Clauses::
24644 * Other Representation Clauses::
24647 @node Integer Types and Representations
24648 @subsection Integer Types and Representations
24651 The set of predefined integer types is identical in HP Ada and GNAT.
24652 Furthermore the representation of these integer types is also identical,
24653 including the capability of size clauses forcing biased representation.
24656 HP Ada for OpenVMS Alpha systems has defined the
24657 following additional integer types in package @code{System}:
24674 @code{LARGEST_INTEGER}
24678 In GNAT, the first four of these types may be obtained from the
24679 standard Ada package @code{Interfaces}.
24680 Alternatively, by use of the pragma @code{Extend_System}, identical
24681 declarations can be referenced directly in package @code{System}.
24682 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24684 @node Floating-Point Types and Representations
24685 @subsection Floating-Point Types and Representations
24686 @cindex Floating-Point types
24689 The set of predefined floating-point types is identical in HP Ada and GNAT.
24690 Furthermore the representation of these floating-point
24691 types is also identical. One important difference is that the default
24692 representation for HP Ada is @code{VAX_Float}, but the default representation
24695 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24696 pragma @code{Float_Representation} as described in the HP Ada
24698 For example, the declarations:
24700 @smallexample @c ada
24702 type F_Float is digits 6;
24703 pragma Float_Representation (VAX_Float, F_Float);
24708 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24710 This set of declarations actually appears in @code{System.Aux_DEC},
24712 the full set of additional floating-point declarations provided in
24713 the HP Ada version of package @code{System}.
24714 This and similar declarations may be accessed in a user program
24715 by using pragma @code{Extend_System}. The use of this
24716 pragma, and the related pragma @code{Long_Float} is described in further
24717 detail in the following section.
24719 @node Pragmas Float_Representation and Long_Float
24720 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24723 HP Ada provides the pragma @code{Float_Representation}, which
24724 acts as a program library switch to allow control over
24725 the internal representation chosen for the predefined
24726 floating-point types declared in the package @code{Standard}.
24727 The format of this pragma is as follows:
24729 @smallexample @c ada
24731 pragma Float_Representation(VAX_Float | IEEE_Float);
24736 This pragma controls the representation of floating-point
24741 @code{VAX_Float} specifies that floating-point
24742 types are represented by default with the VAX system hardware types
24743 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24744 Note that the @code{H-floating}
24745 type was available only on VAX systems, and is not available
24746 in either HP Ada or GNAT.
24749 @code{IEEE_Float} specifies that floating-point
24750 types are represented by default with the IEEE single and
24751 double floating-point types.
24755 GNAT provides an identical implementation of the pragma
24756 @code{Float_Representation}, except that it functions as a
24757 configuration pragma. Note that the
24758 notion of configuration pragma corresponds closely to the
24759 HP Ada notion of a program library switch.
24761 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24763 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24764 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24765 advisable to change the format of numbers passed to standard library
24766 routines, and if necessary explicit type conversions may be needed.
24768 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24769 efficient, and (given that it conforms to an international standard)
24770 potentially more portable.
24771 The situation in which @code{VAX_Float} may be useful is in interfacing
24772 to existing code and data that expect the use of @code{VAX_Float}.
24773 In such a situation use the predefined @code{VAX_Float}
24774 types in package @code{System}, as extended by
24775 @code{Extend_System}. For example, use @code{System.F_Float}
24776 to specify the 32-bit @code{F-Float} format.
24779 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24780 to allow control over the internal representation chosen
24781 for the predefined type @code{Long_Float} and for floating-point
24782 type declarations with digits specified in the range 7 .. 15.
24783 The format of this pragma is as follows:
24785 @smallexample @c ada
24787 pragma Long_Float (D_FLOAT | G_FLOAT);
24791 @node Fixed-Point Types and Representations
24792 @subsection Fixed-Point Types and Representations
24795 On HP Ada for OpenVMS Alpha systems, rounding is
24796 away from zero for both positive and negative numbers.
24797 Therefore, @code{+0.5} rounds to @code{1},
24798 and @code{-0.5} rounds to @code{-1}.
24800 On GNAT the results of operations
24801 on fixed-point types are in accordance with the Ada
24802 rules. In particular, results of operations on decimal
24803 fixed-point types are truncated.
24805 @node Record and Array Component Alignment
24806 @subsection Record and Array Component Alignment
24809 On HP Ada for OpenVMS Alpha, all non-composite components
24810 are aligned on natural boundaries. For example, 1-byte
24811 components are aligned on byte boundaries, 2-byte
24812 components on 2-byte boundaries, 4-byte components on 4-byte
24813 byte boundaries, and so on. The OpenVMS Alpha hardware
24814 runs more efficiently with naturally aligned data.
24816 On GNAT, alignment rules are compatible
24817 with HP Ada for OpenVMS Alpha.
24819 @node Address Clauses
24820 @subsection Address Clauses
24823 In HP Ada and GNAT, address clauses are supported for
24824 objects and imported subprograms.
24825 The predefined type @code{System.Address} is a private type
24826 in both compilers on Alpha OpenVMS, with the same representation
24827 (it is simply a machine pointer). Addition, subtraction, and comparison
24828 operations are available in the standard Ada package
24829 @code{System.Storage_Elements}, or in package @code{System}
24830 if it is extended to include @code{System.Aux_DEC} using a
24831 pragma @code{Extend_System} as previously described.
24833 Note that code that @code{with}'s both this extended package @code{System}
24834 and the package @code{System.Storage_Elements} should not @code{use}
24835 both packages, or ambiguities will result. In general it is better
24836 not to mix these two sets of facilities. The Ada package was
24837 designed specifically to provide the kind of features that HP Ada
24838 adds directly to package @code{System}.
24840 The type @code{System.Address} is a 64-bit integer type in GNAT for
24841 I64 OpenVMS. For more information,
24842 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24844 GNAT is compatible with HP Ada in its handling of address
24845 clauses, except for some limitations in
24846 the form of address clauses for composite objects with
24847 initialization. Such address clauses are easily replaced
24848 by the use of an explicitly-defined constant as described
24849 in the Ada Reference Manual (13.1(22)). For example, the sequence
24852 @smallexample @c ada
24854 X, Y : Integer := Init_Func;
24855 Q : String (X .. Y) := "abc";
24857 for Q'Address use Compute_Address;
24862 will be rejected by GNAT, since the address cannot be computed at the time
24863 that @code{Q} is declared. To achieve the intended effect, write instead:
24865 @smallexample @c ada
24868 X, Y : Integer := Init_Func;
24869 Q_Address : constant Address := Compute_Address;
24870 Q : String (X .. Y) := "abc";
24872 for Q'Address use Q_Address;
24878 which will be accepted by GNAT (and other Ada compilers), and is also
24879 compatible with Ada 83. A fuller description of the restrictions
24880 on address specifications is found in @ref{Top, GNAT Reference Manual,
24881 About This Guide, gnat_rm, GNAT Reference Manual}.
24883 @node Other Representation Clauses
24884 @subsection Other Representation Clauses
24887 GNAT implements in a compatible manner all the representation
24888 clauses supported by HP Ada. In addition, GNAT
24889 implements the representation clause forms that were introduced in Ada 95,
24890 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24892 @node The Package STANDARD
24893 @section The Package @code{STANDARD}
24896 The package @code{STANDARD}, as implemented by HP Ada, is fully
24897 described in the @cite{Ada Reference Manual} and in the
24898 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24899 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24901 In addition, HP Ada supports the Latin-1 character set in
24902 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24903 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24904 the type @code{WIDE_CHARACTER}.
24906 The floating-point types supported by GNAT are those
24907 supported by HP Ada, but the defaults are different, and are controlled by
24908 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24910 @node The Package SYSTEM
24911 @section The Package @code{SYSTEM}
24914 HP Ada provides a specific version of the package
24915 @code{SYSTEM} for each platform on which the language is implemented.
24916 For the complete spec of the package @code{SYSTEM}, see
24917 Appendix F of the @cite{HP Ada Language Reference Manual}.
24919 On HP Ada, the package @code{SYSTEM} includes the following conversion
24922 @item @code{TO_ADDRESS(INTEGER)}
24924 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24926 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24928 @item @code{TO_INTEGER(ADDRESS)}
24930 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24932 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24933 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24937 By default, GNAT supplies a version of @code{SYSTEM} that matches
24938 the definition given in the @cite{Ada Reference Manual}.
24940 is a subset of the HP system definitions, which is as
24941 close as possible to the original definitions. The only difference
24942 is that the definition of @code{SYSTEM_NAME} is different:
24944 @smallexample @c ada
24946 type Name is (SYSTEM_NAME_GNAT);
24947 System_Name : constant Name := SYSTEM_NAME_GNAT;
24952 Also, GNAT adds the Ada declarations for
24953 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24955 However, the use of the following pragma causes GNAT
24956 to extend the definition of package @code{SYSTEM} so that it
24957 encompasses the full set of HP-specific extensions,
24958 including the functions listed above:
24960 @smallexample @c ada
24962 pragma Extend_System (Aux_DEC);
24967 The pragma @code{Extend_System} is a configuration pragma that
24968 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24969 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24971 HP Ada does not allow the recompilation of the package
24972 @code{SYSTEM}. Instead HP Ada provides several pragmas
24973 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24974 to modify values in the package @code{SYSTEM}.
24975 On OpenVMS Alpha systems, the pragma
24976 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24977 its single argument.
24979 GNAT does permit the recompilation of package @code{SYSTEM} using
24980 the special switch @option{-gnatg}, and this switch can be used if
24981 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24982 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24983 or @code{MEMORY_SIZE} by any other means.
24985 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24986 enumeration literal @code{SYSTEM_NAME_GNAT}.
24988 The definitions provided by the use of
24990 @smallexample @c ada
24991 pragma Extend_System (AUX_Dec);
24995 are virtually identical to those provided by the HP Ada 83 package
24996 @code{SYSTEM}. One important difference is that the name of the
24998 function for type @code{UNSIGNED_LONGWORD} is changed to
24999 @code{TO_ADDRESS_LONG}.
25000 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
25001 discussion of why this change was necessary.
25004 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
25006 an extension to Ada 83 not strictly compatible with the reference manual.
25007 GNAT, in order to be exactly compatible with the standard,
25008 does not provide this capability. In HP Ada 83, the
25009 point of this definition is to deal with a call like:
25011 @smallexample @c ada
25012 TO_ADDRESS (16#12777#);
25016 Normally, according to Ada 83 semantics, one would expect this to be
25017 ambiguous, since it matches both the @code{INTEGER} and
25018 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25019 However, in HP Ada 83, there is no ambiguity, since the
25020 definition using @i{universal_integer} takes precedence.
25022 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25024 not possible to be 100% compatible. Since there are many programs using
25025 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25027 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25028 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25030 @smallexample @c ada
25031 function To_Address (X : Integer) return Address;
25032 pragma Pure_Function (To_Address);
25034 function To_Address_Long (X : Unsigned_Longword) return Address;
25035 pragma Pure_Function (To_Address_Long);
25039 This means that programs using @code{TO_ADDRESS} for
25040 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25042 @node Tasking and Task-Related Features
25043 @section Tasking and Task-Related Features
25046 This section compares the treatment of tasking in GNAT
25047 and in HP Ada for OpenVMS Alpha.
25048 The GNAT description applies to both Alpha and I64 OpenVMS.
25049 For detailed information on tasking in
25050 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25051 relevant run-time reference manual.
25054 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25055 * Assigning Task IDs::
25056 * Task IDs and Delays::
25057 * Task-Related Pragmas::
25058 * Scheduling and Task Priority::
25060 * External Interrupts::
25063 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25064 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25067 On OpenVMS Alpha systems, each Ada task (except a passive
25068 task) is implemented as a single stream of execution
25069 that is created and managed by the kernel. On these
25070 systems, HP Ada tasking support is based on DECthreads,
25071 an implementation of the POSIX standard for threads.
25073 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25074 code that calls DECthreads routines can be used together.
25075 The interaction between Ada tasks and DECthreads routines
25076 can have some benefits. For example when on OpenVMS Alpha,
25077 HP Ada can call C code that is already threaded.
25079 GNAT uses the facilities of DECthreads,
25080 and Ada tasks are mapped to threads.
25082 @node Assigning Task IDs
25083 @subsection Assigning Task IDs
25086 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25087 the environment task that executes the main program. On
25088 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25089 that have been created but are not yet activated.
25091 On OpenVMS Alpha systems, task IDs are assigned at
25092 activation. On GNAT systems, task IDs are also assigned at
25093 task creation but do not have the same form or values as
25094 task ID values in HP Ada. There is no null task, and the
25095 environment task does not have a specific task ID value.
25097 @node Task IDs and Delays
25098 @subsection Task IDs and Delays
25101 On OpenVMS Alpha systems, tasking delays are implemented
25102 using Timer System Services. The Task ID is used for the
25103 identification of the timer request (the @code{REQIDT} parameter).
25104 If Timers are used in the application take care not to use
25105 @code{0} for the identification, because cancelling such a timer
25106 will cancel all timers and may lead to unpredictable results.
25108 @node Task-Related Pragmas
25109 @subsection Task-Related Pragmas
25112 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25113 specification of the size of the guard area for a task
25114 stack. (The guard area forms an area of memory that has no
25115 read or write access and thus helps in the detection of
25116 stack overflow.) On OpenVMS Alpha systems, if the pragma
25117 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25118 area is created. In the absence of a pragma @code{TASK_STORAGE},
25119 a default guard area is created.
25121 GNAT supplies the following task-related pragmas:
25124 @item @code{TASK_INFO}
25126 This pragma appears within a task definition and
25127 applies to the task in which it appears. The argument
25128 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25130 @item @code{TASK_STORAGE}
25132 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25133 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25134 @code{SUPPRESS}, and @code{VOLATILE}.
25136 @node Scheduling and Task Priority
25137 @subsection Scheduling and Task Priority
25140 HP Ada implements the Ada language requirement that
25141 when two tasks are eligible for execution and they have
25142 different priorities, the lower priority task does not
25143 execute while the higher priority task is waiting. The HP
25144 Ada Run-Time Library keeps a task running until either the
25145 task is suspended or a higher priority task becomes ready.
25147 On OpenVMS Alpha systems, the default strategy is round-
25148 robin with preemption. Tasks of equal priority take turns
25149 at the processor. A task is run for a certain period of
25150 time and then placed at the tail of the ready queue for
25151 its priority level.
25153 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25154 which can be used to enable or disable round-robin
25155 scheduling of tasks with the same priority.
25156 See the relevant HP Ada run-time reference manual for
25157 information on using the pragmas to control HP Ada task
25160 GNAT follows the scheduling rules of Annex D (Real-Time
25161 Annex) of the @cite{Ada Reference Manual}. In general, this
25162 scheduling strategy is fully compatible with HP Ada
25163 although it provides some additional constraints (as
25164 fully documented in Annex D).
25165 GNAT implements time slicing control in a manner compatible with
25166 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25167 are identical to the HP Ada 83 pragma of the same name.
25168 Note that it is not possible to mix GNAT tasking and
25169 HP Ada 83 tasking in the same program, since the two run-time
25170 libraries are not compatible.
25172 @node The Task Stack
25173 @subsection The Task Stack
25176 In HP Ada, a task stack is allocated each time a
25177 non-passive task is activated. As soon as the task is
25178 terminated, the storage for the task stack is deallocated.
25179 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25180 a default stack size is used. Also, regardless of the size
25181 specified, some additional space is allocated for task
25182 management purposes. On OpenVMS Alpha systems, at least
25183 one page is allocated.
25185 GNAT handles task stacks in a similar manner. In accordance with
25186 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25187 an alternative method for controlling the task stack size.
25188 The specification of the attribute @code{T'STORAGE_SIZE} is also
25189 supported in a manner compatible with HP Ada.
25191 @node External Interrupts
25192 @subsection External Interrupts
25195 On HP Ada, external interrupts can be associated with task entries.
25196 GNAT is compatible with HP Ada in its handling of external interrupts.
25198 @node Pragmas and Pragma-Related Features
25199 @section Pragmas and Pragma-Related Features
25202 Both HP Ada and GNAT supply all language-defined pragmas
25203 as specified by the Ada 83 standard. GNAT also supplies all
25204 language-defined pragmas introduced by Ada 95 and Ada 2005.
25205 In addition, GNAT implements the implementation-defined pragmas
25209 @item @code{AST_ENTRY}
25211 @item @code{COMMON_OBJECT}
25213 @item @code{COMPONENT_ALIGNMENT}
25215 @item @code{EXPORT_EXCEPTION}
25217 @item @code{EXPORT_FUNCTION}
25219 @item @code{EXPORT_OBJECT}
25221 @item @code{EXPORT_PROCEDURE}
25223 @item @code{EXPORT_VALUED_PROCEDURE}
25225 @item @code{FLOAT_REPRESENTATION}
25229 @item @code{IMPORT_EXCEPTION}
25231 @item @code{IMPORT_FUNCTION}
25233 @item @code{IMPORT_OBJECT}
25235 @item @code{IMPORT_PROCEDURE}
25237 @item @code{IMPORT_VALUED_PROCEDURE}
25239 @item @code{INLINE_GENERIC}
25241 @item @code{INTERFACE_NAME}
25243 @item @code{LONG_FLOAT}
25245 @item @code{MAIN_STORAGE}
25247 @item @code{PASSIVE}
25249 @item @code{PSECT_OBJECT}
25251 @item @code{SHARE_GENERIC}
25253 @item @code{SUPPRESS_ALL}
25255 @item @code{TASK_STORAGE}
25257 @item @code{TIME_SLICE}
25263 These pragmas are all fully implemented, with the exception of @code{TITLE},
25264 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25265 recognized, but which have no
25266 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25267 use of Ada protected objects. In GNAT, all generics are inlined.
25269 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25270 a separate subprogram specification which must appear before the
25273 GNAT also supplies a number of implementation-defined pragmas as follows:
25275 @item @code{ABORT_DEFER}
25277 @item @code{ADA_83}
25279 @item @code{ADA_95}
25281 @item @code{ADA_05}
25283 @item @code{ANNOTATE}
25285 @item @code{ASSERT}
25287 @item @code{C_PASS_BY_COPY}
25289 @item @code{CPP_CLASS}
25291 @item @code{CPP_CONSTRUCTOR}
25293 @item @code{CPP_DESTRUCTOR}
25297 @item @code{EXTEND_SYSTEM}
25299 @item @code{LINKER_ALIAS}
25301 @item @code{LINKER_SECTION}
25303 @item @code{MACHINE_ATTRIBUTE}
25305 @item @code{NO_RETURN}
25307 @item @code{PURE_FUNCTION}
25309 @item @code{SOURCE_FILE_NAME}
25311 @item @code{SOURCE_REFERENCE}
25313 @item @code{TASK_INFO}
25315 @item @code{UNCHECKED_UNION}
25317 @item @code{UNIMPLEMENTED_UNIT}
25319 @item @code{UNIVERSAL_DATA}
25321 @item @code{UNSUPPRESS}
25323 @item @code{WARNINGS}
25325 @item @code{WEAK_EXTERNAL}
25329 For full details on these GNAT implementation-defined pragmas,
25330 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25334 * Restrictions on the Pragma INLINE::
25335 * Restrictions on the Pragma INTERFACE::
25336 * Restrictions on the Pragma SYSTEM_NAME::
25339 @node Restrictions on the Pragma INLINE
25340 @subsection Restrictions on Pragma @code{INLINE}
25343 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25345 @item Parameters cannot have a task type.
25347 @item Function results cannot be task types, unconstrained
25348 array types, or unconstrained types with discriminants.
25350 @item Bodies cannot declare the following:
25352 @item Subprogram body or stub (imported subprogram is allowed)
25356 @item Generic declarations
25358 @item Instantiations
25362 @item Access types (types derived from access types allowed)
25364 @item Array or record types
25366 @item Dependent tasks
25368 @item Direct recursive calls of subprogram or containing
25369 subprogram, directly or via a renaming
25375 In GNAT, the only restriction on pragma @code{INLINE} is that the
25376 body must occur before the call if both are in the same
25377 unit, and the size must be appropriately small. There are
25378 no other specific restrictions which cause subprograms to
25379 be incapable of being inlined.
25381 @node Restrictions on the Pragma INTERFACE
25382 @subsection Restrictions on Pragma @code{INTERFACE}
25385 The following restrictions on pragma @code{INTERFACE}
25386 are enforced by both HP Ada and GNAT:
25388 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25389 Default is the default on OpenVMS Alpha systems.
25391 @item Parameter passing: Language specifies default
25392 mechanisms but can be overridden with an @code{EXPORT} pragma.
25395 @item Ada: Use internal Ada rules.
25397 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25398 record or task type. Result cannot be a string, an
25399 array, or a record.
25401 @item Fortran: Parameters cannot have a task type. Result cannot
25402 be a string, an array, or a record.
25407 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25408 record parameters for all languages.
25410 @node Restrictions on the Pragma SYSTEM_NAME
25411 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25414 For HP Ada for OpenVMS Alpha, the enumeration literal
25415 for the type @code{NAME} is @code{OPENVMS_AXP}.
25416 In GNAT, the enumeration
25417 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25419 @node Library of Predefined Units
25420 @section Library of Predefined Units
25423 A library of predefined units is provided as part of the
25424 HP Ada and GNAT implementations. HP Ada does not provide
25425 the package @code{MACHINE_CODE} but instead recommends importing
25428 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25429 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25431 The HP Ada Predefined Library units are modified to remove post-Ada 83
25432 incompatibilities and to make them interoperable with GNAT
25433 (@pxref{Changes to DECLIB}, for details).
25434 The units are located in the @file{DECLIB} directory.
25436 The GNAT RTL is contained in
25437 the @file{ADALIB} directory, and
25438 the default search path is set up to find @code{DECLIB} units in preference
25439 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25440 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25443 * Changes to DECLIB::
25446 @node Changes to DECLIB
25447 @subsection Changes to @code{DECLIB}
25450 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25451 compatibility are minor and include the following:
25454 @item Adjusting the location of pragmas and record representation
25455 clauses to obey Ada 95 (and thus Ada 2005) rules
25457 @item Adding the proper notation to generic formal parameters
25458 that take unconstrained types in instantiation
25460 @item Adding pragma @code{ELABORATE_BODY} to package specs
25461 that have package bodies not otherwise allowed
25463 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25464 ``@code{PROTECTD}''.
25465 Currently these are found only in the @code{STARLET} package spec.
25467 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25468 where the address size is constrained to 32 bits.
25472 None of the above changes is visible to users.
25478 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25481 @item Command Language Interpreter (CLI interface)
25483 @item DECtalk Run-Time Library (DTK interface)
25485 @item Librarian utility routines (LBR interface)
25487 @item General Purpose Run-Time Library (LIB interface)
25489 @item Math Run-Time Library (MTH interface)
25491 @item National Character Set Run-Time Library (NCS interface)
25493 @item Compiled Code Support Run-Time Library (OTS interface)
25495 @item Parallel Processing Run-Time Library (PPL interface)
25497 @item Screen Management Run-Time Library (SMG interface)
25499 @item Sort Run-Time Library (SOR interface)
25501 @item String Run-Time Library (STR interface)
25503 @item STARLET System Library
25506 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25508 @item X Windows Toolkit (XT interface)
25510 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25514 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25515 directory, on both the Alpha and I64 OpenVMS platforms.
25517 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25519 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25520 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25521 @code{Xt}, and @code{X_Lib}
25522 causing the default X/Motif sharable image libraries to be linked in. This
25523 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25524 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25526 It may be necessary to edit these options files to update or correct the
25527 library names if, for example, the newer X/Motif bindings from
25528 @file{ADA$EXAMPLES}
25529 had been (previous to installing GNAT) copied and renamed to supersede the
25530 default @file{ADA$PREDEFINED} versions.
25533 * Shared Libraries and Options Files::
25534 * Interfaces to C::
25537 @node Shared Libraries and Options Files
25538 @subsection Shared Libraries and Options Files
25541 When using the HP Ada
25542 predefined X and Motif bindings, the linking with their sharable images is
25543 done automatically by @command{GNAT LINK}.
25544 When using other X and Motif bindings, you need
25545 to add the corresponding sharable images to the command line for
25546 @code{GNAT LINK}. When linking with shared libraries, or with
25547 @file{.OPT} files, you must
25548 also add them to the command line for @command{GNAT LINK}.
25550 A shared library to be used with GNAT is built in the same way as other
25551 libraries under VMS. The VMS Link command can be used in standard fashion.
25553 @node Interfaces to C
25554 @subsection Interfaces to C
25558 provides the following Ada types and operations:
25561 @item C types package (@code{C_TYPES})
25563 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25565 @item Other_types (@code{SHORT_INT})
25569 Interfacing to C with GNAT, you can use the above approach
25570 described for HP Ada or the facilities of Annex B of
25571 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25572 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25573 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25575 The @option{-gnatF} qualifier forces default and explicit
25576 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25577 to be uppercased for compatibility with the default behavior
25578 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25580 @node Main Program Definition
25581 @section Main Program Definition
25584 The following section discusses differences in the
25585 definition of main programs on HP Ada and GNAT.
25586 On HP Ada, main programs are defined to meet the
25587 following conditions:
25589 @item Procedure with no formal parameters (returns @code{0} upon
25592 @item Procedure with no formal parameters (returns @code{42} when
25593 an unhandled exception is raised)
25595 @item Function with no formal parameters whose returned value
25596 is of a discrete type
25598 @item Procedure with one @code{out} formal of a discrete type for
25599 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25604 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25605 a main function or main procedure returns a discrete
25606 value whose size is less than 64 bits (32 on VAX systems),
25607 the value is zero- or sign-extended as appropriate.
25608 On GNAT, main programs are defined as follows:
25610 @item Must be a non-generic, parameterless subprogram that
25611 is either a procedure or function returning an Ada
25612 @code{STANDARD.INTEGER} (the predefined type)
25614 @item Cannot be a generic subprogram or an instantiation of a
25618 @node Implementation-Defined Attributes
25619 @section Implementation-Defined Attributes
25622 GNAT provides all HP Ada implementation-defined
25625 @node Compiler and Run-Time Interfacing
25626 @section Compiler and Run-Time Interfacing
25629 HP Ada provides the following qualifiers to pass options to the linker
25632 @item @option{/WAIT} and @option{/SUBMIT}
25634 @item @option{/COMMAND}
25636 @item @option{/@r{[}NO@r{]}MAP}
25638 @item @option{/OUTPUT=@var{file-spec}}
25640 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25644 To pass options to the linker, GNAT provides the following
25648 @item @option{/EXECUTABLE=@var{exec-name}}
25650 @item @option{/VERBOSE}
25652 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25656 For more information on these switches, see
25657 @ref{Switches for gnatlink}.
25658 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25659 to control optimization. HP Ada also supplies the
25662 @item @code{OPTIMIZE}
25664 @item @code{INLINE}
25666 @item @code{INLINE_GENERIC}
25668 @item @code{SUPPRESS_ALL}
25670 @item @code{PASSIVE}
25674 In GNAT, optimization is controlled strictly by command
25675 line parameters, as described in the corresponding section of this guide.
25676 The HP pragmas for control of optimization are
25677 recognized but ignored.
25679 Note that in GNAT, the default is optimization off, whereas in HP Ada
25680 the default is that optimization is turned on.
25682 @node Program Compilation and Library Management
25683 @section Program Compilation and Library Management
25686 HP Ada and GNAT provide a comparable set of commands to
25687 build programs. HP Ada also provides a program library,
25688 which is a concept that does not exist on GNAT. Instead,
25689 GNAT provides directories of sources that are compiled as
25692 The following table summarizes
25693 the HP Ada commands and provides
25694 equivalent GNAT commands. In this table, some GNAT
25695 equivalents reflect the fact that GNAT does not use the
25696 concept of a program library. Instead, it uses a model
25697 in which collections of source and object files are used
25698 in a manner consistent with other languages like C and
25699 Fortran. Therefore, standard system file commands are used
25700 to manipulate these elements. Those GNAT commands are marked with
25702 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25705 @multitable @columnfractions .35 .65
25707 @item @emph{HP Ada Command}
25708 @tab @emph{GNAT Equivalent / Description}
25710 @item @command{ADA}
25711 @tab @command{GNAT COMPILE}@*
25712 Invokes the compiler to compile one or more Ada source files.
25714 @item @command{ACS ATTACH}@*
25715 @tab [No equivalent]@*
25716 Switches control of terminal from current process running the program
25719 @item @command{ACS CHECK}
25720 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25721 Forms the execution closure of one
25722 or more compiled units and checks completeness and currency.
25724 @item @command{ACS COMPILE}
25725 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25726 Forms the execution closure of one or
25727 more specified units, checks completeness and currency,
25728 identifies units that have revised source files, compiles same,
25729 and recompiles units that are or will become obsolete.
25730 Also completes incomplete generic instantiations.
25732 @item @command{ACS COPY FOREIGN}
25734 Copies a foreign object file into the program library as a
25737 @item @command{ACS COPY UNIT}
25739 Copies a compiled unit from one program library to another.
25741 @item @command{ACS CREATE LIBRARY}
25742 @tab Create /directory (*)@*
25743 Creates a program library.
25745 @item @command{ACS CREATE SUBLIBRARY}
25746 @tab Create /directory (*)@*
25747 Creates a program sublibrary.
25749 @item @command{ACS DELETE LIBRARY}
25751 Deletes a program library and its contents.
25753 @item @command{ACS DELETE SUBLIBRARY}
25755 Deletes a program sublibrary and its contents.
25757 @item @command{ACS DELETE UNIT}
25758 @tab Delete file (*)@*
25759 On OpenVMS systems, deletes one or more compiled units from
25760 the current program library.
25762 @item @command{ACS DIRECTORY}
25763 @tab Directory (*)@*
25764 On OpenVMS systems, lists units contained in the current
25767 @item @command{ACS ENTER FOREIGN}
25769 Allows the import of a foreign body as an Ada library
25770 spec and enters a reference to a pointer.
25772 @item @command{ACS ENTER UNIT}
25774 Enters a reference (pointer) from the current program library to
25775 a unit compiled into another program library.
25777 @item @command{ACS EXIT}
25778 @tab [No equivalent]@*
25779 Exits from the program library manager.
25781 @item @command{ACS EXPORT}
25783 Creates an object file that contains system-specific object code
25784 for one or more units. With GNAT, object files can simply be copied
25785 into the desired directory.
25787 @item @command{ACS EXTRACT SOURCE}
25789 Allows access to the copied source file for each Ada compilation unit
25791 @item @command{ACS HELP}
25792 @tab @command{HELP GNAT}@*
25793 Provides online help.
25795 @item @command{ACS LINK}
25796 @tab @command{GNAT LINK}@*
25797 Links an object file containing Ada units into an executable file.
25799 @item @command{ACS LOAD}
25801 Loads (partially compiles) Ada units into the program library.
25802 Allows loading a program from a collection of files into a library
25803 without knowing the relationship among units.
25805 @item @command{ACS MERGE}
25807 Merges into the current program library, one or more units from
25808 another library where they were modified.
25810 @item @command{ACS RECOMPILE}
25811 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25812 Recompiles from external or copied source files any obsolete
25813 unit in the closure. Also, completes any incomplete generic
25816 @item @command{ACS REENTER}
25817 @tab @command{GNAT MAKE}@*
25818 Reenters current references to units compiled after last entered
25819 with the @command{ACS ENTER UNIT} command.
25821 @item @command{ACS SET LIBRARY}
25822 @tab Set default (*)@*
25823 Defines a program library to be the compilation context as well
25824 as the target library for compiler output and commands in general.
25826 @item @command{ACS SET PRAGMA}
25827 @tab Edit @file{gnat.adc} (*)@*
25828 Redefines specified values of the library characteristics
25829 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25830 and @code{Float_Representation}.
25832 @item @command{ACS SET SOURCE}
25833 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25834 Defines the source file search list for the @command{ACS COMPILE} command.
25836 @item @command{ACS SHOW LIBRARY}
25837 @tab Directory (*)@*
25838 Lists information about one or more program libraries.
25840 @item @command{ACS SHOW PROGRAM}
25841 @tab [No equivalent]@*
25842 Lists information about the execution closure of one or
25843 more units in the program library.
25845 @item @command{ACS SHOW SOURCE}
25846 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25847 Shows the source file search used when compiling units.
25849 @item @command{ACS SHOW VERSION}
25850 @tab Compile with @option{VERBOSE} option
25851 Displays the version number of the compiler and program library
25854 @item @command{ACS SPAWN}
25855 @tab [No equivalent]@*
25856 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25859 @item @command{ACS VERIFY}
25860 @tab [No equivalent]@*
25861 Performs a series of consistency checks on a program library to
25862 determine whether the library structure and library files are in
25869 @section Input-Output
25872 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25873 Management Services (RMS) to perform operations on
25877 HP Ada and GNAT predefine an identical set of input-
25878 output packages. To make the use of the
25879 generic @code{TEXT_IO} operations more convenient, HP Ada
25880 provides predefined library packages that instantiate the
25881 integer and floating-point operations for the predefined
25882 integer and floating-point types as shown in the following table.
25884 @multitable @columnfractions .45 .55
25885 @item @emph{Package Name} @tab Instantiation
25887 @item @code{INTEGER_TEXT_IO}
25888 @tab @code{INTEGER_IO(INTEGER)}
25890 @item @code{SHORT_INTEGER_TEXT_IO}
25891 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25893 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25894 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25896 @item @code{FLOAT_TEXT_IO}
25897 @tab @code{FLOAT_IO(FLOAT)}
25899 @item @code{LONG_FLOAT_TEXT_IO}
25900 @tab @code{FLOAT_IO(LONG_FLOAT)}
25904 The HP Ada predefined packages and their operations
25905 are implemented using OpenVMS Alpha files and input-output
25906 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25907 Familiarity with the following is recommended:
25909 @item RMS file organizations and access methods
25911 @item OpenVMS file specifications and directories
25913 @item OpenVMS File Definition Language (FDL)
25917 GNAT provides I/O facilities that are completely
25918 compatible with HP Ada. The distribution includes the
25919 standard HP Ada versions of all I/O packages, operating
25920 in a manner compatible with HP Ada. In particular, the
25921 following packages are by default the HP Ada (Ada 83)
25922 versions of these packages rather than the renamings
25923 suggested in Annex J of the Ada Reference Manual:
25925 @item @code{TEXT_IO}
25927 @item @code{SEQUENTIAL_IO}
25929 @item @code{DIRECT_IO}
25933 The use of the standard child package syntax (for
25934 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25936 GNAT provides HP-compatible predefined instantiations
25937 of the @code{TEXT_IO} packages, and also
25938 provides the standard predefined instantiations required
25939 by the @cite{Ada Reference Manual}.
25941 For further information on how GNAT interfaces to the file
25942 system or how I/O is implemented in programs written in
25943 mixed languages, see @ref{Implementation of the Standard I/O,,,
25944 gnat_rm, GNAT Reference Manual}.
25945 This chapter covers the following:
25947 @item Standard I/O packages
25949 @item @code{FORM} strings
25951 @item @code{ADA.DIRECT_IO}
25953 @item @code{ADA.SEQUENTIAL_IO}
25955 @item @code{ADA.TEXT_IO}
25957 @item Stream pointer positioning
25959 @item Reading and writing non-regular files
25961 @item @code{GET_IMMEDIATE}
25963 @item Treating @code{TEXT_IO} files as streams
25970 @node Implementation Limits
25971 @section Implementation Limits
25974 The following table lists implementation limits for HP Ada
25976 @multitable @columnfractions .60 .20 .20
25978 @item @emph{Compilation Parameter}
25983 @item In a subprogram or entry declaration, maximum number of
25984 formal parameters that are of an unconstrained record type
25989 @item Maximum identifier length (number of characters)
25994 @item Maximum number of characters in a source line
25999 @item Maximum collection size (number of bytes)
26004 @item Maximum number of discriminants for a record type
26009 @item Maximum number of formal parameters in an entry or
26010 subprogram declaration
26015 @item Maximum number of dimensions in an array type
26020 @item Maximum number of library units and subunits in a compilation.
26025 @item Maximum number of library units and subunits in an execution.
26030 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26031 or @code{PSECT_OBJECT}
26036 @item Maximum number of enumeration literals in an enumeration type
26042 @item Maximum number of lines in a source file
26047 @item Maximum number of bits in any object
26052 @item Maximum size of the static portion of a stack frame (approximate)
26057 @node Tools and Utilities
26058 @section Tools and Utilities
26061 The following table lists some of the OpenVMS development tools
26062 available for HP Ada, and the corresponding tools for
26063 use with @value{EDITION} on Alpha and I64 platforms.
26064 Aside from the debugger, all the OpenVMS tools identified are part
26065 of the DECset package.
26068 @c Specify table in TeX since Texinfo does a poor job
26072 \settabs\+Language-Sensitive Editor\quad
26073 &Product with HP Ada\quad
26076 &\it Product with HP Ada
26077 & \it Product with GNAT Pro\cr
26079 \+Code Management System
26083 \+Language-Sensitive Editor
26085 & emacs or HP LSE (Alpha)\cr
26095 & OpenVMS Debug (I64)\cr
26097 \+Source Code Analyzer /
26114 \+Coverage Analyzer
26118 \+Module Management
26120 & Not applicable\cr
26130 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26131 @c the TeX version above for the printed version
26133 @c @multitable @columnfractions .3 .4 .4
26134 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26136 @tab @i{Tool with HP Ada}
26137 @tab @i{Tool with @value{EDITION}}
26138 @item Code Management@*System
26141 @item Language-Sensitive@*Editor
26143 @tab emacs or HP LSE (Alpha)
26152 @tab OpenVMS Debug (I64)
26153 @item Source Code Analyzer /@*Cross Referencer
26157 @tab HP Digital Test@*Manager (DTM)
26159 @item Performance and@*Coverage Analyzer
26162 @item Module Management@*System
26164 @tab Not applicable
26171 @c **************************************
26172 @node Platform-Specific Information for the Run-Time Libraries
26173 @appendix Platform-Specific Information for the Run-Time Libraries
26174 @cindex Tasking and threads libraries
26175 @cindex Threads libraries and tasking
26176 @cindex Run-time libraries (platform-specific information)
26179 The GNAT run-time implementation may vary with respect to both the
26180 underlying threads library and the exception handling scheme.
26181 For threads support, one or more of the following are supplied:
26183 @item @b{native threads library}, a binding to the thread package from
26184 the underlying operating system
26186 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26187 POSIX thread package
26191 For exception handling, either or both of two models are supplied:
26193 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26194 Most programs should experience a substantial speed improvement by
26195 being compiled with a ZCX run-time.
26196 This is especially true for
26197 tasking applications or applications with many exception handlers.}
26198 @cindex Zero-Cost Exceptions
26199 @cindex ZCX (Zero-Cost Exceptions)
26200 which uses binder-generated tables that
26201 are interrogated at run time to locate a handler
26203 @item @b{setjmp / longjmp} (``SJLJ''),
26204 @cindex setjmp/longjmp Exception Model
26205 @cindex SJLJ (setjmp/longjmp Exception Model)
26206 which uses dynamically-set data to establish
26207 the set of handlers
26211 This appendix summarizes which combinations of threads and exception support
26212 are supplied on various GNAT platforms.
26213 It then shows how to select a particular library either
26214 permanently or temporarily,
26215 explains the properties of (and tradeoffs among) the various threads
26216 libraries, and provides some additional
26217 information about several specific platforms.
26220 * Summary of Run-Time Configurations::
26221 * Specifying a Run-Time Library::
26222 * Choosing the Scheduling Policy::
26223 * Solaris-Specific Considerations::
26224 * Linux-Specific Considerations::
26225 * AIX-Specific Considerations::
26226 * Irix-Specific Considerations::
26227 * RTX-Specific Considerations::
26230 @node Summary of Run-Time Configurations
26231 @section Summary of Run-Time Configurations
26233 @multitable @columnfractions .30 .70
26234 @item @b{alpha-openvms}
26235 @item @code{@ @ }@i{rts-native (default)}
26236 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26237 @item @code{@ @ @ @ }Exceptions @tab ZCX
26239 @item @b{alpha-tru64}
26240 @item @code{@ @ }@i{rts-native (default)}
26241 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26242 @item @code{@ @ @ @ }Exceptions @tab ZCX
26244 @item @code{@ @ }@i{rts-sjlj}
26245 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26246 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26248 @item @b{ia64-hp_linux}
26249 @item @code{@ @ }@i{rts-native (default)}
26250 @item @code{@ @ @ @ }Tasking @tab pthread library
26251 @item @code{@ @ @ @ }Exceptions @tab ZCX
26253 @item @b{ia64-hpux}
26254 @item @code{@ @ }@i{rts-native (default)}
26255 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26256 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26258 @item @b{ia64-openvms}
26259 @item @code{@ @ }@i{rts-native (default)}
26260 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26261 @item @code{@ @ @ @ }Exceptions @tab ZCX
26263 @item @b{ia64-sgi_linux}
26264 @item @code{@ @ }@i{rts-native (default)}
26265 @item @code{@ @ @ @ }Tasking @tab pthread library
26266 @item @code{@ @ @ @ }Exceptions @tab ZCX
26268 @item @b{mips-irix}
26269 @item @code{@ @ }@i{rts-native (default)}
26270 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26271 @item @code{@ @ @ @ }Exceptions @tab ZCX
26274 @item @code{@ @ }@i{rts-native (default)}
26275 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26276 @item @code{@ @ @ @ }Exceptions @tab ZCX
26278 @item @code{@ @ }@i{rts-sjlj}
26279 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26280 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26283 @item @code{@ @ }@i{rts-native (default)}
26284 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26285 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26287 @item @b{ppc-darwin}
26288 @item @code{@ @ }@i{rts-native (default)}
26289 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26290 @item @code{@ @ @ @ }Exceptions @tab ZCX
26292 @item @b{sparc-solaris} @tab
26293 @item @code{@ @ }@i{rts-native (default)}
26294 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26295 @item @code{@ @ @ @ }Exceptions @tab ZCX
26297 @item @code{@ @ }@i{rts-pthread}
26298 @item @code{@ @ @ @ }Tasking @tab pthread library
26299 @item @code{@ @ @ @ }Exceptions @tab ZCX
26301 @item @code{@ @ }@i{rts-sjlj}
26302 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26303 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26305 @item @b{sparc64-solaris} @tab
26306 @item @code{@ @ }@i{rts-native (default)}
26307 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26308 @item @code{@ @ @ @ }Exceptions @tab ZCX
26310 @item @b{x86-linux}
26311 @item @code{@ @ }@i{rts-native (default)}
26312 @item @code{@ @ @ @ }Tasking @tab pthread library
26313 @item @code{@ @ @ @ }Exceptions @tab ZCX
26315 @item @code{@ @ }@i{rts-sjlj}
26316 @item @code{@ @ @ @ }Tasking @tab pthread library
26317 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26320 @item @code{@ @ }@i{rts-native (default)}
26321 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26322 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26324 @item @b{x86-solaris}
26325 @item @code{@ @ }@i{rts-native (default)}
26326 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26327 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26329 @item @b{x86-windows}
26330 @item @code{@ @ }@i{rts-native (default)}
26331 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26332 @item @code{@ @ @ @ }Exceptions @tab ZCX
26334 @item @code{@ @ }@i{rts-sjlj (default)}
26335 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26336 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26338 @item @b{x86-windows-rtx}
26339 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26340 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26341 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26343 @item @code{@ @ }@i{rts-rtx-w32}
26344 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26345 @item @code{@ @ @ @ }Exceptions @tab ZCX
26347 @item @b{x86_64-linux}
26348 @item @code{@ @ }@i{rts-native (default)}
26349 @item @code{@ @ @ @ }Tasking @tab pthread library
26350 @item @code{@ @ @ @ }Exceptions @tab ZCX
26352 @item @code{@ @ }@i{rts-sjlj}
26353 @item @code{@ @ @ @ }Tasking @tab pthread library
26354 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26358 @node Specifying a Run-Time Library
26359 @section Specifying a Run-Time Library
26362 The @file{adainclude} subdirectory containing the sources of the GNAT
26363 run-time library, and the @file{adalib} subdirectory containing the
26364 @file{ALI} files and the static and/or shared GNAT library, are located
26365 in the gcc target-dependent area:
26368 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26372 As indicated above, on some platforms several run-time libraries are supplied.
26373 These libraries are installed in the target dependent area and
26374 contain a complete source and binary subdirectory. The detailed description
26375 below explains the differences between the different libraries in terms of
26376 their thread support.
26378 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26379 This default run time is selected by the means of soft links.
26380 For example on x86-linux:
26386 +--- adainclude----------+
26388 +--- adalib-----------+ |
26390 +--- rts-native | |
26392 | +--- adainclude <---+
26394 | +--- adalib <----+
26405 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26406 these soft links can be modified with the following commands:
26410 $ rm -f adainclude adalib
26411 $ ln -s rts-sjlj/adainclude adainclude
26412 $ ln -s rts-sjlj/adalib adalib
26416 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26417 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26418 @file{$target/ada_object_path}.
26420 Selecting another run-time library temporarily can be
26421 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26422 @cindex @option{--RTS} option
26424 @node Choosing the Scheduling Policy
26425 @section Choosing the Scheduling Policy
26428 When using a POSIX threads implementation, you have a choice of several
26429 scheduling policies: @code{SCHED_FIFO},
26430 @cindex @code{SCHED_FIFO} scheduling policy
26432 @cindex @code{SCHED_RR} scheduling policy
26433 and @code{SCHED_OTHER}.
26434 @cindex @code{SCHED_OTHER} scheduling policy
26435 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26436 or @code{SCHED_RR} requires special (e.g., root) privileges.
26438 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26440 @cindex @code{SCHED_FIFO} scheduling policy
26441 you can use one of the following:
26445 @code{pragma Time_Slice (0.0)}
26446 @cindex pragma Time_Slice
26448 the corresponding binder option @option{-T0}
26449 @cindex @option{-T0} option
26451 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26452 @cindex pragma Task_Dispatching_Policy
26456 To specify @code{SCHED_RR},
26457 @cindex @code{SCHED_RR} scheduling policy
26458 you should use @code{pragma Time_Slice} with a
26459 value greater than @code{0.0}, or else use the corresponding @option{-T}
26462 @node Solaris-Specific Considerations
26463 @section Solaris-Specific Considerations
26464 @cindex Solaris Sparc threads libraries
26467 This section addresses some topics related to the various threads libraries
26471 * Solaris Threads Issues::
26474 @node Solaris Threads Issues
26475 @subsection Solaris Threads Issues
26478 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26479 library based on POSIX threads --- @emph{rts-pthread}.
26480 @cindex rts-pthread threads library
26481 This run-time library has the advantage of being mostly shared across all
26482 POSIX-compliant thread implementations, and it also provides under
26483 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26484 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26485 and @code{PTHREAD_PRIO_PROTECT}
26486 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26487 semantics that can be selected using the predefined pragma
26488 @code{Locking_Policy}
26489 @cindex pragma Locking_Policy (under rts-pthread)
26491 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26492 @cindex @code{Inheritance_Locking} (under rts-pthread)
26493 @cindex @code{Ceiling_Locking} (under rts-pthread)
26495 As explained above, the native run-time library is based on the Solaris thread
26496 library (@code{libthread}) and is the default library.
26498 When the Solaris threads library is used (this is the default), programs
26499 compiled with GNAT can automatically take advantage of
26500 and can thus execute on multiple processors.
26501 The user can alternatively specify a processor on which the program should run
26502 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26504 setting the environment variable @env{GNAT_PROCESSOR}
26505 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26506 to one of the following:
26510 Use the default configuration (run the program on all
26511 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26515 Let the run-time implementation choose one processor and run the program on
26518 @item 0 .. Last_Proc
26519 Run the program on the specified processor.
26520 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26521 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26524 @node Linux-Specific Considerations
26525 @section Linux-Specific Considerations
26526 @cindex Linux threads libraries
26529 On GNU/Linux without NPTL support (usually system with GNU C Library
26530 older than 2.3), the signal model is not POSIX compliant, which means
26531 that to send a signal to the process, you need to send the signal to all
26532 threads, e.g.@: by using @code{killpg()}.
26534 @node AIX-Specific Considerations
26535 @section AIX-Specific Considerations
26536 @cindex AIX resolver library
26539 On AIX, the resolver library initializes some internal structure on
26540 the first call to @code{get*by*} functions, which are used to implement
26541 @code{GNAT.Sockets.Get_Host_By_Name} and
26542 @code{GNAT.Sockets.Get_Host_By_Address}.
26543 If such initialization occurs within an Ada task, and the stack size for
26544 the task is the default size, a stack overflow may occur.
26546 To avoid this overflow, the user should either ensure that the first call
26547 to @code{GNAT.Sockets.Get_Host_By_Name} or
26548 @code{GNAT.Sockets.Get_Host_By_Addrss}
26549 occurs in the environment task, or use @code{pragma Storage_Size} to
26550 specify a sufficiently large size for the stack of the task that contains
26553 @node Irix-Specific Considerations
26554 @section Irix-Specific Considerations
26555 @cindex Irix libraries
26558 The GCC support libraries coming with the Irix compiler have moved to
26559 their canonical place with respect to the general Irix ABI related
26560 conventions. Running applications built with the default shared GNAT
26561 run-time now requires the LD_LIBRARY_PATH environment variable to
26562 include this location. A possible way to achieve this is to issue the
26563 following command line on a bash prompt:
26567 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26571 @node RTX-Specific Considerations
26572 @section RTX-Specific Considerations
26573 @cindex RTX libraries
26576 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26577 API. Applications can be built to work in two different modes:
26581 Windows executables that run in Ring 3 to utilize memory protection
26582 (@emph{rts-rtx-w32}).
26585 Real-time subsystem (RTSS) executables that run in Ring 0, where
26586 performance can be optimized with RTSS applications taking precedent
26587 over all Windows applications (@emph{rts-rtx-rtss}).
26591 @c *******************************
26592 @node Example of Binder Output File
26593 @appendix Example of Binder Output File
26596 This Appendix displays the source code for @command{gnatbind}'s output
26597 file generated for a simple ``Hello World'' program.
26598 Comments have been added for clarification purposes.
26600 @smallexample @c adanocomment
26604 -- The package is called Ada_Main unless this name is actually used
26605 -- as a unit name in the partition, in which case some other unique
26609 package ada_main is
26611 Elab_Final_Code : Integer;
26612 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26614 -- The main program saves the parameters (argument count,
26615 -- argument values, environment pointer) in global variables
26616 -- for later access by other units including
26617 -- Ada.Command_Line.
26619 gnat_argc : Integer;
26620 gnat_argv : System.Address;
26621 gnat_envp : System.Address;
26623 -- The actual variables are stored in a library routine. This
26624 -- is useful for some shared library situations, where there
26625 -- are problems if variables are not in the library.
26627 pragma Import (C, gnat_argc);
26628 pragma Import (C, gnat_argv);
26629 pragma Import (C, gnat_envp);
26631 -- The exit status is similarly an external location
26633 gnat_exit_status : Integer;
26634 pragma Import (C, gnat_exit_status);
26636 GNAT_Version : constant String :=
26637 "GNAT Version: 6.0.0w (20061115)";
26638 pragma Export (C, GNAT_Version, "__gnat_version");
26640 -- This is the generated adafinal routine that performs
26641 -- finalization at the end of execution. In the case where
26642 -- Ada is the main program, this main program makes a call
26643 -- to adafinal at program termination.
26645 procedure adafinal;
26646 pragma Export (C, adafinal, "adafinal");
26648 -- This is the generated adainit routine that performs
26649 -- initialization at the start of execution. In the case
26650 -- where Ada is the main program, this main program makes
26651 -- a call to adainit at program startup.
26654 pragma Export (C, adainit, "adainit");
26656 -- This routine is called at the start of execution. It is
26657 -- a dummy routine that is used by the debugger to breakpoint
26658 -- at the start of execution.
26660 procedure Break_Start;
26661 pragma Import (C, Break_Start, "__gnat_break_start");
26663 -- This is the actual generated main program (it would be
26664 -- suppressed if the no main program switch were used). As
26665 -- required by standard system conventions, this program has
26666 -- the external name main.
26670 argv : System.Address;
26671 envp : System.Address)
26673 pragma Export (C, main, "main");
26675 -- The following set of constants give the version
26676 -- identification values for every unit in the bound
26677 -- partition. This identification is computed from all
26678 -- dependent semantic units, and corresponds to the
26679 -- string that would be returned by use of the
26680 -- Body_Version or Version attributes.
26682 type Version_32 is mod 2 ** 32;
26683 u00001 : constant Version_32 := 16#7880BEB3#;
26684 u00002 : constant Version_32 := 16#0D24CBD0#;
26685 u00003 : constant Version_32 := 16#3283DBEB#;
26686 u00004 : constant Version_32 := 16#2359F9ED#;
26687 u00005 : constant Version_32 := 16#664FB847#;
26688 u00006 : constant Version_32 := 16#68E803DF#;
26689 u00007 : constant Version_32 := 16#5572E604#;
26690 u00008 : constant Version_32 := 16#46B173D8#;
26691 u00009 : constant Version_32 := 16#156A40CF#;
26692 u00010 : constant Version_32 := 16#033DABE0#;
26693 u00011 : constant Version_32 := 16#6AB38FEA#;
26694 u00012 : constant Version_32 := 16#22B6217D#;
26695 u00013 : constant Version_32 := 16#68A22947#;
26696 u00014 : constant Version_32 := 16#18CC4A56#;
26697 u00015 : constant Version_32 := 16#08258E1B#;
26698 u00016 : constant Version_32 := 16#367D5222#;
26699 u00017 : constant Version_32 := 16#20C9ECA4#;
26700 u00018 : constant Version_32 := 16#50D32CB6#;
26701 u00019 : constant Version_32 := 16#39A8BB77#;
26702 u00020 : constant Version_32 := 16#5CF8FA2B#;
26703 u00021 : constant Version_32 := 16#2F1EB794#;
26704 u00022 : constant Version_32 := 16#31AB6444#;
26705 u00023 : constant Version_32 := 16#1574B6E9#;
26706 u00024 : constant Version_32 := 16#5109C189#;
26707 u00025 : constant Version_32 := 16#56D770CD#;
26708 u00026 : constant Version_32 := 16#02F9DE3D#;
26709 u00027 : constant Version_32 := 16#08AB6B2C#;
26710 u00028 : constant Version_32 := 16#3FA37670#;
26711 u00029 : constant Version_32 := 16#476457A0#;
26712 u00030 : constant Version_32 := 16#731E1B6E#;
26713 u00031 : constant Version_32 := 16#23C2E789#;
26714 u00032 : constant Version_32 := 16#0F1BD6A1#;
26715 u00033 : constant Version_32 := 16#7C25DE96#;
26716 u00034 : constant Version_32 := 16#39ADFFA2#;
26717 u00035 : constant Version_32 := 16#571DE3E7#;
26718 u00036 : constant Version_32 := 16#5EB646AB#;
26719 u00037 : constant Version_32 := 16#4249379B#;
26720 u00038 : constant Version_32 := 16#0357E00A#;
26721 u00039 : constant Version_32 := 16#3784FB72#;
26722 u00040 : constant Version_32 := 16#2E723019#;
26723 u00041 : constant Version_32 := 16#623358EA#;
26724 u00042 : constant Version_32 := 16#107F9465#;
26725 u00043 : constant Version_32 := 16#6843F68A#;
26726 u00044 : constant Version_32 := 16#63305874#;
26727 u00045 : constant Version_32 := 16#31E56CE1#;
26728 u00046 : constant Version_32 := 16#02917970#;
26729 u00047 : constant Version_32 := 16#6CCBA70E#;
26730 u00048 : constant Version_32 := 16#41CD4204#;
26731 u00049 : constant Version_32 := 16#572E3F58#;
26732 u00050 : constant Version_32 := 16#20729FF5#;
26733 u00051 : constant Version_32 := 16#1D4F93E8#;
26734 u00052 : constant Version_32 := 16#30B2EC3D#;
26735 u00053 : constant Version_32 := 16#34054F96#;
26736 u00054 : constant Version_32 := 16#5A199860#;
26737 u00055 : constant Version_32 := 16#0E7F912B#;
26738 u00056 : constant Version_32 := 16#5760634A#;
26739 u00057 : constant Version_32 := 16#5D851835#;
26741 -- The following Export pragmas export the version numbers
26742 -- with symbolic names ending in B (for body) or S
26743 -- (for spec) so that they can be located in a link. The
26744 -- information provided here is sufficient to track down
26745 -- the exact versions of units used in a given build.
26747 pragma Export (C, u00001, "helloB");
26748 pragma Export (C, u00002, "system__standard_libraryB");
26749 pragma Export (C, u00003, "system__standard_libraryS");
26750 pragma Export (C, u00004, "adaS");
26751 pragma Export (C, u00005, "ada__text_ioB");
26752 pragma Export (C, u00006, "ada__text_ioS");
26753 pragma Export (C, u00007, "ada__exceptionsB");
26754 pragma Export (C, u00008, "ada__exceptionsS");
26755 pragma Export (C, u00009, "gnatS");
26756 pragma Export (C, u00010, "gnat__heap_sort_aB");
26757 pragma Export (C, u00011, "gnat__heap_sort_aS");
26758 pragma Export (C, u00012, "systemS");
26759 pragma Export (C, u00013, "system__exception_tableB");
26760 pragma Export (C, u00014, "system__exception_tableS");
26761 pragma Export (C, u00015, "gnat__htableB");
26762 pragma Export (C, u00016, "gnat__htableS");
26763 pragma Export (C, u00017, "system__exceptionsS");
26764 pragma Export (C, u00018, "system__machine_state_operationsB");
26765 pragma Export (C, u00019, "system__machine_state_operationsS");
26766 pragma Export (C, u00020, "system__machine_codeS");
26767 pragma Export (C, u00021, "system__storage_elementsB");
26768 pragma Export (C, u00022, "system__storage_elementsS");
26769 pragma Export (C, u00023, "system__secondary_stackB");
26770 pragma Export (C, u00024, "system__secondary_stackS");
26771 pragma Export (C, u00025, "system__parametersB");
26772 pragma Export (C, u00026, "system__parametersS");
26773 pragma Export (C, u00027, "system__soft_linksB");
26774 pragma Export (C, u00028, "system__soft_linksS");
26775 pragma Export (C, u00029, "system__stack_checkingB");
26776 pragma Export (C, u00030, "system__stack_checkingS");
26777 pragma Export (C, u00031, "system__tracebackB");
26778 pragma Export (C, u00032, "system__tracebackS");
26779 pragma Export (C, u00033, "ada__streamsS");
26780 pragma Export (C, u00034, "ada__tagsB");
26781 pragma Export (C, u00035, "ada__tagsS");
26782 pragma Export (C, u00036, "system__string_opsB");
26783 pragma Export (C, u00037, "system__string_opsS");
26784 pragma Export (C, u00038, "interfacesS");
26785 pragma Export (C, u00039, "interfaces__c_streamsB");
26786 pragma Export (C, u00040, "interfaces__c_streamsS");
26787 pragma Export (C, u00041, "system__file_ioB");
26788 pragma Export (C, u00042, "system__file_ioS");
26789 pragma Export (C, u00043, "ada__finalizationB");
26790 pragma Export (C, u00044, "ada__finalizationS");
26791 pragma Export (C, u00045, "system__finalization_rootB");
26792 pragma Export (C, u00046, "system__finalization_rootS");
26793 pragma Export (C, u00047, "system__finalization_implementationB");
26794 pragma Export (C, u00048, "system__finalization_implementationS");
26795 pragma Export (C, u00049, "system__string_ops_concat_3B");
26796 pragma Export (C, u00050, "system__string_ops_concat_3S");
26797 pragma Export (C, u00051, "system__stream_attributesB");
26798 pragma Export (C, u00052, "system__stream_attributesS");
26799 pragma Export (C, u00053, "ada__io_exceptionsS");
26800 pragma Export (C, u00054, "system__unsigned_typesS");
26801 pragma Export (C, u00055, "system__file_control_blockS");
26802 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26803 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26805 -- BEGIN ELABORATION ORDER
26808 -- gnat.heap_sort_a (spec)
26809 -- gnat.heap_sort_a (body)
26810 -- gnat.htable (spec)
26811 -- gnat.htable (body)
26812 -- interfaces (spec)
26814 -- system.machine_code (spec)
26815 -- system.parameters (spec)
26816 -- system.parameters (body)
26817 -- interfaces.c_streams (spec)
26818 -- interfaces.c_streams (body)
26819 -- system.standard_library (spec)
26820 -- ada.exceptions (spec)
26821 -- system.exception_table (spec)
26822 -- system.exception_table (body)
26823 -- ada.io_exceptions (spec)
26824 -- system.exceptions (spec)
26825 -- system.storage_elements (spec)
26826 -- system.storage_elements (body)
26827 -- system.machine_state_operations (spec)
26828 -- system.machine_state_operations (body)
26829 -- system.secondary_stack (spec)
26830 -- system.stack_checking (spec)
26831 -- system.soft_links (spec)
26832 -- system.soft_links (body)
26833 -- system.stack_checking (body)
26834 -- system.secondary_stack (body)
26835 -- system.standard_library (body)
26836 -- system.string_ops (spec)
26837 -- system.string_ops (body)
26840 -- ada.streams (spec)
26841 -- system.finalization_root (spec)
26842 -- system.finalization_root (body)
26843 -- system.string_ops_concat_3 (spec)
26844 -- system.string_ops_concat_3 (body)
26845 -- system.traceback (spec)
26846 -- system.traceback (body)
26847 -- ada.exceptions (body)
26848 -- system.unsigned_types (spec)
26849 -- system.stream_attributes (spec)
26850 -- system.stream_attributes (body)
26851 -- system.finalization_implementation (spec)
26852 -- system.finalization_implementation (body)
26853 -- ada.finalization (spec)
26854 -- ada.finalization (body)
26855 -- ada.finalization.list_controller (spec)
26856 -- ada.finalization.list_controller (body)
26857 -- system.file_control_block (spec)
26858 -- system.file_io (spec)
26859 -- system.file_io (body)
26860 -- ada.text_io (spec)
26861 -- ada.text_io (body)
26863 -- END ELABORATION ORDER
26867 -- The following source file name pragmas allow the generated file
26868 -- names to be unique for different main programs. They are needed
26869 -- since the package name will always be Ada_Main.
26871 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26872 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26874 -- Generated package body for Ada_Main starts here
26876 package body ada_main is
26878 -- The actual finalization is performed by calling the
26879 -- library routine in System.Standard_Library.Adafinal
26881 procedure Do_Finalize;
26882 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26889 procedure adainit is
26891 -- These booleans are set to True once the associated unit has
26892 -- been elaborated. It is also used to avoid elaborating the
26893 -- same unit twice.
26896 pragma Import (Ada, E040, "interfaces__c_streams_E");
26899 pragma Import (Ada, E008, "ada__exceptions_E");
26902 pragma Import (Ada, E014, "system__exception_table_E");
26905 pragma Import (Ada, E053, "ada__io_exceptions_E");
26908 pragma Import (Ada, E017, "system__exceptions_E");
26911 pragma Import (Ada, E024, "system__secondary_stack_E");
26914 pragma Import (Ada, E030, "system__stack_checking_E");
26917 pragma Import (Ada, E028, "system__soft_links_E");
26920 pragma Import (Ada, E035, "ada__tags_E");
26923 pragma Import (Ada, E033, "ada__streams_E");
26926 pragma Import (Ada, E046, "system__finalization_root_E");
26929 pragma Import (Ada, E048, "system__finalization_implementation_E");
26932 pragma Import (Ada, E044, "ada__finalization_E");
26935 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26938 pragma Import (Ada, E055, "system__file_control_block_E");
26941 pragma Import (Ada, E042, "system__file_io_E");
26944 pragma Import (Ada, E006, "ada__text_io_E");
26946 -- Set_Globals is a library routine that stores away the
26947 -- value of the indicated set of global values in global
26948 -- variables within the library.
26950 procedure Set_Globals
26951 (Main_Priority : Integer;
26952 Time_Slice_Value : Integer;
26953 WC_Encoding : Character;
26954 Locking_Policy : Character;
26955 Queuing_Policy : Character;
26956 Task_Dispatching_Policy : Character;
26957 Adafinal : System.Address;
26958 Unreserve_All_Interrupts : Integer;
26959 Exception_Tracebacks : Integer);
26960 @findex __gnat_set_globals
26961 pragma Import (C, Set_Globals, "__gnat_set_globals");
26963 -- SDP_Table_Build is a library routine used to build the
26964 -- exception tables. See unit Ada.Exceptions in files
26965 -- a-except.ads/adb for full details of how zero cost
26966 -- exception handling works. This procedure, the call to
26967 -- it, and the two following tables are all omitted if the
26968 -- build is in longjmp/setjmp exception mode.
26970 @findex SDP_Table_Build
26971 @findex Zero Cost Exceptions
26972 procedure SDP_Table_Build
26973 (SDP_Addresses : System.Address;
26974 SDP_Count : Natural;
26975 Elab_Addresses : System.Address;
26976 Elab_Addr_Count : Natural);
26977 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26979 -- Table of Unit_Exception_Table addresses. Used for zero
26980 -- cost exception handling to build the top level table.
26982 ST : aliased constant array (1 .. 23) of System.Address := (
26984 Ada.Text_Io'UET_Address,
26985 Ada.Exceptions'UET_Address,
26986 Gnat.Heap_Sort_A'UET_Address,
26987 System.Exception_Table'UET_Address,
26988 System.Machine_State_Operations'UET_Address,
26989 System.Secondary_Stack'UET_Address,
26990 System.Parameters'UET_Address,
26991 System.Soft_Links'UET_Address,
26992 System.Stack_Checking'UET_Address,
26993 System.Traceback'UET_Address,
26994 Ada.Streams'UET_Address,
26995 Ada.Tags'UET_Address,
26996 System.String_Ops'UET_Address,
26997 Interfaces.C_Streams'UET_Address,
26998 System.File_Io'UET_Address,
26999 Ada.Finalization'UET_Address,
27000 System.Finalization_Root'UET_Address,
27001 System.Finalization_Implementation'UET_Address,
27002 System.String_Ops_Concat_3'UET_Address,
27003 System.Stream_Attributes'UET_Address,
27004 System.File_Control_Block'UET_Address,
27005 Ada.Finalization.List_Controller'UET_Address);
27007 -- Table of addresses of elaboration routines. Used for
27008 -- zero cost exception handling to make sure these
27009 -- addresses are included in the top level procedure
27012 EA : aliased constant array (1 .. 23) of System.Address := (
27013 adainit'Code_Address,
27014 Do_Finalize'Code_Address,
27015 Ada.Exceptions'Elab_Spec'Address,
27016 System.Exceptions'Elab_Spec'Address,
27017 Interfaces.C_Streams'Elab_Spec'Address,
27018 System.Exception_Table'Elab_Body'Address,
27019 Ada.Io_Exceptions'Elab_Spec'Address,
27020 System.Stack_Checking'Elab_Spec'Address,
27021 System.Soft_Links'Elab_Body'Address,
27022 System.Secondary_Stack'Elab_Body'Address,
27023 Ada.Tags'Elab_Spec'Address,
27024 Ada.Tags'Elab_Body'Address,
27025 Ada.Streams'Elab_Spec'Address,
27026 System.Finalization_Root'Elab_Spec'Address,
27027 Ada.Exceptions'Elab_Body'Address,
27028 System.Finalization_Implementation'Elab_Spec'Address,
27029 System.Finalization_Implementation'Elab_Body'Address,
27030 Ada.Finalization'Elab_Spec'Address,
27031 Ada.Finalization.List_Controller'Elab_Spec'Address,
27032 System.File_Control_Block'Elab_Spec'Address,
27033 System.File_Io'Elab_Body'Address,
27034 Ada.Text_Io'Elab_Spec'Address,
27035 Ada.Text_Io'Elab_Body'Address);
27037 -- Start of processing for adainit
27041 -- Call SDP_Table_Build to build the top level procedure
27042 -- table for zero cost exception handling (omitted in
27043 -- longjmp/setjmp mode).
27045 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27047 -- Call Set_Globals to record various information for
27048 -- this partition. The values are derived by the binder
27049 -- from information stored in the ali files by the compiler.
27051 @findex __gnat_set_globals
27053 (Main_Priority => -1,
27054 -- Priority of main program, -1 if no pragma Priority used
27056 Time_Slice_Value => -1,
27057 -- Time slice from Time_Slice pragma, -1 if none used
27059 WC_Encoding => 'b',
27060 -- Wide_Character encoding used, default is brackets
27062 Locking_Policy => ' ',
27063 -- Locking_Policy used, default of space means not
27064 -- specified, otherwise it is the first character of
27065 -- the policy name.
27067 Queuing_Policy => ' ',
27068 -- Queuing_Policy used, default of space means not
27069 -- specified, otherwise it is the first character of
27070 -- the policy name.
27072 Task_Dispatching_Policy => ' ',
27073 -- Task_Dispatching_Policy used, default of space means
27074 -- not specified, otherwise first character of the
27077 Adafinal => System.Null_Address,
27078 -- Address of Adafinal routine, not used anymore
27080 Unreserve_All_Interrupts => 0,
27081 -- Set true if pragma Unreserve_All_Interrupts was used
27083 Exception_Tracebacks => 0);
27084 -- Indicates if exception tracebacks are enabled
27086 Elab_Final_Code := 1;
27088 -- Now we have the elaboration calls for all units in the partition.
27089 -- The Elab_Spec and Elab_Body attributes generate references to the
27090 -- implicit elaboration procedures generated by the compiler for
27091 -- each unit that requires elaboration.
27094 Interfaces.C_Streams'Elab_Spec;
27098 Ada.Exceptions'Elab_Spec;
27101 System.Exception_Table'Elab_Body;
27105 Ada.Io_Exceptions'Elab_Spec;
27109 System.Exceptions'Elab_Spec;
27113 System.Stack_Checking'Elab_Spec;
27116 System.Soft_Links'Elab_Body;
27121 System.Secondary_Stack'Elab_Body;
27125 Ada.Tags'Elab_Spec;
27128 Ada.Tags'Elab_Body;
27132 Ada.Streams'Elab_Spec;
27136 System.Finalization_Root'Elab_Spec;
27140 Ada.Exceptions'Elab_Body;
27144 System.Finalization_Implementation'Elab_Spec;
27147 System.Finalization_Implementation'Elab_Body;
27151 Ada.Finalization'Elab_Spec;
27155 Ada.Finalization.List_Controller'Elab_Spec;
27159 System.File_Control_Block'Elab_Spec;
27163 System.File_Io'Elab_Body;
27167 Ada.Text_Io'Elab_Spec;
27170 Ada.Text_Io'Elab_Body;
27174 Elab_Final_Code := 0;
27182 procedure adafinal is
27191 -- main is actually a function, as in the ANSI C standard,
27192 -- defined to return the exit status. The three parameters
27193 -- are the argument count, argument values and environment
27196 @findex Main Program
27199 argv : System.Address;
27200 envp : System.Address)
27203 -- The initialize routine performs low level system
27204 -- initialization using a standard library routine which
27205 -- sets up signal handling and performs any other
27206 -- required setup. The routine can be found in file
27209 @findex __gnat_initialize
27210 procedure initialize;
27211 pragma Import (C, initialize, "__gnat_initialize");
27213 -- The finalize routine performs low level system
27214 -- finalization using a standard library routine. The
27215 -- routine is found in file a-final.c and in the standard
27216 -- distribution is a dummy routine that does nothing, so
27217 -- really this is a hook for special user finalization.
27219 @findex __gnat_finalize
27220 procedure finalize;
27221 pragma Import (C, finalize, "__gnat_finalize");
27223 -- We get to the main program of the partition by using
27224 -- pragma Import because if we try to with the unit and
27225 -- call it Ada style, then not only do we waste time
27226 -- recompiling it, but also, we don't really know the right
27227 -- switches (e.g.@: identifier character set) to be used
27230 procedure Ada_Main_Program;
27231 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27233 -- Start of processing for main
27236 -- Save global variables
27242 -- Call low level system initialization
27246 -- Call our generated Ada initialization routine
27250 -- This is the point at which we want the debugger to get
27255 -- Now we call the main program of the partition
27259 -- Perform Ada finalization
27263 -- Perform low level system finalization
27267 -- Return the proper exit status
27268 return (gnat_exit_status);
27271 -- This section is entirely comments, so it has no effect on the
27272 -- compilation of the Ada_Main package. It provides the list of
27273 -- object files and linker options, as well as some standard
27274 -- libraries needed for the link. The gnatlink utility parses
27275 -- this b~hello.adb file to read these comment lines to generate
27276 -- the appropriate command line arguments for the call to the
27277 -- system linker. The BEGIN/END lines are used for sentinels for
27278 -- this parsing operation.
27280 -- The exact file names will of course depend on the environment,
27281 -- host/target and location of files on the host system.
27283 @findex Object file list
27284 -- BEGIN Object file/option list
27287 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27288 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27289 -- END Object file/option list
27295 The Ada code in the above example is exactly what is generated by the
27296 binder. We have added comments to more clearly indicate the function
27297 of each part of the generated @code{Ada_Main} package.
27299 The code is standard Ada in all respects, and can be processed by any
27300 tools that handle Ada. In particular, it is possible to use the debugger
27301 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27302 suppose that for reasons that you do not understand, your program is crashing
27303 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27304 you can place a breakpoint on the call:
27306 @smallexample @c ada
27307 Ada.Text_Io'Elab_Body;
27311 and trace the elaboration routine for this package to find out where
27312 the problem might be (more usually of course you would be debugging
27313 elaboration code in your own application).
27315 @node Elaboration Order Handling in GNAT
27316 @appendix Elaboration Order Handling in GNAT
27317 @cindex Order of elaboration
27318 @cindex Elaboration control
27321 * Elaboration Code::
27322 * Checking the Elaboration Order::
27323 * Controlling the Elaboration Order::
27324 * Controlling Elaboration in GNAT - Internal Calls::
27325 * Controlling Elaboration in GNAT - External Calls::
27326 * Default Behavior in GNAT - Ensuring Safety::
27327 * Treatment of Pragma Elaborate::
27328 * Elaboration Issues for Library Tasks::
27329 * Mixing Elaboration Models::
27330 * What to Do If the Default Elaboration Behavior Fails::
27331 * Elaboration for Access-to-Subprogram Values::
27332 * Summary of Procedures for Elaboration Control::
27333 * Other Elaboration Order Considerations::
27337 This chapter describes the handling of elaboration code in Ada and
27338 in GNAT, and discusses how the order of elaboration of program units can
27339 be controlled in GNAT, either automatically or with explicit programming
27342 @node Elaboration Code
27343 @section Elaboration Code
27346 Ada provides rather general mechanisms for executing code at elaboration
27347 time, that is to say before the main program starts executing. Such code arises
27351 @item Initializers for variables.
27352 Variables declared at the library level, in package specs or bodies, can
27353 require initialization that is performed at elaboration time, as in:
27354 @smallexample @c ada
27356 Sqrt_Half : Float := Sqrt (0.5);
27360 @item Package initialization code
27361 Code in a @code{BEGIN-END} section at the outer level of a package body is
27362 executed as part of the package body elaboration code.
27364 @item Library level task allocators
27365 Tasks that are declared using task allocators at the library level
27366 start executing immediately and hence can execute at elaboration time.
27370 Subprogram calls are possible in any of these contexts, which means that
27371 any arbitrary part of the program may be executed as part of the elaboration
27372 code. It is even possible to write a program which does all its work at
27373 elaboration time, with a null main program, although stylistically this
27374 would usually be considered an inappropriate way to structure
27377 An important concern arises in the context of elaboration code:
27378 we have to be sure that it is executed in an appropriate order. What we
27379 have is a series of elaboration code sections, potentially one section
27380 for each unit in the program. It is important that these execute
27381 in the correct order. Correctness here means that, taking the above
27382 example of the declaration of @code{Sqrt_Half},
27383 if some other piece of
27384 elaboration code references @code{Sqrt_Half},
27385 then it must run after the
27386 section of elaboration code that contains the declaration of
27389 There would never be any order of elaboration problem if we made a rule
27390 that whenever you @code{with} a unit, you must elaborate both the spec and body
27391 of that unit before elaborating the unit doing the @code{with}'ing:
27393 @smallexample @c ada
27397 package Unit_2 is @dots{}
27403 would require that both the body and spec of @code{Unit_1} be elaborated
27404 before the spec of @code{Unit_2}. However, a rule like that would be far too
27405 restrictive. In particular, it would make it impossible to have routines
27406 in separate packages that were mutually recursive.
27408 You might think that a clever enough compiler could look at the actual
27409 elaboration code and determine an appropriate correct order of elaboration,
27410 but in the general case, this is not possible. Consider the following
27413 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27415 the variable @code{Sqrt_1}, which is declared in the elaboration code
27416 of the body of @code{Unit_1}:
27418 @smallexample @c ada
27420 Sqrt_1 : Float := Sqrt (0.1);
27425 The elaboration code of the body of @code{Unit_1} also contains:
27427 @smallexample @c ada
27430 if expression_1 = 1 then
27431 Q := Unit_2.Func_2;
27438 @code{Unit_2} is exactly parallel,
27439 it has a procedure @code{Func_2} that references
27440 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27441 the body @code{Unit_2}:
27443 @smallexample @c ada
27445 Sqrt_2 : Float := Sqrt (0.1);
27450 The elaboration code of the body of @code{Unit_2} also contains:
27452 @smallexample @c ada
27455 if expression_2 = 2 then
27456 Q := Unit_1.Func_1;
27463 Now the question is, which of the following orders of elaboration is
27488 If you carefully analyze the flow here, you will see that you cannot tell
27489 at compile time the answer to this question.
27490 If @code{expression_1} is not equal to 1,
27491 and @code{expression_2} is not equal to 2,
27492 then either order is acceptable, because neither of the function calls is
27493 executed. If both tests evaluate to true, then neither order is acceptable
27494 and in fact there is no correct order.
27496 If one of the two expressions is true, and the other is false, then one
27497 of the above orders is correct, and the other is incorrect. For example,
27498 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27499 then the call to @code{Func_1}
27500 will occur, but not the call to @code{Func_2.}
27501 This means that it is essential
27502 to elaborate the body of @code{Unit_1} before
27503 the body of @code{Unit_2}, so the first
27504 order of elaboration is correct and the second is wrong.
27506 By making @code{expression_1} and @code{expression_2}
27507 depend on input data, or perhaps
27508 the time of day, we can make it impossible for the compiler or binder
27509 to figure out which of these expressions will be true, and hence it
27510 is impossible to guarantee a safe order of elaboration at run time.
27512 @node Checking the Elaboration Order
27513 @section Checking the Elaboration Order
27516 In some languages that involve the same kind of elaboration problems,
27517 e.g.@: Java and C++, the programmer is expected to worry about these
27518 ordering problems himself, and it is common to
27519 write a program in which an incorrect elaboration order gives
27520 surprising results, because it references variables before they
27522 Ada is designed to be a safe language, and a programmer-beware approach is
27523 clearly not sufficient. Consequently, the language provides three lines
27527 @item Standard rules
27528 Some standard rules restrict the possible choice of elaboration
27529 order. In particular, if you @code{with} a unit, then its spec is always
27530 elaborated before the unit doing the @code{with}. Similarly, a parent
27531 spec is always elaborated before the child spec, and finally
27532 a spec is always elaborated before its corresponding body.
27534 @item Dynamic elaboration checks
27535 @cindex Elaboration checks
27536 @cindex Checks, elaboration
27537 Dynamic checks are made at run time, so that if some entity is accessed
27538 before it is elaborated (typically by means of a subprogram call)
27539 then the exception (@code{Program_Error}) is raised.
27541 @item Elaboration control
27542 Facilities are provided for the programmer to specify the desired order
27546 Let's look at these facilities in more detail. First, the rules for
27547 dynamic checking. One possible rule would be simply to say that the
27548 exception is raised if you access a variable which has not yet been
27549 elaborated. The trouble with this approach is that it could require
27550 expensive checks on every variable reference. Instead Ada has two
27551 rules which are a little more restrictive, but easier to check, and
27555 @item Restrictions on calls
27556 A subprogram can only be called at elaboration time if its body
27557 has been elaborated. The rules for elaboration given above guarantee
27558 that the spec of the subprogram has been elaborated before the
27559 call, but not the body. If this rule is violated, then the
27560 exception @code{Program_Error} is raised.
27562 @item Restrictions on instantiations
27563 A generic unit can only be instantiated if the body of the generic
27564 unit has been elaborated. Again, the rules for elaboration given above
27565 guarantee that the spec of the generic unit has been elaborated
27566 before the instantiation, but not the body. If this rule is
27567 violated, then the exception @code{Program_Error} is raised.
27571 The idea is that if the body has been elaborated, then any variables
27572 it references must have been elaborated; by checking for the body being
27573 elaborated we guarantee that none of its references causes any
27574 trouble. As we noted above, this is a little too restrictive, because a
27575 subprogram that has no non-local references in its body may in fact be safe
27576 to call. However, it really would be unsafe to rely on this, because
27577 it would mean that the caller was aware of details of the implementation
27578 in the body. This goes against the basic tenets of Ada.
27580 A plausible implementation can be described as follows.
27581 A Boolean variable is associated with each subprogram
27582 and each generic unit. This variable is initialized to False, and is set to
27583 True at the point body is elaborated. Every call or instantiation checks the
27584 variable, and raises @code{Program_Error} if the variable is False.
27586 Note that one might think that it would be good enough to have one Boolean
27587 variable for each package, but that would not deal with cases of trying
27588 to call a body in the same package as the call
27589 that has not been elaborated yet.
27590 Of course a compiler may be able to do enough analysis to optimize away
27591 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27592 does such optimizations, but still the easiest conceptual model is to
27593 think of there being one variable per subprogram.
27595 @node Controlling the Elaboration Order
27596 @section Controlling the Elaboration Order
27599 In the previous section we discussed the rules in Ada which ensure
27600 that @code{Program_Error} is raised if an incorrect elaboration order is
27601 chosen. This prevents erroneous executions, but we need mechanisms to
27602 specify a correct execution and avoid the exception altogether.
27603 To achieve this, Ada provides a number of features for controlling
27604 the order of elaboration. We discuss these features in this section.
27606 First, there are several ways of indicating to the compiler that a given
27607 unit has no elaboration problems:
27610 @item packages that do not require a body
27611 A library package that does not require a body does not permit
27612 a body (this rule was introduced in Ada 95).
27613 Thus if we have a such a package, as in:
27615 @smallexample @c ada
27618 package Definitions is
27620 type m is new integer;
27622 type a is array (1 .. 10) of m;
27623 type b is array (1 .. 20) of m;
27631 A package that @code{with}'s @code{Definitions} may safely instantiate
27632 @code{Definitions.Subp} because the compiler can determine that there
27633 definitely is no package body to worry about in this case
27636 @cindex pragma Pure
27638 Places sufficient restrictions on a unit to guarantee that
27639 no call to any subprogram in the unit can result in an
27640 elaboration problem. This means that the compiler does not need
27641 to worry about the point of elaboration of such units, and in
27642 particular, does not need to check any calls to any subprograms
27645 @item pragma Preelaborate
27646 @findex Preelaborate
27647 @cindex pragma Preelaborate
27648 This pragma places slightly less stringent restrictions on a unit than
27650 but these restrictions are still sufficient to ensure that there
27651 are no elaboration problems with any calls to the unit.
27653 @item pragma Elaborate_Body
27654 @findex Elaborate_Body
27655 @cindex pragma Elaborate_Body
27656 This pragma requires that the body of a unit be elaborated immediately
27657 after its spec. Suppose a unit @code{A} has such a pragma,
27658 and unit @code{B} does
27659 a @code{with} of unit @code{A}. Recall that the standard rules require
27660 the spec of unit @code{A}
27661 to be elaborated before the @code{with}'ing unit; given the pragma in
27662 @code{A}, we also know that the body of @code{A}
27663 will be elaborated before @code{B}, so
27664 that calls to @code{A} are safe and do not need a check.
27669 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27671 @code{Elaborate_Body} does not guarantee that the program is
27672 free of elaboration problems, because it may not be possible
27673 to satisfy the requested elaboration order.
27674 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27676 marks @code{Unit_1} as @code{Elaborate_Body},
27677 and not @code{Unit_2,} then the order of
27678 elaboration will be:
27690 Now that means that the call to @code{Func_1} in @code{Unit_2}
27691 need not be checked,
27692 it must be safe. But the call to @code{Func_2} in
27693 @code{Unit_1} may still fail if
27694 @code{Expression_1} is equal to 1,
27695 and the programmer must still take
27696 responsibility for this not being the case.
27698 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27699 eliminated, except for calls entirely within a body, which are
27700 in any case fully under programmer control. However, using the pragma
27701 everywhere is not always possible.
27702 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27703 we marked both of them as having pragma @code{Elaborate_Body}, then
27704 clearly there would be no possible elaboration order.
27706 The above pragmas allow a server to guarantee safe use by clients, and
27707 clearly this is the preferable approach. Consequently a good rule
27708 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27709 and if this is not possible,
27710 mark them as @code{Elaborate_Body} if possible.
27711 As we have seen, there are situations where neither of these
27712 three pragmas can be used.
27713 So we also provide methods for clients to control the
27714 order of elaboration of the servers on which they depend:
27717 @item pragma Elaborate (unit)
27719 @cindex pragma Elaborate
27720 This pragma is placed in the context clause, after a @code{with} clause,
27721 and it requires that the body of the named unit be elaborated before
27722 the unit in which the pragma occurs. The idea is to use this pragma
27723 if the current unit calls at elaboration time, directly or indirectly,
27724 some subprogram in the named unit.
27726 @item pragma Elaborate_All (unit)
27727 @findex Elaborate_All
27728 @cindex pragma Elaborate_All
27729 This is a stronger version of the Elaborate pragma. Consider the
27733 Unit A @code{with}'s unit B and calls B.Func in elab code
27734 Unit B @code{with}'s unit C, and B.Func calls C.Func
27738 Now if we put a pragma @code{Elaborate (B)}
27739 in unit @code{A}, this ensures that the
27740 body of @code{B} is elaborated before the call, but not the
27741 body of @code{C}, so
27742 the call to @code{C.Func} could still cause @code{Program_Error} to
27745 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27746 not only that the body of the named unit be elaborated before the
27747 unit doing the @code{with}, but also the bodies of all units that the
27748 named unit uses, following @code{with} links transitively. For example,
27749 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27751 not only that the body of @code{B} be elaborated before @code{A},
27753 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27757 We are now in a position to give a usage rule in Ada for avoiding
27758 elaboration problems, at least if dynamic dispatching and access to
27759 subprogram values are not used. We will handle these cases separately
27762 The rule is simple. If a unit has elaboration code that can directly or
27763 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27764 a generic package in a @code{with}'ed unit,
27765 then if the @code{with}'ed unit does not have
27766 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27767 a pragma @code{Elaborate_All}
27768 for the @code{with}'ed unit. By following this rule a client is
27769 assured that calls can be made without risk of an exception.
27771 For generic subprogram instantiations, the rule can be relaxed to
27772 require only a pragma @code{Elaborate} since elaborating the body
27773 of a subprogram cannot cause any transitive elaboration (we are
27774 not calling the subprogram in this case, just elaborating its
27777 If this rule is not followed, then a program may be in one of four
27781 @item No order exists
27782 No order of elaboration exists which follows the rules, taking into
27783 account any @code{Elaborate}, @code{Elaborate_All},
27784 or @code{Elaborate_Body} pragmas. In
27785 this case, an Ada compiler must diagnose the situation at bind
27786 time, and refuse to build an executable program.
27788 @item One or more orders exist, all incorrect
27789 One or more acceptable elaboration orders exist, and all of them
27790 generate an elaboration order problem. In this case, the binder
27791 can build an executable program, but @code{Program_Error} will be raised
27792 when the program is run.
27794 @item Several orders exist, some right, some incorrect
27795 One or more acceptable elaboration orders exists, and some of them
27796 work, and some do not. The programmer has not controlled
27797 the order of elaboration, so the binder may or may not pick one of
27798 the correct orders, and the program may or may not raise an
27799 exception when it is run. This is the worst case, because it means
27800 that the program may fail when moved to another compiler, or even
27801 another version of the same compiler.
27803 @item One or more orders exists, all correct
27804 One ore more acceptable elaboration orders exist, and all of them
27805 work. In this case the program runs successfully. This state of
27806 affairs can be guaranteed by following the rule we gave above, but
27807 may be true even if the rule is not followed.
27811 Note that one additional advantage of following our rules on the use
27812 of @code{Elaborate} and @code{Elaborate_All}
27813 is that the program continues to stay in the ideal (all orders OK) state
27814 even if maintenance
27815 changes some bodies of some units. Conversely, if a program that does
27816 not follow this rule happens to be safe at some point, this state of affairs
27817 may deteriorate silently as a result of maintenance changes.
27819 You may have noticed that the above discussion did not mention
27820 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27821 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27822 code in the body makes calls to some other unit, so it is still necessary
27823 to use @code{Elaborate_All} on such units.
27825 @node Controlling Elaboration in GNAT - Internal Calls
27826 @section Controlling Elaboration in GNAT - Internal Calls
27829 In the case of internal calls, i.e., calls within a single package, the
27830 programmer has full control over the order of elaboration, and it is up
27831 to the programmer to elaborate declarations in an appropriate order. For
27834 @smallexample @c ada
27837 function One return Float;
27841 function One return Float is
27850 will obviously raise @code{Program_Error} at run time, because function
27851 One will be called before its body is elaborated. In this case GNAT will
27852 generate a warning that the call will raise @code{Program_Error}:
27858 2. function One return Float;
27860 4. Q : Float := One;
27862 >>> warning: cannot call "One" before body is elaborated
27863 >>> warning: Program_Error will be raised at run time
27866 6. function One return Float is
27879 Note that in this particular case, it is likely that the call is safe, because
27880 the function @code{One} does not access any global variables.
27881 Nevertheless in Ada, we do not want the validity of the check to depend on
27882 the contents of the body (think about the separate compilation case), so this
27883 is still wrong, as we discussed in the previous sections.
27885 The error is easily corrected by rearranging the declarations so that the
27886 body of @code{One} appears before the declaration containing the call
27887 (note that in Ada 95 and Ada 2005,
27888 declarations can appear in any order, so there is no restriction that
27889 would prevent this reordering, and if we write:
27891 @smallexample @c ada
27894 function One return Float;
27896 function One return Float is
27907 then all is well, no warning is generated, and no
27908 @code{Program_Error} exception
27910 Things are more complicated when a chain of subprograms is executed:
27912 @smallexample @c ada
27915 function A return Integer;
27916 function B return Integer;
27917 function C return Integer;
27919 function B return Integer is begin return A; end;
27920 function C return Integer is begin return B; end;
27924 function A return Integer is begin return 1; end;
27930 Now the call to @code{C}
27931 at elaboration time in the declaration of @code{X} is correct, because
27932 the body of @code{C} is already elaborated,
27933 and the call to @code{B} within the body of
27934 @code{C} is correct, but the call
27935 to @code{A} within the body of @code{B} is incorrect, because the body
27936 of @code{A} has not been elaborated, so @code{Program_Error}
27937 will be raised on the call to @code{A}.
27938 In this case GNAT will generate a
27939 warning that @code{Program_Error} may be
27940 raised at the point of the call. Let's look at the warning:
27946 2. function A return Integer;
27947 3. function B return Integer;
27948 4. function C return Integer;
27950 6. function B return Integer is begin return A; end;
27952 >>> warning: call to "A" before body is elaborated may
27953 raise Program_Error
27954 >>> warning: "B" called at line 7
27955 >>> warning: "C" called at line 9
27957 7. function C return Integer is begin return B; end;
27959 9. X : Integer := C;
27961 11. function A return Integer is begin return 1; end;
27971 Note that the message here says ``may raise'', instead of the direct case,
27972 where the message says ``will be raised''. That's because whether
27974 actually called depends in general on run-time flow of control.
27975 For example, if the body of @code{B} said
27977 @smallexample @c ada
27980 function B return Integer is
27982 if some-condition-depending-on-input-data then
27993 then we could not know until run time whether the incorrect call to A would
27994 actually occur, so @code{Program_Error} might
27995 or might not be raised. It is possible for a compiler to
27996 do a better job of analyzing bodies, to
27997 determine whether or not @code{Program_Error}
27998 might be raised, but it certainly
27999 couldn't do a perfect job (that would require solving the halting problem
28000 and is provably impossible), and because this is a warning anyway, it does
28001 not seem worth the effort to do the analysis. Cases in which it
28002 would be relevant are rare.
28004 In practice, warnings of either of the forms given
28005 above will usually correspond to
28006 real errors, and should be examined carefully and eliminated.
28007 In the rare case where a warning is bogus, it can be suppressed by any of
28008 the following methods:
28012 Compile with the @option{-gnatws} switch set
28015 Suppress @code{Elaboration_Check} for the called subprogram
28018 Use pragma @code{Warnings_Off} to turn warnings off for the call
28022 For the internal elaboration check case,
28023 GNAT by default generates the
28024 necessary run-time checks to ensure
28025 that @code{Program_Error} is raised if any
28026 call fails an elaboration check. Of course this can only happen if a
28027 warning has been issued as described above. The use of pragma
28028 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28029 some of these checks, meaning that it may be possible (but is not
28030 guaranteed) for a program to be able to call a subprogram whose body
28031 is not yet elaborated, without raising a @code{Program_Error} exception.
28033 @node Controlling Elaboration in GNAT - External Calls
28034 @section Controlling Elaboration in GNAT - External Calls
28037 The previous section discussed the case in which the execution of a
28038 particular thread of elaboration code occurred entirely within a
28039 single unit. This is the easy case to handle, because a programmer
28040 has direct and total control over the order of elaboration, and
28041 furthermore, checks need only be generated in cases which are rare
28042 and which the compiler can easily detect.
28043 The situation is more complex when separate compilation is taken into account.
28044 Consider the following:
28046 @smallexample @c ada
28050 function Sqrt (Arg : Float) return Float;
28053 package body Math is
28054 function Sqrt (Arg : Float) return Float is
28063 X : Float := Math.Sqrt (0.5);
28076 where @code{Main} is the main program. When this program is executed, the
28077 elaboration code must first be executed, and one of the jobs of the
28078 binder is to determine the order in which the units of a program are
28079 to be elaborated. In this case we have four units: the spec and body
28081 the spec of @code{Stuff} and the body of @code{Main}).
28082 In what order should the four separate sections of elaboration code
28085 There are some restrictions in the order of elaboration that the binder
28086 can choose. In particular, if unit U has a @code{with}
28087 for a package @code{X}, then you
28088 are assured that the spec of @code{X}
28089 is elaborated before U , but you are
28090 not assured that the body of @code{X}
28091 is elaborated before U.
28092 This means that in the above case, the binder is allowed to choose the
28103 but that's not good, because now the call to @code{Math.Sqrt}
28104 that happens during
28105 the elaboration of the @code{Stuff}
28106 spec happens before the body of @code{Math.Sqrt} is
28107 elaborated, and hence causes @code{Program_Error} exception to be raised.
28108 At first glance, one might say that the binder is misbehaving, because
28109 obviously you want to elaborate the body of something you @code{with}
28111 that is not a general rule that can be followed in all cases. Consider
28113 @smallexample @c ada
28116 package X is @dots{}
28118 package Y is @dots{}
28121 package body Y is @dots{}
28124 package body X is @dots{}
28130 This is a common arrangement, and, apart from the order of elaboration
28131 problems that might arise in connection with elaboration code, this works fine.
28132 A rule that says that you must first elaborate the body of anything you
28133 @code{with} cannot work in this case:
28134 the body of @code{X} @code{with}'s @code{Y},
28135 which means you would have to
28136 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28138 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28139 loop that cannot be broken.
28141 It is true that the binder can in many cases guess an order of elaboration
28142 that is unlikely to cause a @code{Program_Error}
28143 exception to be raised, and it tries to do so (in the
28144 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28146 elaborate the body of @code{Math} right after its spec, so all will be well).
28148 However, a program that blindly relies on the binder to be helpful can
28149 get into trouble, as we discussed in the previous sections, so
28151 provides a number of facilities for assisting the programmer in
28152 developing programs that are robust with respect to elaboration order.
28154 @node Default Behavior in GNAT - Ensuring Safety
28155 @section Default Behavior in GNAT - Ensuring Safety
28158 The default behavior in GNAT ensures elaboration safety. In its
28159 default mode GNAT implements the
28160 rule we previously described as the right approach. Let's restate it:
28164 @emph{If a unit has elaboration code that can directly or indirectly make a
28165 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28166 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28167 does not have pragma @code{Pure} or
28168 @code{Preelaborate}, then the client should have an
28169 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28171 @emph{In the case of instantiating a generic subprogram, it is always
28172 sufficient to have only an @code{Elaborate} pragma for the
28173 @code{with}'ed unit.}
28177 By following this rule a client is assured that calls and instantiations
28178 can be made without risk of an exception.
28180 In this mode GNAT traces all calls that are potentially made from
28181 elaboration code, and puts in any missing implicit @code{Elaborate}
28182 and @code{Elaborate_All} pragmas.
28183 The advantage of this approach is that no elaboration problems
28184 are possible if the binder can find an elaboration order that is
28185 consistent with these implicit @code{Elaborate} and
28186 @code{Elaborate_All} pragmas. The
28187 disadvantage of this approach is that no such order may exist.
28189 If the binder does not generate any diagnostics, then it means that it has
28190 found an elaboration order that is guaranteed to be safe. However, the binder
28191 may still be relying on implicitly generated @code{Elaborate} and
28192 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28195 If it is important to guarantee portability, then the compilations should
28198 (warn on elaboration problems) switch. This will cause warning messages
28199 to be generated indicating the missing @code{Elaborate} and
28200 @code{Elaborate_All} pragmas.
28201 Consider the following source program:
28203 @smallexample @c ada
28208 m : integer := k.r;
28215 where it is clear that there
28216 should be a pragma @code{Elaborate_All}
28217 for unit @code{k}. An implicit pragma will be generated, and it is
28218 likely that the binder will be able to honor it. However, if you want
28219 to port this program to some other Ada compiler than GNAT.
28220 it is safer to include the pragma explicitly in the source. If this
28221 unit is compiled with the
28223 switch, then the compiler outputs a warning:
28230 3. m : integer := k.r;
28232 >>> warning: call to "r" may raise Program_Error
28233 >>> warning: missing pragma Elaborate_All for "k"
28241 and these warnings can be used as a guide for supplying manually
28242 the missing pragmas. It is usually a bad idea to use this warning
28243 option during development. That's because it will warn you when
28244 you need to put in a pragma, but cannot warn you when it is time
28245 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28246 unnecessary dependencies and even false circularities.
28248 This default mode is more restrictive than the Ada Reference
28249 Manual, and it is possible to construct programs which will compile
28250 using the dynamic model described there, but will run into a
28251 circularity using the safer static model we have described.
28253 Of course any Ada compiler must be able to operate in a mode
28254 consistent with the requirements of the Ada Reference Manual,
28255 and in particular must have the capability of implementing the
28256 standard dynamic model of elaboration with run-time checks.
28258 In GNAT, this standard mode can be achieved either by the use of
28259 the @option{-gnatE} switch on the compiler (@command{gcc} or
28260 @command{gnatmake}) command, or by the use of the configuration pragma:
28262 @smallexample @c ada
28263 pragma Elaboration_Checks (RM);
28267 Either approach will cause the unit affected to be compiled using the
28268 standard dynamic run-time elaboration checks described in the Ada
28269 Reference Manual. The static model is generally preferable, since it
28270 is clearly safer to rely on compile and link time checks rather than
28271 run-time checks. However, in the case of legacy code, it may be
28272 difficult to meet the requirements of the static model. This
28273 issue is further discussed in
28274 @ref{What to Do If the Default Elaboration Behavior Fails}.
28276 Note that the static model provides a strict subset of the allowed
28277 behavior and programs of the Ada Reference Manual, so if you do
28278 adhere to the static model and no circularities exist,
28279 then you are assured that your program will
28280 work using the dynamic model, providing that you remove any
28281 pragma Elaborate statements from the source.
28283 @node Treatment of Pragma Elaborate
28284 @section Treatment of Pragma Elaborate
28285 @cindex Pragma Elaborate
28288 The use of @code{pragma Elaborate}
28289 should generally be avoided in Ada 95 and Ada 2005 programs,
28290 since there is no guarantee that transitive calls
28291 will be properly handled. Indeed at one point, this pragma was placed
28292 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28294 Now that's a bit restrictive. In practice, the case in which
28295 @code{pragma Elaborate} is useful is when the caller knows that there
28296 are no transitive calls, or that the called unit contains all necessary
28297 transitive @code{pragma Elaborate} statements, and legacy code often
28298 contains such uses.
28300 Strictly speaking the static mode in GNAT should ignore such pragmas,
28301 since there is no assurance at compile time that the necessary safety
28302 conditions are met. In practice, this would cause GNAT to be incompatible
28303 with correctly written Ada 83 code that had all necessary
28304 @code{pragma Elaborate} statements in place. Consequently, we made the
28305 decision that GNAT in its default mode will believe that if it encounters
28306 a @code{pragma Elaborate} then the programmer knows what they are doing,
28307 and it will trust that no elaboration errors can occur.
28309 The result of this decision is two-fold. First to be safe using the
28310 static mode, you should remove all @code{pragma Elaborate} statements.
28311 Second, when fixing circularities in existing code, you can selectively
28312 use @code{pragma Elaborate} statements to convince the static mode of
28313 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28316 When using the static mode with @option{-gnatwl}, any use of
28317 @code{pragma Elaborate} will generate a warning about possible
28320 @node Elaboration Issues for Library Tasks
28321 @section Elaboration Issues for Library Tasks
28322 @cindex Library tasks, elaboration issues
28323 @cindex Elaboration of library tasks
28326 In this section we examine special elaboration issues that arise for
28327 programs that declare library level tasks.
28329 Generally the model of execution of an Ada program is that all units are
28330 elaborated, and then execution of the program starts. However, the
28331 declaration of library tasks definitely does not fit this model. The
28332 reason for this is that library tasks start as soon as they are declared
28333 (more precisely, as soon as the statement part of the enclosing package
28334 body is reached), that is to say before elaboration
28335 of the program is complete. This means that if such a task calls a
28336 subprogram, or an entry in another task, the callee may or may not be
28337 elaborated yet, and in the standard
28338 Reference Manual model of dynamic elaboration checks, you can even
28339 get timing dependent Program_Error exceptions, since there can be
28340 a race between the elaboration code and the task code.
28342 The static model of elaboration in GNAT seeks to avoid all such
28343 dynamic behavior, by being conservative, and the conservative
28344 approach in this particular case is to assume that all the code
28345 in a task body is potentially executed at elaboration time if
28346 a task is declared at the library level.
28348 This can definitely result in unexpected circularities. Consider
28349 the following example
28351 @smallexample @c ada
28357 type My_Int is new Integer;
28359 function Ident (M : My_Int) return My_Int;
28363 package body Decls is
28364 task body Lib_Task is
28370 function Ident (M : My_Int) return My_Int is
28378 procedure Put_Val (Arg : Decls.My_Int);
28382 package body Utils is
28383 procedure Put_Val (Arg : Decls.My_Int) is
28385 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28392 Decls.Lib_Task.Start;
28397 If the above example is compiled in the default static elaboration
28398 mode, then a circularity occurs. The circularity comes from the call
28399 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28400 this call occurs in elaboration code, we need an implicit pragma
28401 @code{Elaborate_All} for @code{Utils}. This means that not only must
28402 the spec and body of @code{Utils} be elaborated before the body
28403 of @code{Decls}, but also the spec and body of any unit that is
28404 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28405 the body of @code{Decls}. This is the transitive implication of
28406 pragma @code{Elaborate_All} and it makes sense, because in general
28407 the body of @code{Put_Val} might have a call to something in a
28408 @code{with'ed} unit.
28410 In this case, the body of Utils (actually its spec) @code{with's}
28411 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28412 must be elaborated before itself, in case there is a call from the
28413 body of @code{Utils}.
28415 Here is the exact chain of events we are worrying about:
28419 In the body of @code{Decls} a call is made from within the body of a library
28420 task to a subprogram in the package @code{Utils}. Since this call may
28421 occur at elaboration time (given that the task is activated at elaboration
28422 time), we have to assume the worst, i.e., that the
28423 call does happen at elaboration time.
28426 This means that the body and spec of @code{Util} must be elaborated before
28427 the body of @code{Decls} so that this call does not cause an access before
28431 Within the body of @code{Util}, specifically within the body of
28432 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28436 One such @code{with}'ed package is package @code{Decls}, so there
28437 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28438 In fact there is such a call in this example, but we would have to
28439 assume that there was such a call even if it were not there, since
28440 we are not supposed to write the body of @code{Decls} knowing what
28441 is in the body of @code{Utils}; certainly in the case of the
28442 static elaboration model, the compiler does not know what is in
28443 other bodies and must assume the worst.
28446 This means that the spec and body of @code{Decls} must also be
28447 elaborated before we elaborate the unit containing the call, but
28448 that unit is @code{Decls}! This means that the body of @code{Decls}
28449 must be elaborated before itself, and that's a circularity.
28453 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28454 the body of @code{Decls} you will get a true Ada Reference Manual
28455 circularity that makes the program illegal.
28457 In practice, we have found that problems with the static model of
28458 elaboration in existing code often arise from library tasks, so
28459 we must address this particular situation.
28461 Note that if we compile and run the program above, using the dynamic model of
28462 elaboration (that is to say use the @option{-gnatE} switch),
28463 then it compiles, binds,
28464 links, and runs, printing the expected result of 2. Therefore in some sense
28465 the circularity here is only apparent, and we need to capture
28466 the properties of this program that distinguish it from other library-level
28467 tasks that have real elaboration problems.
28469 We have four possible answers to this question:
28474 Use the dynamic model of elaboration.
28476 If we use the @option{-gnatE} switch, then as noted above, the program works.
28477 Why is this? If we examine the task body, it is apparent that the task cannot
28479 @code{accept} statement until after elaboration has been completed, because
28480 the corresponding entry call comes from the main program, not earlier.
28481 This is why the dynamic model works here. But that's really giving
28482 up on a precise analysis, and we prefer to take this approach only if we cannot
28484 problem in any other manner. So let us examine two ways to reorganize
28485 the program to avoid the potential elaboration problem.
28488 Split library tasks into separate packages.
28490 Write separate packages, so that library tasks are isolated from
28491 other declarations as much as possible. Let us look at a variation on
28494 @smallexample @c ada
28502 package body Decls1 is
28503 task body Lib_Task is
28511 type My_Int is new Integer;
28512 function Ident (M : My_Int) return My_Int;
28516 package body Decls2 is
28517 function Ident (M : My_Int) return My_Int is
28525 procedure Put_Val (Arg : Decls2.My_Int);
28529 package body Utils is
28530 procedure Put_Val (Arg : Decls2.My_Int) is
28532 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28539 Decls1.Lib_Task.Start;
28544 All we have done is to split @code{Decls} into two packages, one
28545 containing the library task, and one containing everything else. Now
28546 there is no cycle, and the program compiles, binds, links and executes
28547 using the default static model of elaboration.
28550 Declare separate task types.
28552 A significant part of the problem arises because of the use of the
28553 single task declaration form. This means that the elaboration of
28554 the task type, and the elaboration of the task itself (i.e.@: the
28555 creation of the task) happen at the same time. A good rule
28556 of style in Ada is to always create explicit task types. By
28557 following the additional step of placing task objects in separate
28558 packages from the task type declaration, many elaboration problems
28559 are avoided. Here is another modified example of the example program:
28561 @smallexample @c ada
28563 task type Lib_Task_Type is
28567 type My_Int is new Integer;
28569 function Ident (M : My_Int) return My_Int;
28573 package body Decls is
28574 task body Lib_Task_Type is
28580 function Ident (M : My_Int) return My_Int is
28588 procedure Put_Val (Arg : Decls.My_Int);
28592 package body Utils is
28593 procedure Put_Val (Arg : Decls.My_Int) is
28595 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28601 Lib_Task : Decls.Lib_Task_Type;
28607 Declst.Lib_Task.Start;
28612 What we have done here is to replace the @code{task} declaration in
28613 package @code{Decls} with a @code{task type} declaration. Then we
28614 introduce a separate package @code{Declst} to contain the actual
28615 task object. This separates the elaboration issues for
28616 the @code{task type}
28617 declaration, which causes no trouble, from the elaboration issues
28618 of the task object, which is also unproblematic, since it is now independent
28619 of the elaboration of @code{Utils}.
28620 This separation of concerns also corresponds to
28621 a generally sound engineering principle of separating declarations
28622 from instances. This version of the program also compiles, binds, links,
28623 and executes, generating the expected output.
28626 Use No_Entry_Calls_In_Elaboration_Code restriction.
28627 @cindex No_Entry_Calls_In_Elaboration_Code
28629 The previous two approaches described how a program can be restructured
28630 to avoid the special problems caused by library task bodies. in practice,
28631 however, such restructuring may be difficult to apply to existing legacy code,
28632 so we must consider solutions that do not require massive rewriting.
28634 Let us consider more carefully why our original sample program works
28635 under the dynamic model of elaboration. The reason is that the code
28636 in the task body blocks immediately on the @code{accept}
28637 statement. Now of course there is nothing to prohibit elaboration
28638 code from making entry calls (for example from another library level task),
28639 so we cannot tell in isolation that
28640 the task will not execute the accept statement during elaboration.
28642 However, in practice it is very unusual to see elaboration code
28643 make any entry calls, and the pattern of tasks starting
28644 at elaboration time and then immediately blocking on @code{accept} or
28645 @code{select} statements is very common. What this means is that
28646 the compiler is being too pessimistic when it analyzes the
28647 whole package body as though it might be executed at elaboration
28650 If we know that the elaboration code contains no entry calls, (a very safe
28651 assumption most of the time, that could almost be made the default
28652 behavior), then we can compile all units of the program under control
28653 of the following configuration pragma:
28656 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28660 This pragma can be placed in the @file{gnat.adc} file in the usual
28661 manner. If we take our original unmodified program and compile it
28662 in the presence of a @file{gnat.adc} containing the above pragma,
28663 then once again, we can compile, bind, link, and execute, obtaining
28664 the expected result. In the presence of this pragma, the compiler does
28665 not trace calls in a task body, that appear after the first @code{accept}
28666 or @code{select} statement, and therefore does not report a potential
28667 circularity in the original program.
28669 The compiler will check to the extent it can that the above
28670 restriction is not violated, but it is not always possible to do a
28671 complete check at compile time, so it is important to use this
28672 pragma only if the stated restriction is in fact met, that is to say
28673 no task receives an entry call before elaboration of all units is completed.
28677 @node Mixing Elaboration Models
28678 @section Mixing Elaboration Models
28680 So far, we have assumed that the entire program is either compiled
28681 using the dynamic model or static model, ensuring consistency. It
28682 is possible to mix the two models, but rules have to be followed
28683 if this mixing is done to ensure that elaboration checks are not
28686 The basic rule is that @emph{a unit compiled with the static model cannot
28687 be @code{with'ed} by a unit compiled with the dynamic model}. The
28688 reason for this is that in the static model, a unit assumes that
28689 its clients guarantee to use (the equivalent of) pragma
28690 @code{Elaborate_All} so that no elaboration checks are required
28691 in inner subprograms, and this assumption is violated if the
28692 client is compiled with dynamic checks.
28694 The precise rule is as follows. A unit that is compiled with dynamic
28695 checks can only @code{with} a unit that meets at least one of the
28696 following criteria:
28701 The @code{with'ed} unit is itself compiled with dynamic elaboration
28702 checks (that is with the @option{-gnatE} switch.
28705 The @code{with'ed} unit is an internal GNAT implementation unit from
28706 the System, Interfaces, Ada, or GNAT hierarchies.
28709 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28712 The @code{with'ing} unit (that is the client) has an explicit pragma
28713 @code{Elaborate_All} for the @code{with'ed} unit.
28718 If this rule is violated, that is if a unit with dynamic elaboration
28719 checks @code{with's} a unit that does not meet one of the above four
28720 criteria, then the binder (@code{gnatbind}) will issue a warning
28721 similar to that in the following example:
28724 warning: "x.ads" has dynamic elaboration checks and with's
28725 warning: "y.ads" which has static elaboration checks
28729 These warnings indicate that the rule has been violated, and that as a result
28730 elaboration checks may be missed in the resulting executable file.
28731 This warning may be suppressed using the @option{-ws} binder switch
28732 in the usual manner.
28734 One useful application of this mixing rule is in the case of a subsystem
28735 which does not itself @code{with} units from the remainder of the
28736 application. In this case, the entire subsystem can be compiled with
28737 dynamic checks to resolve a circularity in the subsystem, while
28738 allowing the main application that uses this subsystem to be compiled
28739 using the more reliable default static model.
28741 @node What to Do If the Default Elaboration Behavior Fails
28742 @section What to Do If the Default Elaboration Behavior Fails
28745 If the binder cannot find an acceptable order, it outputs detailed
28746 diagnostics. For example:
28752 error: elaboration circularity detected
28753 info: "proc (body)" must be elaborated before "pack (body)"
28754 info: reason: Elaborate_All probably needed in unit "pack (body)"
28755 info: recompile "pack (body)" with -gnatwl
28756 info: for full details
28757 info: "proc (body)"
28758 info: is needed by its spec:
28759 info: "proc (spec)"
28760 info: which is withed by:
28761 info: "pack (body)"
28762 info: "pack (body)" must be elaborated before "proc (body)"
28763 info: reason: pragma Elaborate in unit "proc (body)"
28769 In this case we have a cycle that the binder cannot break. On the one
28770 hand, there is an explicit pragma Elaborate in @code{proc} for
28771 @code{pack}. This means that the body of @code{pack} must be elaborated
28772 before the body of @code{proc}. On the other hand, there is elaboration
28773 code in @code{pack} that calls a subprogram in @code{proc}. This means
28774 that for maximum safety, there should really be a pragma
28775 Elaborate_All in @code{pack} for @code{proc} which would require that
28776 the body of @code{proc} be elaborated before the body of
28777 @code{pack}. Clearly both requirements cannot be satisfied.
28778 Faced with a circularity of this kind, you have three different options.
28781 @item Fix the program
28782 The most desirable option from the point of view of long-term maintenance
28783 is to rearrange the program so that the elaboration problems are avoided.
28784 One useful technique is to place the elaboration code into separate
28785 child packages. Another is to move some of the initialization code to
28786 explicitly called subprograms, where the program controls the order
28787 of initialization explicitly. Although this is the most desirable option,
28788 it may be impractical and involve too much modification, especially in
28789 the case of complex legacy code.
28791 @item Perform dynamic checks
28792 If the compilations are done using the
28794 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28795 manner. Dynamic checks are generated for all calls that could possibly result
28796 in raising an exception. With this switch, the compiler does not generate
28797 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28798 exactly as specified in the @cite{Ada Reference Manual}.
28799 The binder will generate
28800 an executable program that may or may not raise @code{Program_Error}, and then
28801 it is the programmer's job to ensure that it does not raise an exception. Note
28802 that it is important to compile all units with the switch, it cannot be used
28805 @item Suppress checks
28806 The drawback of dynamic checks is that they generate a
28807 significant overhead at run time, both in space and time. If you
28808 are absolutely sure that your program cannot raise any elaboration
28809 exceptions, and you still want to use the dynamic elaboration model,
28810 then you can use the configuration pragma
28811 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28812 example this pragma could be placed in the @file{gnat.adc} file.
28814 @item Suppress checks selectively
28815 When you know that certain calls or instantiations in elaboration code cannot
28816 possibly lead to an elaboration error, and the binder nevertheless complains
28817 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28818 elaboration circularities, it is possible to remove those warnings locally and
28819 obtain a program that will bind. Clearly this can be unsafe, and it is the
28820 responsibility of the programmer to make sure that the resulting program has no
28821 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28822 used with different granularity to suppress warnings and break elaboration
28827 Place the pragma that names the called subprogram in the declarative part
28828 that contains the call.
28831 Place the pragma in the declarative part, without naming an entity. This
28832 disables warnings on all calls in the corresponding declarative region.
28835 Place the pragma in the package spec that declares the called subprogram,
28836 and name the subprogram. This disables warnings on all elaboration calls to
28840 Place the pragma in the package spec that declares the called subprogram,
28841 without naming any entity. This disables warnings on all elaboration calls to
28842 all subprograms declared in this spec.
28844 @item Use Pragma Elaborate
28845 As previously described in section @xref{Treatment of Pragma Elaborate},
28846 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28847 that no elaboration checks are required on calls to the designated unit.
28848 There may be cases in which the caller knows that no transitive calls
28849 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28850 case where @code{pragma Elaborate_All} would cause a circularity.
28854 These five cases are listed in order of decreasing safety, and therefore
28855 require increasing programmer care in their application. Consider the
28858 @smallexample @c adanocomment
28860 function F1 return Integer;
28865 function F2 return Integer;
28866 function Pure (x : integer) return integer;
28867 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28868 -- pragma Suppress (Elaboration_Check); -- (4)
28872 package body Pack1 is
28873 function F1 return Integer is
28877 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28880 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28881 -- pragma Suppress(Elaboration_Check); -- (2)
28883 X1 := Pack2.F2 + 1; -- Elab. call (2)
28888 package body Pack2 is
28889 function F2 return Integer is
28893 function Pure (x : integer) return integer is
28895 return x ** 3 - 3 * x;
28899 with Pack1, Ada.Text_IO;
28902 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28905 In the absence of any pragmas, an attempt to bind this program produces
28906 the following diagnostics:
28912 error: elaboration circularity detected
28913 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28914 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28915 info: recompile "pack1 (body)" with -gnatwl for full details
28916 info: "pack1 (body)"
28917 info: must be elaborated along with its spec:
28918 info: "pack1 (spec)"
28919 info: which is withed by:
28920 info: "pack2 (body)"
28921 info: which must be elaborated along with its spec:
28922 info: "pack2 (spec)"
28923 info: which is withed by:
28924 info: "pack1 (body)"
28927 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28928 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28929 F2 is safe, even though F2 calls F1, because the call appears after the
28930 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28931 remove the warning on the call. It is also possible to use pragma (2)
28932 because there are no other potentially unsafe calls in the block.
28935 The call to @code{Pure} is safe because this function does not depend on the
28936 state of @code{Pack2}. Therefore any call to this function is safe, and it
28937 is correct to place pragma (3) in the corresponding package spec.
28940 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28941 warnings on all calls to functions declared therein. Note that this is not
28942 necessarily safe, and requires more detailed examination of the subprogram
28943 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28944 be already elaborated.
28948 It is hard to generalize on which of these four approaches should be
28949 taken. Obviously if it is possible to fix the program so that the default
28950 treatment works, this is preferable, but this may not always be practical.
28951 It is certainly simple enough to use
28953 but the danger in this case is that, even if the GNAT binder
28954 finds a correct elaboration order, it may not always do so,
28955 and certainly a binder from another Ada compiler might not. A
28956 combination of testing and analysis (for which the warnings generated
28959 switch can be useful) must be used to ensure that the program is free
28960 of errors. One switch that is useful in this testing is the
28961 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28964 Normally the binder tries to find an order that has the best chance
28965 of avoiding elaboration problems. However, if this switch is used, the binder
28966 plays a devil's advocate role, and tries to choose the order that
28967 has the best chance of failing. If your program works even with this
28968 switch, then it has a better chance of being error free, but this is still
28971 For an example of this approach in action, consider the C-tests (executable
28972 tests) from the ACVC suite. If these are compiled and run with the default
28973 treatment, then all but one of them succeed without generating any error
28974 diagnostics from the binder. However, there is one test that fails, and
28975 this is not surprising, because the whole point of this test is to ensure
28976 that the compiler can handle cases where it is impossible to determine
28977 a correct order statically, and it checks that an exception is indeed
28978 raised at run time.
28980 This one test must be compiled and run using the
28982 switch, and then it passes. Alternatively, the entire suite can
28983 be run using this switch. It is never wrong to run with the dynamic
28984 elaboration switch if your code is correct, and we assume that the
28985 C-tests are indeed correct (it is less efficient, but efficiency is
28986 not a factor in running the ACVC tests.)
28988 @node Elaboration for Access-to-Subprogram Values
28989 @section Elaboration for Access-to-Subprogram Values
28990 @cindex Access-to-subprogram
28993 Access-to-subprogram types (introduced in Ada 95) complicate
28994 the handling of elaboration. The trouble is that it becomes
28995 impossible to tell at compile time which procedure
28996 is being called. This means that it is not possible for the binder
28997 to analyze the elaboration requirements in this case.
28999 If at the point at which the access value is created
29000 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
29001 the body of the subprogram is
29002 known to have been elaborated, then the access value is safe, and its use
29003 does not require a check. This may be achieved by appropriate arrangement
29004 of the order of declarations if the subprogram is in the current unit,
29005 or, if the subprogram is in another unit, by using pragma
29006 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
29007 on the referenced unit.
29009 If the referenced body is not known to have been elaborated at the point
29010 the access value is created, then any use of the access value must do a
29011 dynamic check, and this dynamic check will fail and raise a
29012 @code{Program_Error} exception if the body has not been elaborated yet.
29013 GNAT will generate the necessary checks, and in addition, if the
29015 switch is set, will generate warnings that such checks are required.
29017 The use of dynamic dispatching for tagged types similarly generates
29018 a requirement for dynamic checks, and premature calls to any primitive
29019 operation of a tagged type before the body of the operation has been
29020 elaborated, will result in the raising of @code{Program_Error}.
29022 @node Summary of Procedures for Elaboration Control
29023 @section Summary of Procedures for Elaboration Control
29024 @cindex Elaboration control
29027 First, compile your program with the default options, using none of
29028 the special elaboration control switches. If the binder successfully
29029 binds your program, then you can be confident that, apart from issues
29030 raised by the use of access-to-subprogram types and dynamic dispatching,
29031 the program is free of elaboration errors. If it is important that the
29032 program be portable, then use the
29034 switch to generate warnings about missing @code{Elaborate} or
29035 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29037 If the program fails to bind using the default static elaboration
29038 handling, then you can fix the program to eliminate the binder
29039 message, or recompile the entire program with the
29040 @option{-gnatE} switch to generate dynamic elaboration checks,
29041 and, if you are sure there really are no elaboration problems,
29042 use a global pragma @code{Suppress (Elaboration_Check)}.
29044 @node Other Elaboration Order Considerations
29045 @section Other Elaboration Order Considerations
29047 This section has been entirely concerned with the issue of finding a valid
29048 elaboration order, as defined by the Ada Reference Manual. In a case
29049 where several elaboration orders are valid, the task is to find one
29050 of the possible valid elaboration orders (and the static model in GNAT
29051 will ensure that this is achieved).
29053 The purpose of the elaboration rules in the Ada Reference Manual is to
29054 make sure that no entity is accessed before it has been elaborated. For
29055 a subprogram, this means that the spec and body must have been elaborated
29056 before the subprogram is called. For an object, this means that the object
29057 must have been elaborated before its value is read or written. A violation
29058 of either of these two requirements is an access before elaboration order,
29059 and this section has been all about avoiding such errors.
29061 In the case where more than one order of elaboration is possible, in the
29062 sense that access before elaboration errors are avoided, then any one of
29063 the orders is ``correct'' in the sense that it meets the requirements of
29064 the Ada Reference Manual, and no such error occurs.
29066 However, it may be the case for a given program, that there are
29067 constraints on the order of elaboration that come not from consideration
29068 of avoiding elaboration errors, but rather from extra-lingual logic
29069 requirements. Consider this example:
29071 @smallexample @c ada
29072 with Init_Constants;
29073 package Constants is
29078 package Init_Constants is
29079 procedure P; -- require a body
29080 end Init_Constants;
29083 package body Init_Constants is
29084 procedure P is begin null; end;
29088 end Init_Constants;
29092 Z : Integer := Constants.X + Constants.Y;
29096 with Text_IO; use Text_IO;
29099 Put_Line (Calc.Z'Img);
29104 In this example, there is more than one valid order of elaboration. For
29105 example both the following are correct orders:
29108 Init_Constants spec
29111 Init_Constants body
29116 Init_Constants spec
29117 Init_Constants body
29124 There is no language rule to prefer one or the other, both are correct
29125 from an order of elaboration point of view. But the programmatic effects
29126 of the two orders are very different. In the first, the elaboration routine
29127 of @code{Calc} initializes @code{Z} to zero, and then the main program
29128 runs with this value of zero. But in the second order, the elaboration
29129 routine of @code{Calc} runs after the body of Init_Constants has set
29130 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29133 One could perhaps by applying pretty clever non-artificial intelligence
29134 to the situation guess that it is more likely that the second order of
29135 elaboration is the one desired, but there is no formal linguistic reason
29136 to prefer one over the other. In fact in this particular case, GNAT will
29137 prefer the second order, because of the rule that bodies are elaborated
29138 as soon as possible, but it's just luck that this is what was wanted
29139 (if indeed the second order was preferred).
29141 If the program cares about the order of elaboration routines in a case like
29142 this, it is important to specify the order required. In this particular
29143 case, that could have been achieved by adding to the spec of Calc:
29145 @smallexample @c ada
29146 pragma Elaborate_All (Constants);
29150 which requires that the body (if any) and spec of @code{Constants},
29151 as well as the body and spec of any unit @code{with}'ed by
29152 @code{Constants} be elaborated before @code{Calc} is elaborated.
29154 Clearly no automatic method can always guess which alternative you require,
29155 and if you are working with legacy code that had constraints of this kind
29156 which were not properly specified by adding @code{Elaborate} or
29157 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29158 compilers can choose different orders.
29160 However, GNAT does attempt to diagnose the common situation where there
29161 are uninitialized variables in the visible part of a package spec, and the
29162 corresponding package body has an elaboration block that directly or
29163 indirectly initialized one or more of these variables. This is the situation
29164 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29165 a warning that suggests this addition if it detects this situation.
29167 The @code{gnatbind}
29168 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29169 out problems. This switch causes bodies to be elaborated as late as possible
29170 instead of as early as possible. In the example above, it would have forced
29171 the choice of the first elaboration order. If you get different results
29172 when using this switch, and particularly if one set of results is right,
29173 and one is wrong as far as you are concerned, it shows that you have some
29174 missing @code{Elaborate} pragmas. For the example above, we have the
29178 gnatmake -f -q main
29181 gnatmake -f -q main -bargs -p
29187 It is of course quite unlikely that both these results are correct, so
29188 it is up to you in a case like this to investigate the source of the
29189 difference, by looking at the two elaboration orders that are chosen,
29190 and figuring out which is correct, and then adding the necessary
29191 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29195 @c *******************************
29196 @node Conditional Compilation
29197 @appendix Conditional Compilation
29198 @c *******************************
29199 @cindex Conditional compilation
29202 It is often necessary to arrange for a single source program
29203 to serve multiple purposes, where it is compiled in different
29204 ways to achieve these different goals. Some examples of the
29205 need for this feature are
29208 @item Adapting a program to a different hardware environment
29209 @item Adapting a program to a different target architecture
29210 @item Turning debugging features on and off
29211 @item Arranging for a program to compile with different compilers
29215 In C, or C++, the typical approach would be to use the preprocessor
29216 that is defined as part of the language. The Ada language does not
29217 contain such a feature. This is not an oversight, but rather a very
29218 deliberate design decision, based on the experience that overuse of
29219 the preprocessing features in C and C++ can result in programs that
29220 are extremely difficult to maintain. For example, if we have ten
29221 switches that can be on or off, this means that there are a thousand
29222 separate programs, any one of which might not even be syntactically
29223 correct, and even if syntactically correct, the resulting program
29224 might not work correctly. Testing all combinations can quickly become
29227 Nevertheless, the need to tailor programs certainly exists, and in
29228 this Appendix we will discuss how this can
29229 be achieved using Ada in general, and GNAT in particular.
29232 * Use of Boolean Constants::
29233 * Debugging - A Special Case::
29234 * Conditionalizing Declarations::
29235 * Use of Alternative Implementations::
29239 @node Use of Boolean Constants
29240 @section Use of Boolean Constants
29243 In the case where the difference is simply which code
29244 sequence is executed, the cleanest solution is to use Boolean
29245 constants to control which code is executed.
29247 @smallexample @c ada
29249 FP_Initialize_Required : constant Boolean := True;
29251 if FP_Initialize_Required then
29258 Not only will the code inside the @code{if} statement not be executed if
29259 the constant Boolean is @code{False}, but it will also be completely
29260 deleted from the program.
29261 However, the code is only deleted after the @code{if} statement
29262 has been checked for syntactic and semantic correctness.
29263 (In contrast, with preprocessors the code is deleted before the
29264 compiler ever gets to see it, so it is not checked until the switch
29266 @cindex Preprocessors (contrasted with conditional compilation)
29268 Typically the Boolean constants will be in a separate package,
29271 @smallexample @c ada
29274 FP_Initialize_Required : constant Boolean := True;
29275 Reset_Available : constant Boolean := False;
29282 The @code{Config} package exists in multiple forms for the various targets,
29283 with an appropriate script selecting the version of @code{Config} needed.
29284 Then any other unit requiring conditional compilation can do a @code{with}
29285 of @code{Config} to make the constants visible.
29288 @node Debugging - A Special Case
29289 @section Debugging - A Special Case
29292 A common use of conditional code is to execute statements (for example
29293 dynamic checks, or output of intermediate results) under control of a
29294 debug switch, so that the debugging behavior can be turned on and off.
29295 This can be done using a Boolean constant to control whether the code
29298 @smallexample @c ada
29301 Put_Line ("got to the first stage!");
29309 @smallexample @c ada
29311 if Debugging and then Temperature > 999.0 then
29312 raise Temperature_Crazy;
29318 Since this is a common case, there are special features to deal with
29319 this in a convenient manner. For the case of tests, Ada 2005 has added
29320 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29321 @cindex pragma @code{Assert}
29322 on the @code{Assert} pragma that has always been available in GNAT, so this
29323 feature may be used with GNAT even if you are not using Ada 2005 features.
29324 The use of pragma @code{Assert} is described in
29325 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29326 example, the last test could be written:
29328 @smallexample @c ada
29329 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29335 @smallexample @c ada
29336 pragma Assert (Temperature <= 999.0);
29340 In both cases, if assertions are active and the temperature is excessive,
29341 the exception @code{Assert_Failure} will be raised, with the given string in
29342 the first case or a string indicating the location of the pragma in the second
29343 case used as the exception message.
29345 You can turn assertions on and off by using the @code{Assertion_Policy}
29347 @cindex pragma @code{Assertion_Policy}
29348 This is an Ada 2005 pragma which is implemented in all modes by
29349 GNAT, but only in the latest versions of GNAT which include Ada 2005
29350 capability. Alternatively, you can use the @option{-gnata} switch
29351 @cindex @option{-gnata} switch
29352 to enable assertions from the command line (this is recognized by all versions
29355 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29356 @code{Debug} can be used:
29357 @cindex pragma @code{Debug}
29359 @smallexample @c ada
29360 pragma Debug (Put_Line ("got to the first stage!"));
29364 If debug pragmas are enabled, the argument, which must be of the form of
29365 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29366 Only one call can be present, but of course a special debugging procedure
29367 containing any code you like can be included in the program and then
29368 called in a pragma @code{Debug} argument as needed.
29370 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29371 construct is that pragma @code{Debug} can appear in declarative contexts,
29372 such as at the very beginning of a procedure, before local declarations have
29375 Debug pragmas are enabled using either the @option{-gnata} switch that also
29376 controls assertions, or with a separate Debug_Policy pragma.
29377 @cindex pragma @code{Debug_Policy}
29378 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29379 in Ada 95 and Ada 83 programs as well), and is analogous to
29380 pragma @code{Assertion_Policy} to control assertions.
29382 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29383 and thus they can appear in @file{gnat.adc} if you are not using a
29384 project file, or in the file designated to contain configuration pragmas
29386 They then apply to all subsequent compilations. In practice the use of
29387 the @option{-gnata} switch is often the most convenient method of controlling
29388 the status of these pragmas.
29390 Note that a pragma is not a statement, so in contexts where a statement
29391 sequence is required, you can't just write a pragma on its own. You have
29392 to add a @code{null} statement.
29394 @smallexample @c ada
29397 @dots{} -- some statements
29399 pragma Assert (Num_Cases < 10);
29406 @node Conditionalizing Declarations
29407 @section Conditionalizing Declarations
29410 In some cases, it may be necessary to conditionalize declarations to meet
29411 different requirements. For example we might want a bit string whose length
29412 is set to meet some hardware message requirement.
29414 In some cases, it may be possible to do this using declare blocks controlled
29415 by conditional constants:
29417 @smallexample @c ada
29419 if Small_Machine then
29421 X : Bit_String (1 .. 10);
29427 X : Large_Bit_String (1 .. 1000);
29436 Note that in this approach, both declarations are analyzed by the
29437 compiler so this can only be used where both declarations are legal,
29438 even though one of them will not be used.
29440 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29441 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29442 that are parameterized by these constants. For example
29444 @smallexample @c ada
29447 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29453 If @code{Bits_Per_Word} is set to 32, this generates either
29455 @smallexample @c ada
29458 Field1 at 0 range 0 .. 32;
29464 for the big endian case, or
29466 @smallexample @c ada
29469 Field1 at 0 range 10 .. 32;
29475 for the little endian case. Since a powerful subset of Ada expression
29476 notation is usable for creating static constants, clever use of this
29477 feature can often solve quite difficult problems in conditionalizing
29478 compilation (note incidentally that in Ada 95, the little endian
29479 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29480 need to define this one yourself).
29483 @node Use of Alternative Implementations
29484 @section Use of Alternative Implementations
29487 In some cases, none of the approaches described above are adequate. This
29488 can occur for example if the set of declarations required is radically
29489 different for two different configurations.
29491 In this situation, the official Ada way of dealing with conditionalizing
29492 such code is to write separate units for the different cases. As long as
29493 this does not result in excessive duplication of code, this can be done
29494 without creating maintenance problems. The approach is to share common
29495 code as far as possible, and then isolate the code and declarations
29496 that are different. Subunits are often a convenient method for breaking
29497 out a piece of a unit that is to be conditionalized, with separate files
29498 for different versions of the subunit for different targets, where the
29499 build script selects the right one to give to the compiler.
29500 @cindex Subunits (and conditional compilation)
29502 As an example, consider a situation where a new feature in Ada 2005
29503 allows something to be done in a really nice way. But your code must be able
29504 to compile with an Ada 95 compiler. Conceptually you want to say:
29506 @smallexample @c ada
29509 @dots{} neat Ada 2005 code
29511 @dots{} not quite as neat Ada 95 code
29517 where @code{Ada_2005} is a Boolean constant.
29519 But this won't work when @code{Ada_2005} is set to @code{False},
29520 since the @code{then} clause will be illegal for an Ada 95 compiler.
29521 (Recall that although such unreachable code would eventually be deleted
29522 by the compiler, it still needs to be legal. If it uses features
29523 introduced in Ada 2005, it will be illegal in Ada 95.)
29525 So instead we write
29527 @smallexample @c ada
29528 procedure Insert is separate;
29532 Then we have two files for the subunit @code{Insert}, with the two sets of
29534 If the package containing this is called @code{File_Queries}, then we might
29538 @item @file{file_queries-insert-2005.adb}
29539 @item @file{file_queries-insert-95.adb}
29543 and the build script renames the appropriate file to
29546 file_queries-insert.adb
29550 and then carries out the compilation.
29552 This can also be done with project files' naming schemes. For example:
29554 @smallexample @c project
29555 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29559 Note also that with project files it is desirable to use a different extension
29560 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29561 conflict may arise through another commonly used feature: to declare as part
29562 of the project a set of directories containing all the sources obeying the
29563 default naming scheme.
29565 The use of alternative units is certainly feasible in all situations,
29566 and for example the Ada part of the GNAT run-time is conditionalized
29567 based on the target architecture using this approach. As a specific example,
29568 consider the implementation of the AST feature in VMS. There is one
29576 which is the same for all architectures, and three bodies:
29580 used for all non-VMS operating systems
29581 @item s-asthan-vms-alpha.adb
29582 used for VMS on the Alpha
29583 @item s-asthan-vms-ia64.adb
29584 used for VMS on the ia64
29588 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29589 this operating system feature is not available, and the two remaining
29590 versions interface with the corresponding versions of VMS to provide
29591 VMS-compatible AST handling. The GNAT build script knows the architecture
29592 and operating system, and automatically selects the right version,
29593 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29595 Another style for arranging alternative implementations is through Ada's
29596 access-to-subprogram facility.
29597 In case some functionality is to be conditionally included,
29598 you can declare an access-to-procedure variable @code{Ref} that is initialized
29599 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29601 In some library package, set @code{Ref} to @code{Proc'Access} for some
29602 procedure @code{Proc} that performs the relevant processing.
29603 The initialization only occurs if the library package is included in the
29605 The same idea can also be implemented using tagged types and dispatching
29609 @node Preprocessing
29610 @section Preprocessing
29611 @cindex Preprocessing
29614 Although it is quite possible to conditionalize code without the use of
29615 C-style preprocessing, as described earlier in this section, it is
29616 nevertheless convenient in some cases to use the C approach. Moreover,
29617 older Ada compilers have often provided some preprocessing capability,
29618 so legacy code may depend on this approach, even though it is not
29621 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29622 extent on the various preprocessors that have been used
29623 with legacy code on other compilers, to enable easier transition).
29625 The preprocessor may be used in two separate modes. It can be used quite
29626 separately from the compiler, to generate a separate output source file
29627 that is then fed to the compiler as a separate step. This is the
29628 @code{gnatprep} utility, whose use is fully described in
29629 @ref{Preprocessing Using gnatprep}.
29630 @cindex @code{gnatprep}
29632 The preprocessing language allows such constructs as
29636 #if DEBUG or PRIORITY > 4 then
29637 bunch of declarations
29639 completely different bunch of declarations
29645 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29646 defined either on the command line or in a separate file.
29648 The other way of running the preprocessor is even closer to the C style and
29649 often more convenient. In this approach the preprocessing is integrated into
29650 the compilation process. The compiler is fed the preprocessor input which
29651 includes @code{#if} lines etc, and then the compiler carries out the
29652 preprocessing internally and processes the resulting output.
29653 For more details on this approach, see @ref{Integrated Preprocessing}.
29656 @c *******************************
29657 @node Inline Assembler
29658 @appendix Inline Assembler
29659 @c *******************************
29662 If you need to write low-level software that interacts directly
29663 with the hardware, Ada provides two ways to incorporate assembly
29664 language code into your program. First, you can import and invoke
29665 external routines written in assembly language, an Ada feature fully
29666 supported by GNAT@. However, for small sections of code it may be simpler
29667 or more efficient to include assembly language statements directly
29668 in your Ada source program, using the facilities of the implementation-defined
29669 package @code{System.Machine_Code}, which incorporates the gcc
29670 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29671 including the following:
29674 @item No need to use non-Ada tools
29675 @item Consistent interface over different targets
29676 @item Automatic usage of the proper calling conventions
29677 @item Access to Ada constants and variables
29678 @item Definition of intrinsic routines
29679 @item Possibility of inlining a subprogram comprising assembler code
29680 @item Code optimizer can take Inline Assembler code into account
29683 This chapter presents a series of examples to show you how to use
29684 the Inline Assembler. Although it focuses on the Intel x86,
29685 the general approach applies also to other processors.
29686 It is assumed that you are familiar with Ada
29687 and with assembly language programming.
29690 * Basic Assembler Syntax::
29691 * A Simple Example of Inline Assembler::
29692 * Output Variables in Inline Assembler::
29693 * Input Variables in Inline Assembler::
29694 * Inlining Inline Assembler Code::
29695 * Other Asm Functionality::
29698 @c ---------------------------------------------------------------------------
29699 @node Basic Assembler Syntax
29700 @section Basic Assembler Syntax
29703 The assembler used by GNAT and gcc is based not on the Intel assembly
29704 language, but rather on a language that descends from the AT&T Unix
29705 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29706 The following table summarizes the main features of @emph{as} syntax
29707 and points out the differences from the Intel conventions.
29708 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29709 pre-processor) documentation for further information.
29712 @item Register names
29713 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29715 Intel: No extra punctuation; for example @code{eax}
29717 @item Immediate operand
29718 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29720 Intel: No extra punctuation; for example @code{4}
29723 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29725 Intel: No extra punctuation; for example @code{loc}
29727 @item Memory contents
29728 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29730 Intel: Square brackets; for example @code{[loc]}
29732 @item Register contents
29733 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29735 Intel: Square brackets; for example @code{[eax]}
29737 @item Hexadecimal numbers
29738 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29740 Intel: Trailing ``h''; for example @code{A0h}
29743 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29746 Intel: Implicit, deduced by assembler; for example @code{mov}
29748 @item Instruction repetition
29749 gcc / @emph{as}: Split into two lines; for example
29755 Intel: Keep on one line; for example @code{rep stosl}
29757 @item Order of operands
29758 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29760 Intel: Destination first; for example @code{mov eax, 4}
29763 @c ---------------------------------------------------------------------------
29764 @node A Simple Example of Inline Assembler
29765 @section A Simple Example of Inline Assembler
29768 The following example will generate a single assembly language statement,
29769 @code{nop}, which does nothing. Despite its lack of run-time effect,
29770 the example will be useful in illustrating the basics of
29771 the Inline Assembler facility.
29773 @smallexample @c ada
29775 with System.Machine_Code; use System.Machine_Code;
29776 procedure Nothing is
29783 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29784 here it takes one parameter, a @emph{template string} that must be a static
29785 expression and that will form the generated instruction.
29786 @code{Asm} may be regarded as a compile-time procedure that parses
29787 the template string and additional parameters (none here),
29788 from which it generates a sequence of assembly language instructions.
29790 The examples in this chapter will illustrate several of the forms
29791 for invoking @code{Asm}; a complete specification of the syntax
29792 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29795 Under the standard GNAT conventions, the @code{Nothing} procedure
29796 should be in a file named @file{nothing.adb}.
29797 You can build the executable in the usual way:
29801 However, the interesting aspect of this example is not its run-time behavior
29802 but rather the generated assembly code.
29803 To see this output, invoke the compiler as follows:
29805 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29807 where the options are:
29811 compile only (no bind or link)
29813 generate assembler listing
29814 @item -fomit-frame-pointer
29815 do not set up separate stack frames
29817 do not add runtime checks
29820 This gives a human-readable assembler version of the code. The resulting
29821 file will have the same name as the Ada source file, but with a @code{.s}
29822 extension. In our example, the file @file{nothing.s} has the following
29827 .file "nothing.adb"
29829 ___gnu_compiled_ada:
29832 .globl __ada_nothing
29844 The assembly code you included is clearly indicated by
29845 the compiler, between the @code{#APP} and @code{#NO_APP}
29846 delimiters. The character before the 'APP' and 'NOAPP'
29847 can differ on different targets. For example, GNU/Linux uses '#APP' while
29848 on NT you will see '/APP'.
29850 If you make a mistake in your assembler code (such as using the
29851 wrong size modifier, or using a wrong operand for the instruction) GNAT
29852 will report this error in a temporary file, which will be deleted when
29853 the compilation is finished. Generating an assembler file will help
29854 in such cases, since you can assemble this file separately using the
29855 @emph{as} assembler that comes with gcc.
29857 Assembling the file using the command
29860 as @file{nothing.s}
29863 will give you error messages whose lines correspond to the assembler
29864 input file, so you can easily find and correct any mistakes you made.
29865 If there are no errors, @emph{as} will generate an object file
29866 @file{nothing.out}.
29868 @c ---------------------------------------------------------------------------
29869 @node Output Variables in Inline Assembler
29870 @section Output Variables in Inline Assembler
29873 The examples in this section, showing how to access the processor flags,
29874 illustrate how to specify the destination operands for assembly language
29877 @smallexample @c ada
29879 with Interfaces; use Interfaces;
29880 with Ada.Text_IO; use Ada.Text_IO;
29881 with System.Machine_Code; use System.Machine_Code;
29882 procedure Get_Flags is
29883 Flags : Unsigned_32;
29886 Asm ("pushfl" & LF & HT & -- push flags on stack
29887 "popl %%eax" & LF & HT & -- load eax with flags
29888 "movl %%eax, %0", -- store flags in variable
29889 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29890 Put_Line ("Flags register:" & Flags'Img);
29895 In order to have a nicely aligned assembly listing, we have separated
29896 multiple assembler statements in the Asm template string with linefeed
29897 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29898 The resulting section of the assembly output file is:
29905 movl %eax, -40(%ebp)
29910 It would have been legal to write the Asm invocation as:
29913 Asm ("pushfl popl %%eax movl %%eax, %0")
29916 but in the generated assembler file, this would come out as:
29920 pushfl popl %eax movl %eax, -40(%ebp)
29924 which is not so convenient for the human reader.
29926 We use Ada comments
29927 at the end of each line to explain what the assembler instructions
29928 actually do. This is a useful convention.
29930 When writing Inline Assembler instructions, you need to precede each register
29931 and variable name with a percent sign. Since the assembler already requires
29932 a percent sign at the beginning of a register name, you need two consecutive
29933 percent signs for such names in the Asm template string, thus @code{%%eax}.
29934 In the generated assembly code, one of the percent signs will be stripped off.
29936 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29937 variables: operands you later define using @code{Input} or @code{Output}
29938 parameters to @code{Asm}.
29939 An output variable is illustrated in
29940 the third statement in the Asm template string:
29944 The intent is to store the contents of the eax register in a variable that can
29945 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29946 necessarily work, since the compiler might optimize by using a register
29947 to hold Flags, and the expansion of the @code{movl} instruction would not be
29948 aware of this optimization. The solution is not to store the result directly
29949 but rather to advise the compiler to choose the correct operand form;
29950 that is the purpose of the @code{%0} output variable.
29952 Information about the output variable is supplied in the @code{Outputs}
29953 parameter to @code{Asm}:
29955 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29958 The output is defined by the @code{Asm_Output} attribute of the target type;
29959 the general format is
29961 Type'Asm_Output (constraint_string, variable_name)
29964 The constraint string directs the compiler how
29965 to store/access the associated variable. In the example
29967 Unsigned_32'Asm_Output ("=m", Flags);
29969 the @code{"m"} (memory) constraint tells the compiler that the variable
29970 @code{Flags} should be stored in a memory variable, thus preventing
29971 the optimizer from keeping it in a register. In contrast,
29973 Unsigned_32'Asm_Output ("=r", Flags);
29975 uses the @code{"r"} (register) constraint, telling the compiler to
29976 store the variable in a register.
29978 If the constraint is preceded by the equal character (@strong{=}), it tells
29979 the compiler that the variable will be used to store data into it.
29981 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29982 allowing the optimizer to choose whatever it deems best.
29984 There are a fairly large number of constraints, but the ones that are
29985 most useful (for the Intel x86 processor) are the following:
29991 global (i.e.@: can be stored anywhere)
30009 use one of eax, ebx, ecx or edx
30011 use one of eax, ebx, ecx, edx, esi or edi
30014 The full set of constraints is described in the gcc and @emph{as}
30015 documentation; note that it is possible to combine certain constraints
30016 in one constraint string.
30018 You specify the association of an output variable with an assembler operand
30019 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30021 @smallexample @c ada
30023 Asm ("pushfl" & LF & HT & -- push flags on stack
30024 "popl %%eax" & LF & HT & -- load eax with flags
30025 "movl %%eax, %0", -- store flags in variable
30026 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30030 @code{%0} will be replaced in the expanded code by the appropriate operand,
30032 the compiler decided for the @code{Flags} variable.
30034 In general, you may have any number of output variables:
30037 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30039 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30040 of @code{Asm_Output} attributes
30044 @smallexample @c ada
30046 Asm ("movl %%eax, %0" & LF & HT &
30047 "movl %%ebx, %1" & LF & HT &
30049 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30050 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30051 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30055 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30056 in the Ada program.
30058 As a variation on the @code{Get_Flags} example, we can use the constraints
30059 string to direct the compiler to store the eax register into the @code{Flags}
30060 variable, instead of including the store instruction explicitly in the
30061 @code{Asm} template string:
30063 @smallexample @c ada
30065 with Interfaces; use Interfaces;
30066 with Ada.Text_IO; use Ada.Text_IO;
30067 with System.Machine_Code; use System.Machine_Code;
30068 procedure Get_Flags_2 is
30069 Flags : Unsigned_32;
30072 Asm ("pushfl" & LF & HT & -- push flags on stack
30073 "popl %%eax", -- save flags in eax
30074 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30075 Put_Line ("Flags register:" & Flags'Img);
30081 The @code{"a"} constraint tells the compiler that the @code{Flags}
30082 variable will come from the eax register. Here is the resulting code:
30090 movl %eax,-40(%ebp)
30095 The compiler generated the store of eax into Flags after
30096 expanding the assembler code.
30098 Actually, there was no need to pop the flags into the eax register;
30099 more simply, we could just pop the flags directly into the program variable:
30101 @smallexample @c ada
30103 with Interfaces; use Interfaces;
30104 with Ada.Text_IO; use Ada.Text_IO;
30105 with System.Machine_Code; use System.Machine_Code;
30106 procedure Get_Flags_3 is
30107 Flags : Unsigned_32;
30110 Asm ("pushfl" & LF & HT & -- push flags on stack
30111 "pop %0", -- save flags in Flags
30112 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30113 Put_Line ("Flags register:" & Flags'Img);
30118 @c ---------------------------------------------------------------------------
30119 @node Input Variables in Inline Assembler
30120 @section Input Variables in Inline Assembler
30123 The example in this section illustrates how to specify the source operands
30124 for assembly language statements.
30125 The program simply increments its input value by 1:
30127 @smallexample @c ada
30129 with Interfaces; use Interfaces;
30130 with Ada.Text_IO; use Ada.Text_IO;
30131 with System.Machine_Code; use System.Machine_Code;
30132 procedure Increment is
30134 function Incr (Value : Unsigned_32) return Unsigned_32 is
30135 Result : Unsigned_32;
30138 Inputs => Unsigned_32'Asm_Input ("a", Value),
30139 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30143 Value : Unsigned_32;
30147 Put_Line ("Value before is" & Value'Img);
30148 Value := Incr (Value);
30149 Put_Line ("Value after is" & Value'Img);
30154 The @code{Outputs} parameter to @code{Asm} specifies
30155 that the result will be in the eax register and that it is to be stored
30156 in the @code{Result} variable.
30158 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30159 but with an @code{Asm_Input} attribute.
30160 The @code{"="} constraint, indicating an output value, is not present.
30162 You can have multiple input variables, in the same way that you can have more
30163 than one output variable.
30165 The parameter count (%0, %1) etc, now starts at the first input
30166 statement, and continues with the output statements.
30167 When both parameters use the same variable, the
30168 compiler will treat them as the same %n operand, which is the case here.
30170 Just as the @code{Outputs} parameter causes the register to be stored into the
30171 target variable after execution of the assembler statements, so does the
30172 @code{Inputs} parameter cause its variable to be loaded into the register
30173 before execution of the assembler statements.
30175 Thus the effect of the @code{Asm} invocation is:
30177 @item load the 32-bit value of @code{Value} into eax
30178 @item execute the @code{incl %eax} instruction
30179 @item store the contents of eax into the @code{Result} variable
30182 The resulting assembler file (with @option{-O2} optimization) contains:
30185 _increment__incr.1:
30198 @c ---------------------------------------------------------------------------
30199 @node Inlining Inline Assembler Code
30200 @section Inlining Inline Assembler Code
30203 For a short subprogram such as the @code{Incr} function in the previous
30204 section, the overhead of the call and return (creating / deleting the stack
30205 frame) can be significant, compared to the amount of code in the subprogram
30206 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30207 which directs the compiler to expand invocations of the subprogram at the
30208 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30209 Here is the resulting program:
30211 @smallexample @c ada
30213 with Interfaces; use Interfaces;
30214 with Ada.Text_IO; use Ada.Text_IO;
30215 with System.Machine_Code; use System.Machine_Code;
30216 procedure Increment_2 is
30218 function Incr (Value : Unsigned_32) return Unsigned_32 is
30219 Result : Unsigned_32;
30222 Inputs => Unsigned_32'Asm_Input ("a", Value),
30223 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30226 pragma Inline (Increment);
30228 Value : Unsigned_32;
30232 Put_Line ("Value before is" & Value'Img);
30233 Value := Increment (Value);
30234 Put_Line ("Value after is" & Value'Img);
30239 Compile the program with both optimization (@option{-O2}) and inlining
30240 (@option{-gnatn}) enabled.
30242 The @code{Incr} function is still compiled as usual, but at the
30243 point in @code{Increment} where our function used to be called:
30248 call _increment__incr.1
30253 the code for the function body directly appears:
30266 thus saving the overhead of stack frame setup and an out-of-line call.
30268 @c ---------------------------------------------------------------------------
30269 @node Other Asm Functionality
30270 @section Other @code{Asm} Functionality
30273 This section describes two important parameters to the @code{Asm}
30274 procedure: @code{Clobber}, which identifies register usage;
30275 and @code{Volatile}, which inhibits unwanted optimizations.
30278 * The Clobber Parameter::
30279 * The Volatile Parameter::
30282 @c ---------------------------------------------------------------------------
30283 @node The Clobber Parameter
30284 @subsection The @code{Clobber} Parameter
30287 One of the dangers of intermixing assembly language and a compiled language
30288 such as Ada is that the compiler needs to be aware of which registers are
30289 being used by the assembly code. In some cases, such as the earlier examples,
30290 the constraint string is sufficient to indicate register usage (e.g.,
30292 the eax register). But more generally, the compiler needs an explicit
30293 identification of the registers that are used by the Inline Assembly
30296 Using a register that the compiler doesn't know about
30297 could be a side effect of an instruction (like @code{mull}
30298 storing its result in both eax and edx).
30299 It can also arise from explicit register usage in your
30300 assembly code; for example:
30303 Asm ("movl %0, %%ebx" & LF & HT &
30305 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30306 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30310 where the compiler (since it does not analyze the @code{Asm} template string)
30311 does not know you are using the ebx register.
30313 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30314 to identify the registers that will be used by your assembly code:
30318 Asm ("movl %0, %%ebx" & LF & HT &
30320 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30321 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30326 The Clobber parameter is a static string expression specifying the
30327 register(s) you are using. Note that register names are @emph{not} prefixed
30328 by a percent sign. Also, if more than one register is used then their names
30329 are separated by commas; e.g., @code{"eax, ebx"}
30331 The @code{Clobber} parameter has several additional uses:
30333 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30334 @item Use ``register'' name @code{memory} if you changed a memory location
30337 @c ---------------------------------------------------------------------------
30338 @node The Volatile Parameter
30339 @subsection The @code{Volatile} Parameter
30340 @cindex Volatile parameter
30343 Compiler optimizations in the presence of Inline Assembler may sometimes have
30344 unwanted effects. For example, when an @code{Asm} invocation with an input
30345 variable is inside a loop, the compiler might move the loading of the input
30346 variable outside the loop, regarding it as a one-time initialization.
30348 If this effect is not desired, you can disable such optimizations by setting
30349 the @code{Volatile} parameter to @code{True}; for example:
30351 @smallexample @c ada
30353 Asm ("movl %0, %%ebx" & LF & HT &
30355 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30356 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30362 By default, @code{Volatile} is set to @code{False} unless there is no
30363 @code{Outputs} parameter.
30365 Although setting @code{Volatile} to @code{True} prevents unwanted
30366 optimizations, it will also disable other optimizations that might be
30367 important for efficiency. In general, you should set @code{Volatile}
30368 to @code{True} only if the compiler's optimizations have created
30370 @c END OF INLINE ASSEMBLER CHAPTER
30371 @c ===============================
30373 @c ***********************************
30374 @c * Compatibility and Porting Guide *
30375 @c ***********************************
30376 @node Compatibility and Porting Guide
30377 @appendix Compatibility and Porting Guide
30380 This chapter describes the compatibility issues that may arise between
30381 GNAT and other Ada compilation systems (including those for Ada 83),
30382 and shows how GNAT can expedite porting
30383 applications developed in other Ada environments.
30386 * Compatibility with Ada 83::
30387 * Compatibility between Ada 95 and Ada 2005::
30388 * Implementation-dependent characteristics::
30389 * Compatibility with Other Ada Systems::
30390 * Representation Clauses::
30392 @c Brief section is only in non-VMS version
30393 @c Full chapter is in VMS version
30394 * Compatibility with HP Ada 83::
30397 * Transitioning to 64-Bit GNAT for OpenVMS::
30401 @node Compatibility with Ada 83
30402 @section Compatibility with Ada 83
30403 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30406 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30407 particular, the design intention was that the difficulties associated
30408 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30409 that occur when moving from one Ada 83 system to another.
30411 However, there are a number of points at which there are minor
30412 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30413 full details of these issues,
30414 and should be consulted for a complete treatment.
30416 following subsections treat the most likely issues to be encountered.
30419 * Legal Ada 83 programs that are illegal in Ada 95::
30420 * More deterministic semantics::
30421 * Changed semantics::
30422 * Other language compatibility issues::
30425 @node Legal Ada 83 programs that are illegal in Ada 95
30426 @subsection Legal Ada 83 programs that are illegal in Ada 95
30428 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30429 Ada 95 and thus also in Ada 2005:
30432 @item Character literals
30433 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30434 @code{Wide_Character} as a new predefined character type, some uses of
30435 character literals that were legal in Ada 83 are illegal in Ada 95.
30437 @smallexample @c ada
30438 for Char in 'A' .. 'Z' loop @dots{} end loop;
30442 The problem is that @code{'A'} and @code{'Z'} could be from either
30443 @code{Character} or @code{Wide_Character}. The simplest correction
30444 is to make the type explicit; e.g.:
30445 @smallexample @c ada
30446 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30449 @item New reserved words
30450 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30451 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30452 Existing Ada 83 code using any of these identifiers must be edited to
30453 use some alternative name.
30455 @item Freezing rules
30456 The rules in Ada 95 are slightly different with regard to the point at
30457 which entities are frozen, and representation pragmas and clauses are
30458 not permitted past the freeze point. This shows up most typically in
30459 the form of an error message complaining that a representation item
30460 appears too late, and the appropriate corrective action is to move
30461 the item nearer to the declaration of the entity to which it refers.
30463 A particular case is that representation pragmas
30466 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30468 cannot be applied to a subprogram body. If necessary, a separate subprogram
30469 declaration must be introduced to which the pragma can be applied.
30471 @item Optional bodies for library packages
30472 In Ada 83, a package that did not require a package body was nevertheless
30473 allowed to have one. This lead to certain surprises in compiling large
30474 systems (situations in which the body could be unexpectedly ignored by the
30475 binder). In Ada 95, if a package does not require a body then it is not
30476 permitted to have a body. To fix this problem, simply remove a redundant
30477 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30478 into the spec that makes the body required. One approach is to add a private
30479 part to the package declaration (if necessary), and define a parameterless
30480 procedure called @code{Requires_Body}, which must then be given a dummy
30481 procedure body in the package body, which then becomes required.
30482 Another approach (assuming that this does not introduce elaboration
30483 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30484 since one effect of this pragma is to require the presence of a package body.
30486 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30487 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30488 @code{Constraint_Error}.
30489 This means that it is illegal to have separate exception handlers for
30490 the two exceptions. The fix is simply to remove the handler for the
30491 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30492 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30494 @item Indefinite subtypes in generics
30495 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30496 as the actual for a generic formal private type, but then the instantiation
30497 would be illegal if there were any instances of declarations of variables
30498 of this type in the generic body. In Ada 95, to avoid this clear violation
30499 of the methodological principle known as the ``contract model'',
30500 the generic declaration explicitly indicates whether
30501 or not such instantiations are permitted. If a generic formal parameter
30502 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30503 type name, then it can be instantiated with indefinite types, but no
30504 stand-alone variables can be declared of this type. Any attempt to declare
30505 such a variable will result in an illegality at the time the generic is
30506 declared. If the @code{(<>)} notation is not used, then it is illegal
30507 to instantiate the generic with an indefinite type.
30508 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30509 It will show up as a compile time error, and
30510 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30513 @node More deterministic semantics
30514 @subsection More deterministic semantics
30518 Conversions from real types to integer types round away from 0. In Ada 83
30519 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30520 implementation freedom was intended to support unbiased rounding in
30521 statistical applications, but in practice it interfered with portability.
30522 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30523 is required. Numeric code may be affected by this change in semantics.
30524 Note, though, that this issue is no worse than already existed in Ada 83
30525 when porting code from one vendor to another.
30528 The Real-Time Annex introduces a set of policies that define the behavior of
30529 features that were implementation dependent in Ada 83, such as the order in
30530 which open select branches are executed.
30533 @node Changed semantics
30534 @subsection Changed semantics
30537 The worst kind of incompatibility is one where a program that is legal in
30538 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30539 possible in Ada 83. Fortunately this is extremely rare, but the one
30540 situation that you should be alert to is the change in the predefined type
30541 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30544 @item Range of type @code{Character}
30545 The range of @code{Standard.Character} is now the full 256 characters
30546 of Latin-1, whereas in most Ada 83 implementations it was restricted
30547 to 128 characters. Although some of the effects of
30548 this change will be manifest in compile-time rejection of legal
30549 Ada 83 programs it is possible for a working Ada 83 program to have
30550 a different effect in Ada 95, one that was not permitted in Ada 83.
30551 As an example, the expression
30552 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30553 delivers @code{255} as its value.
30554 In general, you should look at the logic of any
30555 character-processing Ada 83 program and see whether it needs to be adapted
30556 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30557 character handling package that may be relevant if code needs to be adapted
30558 to account for the additional Latin-1 elements.
30559 The desirable fix is to
30560 modify the program to accommodate the full character set, but in some cases
30561 it may be convenient to define a subtype or derived type of Character that
30562 covers only the restricted range.
30566 @node Other language compatibility issues
30567 @subsection Other language compatibility issues
30570 @item @option{-gnat83} switch
30571 All implementations of GNAT provide a switch that causes GNAT to operate
30572 in Ada 83 mode. In this mode, some but not all compatibility problems
30573 of the type described above are handled automatically. For example, the
30574 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30575 as identifiers as in Ada 83.
30577 in practice, it is usually advisable to make the necessary modifications
30578 to the program to remove the need for using this switch.
30579 See @ref{Compiling Different Versions of Ada}.
30581 @item Support for removed Ada 83 pragmas and attributes
30582 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30583 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30584 compilers are allowed, but not required, to implement these missing
30585 elements. In contrast with some other compilers, GNAT implements all
30586 such pragmas and attributes, eliminating this compatibility concern. These
30587 include @code{pragma Interface} and the floating point type attributes
30588 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30592 @node Compatibility between Ada 95 and Ada 2005
30593 @section Compatibility between Ada 95 and Ada 2005
30594 @cindex Compatibility between Ada 95 and Ada 2005
30597 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30598 a number of incompatibilities. Several are enumerated below;
30599 for a complete description please see the
30600 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30601 @cite{Rationale for Ada 2005}.
30604 @item New reserved words.
30605 The words @code{interface}, @code{overriding} and @code{synchronized} are
30606 reserved in Ada 2005.
30607 A pre-Ada 2005 program that uses any of these as an identifier will be
30610 @item New declarations in predefined packages.
30611 A number of packages in the predefined environment contain new declarations:
30612 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30613 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30614 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30615 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30616 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30617 If an Ada 95 program does a @code{with} and @code{use} of any of these
30618 packages, the new declarations may cause name clashes.
30620 @item Access parameters.
30621 A nondispatching subprogram with an access parameter cannot be renamed
30622 as a dispatching operation. This was permitted in Ada 95.
30624 @item Access types, discriminants, and constraints.
30625 Rule changes in this area have led to some incompatibilities; for example,
30626 constrained subtypes of some access types are not permitted in Ada 2005.
30628 @item Aggregates for limited types.
30629 The allowance of aggregates for limited types in Ada 2005 raises the
30630 possibility of ambiguities in legal Ada 95 programs, since additional types
30631 now need to be considered in expression resolution.
30633 @item Fixed-point multiplication and division.
30634 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30635 were legal in Ada 95 and invoked the predefined versions of these operations,
30637 The ambiguity may be resolved either by applying a type conversion to the
30638 expression, or by explicitly invoking the operation from package
30641 @item Return-by-reference types.
30642 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30643 can declare a function returning a value from an anonymous access type.
30647 @node Implementation-dependent characteristics
30648 @section Implementation-dependent characteristics
30650 Although the Ada language defines the semantics of each construct as
30651 precisely as practical, in some situations (for example for reasons of
30652 efficiency, or where the effect is heavily dependent on the host or target
30653 platform) the implementation is allowed some freedom. In porting Ada 83
30654 code to GNAT, you need to be aware of whether / how the existing code
30655 exercised such implementation dependencies. Such characteristics fall into
30656 several categories, and GNAT offers specific support in assisting the
30657 transition from certain Ada 83 compilers.
30660 * Implementation-defined pragmas::
30661 * Implementation-defined attributes::
30663 * Elaboration order::
30664 * Target-specific aspects::
30667 @node Implementation-defined pragmas
30668 @subsection Implementation-defined pragmas
30671 Ada compilers are allowed to supplement the language-defined pragmas, and
30672 these are a potential source of non-portability. All GNAT-defined pragmas
30673 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30674 Reference Manual}, and these include several that are specifically
30675 intended to correspond to other vendors' Ada 83 pragmas.
30676 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30677 For compatibility with HP Ada 83, GNAT supplies the pragmas
30678 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30679 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30680 and @code{Volatile}.
30681 Other relevant pragmas include @code{External} and @code{Link_With}.
30682 Some vendor-specific
30683 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30685 avoiding compiler rejection of units that contain such pragmas; they are not
30686 relevant in a GNAT context and hence are not otherwise implemented.
30688 @node Implementation-defined attributes
30689 @subsection Implementation-defined attributes
30691 Analogous to pragmas, the set of attributes may be extended by an
30692 implementation. All GNAT-defined attributes are described in
30693 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30694 Manual}, and these include several that are specifically intended
30695 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30696 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30697 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30701 @subsection Libraries
30703 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30704 code uses vendor-specific libraries then there are several ways to manage
30705 this in Ada 95 or Ada 2005:
30708 If the source code for the libraries (specs and bodies) are
30709 available, then the libraries can be migrated in the same way as the
30712 If the source code for the specs but not the bodies are
30713 available, then you can reimplement the bodies.
30715 Some features introduced by Ada 95 obviate the need for library support. For
30716 example most Ada 83 vendors supplied a package for unsigned integers. The
30717 Ada 95 modular type feature is the preferred way to handle this need, so
30718 instead of migrating or reimplementing the unsigned integer package it may
30719 be preferable to retrofit the application using modular types.
30722 @node Elaboration order
30723 @subsection Elaboration order
30725 The implementation can choose any elaboration order consistent with the unit
30726 dependency relationship. This freedom means that some orders can result in
30727 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30728 to invoke a subprogram its body has been elaborated, or to instantiate a
30729 generic before the generic body has been elaborated. By default GNAT
30730 attempts to choose a safe order (one that will not encounter access before
30731 elaboration problems) by implicitly inserting @code{Elaborate} or
30732 @code{Elaborate_All} pragmas where
30733 needed. However, this can lead to the creation of elaboration circularities
30734 and a resulting rejection of the program by gnatbind. This issue is
30735 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30736 In brief, there are several
30737 ways to deal with this situation:
30741 Modify the program to eliminate the circularities, e.g.@: by moving
30742 elaboration-time code into explicitly-invoked procedures
30744 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30745 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30746 @code{Elaborate_All}
30747 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30748 (by selectively suppressing elaboration checks via pragma
30749 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30752 @node Target-specific aspects
30753 @subsection Target-specific aspects
30755 Low-level applications need to deal with machine addresses, data
30756 representations, interfacing with assembler code, and similar issues. If
30757 such an Ada 83 application is being ported to different target hardware (for
30758 example where the byte endianness has changed) then you will need to
30759 carefully examine the program logic; the porting effort will heavily depend
30760 on the robustness of the original design. Moreover, Ada 95 (and thus
30761 Ada 2005) are sometimes
30762 incompatible with typical Ada 83 compiler practices regarding implicit
30763 packing, the meaning of the Size attribute, and the size of access values.
30764 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30766 @node Compatibility with Other Ada Systems
30767 @section Compatibility with Other Ada Systems
30770 If programs avoid the use of implementation dependent and
30771 implementation defined features, as documented in the @cite{Ada
30772 Reference Manual}, there should be a high degree of portability between
30773 GNAT and other Ada systems. The following are specific items which
30774 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30775 compilers, but do not affect porting code to GNAT@.
30776 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30777 the following issues may or may not arise for Ada 2005 programs
30778 when other compilers appear.)
30781 @item Ada 83 Pragmas and Attributes
30782 Ada 95 compilers are allowed, but not required, to implement the missing
30783 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30784 GNAT implements all such pragmas and attributes, eliminating this as
30785 a compatibility concern, but some other Ada 95 compilers reject these
30786 pragmas and attributes.
30788 @item Specialized Needs Annexes
30789 GNAT implements the full set of special needs annexes. At the
30790 current time, it is the only Ada 95 compiler to do so. This means that
30791 programs making use of these features may not be portable to other Ada
30792 95 compilation systems.
30794 @item Representation Clauses
30795 Some other Ada 95 compilers implement only the minimal set of
30796 representation clauses required by the Ada 95 reference manual. GNAT goes
30797 far beyond this minimal set, as described in the next section.
30800 @node Representation Clauses
30801 @section Representation Clauses
30804 The Ada 83 reference manual was quite vague in describing both the minimal
30805 required implementation of representation clauses, and also their precise
30806 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30807 minimal set of capabilities required is still quite limited.
30809 GNAT implements the full required set of capabilities in
30810 Ada 95 and Ada 2005, but also goes much further, and in particular
30811 an effort has been made to be compatible with existing Ada 83 usage to the
30812 greatest extent possible.
30814 A few cases exist in which Ada 83 compiler behavior is incompatible with
30815 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30816 intentional or accidental dependence on specific implementation dependent
30817 characteristics of these Ada 83 compilers. The following is a list of
30818 the cases most likely to arise in existing Ada 83 code.
30821 @item Implicit Packing
30822 Some Ada 83 compilers allowed a Size specification to cause implicit
30823 packing of an array or record. This could cause expensive implicit
30824 conversions for change of representation in the presence of derived
30825 types, and the Ada design intends to avoid this possibility.
30826 Subsequent AI's were issued to make it clear that such implicit
30827 change of representation in response to a Size clause is inadvisable,
30828 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30829 Reference Manuals as implementation advice that is followed by GNAT@.
30830 The problem will show up as an error
30831 message rejecting the size clause. The fix is simply to provide
30832 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30833 a Component_Size clause.
30835 @item Meaning of Size Attribute
30836 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30837 the minimal number of bits required to hold values of the type. For example,
30838 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30839 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30840 some 32 in this situation. This problem will usually show up as a compile
30841 time error, but not always. It is a good idea to check all uses of the
30842 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30843 Object_Size can provide a useful way of duplicating the behavior of
30844 some Ada 83 compiler systems.
30846 @item Size of Access Types
30847 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30848 and that therefore it will be the same size as a System.Address value. This
30849 assumption is true for GNAT in most cases with one exception. For the case of
30850 a pointer to an unconstrained array type (where the bounds may vary from one
30851 value of the access type to another), the default is to use a ``fat pointer'',
30852 which is represented as two separate pointers, one to the bounds, and one to
30853 the array. This representation has a number of advantages, including improved
30854 efficiency. However, it may cause some difficulties in porting existing Ada 83
30855 code which makes the assumption that, for example, pointers fit in 32 bits on
30856 a machine with 32-bit addressing.
30858 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30859 access types in this case (where the designated type is an unconstrained array
30860 type). These thin pointers are indeed the same size as a System.Address value.
30861 To specify a thin pointer, use a size clause for the type, for example:
30863 @smallexample @c ada
30864 type X is access all String;
30865 for X'Size use Standard'Address_Size;
30869 which will cause the type X to be represented using a single pointer.
30870 When using this representation, the bounds are right behind the array.
30871 This representation is slightly less efficient, and does not allow quite
30872 such flexibility in the use of foreign pointers or in using the
30873 Unrestricted_Access attribute to create pointers to non-aliased objects.
30874 But for any standard portable use of the access type it will work in
30875 a functionally correct manner and allow porting of existing code.
30876 Note that another way of forcing a thin pointer representation
30877 is to use a component size clause for the element size in an array,
30878 or a record representation clause for an access field in a record.
30882 @c This brief section is only in the non-VMS version
30883 @c The complete chapter on HP Ada is in the VMS version
30884 @node Compatibility with HP Ada 83
30885 @section Compatibility with HP Ada 83
30888 The VMS version of GNAT fully implements all the pragmas and attributes
30889 provided by HP Ada 83, as well as providing the standard HP Ada 83
30890 libraries, including Starlet. In addition, data layouts and parameter
30891 passing conventions are highly compatible. This means that porting
30892 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30893 most other porting efforts. The following are some of the most
30894 significant differences between GNAT and HP Ada 83.
30897 @item Default floating-point representation
30898 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30899 it is VMS format. GNAT does implement the necessary pragmas
30900 (Long_Float, Float_Representation) for changing this default.
30903 The package System in GNAT exactly corresponds to the definition in the
30904 Ada 95 reference manual, which means that it excludes many of the
30905 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30906 that contains the additional definitions, and a special pragma,
30907 Extend_System allows this package to be treated transparently as an
30908 extension of package System.
30911 The definitions provided by Aux_DEC are exactly compatible with those
30912 in the HP Ada 83 version of System, with one exception.
30913 HP Ada provides the following declarations:
30915 @smallexample @c ada
30916 TO_ADDRESS (INTEGER)
30917 TO_ADDRESS (UNSIGNED_LONGWORD)
30918 TO_ADDRESS (@i{universal_integer})
30922 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30923 an extension to Ada 83 not strictly compatible with the reference manual.
30924 In GNAT, we are constrained to be exactly compatible with the standard,
30925 and this means we cannot provide this capability. In HP Ada 83, the
30926 point of this definition is to deal with a call like:
30928 @smallexample @c ada
30929 TO_ADDRESS (16#12777#);
30933 Normally, according to the Ada 83 standard, one would expect this to be
30934 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30935 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30936 definition using @i{universal_integer} takes precedence.
30938 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30939 is not possible to be 100% compatible. Since there are many programs using
30940 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30941 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30942 declarations provided in the GNAT version of AUX_Dec are:
30944 @smallexample @c ada
30945 function To_Address (X : Integer) return Address;
30946 pragma Pure_Function (To_Address);
30948 function To_Address_Long (X : Unsigned_Longword)
30950 pragma Pure_Function (To_Address_Long);
30954 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30955 change the name to TO_ADDRESS_LONG@.
30957 @item Task_Id values
30958 The Task_Id values assigned will be different in the two systems, and GNAT
30959 does not provide a specified value for the Task_Id of the environment task,
30960 which in GNAT is treated like any other declared task.
30964 For full details on these and other less significant compatibility issues,
30965 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30966 Overview and Comparison on HP Platforms}.
30968 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30969 attributes are recognized, although only a subset of them can sensibly
30970 be implemented. The description of pragmas in @ref{Implementation
30971 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30972 indicates whether or not they are applicable to non-VMS systems.
30976 @node Transitioning to 64-Bit GNAT for OpenVMS
30977 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30980 This section is meant to assist users of pre-2006 @value{EDITION}
30981 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30982 the version of the GNAT technology supplied in 2006 and later for
30983 OpenVMS on both Alpha and I64.
30986 * Introduction to transitioning::
30987 * Migration of 32 bit code::
30988 * Taking advantage of 64 bit addressing::
30989 * Technical details::
30992 @node Introduction to transitioning
30993 @subsection Introduction
30996 64-bit @value{EDITION} for Open VMS has been designed to meet
31001 Providing a full conforming implementation of Ada 95 and Ada 2005
31004 Allowing maximum backward compatibility, thus easing migration of existing
31008 Supplying a path for exploiting the full 64-bit address range
31012 Ada's strong typing semantics has made it
31013 impractical to have different 32-bit and 64-bit modes. As soon as
31014 one object could possibly be outside the 32-bit address space, this
31015 would make it necessary for the @code{System.Address} type to be 64 bits.
31016 In particular, this would cause inconsistencies if 32-bit code is
31017 called from 64-bit code that raises an exception.
31019 This issue has been resolved by always using 64-bit addressing
31020 at the system level, but allowing for automatic conversions between
31021 32-bit and 64-bit addresses where required. Thus users who
31022 do not currently require 64-bit addressing capabilities, can
31023 recompile their code with only minimal changes (and indeed
31024 if the code is written in portable Ada, with no assumptions about
31025 the size of the @code{Address} type, then no changes at all are necessary).
31027 this approach provides a simple, gradual upgrade path to future
31028 use of larger memories than available for 32-bit systems.
31029 Also, newly written applications or libraries will by default
31030 be fully compatible with future systems exploiting 64-bit
31031 addressing capabilities.
31033 @ref{Migration of 32 bit code}, will focus on porting applications
31034 that do not require more than 2 GB of
31035 addressable memory. This code will be referred to as
31036 @emph{32-bit code}.
31037 For applications intending to exploit the full 64-bit address space,
31038 @ref{Taking advantage of 64 bit addressing},
31039 will consider further changes that may be required.
31040 Such code will be referred to below as @emph{64-bit code}.
31042 @node Migration of 32 bit code
31043 @subsection Migration of 32-bit code
31048 * Unchecked conversions::
31049 * Predefined constants::
31050 * Interfacing with C::
31051 * Experience with source compatibility::
31054 @node Address types
31055 @subsubsection Address types
31058 To solve the problem of mixing 64-bit and 32-bit addressing,
31059 while maintaining maximum backward compatibility, the following
31060 approach has been taken:
31064 @code{System.Address} always has a size of 64 bits
31067 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31071 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31072 a @code{Short_Address}
31073 may be used where an @code{Address} is required, and vice versa, without
31074 needing explicit type conversions.
31075 By virtue of the Open VMS parameter passing conventions,
31077 and exported subprograms that have 32-bit address parameters are
31078 compatible with those that have 64-bit address parameters.
31079 (See @ref{Making code 64 bit clean} for details.)
31081 The areas that may need attention are those where record types have
31082 been defined that contain components of the type @code{System.Address}, and
31083 where objects of this type are passed to code expecting a record layout with
31086 Different compilers on different platforms cannot be
31087 expected to represent the same type in the same way,
31088 since alignment constraints
31089 and other system-dependent properties affect the compiler's decision.
31090 For that reason, Ada code
31091 generally uses representation clauses to specify the expected
31092 layout where required.
31094 If such a representation clause uses 32 bits for a component having
31095 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31096 will detect that error and produce a specific diagnostic message.
31097 The developer should then determine whether the representation
31098 should be 64 bits or not and make either of two changes:
31099 change the size to 64 bits and leave the type as @code{System.Address}, or
31100 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31101 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31102 required in any code setting or accessing the field; the compiler will
31103 automatically perform any needed conversions between address
31107 @subsubsection Access types
31110 By default, objects designated by access values are always
31111 allocated in the 32-bit
31112 address space. Thus legacy code will never contain
31113 any objects that are not addressable with 32-bit addresses, and
31114 the compiler will never raise exceptions as result of mixing
31115 32-bit and 64-bit addresses.
31117 However, the access values themselves are represented in 64 bits, for optimum
31118 performance and future compatibility with 64-bit code. As was
31119 the case with @code{System.Address}, the compiler will give an error message
31120 if an object or record component has a representation clause that
31121 requires the access value to fit in 32 bits. In such a situation,
31122 an explicit size clause for the access type, specifying 32 bits,
31123 will have the desired effect.
31125 General access types (declared with @code{access all}) can never be
31126 32 bits, as values of such types must be able to refer to any object
31127 of the designated type,
31128 including objects residing outside the 32-bit address range.
31129 Existing Ada 83 code will not contain such type definitions,
31130 however, since general access types were introduced in Ada 95.
31132 @node Unchecked conversions
31133 @subsubsection Unchecked conversions
31136 In the case of an @code{Unchecked_Conversion} where the source type is a
31137 64-bit access type or the type @code{System.Address}, and the target
31138 type is a 32-bit type, the compiler will generate a warning.
31139 Even though the generated code will still perform the required
31140 conversions, it is highly recommended in these cases to use
31141 respectively a 32-bit access type or @code{System.Short_Address}
31142 as the source type.
31144 @node Predefined constants
31145 @subsubsection Predefined constants
31148 The following table shows the correspondence between pre-2006 versions of
31149 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31152 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31153 @item @b{Constant} @tab @b{Old} @tab @b{New}
31154 @item @code{System.Word_Size} @tab 32 @tab 64
31155 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31156 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31157 @item @code{System.Address_Size} @tab 32 @tab 64
31161 If you need to refer to the specific
31162 memory size of a 32-bit implementation, instead of the
31163 actual memory size, use @code{System.Short_Memory_Size}
31164 rather than @code{System.Memory_Size}.
31165 Similarly, references to @code{System.Address_Size} may need
31166 to be replaced by @code{System.Short_Address'Size}.
31167 The program @command{gnatfind} may be useful for locating
31168 references to the above constants, so that you can verify that they
31171 @node Interfacing with C
31172 @subsubsection Interfacing with C
31175 In order to minimize the impact of the transition to 64-bit addresses on
31176 legacy programs, some fundamental types in the @code{Interfaces.C}
31177 package hierarchy continue to be represented in 32 bits.
31178 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31179 This eases integration with the default HP C layout choices, for example
31180 as found in the system routines in @code{DECC$SHR.EXE}.
31181 Because of this implementation choice, the type fully compatible with
31182 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31183 Depending on the context the compiler will issue a
31184 warning or an error when type @code{Address} is used, alerting the user to a
31185 potential problem. Otherwise 32-bit programs that use
31186 @code{Interfaces.C} should normally not require code modifications
31188 The other issue arising with C interfacing concerns pragma @code{Convention}.
31189 For VMS 64-bit systems, there is an issue of the appropriate default size
31190 of C convention pointers in the absence of an explicit size clause. The HP
31191 C compiler can choose either 32 or 64 bits depending on compiler options.
31192 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31193 clause is given. This proves a better choice for porting 32-bit legacy
31194 applications. In order to have a 64-bit representation, it is necessary to
31195 specify a size representation clause. For example:
31197 @smallexample @c ada
31198 type int_star is access Interfaces.C.int;
31199 pragma Convention(C, int_star);
31200 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31203 @node Experience with source compatibility
31204 @subsubsection Experience with source compatibility
31207 The Security Server and STARLET on I64 provide an interesting ``test case''
31208 for source compatibility issues, since it is in such system code
31209 where assumptions about @code{Address} size might be expected to occur.
31210 Indeed, there were a small number of occasions in the Security Server
31211 file @file{jibdef.ads}
31212 where a representation clause for a record type specified
31213 32 bits for a component of type @code{Address}.
31214 All of these errors were detected by the compiler.
31215 The repair was obvious and immediate; to simply replace @code{Address} by
31216 @code{Short_Address}.
31218 In the case of STARLET, there were several record types that should
31219 have had representation clauses but did not. In these record types
31220 there was an implicit assumption that an @code{Address} value occupied
31222 These compiled without error, but their usage resulted in run-time error
31223 returns from STARLET system calls.
31224 Future GNAT technology enhancements may include a tool that detects and flags
31225 these sorts of potential source code porting problems.
31227 @c ****************************************
31228 @node Taking advantage of 64 bit addressing
31229 @subsection Taking advantage of 64-bit addressing
31232 * Making code 64 bit clean::
31233 * Allocating memory from the 64 bit storage pool::
31234 * Restrictions on use of 64 bit objects::
31235 * Using 64 bit storage pools by default::
31236 * General access types::
31237 * STARLET and other predefined libraries::
31240 @node Making code 64 bit clean
31241 @subsubsection Making code 64-bit clean
31244 In order to prevent problems that may occur when (parts of) a
31245 system start using memory outside the 32-bit address range,
31246 we recommend some additional guidelines:
31250 For imported subprograms that take parameters of the
31251 type @code{System.Address}, ensure that these subprograms can
31252 indeed handle 64-bit addresses. If not, or when in doubt,
31253 change the subprogram declaration to specify
31254 @code{System.Short_Address} instead.
31257 Resolve all warnings related to size mismatches in
31258 unchecked conversions. Failing to do so causes
31259 erroneous execution if the source object is outside
31260 the 32-bit address space.
31263 (optional) Explicitly use the 32-bit storage pool
31264 for access types used in a 32-bit context, or use
31265 generic access types where possible
31266 (@pxref{Restrictions on use of 64 bit objects}).
31270 If these rules are followed, the compiler will automatically insert
31271 any necessary checks to ensure that no addresses or access values
31272 passed to 32-bit code ever refer to objects outside the 32-bit
31274 Any attempt to do this will raise @code{Constraint_Error}.
31276 @node Allocating memory from the 64 bit storage pool
31277 @subsubsection Allocating memory from the 64-bit storage pool
31280 For any access type @code{T} that potentially requires memory allocations
31281 beyond the 32-bit address space,
31282 use the following representation clause:
31284 @smallexample @c ada
31285 for T'Storage_Pool use System.Pool_64;
31288 @node Restrictions on use of 64 bit objects
31289 @subsubsection Restrictions on use of 64-bit objects
31292 Taking the address of an object allocated from a 64-bit storage pool,
31293 and then passing this address to a subprogram expecting
31294 @code{System.Short_Address},
31295 or assigning it to a variable of type @code{Short_Address}, will cause
31296 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31297 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31298 no exception is raised and execution
31299 will become erroneous.
31301 @node Using 64 bit storage pools by default
31302 @subsubsection Using 64-bit storage pools by default
31305 In some cases it may be desirable to have the compiler allocate
31306 from 64-bit storage pools by default. This may be the case for
31307 libraries that are 64-bit clean, but may be used in both 32-bit
31308 and 64-bit contexts. For these cases the following configuration
31309 pragma may be specified:
31311 @smallexample @c ada
31312 pragma Pool_64_Default;
31316 Any code compiled in the context of this pragma will by default
31317 use the @code{System.Pool_64} storage pool. This default may be overridden
31318 for a specific access type @code{T} by the representation clause:
31320 @smallexample @c ada
31321 for T'Storage_Pool use System.Pool_32;
31325 Any object whose address may be passed to a subprogram with a
31326 @code{Short_Address} argument, or assigned to a variable of type
31327 @code{Short_Address}, needs to be allocated from this pool.
31329 @node General access types
31330 @subsubsection General access types
31333 Objects designated by access values from a
31334 general access type (declared with @code{access all}) are never allocated
31335 from a 64-bit storage pool. Code that uses general access types will
31336 accept objects allocated in either 32-bit or 64-bit address spaces,
31337 but never allocate objects outside the 32-bit address space.
31338 Using general access types ensures maximum compatibility with both
31339 32-bit and 64-bit code.
31341 @node STARLET and other predefined libraries
31342 @subsubsection STARLET and other predefined libraries
31345 All code that comes as part of GNAT is 64-bit clean, but the
31346 restrictions given in @ref{Restrictions on use of 64 bit objects},
31347 still apply. Look at the package
31348 specs to see in which contexts objects allocated
31349 in 64-bit address space are acceptable.
31351 @node Technical details
31352 @subsection Technical details
31355 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31356 Ada standard with respect to the type of @code{System.Address}. Previous
31357 versions of GNAT Pro have defined this type as private and implemented it as a
31360 In order to allow defining @code{System.Short_Address} as a proper subtype,
31361 and to match the implicit sign extension in parameter passing,
31362 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31363 visible (i.e., non-private) integer type.
31364 Standard operations on the type, such as the binary operators ``+'', ``-'',
31365 etc., that take @code{Address} operands and return an @code{Address} result,
31366 have been hidden by declaring these
31367 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31368 ambiguities that would otherwise result from overloading.
31369 (Note that, although @code{Address} is a visible integer type,
31370 good programming practice dictates against exploiting the type's
31371 integer properties such as literals, since this will compromise
31374 Defining @code{Address} as a visible integer type helps achieve
31375 maximum compatibility for existing Ada code,
31376 without sacrificing the capabilities of the 64-bit architecture.
31379 @c ************************************************
31381 @node Microsoft Windows Topics
31382 @appendix Microsoft Windows Topics
31388 This chapter describes topics that are specific to the Microsoft Windows
31389 platforms (NT, 2000, and XP Professional).
31392 * Using GNAT on Windows::
31393 * Using a network installation of GNAT::
31394 * CONSOLE and WINDOWS subsystems::
31395 * Temporary Files::
31396 * Mixed-Language Programming on Windows::
31397 * Windows Calling Conventions::
31398 * Introduction to Dynamic Link Libraries (DLLs)::
31399 * Using DLLs with GNAT::
31400 * Building DLLs with GNAT::
31401 * Building DLLs with GNAT Project files::
31402 * Building DLLs with gnatdll::
31403 * GNAT and Windows Resources::
31404 * Debugging a DLL::
31405 * Setting Stack Size from gnatlink::
31406 * Setting Heap Size from gnatlink::
31409 @node Using GNAT on Windows
31410 @section Using GNAT on Windows
31413 One of the strengths of the GNAT technology is that its tool set
31414 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31415 @code{gdb} debugger, etc.) is used in the same way regardless of the
31418 On Windows this tool set is complemented by a number of Microsoft-specific
31419 tools that have been provided to facilitate interoperability with Windows
31420 when this is required. With these tools:
31425 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31429 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31430 relocatable and non-relocatable DLLs are supported).
31433 You can build Ada DLLs for use in other applications. These applications
31434 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31435 relocatable and non-relocatable Ada DLLs are supported.
31438 You can include Windows resources in your Ada application.
31441 You can use or create COM/DCOM objects.
31445 Immediately below are listed all known general GNAT-for-Windows restrictions.
31446 Other restrictions about specific features like Windows Resources and DLLs
31447 are listed in separate sections below.
31452 It is not possible to use @code{GetLastError} and @code{SetLastError}
31453 when tasking, protected records, or exceptions are used. In these
31454 cases, in order to implement Ada semantics, the GNAT run-time system
31455 calls certain Win32 routines that set the last error variable to 0 upon
31456 success. It should be possible to use @code{GetLastError} and
31457 @code{SetLastError} when tasking, protected record, and exception
31458 features are not used, but it is not guaranteed to work.
31461 It is not possible to link against Microsoft libraries except for
31462 import libraries. The library must be built to be compatible with
31463 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31464 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31465 not be compatible with the GNAT runtime. Even if the library is
31466 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31469 When the compilation environment is located on FAT32 drives, users may
31470 experience recompilations of the source files that have not changed if
31471 Daylight Saving Time (DST) state has changed since the last time files
31472 were compiled. NTFS drives do not have this problem.
31475 No components of the GNAT toolset use any entries in the Windows
31476 registry. The only entries that can be created are file associations and
31477 PATH settings, provided the user has chosen to create them at installation
31478 time, as well as some minimal book-keeping information needed to correctly
31479 uninstall or integrate different GNAT products.
31482 @node Using a network installation of GNAT
31483 @section Using a network installation of GNAT
31486 Make sure the system on which GNAT is installed is accessible from the
31487 current machine, i.e., the install location is shared over the network.
31488 Shared resources are accessed on Windows by means of UNC paths, which
31489 have the format @code{\\server\sharename\path}
31491 In order to use such a network installation, simply add the UNC path of the
31492 @file{bin} directory of your GNAT installation in front of your PATH. For
31493 example, if GNAT is installed in @file{\GNAT} directory of a share location
31494 called @file{c-drive} on a machine @file{LOKI}, the following command will
31497 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31499 Be aware that every compilation using the network installation results in the
31500 transfer of large amounts of data across the network and will likely cause
31501 serious performance penalty.
31503 @node CONSOLE and WINDOWS subsystems
31504 @section CONSOLE and WINDOWS subsystems
31505 @cindex CONSOLE Subsystem
31506 @cindex WINDOWS Subsystem
31510 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31511 (which is the default subsystem) will always create a console when
31512 launching the application. This is not something desirable when the
31513 application has a Windows GUI. To get rid of this console the
31514 application must be using the @code{WINDOWS} subsystem. To do so
31515 the @option{-mwindows} linker option must be specified.
31518 $ gnatmake winprog -largs -mwindows
31521 @node Temporary Files
31522 @section Temporary Files
31523 @cindex Temporary files
31526 It is possible to control where temporary files gets created by setting
31527 the @env{TMP} environment variable. The file will be created:
31530 @item Under the directory pointed to by the @env{TMP} environment variable if
31531 this directory exists.
31533 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31534 set (or not pointing to a directory) and if this directory exists.
31536 @item Under the current working directory otherwise.
31540 This allows you to determine exactly where the temporary
31541 file will be created. This is particularly useful in networked
31542 environments where you may not have write access to some
31545 @node Mixed-Language Programming on Windows
31546 @section Mixed-Language Programming on Windows
31549 Developing pure Ada applications on Windows is no different than on
31550 other GNAT-supported platforms. However, when developing or porting an
31551 application that contains a mix of Ada and C/C++, the choice of your
31552 Windows C/C++ development environment conditions your overall
31553 interoperability strategy.
31555 If you use @command{gcc} to compile the non-Ada part of your application,
31556 there are no Windows-specific restrictions that affect the overall
31557 interoperability with your Ada code. If you plan to use
31558 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31559 the following limitations:
31563 You cannot link your Ada code with an object or library generated with
31564 Microsoft tools if these use the @code{.tls} section (Thread Local
31565 Storage section) since the GNAT linker does not yet support this section.
31568 You cannot link your Ada code with an object or library generated with
31569 Microsoft tools if these use I/O routines other than those provided in
31570 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31571 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31572 libraries can cause a conflict with @code{msvcrt.dll} services. For
31573 instance Visual C++ I/O stream routines conflict with those in
31578 If you do want to use the Microsoft tools for your non-Ada code and hit one
31579 of the above limitations, you have two choices:
31583 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31584 application. In this case, use the Microsoft or whatever environment to
31585 build the DLL and use GNAT to build your executable
31586 (@pxref{Using DLLs with GNAT}).
31589 Or you can encapsulate your Ada code in a DLL to be linked with the
31590 other part of your application. In this case, use GNAT to build the DLL
31591 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31592 environment to build your executable.
31595 @node Windows Calling Conventions
31596 @section Windows Calling Conventions
31601 * C Calling Convention::
31602 * Stdcall Calling Convention::
31603 * Win32 Calling Convention::
31604 * DLL Calling Convention::
31608 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31609 (callee), there are several ways to push @code{G}'s parameters on the
31610 stack and there are several possible scenarios to clean up the stack
31611 upon @code{G}'s return. A calling convention is an agreed upon software
31612 protocol whereby the responsibilities between the caller (@code{F}) and
31613 the callee (@code{G}) are clearly defined. Several calling conventions
31614 are available for Windows:
31618 @code{C} (Microsoft defined)
31621 @code{Stdcall} (Microsoft defined)
31624 @code{Win32} (GNAT specific)
31627 @code{DLL} (GNAT specific)
31630 @node C Calling Convention
31631 @subsection @code{C} Calling Convention
31634 This is the default calling convention used when interfacing to C/C++
31635 routines compiled with either @command{gcc} or Microsoft Visual C++.
31637 In the @code{C} calling convention subprogram parameters are pushed on the
31638 stack by the caller from right to left. The caller itself is in charge of
31639 cleaning up the stack after the call. In addition, the name of a routine
31640 with @code{C} calling convention is mangled by adding a leading underscore.
31642 The name to use on the Ada side when importing (or exporting) a routine
31643 with @code{C} calling convention is the name of the routine. For
31644 instance the C function:
31647 int get_val (long);
31651 should be imported from Ada as follows:
31653 @smallexample @c ada
31655 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31656 pragma Import (C, Get_Val, External_Name => "get_val");
31661 Note that in this particular case the @code{External_Name} parameter could
31662 have been omitted since, when missing, this parameter is taken to be the
31663 name of the Ada entity in lower case. When the @code{Link_Name} parameter
31664 is missing, as in the above example, this parameter is set to be the
31665 @code{External_Name} with a leading underscore.
31667 When importing a variable defined in C, you should always use the @code{C}
31668 calling convention unless the object containing the variable is part of a
31669 DLL (in which case you should use the @code{Stdcall} calling
31670 convention, @pxref{Stdcall Calling Convention}).
31672 @node Stdcall Calling Convention
31673 @subsection @code{Stdcall} Calling Convention
31676 This convention, which was the calling convention used for Pascal
31677 programs, is used by Microsoft for all the routines in the Win32 API for
31678 efficiency reasons. It must be used to import any routine for which this
31679 convention was specified.
31681 In the @code{Stdcall} calling convention subprogram parameters are pushed
31682 on the stack by the caller from right to left. The callee (and not the
31683 caller) is in charge of cleaning the stack on routine exit. In addition,
31684 the name of a routine with @code{Stdcall} calling convention is mangled by
31685 adding a leading underscore (as for the @code{C} calling convention) and a
31686 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31687 bytes) of the parameters passed to the routine.
31689 The name to use on the Ada side when importing a C routine with a
31690 @code{Stdcall} calling convention is the name of the C routine. The leading
31691 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31692 the compiler. For instance the Win32 function:
31695 @b{APIENTRY} int get_val (long);
31699 should be imported from Ada as follows:
31701 @smallexample @c ada
31703 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31704 pragma Import (Stdcall, Get_Val);
31705 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31710 As for the @code{C} calling convention, when the @code{External_Name}
31711 parameter is missing, it is taken to be the name of the Ada entity in lower
31712 case. If instead of writing the above import pragma you write:
31714 @smallexample @c ada
31716 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31717 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31722 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31723 of specifying the @code{External_Name} parameter you specify the
31724 @code{Link_Name} as in the following example:
31726 @smallexample @c ada
31728 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31729 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31734 then the imported routine is @code{retrieve_val}, that is, there is no
31735 decoration at all. No leading underscore and no Stdcall suffix
31736 @code{@@}@code{@var{nn}}.
31739 This is especially important as in some special cases a DLL's entry
31740 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31741 name generated for a call has it.
31744 It is also possible to import variables defined in a DLL by using an
31745 import pragma for a variable. As an example, if a DLL contains a
31746 variable defined as:
31753 then, to access this variable from Ada you should write:
31755 @smallexample @c ada
31757 My_Var : Interfaces.C.int;
31758 pragma Import (Stdcall, My_Var);
31763 Note that to ease building cross-platform bindings this convention
31764 will be handled as a @code{C} calling convention on non-Windows platforms.
31766 @node Win32 Calling Convention
31767 @subsection @code{Win32} Calling Convention
31770 This convention, which is GNAT-specific is fully equivalent to the
31771 @code{Stdcall} calling convention described above.
31773 @node DLL Calling Convention
31774 @subsection @code{DLL} Calling Convention
31777 This convention, which is GNAT-specific is fully equivalent to the
31778 @code{Stdcall} calling convention described above.
31780 @node Introduction to Dynamic Link Libraries (DLLs)
31781 @section Introduction to Dynamic Link Libraries (DLLs)
31785 A Dynamically Linked Library (DLL) is a library that can be shared by
31786 several applications running under Windows. A DLL can contain any number of
31787 routines and variables.
31789 One advantage of DLLs is that you can change and enhance them without
31790 forcing all the applications that depend on them to be relinked or
31791 recompiled. However, you should be aware than all calls to DLL routines are
31792 slower since, as you will understand below, such calls are indirect.
31794 To illustrate the remainder of this section, suppose that an application
31795 wants to use the services of a DLL @file{API.dll}. To use the services
31796 provided by @file{API.dll} you must statically link against the DLL or
31797 an import library which contains a jump table with an entry for each
31798 routine and variable exported by the DLL. In the Microsoft world this
31799 import library is called @file{API.lib}. When using GNAT this import
31800 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31801 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31803 After you have linked your application with the DLL or the import library
31804 and you run your application, here is what happens:
31808 Your application is loaded into memory.
31811 The DLL @file{API.dll} is mapped into the address space of your
31812 application. This means that:
31816 The DLL will use the stack of the calling thread.
31819 The DLL will use the virtual address space of the calling process.
31822 The DLL will allocate memory from the virtual address space of the calling
31826 Handles (pointers) can be safely exchanged between routines in the DLL
31827 routines and routines in the application using the DLL.
31831 The entries in the jump table (from the import library @file{libAPI.dll.a}
31832 or @file{API.lib} or automatically created when linking against a DLL)
31833 which is part of your application are initialized with the addresses
31834 of the routines and variables in @file{API.dll}.
31837 If present in @file{API.dll}, routines @code{DllMain} or
31838 @code{DllMainCRTStartup} are invoked. These routines typically contain
31839 the initialization code needed for the well-being of the routines and
31840 variables exported by the DLL.
31844 There is an additional point which is worth mentioning. In the Windows
31845 world there are two kind of DLLs: relocatable and non-relocatable
31846 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31847 in the target application address space. If the addresses of two
31848 non-relocatable DLLs overlap and these happen to be used by the same
31849 application, a conflict will occur and the application will run
31850 incorrectly. Hence, when possible, it is always preferable to use and
31851 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31852 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31853 User's Guide) removes the debugging symbols from the DLL but the DLL can
31854 still be relocated.
31856 As a side note, an interesting difference between Microsoft DLLs and
31857 Unix shared libraries, is the fact that on most Unix systems all public
31858 routines are exported by default in a Unix shared library, while under
31859 Windows it is possible (but not required) to list exported routines in
31860 a definition file (@pxref{The Definition File}).
31862 @node Using DLLs with GNAT
31863 @section Using DLLs with GNAT
31866 * Creating an Ada Spec for the DLL Services::
31867 * Creating an Import Library::
31871 To use the services of a DLL, say @file{API.dll}, in your Ada application
31876 The Ada spec for the routines and/or variables you want to access in
31877 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31878 header files provided with the DLL.
31881 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31882 mentioned an import library is a statically linked library containing the
31883 import table which will be filled at load time to point to the actual
31884 @file{API.dll} routines. Sometimes you don't have an import library for the
31885 DLL you want to use. The following sections will explain how to build
31886 one. Note that this is optional.
31889 The actual DLL, @file{API.dll}.
31893 Once you have all the above, to compile an Ada application that uses the
31894 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31895 you simply issue the command
31898 $ gnatmake my_ada_app -largs -lAPI
31902 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31903 tells the GNAT linker to look first for a library named @file{API.lib}
31904 (Microsoft-style name) and if not found for a libraries named
31905 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31906 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31907 contains the following pragma
31909 @smallexample @c ada
31910 pragma Linker_Options ("-lAPI");
31914 you do not have to add @option{-largs -lAPI} at the end of the
31915 @command{gnatmake} command.
31917 If any one of the items above is missing you will have to create it
31918 yourself. The following sections explain how to do so using as an
31919 example a fictitious DLL called @file{API.dll}.
31921 @node Creating an Ada Spec for the DLL Services
31922 @subsection Creating an Ada Spec for the DLL Services
31925 A DLL typically comes with a C/C++ header file which provides the
31926 definitions of the routines and variables exported by the DLL. The Ada
31927 equivalent of this header file is a package spec that contains definitions
31928 for the imported entities. If the DLL you intend to use does not come with
31929 an Ada spec you have to generate one such spec yourself. For example if
31930 the header file of @file{API.dll} is a file @file{api.h} containing the
31931 following two definitions:
31943 then the equivalent Ada spec could be:
31945 @smallexample @c ada
31948 with Interfaces.C.Strings;
31953 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31956 pragma Import (C, Get);
31957 pragma Import (DLL, Some_Var);
31964 Note that a variable is
31965 @strong{always imported with a Stdcall convention}. A function
31966 can have @code{C} or @code{Stdcall} convention.
31967 (@pxref{Windows Calling Conventions}).
31969 @node Creating an Import Library
31970 @subsection Creating an Import Library
31971 @cindex Import library
31974 * The Definition File::
31975 * GNAT-Style Import Library::
31976 * Microsoft-Style Import Library::
31980 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31981 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31982 with @file{API.dll} you can skip this section. You can also skip this
31983 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31984 as in this case it is possible to link directly against the
31985 DLL. Otherwise read on.
31987 @node The Definition File
31988 @subsubsection The Definition File
31989 @cindex Definition file
31993 As previously mentioned, and unlike Unix systems, the list of symbols
31994 that are exported from a DLL must be provided explicitly in Windows.
31995 The main goal of a definition file is precisely that: list the symbols
31996 exported by a DLL. A definition file (usually a file with a @code{.def}
31997 suffix) has the following structure:
32002 @r{[}LIBRARY @var{name}@r{]}
32003 @r{[}DESCRIPTION @var{string}@r{]}
32013 @item LIBRARY @var{name}
32014 This section, which is optional, gives the name of the DLL.
32016 @item DESCRIPTION @var{string}
32017 This section, which is optional, gives a description string that will be
32018 embedded in the import library.
32021 This section gives the list of exported symbols (procedures, functions or
32022 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32023 section of @file{API.def} looks like:
32037 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32038 (@pxref{Windows Calling Conventions}) for a Stdcall
32039 calling convention function in the exported symbols list.
32042 There can actually be other sections in a definition file, but these
32043 sections are not relevant to the discussion at hand.
32045 @node GNAT-Style Import Library
32046 @subsubsection GNAT-Style Import Library
32049 To create a static import library from @file{API.dll} with the GNAT tools
32050 you should proceed as follows:
32054 Create the definition file @file{API.def} (@pxref{The Definition File}).
32055 For that use the @code{dll2def} tool as follows:
32058 $ dll2def API.dll > API.def
32062 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32063 to standard output the list of entry points in the DLL. Note that if
32064 some routines in the DLL have the @code{Stdcall} convention
32065 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32066 suffix then you'll have to edit @file{api.def} to add it, and specify
32067 @option{-k} to @command{gnatdll} when creating the import library.
32070 Here are some hints to find the right @code{@@}@var{nn} suffix.
32074 If you have the Microsoft import library (.lib), it is possible to get
32075 the right symbols by using Microsoft @code{dumpbin} tool (see the
32076 corresponding Microsoft documentation for further details).
32079 $ dumpbin /exports api.lib
32083 If you have a message about a missing symbol at link time the compiler
32084 tells you what symbol is expected. You just have to go back to the
32085 definition file and add the right suffix.
32089 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32090 (@pxref{Using gnatdll}) as follows:
32093 $ gnatdll -e API.def -d API.dll
32097 @code{gnatdll} takes as input a definition file @file{API.def} and the
32098 name of the DLL containing the services listed in the definition file
32099 @file{API.dll}. The name of the static import library generated is
32100 computed from the name of the definition file as follows: if the
32101 definition file name is @var{xyz}@code{.def}, the import library name will
32102 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32103 @option{-e} could have been removed because the name of the definition
32104 file (before the ``@code{.def}'' suffix) is the same as the name of the
32105 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32108 @node Microsoft-Style Import Library
32109 @subsubsection Microsoft-Style Import Library
32112 With GNAT you can either use a GNAT-style or Microsoft-style import
32113 library. A Microsoft import library is needed only if you plan to make an
32114 Ada DLL available to applications developed with Microsoft
32115 tools (@pxref{Mixed-Language Programming on Windows}).
32117 To create a Microsoft-style import library for @file{API.dll} you
32118 should proceed as follows:
32122 Create the definition file @file{API.def} from the DLL. For this use either
32123 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32124 tool (see the corresponding Microsoft documentation for further details).
32127 Build the actual import library using Microsoft's @code{lib} utility:
32130 $ lib -machine:IX86 -def:API.def -out:API.lib
32134 If you use the above command the definition file @file{API.def} must
32135 contain a line giving the name of the DLL:
32142 See the Microsoft documentation for further details about the usage of
32146 @node Building DLLs with GNAT
32147 @section Building DLLs with GNAT
32148 @cindex DLLs, building
32151 This section explain how to build DLLs using the GNAT built-in DLL
32152 support. With the following procedure it is straight forward to build
32153 and use DLLs with GNAT.
32157 @item building object files
32159 The first step is to build all objects files that are to be included
32160 into the DLL. This is done by using the standard @command{gnatmake} tool.
32162 @item building the DLL
32164 To build the DLL you must use @command{gcc}'s @option{-shared}
32165 option. It is quite simple to use this method:
32168 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32171 It is important to note that in this case all symbols found in the
32172 object files are automatically exported. It is possible to restrict
32173 the set of symbols to export by passing to @command{gcc} a definition
32174 file, @pxref{The Definition File}. For example:
32177 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32180 If you use a definition file you must export the elaboration procedures
32181 for every package that required one. Elaboration procedures are named
32182 using the package name followed by "_E".
32184 @item preparing DLL to be used
32186 For the DLL to be used by client programs the bodies must be hidden
32187 from it and the .ali set with read-only attribute. This is very important
32188 otherwise GNAT will recompile all packages and will not actually use
32189 the code in the DLL. For example:
32193 $ copy *.ads *.ali api.dll apilib
32194 $ attrib +R apilib\*.ali
32199 At this point it is possible to use the DLL by directly linking
32200 against it. Note that you must use the GNAT shared runtime when using
32201 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32205 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32208 @node Building DLLs with GNAT Project files
32209 @section Building DLLs with GNAT Project files
32210 @cindex DLLs, building
32213 There is nothing specific to Windows in the build process.
32214 @pxref{Library Projects}.
32217 Due to a system limitation, it is not possible under Windows to create threads
32218 when inside the @code{DllMain} routine which is used for auto-initialization
32219 of shared libraries, so it is not possible to have library level tasks in SALs.
32221 @node Building DLLs with gnatdll
32222 @section Building DLLs with gnatdll
32223 @cindex DLLs, building
32226 * Limitations When Using Ada DLLs from Ada::
32227 * Exporting Ada Entities::
32228 * Ada DLLs and Elaboration::
32229 * Ada DLLs and Finalization::
32230 * Creating a Spec for Ada DLLs::
32231 * Creating the Definition File::
32236 Note that it is preferred to use the built-in GNAT DLL support
32237 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32238 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32240 This section explains how to build DLLs containing Ada code using
32241 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32242 remainder of this section.
32244 The steps required to build an Ada DLL that is to be used by Ada as well as
32245 non-Ada applications are as follows:
32249 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32250 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32251 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32252 skip this step if you plan to use the Ada DLL only from Ada applications.
32255 Your Ada code must export an initialization routine which calls the routine
32256 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32257 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32258 routine exported by the Ada DLL must be invoked by the clients of the DLL
32259 to initialize the DLL.
32262 When useful, the DLL should also export a finalization routine which calls
32263 routine @code{adafinal} generated by @command{gnatbind} to perform the
32264 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32265 The finalization routine exported by the Ada DLL must be invoked by the
32266 clients of the DLL when the DLL services are no further needed.
32269 You must provide a spec for the services exported by the Ada DLL in each
32270 of the programming languages to which you plan to make the DLL available.
32273 You must provide a definition file listing the exported entities
32274 (@pxref{The Definition File}).
32277 Finally you must use @code{gnatdll} to produce the DLL and the import
32278 library (@pxref{Using gnatdll}).
32282 Note that a relocatable DLL stripped using the @code{strip}
32283 binutils tool will not be relocatable anymore. To build a DLL without
32284 debug information pass @code{-largs -s} to @code{gnatdll}. This
32285 restriction does not apply to a DLL built using a Library Project.
32286 @pxref{Library Projects}.
32288 @node Limitations When Using Ada DLLs from Ada
32289 @subsection Limitations When Using Ada DLLs from Ada
32292 When using Ada DLLs from Ada applications there is a limitation users
32293 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32294 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32295 each Ada DLL includes the services of the GNAT run time that are necessary
32296 to the Ada code inside the DLL. As a result, when an Ada program uses an
32297 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32298 one in the main program.
32300 It is therefore not possible to exchange GNAT run-time objects between the
32301 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32302 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32305 It is completely safe to exchange plain elementary, array or record types,
32306 Windows object handles, etc.
32308 @node Exporting Ada Entities
32309 @subsection Exporting Ada Entities
32310 @cindex Export table
32313 Building a DLL is a way to encapsulate a set of services usable from any
32314 application. As a result, the Ada entities exported by a DLL should be
32315 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32316 any Ada name mangling. As an example here is an Ada package
32317 @code{API}, spec and body, exporting two procedures, a function, and a
32320 @smallexample @c ada
32323 with Interfaces.C; use Interfaces;
32325 Count : C.int := 0;
32326 function Factorial (Val : C.int) return C.int;
32328 procedure Initialize_API;
32329 procedure Finalize_API;
32330 -- Initialization & Finalization routines. More in the next section.
32332 pragma Export (C, Initialize_API);
32333 pragma Export (C, Finalize_API);
32334 pragma Export (C, Count);
32335 pragma Export (C, Factorial);
32341 @smallexample @c ada
32344 package body API is
32345 function Factorial (Val : C.int) return C.int is
32348 Count := Count + 1;
32349 for K in 1 .. Val loop
32355 procedure Initialize_API is
32357 pragma Import (C, Adainit);
32360 end Initialize_API;
32362 procedure Finalize_API is
32363 procedure Adafinal;
32364 pragma Import (C, Adafinal);
32374 If the Ada DLL you are building will only be used by Ada applications
32375 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32376 convention. As an example, the previous package could be written as
32379 @smallexample @c ada
32383 Count : Integer := 0;
32384 function Factorial (Val : Integer) return Integer;
32386 procedure Initialize_API;
32387 procedure Finalize_API;
32388 -- Initialization and Finalization routines.
32394 @smallexample @c ada
32397 package body API is
32398 function Factorial (Val : Integer) return Integer is
32399 Fact : Integer := 1;
32401 Count := Count + 1;
32402 for K in 1 .. Val loop
32409 -- The remainder of this package body is unchanged.
32416 Note that if you do not export the Ada entities with a @code{C} or
32417 @code{Stdcall} convention you will have to provide the mangled Ada names
32418 in the definition file of the Ada DLL
32419 (@pxref{Creating the Definition File}).
32421 @node Ada DLLs and Elaboration
32422 @subsection Ada DLLs and Elaboration
32423 @cindex DLLs and elaboration
32426 The DLL that you are building contains your Ada code as well as all the
32427 routines in the Ada library that are needed by it. The first thing a
32428 user of your DLL must do is elaborate the Ada code
32429 (@pxref{Elaboration Order Handling in GNAT}).
32431 To achieve this you must export an initialization routine
32432 (@code{Initialize_API} in the previous example), which must be invoked
32433 before using any of the DLL services. This elaboration routine must call
32434 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32435 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32436 @code{Initialize_Api} for an example. Note that the GNAT binder is
32437 automatically invoked during the DLL build process by the @code{gnatdll}
32438 tool (@pxref{Using gnatdll}).
32440 When a DLL is loaded, Windows systematically invokes a routine called
32441 @code{DllMain}. It would therefore be possible to call @code{adainit}
32442 directly from @code{DllMain} without having to provide an explicit
32443 initialization routine. Unfortunately, it is not possible to call
32444 @code{adainit} from the @code{DllMain} if your program has library level
32445 tasks because access to the @code{DllMain} entry point is serialized by
32446 the system (that is, only a single thread can execute ``through'' it at a
32447 time), which means that the GNAT run time will deadlock waiting for the
32448 newly created task to complete its initialization.
32450 @node Ada DLLs and Finalization
32451 @subsection Ada DLLs and Finalization
32452 @cindex DLLs and finalization
32455 When the services of an Ada DLL are no longer needed, the client code should
32456 invoke the DLL finalization routine, if available. The DLL finalization
32457 routine is in charge of releasing all resources acquired by the DLL. In the
32458 case of the Ada code contained in the DLL, this is achieved by calling
32459 routine @code{adafinal} generated by the GNAT binder
32460 (@pxref{Binding with Non-Ada Main Programs}).
32461 See the body of @code{Finalize_Api} for an
32462 example. As already pointed out the GNAT binder is automatically invoked
32463 during the DLL build process by the @code{gnatdll} tool
32464 (@pxref{Using gnatdll}).
32466 @node Creating a Spec for Ada DLLs
32467 @subsection Creating a Spec for Ada DLLs
32470 To use the services exported by the Ada DLL from another programming
32471 language (e.g.@: C), you have to translate the specs of the exported Ada
32472 entities in that language. For instance in the case of @code{API.dll},
32473 the corresponding C header file could look like:
32478 extern int *_imp__count;
32479 #define count (*_imp__count)
32480 int factorial (int);
32486 It is important to understand that when building an Ada DLL to be used by
32487 other Ada applications, you need two different specs for the packages
32488 contained in the DLL: one for building the DLL and the other for using
32489 the DLL. This is because the @code{DLL} calling convention is needed to
32490 use a variable defined in a DLL, but when building the DLL, the variable
32491 must have either the @code{Ada} or @code{C} calling convention. As an
32492 example consider a DLL comprising the following package @code{API}:
32494 @smallexample @c ada
32498 Count : Integer := 0;
32500 -- Remainder of the package omitted.
32507 After producing a DLL containing package @code{API}, the spec that
32508 must be used to import @code{API.Count} from Ada code outside of the
32511 @smallexample @c ada
32516 pragma Import (DLL, Count);
32522 @node Creating the Definition File
32523 @subsection Creating the Definition File
32526 The definition file is the last file needed to build the DLL. It lists
32527 the exported symbols. As an example, the definition file for a DLL
32528 containing only package @code{API} (where all the entities are exported
32529 with a @code{C} calling convention) is:
32544 If the @code{C} calling convention is missing from package @code{API},
32545 then the definition file contains the mangled Ada names of the above
32546 entities, which in this case are:
32555 api__initialize_api
32560 @node Using gnatdll
32561 @subsection Using @code{gnatdll}
32565 * gnatdll Example::
32566 * gnatdll behind the Scenes::
32571 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32572 and non-Ada sources that make up your DLL have been compiled.
32573 @code{gnatdll} is actually in charge of two distinct tasks: build the
32574 static import library for the DLL and the actual DLL. The form of the
32575 @code{gnatdll} command is
32579 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32584 where @var{list-of-files} is a list of ALI and object files. The object
32585 file list must be the exact list of objects corresponding to the non-Ada
32586 sources whose services are to be included in the DLL. The ALI file list
32587 must be the exact list of ALI files for the corresponding Ada sources
32588 whose services are to be included in the DLL. If @var{list-of-files} is
32589 missing, only the static import library is generated.
32592 You may specify any of the following switches to @code{gnatdll}:
32595 @item -a@ovar{address}
32596 @cindex @option{-a} (@code{gnatdll})
32597 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32598 specified the default address @var{0x11000000} will be used. By default,
32599 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32600 advise the reader to build relocatable DLL.
32602 @item -b @var{address}
32603 @cindex @option{-b} (@code{gnatdll})
32604 Set the relocatable DLL base address. By default the address is
32607 @item -bargs @var{opts}
32608 @cindex @option{-bargs} (@code{gnatdll})
32609 Binder options. Pass @var{opts} to the binder.
32611 @item -d @var{dllfile}
32612 @cindex @option{-d} (@code{gnatdll})
32613 @var{dllfile} is the name of the DLL. This switch must be present for
32614 @code{gnatdll} to do anything. The name of the generated import library is
32615 obtained algorithmically from @var{dllfile} as shown in the following
32616 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32617 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32618 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32619 as shown in the following example:
32620 if @var{dllfile} is @code{xyz.dll}, the definition
32621 file used is @code{xyz.def}.
32623 @item -e @var{deffile}
32624 @cindex @option{-e} (@code{gnatdll})
32625 @var{deffile} is the name of the definition file.
32628 @cindex @option{-g} (@code{gnatdll})
32629 Generate debugging information. This information is stored in the object
32630 file and copied from there to the final DLL file by the linker,
32631 where it can be read by the debugger. You must use the
32632 @option{-g} switch if you plan on using the debugger or the symbolic
32636 @cindex @option{-h} (@code{gnatdll})
32637 Help mode. Displays @code{gnatdll} switch usage information.
32640 @cindex @option{-I} (@code{gnatdll})
32641 Direct @code{gnatdll} to search the @var{dir} directory for source and
32642 object files needed to build the DLL.
32643 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32646 @cindex @option{-k} (@code{gnatdll})
32647 Removes the @code{@@}@var{nn} suffix from the import library's exported
32648 names, but keeps them for the link names. You must specify this
32649 option if you want to use a @code{Stdcall} function in a DLL for which
32650 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32651 of the Windows NT DLL for example. This option has no effect when
32652 @option{-n} option is specified.
32654 @item -l @var{file}
32655 @cindex @option{-l} (@code{gnatdll})
32656 The list of ALI and object files used to build the DLL are listed in
32657 @var{file}, instead of being given in the command line. Each line in
32658 @var{file} contains the name of an ALI or object file.
32661 @cindex @option{-n} (@code{gnatdll})
32662 No Import. Do not create the import library.
32665 @cindex @option{-q} (@code{gnatdll})
32666 Quiet mode. Do not display unnecessary messages.
32669 @cindex @option{-v} (@code{gnatdll})
32670 Verbose mode. Display extra information.
32672 @item -largs @var{opts}
32673 @cindex @option{-largs} (@code{gnatdll})
32674 Linker options. Pass @var{opts} to the linker.
32677 @node gnatdll Example
32678 @subsubsection @code{gnatdll} Example
32681 As an example the command to build a relocatable DLL from @file{api.adb}
32682 once @file{api.adb} has been compiled and @file{api.def} created is
32685 $ gnatdll -d api.dll api.ali
32689 The above command creates two files: @file{libapi.dll.a} (the import
32690 library) and @file{api.dll} (the actual DLL). If you want to create
32691 only the DLL, just type:
32694 $ gnatdll -d api.dll -n api.ali
32698 Alternatively if you want to create just the import library, type:
32701 $ gnatdll -d api.dll
32704 @node gnatdll behind the Scenes
32705 @subsubsection @code{gnatdll} behind the Scenes
32708 This section details the steps involved in creating a DLL. @code{gnatdll}
32709 does these steps for you. Unless you are interested in understanding what
32710 goes on behind the scenes, you should skip this section.
32712 We use the previous example of a DLL containing the Ada package @code{API},
32713 to illustrate the steps necessary to build a DLL. The starting point is a
32714 set of objects that will make up the DLL and the corresponding ALI
32715 files. In the case of this example this means that @file{api.o} and
32716 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32721 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32722 the information necessary to generate relocation information for the
32728 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32733 In addition to the base file, the @command{gnatlink} command generates an
32734 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32735 asks @command{gnatlink} to generate the routines @code{DllMain} and
32736 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32737 is loaded into memory.
32740 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32741 export table (@file{api.exp}). The export table contains the relocation
32742 information in a form which can be used during the final link to ensure
32743 that the Windows loader is able to place the DLL anywhere in memory.
32747 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32748 --output-exp api.exp
32753 @code{gnatdll} builds the base file using the new export table. Note that
32754 @command{gnatbind} must be called once again since the binder generated file
32755 has been deleted during the previous call to @command{gnatlink}.
32760 $ gnatlink api -o api.jnk api.exp -mdll
32761 -Wl,--base-file,api.base
32766 @code{gnatdll} builds the new export table using the new base file and
32767 generates the DLL import library @file{libAPI.dll.a}.
32771 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32772 --output-exp api.exp --output-lib libAPI.a
32777 Finally @code{gnatdll} builds the relocatable DLL using the final export
32783 $ gnatlink api api.exp -o api.dll -mdll
32788 @node Using dlltool
32789 @subsubsection Using @code{dlltool}
32792 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32793 DLLs and static import libraries. This section summarizes the most
32794 common @code{dlltool} switches. The form of the @code{dlltool} command
32798 $ dlltool @ovar{switches}
32802 @code{dlltool} switches include:
32805 @item --base-file @var{basefile}
32806 @cindex @option{--base-file} (@command{dlltool})
32807 Read the base file @var{basefile} generated by the linker. This switch
32808 is used to create a relocatable DLL.
32810 @item --def @var{deffile}
32811 @cindex @option{--def} (@command{dlltool})
32812 Read the definition file.
32814 @item --dllname @var{name}
32815 @cindex @option{--dllname} (@command{dlltool})
32816 Gives the name of the DLL. This switch is used to embed the name of the
32817 DLL in the static import library generated by @code{dlltool} with switch
32818 @option{--output-lib}.
32821 @cindex @option{-k} (@command{dlltool})
32822 Kill @code{@@}@var{nn} from exported names
32823 (@pxref{Windows Calling Conventions}
32824 for a discussion about @code{Stdcall}-style symbols.
32827 @cindex @option{--help} (@command{dlltool})
32828 Prints the @code{dlltool} switches with a concise description.
32830 @item --output-exp @var{exportfile}
32831 @cindex @option{--output-exp} (@command{dlltool})
32832 Generate an export file @var{exportfile}. The export file contains the
32833 export table (list of symbols in the DLL) and is used to create the DLL.
32835 @item --output-lib @var{libfile}
32836 @cindex @option{--output-lib} (@command{dlltool})
32837 Generate a static import library @var{libfile}.
32840 @cindex @option{-v} (@command{dlltool})
32843 @item --as @var{assembler-name}
32844 @cindex @option{--as} (@command{dlltool})
32845 Use @var{assembler-name} as the assembler. The default is @code{as}.
32848 @node GNAT and Windows Resources
32849 @section GNAT and Windows Resources
32850 @cindex Resources, windows
32853 * Building Resources::
32854 * Compiling Resources::
32855 * Using Resources::
32859 Resources are an easy way to add Windows specific objects to your
32860 application. The objects that can be added as resources include:
32889 This section explains how to build, compile and use resources.
32891 @node Building Resources
32892 @subsection Building Resources
32893 @cindex Resources, building
32896 A resource file is an ASCII file. By convention resource files have an
32897 @file{.rc} extension.
32898 The easiest way to build a resource file is to use Microsoft tools
32899 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32900 @code{dlgedit.exe} to build dialogs.
32901 It is always possible to build an @file{.rc} file yourself by writing a
32904 It is not our objective to explain how to write a resource file. A
32905 complete description of the resource script language can be found in the
32906 Microsoft documentation.
32908 @node Compiling Resources
32909 @subsection Compiling Resources
32912 @cindex Resources, compiling
32915 This section describes how to build a GNAT-compatible (COFF) object file
32916 containing the resources. This is done using the Resource Compiler
32917 @code{windres} as follows:
32920 $ windres -i myres.rc -o myres.o
32924 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32925 file. You can specify an alternate preprocessor (usually named
32926 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32927 parameter. A list of all possible options may be obtained by entering
32928 the command @code{windres} @option{--help}.
32930 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32931 to produce a @file{.res} file (binary resource file). See the
32932 corresponding Microsoft documentation for further details. In this case
32933 you need to use @code{windres} to translate the @file{.res} file to a
32934 GNAT-compatible object file as follows:
32937 $ windres -i myres.res -o myres.o
32940 @node Using Resources
32941 @subsection Using Resources
32942 @cindex Resources, using
32945 To include the resource file in your program just add the
32946 GNAT-compatible object file for the resource(s) to the linker
32947 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32951 $ gnatmake myprog -largs myres.o
32954 @node Debugging a DLL
32955 @section Debugging a DLL
32956 @cindex DLL debugging
32959 * Program and DLL Both Built with GCC/GNAT::
32960 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32964 Debugging a DLL is similar to debugging a standard program. But
32965 we have to deal with two different executable parts: the DLL and the
32966 program that uses it. We have the following four possibilities:
32970 The program and the DLL are built with @code{GCC/GNAT}.
32972 The program is built with foreign tools and the DLL is built with
32975 The program is built with @code{GCC/GNAT} and the DLL is built with
32981 In this section we address only cases one and two above.
32982 There is no point in trying to debug
32983 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32984 information in it. To do so you must use a debugger compatible with the
32985 tools suite used to build the DLL.
32987 @node Program and DLL Both Built with GCC/GNAT
32988 @subsection Program and DLL Both Built with GCC/GNAT
32991 This is the simplest case. Both the DLL and the program have @code{GDB}
32992 compatible debugging information. It is then possible to break anywhere in
32993 the process. Let's suppose here that the main procedure is named
32994 @code{ada_main} and that in the DLL there is an entry point named
32998 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32999 program must have been built with the debugging information (see GNAT -g
33000 switch). Here are the step-by-step instructions for debugging it:
33003 @item Launch @code{GDB} on the main program.
33009 @item Start the program and stop at the beginning of the main procedure
33016 This step is required to be able to set a breakpoint inside the DLL. As long
33017 as the program is not run, the DLL is not loaded. This has the
33018 consequence that the DLL debugging information is also not loaded, so it is not
33019 possible to set a breakpoint in the DLL.
33021 @item Set a breakpoint inside the DLL
33024 (gdb) break ada_dll
33031 At this stage a breakpoint is set inside the DLL. From there on
33032 you can use the standard approach to debug the whole program
33033 (@pxref{Running and Debugging Ada Programs}).
33036 @c This used to work, probably because the DLLs were non-relocatable
33037 @c keep this section around until the problem is sorted out.
33039 To break on the @code{DllMain} routine it is not possible to follow
33040 the procedure above. At the time the program stop on @code{ada_main}
33041 the @code{DllMain} routine as already been called. Either you can use
33042 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33045 @item Launch @code{GDB} on the main program.
33051 @item Load DLL symbols
33054 (gdb) add-sym api.dll
33057 @item Set a breakpoint inside the DLL
33060 (gdb) break ada_dll.adb:45
33063 Note that at this point it is not possible to break using the routine symbol
33064 directly as the program is not yet running. The solution is to break
33065 on the proper line (break in @file{ada_dll.adb} line 45).
33067 @item Start the program
33076 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33077 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33080 * Debugging the DLL Directly::
33081 * Attaching to a Running Process::
33085 In this case things are slightly more complex because it is not possible to
33086 start the main program and then break at the beginning to load the DLL and the
33087 associated DLL debugging information. It is not possible to break at the
33088 beginning of the program because there is no @code{GDB} debugging information,
33089 and therefore there is no direct way of getting initial control. This
33090 section addresses this issue by describing some methods that can be used
33091 to break somewhere in the DLL to debug it.
33094 First suppose that the main procedure is named @code{main} (this is for
33095 example some C code built with Microsoft Visual C) and that there is a
33096 DLL named @code{test.dll} containing an Ada entry point named
33100 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33101 been built with debugging information (see GNAT -g option).
33103 @node Debugging the DLL Directly
33104 @subsubsection Debugging the DLL Directly
33108 Find out the executable starting address
33111 $ objdump --file-header main.exe
33114 The starting address is reported on the last line. For example:
33117 main.exe: file format pei-i386
33118 architecture: i386, flags 0x0000010a:
33119 EXEC_P, HAS_DEBUG, D_PAGED
33120 start address 0x00401010
33124 Launch the debugger on the executable.
33131 Set a breakpoint at the starting address, and launch the program.
33134 $ (gdb) break *0x00401010
33138 The program will stop at the given address.
33141 Set a breakpoint on a DLL subroutine.
33144 (gdb) break ada_dll.adb:45
33147 Or if you want to break using a symbol on the DLL, you need first to
33148 select the Ada language (language used by the DLL).
33151 (gdb) set language ada
33152 (gdb) break ada_dll
33156 Continue the program.
33163 This will run the program until it reaches the breakpoint that has been
33164 set. From that point you can use the standard way to debug a program
33165 as described in (@pxref{Running and Debugging Ada Programs}).
33170 It is also possible to debug the DLL by attaching to a running process.
33172 @node Attaching to a Running Process
33173 @subsubsection Attaching to a Running Process
33174 @cindex DLL debugging, attach to process
33177 With @code{GDB} it is always possible to debug a running process by
33178 attaching to it. It is possible to debug a DLL this way. The limitation
33179 of this approach is that the DLL must run long enough to perform the
33180 attach operation. It may be useful for instance to insert a time wasting
33181 loop in the code of the DLL to meet this criterion.
33185 @item Launch the main program @file{main.exe}.
33191 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33192 that the process PID for @file{main.exe} is 208.
33200 @item Attach to the running process to be debugged.
33206 @item Load the process debugging information.
33209 (gdb) symbol-file main.exe
33212 @item Break somewhere in the DLL.
33215 (gdb) break ada_dll
33218 @item Continue process execution.
33227 This last step will resume the process execution, and stop at
33228 the breakpoint we have set. From there you can use the standard
33229 approach to debug a program as described in
33230 (@pxref{Running and Debugging Ada Programs}).
33232 @node Setting Stack Size from gnatlink
33233 @section Setting Stack Size from @command{gnatlink}
33236 It is possible to specify the program stack size at link time. On modern
33237 versions of Windows, starting with XP, this is mostly useful to set the size of
33238 the main stack (environment task). The other task stacks are set with pragma
33239 Storage_Size or with the @command{gnatbind -d} command.
33241 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33242 reserve size of individual tasks, the link-time stack size applies to all
33243 tasks, and pragma Storage_Size has no effect.
33244 In particular, Stack Overflow checks are made against this
33245 link-time specified size.
33247 This setting can be done with
33248 @command{gnatlink} using either:
33252 @item using @option{-Xlinker} linker option
33255 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33258 This sets the stack reserve size to 0x10000 bytes and the stack commit
33259 size to 0x1000 bytes.
33261 @item using @option{-Wl} linker option
33264 $ gnatlink hello -Wl,--stack=0x1000000
33267 This sets the stack reserve size to 0x1000000 bytes. Note that with
33268 @option{-Wl} option it is not possible to set the stack commit size
33269 because the coma is a separator for this option.
33273 @node Setting Heap Size from gnatlink
33274 @section Setting Heap Size from @command{gnatlink}
33277 Under Windows systems, it is possible to specify the program heap size from
33278 @command{gnatlink} using either:
33282 @item using @option{-Xlinker} linker option
33285 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33288 This sets the heap reserve size to 0x10000 bytes and the heap commit
33289 size to 0x1000 bytes.
33291 @item using @option{-Wl} linker option
33294 $ gnatlink hello -Wl,--heap=0x1000000
33297 This sets the heap reserve size to 0x1000000 bytes. Note that with
33298 @option{-Wl} option it is not possible to set the heap commit size
33299 because the coma is a separator for this option.
33305 @c **********************************
33306 @c * GNU Free Documentation License *
33307 @c **********************************
33309 @c GNU Free Documentation License
33311 @node Index,,GNU Free Documentation License, Top
33317 @c Put table of contents at end, otherwise it precedes the "title page" in
33318 @c the .txt version
33319 @c Edit the pdf file to move the contents to the beginning, after the title