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
12 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
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 1.3 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
110 @c Status as of November 2009:
111 @c Unfortunately texi2pdf and texi2html treat the trailing "@c"
112 @c differently, and faulty output is produced by one or the other
113 @c depending on whether the "@c" is present or absent.
114 @c As a result, the @ovar macro is not used, and all invocations
115 @c of the @ovar macro have been expanded inline.
118 @settitle @value{EDITION} User's Guide @value{PLATFORM}
119 @dircategory GNU Ada tools
121 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
124 @include gcc-common.texi
126 @setchapternewpage odd
131 @title @value{EDITION} User's Guide
135 @titlefont{@i{@value{PLATFORM}}}
141 @subtitle GNAT, The GNU Ada Compiler
146 @vskip 0pt plus 1filll
153 @node Top, About This Guide, (dir), (dir)
154 @top @value{EDITION} User's Guide
157 @value{EDITION} User's Guide @value{PLATFORM}
160 GNAT, The GNU Ada Compiler@*
161 GCC version @value{version-GCC}@*
168 * Getting Started with GNAT::
169 * The GNAT Compilation Model::
170 * Compiling Using gcc::
171 * Binding Using gnatbind::
172 * Linking Using gnatlink::
173 * The GNAT Make Program gnatmake::
174 * Improving Performance::
175 * Renaming Files Using gnatchop::
176 * Configuration Pragmas::
177 * Handling Arbitrary File Naming Conventions Using gnatname::
178 * GNAT Project Manager::
179 * Tools Supporting Project Files::
180 * The Cross-Referencing Tools gnatxref and gnatfind::
181 * The GNAT Pretty-Printer gnatpp::
182 * The GNAT Metric Tool gnatmetric::
183 * File Name Krunching Using gnatkr::
184 * Preprocessing Using gnatprep::
186 * The GNAT Run-Time Library Builder gnatlbr::
188 * The GNAT Library Browser gnatls::
189 * Cleaning Up Using gnatclean::
191 * GNAT and Libraries::
192 * Using the GNU make Utility::
194 * Memory Management Issues::
195 * Stack Related Facilities::
196 * Verifying Properties Using gnatcheck::
197 * Creating Sample Bodies Using gnatstub::
198 * Generating Ada Bindings for C and C++ headers::
199 * Other Utility Programs::
200 * Running and Debugging Ada Programs::
202 * Code Coverage and Profiling::
205 * Compatibility with HP Ada::
207 * Platform-Specific Information for the Run-Time Libraries::
208 * Example of Binder Output File::
209 * Elaboration Order Handling in GNAT::
210 * Conditional Compilation::
212 * Compatibility and Porting Guide::
214 * Microsoft Windows Topics::
216 * GNU Free Documentation License::
219 --- The Detailed Node Listing ---
223 * What This Guide Contains::
224 * What You Should Know before Reading This Guide::
225 * Related Information::
228 Getting Started with GNAT
231 * Running a Simple Ada Program::
232 * Running a Program with Multiple Units::
233 * Using the gnatmake Utility::
235 * Editing with Emacs::
238 * Introduction to GPS::
241 The GNAT Compilation Model
243 * Source Representation::
244 * Foreign Language Representation::
245 * File Naming Rules::
246 * Using Other File Names::
247 * Alternative File Naming Schemes::
248 * Generating Object Files::
249 * Source Dependencies::
250 * The Ada Library Information Files::
251 * Binding an Ada Program::
252 * Mixed Language Programming::
254 * Building Mixed Ada & C++ Programs::
255 * Comparison between GNAT and C/C++ Compilation Models::
257 * Comparison between GNAT and Conventional Ada Library Models::
259 * Placement of temporary files::
262 Foreign Language Representation
265 * Other 8-Bit Codes::
266 * Wide Character Encodings::
268 Compiling Ada Programs With gcc
270 * Compiling Programs::
272 * Search Paths and the Run-Time Library (RTL)::
273 * Order of Compilation Issues::
278 * Output and Error Message Control::
279 * Warning Message Control::
280 * Debugging and Assertion Control::
281 * Validity Checking::
284 * Using gcc for Syntax Checking::
285 * Using gcc for Semantic Checking::
286 * Compiling Different Versions of Ada::
287 * Character Set Control::
288 * File Naming Control::
289 * Subprogram Inlining Control::
290 * Auxiliary Output Control::
291 * Debugging Control::
292 * Exception Handling Control::
293 * Units to Sources Mapping Files::
294 * Integrated Preprocessing::
299 Binding Ada Programs With gnatbind
302 * Switches for gnatbind::
303 * Command-Line Access::
304 * Search Paths for gnatbind::
305 * Examples of gnatbind Usage::
307 Switches for gnatbind
309 * Consistency-Checking Modes::
310 * Binder Error Message Control::
311 * Elaboration Control::
313 * Binding with Non-Ada Main Programs::
314 * Binding Programs with No Main Subprogram::
316 Linking Using gnatlink
319 * Switches for gnatlink::
321 The GNAT Make Program gnatmake
324 * Switches for gnatmake::
325 * Mode Switches for gnatmake::
326 * Notes on the Command Line::
327 * How gnatmake Works::
328 * Examples of gnatmake Usage::
330 Improving Performance
331 * Performance Considerations::
332 * Text_IO Suggestions::
333 * Reducing Size of Ada Executables with gnatelim::
334 * Reducing Size of Executables with unused subprogram/data elimination::
336 Performance Considerations
337 * Controlling Run-Time Checks::
338 * Use of Restrictions::
339 * Optimization Levels::
340 * Debugging Optimized Code::
341 * Inlining of Subprograms::
342 * Other Optimization Switches::
343 * Optimization and Strict Aliasing::
345 * Coverage Analysis::
348 Reducing Size of Ada Executables with gnatelim
351 * Processing Precompiled Libraries::
352 * Correcting the List of Eliminate Pragmas::
353 * Making Your Executables Smaller::
354 * Summary of the gnatelim Usage Cycle::
356 Reducing Size of Executables with unused subprogram/data elimination
357 * About unused subprogram/data elimination::
358 * Compilation options::
360 Renaming Files Using gnatchop
362 * Handling Files with Multiple Units::
363 * Operating gnatchop in Compilation Mode::
364 * Command Line for gnatchop::
365 * Switches for gnatchop::
366 * Examples of gnatchop Usage::
368 Configuration Pragmas
370 * Handling of Configuration Pragmas::
371 * The Configuration Pragmas Files::
373 Handling Arbitrary File Naming Conventions Using gnatname
375 * Arbitrary File Naming Conventions::
377 * Switches for gnatname::
378 * Examples of gnatname Usage::
380 The Cross-Referencing Tools gnatxref and gnatfind
382 * Switches for gnatxref::
383 * Switches for gnatfind::
384 * Project Files for gnatxref and gnatfind::
385 * Regular Expressions in gnatfind and gnatxref::
386 * Examples of gnatxref Usage::
387 * Examples of gnatfind Usage::
389 The GNAT Pretty-Printer gnatpp
391 * Switches for gnatpp::
394 The GNAT Metrics Tool gnatmetric
396 * Switches for gnatmetric::
398 File Name Krunching Using gnatkr
403 * Examples of gnatkr Usage::
405 Preprocessing Using gnatprep
406 * Preprocessing Symbols::
408 * Switches for gnatprep::
409 * Form of Definitions File::
410 * Form of Input Text for gnatprep::
413 The GNAT Run-Time Library Builder gnatlbr
416 * Switches for gnatlbr::
417 * Examples of gnatlbr Usage::
420 The GNAT Library Browser gnatls
423 * Switches for gnatls::
424 * Examples of gnatls Usage::
426 Cleaning Up Using gnatclean
428 * Running gnatclean::
429 * Switches for gnatclean::
430 @c * Examples of gnatclean Usage::
436 * Introduction to Libraries in GNAT::
437 * General Ada Libraries::
438 * Stand-alone Ada Libraries::
439 * Rebuilding the GNAT Run-Time Library::
441 Using the GNU make Utility
443 * Using gnatmake in a Makefile::
444 * Automatically Creating a List of Directories::
445 * Generating the Command Line Switches::
446 * Overcoming Command Line Length Limits::
449 Memory Management Issues
451 * Some Useful Memory Pools::
452 * The GNAT Debug Pool Facility::
457 Stack Related Facilities
459 * Stack Overflow Checking::
460 * Static Stack Usage Analysis::
461 * Dynamic Stack Usage Analysis::
463 Some Useful Memory Pools
465 The GNAT Debug Pool Facility
471 * Switches for gnatmem::
472 * Example of gnatmem Usage::
475 Verifying Properties Using gnatcheck
477 * Format of the Report File::
478 * General gnatcheck Switches::
479 * gnatcheck Rule Options::
480 * Adding the Results of Compiler Checks to gnatcheck Output::
481 * Project-Wide Checks::
484 * Example of gnatcheck Usage::
486 Sample Bodies Using gnatstub
489 * Switches for gnatstub::
491 Other Utility Programs
493 * Using Other Utility Programs with GNAT::
494 * The External Symbol Naming Scheme of GNAT::
495 * Converting Ada Files to html with gnathtml::
498 Code Coverage and Profiling
500 * Code Coverage of Ada Programs using gcov::
501 * Profiling an Ada Program using gprof::
504 Running and Debugging Ada Programs
506 * The GNAT Debugger GDB::
508 * Introduction to GDB Commands::
509 * Using Ada Expressions::
510 * Calling User-Defined Subprograms::
511 * Using the Next Command in a Function::
514 * Debugging Generic Units::
515 * Remote Debugging using gdbserver::
516 * GNAT Abnormal Termination or Failure to Terminate::
517 * Naming Conventions for GNAT Source Files::
518 * Getting Internal Debugging Information::
526 Compatibility with HP Ada
528 * Ada Language Compatibility::
529 * Differences in the Definition of Package System::
530 * Language-Related Features::
531 * The Package STANDARD::
532 * The Package SYSTEM::
533 * Tasking and Task-Related Features::
534 * Pragmas and Pragma-Related Features::
535 * Library of Predefined Units::
537 * Main Program Definition::
538 * Implementation-Defined Attributes::
539 * Compiler and Run-Time Interfacing::
540 * Program Compilation and Library Management::
542 * Implementation Limits::
543 * Tools and Utilities::
545 Language-Related Features
547 * Integer Types and Representations::
548 * Floating-Point Types and Representations::
549 * Pragmas Float_Representation and Long_Float::
550 * Fixed-Point Types and Representations::
551 * Record and Array Component Alignment::
553 * Other Representation Clauses::
555 Tasking and Task-Related Features
557 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
558 * Assigning Task IDs::
559 * Task IDs and Delays::
560 * Task-Related Pragmas::
561 * Scheduling and Task Priority::
563 * External Interrupts::
565 Pragmas and Pragma-Related Features
567 * Restrictions on the Pragma INLINE::
568 * Restrictions on the Pragma INTERFACE::
569 * Restrictions on the Pragma SYSTEM_NAME::
571 Library of Predefined Units
573 * Changes to DECLIB::
577 * Shared Libraries and Options Files::
581 Platform-Specific Information for the Run-Time Libraries
583 * Summary of Run-Time Configurations::
584 * Specifying a Run-Time Library::
585 * Choosing the Scheduling Policy::
586 * Solaris-Specific Considerations::
587 * Linux-Specific Considerations::
588 * AIX-Specific Considerations::
589 * Irix-Specific Considerations::
590 * RTX-Specific Considerations::
591 * HP-UX-Specific Considerations::
593 Example of Binder Output File
595 Elaboration Order Handling in GNAT
598 * Checking the Elaboration Order::
599 * Controlling the Elaboration Order::
600 * Controlling Elaboration in GNAT - Internal Calls::
601 * Controlling Elaboration in GNAT - External Calls::
602 * Default Behavior in GNAT - Ensuring Safety::
603 * Treatment of Pragma Elaborate::
604 * Elaboration Issues for Library Tasks::
605 * Mixing Elaboration Models::
606 * What to Do If the Default Elaboration Behavior Fails::
607 * Elaboration for Access-to-Subprogram Values::
608 * Summary of Procedures for Elaboration Control::
609 * Other Elaboration Order Considerations::
611 Conditional Compilation
612 * Use of Boolean Constants::
613 * Debugging - A Special Case::
614 * Conditionalizing Declarations::
615 * Use of Alternative Implementations::
620 * Basic Assembler Syntax::
621 * A Simple Example of Inline Assembler::
622 * Output Variables in Inline Assembler::
623 * Input Variables in Inline Assembler::
624 * Inlining Inline Assembler Code::
625 * Other Asm Functionality::
627 Compatibility and Porting Guide
629 * Compatibility with Ada 83::
630 * Compatibility between Ada 95 and Ada 2005::
631 * Implementation-dependent characteristics::
633 @c This brief section is only in the non-VMS version
634 @c The complete chapter on HP Ada issues is in the VMS version
635 * Compatibility with HP Ada 83::
637 * Compatibility with Other Ada Systems::
638 * Representation Clauses::
640 * Transitioning to 64-Bit GNAT for OpenVMS::
644 Microsoft Windows Topics
646 * Using GNAT on Windows::
647 * CONSOLE and WINDOWS subsystems::
649 * Mixed-Language Programming on Windows::
650 * Windows Calling Conventions::
651 * Introduction to Dynamic Link Libraries (DLLs)::
652 * Using DLLs with GNAT::
653 * Building DLLs with GNAT::
654 * GNAT and Windows Resources::
656 * Setting Stack Size from gnatlink::
657 * Setting Heap Size from gnatlink::
664 @node About This Guide
665 @unnumbered About This Guide
669 This guide describes the use of @value{EDITION},
670 a compiler and software development toolset for the full Ada
671 programming language, implemented on OpenVMS for HP's Alpha and
672 Integrity server (I64) platforms.
675 This guide describes the use of @value{EDITION},
676 a compiler and software development
677 toolset for the full Ada programming language.
679 It documents the features of the compiler and tools, and explains
680 how to use them to build Ada applications.
682 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
683 Ada 83 compatibility mode.
684 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
685 but you can override with a compiler switch
686 (@pxref{Compiling Different Versions of Ada})
687 to explicitly specify the language version.
688 Throughout this manual, references to ``Ada'' without a year suffix
689 apply to both the Ada 95 and Ada 2005 versions of the language.
693 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
694 ``GNAT'' in the remainder of this document.
701 * What This Guide Contains::
702 * What You Should Know before Reading This Guide::
703 * Related Information::
707 @node What This Guide Contains
708 @unnumberedsec What This Guide Contains
711 This guide contains the following chapters:
715 @ref{Getting Started with GNAT}, describes how to get started compiling
716 and running Ada programs with the GNAT Ada programming environment.
718 @ref{The GNAT Compilation Model}, describes the compilation model used
722 @ref{Compiling Using gcc}, describes how to compile
723 Ada programs with @command{gcc}, the Ada compiler.
726 @ref{Binding Using gnatbind}, describes how to
727 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
731 @ref{Linking Using gnatlink},
732 describes @command{gnatlink}, a
733 program that provides for linking using the GNAT run-time library to
734 construct a program. @command{gnatlink} can also incorporate foreign language
735 object units into the executable.
738 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
739 utility that automatically determines the set of sources
740 needed by an Ada compilation unit, and executes the necessary compilations
744 @ref{Improving Performance}, shows various techniques for making your
745 Ada program run faster or take less space.
746 It discusses the effect of the compiler's optimization switch and
747 also describes the @command{gnatelim} tool and unused subprogram/data
751 @ref{Renaming Files Using gnatchop}, describes
752 @code{gnatchop}, a utility that allows you to preprocess a file that
753 contains Ada source code, and split it into one or more new files, one
754 for each compilation unit.
757 @ref{Configuration Pragmas}, describes the configuration pragmas
761 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
762 shows how to override the default GNAT file naming conventions,
763 either for an individual unit or globally.
766 @ref{GNAT Project Manager}, describes how to use project files
767 to organize large projects.
770 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
771 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
772 way to navigate through sources.
775 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
776 version of an Ada source file with control over casing, indentation,
777 comment placement, and other elements of program presentation style.
780 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
781 metrics for an Ada source file, such as the number of types and subprograms,
782 and assorted complexity measures.
785 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
786 file name krunching utility, used to handle shortened
787 file names on operating systems with a limit on the length of names.
790 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
791 preprocessor utility that allows a single source file to be used to
792 generate multiple or parameterized source files by means of macro
797 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
798 a tool for rebuilding the GNAT run time with user-supplied
799 configuration pragmas.
803 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
804 utility that displays information about compiled units, including dependences
805 on the corresponding sources files, and consistency of compilations.
808 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
809 to delete files that are produced by the compiler, binder and linker.
813 @ref{GNAT and Libraries}, describes the process of creating and using
814 Libraries with GNAT. It also describes how to recompile the GNAT run-time
818 @ref{Using the GNU make Utility}, describes some techniques for using
819 the GNAT toolset in Makefiles.
823 @ref{Memory Management Issues}, describes some useful predefined storage pools
824 and in particular the GNAT Debug Pool facility, which helps detect incorrect
827 It also describes @command{gnatmem}, a utility that monitors dynamic
828 allocation and deallocation and helps detect ``memory leaks''.
832 @ref{Stack Related Facilities}, describes some useful tools associated with
833 stack checking and analysis.
836 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
837 a utility that checks Ada code against a set of rules.
840 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
841 a utility that generates empty but compilable bodies for library units.
844 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
845 generate automatically Ada bindings from C and C++ headers.
848 @ref{Other Utility Programs}, discusses several other GNAT utilities,
849 including @code{gnathtml}.
853 @ref{Code Coverage and Profiling}, describes how to perform a structural
854 coverage and profile the execution of Ada programs.
858 @ref{Running and Debugging Ada Programs}, describes how to run and debug
863 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
864 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
865 developed by Digital Equipment Corporation and currently supported by HP.}
866 for OpenVMS Alpha. This product was formerly known as DEC Ada,
869 historical compatibility reasons, the relevant libraries still use the
874 @ref{Platform-Specific Information for the Run-Time Libraries},
875 describes the various run-time
876 libraries supported by GNAT on various platforms and explains how to
877 choose a particular library.
880 @ref{Example of Binder Output File}, shows the source code for the binder
881 output file for a sample program.
884 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
885 you deal with elaboration order issues.
888 @ref{Conditional Compilation}, describes how to model conditional compilation,
889 both with Ada in general and with GNAT facilities in particular.
892 @ref{Inline Assembler}, shows how to use the inline assembly facility
896 @ref{Compatibility and Porting Guide}, contains sections on compatibility
897 of GNAT with other Ada development environments (including Ada 83 systems),
898 to assist in porting code from those environments.
902 @ref{Microsoft Windows Topics}, presents information relevant to the
903 Microsoft Windows platform.
907 @c *************************************************
908 @node What You Should Know before Reading This Guide
909 @c *************************************************
910 @unnumberedsec What You Should Know before Reading This Guide
912 @cindex Ada 95 Language Reference Manual
913 @cindex Ada 2005 Language Reference Manual
915 This guide assumes a basic familiarity with the Ada 95 language, as
916 described in the International Standard ANSI/ISO/IEC-8652:1995, January
918 It does not require knowledge of the new features introduced by Ada 2005,
919 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
921 Both reference manuals are included in the GNAT documentation
924 @node Related Information
925 @unnumberedsec Related Information
928 For further information about related tools, refer to the following
933 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
934 Reference Manual}, which contains all reference material for the GNAT
935 implementation of Ada.
939 @cite{Using the GNAT Programming Studio}, which describes the GPS
940 Integrated Development Environment.
943 @cite{GNAT Programming Studio Tutorial}, which introduces the
944 main GPS features through examples.
948 @cite{Ada 95 Reference Manual}, which contains reference
949 material for the Ada 95 programming language.
952 @cite{Ada 2005 Reference Manual}, which contains reference
953 material for the Ada 2005 programming language.
956 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
958 in the GNU:[DOCS] directory,
960 for all details on the use of the GNU source-level debugger.
963 @xref{Top,, The extensible self-documenting text editor, emacs,
966 located in the GNU:[DOCS] directory if the EMACS kit is installed,
968 for full information on the extensible editor and programming
975 @unnumberedsec Conventions
977 @cindex Typographical conventions
980 Following are examples of the typographical and graphic conventions used
985 @code{Functions}, @command{utility program names}, @code{standard names},
989 @option{Option flags}
992 @file{File names}, @samp{button names}, and @samp{field names}.
995 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1002 @r{[}optional information or parameters@r{]}
1005 Examples are described by text
1007 and then shown this way.
1012 Commands that are entered by the user are preceded in this manual by the
1013 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1014 uses this sequence as a prompt, then the commands will appear exactly as
1015 you see them in the manual. If your system uses some other prompt, then
1016 the command will appear with the @code{$} replaced by whatever prompt
1017 character you are using.
1020 Full file names are shown with the ``@code{/}'' character
1021 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1022 If you are using GNAT on a Windows platform, please note that
1023 the ``@code{\}'' character should be used instead.
1026 @c ****************************
1027 @node Getting Started with GNAT
1028 @chapter Getting Started with GNAT
1031 This chapter describes some simple ways of using GNAT to build
1032 executable Ada programs.
1034 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1035 show how to use the command line environment.
1036 @ref{Introduction to GPS}, provides a brief
1037 introduction to the GNAT Programming Studio, a visually-oriented
1038 Integrated Development Environment for GNAT.
1039 GPS offers a graphical ``look and feel'', support for development in
1040 other programming languages, comprehensive browsing features, and
1041 many other capabilities.
1042 For information on GPS please refer to
1043 @cite{Using the GNAT Programming Studio}.
1048 * Running a Simple Ada Program::
1049 * Running a Program with Multiple Units::
1050 * Using the gnatmake Utility::
1052 * Editing with Emacs::
1055 * Introduction to GPS::
1060 @section Running GNAT
1063 Three steps are needed to create an executable file from an Ada source
1068 The source file(s) must be compiled.
1070 The file(s) must be bound using the GNAT binder.
1072 All appropriate object files must be linked to produce an executable.
1076 All three steps are most commonly handled by using the @command{gnatmake}
1077 utility program that, given the name of the main program, automatically
1078 performs the necessary compilation, binding and linking steps.
1080 @node Running a Simple Ada Program
1081 @section Running a Simple Ada Program
1084 Any text editor may be used to prepare an Ada program.
1086 used, the optional Ada mode may be helpful in laying out the program.)
1088 program text is a normal text file. We will assume in our initial
1089 example that you have used your editor to prepare the following
1090 standard format text file:
1092 @smallexample @c ada
1094 with Ada.Text_IO; use Ada.Text_IO;
1097 Put_Line ("Hello WORLD!");
1103 This file should be named @file{hello.adb}.
1104 With the normal default file naming conventions, GNAT requires
1106 contain a single compilation unit whose file name is the
1108 with periods replaced by hyphens; the
1109 extension is @file{ads} for a
1110 spec and @file{adb} for a body.
1111 You can override this default file naming convention by use of the
1112 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1113 Alternatively, if you want to rename your files according to this default
1114 convention, which is probably more convenient if you will be using GNAT
1115 for all your compilations, then the @code{gnatchop} utility
1116 can be used to generate correctly-named source files
1117 (@pxref{Renaming Files Using gnatchop}).
1119 You can compile the program using the following command (@code{$} is used
1120 as the command prompt in the examples in this document):
1127 @command{gcc} is the command used to run the compiler. This compiler is
1128 capable of compiling programs in several languages, including Ada and
1129 C. It assumes that you have given it an Ada program if the file extension is
1130 either @file{.ads} or @file{.adb}, and it will then call
1131 the GNAT compiler to compile the specified file.
1134 The @option{-c} switch is required. It tells @command{gcc} to only do a
1135 compilation. (For C programs, @command{gcc} can also do linking, but this
1136 capability is not used directly for Ada programs, so the @option{-c}
1137 switch must always be present.)
1140 This compile command generates a file
1141 @file{hello.o}, which is the object
1142 file corresponding to your Ada program. It also generates
1143 an ``Ada Library Information'' file @file{hello.ali},
1144 which contains additional information used to check
1145 that an Ada program is consistent.
1146 To build an executable file,
1147 use @code{gnatbind} to bind the program
1148 and @command{gnatlink} to link it. The
1149 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1150 @file{ALI} file, but the default extension of @file{.ali} can
1151 be omitted. This means that in the most common case, the argument
1152 is simply the name of the main program:
1160 A simpler method of carrying out these steps is to use
1162 a master program that invokes all the required
1163 compilation, binding and linking tools in the correct order. In particular,
1164 @command{gnatmake} automatically recompiles any sources that have been
1165 modified since they were last compiled, or sources that depend
1166 on such modified sources, so that ``version skew'' is avoided.
1167 @cindex Version skew (avoided by @command{gnatmake})
1170 $ gnatmake hello.adb
1174 The result is an executable program called @file{hello}, which can be
1182 assuming that the current directory is on the search path
1183 for executable programs.
1186 and, if all has gone well, you will see
1193 appear in response to this command.
1195 @c ****************************************
1196 @node Running a Program with Multiple Units
1197 @section Running a Program with Multiple Units
1200 Consider a slightly more complicated example that has three files: a
1201 main program, and the spec and body of a package:
1203 @smallexample @c ada
1206 package Greetings is
1211 with Ada.Text_IO; use Ada.Text_IO;
1212 package body Greetings is
1215 Put_Line ("Hello WORLD!");
1218 procedure Goodbye is
1220 Put_Line ("Goodbye WORLD!");
1237 Following the one-unit-per-file rule, place this program in the
1238 following three separate files:
1242 spec of package @code{Greetings}
1245 body of package @code{Greetings}
1248 body of main program
1252 To build an executable version of
1253 this program, we could use four separate steps to compile, bind, and link
1254 the program, as follows:
1258 $ gcc -c greetings.adb
1264 Note that there is no required order of compilation when using GNAT.
1265 In particular it is perfectly fine to compile the main program first.
1266 Also, it is not necessary to compile package specs in the case where
1267 there is an accompanying body; you only need to compile the body. If you want
1268 to submit these files to the compiler for semantic checking and not code
1269 generation, then use the
1270 @option{-gnatc} switch:
1273 $ gcc -c greetings.ads -gnatc
1277 Although the compilation can be done in separate steps as in the
1278 above example, in practice it is almost always more convenient
1279 to use the @command{gnatmake} tool. All you need to know in this case
1280 is the name of the main program's source file. The effect of the above four
1281 commands can be achieved with a single one:
1284 $ gnatmake gmain.adb
1288 In the next section we discuss the advantages of using @command{gnatmake} in
1291 @c *****************************
1292 @node Using the gnatmake Utility
1293 @section Using the @command{gnatmake} Utility
1296 If you work on a program by compiling single components at a time using
1297 @command{gcc}, you typically keep track of the units you modify. In order to
1298 build a consistent system, you compile not only these units, but also any
1299 units that depend on the units you have modified.
1300 For example, in the preceding case,
1301 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1302 you edit @file{greetings.ads}, you must recompile both
1303 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1304 units that depend on @file{greetings.ads}.
1306 @code{gnatbind} will warn you if you forget one of these compilation
1307 steps, so that it is impossible to generate an inconsistent program as a
1308 result of forgetting to do a compilation. Nevertheless it is tedious and
1309 error-prone to keep track of dependencies among units.
1310 One approach to handle the dependency-bookkeeping is to use a
1311 makefile. However, makefiles present maintenance problems of their own:
1312 if the dependencies change as you change the program, you must make
1313 sure that the makefile is kept up-to-date manually, which is also an
1314 error-prone process.
1316 The @command{gnatmake} utility takes care of these details automatically.
1317 Invoke it using either one of the following forms:
1320 $ gnatmake gmain.adb
1321 $ gnatmake ^gmain^GMAIN^
1325 The argument is the name of the file containing the main program;
1326 you may omit the extension. @command{gnatmake}
1327 examines the environment, automatically recompiles any files that need
1328 recompiling, and binds and links the resulting set of object files,
1329 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1330 In a large program, it
1331 can be extremely helpful to use @command{gnatmake}, because working out by hand
1332 what needs to be recompiled can be difficult.
1334 Note that @command{gnatmake}
1335 takes into account all the Ada rules that
1336 establish dependencies among units. These include dependencies that result
1337 from inlining subprogram bodies, and from
1338 generic instantiation. Unlike some other
1339 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1340 found by the compiler on a previous compilation, which may possibly
1341 be wrong when sources change. @command{gnatmake} determines the exact set of
1342 dependencies from scratch each time it is run.
1345 @node Editing with Emacs
1346 @section Editing with Emacs
1350 Emacs is an extensible self-documenting text editor that is available in a
1351 separate VMSINSTAL kit.
1353 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1354 click on the Emacs Help menu and run the Emacs Tutorial.
1355 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1356 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1358 Documentation on Emacs and other tools is available in Emacs under the
1359 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1360 use the middle mouse button to select a topic (e.g.@: Emacs).
1362 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1363 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1364 get to the Emacs manual.
1365 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1368 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1369 which is sufficiently extensible to provide for a complete programming
1370 environment and shell for the sophisticated user.
1374 @node Introduction to GPS
1375 @section Introduction to GPS
1376 @cindex GPS (GNAT Programming Studio)
1377 @cindex GNAT Programming Studio (GPS)
1379 Although the command line interface (@command{gnatmake}, etc.) alone
1380 is sufficient, a graphical Interactive Development
1381 Environment can make it easier for you to compose, navigate, and debug
1382 programs. This section describes the main features of GPS
1383 (``GNAT Programming Studio''), the GNAT graphical IDE.
1384 You will see how to use GPS to build and debug an executable, and
1385 you will also learn some of the basics of the GNAT ``project'' facility.
1387 GPS enables you to do much more than is presented here;
1388 e.g., you can produce a call graph, interface to a third-party
1389 Version Control System, and inspect the generated assembly language
1391 Indeed, GPS also supports languages other than Ada.
1392 Such additional information, and an explanation of all of the GPS menu
1393 items. may be found in the on-line help, which includes
1394 a user's guide and a tutorial (these are also accessible from the GNAT
1398 * Building a New Program with GPS::
1399 * Simple Debugging with GPS::
1402 @node Building a New Program with GPS
1403 @subsection Building a New Program with GPS
1405 GPS invokes the GNAT compilation tools using information
1406 contained in a @emph{project} (also known as a @emph{project file}):
1407 a collection of properties such
1408 as source directories, identities of main subprograms, tool switches, etc.,
1409 and their associated values.
1410 See @ref{GNAT Project Manager} for details.
1411 In order to run GPS, you will need to either create a new project
1412 or else open an existing one.
1414 This section will explain how you can use GPS to create a project,
1415 to associate Ada source files with a project, and to build and run
1419 @item @emph{Creating a project}
1421 Invoke GPS, either from the command line or the platform's IDE.
1422 After it starts, GPS will display a ``Welcome'' screen with three
1427 @code{Start with default project in directory}
1430 @code{Create new project with wizard}
1433 @code{Open existing project}
1437 Select @code{Create new project with wizard} and press @code{OK}.
1438 A new window will appear. In the text box labeled with
1439 @code{Enter the name of the project to create}, type @file{sample}
1440 as the project name.
1441 In the next box, browse to choose the directory in which you
1442 would like to create the project file.
1443 After selecting an appropriate directory, press @code{Forward}.
1445 A window will appear with the title
1446 @code{Version Control System Configuration}.
1447 Simply press @code{Forward}.
1449 A window will appear with the title
1450 @code{Please select the source directories for this project}.
1451 The directory that you specified for the project file will be selected
1452 by default as the one to use for sources; simply press @code{Forward}.
1454 A window will appear with the title
1455 @code{Please select the build directory for this project}.
1456 The directory that you specified for the project file will be selected
1457 by default for object files and executables;
1458 simply press @code{Forward}.
1460 A window will appear with the title
1461 @code{Please select the main units for this project}.
1462 You will supply this information later, after creating the source file.
1463 Simply press @code{Forward} for now.
1465 A window will appear with the title
1466 @code{Please select the switches to build the project}.
1467 Press @code{Apply}. This will create a project file named
1468 @file{sample.prj} in the directory that you had specified.
1470 @item @emph{Creating and saving the source file}
1472 After you create the new project, a GPS window will appear, which is
1473 partitioned into two main sections:
1477 A @emph{Workspace area}, initially greyed out, which you will use for
1478 creating and editing source files
1481 Directly below, a @emph{Messages area}, which initially displays a
1482 ``Welcome'' message.
1483 (If the Messages area is not visible, drag its border upward to expand it.)
1487 Select @code{File} on the menu bar, and then the @code{New} command.
1488 The Workspace area will become white, and you can now
1489 enter the source program explicitly.
1490 Type the following text
1492 @smallexample @c ada
1494 with Ada.Text_IO; use Ada.Text_IO;
1497 Put_Line("Hello from GPS!");
1503 Select @code{File}, then @code{Save As}, and enter the source file name
1505 The file will be saved in the same directory you specified as the
1506 location of the default project file.
1508 @item @emph{Updating the project file}
1510 You need to add the new source file to the project.
1512 the @code{Project} menu and then @code{Edit project properties}.
1513 Click the @code{Main files} tab on the left, and then the
1515 Choose @file{hello.adb} from the list, and press @code{Open}.
1516 The project settings window will reflect this action.
1519 @item @emph{Building and running the program}
1521 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1522 and select @file{hello.adb}.
1523 The Messages window will display the resulting invocations of @command{gcc},
1524 @command{gnatbind}, and @command{gnatlink}
1525 (reflecting the default switch settings from the
1526 project file that you created) and then a ``successful compilation/build''
1529 To run the program, choose the @code{Build} menu, then @code{Run}, and
1530 select @command{hello}.
1531 An @emph{Arguments Selection} window will appear.
1532 There are no command line arguments, so just click @code{OK}.
1534 The Messages window will now display the program's output (the string
1535 @code{Hello from GPS}), and at the bottom of the GPS window a status
1536 update is displayed (@code{Run: hello}).
1537 Close the GPS window (or select @code{File}, then @code{Exit}) to
1538 terminate this GPS session.
1541 @node Simple Debugging with GPS
1542 @subsection Simple Debugging with GPS
1544 This section illustrates basic debugging techniques (setting breakpoints,
1545 examining/modifying variables, single stepping).
1548 @item @emph{Opening a project}
1550 Start GPS and select @code{Open existing project}; browse to
1551 specify the project file @file{sample.prj} that you had created in the
1554 @item @emph{Creating a source file}
1556 Select @code{File}, then @code{New}, and type in the following program:
1558 @smallexample @c ada
1560 with Ada.Text_IO; use Ada.Text_IO;
1561 procedure Example is
1562 Line : String (1..80);
1565 Put_Line("Type a line of text at each prompt; an empty line to exit");
1569 Put_Line (Line (1..N) );
1577 Select @code{File}, then @code{Save as}, and enter the file name
1580 @item @emph{Updating the project file}
1582 Add @code{Example} as a new main unit for the project:
1585 Select @code{Project}, then @code{Edit Project Properties}.
1588 Select the @code{Main files} tab, click @code{Add}, then
1589 select the file @file{example.adb} from the list, and
1591 You will see the file name appear in the list of main units
1597 @item @emph{Building/running the executable}
1599 To build the executable
1600 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1602 Run the program to see its effect (in the Messages area).
1603 Each line that you enter is displayed; an empty line will
1604 cause the loop to exit and the program to terminate.
1606 @item @emph{Debugging the program}
1608 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1609 which are required for debugging, are on by default when you create
1611 Thus unless you intentionally remove these settings, you will be able
1612 to debug any program that you develop using GPS.
1615 @item @emph{Initializing}
1617 Select @code{Debug}, then @code{Initialize}, then @file{example}
1619 @item @emph{Setting a breakpoint}
1621 After performing the initialization step, you will observe a small
1622 icon to the right of each line number.
1623 This serves as a toggle for breakpoints; clicking the icon will
1624 set a breakpoint at the corresponding line (the icon will change to
1625 a red circle with an ``x''), and clicking it again
1626 will remove the breakpoint / reset the icon.
1628 For purposes of this example, set a breakpoint at line 10 (the
1629 statement @code{Put_Line@ (Line@ (1..N));}
1631 @item @emph{Starting program execution}
1633 Select @code{Debug}, then @code{Run}. When the
1634 @code{Program Arguments} window appears, click @code{OK}.
1635 A console window will appear; enter some line of text,
1636 e.g.@: @code{abcde}, at the prompt.
1637 The program will pause execution when it gets to the
1638 breakpoint, and the corresponding line is highlighted.
1640 @item @emph{Examining a variable}
1642 Move the mouse over one of the occurrences of the variable @code{N}.
1643 You will see the value (5) displayed, in ``tool tip'' fashion.
1644 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1645 You will see information about @code{N} appear in the @code{Debugger Data}
1646 pane, showing the value as 5.
1648 @item @emph{Assigning a new value to a variable}
1650 Right click on the @code{N} in the @code{Debugger Data} pane, and
1651 select @code{Set value of N}.
1652 When the input window appears, enter the value @code{4} and click
1654 This value does not automatically appear in the @code{Debugger Data}
1655 pane; to see it, right click again on the @code{N} in the
1656 @code{Debugger Data} pane and select @code{Update value}.
1657 The new value, 4, will appear in red.
1659 @item @emph{Single stepping}
1661 Select @code{Debug}, then @code{Next}.
1662 This will cause the next statement to be executed, in this case the
1663 call of @code{Put_Line} with the string slice.
1664 Notice in the console window that the displayed string is simply
1665 @code{abcd} and not @code{abcde} which you had entered.
1666 This is because the upper bound of the slice is now 4 rather than 5.
1668 @item @emph{Removing a breakpoint}
1670 Toggle the breakpoint icon at line 10.
1672 @item @emph{Resuming execution from a breakpoint}
1674 Select @code{Debug}, then @code{Continue}.
1675 The program will reach the next iteration of the loop, and
1676 wait for input after displaying the prompt.
1677 This time, just hit the @kbd{Enter} key.
1678 The value of @code{N} will be 0, and the program will terminate.
1679 The console window will disappear.
1684 @node The GNAT Compilation Model
1685 @chapter The GNAT Compilation Model
1686 @cindex GNAT compilation model
1687 @cindex Compilation model
1690 * Source Representation::
1691 * Foreign Language Representation::
1692 * File Naming Rules::
1693 * Using Other File Names::
1694 * Alternative File Naming Schemes::
1695 * Generating Object Files::
1696 * Source Dependencies::
1697 * The Ada Library Information Files::
1698 * Binding an Ada Program::
1699 * Mixed Language Programming::
1701 * Building Mixed Ada & C++ Programs::
1702 * Comparison between GNAT and C/C++ Compilation Models::
1704 * Comparison between GNAT and Conventional Ada Library Models::
1706 * Placement of temporary files::
1711 This chapter describes the compilation model used by GNAT. Although
1712 similar to that used by other languages, such as C and C++, this model
1713 is substantially different from the traditional Ada compilation models,
1714 which are based on a library. The model is initially described without
1715 reference to the library-based model. If you have not previously used an
1716 Ada compiler, you need only read the first part of this chapter. The
1717 last section describes and discusses the differences between the GNAT
1718 model and the traditional Ada compiler models. If you have used other
1719 Ada compilers, this section will help you to understand those
1720 differences, and the advantages of the GNAT model.
1722 @node Source Representation
1723 @section Source Representation
1727 Ada source programs are represented in standard text files, using
1728 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1729 7-bit ASCII set, plus additional characters used for
1730 representing foreign languages (@pxref{Foreign Language Representation}
1731 for support of non-USA character sets). The format effector characters
1732 are represented using their standard ASCII encodings, as follows:
1737 Vertical tab, @code{16#0B#}
1741 Horizontal tab, @code{16#09#}
1745 Carriage return, @code{16#0D#}
1749 Line feed, @code{16#0A#}
1753 Form feed, @code{16#0C#}
1757 Source files are in standard text file format. In addition, GNAT will
1758 recognize a wide variety of stream formats, in which the end of
1759 physical lines is marked by any of the following sequences:
1760 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1761 in accommodating files that are imported from other operating systems.
1763 @cindex End of source file
1764 @cindex Source file, end
1766 The end of a source file is normally represented by the physical end of
1767 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1768 recognized as signalling the end of the source file. Again, this is
1769 provided for compatibility with other operating systems where this
1770 code is used to represent the end of file.
1772 Each file contains a single Ada compilation unit, including any pragmas
1773 associated with the unit. For example, this means you must place a
1774 package declaration (a package @dfn{spec}) and the corresponding body in
1775 separate files. An Ada @dfn{compilation} (which is a sequence of
1776 compilation units) is represented using a sequence of files. Similarly,
1777 you will place each subunit or child unit in a separate file.
1779 @node Foreign Language Representation
1780 @section Foreign Language Representation
1783 GNAT supports the standard character sets defined in Ada as well as
1784 several other non-standard character sets for use in localized versions
1785 of the compiler (@pxref{Character Set Control}).
1788 * Other 8-Bit Codes::
1789 * Wide Character Encodings::
1797 The basic character set is Latin-1. This character set is defined by ISO
1798 standard 8859, part 1. The lower half (character codes @code{16#00#}
1799 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1800 is used to represent additional characters. These include extended letters
1801 used by European languages, such as French accents, the vowels with umlauts
1802 used in German, and the extra letter A-ring used in Swedish.
1804 @findex Ada.Characters.Latin_1
1805 For a complete list of Latin-1 codes and their encodings, see the source
1806 file of library unit @code{Ada.Characters.Latin_1} in file
1807 @file{a-chlat1.ads}.
1808 You may use any of these extended characters freely in character or
1809 string literals. In addition, the extended characters that represent
1810 letters can be used in identifiers.
1812 @node Other 8-Bit Codes
1813 @subsection Other 8-Bit Codes
1816 GNAT also supports several other 8-bit coding schemes:
1819 @item ISO 8859-2 (Latin-2)
1822 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1825 @item ISO 8859-3 (Latin-3)
1828 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1831 @item ISO 8859-4 (Latin-4)
1834 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1837 @item ISO 8859-5 (Cyrillic)
1840 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1841 lowercase equivalence.
1843 @item ISO 8859-15 (Latin-9)
1846 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1847 lowercase equivalence
1849 @item IBM PC (code page 437)
1850 @cindex code page 437
1851 This code page is the normal default for PCs in the U.S. It corresponds
1852 to the original IBM PC character set. This set has some, but not all, of
1853 the extended Latin-1 letters, but these letters do not have the same
1854 encoding as Latin-1. In this mode, these letters are allowed in
1855 identifiers with uppercase and lowercase equivalence.
1857 @item IBM PC (code page 850)
1858 @cindex code page 850
1859 This code page is a modification of 437 extended to include all the
1860 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1861 mode, all these letters are allowed in identifiers with uppercase and
1862 lowercase equivalence.
1864 @item Full Upper 8-bit
1865 Any character in the range 80-FF allowed in identifiers, and all are
1866 considered distinct. In other words, there are no uppercase and lowercase
1867 equivalences in this range. This is useful in conjunction with
1868 certain encoding schemes used for some foreign character sets (e.g.,
1869 the typical method of representing Chinese characters on the PC).
1872 No upper-half characters in the range 80-FF are allowed in identifiers.
1873 This gives Ada 83 compatibility for identifier names.
1877 For precise data on the encodings permitted, and the uppercase and lowercase
1878 equivalences that are recognized, see the file @file{csets.adb} in
1879 the GNAT compiler sources. You will need to obtain a full source release
1880 of GNAT to obtain this file.
1882 @node Wide Character Encodings
1883 @subsection Wide Character Encodings
1886 GNAT allows wide character codes to appear in character and string
1887 literals, and also optionally in identifiers, by means of the following
1888 possible encoding schemes:
1893 In this encoding, a wide character is represented by the following five
1901 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1902 characters (using uppercase letters) of the wide character code. For
1903 example, ESC A345 is used to represent the wide character with code
1905 This scheme is compatible with use of the full Wide_Character set.
1907 @item Upper-Half Coding
1908 @cindex Upper-Half Coding
1909 The wide character with encoding @code{16#abcd#} where the upper bit is on
1910 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1911 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1912 character, but is not required to be in the upper half. This method can
1913 be also used for shift-JIS or EUC, where the internal coding matches the
1916 @item Shift JIS Coding
1917 @cindex Shift JIS Coding
1918 A wide character is represented by a two-character sequence,
1920 @code{16#cd#}, with the restrictions described for upper-half encoding as
1921 described above. The internal character code is the corresponding JIS
1922 character according to the standard algorithm for Shift-JIS
1923 conversion. Only characters defined in the JIS code set table can be
1924 used with this encoding method.
1928 A wide character is represented by a two-character sequence
1930 @code{16#cd#}, with both characters being in the upper half. The internal
1931 character code is the corresponding JIS character according to the EUC
1932 encoding algorithm. Only characters defined in the JIS code set table
1933 can be used with this encoding method.
1936 A wide character is represented using
1937 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1938 10646-1/Am.2. Depending on the character value, the representation
1939 is a one, two, or three byte sequence:
1944 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1945 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1946 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1951 where the @var{xxx} bits correspond to the left-padded bits of the
1952 16-bit character value. Note that all lower half ASCII characters
1953 are represented as ASCII bytes and all upper half characters and
1954 other wide characters are represented as sequences of upper-half
1955 (The full UTF-8 scheme allows for encoding 31-bit characters as
1956 6-byte sequences, but in this implementation, all UTF-8 sequences
1957 of four or more bytes length will be treated as illegal).
1958 @item Brackets Coding
1959 In this encoding, a wide character is represented by the following eight
1967 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1968 characters (using uppercase letters) of the wide character code. For
1969 example, [``A345''] is used to represent the wide character with code
1970 @code{16#A345#}. It is also possible (though not required) to use the
1971 Brackets coding for upper half characters. For example, the code
1972 @code{16#A3#} can be represented as @code{[``A3'']}.
1974 This scheme is compatible with use of the full Wide_Character set,
1975 and is also the method used for wide character encoding in the standard
1976 ACVC (Ada Compiler Validation Capability) test suite distributions.
1981 Note: Some of these coding schemes do not permit the full use of the
1982 Ada character set. For example, neither Shift JIS, nor EUC allow the
1983 use of the upper half of the Latin-1 set.
1985 @node File Naming Rules
1986 @section File Naming Rules
1989 The default file name is determined by the name of the unit that the
1990 file contains. The name is formed by taking the full expanded name of
1991 the unit and replacing the separating dots with hyphens and using
1992 ^lowercase^uppercase^ for all letters.
1994 An exception arises if the file name generated by the above rules starts
1995 with one of the characters
1997 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2000 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2002 and the second character is a
2003 minus. In this case, the character ^tilde^dollar sign^ is used in place
2004 of the minus. The reason for this special rule is to avoid clashes with
2005 the standard names for child units of the packages System, Ada,
2006 Interfaces, and GNAT, which use the prefixes
2008 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2011 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2015 The file extension is @file{.ads} for a spec and
2016 @file{.adb} for a body. The following list shows some
2017 examples of these rules.
2024 @item arith_functions.ads
2025 Arith_Functions (package spec)
2026 @item arith_functions.adb
2027 Arith_Functions (package body)
2029 Func.Spec (child package spec)
2031 Func.Spec (child package body)
2033 Sub (subunit of Main)
2034 @item ^a~bad.adb^A$BAD.ADB^
2035 A.Bad (child package body)
2039 Following these rules can result in excessively long
2040 file names if corresponding
2041 unit names are long (for example, if child units or subunits are
2042 heavily nested). An option is available to shorten such long file names
2043 (called file name ``krunching''). This may be particularly useful when
2044 programs being developed with GNAT are to be used on operating systems
2045 with limited file name lengths. @xref{Using gnatkr}.
2047 Of course, no file shortening algorithm can guarantee uniqueness over
2048 all possible unit names; if file name krunching is used, it is your
2049 responsibility to ensure no name clashes occur. Alternatively you
2050 can specify the exact file names that you want used, as described
2051 in the next section. Finally, if your Ada programs are migrating from a
2052 compiler with a different naming convention, you can use the gnatchop
2053 utility to produce source files that follow the GNAT naming conventions.
2054 (For details @pxref{Renaming Files Using gnatchop}.)
2056 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2057 systems, case is not significant. So for example on @code{Windows XP}
2058 if the canonical name is @code{main-sub.adb}, you can use the file name
2059 @code{Main-Sub.adb} instead. However, case is significant for other
2060 operating systems, so for example, if you want to use other than
2061 canonically cased file names on a Unix system, you need to follow
2062 the procedures described in the next section.
2064 @node Using Other File Names
2065 @section Using Other File Names
2069 In the previous section, we have described the default rules used by
2070 GNAT to determine the file name in which a given unit resides. It is
2071 often convenient to follow these default rules, and if you follow them,
2072 the compiler knows without being explicitly told where to find all
2075 However, in some cases, particularly when a program is imported from
2076 another Ada compiler environment, it may be more convenient for the
2077 programmer to specify which file names contain which units. GNAT allows
2078 arbitrary file names to be used by means of the Source_File_Name pragma.
2079 The form of this pragma is as shown in the following examples:
2080 @cindex Source_File_Name pragma
2082 @smallexample @c ada
2084 pragma Source_File_Name (My_Utilities.Stacks,
2085 Spec_File_Name => "myutilst_a.ada");
2086 pragma Source_File_name (My_Utilities.Stacks,
2087 Body_File_Name => "myutilst.ada");
2092 As shown in this example, the first argument for the pragma is the unit
2093 name (in this example a child unit). The second argument has the form
2094 of a named association. The identifier
2095 indicates whether the file name is for a spec or a body;
2096 the file name itself is given by a string literal.
2098 The source file name pragma is a configuration pragma, which means that
2099 normally it will be placed in the @file{gnat.adc}
2100 file used to hold configuration
2101 pragmas that apply to a complete compilation environment.
2102 For more details on how the @file{gnat.adc} file is created and used
2103 see @ref{Handling of Configuration Pragmas}.
2104 @cindex @file{gnat.adc}
2107 GNAT allows completely arbitrary file names to be specified using the
2108 source file name pragma. However, if the file name specified has an
2109 extension other than @file{.ads} or @file{.adb} it is necessary to use
2110 a special syntax when compiling the file. The name in this case must be
2111 preceded by the special sequence @option{-x} followed by a space and the name
2112 of the language, here @code{ada}, as in:
2115 $ gcc -c -x ada peculiar_file_name.sim
2120 @command{gnatmake} handles non-standard file names in the usual manner (the
2121 non-standard file name for the main program is simply used as the
2122 argument to gnatmake). Note that if the extension is also non-standard,
2123 then it must be included in the @command{gnatmake} command, it may not
2126 @node Alternative File Naming Schemes
2127 @section Alternative File Naming Schemes
2128 @cindex File naming schemes, alternative
2131 In the previous section, we described the use of the @code{Source_File_Name}
2132 pragma to allow arbitrary names to be assigned to individual source files.
2133 However, this approach requires one pragma for each file, and especially in
2134 large systems can result in very long @file{gnat.adc} files, and also create
2135 a maintenance problem.
2137 GNAT also provides a facility for specifying systematic file naming schemes
2138 other than the standard default naming scheme previously described. An
2139 alternative scheme for naming is specified by the use of
2140 @code{Source_File_Name} pragmas having the following format:
2141 @cindex Source_File_Name pragma
2143 @smallexample @c ada
2144 pragma Source_File_Name (
2145 Spec_File_Name => FILE_NAME_PATTERN
2146 @r{[},Casing => CASING_SPEC@r{]}
2147 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2149 pragma Source_File_Name (
2150 Body_File_Name => FILE_NAME_PATTERN
2151 @r{[},Casing => CASING_SPEC@r{]}
2152 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2154 pragma Source_File_Name (
2155 Subunit_File_Name => FILE_NAME_PATTERN
2156 @r{[},Casing => CASING_SPEC@r{]}
2157 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2159 FILE_NAME_PATTERN ::= STRING_LITERAL
2160 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2164 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2165 It contains a single asterisk character, and the unit name is substituted
2166 systematically for this asterisk. The optional parameter
2167 @code{Casing} indicates
2168 whether the unit name is to be all upper-case letters, all lower-case letters,
2169 or mixed-case. If no
2170 @code{Casing} parameter is used, then the default is all
2171 ^lower-case^upper-case^.
2173 The optional @code{Dot_Replacement} string is used to replace any periods
2174 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2175 argument is used then separating dots appear unchanged in the resulting
2177 Although the above syntax indicates that the
2178 @code{Casing} argument must appear
2179 before the @code{Dot_Replacement} argument, but it
2180 is also permissible to write these arguments in the opposite order.
2182 As indicated, it is possible to specify different naming schemes for
2183 bodies, specs, and subunits. Quite often the rule for subunits is the
2184 same as the rule for bodies, in which case, there is no need to give
2185 a separate @code{Subunit_File_Name} rule, and in this case the
2186 @code{Body_File_name} rule is used for subunits as well.
2188 The separate rule for subunits can also be used to implement the rather
2189 unusual case of a compilation environment (e.g.@: a single directory) which
2190 contains a subunit and a child unit with the same unit name. Although
2191 both units cannot appear in the same partition, the Ada Reference Manual
2192 allows (but does not require) the possibility of the two units coexisting
2193 in the same environment.
2195 The file name translation works in the following steps:
2200 If there is a specific @code{Source_File_Name} pragma for the given unit,
2201 then this is always used, and any general pattern rules are ignored.
2204 If there is a pattern type @code{Source_File_Name} pragma that applies to
2205 the unit, then the resulting file name will be used if the file exists. If
2206 more than one pattern matches, the latest one will be tried first, and the
2207 first attempt resulting in a reference to a file that exists will be used.
2210 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2211 for which the corresponding file exists, then the standard GNAT default
2212 naming rules are used.
2217 As an example of the use of this mechanism, consider a commonly used scheme
2218 in which file names are all lower case, with separating periods copied
2219 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2220 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2223 @smallexample @c ada
2224 pragma Source_File_Name
2225 (Spec_File_Name => "*.1.ada");
2226 pragma Source_File_Name
2227 (Body_File_Name => "*.2.ada");
2231 The default GNAT scheme is actually implemented by providing the following
2232 default pragmas internally:
2234 @smallexample @c ada
2235 pragma Source_File_Name
2236 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2237 pragma Source_File_Name
2238 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2242 Our final example implements a scheme typically used with one of the
2243 Ada 83 compilers, where the separator character for subunits was ``__''
2244 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2245 by adding @file{.ADA}, and subunits by
2246 adding @file{.SEP}. All file names were
2247 upper case. Child units were not present of course since this was an
2248 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2249 the same double underscore separator for child units.
2251 @smallexample @c ada
2252 pragma Source_File_Name
2253 (Spec_File_Name => "*_.ADA",
2254 Dot_Replacement => "__",
2255 Casing = Uppercase);
2256 pragma Source_File_Name
2257 (Body_File_Name => "*.ADA",
2258 Dot_Replacement => "__",
2259 Casing = Uppercase);
2260 pragma Source_File_Name
2261 (Subunit_File_Name => "*.SEP",
2262 Dot_Replacement => "__",
2263 Casing = Uppercase);
2266 @node Generating Object Files
2267 @section Generating Object Files
2270 An Ada program consists of a set of source files, and the first step in
2271 compiling the program is to generate the corresponding object files.
2272 These are generated by compiling a subset of these source files.
2273 The files you need to compile are the following:
2277 If a package spec has no body, compile the package spec to produce the
2278 object file for the package.
2281 If a package has both a spec and a body, compile the body to produce the
2282 object file for the package. The source file for the package spec need
2283 not be compiled in this case because there is only one object file, which
2284 contains the code for both the spec and body of the package.
2287 For a subprogram, compile the subprogram body to produce the object file
2288 for the subprogram. The spec, if one is present, is as usual in a
2289 separate file, and need not be compiled.
2293 In the case of subunits, only compile the parent unit. A single object
2294 file is generated for the entire subunit tree, which includes all the
2298 Compile child units independently of their parent units
2299 (though, of course, the spec of all the ancestor unit must be present in order
2300 to compile a child unit).
2304 Compile generic units in the same manner as any other units. The object
2305 files in this case are small dummy files that contain at most the
2306 flag used for elaboration checking. This is because GNAT always handles generic
2307 instantiation by means of macro expansion. However, it is still necessary to
2308 compile generic units, for dependency checking and elaboration purposes.
2312 The preceding rules describe the set of files that must be compiled to
2313 generate the object files for a program. Each object file has the same
2314 name as the corresponding source file, except that the extension is
2317 You may wish to compile other files for the purpose of checking their
2318 syntactic and semantic correctness. For example, in the case where a
2319 package has a separate spec and body, you would not normally compile the
2320 spec. However, it is convenient in practice to compile the spec to make
2321 sure it is error-free before compiling clients of this spec, because such
2322 compilations will fail if there is an error in the spec.
2324 GNAT provides an option for compiling such files purely for the
2325 purposes of checking correctness; such compilations are not required as
2326 part of the process of building a program. To compile a file in this
2327 checking mode, use the @option{-gnatc} switch.
2329 @node Source Dependencies
2330 @section Source Dependencies
2333 A given object file clearly depends on the source file which is compiled
2334 to produce it. Here we are using @dfn{depends} in the sense of a typical
2335 @code{make} utility; in other words, an object file depends on a source
2336 file if changes to the source file require the object file to be
2338 In addition to this basic dependency, a given object may depend on
2339 additional source files as follows:
2343 If a file being compiled @code{with}'s a unit @var{X}, the object file
2344 depends on the file containing the spec of unit @var{X}. This includes
2345 files that are @code{with}'ed implicitly either because they are parents
2346 of @code{with}'ed child units or they are run-time units required by the
2347 language constructs used in a particular unit.
2350 If a file being compiled instantiates a library level generic unit, the
2351 object file depends on both the spec and body files for this generic
2355 If a file being compiled instantiates a generic unit defined within a
2356 package, the object file depends on the body file for the package as
2357 well as the spec file.
2361 @cindex @option{-gnatn} switch
2362 If a file being compiled contains a call to a subprogram for which
2363 pragma @code{Inline} applies and inlining is activated with the
2364 @option{-gnatn} switch, the object file depends on the file containing the
2365 body of this subprogram as well as on the file containing the spec. Note
2366 that for inlining to actually occur as a result of the use of this switch,
2367 it is necessary to compile in optimizing mode.
2369 @cindex @option{-gnatN} switch
2370 The use of @option{-gnatN} activates inlining optimization
2371 that is performed by the front end of the compiler. This inlining does
2372 not require that the code generation be optimized. Like @option{-gnatn},
2373 the use of this switch generates additional dependencies.
2375 When using a gcc-based back end (in practice this means using any version
2376 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2377 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2378 Historically front end inlining was more extensive than the gcc back end
2379 inlining, but that is no longer the case.
2382 If an object file @file{O} depends on the proper body of a subunit through
2383 inlining or instantiation, it depends on the parent unit of the subunit.
2384 This means that any modification of the parent unit or one of its subunits
2385 affects the compilation of @file{O}.
2388 The object file for a parent unit depends on all its subunit body files.
2391 The previous two rules meant that for purposes of computing dependencies and
2392 recompilation, a body and all its subunits are treated as an indivisible whole.
2395 These rules are applied transitively: if unit @code{A} @code{with}'s
2396 unit @code{B}, whose elaboration calls an inlined procedure in package
2397 @code{C}, the object file for unit @code{A} will depend on the body of
2398 @code{C}, in file @file{c.adb}.
2400 The set of dependent files described by these rules includes all the
2401 files on which the unit is semantically dependent, as dictated by the
2402 Ada language standard. However, it is a superset of what the
2403 standard describes, because it includes generic, inline, and subunit
2406 An object file must be recreated by recompiling the corresponding source
2407 file if any of the source files on which it depends are modified. For
2408 example, if the @code{make} utility is used to control compilation,
2409 the rule for an Ada object file must mention all the source files on
2410 which the object file depends, according to the above definition.
2411 The determination of the necessary
2412 recompilations is done automatically when one uses @command{gnatmake}.
2415 @node The Ada Library Information Files
2416 @section The Ada Library Information Files
2417 @cindex Ada Library Information files
2418 @cindex @file{ALI} files
2421 Each compilation actually generates two output files. The first of these
2422 is the normal object file that has a @file{.o} extension. The second is a
2423 text file containing full dependency information. It has the same
2424 name as the source file, but an @file{.ali} extension.
2425 This file is known as the Ada Library Information (@file{ALI}) file.
2426 The following information is contained in the @file{ALI} file.
2430 Version information (indicates which version of GNAT was used to compile
2431 the unit(s) in question)
2434 Main program information (including priority and time slice settings,
2435 as well as the wide character encoding used during compilation).
2438 List of arguments used in the @command{gcc} command for the compilation
2441 Attributes of the unit, including configuration pragmas used, an indication
2442 of whether the compilation was successful, exception model used etc.
2445 A list of relevant restrictions applying to the unit (used for consistency)
2449 Categorization information (e.g.@: use of pragma @code{Pure}).
2452 Information on all @code{with}'ed units, including presence of
2453 @code{Elaborate} or @code{Elaborate_All} pragmas.
2456 Information from any @code{Linker_Options} pragmas used in the unit
2459 Information on the use of @code{Body_Version} or @code{Version}
2460 attributes in the unit.
2463 Dependency information. This is a list of files, together with
2464 time stamp and checksum information. These are files on which
2465 the unit depends in the sense that recompilation is required
2466 if any of these units are modified.
2469 Cross-reference data. Contains information on all entities referenced
2470 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2471 provide cross-reference information.
2476 For a full detailed description of the format of the @file{ALI} file,
2477 see the source of the body of unit @code{Lib.Writ}, contained in file
2478 @file{lib-writ.adb} in the GNAT compiler sources.
2480 @node Binding an Ada Program
2481 @section Binding an Ada Program
2484 When using languages such as C and C++, once the source files have been
2485 compiled the only remaining step in building an executable program
2486 is linking the object modules together. This means that it is possible to
2487 link an inconsistent version of a program, in which two units have
2488 included different versions of the same header.
2490 The rules of Ada do not permit such an inconsistent program to be built.
2491 For example, if two clients have different versions of the same package,
2492 it is illegal to build a program containing these two clients.
2493 These rules are enforced by the GNAT binder, which also determines an
2494 elaboration order consistent with the Ada rules.
2496 The GNAT binder is run after all the object files for a program have
2497 been created. It is given the name of the main program unit, and from
2498 this it determines the set of units required by the program, by reading the
2499 corresponding ALI files. It generates error messages if the program is
2500 inconsistent or if no valid order of elaboration exists.
2502 If no errors are detected, the binder produces a main program, in Ada by
2503 default, that contains calls to the elaboration procedures of those
2504 compilation unit that require them, followed by
2505 a call to the main program. This Ada program is compiled to generate the
2506 object file for the main program. The name of
2507 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2508 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2511 Finally, the linker is used to build the resulting executable program,
2512 using the object from the main program from the bind step as well as the
2513 object files for the Ada units of the program.
2515 @node Mixed Language Programming
2516 @section Mixed Language Programming
2517 @cindex Mixed Language Programming
2520 This section describes how to develop a mixed-language program,
2521 specifically one that comprises units in both Ada and C.
2524 * Interfacing to C::
2525 * Calling Conventions::
2528 @node Interfacing to C
2529 @subsection Interfacing to C
2531 Interfacing Ada with a foreign language such as C involves using
2532 compiler directives to import and/or export entity definitions in each
2533 language---using @code{extern} statements in C, for instance, and the
2534 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2535 A full treatment of these topics is provided in Appendix B, section 1
2536 of the Ada Reference Manual.
2538 There are two ways to build a program using GNAT that contains some Ada
2539 sources and some foreign language sources, depending on whether or not
2540 the main subprogram is written in Ada. Here is a source example with
2541 the main subprogram in Ada:
2547 void print_num (int num)
2549 printf ("num is %d.\n", num);
2555 /* num_from_Ada is declared in my_main.adb */
2556 extern int num_from_Ada;
2560 return num_from_Ada;
2564 @smallexample @c ada
2566 procedure My_Main is
2568 -- Declare then export an Integer entity called num_from_Ada
2569 My_Num : Integer := 10;
2570 pragma Export (C, My_Num, "num_from_Ada");
2572 -- Declare an Ada function spec for Get_Num, then use
2573 -- C function get_num for the implementation.
2574 function Get_Num return Integer;
2575 pragma Import (C, Get_Num, "get_num");
2577 -- Declare an Ada procedure spec for Print_Num, then use
2578 -- C function print_num for the implementation.
2579 procedure Print_Num (Num : Integer);
2580 pragma Import (C, Print_Num, "print_num");
2583 Print_Num (Get_Num);
2589 To build this example, first compile the foreign language files to
2590 generate object files:
2592 ^gcc -c file1.c^gcc -c FILE1.C^
2593 ^gcc -c file2.c^gcc -c FILE2.C^
2597 Then, compile the Ada units to produce a set of object files and ALI
2600 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2604 Run the Ada binder on the Ada main program:
2606 gnatbind my_main.ali
2610 Link the Ada main program, the Ada objects and the other language
2613 gnatlink my_main.ali file1.o file2.o
2617 The last three steps can be grouped in a single command:
2619 gnatmake my_main.adb -largs file1.o file2.o
2622 @cindex Binder output file
2624 If the main program is in a language other than Ada, then you may have
2625 more than one entry point into the Ada subsystem. You must use a special
2626 binder option to generate callable routines that initialize and
2627 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2628 Calls to the initialization and finalization routines must be inserted
2629 in the main program, or some other appropriate point in the code. The
2630 call to initialize the Ada units must occur before the first Ada
2631 subprogram is called, and the call to finalize the Ada units must occur
2632 after the last Ada subprogram returns. The binder will place the
2633 initialization and finalization subprograms into the
2634 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2635 sources. To illustrate, we have the following example:
2639 extern void adainit (void);
2640 extern void adafinal (void);
2641 extern int add (int, int);
2642 extern int sub (int, int);
2644 int main (int argc, char *argv[])
2650 /* Should print "21 + 7 = 28" */
2651 printf ("%d + %d = %d\n", a, b, add (a, b));
2652 /* Should print "21 - 7 = 14" */
2653 printf ("%d - %d = %d\n", a, b, sub (a, b));
2659 @smallexample @c ada
2662 function Add (A, B : Integer) return Integer;
2663 pragma Export (C, Add, "add");
2667 package body Unit1 is
2668 function Add (A, B : Integer) return Integer is
2676 function Sub (A, B : Integer) return Integer;
2677 pragma Export (C, Sub, "sub");
2681 package body Unit2 is
2682 function Sub (A, B : Integer) return Integer is
2691 The build procedure for this application is similar to the last
2692 example's. First, compile the foreign language files to generate object
2695 ^gcc -c main.c^gcc -c main.c^
2699 Next, compile the Ada units to produce a set of object files and ALI
2702 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2703 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2707 Run the Ada binder on every generated ALI file. Make sure to use the
2708 @option{-n} option to specify a foreign main program:
2710 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2714 Link the Ada main program, the Ada objects and the foreign language
2715 objects. You need only list the last ALI file here:
2717 gnatlink unit2.ali main.o -o exec_file
2720 This procedure yields a binary executable called @file{exec_file}.
2724 Depending on the circumstances (for example when your non-Ada main object
2725 does not provide symbol @code{main}), you may also need to instruct the
2726 GNAT linker not to include the standard startup objects by passing the
2727 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2729 @node Calling Conventions
2730 @subsection Calling Conventions
2731 @cindex Foreign Languages
2732 @cindex Calling Conventions
2733 GNAT follows standard calling sequence conventions and will thus interface
2734 to any other language that also follows these conventions. The following
2735 Convention identifiers are recognized by GNAT:
2738 @cindex Interfacing to Ada
2739 @cindex Other Ada compilers
2740 @cindex Convention Ada
2742 This indicates that the standard Ada calling sequence will be
2743 used and all Ada data items may be passed without any limitations in the
2744 case where GNAT is used to generate both the caller and callee. It is also
2745 possible to mix GNAT generated code and code generated by another Ada
2746 compiler. In this case, the data types should be restricted to simple
2747 cases, including primitive types. Whether complex data types can be passed
2748 depends on the situation. Probably it is safe to pass simple arrays, such
2749 as arrays of integers or floats. Records may or may not work, depending
2750 on whether both compilers lay them out identically. Complex structures
2751 involving variant records, access parameters, tasks, or protected types,
2752 are unlikely to be able to be passed.
2754 Note that in the case of GNAT running
2755 on a platform that supports HP Ada 83, a higher degree of compatibility
2756 can be guaranteed, and in particular records are layed out in an identical
2757 manner in the two compilers. Note also that if output from two different
2758 compilers is mixed, the program is responsible for dealing with elaboration
2759 issues. Probably the safest approach is to write the main program in the
2760 version of Ada other than GNAT, so that it takes care of its own elaboration
2761 requirements, and then call the GNAT-generated adainit procedure to ensure
2762 elaboration of the GNAT components. Consult the documentation of the other
2763 Ada compiler for further details on elaboration.
2765 However, it is not possible to mix the tasking run time of GNAT and
2766 HP Ada 83, All the tasking operations must either be entirely within
2767 GNAT compiled sections of the program, or entirely within HP Ada 83
2768 compiled sections of the program.
2770 @cindex Interfacing to Assembly
2771 @cindex Convention Assembler
2773 Specifies assembler as the convention. In practice this has the
2774 same effect as convention Ada (but is not equivalent in the sense of being
2775 considered the same convention).
2777 @cindex Convention Asm
2780 Equivalent to Assembler.
2782 @cindex Interfacing to COBOL
2783 @cindex Convention COBOL
2786 Data will be passed according to the conventions described
2787 in section B.4 of the Ada Reference Manual.
2790 @cindex Interfacing to C
2791 @cindex Convention C
2793 Data will be passed according to the conventions described
2794 in section B.3 of the Ada Reference Manual.
2796 A note on interfacing to a C ``varargs'' function:
2797 @findex C varargs function
2798 @cindex Interfacing to C varargs function
2799 @cindex varargs function interfaces
2803 In C, @code{varargs} allows a function to take a variable number of
2804 arguments. There is no direct equivalent in this to Ada. One
2805 approach that can be used is to create a C wrapper for each
2806 different profile and then interface to this C wrapper. For
2807 example, to print an @code{int} value using @code{printf},
2808 create a C function @code{printfi} that takes two arguments, a
2809 pointer to a string and an int, and calls @code{printf}.
2810 Then in the Ada program, use pragma @code{Import} to
2811 interface to @code{printfi}.
2814 It may work on some platforms to directly interface to
2815 a @code{varargs} function by providing a specific Ada profile
2816 for a particular call. However, this does not work on
2817 all platforms, since there is no guarantee that the
2818 calling sequence for a two argument normal C function
2819 is the same as for calling a @code{varargs} C function with
2820 the same two arguments.
2823 @cindex Convention Default
2828 @cindex Convention External
2835 @cindex Interfacing to C++
2836 @cindex Convention C++
2837 @item C_Plus_Plus (or CPP)
2838 This stands for C++. For most purposes this is identical to C.
2839 See the separate description of the specialized GNAT pragmas relating to
2840 C++ interfacing for further details.
2844 @cindex Interfacing to Fortran
2845 @cindex Convention Fortran
2847 Data will be passed according to the conventions described
2848 in section B.5 of the Ada Reference Manual.
2851 This applies to an intrinsic operation, as defined in the Ada
2852 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2853 this means that the body of the subprogram is provided by the compiler itself,
2854 usually by means of an efficient code sequence, and that the user does not
2855 supply an explicit body for it. In an application program, the pragma may
2856 be applied to the following sets of names:
2860 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2861 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2862 two formal parameters. The
2863 first one must be a signed integer type or a modular type with a binary
2864 modulus, and the second parameter must be of type Natural.
2865 The return type must be the same as the type of the first argument. The size
2866 of this type can only be 8, 16, 32, or 64.
2869 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2870 The corresponding operator declaration must have parameters and result type
2871 that have the same root numeric type (for example, all three are long_float
2872 types). This simplifies the definition of operations that use type checking
2873 to perform dimensional checks:
2875 @smallexample @c ada
2876 type Distance is new Long_Float;
2877 type Time is new Long_Float;
2878 type Velocity is new Long_Float;
2879 function "/" (D : Distance; T : Time)
2881 pragma Import (Intrinsic, "/");
2885 This common idiom is often programmed with a generic definition and an
2886 explicit body. The pragma makes it simpler to introduce such declarations.
2887 It incurs no overhead in compilation time or code size, because it is
2888 implemented as a single machine instruction.
2891 General subprogram entities, to bind an Ada subprogram declaration to
2892 a compiler builtin by name with back-ends where such interfaces are
2893 available. A typical example is the set of ``__builtin'' functions
2894 exposed by the GCC back-end, as in the following example:
2896 @smallexample @c ada
2897 function builtin_sqrt (F : Float) return Float;
2898 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2901 Most of the GCC builtins are accessible this way, and as for other
2902 import conventions (e.g. C), it is the user's responsibility to ensure
2903 that the Ada subprogram profile matches the underlying builtin
2911 @cindex Convention Stdcall
2913 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2914 and specifies that the @code{Stdcall} calling sequence will be used,
2915 as defined by the NT API. Nevertheless, to ease building
2916 cross-platform bindings this convention will be handled as a @code{C} calling
2917 convention on non-Windows platforms.
2920 @cindex Convention DLL
2922 This is equivalent to @code{Stdcall}.
2925 @cindex Convention Win32
2927 This is equivalent to @code{Stdcall}.
2931 @cindex Convention Stubbed
2933 This is a special convention that indicates that the compiler
2934 should provide a stub body that raises @code{Program_Error}.
2938 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2939 that can be used to parametrize conventions and allow additional synonyms
2940 to be specified. For example if you have legacy code in which the convention
2941 identifier Fortran77 was used for Fortran, you can use the configuration
2944 @smallexample @c ada
2945 pragma Convention_Identifier (Fortran77, Fortran);
2949 And from now on the identifier Fortran77 may be used as a convention
2950 identifier (for example in an @code{Import} pragma) with the same
2954 @node Building Mixed Ada & C++ Programs
2955 @section Building Mixed Ada and C++ Programs
2958 A programmer inexperienced with mixed-language development may find that
2959 building an application containing both Ada and C++ code can be a
2960 challenge. This section gives a few
2961 hints that should make this task easier. The first section addresses
2962 the differences between interfacing with C and interfacing with C++.
2964 looks into the delicate problem of linking the complete application from
2965 its Ada and C++ parts. The last section gives some hints on how the GNAT
2966 run-time library can be adapted in order to allow inter-language dispatching
2967 with a new C++ compiler.
2970 * Interfacing to C++::
2971 * Linking a Mixed C++ & Ada Program::
2972 * A Simple Example::
2973 * Interfacing with C++ constructors::
2974 * Interfacing with C++ at the Class Level::
2977 @node Interfacing to C++
2978 @subsection Interfacing to C++
2981 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2982 generating code that is compatible with the G++ Application Binary
2983 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2986 Interfacing can be done at 3 levels: simple data, subprograms, and
2987 classes. In the first two cases, GNAT offers a specific @code{Convention
2988 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2989 Usually, C++ mangles the names of subprograms. To generate proper mangled
2990 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2991 This problem can also be addressed manually in two ways:
2995 by modifying the C++ code in order to force a C convention using
2996 the @code{extern "C"} syntax.
2999 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
3000 Link_Name argument of the pragma import.
3004 Interfacing at the class level can be achieved by using the GNAT specific
3005 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3006 gnat_rm, GNAT Reference Manual}, for additional information.
3008 @node Linking a Mixed C++ & Ada Program
3009 @subsection Linking a Mixed C++ & Ada Program
3012 Usually the linker of the C++ development system must be used to link
3013 mixed applications because most C++ systems will resolve elaboration
3014 issues (such as calling constructors on global class instances)
3015 transparently during the link phase. GNAT has been adapted to ease the
3016 use of a foreign linker for the last phase. Three cases can be
3021 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3022 The C++ linker can simply be called by using the C++ specific driver
3025 Note that if the C++ code uses inline functions, you will need to
3026 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3027 order to provide an existing function implementation that the Ada code can
3031 $ g++ -c -fkeep-inline-functions file1.C
3032 $ g++ -c -fkeep-inline-functions file2.C
3033 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3037 Using GNAT and G++ from two different GCC installations: If both
3038 compilers are on the @env{PATH}, the previous method may be used. It is
3039 important to note that environment variables such as
3040 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3041 @env{GCC_ROOT} will affect both compilers
3042 at the same time and may make one of the two compilers operate
3043 improperly if set during invocation of the wrong compiler. It is also
3044 very important that the linker uses the proper @file{libgcc.a} GCC
3045 library -- that is, the one from the C++ compiler installation. The
3046 implicit link command as suggested in the @command{gnatmake} command
3047 from the former example can be replaced by an explicit link command with
3048 the full-verbosity option in order to verify which library is used:
3051 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3053 If there is a problem due to interfering environment variables, it can
3054 be worked around by using an intermediate script. The following example
3055 shows the proper script to use when GNAT has not been installed at its
3056 default location and g++ has been installed at its default location:
3064 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3068 Using a non-GNU C++ compiler: The commands previously described can be
3069 used to insure that the C++ linker is used. Nonetheless, you need to add
3070 a few more parameters to the link command line, depending on the exception
3073 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3074 to the libgcc libraries are required:
3079 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3080 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3083 Where CC is the name of the non-GNU C++ compiler.
3085 If the @code{zero cost} exception mechanism is used, and the platform
3086 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3087 paths to more objects are required:
3092 CC `gcc -print-file-name=crtbegin.o` $* \
3093 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3094 `gcc -print-file-name=crtend.o`
3095 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3098 If the @code{zero cost} exception mechanism is used, and the platform
3099 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3100 Tru64 or AIX), the simple approach described above will not work and
3101 a pre-linking phase using GNAT will be necessary.
3105 Another alternative is to use the @command{gprbuild} multi-language builder
3106 which has a large knowledge base and knows how to link Ada and C++ code
3107 together automatically in most cases.
3109 @node A Simple Example
3110 @subsection A Simple Example
3112 The following example, provided as part of the GNAT examples, shows how
3113 to achieve procedural interfacing between Ada and C++ in both
3114 directions. The C++ class A has two methods. The first method is exported
3115 to Ada by the means of an extern C wrapper function. The second method
3116 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3117 a limited record with a layout comparable to the C++ class. The Ada
3118 subprogram, in turn, calls the C++ method. So, starting from the C++
3119 main program, the process passes back and forth between the two
3123 Here are the compilation commands:
3125 $ gnatmake -c simple_cpp_interface
3128 $ gnatbind -n simple_cpp_interface
3129 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3130 -lstdc++ ex7.o cpp_main.o
3134 Here are the corresponding sources:
3142 void adainit (void);
3143 void adafinal (void);
3144 void method1 (A *t);
3166 class A : public Origin @{
3168 void method1 (void);
3169 void method2 (int v);
3179 extern "C" @{ void ada_method2 (A *t, int v);@}
3181 void A::method1 (void)
3184 printf ("in A::method1, a_value = %d \n",a_value);
3188 void A::method2 (int v)
3190 ada_method2 (this, v);
3191 printf ("in A::method2, a_value = %d \n",a_value);
3198 printf ("in A::A, a_value = %d \n",a_value);
3202 @smallexample @c ada
3204 package body Simple_Cpp_Interface is
3206 procedure Ada_Method2 (This : in out A; V : Integer) is
3212 end Simple_Cpp_Interface;
3215 package Simple_Cpp_Interface is
3218 Vptr : System.Address;
3222 pragma Convention (C, A);
3224 procedure Method1 (This : in out A);
3225 pragma Import (C, Method1);
3227 procedure Ada_Method2 (This : in out A; V : Integer);
3228 pragma Export (C, Ada_Method2);
3230 end Simple_Cpp_Interface;
3233 @node Interfacing with C++ constructors
3234 @subsection Interfacing with C++ constructors
3237 In order to interface with C++ constructors GNAT provides the
3238 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3239 gnat_rm, GNAT Reference Manual}, for additional information).
3240 In this section we present some common uses of C++ constructors
3241 in mixed-languages programs in GNAT.
3243 Let us assume that we need to interface with the following
3251 @b{virtual} int Get_Value ();
3252 Root(); // Default constructor
3253 Root(int v); // 1st non-default constructor
3254 Root(int v, int w); // 2nd non-default constructor
3258 For this purpose we can write the following package spec (further
3259 information on how to build this spec is available in
3260 @ref{Interfacing with C++ at the Class Level} and
3261 @ref{Generating Ada Bindings for C and C++ headers}).
3263 @smallexample @c ada
3264 with Interfaces.C; use Interfaces.C;
3266 type Root is tagged limited record
3270 pragma Import (CPP, Root);
3272 function Get_Value (Obj : Root) return int;
3273 pragma Import (CPP, Get_Value);
3275 function Constructor return Root;
3276 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3278 function Constructor (v : Integer) return Root;
3279 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3281 function Constructor (v, w : Integer) return Root;
3282 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3286 On the Ada side the constructor is represented by a function (whose
3287 name is arbitrary) that returns the classwide type corresponding to
3288 the imported C++ class. Although the constructor is described as a
3289 function, it is typically a procedure with an extra implicit argument
3290 (the object being initialized) at the implementation level. GNAT
3291 issues the appropriate call, whatever it is, to get the object
3292 properly initialized.
3294 Constructors can only appear in the following contexts:
3298 On the right side of an initialization of an object of type @var{T}.
3300 On the right side of an initialization of a record component of type @var{T}.
3302 In an Ada 2005 limited aggregate.
3304 In an Ada 2005 nested limited aggregate.
3306 In an Ada 2005 limited aggregate that initializes an object built in
3307 place by an extended return statement.
3311 In a declaration of an object whose type is a class imported from C++,
3312 either the default C++ constructor is implicitly called by GNAT, or
3313 else the required C++ constructor must be explicitly called in the
3314 expression that initializes the object. For example:
3316 @smallexample @c ada
3318 Obj2 : Root := Constructor;
3319 Obj3 : Root := Constructor (v => 10);
3320 Obj4 : Root := Constructor (30, 40);
3323 The first two declarations are equivalent: in both cases the default C++
3324 constructor is invoked (in the former case the call to the constructor is
3325 implicit, and in the latter case the call is explicit in the object
3326 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3327 that takes an integer argument, and @code{Obj4} is initialized by the
3328 non-default C++ constructor that takes two integers.
3330 Let us derive the imported C++ class in the Ada side. For example:
3332 @smallexample @c ada
3333 type DT is new Root with record
3334 C_Value : Natural := 2009;
3338 In this case the components DT inherited from the C++ side must be
3339 initialized by a C++ constructor, and the additional Ada components
3340 of type DT are initialized by GNAT. The initialization of such an
3341 object is done either by default, or by means of a function returning
3342 an aggregate of type DT, or by means of an extension aggregate.
3344 @smallexample @c ada
3346 Obj6 : DT := Function_Returning_DT (50);
3347 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3350 The declaration of @code{Obj5} invokes the default constructors: the
3351 C++ default constructor of the parent type takes care of the initialization
3352 of the components inherited from Root, and GNAT takes care of the default
3353 initialization of the additional Ada components of type DT (that is,
3354 @code{C_Value} is initialized to value 2009). The order of invocation of
3355 the constructors is consistent with the order of elaboration required by
3356 Ada and C++. That is, the constructor of the parent type is always called
3357 before the constructor of the derived type.
3359 Let us now consider a record that has components whose type is imported
3360 from C++. For example:
3362 @smallexample @c ada
3363 type Rec1 is limited record
3364 Data1 : Root := Constructor (10);
3365 Value : Natural := 1000;
3368 type Rec2 (D : Integer := 20) is limited record
3370 Data2 : Root := Constructor (D, 30);
3374 The initialization of an object of type @code{Rec2} will call the
3375 non-default C++ constructors specified for the imported components.
3378 @smallexample @c ada
3382 Using Ada 2005 we can use limited aggregates to initialize an object
3383 invoking C++ constructors that differ from those specified in the type
3384 declarations. For example:
3386 @smallexample @c ada
3387 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3392 The above declaration uses an Ada 2005 limited aggregate to
3393 initialize @code{Obj9}, and the C++ constructor that has two integer
3394 arguments is invoked to initialize the @code{Data1} component instead
3395 of the constructor specified in the declaration of type @code{Rec1}. In
3396 Ada 2005 the box in the aggregate indicates that unspecified components
3397 are initialized using the expression (if any) available in the component
3398 declaration. That is, in this case discriminant @code{D} is initialized
3399 to value @code{20}, @code{Value} is initialized to value 1000, and the
3400 non-default C++ constructor that handles two integers takes care of
3401 initializing component @code{Data2} with values @code{20,30}.
3403 In Ada 2005 we can use the extended return statement to build the Ada
3404 equivalent to C++ non-default constructors. For example:
3406 @smallexample @c ada
3407 function Constructor (V : Integer) return Rec2 is
3409 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3412 -- Further actions required for construction of
3413 -- objects of type Rec2
3419 In this example the extended return statement construct is used to
3420 build in place the returned object whose components are initialized
3421 by means of a limited aggregate. Any further action associated with
3422 the constructor can be placed inside the construct.
3424 @node Interfacing with C++ at the Class Level
3425 @subsection Interfacing with C++ at the Class Level
3427 In this section we demonstrate the GNAT features for interfacing with
3428 C++ by means of an example making use of Ada 2005 abstract interface
3429 types. This example consists of a classification of animals; classes
3430 have been used to model our main classification of animals, and
3431 interfaces provide support for the management of secondary
3432 classifications. We first demonstrate a case in which the types and
3433 constructors are defined on the C++ side and imported from the Ada
3434 side, and latter the reverse case.
3436 The root of our derivation will be the @code{Animal} class, with a
3437 single private attribute (the @code{Age} of the animal) and two public
3438 primitives to set and get the value of this attribute.
3443 @b{virtual} void Set_Age (int New_Age);
3444 @b{virtual} int Age ();
3450 Abstract interface types are defined in C++ by means of classes with pure
3451 virtual functions and no data members. In our example we will use two
3452 interfaces that provide support for the common management of @code{Carnivore}
3453 and @code{Domestic} animals:
3456 @b{class} Carnivore @{
3458 @b{virtual} int Number_Of_Teeth () = 0;
3461 @b{class} Domestic @{
3463 @b{virtual void} Set_Owner (char* Name) = 0;
3467 Using these declarations, we can now say that a @code{Dog} is an animal that is
3468 both Carnivore and Domestic, that is:
3471 @b{class} Dog : Animal, Carnivore, Domestic @{
3473 @b{virtual} int Number_Of_Teeth ();
3474 @b{virtual} void Set_Owner (char* Name);
3476 Dog(); // Constructor
3483 In the following examples we will assume that the previous declarations are
3484 located in a file named @code{animals.h}. The following package demonstrates
3485 how to import these C++ declarations from the Ada side:
3487 @smallexample @c ada
3488 with Interfaces.C.Strings; use Interfaces.C.Strings;
3490 type Carnivore is interface;
3491 pragma Convention (C_Plus_Plus, Carnivore);
3492 function Number_Of_Teeth (X : Carnivore)
3493 return Natural is abstract;
3495 type Domestic is interface;
3496 pragma Convention (C_Plus_Plus, Set_Owner);
3498 (X : in out Domestic;
3499 Name : Chars_Ptr) is abstract;
3501 type Animal is tagged record
3504 pragma Import (C_Plus_Plus, Animal);
3506 procedure Set_Age (X : in out Animal; Age : Integer);
3507 pragma Import (C_Plus_Plus, Set_Age);
3509 function Age (X : Animal) return Integer;
3510 pragma Import (C_Plus_Plus, Age);
3512 type Dog is new Animal and Carnivore and Domestic with record
3513 Tooth_Count : Natural;
3514 Owner : String (1 .. 30);
3516 pragma Import (C_Plus_Plus, Dog);
3518 function Number_Of_Teeth (A : Dog) return Integer;
3519 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3521 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3522 pragma Import (C_Plus_Plus, Set_Owner);
3524 function New_Dog return Dog;
3525 pragma CPP_Constructor (New_Dog);
3526 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3530 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3531 interfacing with these C++ classes is easy. The only requirement is that all
3532 the primitives and components must be declared exactly in the same order in
3535 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3536 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3537 the arguments to the called primitives will be the same as for C++. For the
3538 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3539 to indicate that they have been defined on the C++ side; this is required
3540 because the dispatch table associated with these tagged types will be built
3541 in the C++ side and therefore will not contain the predefined Ada primitives
3542 which Ada would otherwise expect.
3544 As the reader can see there is no need to indicate the C++ mangled names
3545 associated with each subprogram because it is assumed that all the calls to
3546 these primitives will be dispatching calls. The only exception is the
3547 constructor, which must be registered with the compiler by means of
3548 @code{pragma CPP_Constructor} and needs to provide its associated C++
3549 mangled name because the Ada compiler generates direct calls to it.
3551 With the above packages we can now declare objects of type Dog on the Ada side
3552 and dispatch calls to the corresponding subprograms on the C++ side. We can
3553 also extend the tagged type Dog with further fields and primitives, and
3554 override some of its C++ primitives on the Ada side. For example, here we have
3555 a type derivation defined on the Ada side that inherits all the dispatching
3556 primitives of the ancestor from the C++ side.
3559 @b{with} Animals; @b{use} Animals;
3560 @b{package} Vaccinated_Animals @b{is}
3561 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3562 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3563 @b{end} Vaccinated_Animals;
3566 It is important to note that, because of the ABI compatibility, the programmer
3567 does not need to add any further information to indicate either the object
3568 layout or the dispatch table entry associated with each dispatching operation.
3570 Now let us define all the types and constructors on the Ada side and export
3571 them to C++, using the same hierarchy of our previous example:
3573 @smallexample @c ada
3574 with Interfaces.C.Strings;
3575 use Interfaces.C.Strings;
3577 type Carnivore is interface;
3578 pragma Convention (C_Plus_Plus, Carnivore);
3579 function Number_Of_Teeth (X : Carnivore)
3580 return Natural is abstract;
3582 type Domestic is interface;
3583 pragma Convention (C_Plus_Plus, Set_Owner);
3585 (X : in out Domestic;
3586 Name : Chars_Ptr) is abstract;
3588 type Animal is tagged record
3591 pragma Convention (C_Plus_Plus, Animal);
3593 procedure Set_Age (X : in out Animal; Age : Integer);
3594 pragma Export (C_Plus_Plus, Set_Age);
3596 function Age (X : Animal) return Integer;
3597 pragma Export (C_Plus_Plus, Age);
3599 type Dog is new Animal and Carnivore and Domestic with record
3600 Tooth_Count : Natural;
3601 Owner : String (1 .. 30);
3603 pragma Convention (C_Plus_Plus, Dog);
3605 function Number_Of_Teeth (A : Dog) return Integer;
3606 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3608 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3609 pragma Export (C_Plus_Plus, Set_Owner);
3611 function New_Dog return Dog'Class;
3612 pragma Export (C_Plus_Plus, New_Dog);
3616 Compared with our previous example the only difference is the use of
3617 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3618 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3619 nothing else to be done; as explained above, the only requirement is that all
3620 the primitives and components are declared in exactly the same order.
3622 For completeness, let us see a brief C++ main program that uses the
3623 declarations available in @code{animals.h} (presented in our first example) to
3624 import and use the declarations from the Ada side, properly initializing and
3625 finalizing the Ada run-time system along the way:
3628 @b{#include} "animals.h"
3629 @b{#include} <iostream>
3630 @b{using namespace} std;
3632 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3633 void Check_Domestic (Domestic *obj) @{@dots{}@}
3634 void Check_Animal (Animal *obj) @{@dots{}@}
3635 void Check_Dog (Dog *obj) @{@dots{}@}
3638 void adainit (void);
3639 void adafinal (void);
3645 Dog *obj = new_dog(); // Ada constructor
3646 Check_Carnivore (obj); // Check secondary DT
3647 Check_Domestic (obj); // Check secondary DT
3648 Check_Animal (obj); // Check primary DT
3649 Check_Dog (obj); // Check primary DT
3654 adainit (); test(); adafinal ();
3659 @node Comparison between GNAT and C/C++ Compilation Models
3660 @section Comparison between GNAT and C/C++ Compilation Models
3663 The GNAT model of compilation is close to the C and C++ models. You can
3664 think of Ada specs as corresponding to header files in C. As in C, you
3665 don't need to compile specs; they are compiled when they are used. The
3666 Ada @code{with} is similar in effect to the @code{#include} of a C
3669 One notable difference is that, in Ada, you may compile specs separately
3670 to check them for semantic and syntactic accuracy. This is not always
3671 possible with C headers because they are fragments of programs that have
3672 less specific syntactic or semantic rules.
3674 The other major difference is the requirement for running the binder,
3675 which performs two important functions. First, it checks for
3676 consistency. In C or C++, the only defense against assembling
3677 inconsistent programs lies outside the compiler, in a makefile, for
3678 example. The binder satisfies the Ada requirement that it be impossible
3679 to construct an inconsistent program when the compiler is used in normal
3682 @cindex Elaboration order control
3683 The other important function of the binder is to deal with elaboration
3684 issues. There are also elaboration issues in C++ that are handled
3685 automatically. This automatic handling has the advantage of being
3686 simpler to use, but the C++ programmer has no control over elaboration.
3687 Where @code{gnatbind} might complain there was no valid order of
3688 elaboration, a C++ compiler would simply construct a program that
3689 malfunctioned at run time.
3692 @node Comparison between GNAT and Conventional Ada Library Models
3693 @section Comparison between GNAT and Conventional Ada Library Models
3696 This section is intended for Ada programmers who have
3697 used an Ada compiler implementing the traditional Ada library
3698 model, as described in the Ada Reference Manual.
3700 @cindex GNAT library
3701 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3702 source files themselves acts as the library. Compiling Ada programs does
3703 not generate any centralized information, but rather an object file and
3704 a ALI file, which are of interest only to the binder and linker.
3705 In a traditional system, the compiler reads information not only from
3706 the source file being compiled, but also from the centralized library.
3707 This means that the effect of a compilation depends on what has been
3708 previously compiled. In particular:
3712 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3713 to the version of the unit most recently compiled into the library.
3716 Inlining is effective only if the necessary body has already been
3717 compiled into the library.
3720 Compiling a unit may obsolete other units in the library.
3724 In GNAT, compiling one unit never affects the compilation of any other
3725 units because the compiler reads only source files. Only changes to source
3726 files can affect the results of a compilation. In particular:
3730 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3731 to the source version of the unit that is currently accessible to the
3736 Inlining requires the appropriate source files for the package or
3737 subprogram bodies to be available to the compiler. Inlining is always
3738 effective, independent of the order in which units are complied.
3741 Compiling a unit never affects any other compilations. The editing of
3742 sources may cause previous compilations to be out of date if they
3743 depended on the source file being modified.
3747 The most important result of these differences is that order of compilation
3748 is never significant in GNAT. There is no situation in which one is
3749 required to do one compilation before another. What shows up as order of
3750 compilation requirements in the traditional Ada library becomes, in
3751 GNAT, simple source dependencies; in other words, there is only a set
3752 of rules saying what source files must be present when a file is
3756 @node Placement of temporary files
3757 @section Placement of temporary files
3758 @cindex Temporary files (user control over placement)
3761 GNAT creates temporary files in the directory designated by the environment
3762 variable @env{TMPDIR}.
3763 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3764 for detailed information on how environment variables are resolved.
3765 For most users the easiest way to make use of this feature is to simply
3766 define @env{TMPDIR} as a job level logical name).
3767 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3768 for compiler temporary files, then you can include something like the
3769 following command in your @file{LOGIN.COM} file:
3772 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3776 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3777 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3778 designated by @env{TEMP}.
3779 If none of these environment variables are defined then GNAT uses the
3780 directory designated by the logical name @code{SYS$SCRATCH:}
3781 (by default the user's home directory). If all else fails
3782 GNAT uses the current directory for temporary files.
3785 @c *************************
3786 @node Compiling Using gcc
3787 @chapter Compiling Using @command{gcc}
3790 This chapter discusses how to compile Ada programs using the @command{gcc}
3791 command. It also describes the set of switches
3792 that can be used to control the behavior of the compiler.
3794 * Compiling Programs::
3795 * Switches for gcc::
3796 * Search Paths and the Run-Time Library (RTL)::
3797 * Order of Compilation Issues::
3801 @node Compiling Programs
3802 @section Compiling Programs
3805 The first step in creating an executable program is to compile the units
3806 of the program using the @command{gcc} command. You must compile the
3811 the body file (@file{.adb}) for a library level subprogram or generic
3815 the spec file (@file{.ads}) for a library level package or generic
3816 package that has no body
3819 the body file (@file{.adb}) for a library level package
3820 or generic package that has a body
3825 You need @emph{not} compile the following files
3830 the spec of a library unit which has a body
3837 because they are compiled as part of compiling related units. GNAT
3839 when the corresponding body is compiled, and subunits when the parent is
3842 @cindex cannot generate code
3843 If you attempt to compile any of these files, you will get one of the
3844 following error messages (where @var{fff} is the name of the file you compiled):
3847 cannot generate code for file @var{fff} (package spec)
3848 to check package spec, use -gnatc
3850 cannot generate code for file @var{fff} (missing subunits)
3851 to check parent unit, use -gnatc
3853 cannot generate code for file @var{fff} (subprogram spec)
3854 to check subprogram spec, use -gnatc
3856 cannot generate code for file @var{fff} (subunit)
3857 to check subunit, use -gnatc
3861 As indicated by the above error messages, if you want to submit
3862 one of these files to the compiler to check for correct semantics
3863 without generating code, then use the @option{-gnatc} switch.
3865 The basic command for compiling a file containing an Ada unit is
3868 @c $ gcc -c @ovar{switches} @file{file name}
3869 @c Expanding @ovar macro inline (explanation in macro def comments)
3870 $ gcc -c @r{[}@var{switches}@r{]} @file{file name}
3874 where @var{file name} is the name of the Ada file (usually
3876 @file{.ads} for a spec or @file{.adb} for a body).
3879 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3881 The result of a successful compilation is an object file, which has the
3882 same name as the source file but an extension of @file{.o} and an Ada
3883 Library Information (ALI) file, which also has the same name as the
3884 source file, but with @file{.ali} as the extension. GNAT creates these
3885 two output files in the current directory, but you may specify a source
3886 file in any directory using an absolute or relative path specification
3887 containing the directory information.
3890 @command{gcc} is actually a driver program that looks at the extensions of
3891 the file arguments and loads the appropriate compiler. For example, the
3892 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3893 These programs are in directories known to the driver program (in some
3894 configurations via environment variables you set), but need not be in
3895 your path. The @command{gcc} driver also calls the assembler and any other
3896 utilities needed to complete the generation of the required object
3899 It is possible to supply several file names on the same @command{gcc}
3900 command. This causes @command{gcc} to call the appropriate compiler for
3901 each file. For example, the following command lists three separate
3902 files to be compiled:
3905 $ gcc -c x.adb y.adb z.c
3909 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3910 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3911 The compiler generates three object files @file{x.o}, @file{y.o} and
3912 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3913 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3916 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3919 @node Switches for gcc
3920 @section Switches for @command{gcc}
3923 The @command{gcc} command accepts switches that control the
3924 compilation process. These switches are fully described in this section.
3925 First we briefly list all the switches, in alphabetical order, then we
3926 describe the switches in more detail in functionally grouped sections.
3928 More switches exist for GCC than those documented here, especially
3929 for specific targets. However, their use is not recommended as
3930 they may change code generation in ways that are incompatible with
3931 the Ada run-time library, or can cause inconsistencies between
3935 * Output and Error Message Control::
3936 * Warning Message Control::
3937 * Debugging and Assertion Control::
3938 * Validity Checking::
3941 * Using gcc for Syntax Checking::
3942 * Using gcc for Semantic Checking::
3943 * Compiling Different Versions of Ada::
3944 * Character Set Control::
3945 * File Naming Control::
3946 * Subprogram Inlining Control::
3947 * Auxiliary Output Control::
3948 * Debugging Control::
3949 * Exception Handling Control::
3950 * Units to Sources Mapping Files::
3951 * Integrated Preprocessing::
3952 * Code Generation Control::
3961 @cindex @option{-b} (@command{gcc})
3962 @item -b @var{target}
3963 Compile your program to run on @var{target}, which is the name of a
3964 system configuration. You must have a GNAT cross-compiler built if
3965 @var{target} is not the same as your host system.
3968 @cindex @option{-B} (@command{gcc})
3969 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3970 from @var{dir} instead of the default location. Only use this switch
3971 when multiple versions of the GNAT compiler are available.
3972 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3973 GNU Compiler Collection (GCC)}, for further details. You would normally
3974 use the @option{-b} or @option{-V} switch instead.
3977 @cindex @option{-c} (@command{gcc})
3978 Compile. Always use this switch when compiling Ada programs.
3980 Note: for some other languages when using @command{gcc}, notably in
3981 the case of C and C++, it is possible to use
3982 use @command{gcc} without a @option{-c} switch to
3983 compile and link in one step. In the case of GNAT, you
3984 cannot use this approach, because the binder must be run
3985 and @command{gcc} cannot be used to run the GNAT binder.
3989 @cindex @option{-fno-inline} (@command{gcc})
3990 Suppresses all back-end inlining, even if other optimization or inlining
3992 This includes suppression of inlining that results
3993 from the use of the pragma @code{Inline_Always}.
3994 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3995 are ignored, and @option{-gnatn} and @option{-gnatN} have no
3996 effect if this switch is present.
3998 @item -fno-inline-functions
3999 @cindex @option{-fno-inline-functions} (@command{gcc})
4000 Suppresses automatic inlining of simple subprograms, which is enabled
4001 if @option{-O3} is used.
4003 @item -fno-inline-small-functions
4004 @cindex @option{-fno-inline-small-functions} (@command{gcc})
4005 Suppresses automatic inlining of small subprograms, which is enabled
4006 if @option{-O2} is used.
4008 @item -fno-inline-functions-called-once
4009 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
4010 Suppresses inlining of subprograms local to the unit and called once
4011 from within it, which is enabled if @option{-O1} is used.
4014 @cindex @option{-fno-ivopts} (@command{gcc})
4015 Suppresses high-level loop induction variable optimizations, which are
4016 enabled if @option{-O1} is used. These optimizations are generally
4017 profitable but, for some specific cases of loops with numerous uses
4018 of the iteration variable that follow a common pattern, they may end
4019 up destroying the regularity that could be exploited at a lower level
4020 and thus producing inferior code.
4022 @item -fno-strict-aliasing
4023 @cindex @option{-fno-strict-aliasing} (@command{gcc})
4024 Causes the compiler to avoid assumptions regarding non-aliasing
4025 of objects of different types. See
4026 @ref{Optimization and Strict Aliasing} for details.
4029 @cindex @option{-fstack-check} (@command{gcc})
4030 Activates stack checking.
4031 See @ref{Stack Overflow Checking} for details.
4034 @cindex @option{-fstack-usage} (@command{gcc})
4035 Makes the compiler output stack usage information for the program, on a
4036 per-function basis. See @ref{Static Stack Usage Analysis} for details.
4038 @item -fcallgraph-info@r{[}=su@r{]}
4039 @cindex @option{-fcallgraph-info} (@command{gcc})
4040 Makes the compiler output callgraph information for the program, on a
4041 per-file basis. The information is generated in the VCG format. It can
4042 be decorated with stack-usage per-node information.
4045 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4046 Generate debugging information. This information is stored in the object
4047 file and copied from there to the final executable file by the linker,
4048 where it can be read by the debugger. You must use the
4049 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4052 @cindex @option{-gnat83} (@command{gcc})
4053 Enforce Ada 83 restrictions.
4056 @cindex @option{-gnat95} (@command{gcc})
4057 Enforce Ada 95 restrictions.
4060 @cindex @option{-gnat05} (@command{gcc})
4061 Allow full Ada 2005 features.
4064 @cindex @option{-gnata} (@command{gcc})
4065 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4066 activated. Note that these pragmas can also be controlled using the
4067 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4068 It also activates pragmas @code{Check}, @code{Precondition}, and
4069 @code{Postcondition}. Note that these pragmas can also be controlled
4070 using the configuration pragma @code{Check_Policy}.
4073 @cindex @option{-gnatA} (@command{gcc})
4074 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4078 @cindex @option{-gnatb} (@command{gcc})
4079 Generate brief messages to @file{stderr} even if verbose mode set.
4082 @cindex @option{-gnatB} (@command{gcc})
4083 Assume no invalid (bad) values except for 'Valid attribute use
4084 (@pxref{Validity Checking}).
4087 @cindex @option{-gnatc} (@command{gcc})
4088 Check syntax and semantics only (no code generation attempted).
4091 @cindex @option{-gnatC} (@command{gcc})
4092 Generate CodePeer information (no code generation attempted).
4093 This switch will generate an intermediate representation suitable for
4094 use by CodePeer (@file{.scil} files). This switch is not compatible with
4095 code generation (it will, among other things, disable some switches such
4096 as -gnatn, and enable others such as -gnata).
4099 @cindex @option{-gnatd} (@command{gcc})
4100 Specify debug options for the compiler. The string of characters after
4101 the @option{-gnatd} specify the specific debug options. The possible
4102 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4103 compiler source file @file{debug.adb} for details of the implemented
4104 debug options. Certain debug options are relevant to applications
4105 programmers, and these are documented at appropriate points in this
4110 @cindex @option{-gnatD[nn]} (@command{gcc})
4113 @item /XDEBUG /LXDEBUG=nnn
4115 Create expanded source files for source level debugging. This switch
4116 also suppress generation of cross-reference information
4117 (see @option{-gnatx}).
4119 @item -gnatec=@var{path}
4120 @cindex @option{-gnatec} (@command{gcc})
4121 Specify a configuration pragma file
4123 (the equal sign is optional)
4125 (@pxref{The Configuration Pragmas Files}).
4127 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4128 @cindex @option{-gnateD} (@command{gcc})
4129 Defines a symbol, associated with @var{value}, for preprocessing.
4130 (@pxref{Integrated Preprocessing}).
4133 @cindex @option{-gnatef} (@command{gcc})
4134 Display full source path name in brief error messages.
4137 @cindex @option{-gnateG} (@command{gcc})
4138 Save result of preprocessing in a text file.
4140 @item -gnatem=@var{path}
4141 @cindex @option{-gnatem} (@command{gcc})
4142 Specify a mapping file
4144 (the equal sign is optional)
4146 (@pxref{Units to Sources Mapping Files}).
4148 @item -gnatep=@var{file}
4149 @cindex @option{-gnatep} (@command{gcc})
4150 Specify a preprocessing data file
4152 (the equal sign is optional)
4154 (@pxref{Integrated Preprocessing}).
4157 @cindex @option{-gnateS} (@command{gcc})
4158 Generate SCO (Source Coverage Obligation) information in the ALI
4159 file. This information is used by advanced coverage tools. See
4160 unit @file{SCOs} in the compiler sources for details in files
4161 @file{scos.ads} and @file{scos.adb}.
4164 @cindex @option{-gnatE} (@command{gcc})
4165 Full dynamic elaboration checks.
4168 @cindex @option{-gnatf} (@command{gcc})
4169 Full errors. Multiple errors per line, all undefined references, do not
4170 attempt to suppress cascaded errors.
4173 @cindex @option{-gnatF} (@command{gcc})
4174 Externals names are folded to all uppercase.
4176 @item ^-gnatg^/GNAT_INTERNAL^
4177 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4178 Internal GNAT implementation mode. This should not be used for
4179 applications programs, it is intended only for use by the compiler
4180 and its run-time library. For documentation, see the GNAT sources.
4181 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4182 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4183 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4184 so that all standard warnings and all standard style options are turned on.
4185 All warnings and style messages are treated as errors.
4189 @cindex @option{-gnatG[nn]} (@command{gcc})
4192 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4194 List generated expanded code in source form.
4196 @item ^-gnath^/HELP^
4197 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4198 Output usage information. The output is written to @file{stdout}.
4200 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4201 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4202 Identifier character set
4204 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4206 For details of the possible selections for @var{c},
4207 see @ref{Character Set Control}.
4209 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4210 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4211 Ignore representation clauses. When this switch is used,
4212 representation clauses are treated as comments. This is useful
4213 when initially porting code where you want to ignore rep clause
4214 problems, and also for compiling foreign code (particularly
4215 for use with ASIS). The representation clauses that are ignored
4216 are: enumeration_representation_clause, record_representation_clause,
4217 and attribute_definition_clause for the following attributes:
4218 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4219 Object_Size, Size, Small, Stream_Size, and Value_Size.
4220 Note that this option should be used only for compiling -- the
4221 code is likely to malfunction at run time.
4224 @cindex @option{-gnatjnn} (@command{gcc})
4225 Reformat error messages to fit on nn character lines
4227 @item -gnatk=@var{n}
4228 @cindex @option{-gnatk} (@command{gcc})
4229 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4232 @cindex @option{-gnatl} (@command{gcc})
4233 Output full source listing with embedded error messages.
4236 @cindex @option{-gnatL} (@command{gcc})
4237 Used in conjunction with -gnatG or -gnatD to intersperse original
4238 source lines (as comment lines with line numbers) in the expanded
4241 @item -gnatm=@var{n}
4242 @cindex @option{-gnatm} (@command{gcc})
4243 Limit number of detected error or warning messages to @var{n}
4244 where @var{n} is in the range 1..999999. The default setting if
4245 no switch is given is 9999. If the number of warnings reaches this
4246 limit, then a message is output and further warnings are suppressed,
4247 but the compilation is continued. If the number of error messages
4248 reaches this limit, then a message is output and the compilation
4249 is abandoned. The equal sign here is optional. A value of zero
4250 means that no limit applies.
4253 @cindex @option{-gnatn} (@command{gcc})
4254 Activate inlining for subprograms for which
4255 pragma @code{inline} is specified. This inlining is performed
4256 by the GCC back-end.
4259 @cindex @option{-gnatN} (@command{gcc})
4260 Activate front end inlining for subprograms for which
4261 pragma @code{Inline} is specified. This inlining is performed
4262 by the front end and will be visible in the
4263 @option{-gnatG} output.
4265 When using a gcc-based back end (in practice this means using any version
4266 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4267 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4268 Historically front end inlining was more extensive than the gcc back end
4269 inlining, but that is no longer the case.
4272 @cindex @option{-gnato} (@command{gcc})
4273 Enable numeric overflow checking (which is not normally enabled by
4274 default). Note that division by zero is a separate check that is not
4275 controlled by this switch (division by zero checking is on by default).
4278 @cindex @option{-gnatp} (@command{gcc})
4279 Suppress all checks. See @ref{Run-Time Checks} for details. This switch
4280 has no effect if cancelled by a subsequent @option{-gnat-p} switch.
4283 @cindex @option{-gnat-p} (@command{gcc})
4284 Cancel effect of previous @option{-gnatp} switch.
4287 @cindex @option{-gnatP} (@command{gcc})
4288 Enable polling. This is required on some systems (notably Windows NT) to
4289 obtain asynchronous abort and asynchronous transfer of control capability.
4290 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4294 @cindex @option{-gnatq} (@command{gcc})
4295 Don't quit. Try semantics, even if parse errors.
4298 @cindex @option{-gnatQ} (@command{gcc})
4299 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4302 @cindex @option{-gnatr} (@command{gcc})
4303 Treat pragma Restrictions as Restriction_Warnings.
4305 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4306 @cindex @option{-gnatR} (@command{gcc})
4307 Output representation information for declared types and objects.
4310 @cindex @option{-gnats} (@command{gcc})
4314 @cindex @option{-gnatS} (@command{gcc})
4315 Print package Standard.
4318 @cindex @option{-gnatt} (@command{gcc})
4319 Generate tree output file.
4321 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4322 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4323 All compiler tables start at @var{nnn} times usual starting size.
4326 @cindex @option{-gnatu} (@command{gcc})
4327 List units for this compilation.
4330 @cindex @option{-gnatU} (@command{gcc})
4331 Tag all error messages with the unique string ``error:''
4334 @cindex @option{-gnatv} (@command{gcc})
4335 Verbose mode. Full error output with source lines to @file{stdout}.
4338 @cindex @option{-gnatV} (@command{gcc})
4339 Control level of validity checking (@pxref{Validity Checking}).
4341 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4342 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4344 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4345 the exact warnings that
4346 are enabled or disabled (@pxref{Warning Message Control}).
4348 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4349 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4350 Wide character encoding method
4352 (@var{e}=n/h/u/s/e/8).
4355 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4359 @cindex @option{-gnatx} (@command{gcc})
4360 Suppress generation of cross-reference information.
4362 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4363 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4364 Enable built-in style checks (@pxref{Style Checking}).
4366 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4367 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4368 Distribution stub generation and compilation
4370 (@var{m}=r/c for receiver/caller stubs).
4373 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4374 to be generated and compiled).
4377 @item ^-I^/SEARCH=^@var{dir}
4378 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4380 Direct GNAT to search the @var{dir} directory for source files needed by
4381 the current compilation
4382 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4384 @item ^-I-^/NOCURRENT_DIRECTORY^
4385 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4387 Except for the source file named in the command line, do not look for source
4388 files in the directory containing the source file named in the command line
4389 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4393 @cindex @option{-mbig-switch} (@command{gcc})
4394 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4395 This standard gcc switch causes the compiler to use larger offsets in its
4396 jump table representation for @code{case} statements.
4397 This may result in less efficient code, but is sometimes necessary
4398 (for example on HP-UX targets)
4399 @cindex HP-UX and @option{-mbig-switch} option
4400 in order to compile large and/or nested @code{case} statements.
4403 @cindex @option{-o} (@command{gcc})
4404 This switch is used in @command{gcc} to redirect the generated object file
4405 and its associated ALI file. Beware of this switch with GNAT, because it may
4406 cause the object file and ALI file to have different names which in turn
4407 may confuse the binder and the linker.
4411 @cindex @option{-nostdinc} (@command{gcc})
4412 Inhibit the search of the default location for the GNAT Run Time
4413 Library (RTL) source files.
4416 @cindex @option{-nostdlib} (@command{gcc})
4417 Inhibit the search of the default location for the GNAT Run Time
4418 Library (RTL) ALI files.
4422 @c Expanding @ovar macro inline (explanation in macro def comments)
4423 @item -O@r{[}@var{n}@r{]}
4424 @cindex @option{-O} (@command{gcc})
4425 @var{n} controls the optimization level.
4429 No optimization, the default setting if no @option{-O} appears
4432 Normal optimization, the default if you specify @option{-O} without
4433 an operand. A good compromise between code quality and compilation
4437 Extensive optimization, may improve execution time, possibly at the cost of
4438 substantially increased compilation time.
4441 Same as @option{-O2}, and also includes inline expansion for small subprograms
4445 Optimize space usage
4449 See also @ref{Optimization Levels}.
4454 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4455 Equivalent to @option{/OPTIMIZE=NONE}.
4456 This is the default behavior in the absence of an @option{/OPTIMIZE}
4459 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4460 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4461 Selects the level of optimization for your program. The supported
4462 keywords are as follows:
4465 Perform most optimizations, including those that
4467 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4468 without keyword options.
4471 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4474 Perform some optimizations, but omit ones that are costly.
4477 Same as @code{SOME}.
4480 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4481 automatic inlining of small subprograms within a unit
4484 Try to unroll loops. This keyword may be specified together with
4485 any keyword above other than @code{NONE}. Loop unrolling
4486 usually, but not always, improves the performance of programs.
4489 Optimize space usage
4493 See also @ref{Optimization Levels}.
4497 @item -pass-exit-codes
4498 @cindex @option{-pass-exit-codes} (@command{gcc})
4499 Catch exit codes from the compiler and use the most meaningful as
4503 @item --RTS=@var{rts-path}
4504 @cindex @option{--RTS} (@command{gcc})
4505 Specifies the default location of the runtime library. Same meaning as the
4506 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4509 @cindex @option{^-S^/ASM^} (@command{gcc})
4510 ^Used in place of @option{-c} to^Used to^
4511 cause the assembler source file to be
4512 generated, using @file{^.s^.S^} as the extension,
4513 instead of the object file.
4514 This may be useful if you need to examine the generated assembly code.
4516 @item ^-fverbose-asm^/VERBOSE_ASM^
4517 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4518 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4519 to cause the generated assembly code file to be annotated with variable
4520 names, making it significantly easier to follow.
4523 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4524 Show commands generated by the @command{gcc} driver. Normally used only for
4525 debugging purposes or if you need to be sure what version of the
4526 compiler you are executing.
4530 @cindex @option{-V} (@command{gcc})
4531 Execute @var{ver} version of the compiler. This is the @command{gcc}
4532 version, not the GNAT version.
4535 @item ^-w^/NO_BACK_END_WARNINGS^
4536 @cindex @option{-w} (@command{gcc})
4537 Turn off warnings generated by the back end of the compiler. Use of
4538 this switch also causes the default for front end warnings to be set
4539 to suppress (as though @option{-gnatws} had appeared at the start of
4545 @c Combining qualifiers does not work on VMS
4546 You may combine a sequence of GNAT switches into a single switch. For
4547 example, the combined switch
4549 @cindex Combining GNAT switches
4555 is equivalent to specifying the following sequence of switches:
4558 -gnato -gnatf -gnati3
4563 The following restrictions apply to the combination of switches
4568 The switch @option{-gnatc} if combined with other switches must come
4569 first in the string.
4572 The switch @option{-gnats} if combined with other switches must come
4573 first in the string.
4577 ^^@option{/DISTRIBUTION_STUBS=},^
4578 @option{-gnatzc} and @option{-gnatzr} may not be combined with any other
4579 switches, and only one of them may appear in the command line.
4582 The switch @option{-gnat-p} may not be combined with any other switch.
4586 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4587 switch), then all further characters in the switch are interpreted
4588 as style modifiers (see description of @option{-gnaty}).
4591 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4592 switch), then all further characters in the switch are interpreted
4593 as debug flags (see description of @option{-gnatd}).
4596 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4597 switch), then all further characters in the switch are interpreted
4598 as warning mode modifiers (see description of @option{-gnatw}).
4601 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4602 switch), then all further characters in the switch are interpreted
4603 as validity checking options (@pxref{Validity Checking}).
4606 Option ``em'', ``ec'', ``ep'', ``l='' and ``R'' must be the last options in
4607 a combined list of options.
4611 @node Output and Error Message Control
4612 @subsection Output and Error Message Control
4616 The standard default format for error messages is called ``brief format''.
4617 Brief format messages are written to @file{stderr} (the standard error
4618 file) and have the following form:
4621 e.adb:3:04: Incorrect spelling of keyword "function"
4622 e.adb:4:20: ";" should be "is"
4626 The first integer after the file name is the line number in the file,
4627 and the second integer is the column number within the line.
4629 @code{GPS} can parse the error messages
4630 and point to the referenced character.
4632 The following switches provide control over the error message
4638 @cindex @option{-gnatv} (@command{gcc})
4641 The v stands for verbose.
4643 The effect of this setting is to write long-format error
4644 messages to @file{stdout} (the standard output file.
4645 The same program compiled with the
4646 @option{-gnatv} switch would generate:
4650 3. funcion X (Q : Integer)
4652 >>> Incorrect spelling of keyword "function"
4655 >>> ";" should be "is"
4660 The vertical bar indicates the location of the error, and the @samp{>>>}
4661 prefix can be used to search for error messages. When this switch is
4662 used the only source lines output are those with errors.
4665 @cindex @option{-gnatl} (@command{gcc})
4667 The @code{l} stands for list.
4669 This switch causes a full listing of
4670 the file to be generated. In the case where a body is
4671 compiled, the corresponding spec is also listed, along
4672 with any subunits. Typical output from compiling a package
4673 body @file{p.adb} might look like:
4675 @smallexample @c ada
4679 1. package body p is
4681 3. procedure a is separate;
4692 2. pragma Elaborate_Body
4716 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4717 standard output is redirected, a brief summary is written to
4718 @file{stderr} (standard error) giving the number of error messages and
4719 warning messages generated.
4721 @item -^gnatl^OUTPUT_FILE^=file
4722 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4723 This has the same effect as @option{-gnatl} except that the output is
4724 written to a file instead of to standard output. If the given name
4725 @file{fname} does not start with a period, then it is the full name
4726 of the file to be written. If @file{fname} is an extension, it is
4727 appended to the name of the file being compiled. For example, if
4728 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4729 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4732 @cindex @option{-gnatU} (@command{gcc})
4733 This switch forces all error messages to be preceded by the unique
4734 string ``error:''. This means that error messages take a few more
4735 characters in space, but allows easy searching for and identification
4739 @cindex @option{-gnatb} (@command{gcc})
4741 The @code{b} stands for brief.
4743 This switch causes GNAT to generate the
4744 brief format error messages to @file{stderr} (the standard error
4745 file) as well as the verbose
4746 format message or full listing (which as usual is written to
4747 @file{stdout} (the standard output file).
4749 @item -gnatm=@var{n}
4750 @cindex @option{-gnatm} (@command{gcc})
4752 The @code{m} stands for maximum.
4754 @var{n} is a decimal integer in the
4755 range of 1 to 999999 and limits the number of error or warning
4756 messages to be generated. For example, using
4757 @option{-gnatm2} might yield
4760 e.adb:3:04: Incorrect spelling of keyword "function"
4761 e.adb:5:35: missing ".."
4762 fatal error: maximum number of errors detected
4763 compilation abandoned
4767 The default setting if
4768 no switch is given is 9999. If the number of warnings reaches this
4769 limit, then a message is output and further warnings are suppressed,
4770 but the compilation is continued. If the number of error messages
4771 reaches this limit, then a message is output and the compilation
4772 is abandoned. A value of zero means that no limit applies.
4775 Note that the equal sign is optional, so the switches
4776 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4779 @cindex @option{-gnatf} (@command{gcc})
4780 @cindex Error messages, suppressing
4782 The @code{f} stands for full.
4784 Normally, the compiler suppresses error messages that are likely to be
4785 redundant. This switch causes all error
4786 messages to be generated. In particular, in the case of
4787 references to undefined variables. If a given variable is referenced
4788 several times, the normal format of messages is
4790 e.adb:7:07: "V" is undefined (more references follow)
4794 where the parenthetical comment warns that there are additional
4795 references to the variable @code{V}. Compiling the same program with the
4796 @option{-gnatf} switch yields
4799 e.adb:7:07: "V" is undefined
4800 e.adb:8:07: "V" is undefined
4801 e.adb:8:12: "V" is undefined
4802 e.adb:8:16: "V" is undefined
4803 e.adb:9:07: "V" is undefined
4804 e.adb:9:12: "V" is undefined
4808 The @option{-gnatf} switch also generates additional information for
4809 some error messages. Some examples are:
4813 Details on possibly non-portable unchecked conversion
4815 List possible interpretations for ambiguous calls
4817 Additional details on incorrect parameters
4821 @cindex @option{-gnatjnn} (@command{gcc})
4822 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4823 with continuation lines are treated as though the continuation lines were
4824 separate messages (and so a warning with two continuation lines counts as
4825 three warnings, and is listed as three separate messages).
4827 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4828 messages are output in a different manner. A message and all its continuation
4829 lines are treated as a unit, and count as only one warning or message in the
4830 statistics totals. Furthermore, the message is reformatted so that no line
4831 is longer than nn characters.
4834 @cindex @option{-gnatq} (@command{gcc})
4836 The @code{q} stands for quit (really ``don't quit'').
4838 In normal operation mode, the compiler first parses the program and
4839 determines if there are any syntax errors. If there are, appropriate
4840 error messages are generated and compilation is immediately terminated.
4842 GNAT to continue with semantic analysis even if syntax errors have been
4843 found. This may enable the detection of more errors in a single run. On
4844 the other hand, the semantic analyzer is more likely to encounter some
4845 internal fatal error when given a syntactically invalid tree.
4848 @cindex @option{-gnatQ} (@command{gcc})
4849 In normal operation mode, the @file{ALI} file is not generated if any
4850 illegalities are detected in the program. The use of @option{-gnatQ} forces
4851 generation of the @file{ALI} file. This file is marked as being in
4852 error, so it cannot be used for binding purposes, but it does contain
4853 reasonably complete cross-reference information, and thus may be useful
4854 for use by tools (e.g., semantic browsing tools or integrated development
4855 environments) that are driven from the @file{ALI} file. This switch
4856 implies @option{-gnatq}, since the semantic phase must be run to get a
4857 meaningful ALI file.
4859 In addition, if @option{-gnatt} is also specified, then the tree file is
4860 generated even if there are illegalities. It may be useful in this case
4861 to also specify @option{-gnatq} to ensure that full semantic processing
4862 occurs. The resulting tree file can be processed by ASIS, for the purpose
4863 of providing partial information about illegal units, but if the error
4864 causes the tree to be badly malformed, then ASIS may crash during the
4867 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4868 being in error, @command{gnatmake} will attempt to recompile the source when it
4869 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4871 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4872 since ALI files are never generated if @option{-gnats} is set.
4876 @node Warning Message Control
4877 @subsection Warning Message Control
4878 @cindex Warning messages
4880 In addition to error messages, which correspond to illegalities as defined
4881 in the Ada Reference Manual, the compiler detects two kinds of warning
4884 First, the compiler considers some constructs suspicious and generates a
4885 warning message to alert you to a possible error. Second, if the
4886 compiler detects a situation that is sure to raise an exception at
4887 run time, it generates a warning message. The following shows an example
4888 of warning messages:
4890 e.adb:4:24: warning: creation of object may raise Storage_Error
4891 e.adb:10:17: warning: static value out of range
4892 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4896 GNAT considers a large number of situations as appropriate
4897 for the generation of warning messages. As always, warnings are not
4898 definite indications of errors. For example, if you do an out-of-range
4899 assignment with the deliberate intention of raising a
4900 @code{Constraint_Error} exception, then the warning that may be
4901 issued does not indicate an error. Some of the situations for which GNAT
4902 issues warnings (at least some of the time) are given in the following
4903 list. This list is not complete, and new warnings are often added to
4904 subsequent versions of GNAT. The list is intended to give a general idea
4905 of the kinds of warnings that are generated.
4909 Possible infinitely recursive calls
4912 Out-of-range values being assigned
4915 Possible order of elaboration problems
4918 Assertions (pragma Assert) that are sure to fail
4924 Address clauses with possibly unaligned values, or where an attempt is
4925 made to overlay a smaller variable with a larger one.
4928 Fixed-point type declarations with a null range
4931 Direct_IO or Sequential_IO instantiated with a type that has access values
4934 Variables that are never assigned a value
4937 Variables that are referenced before being initialized
4940 Task entries with no corresponding @code{accept} statement
4943 Duplicate accepts for the same task entry in a @code{select}
4946 Objects that take too much storage
4949 Unchecked conversion between types of differing sizes
4952 Missing @code{return} statement along some execution path in a function
4955 Incorrect (unrecognized) pragmas
4958 Incorrect external names
4961 Allocation from empty storage pool
4964 Potentially blocking operation in protected type
4967 Suspicious parenthesization of expressions
4970 Mismatching bounds in an aggregate
4973 Attempt to return local value by reference
4976 Premature instantiation of a generic body
4979 Attempt to pack aliased components
4982 Out of bounds array subscripts
4985 Wrong length on string assignment
4988 Violations of style rules if style checking is enabled
4991 Unused @code{with} clauses
4994 @code{Bit_Order} usage that does not have any effect
4997 @code{Standard.Duration} used to resolve universal fixed expression
5000 Dereference of possibly null value
5003 Declaration that is likely to cause storage error
5006 Internal GNAT unit @code{with}'ed by application unit
5009 Values known to be out of range at compile time
5012 Unreferenced labels and variables
5015 Address overlays that could clobber memory
5018 Unexpected initialization when address clause present
5021 Bad alignment for address clause
5024 Useless type conversions
5027 Redundant assignment statements and other redundant constructs
5030 Useless exception handlers
5033 Accidental hiding of name by child unit
5036 Access before elaboration detected at compile time
5039 A range in a @code{for} loop that is known to be null or might be null
5044 The following section lists compiler switches that are available
5045 to control the handling of warning messages. It is also possible
5046 to exercise much finer control over what warnings are issued and
5047 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5048 gnat_rm, GNAT Reference manual}.
5053 @emph{Activate all optional errors.}
5054 @cindex @option{-gnatwa} (@command{gcc})
5055 This switch activates most optional warning messages, see remaining list
5056 in this section for details on optional warning messages that can be
5057 individually controlled. The warnings that are not turned on by this
5059 @option{-gnatwd} (implicit dereferencing),
5060 @option{-gnatwh} (hiding),
5061 @option{-gnatwl} (elaboration warnings),
5062 @option{-gnatw.o} (warn on values set by out parameters ignored)
5063 and @option{-gnatwt} (tracking of deleted conditional code).
5064 All other optional warnings are turned on.
5067 @emph{Suppress all optional errors.}
5068 @cindex @option{-gnatwA} (@command{gcc})
5069 This switch suppresses all optional warning messages, see remaining list
5070 in this section for details on optional warning messages that can be
5071 individually controlled.
5074 @emph{Activate warnings on failing assertions.}
5075 @cindex @option{-gnatw.a} (@command{gcc})
5076 @cindex Assert failures
5077 This switch activates warnings for assertions where the compiler can tell at
5078 compile time that the assertion will fail. Note that this warning is given
5079 even if assertions are disabled. The default is that such warnings are
5083 @emph{Suppress warnings on failing assertions.}
5084 @cindex @option{-gnatw.A} (@command{gcc})
5085 @cindex Assert failures
5086 This switch suppresses warnings for assertions where the compiler can tell at
5087 compile time that the assertion will fail.
5090 @emph{Activate warnings on bad fixed values.}
5091 @cindex @option{-gnatwb} (@command{gcc})
5092 @cindex Bad fixed values
5093 @cindex Fixed-point Small value
5095 This switch activates warnings for static fixed-point expressions whose
5096 value is not an exact multiple of Small. Such values are implementation
5097 dependent, since an implementation is free to choose either of the multiples
5098 that surround the value. GNAT always chooses the closer one, but this is not
5099 required behavior, and it is better to specify a value that is an exact
5100 multiple, ensuring predictable execution. The default is that such warnings
5104 @emph{Suppress warnings on bad fixed values.}
5105 @cindex @option{-gnatwB} (@command{gcc})
5106 This switch suppresses warnings for static fixed-point expressions whose
5107 value is not an exact multiple of Small.
5110 @emph{Activate warnings on biased representation.}
5111 @cindex @option{-gnatw.b} (@command{gcc})
5112 @cindex Biased representation
5113 This switch activates warnings when a size clause, value size clause, component
5114 clause, or component size clause forces the use of biased representation for an
5115 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5116 to represent 10/11). The default is that such warnings are generated.
5119 @emph{Suppress warnings on biased representation.}
5120 @cindex @option{-gnatwB} (@command{gcc})
5121 This switch suppresses warnings for representation clauses that force the use
5122 of biased representation.
5125 @emph{Activate warnings on conditionals.}
5126 @cindex @option{-gnatwc} (@command{gcc})
5127 @cindex Conditionals, constant
5128 This switch activates warnings for conditional expressions used in
5129 tests that are known to be True or False at compile time. The default
5130 is that such warnings are not generated.
5131 Note that this warning does
5132 not get issued for the use of boolean variables or constants whose
5133 values are known at compile time, since this is a standard technique
5134 for conditional compilation in Ada, and this would generate too many
5135 false positive warnings.
5137 This warning option also activates a special test for comparisons using
5138 the operators ``>='' and`` <=''.
5139 If the compiler can tell that only the equality condition is possible,
5140 then it will warn that the ``>'' or ``<'' part of the test
5141 is useless and that the operator could be replaced by ``=''.
5142 An example would be comparing a @code{Natural} variable <= 0.
5144 This warning option also generates warnings if
5145 one or both tests is optimized away in a membership test for integer
5146 values if the result can be determined at compile time. Range tests on
5147 enumeration types are not included, since it is common for such tests
5148 to include an end point.
5150 This warning can also be turned on using @option{-gnatwa}.
5153 @emph{Suppress warnings on conditionals.}
5154 @cindex @option{-gnatwC} (@command{gcc})
5155 This switch suppresses warnings for conditional expressions used in
5156 tests that are known to be True or False at compile time.
5159 @emph{Activate warnings on missing component clauses.}
5160 @cindex @option{-gnatw.c} (@command{gcc})
5161 @cindex Component clause, missing
5162 This switch activates warnings for record components where a record
5163 representation clause is present and has component clauses for the
5164 majority, but not all, of the components. A warning is given for each
5165 component for which no component clause is present.
5167 This warning can also be turned on using @option{-gnatwa}.
5170 @emph{Suppress warnings on missing component clauses.}
5171 @cindex @option{-gnatwC} (@command{gcc})
5172 This switch suppresses warnings for record components that are
5173 missing a component clause in the situation described above.
5176 @emph{Activate warnings on implicit dereferencing.}
5177 @cindex @option{-gnatwd} (@command{gcc})
5178 If this switch is set, then the use of a prefix of an access type
5179 in an indexed component, slice, or selected component without an
5180 explicit @code{.all} will generate a warning. With this warning
5181 enabled, access checks occur only at points where an explicit
5182 @code{.all} appears in the source code (assuming no warnings are
5183 generated as a result of this switch). The default is that such
5184 warnings are not generated.
5185 Note that @option{-gnatwa} does not affect the setting of
5186 this warning option.
5189 @emph{Suppress warnings on implicit dereferencing.}
5190 @cindex @option{-gnatwD} (@command{gcc})
5191 @cindex Implicit dereferencing
5192 @cindex Dereferencing, implicit
5193 This switch suppresses warnings for implicit dereferences in
5194 indexed components, slices, and selected components.
5197 @emph{Treat warnings and style checks as errors.}
5198 @cindex @option{-gnatwe} (@command{gcc})
5199 @cindex Warnings, treat as error
5200 This switch causes warning messages and style check messages to be
5202 The warning string still appears, but the warning messages are counted
5203 as errors, and prevent the generation of an object file. Note that this
5204 is the only -gnatw switch that affects the handling of style check messages.
5207 @emph{Activate every optional warning}
5208 @cindex @option{-gnatw.e} (@command{gcc})
5209 @cindex Warnings, activate every optional warning
5210 This switch activates all optional warnings, including those which
5211 are not activated by @code{-gnatwa}.
5214 @emph{Activate warnings on unreferenced formals.}
5215 @cindex @option{-gnatwf} (@command{gcc})
5216 @cindex Formals, unreferenced
5217 This switch causes a warning to be generated if a formal parameter
5218 is not referenced in the body of the subprogram. This warning can
5219 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5220 default is that these warnings are not generated.
5223 @emph{Suppress warnings on unreferenced formals.}
5224 @cindex @option{-gnatwF} (@command{gcc})
5225 This switch suppresses warnings for unreferenced formal
5226 parameters. Note that the
5227 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5228 effect of warning on unreferenced entities other than subprogram
5232 @emph{Activate warnings on unrecognized pragmas.}
5233 @cindex @option{-gnatwg} (@command{gcc})
5234 @cindex Pragmas, unrecognized
5235 This switch causes a warning to be generated if an unrecognized
5236 pragma is encountered. Apart from issuing this warning, the
5237 pragma is ignored and has no effect. This warning can
5238 also be turned on using @option{-gnatwa}. The default
5239 is that such warnings are issued (satisfying the Ada Reference
5240 Manual requirement that such warnings appear).
5243 @emph{Suppress warnings on unrecognized pragmas.}
5244 @cindex @option{-gnatwG} (@command{gcc})
5245 This switch suppresses warnings for unrecognized pragmas.
5248 @emph{Activate warnings on hiding.}
5249 @cindex @option{-gnatwh} (@command{gcc})
5250 @cindex Hiding of Declarations
5251 This switch activates warnings on hiding declarations.
5252 A declaration is considered hiding
5253 if it is for a non-overloadable entity, and it declares an entity with the
5254 same name as some other entity that is directly or use-visible. The default
5255 is that such warnings are not generated.
5256 Note that @option{-gnatwa} does not affect the setting of this warning option.
5259 @emph{Suppress warnings on hiding.}
5260 @cindex @option{-gnatwH} (@command{gcc})
5261 This switch suppresses warnings on hiding declarations.
5264 @emph{Activate warnings on implementation units.}
5265 @cindex @option{-gnatwi} (@command{gcc})
5266 This switch activates warnings for a @code{with} of an internal GNAT
5267 implementation unit, defined as any unit from the @code{Ada},
5268 @code{Interfaces}, @code{GNAT},
5269 ^^@code{DEC},^ or @code{System}
5270 hierarchies that is not
5271 documented in either the Ada Reference Manual or the GNAT
5272 Programmer's Reference Manual. Such units are intended only
5273 for internal implementation purposes and should not be @code{with}'ed
5274 by user programs. The default is that such warnings are generated
5275 This warning can also be turned on using @option{-gnatwa}.
5278 @emph{Disable warnings on implementation units.}
5279 @cindex @option{-gnatwI} (@command{gcc})
5280 This switch disables warnings for a @code{with} of an internal GNAT
5281 implementation unit.
5284 @emph{Activate warnings on overlapping actuals.}
5285 @cindex @option{-gnatw.i} (@command{gcc})
5286 This switch enables a warning on statically detectable overlapping actuals in
5287 a subprogram call, when one of the actuals is an in-out parameter, and the
5288 types of the actuals are not by-copy types. The warning is off by default,
5289 and is not included under -gnatwa.
5292 @emph{Disable warnings on overlapping actuals.}
5293 @cindex @option{-gnatw.I} (@command{gcc})
5294 This switch disables warnings on overlapping actuals in a call..
5297 @emph{Activate warnings on obsolescent features (Annex J).}
5298 @cindex @option{-gnatwj} (@command{gcc})
5299 @cindex Features, obsolescent
5300 @cindex Obsolescent features
5301 If this warning option is activated, then warnings are generated for
5302 calls to subprograms marked with @code{pragma Obsolescent} and
5303 for use of features in Annex J of the Ada Reference Manual. In the
5304 case of Annex J, not all features are flagged. In particular use
5305 of the renamed packages (like @code{Text_IO}) and use of package
5306 @code{ASCII} are not flagged, since these are very common and
5307 would generate many annoying positive warnings. The default is that
5308 such warnings are not generated. This warning is also turned on by
5309 the use of @option{-gnatwa}.
5311 In addition to the above cases, warnings are also generated for
5312 GNAT features that have been provided in past versions but which
5313 have been superseded (typically by features in the new Ada standard).
5314 For example, @code{pragma Ravenscar} will be flagged since its
5315 function is replaced by @code{pragma Profile(Ravenscar)}.
5317 Note that this warning option functions differently from the
5318 restriction @code{No_Obsolescent_Features} in two respects.
5319 First, the restriction applies only to annex J features.
5320 Second, the restriction does flag uses of package @code{ASCII}.
5323 @emph{Suppress warnings on obsolescent features (Annex J).}
5324 @cindex @option{-gnatwJ} (@command{gcc})
5325 This switch disables warnings on use of obsolescent features.
5328 @emph{Activate warnings on variables that could be constants.}
5329 @cindex @option{-gnatwk} (@command{gcc})
5330 This switch activates warnings for variables that are initialized but
5331 never modified, and then could be declared constants. The default is that
5332 such warnings are not given.
5333 This warning can also be turned on using @option{-gnatwa}.
5336 @emph{Suppress warnings on variables that could be constants.}
5337 @cindex @option{-gnatwK} (@command{gcc})
5338 This switch disables warnings on variables that could be declared constants.
5341 @emph{Activate warnings for elaboration pragmas.}
5342 @cindex @option{-gnatwl} (@command{gcc})
5343 @cindex Elaboration, warnings
5344 This switch activates warnings on missing
5345 @code{Elaborate_All} and @code{Elaborate} pragmas.
5346 See the section in this guide on elaboration checking for details on
5347 when such pragmas should be used. In dynamic elaboration mode, this switch
5348 generations warnings about the need to add elaboration pragmas. Note however,
5349 that if you blindly follow these warnings, and add @code{Elaborate_All}
5350 warnings wherever they are recommended, you basically end up with the
5351 equivalent of the static elaboration model, which may not be what you want for
5352 legacy code for which the static model does not work.
5354 For the static model, the messages generated are labeled "info:" (for
5355 information messages). They are not warnings to add elaboration pragmas,
5356 merely informational messages showing what implicit elaboration pragmas
5357 have been added, for use in analyzing elaboration circularity problems.
5359 Warnings are also generated if you
5360 are using the static mode of elaboration, and a @code{pragma Elaborate}
5361 is encountered. The default is that such warnings
5363 This warning is not automatically turned on by the use of @option{-gnatwa}.
5366 @emph{Suppress warnings for elaboration pragmas.}
5367 @cindex @option{-gnatwL} (@command{gcc})
5368 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5369 See the section in this guide on elaboration checking for details on
5370 when such pragmas should be used.
5373 @emph{Activate warnings on modified but unreferenced variables.}
5374 @cindex @option{-gnatwm} (@command{gcc})
5375 This switch activates warnings for variables that are assigned (using
5376 an initialization value or with one or more assignment statements) but
5377 whose value is never read. The warning is suppressed for volatile
5378 variables and also for variables that are renamings of other variables
5379 or for which an address clause is given.
5380 This warning can also be turned on using @option{-gnatwa}.
5381 The default is that these warnings are not given.
5384 @emph{Disable warnings on modified but unreferenced variables.}
5385 @cindex @option{-gnatwM} (@command{gcc})
5386 This switch disables warnings for variables that are assigned or
5387 initialized, but never read.
5390 @emph{Activate warnings on suspicious modulus values.}
5391 @cindex @option{-gnatw.m} (@command{gcc})
5392 This switch activates warnings for modulus values that seem suspicious.
5393 The cases caught are where the size is the same as the modulus (e.g.
5394 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5395 with no size clause. The guess in both cases is that 2**x was intended
5396 rather than x. The default is that these warnings are given.
5399 @emph{Disable warnings on suspicious modulus values.}
5400 @cindex @option{-gnatw.M} (@command{gcc})
5401 This switch disables warnings for suspicious modulus values.
5404 @emph{Set normal warnings mode.}
5405 @cindex @option{-gnatwn} (@command{gcc})
5406 This switch sets normal warning mode, in which enabled warnings are
5407 issued and treated as warnings rather than errors. This is the default
5408 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5409 an explicit @option{-gnatws} or
5410 @option{-gnatwe}. It also cancels the effect of the
5411 implicit @option{-gnatwe} that is activated by the
5412 use of @option{-gnatg}.
5415 @emph{Activate warnings on address clause overlays.}
5416 @cindex @option{-gnatwo} (@command{gcc})
5417 @cindex Address Clauses, warnings
5418 This switch activates warnings for possibly unintended initialization
5419 effects of defining address clauses that cause one variable to overlap
5420 another. The default is that such warnings are generated.
5421 This warning can also be turned on using @option{-gnatwa}.
5424 @emph{Suppress warnings on address clause overlays.}
5425 @cindex @option{-gnatwO} (@command{gcc})
5426 This switch suppresses warnings on possibly unintended initialization
5427 effects of defining address clauses that cause one variable to overlap
5431 @emph{Activate warnings on modified but unreferenced out parameters.}
5432 @cindex @option{-gnatw.o} (@command{gcc})
5433 This switch activates warnings for variables that are modified by using
5434 them as actuals for a call to a procedure with an out mode formal, where
5435 the resulting assigned value is never read. It is applicable in the case
5436 where there is more than one out mode formal. If there is only one out
5437 mode formal, the warning is issued by default (controlled by -gnatwu).
5438 The warning is suppressed for volatile
5439 variables and also for variables that are renamings of other variables
5440 or for which an address clause is given.
5441 The default is that these warnings are not given. Note that this warning
5442 is not included in -gnatwa, it must be activated explicitly.
5445 @emph{Disable warnings on modified but unreferenced out parameters.}
5446 @cindex @option{-gnatw.O} (@command{gcc})
5447 This switch suppresses warnings for variables that are modified by using
5448 them as actuals for a call to a procedure with an out mode formal, where
5449 the resulting assigned value is never read.
5452 @emph{Activate warnings on ineffective pragma Inlines.}
5453 @cindex @option{-gnatwp} (@command{gcc})
5454 @cindex Inlining, warnings
5455 This switch activates warnings for failure of front end inlining
5456 (activated by @option{-gnatN}) to inline a particular call. There are
5457 many reasons for not being able to inline a call, including most
5458 commonly that the call is too complex to inline. The default is
5459 that such warnings are not given.
5460 This warning can also be turned on using @option{-gnatwa}.
5461 Warnings on ineffective inlining by the gcc back-end can be activated
5462 separately, using the gcc switch -Winline.
5465 @emph{Suppress warnings on ineffective pragma Inlines.}
5466 @cindex @option{-gnatwP} (@command{gcc})
5467 This switch suppresses warnings on ineffective pragma Inlines. If the
5468 inlining mechanism cannot inline a call, it will simply ignore the
5472 @emph{Activate warnings on parameter ordering.}
5473 @cindex @option{-gnatw.p} (@command{gcc})
5474 @cindex Parameter order, warnings
5475 This switch activates warnings for cases of suspicious parameter
5476 ordering when the list of arguments are all simple identifiers that
5477 match the names of the formals, but are in a different order. The
5478 warning is suppressed if any use of named parameter notation is used,
5479 so this is the appropriate way to suppress a false positive (and
5480 serves to emphasize that the "misordering" is deliberate). The
5482 that such warnings are not given.
5483 This warning can also be turned on using @option{-gnatwa}.
5486 @emph{Suppress warnings on parameter ordering.}
5487 @cindex @option{-gnatw.P} (@command{gcc})
5488 This switch suppresses warnings on cases of suspicious parameter
5492 @emph{Activate warnings on questionable missing parentheses.}
5493 @cindex @option{-gnatwq} (@command{gcc})
5494 @cindex Parentheses, warnings
5495 This switch activates warnings for cases where parentheses are not used and
5496 the result is potential ambiguity from a readers point of view. For example
5497 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5498 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5499 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5500 follow the rule of always parenthesizing to make the association clear, and
5501 this warning switch warns if such parentheses are not present. The default
5502 is that these warnings are given.
5503 This warning can also be turned on using @option{-gnatwa}.
5506 @emph{Suppress warnings on questionable missing parentheses.}
5507 @cindex @option{-gnatwQ} (@command{gcc})
5508 This switch suppresses warnings for cases where the association is not
5509 clear and the use of parentheses is preferred.
5512 @emph{Activate warnings on redundant constructs.}
5513 @cindex @option{-gnatwr} (@command{gcc})
5514 This switch activates warnings for redundant constructs. The following
5515 is the current list of constructs regarded as redundant:
5519 Assignment of an item to itself.
5521 Type conversion that converts an expression to its own type.
5523 Use of the attribute @code{Base} where @code{typ'Base} is the same
5526 Use of pragma @code{Pack} when all components are placed by a record
5527 representation clause.
5529 Exception handler containing only a reraise statement (raise with no
5530 operand) which has no effect.
5532 Use of the operator abs on an operand that is known at compile time
5535 Comparison of boolean expressions to an explicit True value.
5538 This warning can also be turned on using @option{-gnatwa}.
5539 The default is that warnings for redundant constructs are not given.
5542 @emph{Suppress warnings on redundant constructs.}
5543 @cindex @option{-gnatwR} (@command{gcc})
5544 This switch suppresses warnings for redundant constructs.
5547 @emph{Activate warnings for object renaming function.}
5548 @cindex @option{-gnatw.r} (@command{gcc})
5549 This switch activates warnings for an object renaming that renames a
5550 function call, which is equivalent to a constant declaration (as
5551 opposed to renaming the function itself). The default is that these
5552 warnings are given. This warning can also be turned on using
5556 @emph{Suppress warnings for object renaming function.}
5557 @cindex @option{-gnatwT} (@command{gcc})
5558 This switch suppresses warnings for object renaming function.
5561 @emph{Suppress all warnings.}
5562 @cindex @option{-gnatws} (@command{gcc})
5563 This switch completely suppresses the
5564 output of all warning messages from the GNAT front end.
5565 Note that it does not suppress warnings from the @command{gcc} back end.
5566 To suppress these back end warnings as well, use the switch @option{-w}
5567 in addition to @option{-gnatws}. Also this switch has no effect on the
5568 handling of style check messages.
5571 @emph{Activate warnings for tracking of deleted conditional code.}
5572 @cindex @option{-gnatwt} (@command{gcc})
5573 @cindex Deactivated code, warnings
5574 @cindex Deleted code, warnings
5575 This switch activates warnings for tracking of code in conditionals (IF and
5576 CASE statements) that is detected to be dead code which cannot be executed, and
5577 which is removed by the front end. This warning is off by default, and is not
5578 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5579 useful for detecting deactivated code in certified applications.
5582 @emph{Suppress warnings for tracking of deleted conditional code.}
5583 @cindex @option{-gnatwT} (@command{gcc})
5584 This switch suppresses warnings for tracking of deleted conditional code.
5587 @emph{Activate warnings on unused entities.}
5588 @cindex @option{-gnatwu} (@command{gcc})
5589 This switch activates warnings to be generated for entities that
5590 are declared but not referenced, and for units that are @code{with}'ed
5592 referenced. In the case of packages, a warning is also generated if
5593 no entities in the package are referenced. This means that if the package
5594 is referenced but the only references are in @code{use}
5595 clauses or @code{renames}
5596 declarations, a warning is still generated. A warning is also generated
5597 for a generic package that is @code{with}'ed but never instantiated.
5598 In the case where a package or subprogram body is compiled, and there
5599 is a @code{with} on the corresponding spec
5600 that is only referenced in the body,
5601 a warning is also generated, noting that the
5602 @code{with} can be moved to the body. The default is that
5603 such warnings are not generated.
5604 This switch also activates warnings on unreferenced formals
5605 (it includes the effect of @option{-gnatwf}).
5606 This warning can also be turned on using @option{-gnatwa}.
5609 @emph{Suppress warnings on unused entities.}
5610 @cindex @option{-gnatwU} (@command{gcc})
5611 This switch suppresses warnings for unused entities and packages.
5612 It also turns off warnings on unreferenced formals (and thus includes
5613 the effect of @option{-gnatwF}).
5616 @emph{Activate warnings on unassigned variables.}
5617 @cindex @option{-gnatwv} (@command{gcc})
5618 @cindex Unassigned variable warnings
5619 This switch activates warnings for access to variables which
5620 may not be properly initialized. The default is that
5621 such warnings are generated.
5622 This warning can also be turned on using @option{-gnatwa}.
5625 @emph{Suppress warnings on unassigned variables.}
5626 @cindex @option{-gnatwV} (@command{gcc})
5627 This switch suppresses warnings for access to variables which
5628 may not be properly initialized.
5629 For variables of a composite type, the warning can also be suppressed in
5630 Ada 2005 by using a default initialization with a box. For example, if
5631 Table is an array of records whose components are only partially uninitialized,
5632 then the following code:
5634 @smallexample @c ada
5635 Tab : Table := (others => <>);
5638 will suppress warnings on subsequent statements that access components
5642 @emph{Activate warnings on wrong low bound assumption.}
5643 @cindex @option{-gnatww} (@command{gcc})
5644 @cindex String indexing warnings
5645 This switch activates warnings for indexing an unconstrained string parameter
5646 with a literal or S'Length. This is a case where the code is assuming that the
5647 low bound is one, which is in general not true (for example when a slice is
5648 passed). The default is that such warnings are generated.
5649 This warning can also be turned on using @option{-gnatwa}.
5652 @emph{Suppress warnings on wrong low bound assumption.}
5653 @cindex @option{-gnatwW} (@command{gcc})
5654 This switch suppresses warnings for indexing an unconstrained string parameter
5655 with a literal or S'Length. Note that this warning can also be suppressed
5656 in a particular case by adding an
5657 assertion that the lower bound is 1,
5658 as shown in the following example.
5660 @smallexample @c ada
5661 procedure K (S : String) is
5662 pragma Assert (S'First = 1);
5667 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5668 @cindex @option{-gnatw.w} (@command{gcc})
5669 @cindex Warnings Off control
5670 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5671 where either the pragma is entirely useless (because it suppresses no
5672 warnings), or it could be replaced by @code{pragma Unreferenced} or
5673 @code{pragma Unmodified}.The default is that these warnings are not given.
5674 Note that this warning is not included in -gnatwa, it must be
5675 activated explicitly.
5678 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5679 @cindex @option{-gnatw.W} (@command{gcc})
5680 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5683 @emph{Activate warnings on Export/Import pragmas.}
5684 @cindex @option{-gnatwx} (@command{gcc})
5685 @cindex Export/Import pragma warnings
5686 This switch activates warnings on Export/Import pragmas when
5687 the compiler detects a possible conflict between the Ada and
5688 foreign language calling sequences. For example, the use of
5689 default parameters in a convention C procedure is dubious
5690 because the C compiler cannot supply the proper default, so
5691 a warning is issued. The default is that such warnings are
5693 This warning can also be turned on using @option{-gnatwa}.
5696 @emph{Suppress warnings on Export/Import pragmas.}
5697 @cindex @option{-gnatwX} (@command{gcc})
5698 This switch suppresses warnings on Export/Import pragmas.
5699 The sense of this is that you are telling the compiler that
5700 you know what you are doing in writing the pragma, and it
5701 should not complain at you.
5704 @emph{Activate warnings for No_Exception_Propagation mode.}
5705 @cindex @option{-gnatwm} (@command{gcc})
5706 This switch activates warnings for exception usage when pragma Restrictions
5707 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5708 explicit exception raises which are not covered by a local handler, and for
5709 exception handlers which do not cover a local raise. The default is that these
5710 warnings are not given.
5713 @emph{Disable warnings for No_Exception_Propagation mode.}
5714 This switch disables warnings for exception usage when pragma Restrictions
5715 (No_Exception_Propagation) is in effect.
5718 @emph{Activate warnings for Ada 2005 compatibility issues.}
5719 @cindex @option{-gnatwy} (@command{gcc})
5720 @cindex Ada 2005 compatibility issues warnings
5721 For the most part Ada 2005 is upwards compatible with Ada 95,
5722 but there are some exceptions (for example the fact that
5723 @code{interface} is now a reserved word in Ada 2005). This
5724 switch activates several warnings to help in identifying
5725 and correcting such incompatibilities. The default is that
5726 these warnings are generated. Note that at one point Ada 2005
5727 was called Ada 0Y, hence the choice of character.
5728 This warning can also be turned on using @option{-gnatwa}.
5731 @emph{Disable warnings for Ada 2005 compatibility issues.}
5732 @cindex @option{-gnatwY} (@command{gcc})
5733 @cindex Ada 2005 compatibility issues warnings
5734 This switch suppresses several warnings intended to help in identifying
5735 incompatibilities between Ada 95 and Ada 2005.
5738 @emph{Activate warnings on unchecked conversions.}
5739 @cindex @option{-gnatwz} (@command{gcc})
5740 @cindex Unchecked_Conversion warnings
5741 This switch activates warnings for unchecked conversions
5742 where the types are known at compile time to have different
5744 is that such warnings are generated. Warnings are also
5745 generated for subprogram pointers with different conventions,
5746 and, on VMS only, for data pointers with different conventions.
5747 This warning can also be turned on using @option{-gnatwa}.
5750 @emph{Suppress warnings on unchecked conversions.}
5751 @cindex @option{-gnatwZ} (@command{gcc})
5752 This switch suppresses warnings for unchecked conversions
5753 where the types are known at compile time to have different
5754 sizes or conventions.
5756 @item ^-Wunused^WARNINGS=UNUSED^
5757 @cindex @option{-Wunused}
5758 The warnings controlled by the @option{-gnatw} switch are generated by
5759 the front end of the compiler. The @option{GCC} back end can provide
5760 additional warnings and they are controlled by the @option{-W} switch.
5761 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5762 warnings for entities that are declared but not referenced.
5764 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5765 @cindex @option{-Wuninitialized}
5766 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5767 the back end warning for uninitialized variables. This switch must be
5768 used in conjunction with an optimization level greater than zero.
5770 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5771 @cindex @option{-Wall}
5772 This switch enables all the above warnings from the @option{GCC} back end.
5773 The code generator detects a number of warning situations that are missed
5774 by the @option{GNAT} front end, and this switch can be used to activate them.
5775 The use of this switch also sets the default front end warning mode to
5776 @option{-gnatwa}, that is, most front end warnings activated as well.
5778 @item ^-w^/NO_BACK_END_WARNINGS^
5780 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5781 The use of this switch also sets the default front end warning mode to
5782 @option{-gnatws}, that is, front end warnings suppressed as well.
5788 A string of warning parameters can be used in the same parameter. For example:
5795 will turn on all optional warnings except for elaboration pragma warnings,
5796 and also specify that warnings should be treated as errors.
5798 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5823 @node Debugging and Assertion Control
5824 @subsection Debugging and Assertion Control
5828 @cindex @option{-gnata} (@command{gcc})
5834 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5835 are ignored. This switch, where @samp{a} stands for assert, causes
5836 @code{Assert} and @code{Debug} pragmas to be activated.
5838 The pragmas have the form:
5842 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5843 @var{static-string-expression}@r{]})
5844 @b{pragma} Debug (@var{procedure call})
5849 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5850 If the result is @code{True}, the pragma has no effect (other than
5851 possible side effects from evaluating the expression). If the result is
5852 @code{False}, the exception @code{Assert_Failure} declared in the package
5853 @code{System.Assertions} is
5854 raised (passing @var{static-string-expression}, if present, as the
5855 message associated with the exception). If no string expression is
5856 given the default is a string giving the file name and line number
5859 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5860 @code{pragma Debug} may appear within a declaration sequence, allowing
5861 debugging procedures to be called between declarations.
5864 @item /DEBUG@r{[}=debug-level@r{]}
5866 Specifies how much debugging information is to be included in
5867 the resulting object file where 'debug-level' is one of the following:
5870 Include both debugger symbol records and traceback
5872 This is the default setting.
5874 Include both debugger symbol records and traceback in
5877 Excludes both debugger symbol records and traceback
5878 the object file. Same as /NODEBUG.
5880 Includes only debugger symbol records in the object
5881 file. Note that this doesn't include traceback information.
5886 @node Validity Checking
5887 @subsection Validity Checking
5888 @findex Validity Checking
5891 The Ada Reference Manual defines the concept of invalid values (see
5892 RM 13.9.1). The primary source of invalid values is uninitialized
5893 variables. A scalar variable that is left uninitialized may contain
5894 an invalid value; the concept of invalid does not apply to access or
5897 It is an error to read an invalid value, but the RM does not require
5898 run-time checks to detect such errors, except for some minimal
5899 checking to prevent erroneous execution (i.e. unpredictable
5900 behavior). This corresponds to the @option{-gnatVd} switch below,
5901 which is the default. For example, by default, if the expression of a
5902 case statement is invalid, it will raise Constraint_Error rather than
5903 causing a wild jump, and if an array index on the left-hand side of an
5904 assignment is invalid, it will raise Constraint_Error rather than
5905 overwriting an arbitrary memory location.
5907 The @option{-gnatVa} may be used to enable additional validity checks,
5908 which are not required by the RM. These checks are often very
5909 expensive (which is why the RM does not require them). These checks
5910 are useful in tracking down uninitialized variables, but they are
5911 not usually recommended for production builds.
5913 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5914 control; you can enable whichever validity checks you desire. However,
5915 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5916 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5917 sufficient for non-debugging use.
5919 The @option{-gnatB} switch tells the compiler to assume that all
5920 values are valid (that is, within their declared subtype range)
5921 except in the context of a use of the Valid attribute. This means
5922 the compiler can generate more efficient code, since the range
5923 of values is better known at compile time. However, an uninitialized
5924 variable can cause wild jumps and memory corruption in this mode.
5926 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5927 checking mode as described below.
5929 The @code{x} argument is a string of letters that
5930 indicate validity checks that are performed or not performed in addition
5931 to the default checks required by Ada as described above.
5934 The options allowed for this qualifier
5935 indicate validity checks that are performed or not performed in addition
5936 to the default checks required by Ada as described above.
5942 @emph{All validity checks.}
5943 @cindex @option{-gnatVa} (@command{gcc})
5944 All validity checks are turned on.
5946 That is, @option{-gnatVa} is
5947 equivalent to @option{gnatVcdfimorst}.
5951 @emph{Validity checks for copies.}
5952 @cindex @option{-gnatVc} (@command{gcc})
5953 The right hand side of assignments, and the initializing values of
5954 object declarations are validity checked.
5957 @emph{Default (RM) validity checks.}
5958 @cindex @option{-gnatVd} (@command{gcc})
5959 Some validity checks are done by default following normal Ada semantics
5961 A check is done in case statements that the expression is within the range
5962 of the subtype. If it is not, Constraint_Error is raised.
5963 For assignments to array components, a check is done that the expression used
5964 as index is within the range. If it is not, Constraint_Error is raised.
5965 Both these validity checks may be turned off using switch @option{-gnatVD}.
5966 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5967 switch @option{-gnatVd} will leave the checks turned on.
5968 Switch @option{-gnatVD} should be used only if you are sure that all such
5969 expressions have valid values. If you use this switch and invalid values
5970 are present, then the program is erroneous, and wild jumps or memory
5971 overwriting may occur.
5974 @emph{Validity checks for elementary components.}
5975 @cindex @option{-gnatVe} (@command{gcc})
5976 In the absence of this switch, assignments to record or array components are
5977 not validity checked, even if validity checks for assignments generally
5978 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5979 require valid data, but assignment of individual components does. So for
5980 example, there is a difference between copying the elements of an array with a
5981 slice assignment, compared to assigning element by element in a loop. This
5982 switch allows you to turn off validity checking for components, even when they
5983 are assigned component by component.
5986 @emph{Validity checks for floating-point values.}
5987 @cindex @option{-gnatVf} (@command{gcc})
5988 In the absence of this switch, validity checking occurs only for discrete
5989 values. If @option{-gnatVf} is specified, then validity checking also applies
5990 for floating-point values, and NaNs and infinities are considered invalid,
5991 as well as out of range values for constrained types. Note that this means
5992 that standard IEEE infinity mode is not allowed. The exact contexts
5993 in which floating-point values are checked depends on the setting of other
5994 options. For example,
5995 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5996 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5997 (the order does not matter) specifies that floating-point parameters of mode
5998 @code{in} should be validity checked.
6001 @emph{Validity checks for @code{in} mode parameters}
6002 @cindex @option{-gnatVi} (@command{gcc})
6003 Arguments for parameters of mode @code{in} are validity checked in function
6004 and procedure calls at the point of call.
6007 @emph{Validity checks for @code{in out} mode parameters.}
6008 @cindex @option{-gnatVm} (@command{gcc})
6009 Arguments for parameters of mode @code{in out} are validity checked in
6010 procedure calls at the point of call. The @code{'m'} here stands for
6011 modify, since this concerns parameters that can be modified by the call.
6012 Note that there is no specific option to test @code{out} parameters,
6013 but any reference within the subprogram will be tested in the usual
6014 manner, and if an invalid value is copied back, any reference to it
6015 will be subject to validity checking.
6018 @emph{No validity checks.}
6019 @cindex @option{-gnatVn} (@command{gcc})
6020 This switch turns off all validity checking, including the default checking
6021 for case statements and left hand side subscripts. Note that the use of
6022 the switch @option{-gnatp} suppresses all run-time checks, including
6023 validity checks, and thus implies @option{-gnatVn}. When this switch
6024 is used, it cancels any other @option{-gnatV} previously issued.
6027 @emph{Validity checks for operator and attribute operands.}
6028 @cindex @option{-gnatVo} (@command{gcc})
6029 Arguments for predefined operators and attributes are validity checked.
6030 This includes all operators in package @code{Standard},
6031 the shift operators defined as intrinsic in package @code{Interfaces}
6032 and operands for attributes such as @code{Pos}. Checks are also made
6033 on individual component values for composite comparisons, and on the
6034 expressions in type conversions and qualified expressions. Checks are
6035 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6038 @emph{Validity checks for parameters.}
6039 @cindex @option{-gnatVp} (@command{gcc})
6040 This controls the treatment of parameters within a subprogram (as opposed
6041 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6042 of parameters on a call. If either of these call options is used, then
6043 normally an assumption is made within a subprogram that the input arguments
6044 have been validity checking at the point of call, and do not need checking
6045 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6046 is not made, and parameters are not assumed to be valid, so their validity
6047 will be checked (or rechecked) within the subprogram.
6050 @emph{Validity checks for function returns.}
6051 @cindex @option{-gnatVr} (@command{gcc})
6052 The expression in @code{return} statements in functions is validity
6056 @emph{Validity checks for subscripts.}
6057 @cindex @option{-gnatVs} (@command{gcc})
6058 All subscripts expressions are checked for validity, whether they appear
6059 on the right side or left side (in default mode only left side subscripts
6060 are validity checked).
6063 @emph{Validity checks for tests.}
6064 @cindex @option{-gnatVt} (@command{gcc})
6065 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6066 statements are checked, as well as guard expressions in entry calls.
6071 The @option{-gnatV} switch may be followed by
6072 ^a string of letters^a list of options^
6073 to turn on a series of validity checking options.
6075 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6076 specifies that in addition to the default validity checking, copies and
6077 function return expressions are to be validity checked.
6078 In order to make it easier
6079 to specify the desired combination of effects,
6081 the upper case letters @code{CDFIMORST} may
6082 be used to turn off the corresponding lower case option.
6085 the prefix @code{NO} on an option turns off the corresponding validity
6088 @item @code{NOCOPIES}
6089 @item @code{NODEFAULT}
6090 @item @code{NOFLOATS}
6091 @item @code{NOIN_PARAMS}
6092 @item @code{NOMOD_PARAMS}
6093 @item @code{NOOPERANDS}
6094 @item @code{NORETURNS}
6095 @item @code{NOSUBSCRIPTS}
6096 @item @code{NOTESTS}
6100 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6101 turns on all validity checking options except for
6102 checking of @code{@b{in out}} procedure arguments.
6104 The specification of additional validity checking generates extra code (and
6105 in the case of @option{-gnatVa} the code expansion can be substantial).
6106 However, these additional checks can be very useful in detecting
6107 uninitialized variables, incorrect use of unchecked conversion, and other
6108 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6109 is useful in conjunction with the extra validity checking, since this
6110 ensures that wherever possible uninitialized variables have invalid values.
6112 See also the pragma @code{Validity_Checks} which allows modification of
6113 the validity checking mode at the program source level, and also allows for
6114 temporary disabling of validity checks.
6116 @node Style Checking
6117 @subsection Style Checking
6118 @findex Style checking
6121 The @option{-gnaty^x^(option,option,@dots{})^} switch
6122 @cindex @option{-gnaty} (@command{gcc})
6123 causes the compiler to
6124 enforce specified style rules. A limited set of style rules has been used
6125 in writing the GNAT sources themselves. This switch allows user programs
6126 to activate all or some of these checks. If the source program fails a
6127 specified style check, an appropriate message is given, preceded by
6128 the character sequence ``(style)''. This message does not prevent
6129 successful compilation (unless the @option{-gnatwe} switch is used).
6132 @code{(option,option,@dots{})} is a sequence of keywords
6135 The string @var{x} is a sequence of letters or digits
6137 indicating the particular style
6138 checks to be performed. The following checks are defined:
6143 @emph{Specify indentation level.}
6144 If a digit from 1-9 appears
6145 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6146 then proper indentation is checked, with the digit indicating the
6147 indentation level required. A value of zero turns off this style check.
6148 The general style of required indentation is as specified by
6149 the examples in the Ada Reference Manual. Full line comments must be
6150 aligned with the @code{--} starting on a column that is a multiple of
6151 the alignment level, or they may be aligned the same way as the following
6152 non-blank line (this is useful when full line comments appear in the middle
6156 @emph{Check attribute casing.}
6157 Attribute names, including the case of keywords such as @code{digits}
6158 used as attributes names, must be written in mixed case, that is, the
6159 initial letter and any letter following an underscore must be uppercase.
6160 All other letters must be lowercase.
6162 @item ^A^ARRAY_INDEXES^
6163 @emph{Use of array index numbers in array attributes.}
6164 When using the array attributes First, Last, Range,
6165 or Length, the index number must be omitted for one-dimensional arrays
6166 and is required for multi-dimensional arrays.
6169 @emph{Blanks not allowed at statement end.}
6170 Trailing blanks are not allowed at the end of statements. The purpose of this
6171 rule, together with h (no horizontal tabs), is to enforce a canonical format
6172 for the use of blanks to separate source tokens.
6174 @item ^B^BOOLEAN_OPERATORS^
6175 @emph{Check Boolean operators.}
6176 The use of AND/OR operators is not permitted except in the cases of modular
6177 operands, array operands, and simple stand-alone boolean variables or
6178 boolean constants. In all other cases AND THEN/OR ELSE are required.
6181 @emph{Check comments.}
6182 Comments must meet the following set of rules:
6187 The ``@code{--}'' that starts the column must either start in column one,
6188 or else at least one blank must precede this sequence.
6191 Comments that follow other tokens on a line must have at least one blank
6192 following the ``@code{--}'' at the start of the comment.
6195 Full line comments must have two blanks following the ``@code{--}'' that
6196 starts the comment, with the following exceptions.
6199 A line consisting only of the ``@code{--}'' characters, possibly preceded
6200 by blanks is permitted.
6203 A comment starting with ``@code{--x}'' where @code{x} is a special character
6205 This allows proper processing of the output generated by specialized tools
6206 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6208 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6209 special character is defined as being in one of the ASCII ranges
6210 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6211 Note that this usage is not permitted
6212 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6215 A line consisting entirely of minus signs, possibly preceded by blanks, is
6216 permitted. This allows the construction of box comments where lines of minus
6217 signs are used to form the top and bottom of the box.
6220 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6221 least one blank follows the initial ``@code{--}''. Together with the preceding
6222 rule, this allows the construction of box comments, as shown in the following
6225 ---------------------------
6226 -- This is a box comment --
6227 -- with two text lines. --
6228 ---------------------------
6232 @item ^d^DOS_LINE_ENDINGS^
6233 @emph{Check no DOS line terminators present.}
6234 All lines must be terminated by a single ASCII.LF
6235 character (in particular the DOS line terminator sequence CR/LF is not
6239 @emph{Check end/exit labels.}
6240 Optional labels on @code{end} statements ending subprograms and on
6241 @code{exit} statements exiting named loops, are required to be present.
6244 @emph{No form feeds or vertical tabs.}
6245 Neither form feeds nor vertical tab characters are permitted
6249 @emph{GNAT style mode}
6250 The set of style check switches is set to match that used by the GNAT sources.
6251 This may be useful when developing code that is eventually intended to be
6252 incorporated into GNAT. For further details, see GNAT sources.
6255 @emph{No horizontal tabs.}
6256 Horizontal tab characters are not permitted in the source text.
6257 Together with the b (no blanks at end of line) check, this
6258 enforces a canonical form for the use of blanks to separate
6262 @emph{Check if-then layout.}
6263 The keyword @code{then} must appear either on the same
6264 line as corresponding @code{if}, or on a line on its own, lined
6265 up under the @code{if} with at least one non-blank line in between
6266 containing all or part of the condition to be tested.
6269 @emph{check mode IN keywords}
6270 Mode @code{in} (the default mode) is not
6271 allowed to be given explicitly. @code{in out} is fine,
6272 but not @code{in} on its own.
6275 @emph{Check keyword casing.}
6276 All keywords must be in lower case (with the exception of keywords
6277 such as @code{digits} used as attribute names to which this check
6281 @emph{Check layout.}
6282 Layout of statement and declaration constructs must follow the
6283 recommendations in the Ada Reference Manual, as indicated by the
6284 form of the syntax rules. For example an @code{else} keyword must
6285 be lined up with the corresponding @code{if} keyword.
6287 There are two respects in which the style rule enforced by this check
6288 option are more liberal than those in the Ada Reference Manual. First
6289 in the case of record declarations, it is permissible to put the
6290 @code{record} keyword on the same line as the @code{type} keyword, and
6291 then the @code{end} in @code{end record} must line up under @code{type}.
6292 This is also permitted when the type declaration is split on two lines.
6293 For example, any of the following three layouts is acceptable:
6295 @smallexample @c ada
6318 Second, in the case of a block statement, a permitted alternative
6319 is to put the block label on the same line as the @code{declare} or
6320 @code{begin} keyword, and then line the @code{end} keyword up under
6321 the block label. For example both the following are permitted:
6323 @smallexample @c ada
6341 The same alternative format is allowed for loops. For example, both of
6342 the following are permitted:
6344 @smallexample @c ada
6346 Clear : while J < 10 loop
6357 @item ^Lnnn^MAX_NESTING=nnn^
6358 @emph{Set maximum nesting level}
6359 The maximum level of nesting of constructs (including subprograms, loops,
6360 blocks, packages, and conditionals) may not exceed the given value
6361 @option{nnn}. A value of zero disconnects this style check.
6363 @item ^m^LINE_LENGTH^
6364 @emph{Check maximum line length.}
6365 The length of source lines must not exceed 79 characters, including
6366 any trailing blanks. The value of 79 allows convenient display on an
6367 80 character wide device or window, allowing for possible special
6368 treatment of 80 character lines. Note that this count is of
6369 characters in the source text. This means that a tab character counts
6370 as one character in this count but a wide character sequence counts as
6371 a single character (however many bytes are needed in the encoding).
6373 @item ^Mnnn^MAX_LENGTH=nnn^
6374 @emph{Set maximum line length.}
6375 The length of lines must not exceed the
6376 given value @option{nnn}. The maximum value that can be specified is 32767.
6378 @item ^n^STANDARD_CASING^
6379 @emph{Check casing of entities in Standard.}
6380 Any identifier from Standard must be cased
6381 to match the presentation in the Ada Reference Manual (for example,
6382 @code{Integer} and @code{ASCII.NUL}).
6385 @emph{Turn off all style checks}
6386 All style check options are turned off.
6388 @item ^o^ORDERED_SUBPROGRAMS^
6389 @emph{Check order of subprogram bodies.}
6390 All subprogram bodies in a given scope
6391 (e.g.@: a package body) must be in alphabetical order. The ordering
6392 rule uses normal Ada rules for comparing strings, ignoring casing
6393 of letters, except that if there is a trailing numeric suffix, then
6394 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6397 @item ^O^OVERRIDING_INDICATORS^
6398 @emph{Check that overriding subprograms are explicitly marked as such.}
6399 The declaration of a primitive operation of a type extension that overrides
6400 an inherited operation must carry an overriding indicator.
6403 @emph{Check pragma casing.}
6404 Pragma names must be written in mixed case, that is, the
6405 initial letter and any letter following an underscore must be uppercase.
6406 All other letters must be lowercase.
6408 @item ^r^REFERENCES^
6409 @emph{Check references.}
6410 All identifier references must be cased in the same way as the
6411 corresponding declaration. No specific casing style is imposed on
6412 identifiers. The only requirement is for consistency of references
6415 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6416 @emph{Check no statements after THEN/ELSE.}
6417 No statements are allowed
6418 on the same line as a THEN or ELSE keyword following the
6419 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6420 and a special exception allows a pragma to appear after ELSE.
6423 @emph{Check separate specs.}
6424 Separate declarations (``specs'') are required for subprograms (a
6425 body is not allowed to serve as its own declaration). The only
6426 exception is that parameterless library level procedures are
6427 not required to have a separate declaration. This exception covers
6428 the most frequent form of main program procedures.
6431 @emph{Check token spacing.}
6432 The following token spacing rules are enforced:
6437 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6440 The token @code{=>} must be surrounded by spaces.
6443 The token @code{<>} must be preceded by a space or a left parenthesis.
6446 Binary operators other than @code{**} must be surrounded by spaces.
6447 There is no restriction on the layout of the @code{**} binary operator.
6450 Colon must be surrounded by spaces.
6453 Colon-equal (assignment, initialization) must be surrounded by spaces.
6456 Comma must be the first non-blank character on the line, or be
6457 immediately preceded by a non-blank character, and must be followed
6461 If the token preceding a left parenthesis ends with a letter or digit, then
6462 a space must separate the two tokens.
6465 if the token following a right parenthesis starts with a letter or digit, then
6466 a space must separate the two tokens.
6469 A right parenthesis must either be the first non-blank character on
6470 a line, or it must be preceded by a non-blank character.
6473 A semicolon must not be preceded by a space, and must not be followed by
6474 a non-blank character.
6477 A unary plus or minus may not be followed by a space.
6480 A vertical bar must be surrounded by spaces.
6483 @item ^u^UNNECESSARY_BLANK_LINES^
6484 @emph{Check unnecessary blank lines.}
6485 Unnecessary blank lines are not allowed. A blank line is considered
6486 unnecessary if it appears at the end of the file, or if more than
6487 one blank line occurs in sequence.
6489 @item ^x^XTRA_PARENS^
6490 @emph{Check extra parentheses.}
6491 Unnecessary extra level of parentheses (C-style) are not allowed
6492 around conditions in @code{if} statements, @code{while} statements and
6493 @code{exit} statements.
6495 @item ^y^ALL_BUILTIN^
6496 @emph{Set all standard style check options}
6497 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6498 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6499 @option{-gnatyS}, @option{-gnatyLnnn},
6500 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6504 @emph{Remove style check options}
6505 This causes any subsequent options in the string to act as canceling the
6506 corresponding style check option. To cancel maximum nesting level control,
6507 use @option{L} parameter witout any integer value after that, because any
6508 digit following @option{-} in the parameter string of the @option{-gnaty}
6509 option will be threated as canceling indentation check. The same is true
6510 for @option{M} parameter. @option{y} and @option{N} parameters are not
6511 allowed after @option{-}.
6514 This causes any subsequent options in the string to enable the corresponding
6515 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6521 @emph{Removing style check options}
6522 If the name of a style check is preceded by @option{NO} then the corresponding
6523 style check is turned off. For example @option{NOCOMMENTS} turns off style
6524 checking for comments.
6529 In the above rules, appearing in column one is always permitted, that is,
6530 counts as meeting either a requirement for a required preceding space,
6531 or as meeting a requirement for no preceding space.
6533 Appearing at the end of a line is also always permitted, that is, counts
6534 as meeting either a requirement for a following space, or as meeting
6535 a requirement for no following space.
6538 If any of these style rules is violated, a message is generated giving
6539 details on the violation. The initial characters of such messages are
6540 always ``@code{(style)}''. Note that these messages are treated as warning
6541 messages, so they normally do not prevent the generation of an object
6542 file. The @option{-gnatwe} switch can be used to treat warning messages,
6543 including style messages, as fatal errors.
6547 @option{-gnaty} on its own (that is not
6548 followed by any letters or digits), then the effect is equivalent
6549 to the use of @option{-gnatyy}, as described above, that is all
6550 built-in standard style check options are enabled.
6554 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6555 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6556 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6566 clears any previously set style checks.
6568 @node Run-Time Checks
6569 @subsection Run-Time Checks
6570 @cindex Division by zero
6571 @cindex Access before elaboration
6572 @cindex Checks, division by zero
6573 @cindex Checks, access before elaboration
6574 @cindex Checks, stack overflow checking
6577 By default, the following checks are suppressed: integer overflow
6578 checks, stack overflow checks, and checks for access before
6579 elaboration on subprogram calls. All other checks, including range
6580 checks and array bounds checks, are turned on by default. The
6581 following @command{gcc} switches refine this default behavior.
6586 @cindex @option{-gnatp} (@command{gcc})
6587 @cindex Suppressing checks
6588 @cindex Checks, suppressing
6590 This switch causes the unit to be compiled
6591 as though @code{pragma Suppress (All_checks)}
6592 had been present in the source. Validity checks are also eliminated (in
6593 other words @option{-gnatp} also implies @option{-gnatVn}.
6594 Use this switch to improve the performance
6595 of the code at the expense of safety in the presence of invalid data or
6598 Note that when checks are suppressed, the compiler is allowed, but not
6599 required, to omit the checking code. If the run-time cost of the
6600 checking code is zero or near-zero, the compiler will generate it even
6601 if checks are suppressed. In particular, if the compiler can prove
6602 that a certain check will necessarily fail, it will generate code to
6603 do an unconditional ``raise'', even if checks are suppressed. The
6604 compiler warns in this case. Another case in which checks may not be
6605 eliminated is when they are embedded in certain run time routines such
6606 as math library routines.
6608 Of course, run-time checks are omitted whenever the compiler can prove
6609 that they will not fail, whether or not checks are suppressed.
6611 Note that if you suppress a check that would have failed, program
6612 execution is erroneous, which means the behavior is totally
6613 unpredictable. The program might crash, or print wrong answers, or
6614 do anything else. It might even do exactly what you wanted it to do
6615 (and then it might start failing mysteriously next week or next
6616 year). The compiler will generate code based on the assumption that
6617 the condition being checked is true, which can result in disaster if
6618 that assumption is wrong.
6620 The @option{-gnatp} switch has no effect if a subsequent
6621 @option{-gnat-p} switch appears.
6624 @cindex @option{-gnat-p} (@command{gcc})
6625 @cindex Suppressing checks
6626 @cindex Checks, suppressing
6628 This switch cancels the effect of a previous @option{gnatp} switch.
6631 @cindex @option{-gnato} (@command{gcc})
6632 @cindex Overflow checks
6633 @cindex Check, overflow
6634 Enables overflow checking for integer operations.
6635 This causes GNAT to generate slower and larger executable
6636 programs by adding code to check for overflow (resulting in raising
6637 @code{Constraint_Error} as required by standard Ada
6638 semantics). These overflow checks correspond to situations in which
6639 the true value of the result of an operation may be outside the base
6640 range of the result type. The following example shows the distinction:
6642 @smallexample @c ada
6643 X1 : Integer := "Integer'Last";
6644 X2 : Integer range 1 .. 5 := "5";
6645 X3 : Integer := "Integer'Last";
6646 X4 : Integer range 1 .. 5 := "5";
6647 F : Float := "2.0E+20";
6656 Note that if explicit values are assigned at compile time, the
6657 compiler may be able to detect overflow at compile time, in which case
6658 no actual run-time checking code is required, and Constraint_Error
6659 will be raised unconditionally, with or without
6660 @option{-gnato}. That's why the assigned values in the above fragment
6661 are in quotes, the meaning is "assign a value not known to the
6662 compiler that happens to be equal to ...". The remaining discussion
6663 assumes that the compiler cannot detect the values at compile time.
6665 Here the first addition results in a value that is outside the base range
6666 of Integer, and hence requires an overflow check for detection of the
6667 constraint error. Thus the first assignment to @code{X1} raises a
6668 @code{Constraint_Error} exception only if @option{-gnato} is set.
6670 The second increment operation results in a violation of the explicit
6671 range constraint; such range checks are performed by default, and are
6672 unaffected by @option{-gnato}.
6674 The two conversions of @code{F} both result in values that are outside
6675 the base range of type @code{Integer} and thus will raise
6676 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6677 The fact that the result of the second conversion is assigned to
6678 variable @code{X4} with a restricted range is irrelevant, since the problem
6679 is in the conversion, not the assignment.
6681 Basically the rule is that in the default mode (@option{-gnato} not
6682 used), the generated code assures that all integer variables stay
6683 within their declared ranges, or within the base range if there is
6684 no declared range. This prevents any serious problems like indexes
6685 out of range for array operations.
6687 What is not checked in default mode is an overflow that results in
6688 an in-range, but incorrect value. In the above example, the assignments
6689 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6690 range of the target variable, but the result is wrong in the sense that
6691 it is too large to be represented correctly. Typically the assignment
6692 to @code{X1} will result in wrap around to the largest negative number.
6693 The conversions of @code{F} will result in some @code{Integer} value
6694 and if that integer value is out of the @code{X4} range then the
6695 subsequent assignment would generate an exception.
6697 @findex Machine_Overflows
6698 Note that the @option{-gnato} switch does not affect the code generated
6699 for any floating-point operations; it applies only to integer
6701 For floating-point, GNAT has the @code{Machine_Overflows}
6702 attribute set to @code{False} and the normal mode of operation is to
6703 generate IEEE NaN and infinite values on overflow or invalid operations
6704 (such as dividing 0.0 by 0.0).
6706 The reason that we distinguish overflow checking from other kinds of
6707 range constraint checking is that a failure of an overflow check, unlike
6708 for example the failure of a range check, can result in an incorrect
6709 value, but cannot cause random memory destruction (like an out of range
6710 subscript), or a wild jump (from an out of range case value). Overflow
6711 checking is also quite expensive in time and space, since in general it
6712 requires the use of double length arithmetic.
6714 Note again that @option{-gnato} is off by default, so overflow checking is
6715 not performed in default mode. This means that out of the box, with the
6716 default settings, GNAT does not do all the checks expected from the
6717 language description in the Ada Reference Manual. If you want all constraint
6718 checks to be performed, as described in this Manual, then you must
6719 explicitly use the -gnato switch either on the @command{gnatmake} or
6720 @command{gcc} command.
6723 @cindex @option{-gnatE} (@command{gcc})
6724 @cindex Elaboration checks
6725 @cindex Check, elaboration
6726 Enables dynamic checks for access-before-elaboration
6727 on subprogram calls and generic instantiations.
6728 Note that @option{-gnatE} is not necessary for safety, because in the
6729 default mode, GNAT ensures statically that the checks would not fail.
6730 For full details of the effect and use of this switch,
6731 @xref{Compiling Using gcc}.
6734 @cindex @option{-fstack-check} (@command{gcc})
6735 @cindex Stack Overflow Checking
6736 @cindex Checks, stack overflow checking
6737 Activates stack overflow checking. For full details of the effect and use of
6738 this switch see @ref{Stack Overflow Checking}.
6743 The setting of these switches only controls the default setting of the
6744 checks. You may modify them using either @code{Suppress} (to remove
6745 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6748 @node Using gcc for Syntax Checking
6749 @subsection Using @command{gcc} for Syntax Checking
6752 @cindex @option{-gnats} (@command{gcc})
6756 The @code{s} stands for ``syntax''.
6759 Run GNAT in syntax checking only mode. For
6760 example, the command
6763 $ gcc -c -gnats x.adb
6767 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6768 series of files in a single command
6770 , and can use wild cards to specify such a group of files.
6771 Note that you must specify the @option{-c} (compile
6772 only) flag in addition to the @option{-gnats} flag.
6775 You may use other switches in conjunction with @option{-gnats}. In
6776 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6777 format of any generated error messages.
6779 When the source file is empty or contains only empty lines and/or comments,
6780 the output is a warning:
6783 $ gcc -c -gnats -x ada toto.txt
6784 toto.txt:1:01: warning: empty file, contains no compilation units
6788 Otherwise, the output is simply the error messages, if any. No object file or
6789 ALI file is generated by a syntax-only compilation. Also, no units other
6790 than the one specified are accessed. For example, if a unit @code{X}
6791 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6792 check only mode does not access the source file containing unit
6795 @cindex Multiple units, syntax checking
6796 Normally, GNAT allows only a single unit in a source file. However, this
6797 restriction does not apply in syntax-check-only mode, and it is possible
6798 to check a file containing multiple compilation units concatenated
6799 together. This is primarily used by the @code{gnatchop} utility
6800 (@pxref{Renaming Files Using gnatchop}).
6803 @node Using gcc for Semantic Checking
6804 @subsection Using @command{gcc} for Semantic Checking
6807 @cindex @option{-gnatc} (@command{gcc})
6811 The @code{c} stands for ``check''.
6813 Causes the compiler to operate in semantic check mode,
6814 with full checking for all illegalities specified in the
6815 Ada Reference Manual, but without generation of any object code
6816 (no object file is generated).
6818 Because dependent files must be accessed, you must follow the GNAT
6819 semantic restrictions on file structuring to operate in this mode:
6823 The needed source files must be accessible
6824 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6827 Each file must contain only one compilation unit.
6830 The file name and unit name must match (@pxref{File Naming Rules}).
6833 The output consists of error messages as appropriate. No object file is
6834 generated. An @file{ALI} file is generated for use in the context of
6835 cross-reference tools, but this file is marked as not being suitable
6836 for binding (since no object file is generated).
6837 The checking corresponds exactly to the notion of
6838 legality in the Ada Reference Manual.
6840 Any unit can be compiled in semantics-checking-only mode, including
6841 units that would not normally be compiled (subunits,
6842 and specifications where a separate body is present).
6845 @node Compiling Different Versions of Ada
6846 @subsection Compiling Different Versions of Ada
6849 The switches described in this section allow you to explicitly specify
6850 the version of the Ada language that your programs are written in.
6851 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6852 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6853 indicate Ada 83 compatibility mode.
6856 @cindex Compatibility with Ada 83
6858 @item -gnat83 (Ada 83 Compatibility Mode)
6859 @cindex @option{-gnat83} (@command{gcc})
6860 @cindex ACVC, Ada 83 tests
6864 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6865 specifies that the program is to be compiled in Ada 83 mode. With
6866 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6867 semantics where this can be done easily.
6868 It is not possible to guarantee this switch does a perfect
6869 job; some subtle tests, such as are
6870 found in earlier ACVC tests (and that have been removed from the ACATS suite
6871 for Ada 95), might not compile correctly.
6872 Nevertheless, this switch may be useful in some circumstances, for example
6873 where, due to contractual reasons, existing code needs to be maintained
6874 using only Ada 83 features.
6876 With few exceptions (most notably the need to use @code{<>} on
6877 @cindex Generic formal parameters
6878 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6879 reserved words, and the use of packages
6880 with optional bodies), it is not necessary to specify the
6881 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6882 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6883 a correct Ada 83 program is usually also a correct program
6884 in these later versions of the language standard.
6885 For further information, please refer to @ref{Compatibility and Porting Guide}.
6887 @item -gnat95 (Ada 95 mode)
6888 @cindex @option{-gnat95} (@command{gcc})
6892 This switch directs the compiler to implement the Ada 95 version of the
6894 Since Ada 95 is almost completely upwards
6895 compatible with Ada 83, Ada 83 programs may generally be compiled using
6896 this switch (see the description of the @option{-gnat83} switch for further
6897 information about Ada 83 mode).
6898 If an Ada 2005 program is compiled in Ada 95 mode,
6899 uses of the new Ada 2005 features will cause error
6900 messages or warnings.
6902 This switch also can be used to cancel the effect of a previous
6903 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6905 @item -gnat05 (Ada 2005 mode)
6906 @cindex @option{-gnat05} (@command{gcc})
6907 @cindex Ada 2005 mode
6910 This switch directs the compiler to implement the Ada 2005 version of the
6912 Since Ada 2005 is almost completely upwards
6913 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6914 may generally be compiled using this switch (see the description of the
6915 @option{-gnat83} and @option{-gnat95} switches for further
6918 For information about the approved ``Ada Issues'' that have been incorporated
6919 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6920 Included with GNAT releases is a file @file{features-ada0y} that describes
6921 the set of implemented Ada 2005 features.
6925 @node Character Set Control
6926 @subsection Character Set Control
6928 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6929 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6932 Normally GNAT recognizes the Latin-1 character set in source program
6933 identifiers, as described in the Ada Reference Manual.
6935 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6936 single character ^^or word^ indicating the character set, as follows:
6940 ISO 8859-1 (Latin-1) identifiers
6943 ISO 8859-2 (Latin-2) letters allowed in identifiers
6946 ISO 8859-3 (Latin-3) letters allowed in identifiers
6949 ISO 8859-4 (Latin-4) letters allowed in identifiers
6952 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6955 ISO 8859-15 (Latin-9) letters allowed in identifiers
6958 IBM PC letters (code page 437) allowed in identifiers
6961 IBM PC letters (code page 850) allowed in identifiers
6963 @item ^f^FULL_UPPER^
6964 Full upper-half codes allowed in identifiers
6967 No upper-half codes allowed in identifiers
6970 Wide-character codes (that is, codes greater than 255)
6971 allowed in identifiers
6974 @xref{Foreign Language Representation}, for full details on the
6975 implementation of these character sets.
6977 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6978 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6979 Specify the method of encoding for wide characters.
6980 @var{e} is one of the following:
6985 Hex encoding (brackets coding also recognized)
6988 Upper half encoding (brackets encoding also recognized)
6991 Shift/JIS encoding (brackets encoding also recognized)
6994 EUC encoding (brackets encoding also recognized)
6997 UTF-8 encoding (brackets encoding also recognized)
7000 Brackets encoding only (default value)
7002 For full details on these encoding
7003 methods see @ref{Wide Character Encodings}.
7004 Note that brackets coding is always accepted, even if one of the other
7005 options is specified, so for example @option{-gnatW8} specifies that both
7006 brackets and UTF-8 encodings will be recognized. The units that are
7007 with'ed directly or indirectly will be scanned using the specified
7008 representation scheme, and so if one of the non-brackets scheme is
7009 used, it must be used consistently throughout the program. However,
7010 since brackets encoding is always recognized, it may be conveniently
7011 used in standard libraries, allowing these libraries to be used with
7012 any of the available coding schemes.
7015 If no @option{-gnatW?} parameter is present, then the default
7016 representation is normally Brackets encoding only. However, if the
7017 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
7018 byte order mark or BOM for UTF-8), then these three characters are
7019 skipped and the default representation for the file is set to UTF-8.
7021 Note that the wide character representation that is specified (explicitly
7022 or by default) for the main program also acts as the default encoding used
7023 for Wide_Text_IO files if not specifically overridden by a WCEM form
7027 @node File Naming Control
7028 @subsection File Naming Control
7031 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
7032 @cindex @option{-gnatk} (@command{gcc})
7033 Activates file name ``krunching''. @var{n}, a decimal integer in the range
7034 1-999, indicates the maximum allowable length of a file name (not
7035 including the @file{.ads} or @file{.adb} extension). The default is not
7036 to enable file name krunching.
7038 For the source file naming rules, @xref{File Naming Rules}.
7041 @node Subprogram Inlining Control
7042 @subsection Subprogram Inlining Control
7047 @cindex @option{-gnatn} (@command{gcc})
7049 The @code{n} here is intended to suggest the first syllable of the
7052 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7053 inlining to actually occur, optimization must be enabled. To enable
7054 inlining of subprograms specified by pragma @code{Inline},
7055 you must also specify this switch.
7056 In the absence of this switch, GNAT does not attempt
7057 inlining and does not need to access the bodies of
7058 subprograms for which @code{pragma Inline} is specified if they are not
7059 in the current unit.
7061 If you specify this switch the compiler will access these bodies,
7062 creating an extra source dependency for the resulting object file, and
7063 where possible, the call will be inlined.
7064 For further details on when inlining is possible
7065 see @ref{Inlining of Subprograms}.
7068 @cindex @option{-gnatN} (@command{gcc})
7069 This switch activates front-end inlining which also
7070 generates additional dependencies.
7072 When using a gcc-based back end (in practice this means using any version
7073 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7074 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7075 Historically front end inlining was more extensive than the gcc back end
7076 inlining, but that is no longer the case.
7079 @node Auxiliary Output Control
7080 @subsection Auxiliary Output Control
7084 @cindex @option{-gnatt} (@command{gcc})
7085 @cindex Writing internal trees
7086 @cindex Internal trees, writing to file
7087 Causes GNAT to write the internal tree for a unit to a file (with the
7088 extension @file{.adt}.
7089 This not normally required, but is used by separate analysis tools.
7091 these tools do the necessary compilations automatically, so you should
7092 not have to specify this switch in normal operation.
7093 Note that the combination of switches @option{-gnatct}
7094 generates a tree in the form required by ASIS applications.
7097 @cindex @option{-gnatu} (@command{gcc})
7098 Print a list of units required by this compilation on @file{stdout}.
7099 The listing includes all units on which the unit being compiled depends
7100 either directly or indirectly.
7103 @item -pass-exit-codes
7104 @cindex @option{-pass-exit-codes} (@command{gcc})
7105 If this switch is not used, the exit code returned by @command{gcc} when
7106 compiling multiple files indicates whether all source files have
7107 been successfully used to generate object files or not.
7109 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7110 exit status and allows an integrated development environment to better
7111 react to a compilation failure. Those exit status are:
7115 There was an error in at least one source file.
7117 At least one source file did not generate an object file.
7119 The compiler died unexpectedly (internal error for example).
7121 An object file has been generated for every source file.
7126 @node Debugging Control
7127 @subsection Debugging Control
7131 @cindex Debugging options
7134 @cindex @option{-gnatd} (@command{gcc})
7135 Activate internal debugging switches. @var{x} is a letter or digit, or
7136 string of letters or digits, which specifies the type of debugging
7137 outputs desired. Normally these are used only for internal development
7138 or system debugging purposes. You can find full documentation for these
7139 switches in the body of the @code{Debug} unit in the compiler source
7140 file @file{debug.adb}.
7144 @cindex @option{-gnatG} (@command{gcc})
7145 This switch causes the compiler to generate auxiliary output containing
7146 a pseudo-source listing of the generated expanded code. Like most Ada
7147 compilers, GNAT works by first transforming the high level Ada code into
7148 lower level constructs. For example, tasking operations are transformed
7149 into calls to the tasking run-time routines. A unique capability of GNAT
7150 is to list this expanded code in a form very close to normal Ada source.
7151 This is very useful in understanding the implications of various Ada
7152 usage on the efficiency of the generated code. There are many cases in
7153 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7154 generate a lot of run-time code. By using @option{-gnatG} you can identify
7155 these cases, and consider whether it may be desirable to modify the coding
7156 approach to improve efficiency.
7158 The optional parameter @code{nn} if present after -gnatG specifies an
7159 alternative maximum line length that overrides the normal default of 72.
7160 This value is in the range 40-999999, values less than 40 being silently
7161 reset to 40. The equal sign is optional.
7163 The format of the output is very similar to standard Ada source, and is
7164 easily understood by an Ada programmer. The following special syntactic
7165 additions correspond to low level features used in the generated code that
7166 do not have any exact analogies in pure Ada source form. The following
7167 is a partial list of these special constructions. See the spec
7168 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7170 If the switch @option{-gnatL} is used in conjunction with
7171 @cindex @option{-gnatL} (@command{gcc})
7172 @option{-gnatG}, then the original source lines are interspersed
7173 in the expanded source (as comment lines with the original line number).
7176 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7177 Shows the storage pool being used for an allocator.
7179 @item at end @var{procedure-name};
7180 Shows the finalization (cleanup) procedure for a scope.
7182 @item (if @var{expr} then @var{expr} else @var{expr})
7183 Conditional expression equivalent to the @code{x?y:z} construction in C.
7185 @item @var{target}^^^(@var{source})
7186 A conversion with floating-point truncation instead of rounding.
7188 @item @var{target}?(@var{source})
7189 A conversion that bypasses normal Ada semantic checking. In particular
7190 enumeration types and fixed-point types are treated simply as integers.
7192 @item @var{target}?^^^(@var{source})
7193 Combines the above two cases.
7195 @item @var{x} #/ @var{y}
7196 @itemx @var{x} #mod @var{y}
7197 @itemx @var{x} #* @var{y}
7198 @itemx @var{x} #rem @var{y}
7199 A division or multiplication of fixed-point values which are treated as
7200 integers without any kind of scaling.
7202 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7203 Shows the storage pool associated with a @code{free} statement.
7205 @item [subtype or type declaration]
7206 Used to list an equivalent declaration for an internally generated
7207 type that is referenced elsewhere in the listing.
7209 @c @item freeze @var{type-name} @ovar{actions}
7210 @c Expanding @ovar macro inline (explanation in macro def comments)
7211 @item freeze @var{type-name} @r{[}@var{actions}@r{]}
7212 Shows the point at which @var{type-name} is frozen, with possible
7213 associated actions to be performed at the freeze point.
7215 @item reference @var{itype}
7216 Reference (and hence definition) to internal type @var{itype}.
7218 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7219 Intrinsic function call.
7221 @item @var{label-name} : label
7222 Declaration of label @var{labelname}.
7224 @item #$ @var{subprogram-name}
7225 An implicit call to a run-time support routine
7226 (to meet the requirement of H.3.1(9) in a
7229 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7230 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7231 @var{expr}, but handled more efficiently).
7233 @item [constraint_error]
7234 Raise the @code{Constraint_Error} exception.
7236 @item @var{expression}'reference
7237 A pointer to the result of evaluating @var{expression}.
7239 @item @var{target-type}!(@var{source-expression})
7240 An unchecked conversion of @var{source-expression} to @var{target-type}.
7242 @item [@var{numerator}/@var{denominator}]
7243 Used to represent internal real literals (that) have no exact
7244 representation in base 2-16 (for example, the result of compile time
7245 evaluation of the expression 1.0/27.0).
7249 @cindex @option{-gnatD} (@command{gcc})
7250 When used in conjunction with @option{-gnatG}, this switch causes
7251 the expanded source, as described above for
7252 @option{-gnatG} to be written to files with names
7253 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7254 instead of to the standard output file. For
7255 example, if the source file name is @file{hello.adb}, then a file
7256 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7257 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7258 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7259 you to do source level debugging using the generated code which is
7260 sometimes useful for complex code, for example to find out exactly
7261 which part of a complex construction raised an exception. This switch
7262 also suppress generation of cross-reference information (see
7263 @option{-gnatx}) since otherwise the cross-reference information
7264 would refer to the @file{^.dg^.DG^} file, which would cause
7265 confusion since this is not the original source file.
7267 Note that @option{-gnatD} actually implies @option{-gnatG}
7268 automatically, so it is not necessary to give both options.
7269 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7271 If the switch @option{-gnatL} is used in conjunction with
7272 @cindex @option{-gnatL} (@command{gcc})
7273 @option{-gnatDG}, then the original source lines are interspersed
7274 in the expanded source (as comment lines with the original line number).
7276 The optional parameter @code{nn} if present after -gnatD specifies an
7277 alternative maximum line length that overrides the normal default of 72.
7278 This value is in the range 40-999999, values less than 40 being silently
7279 reset to 40. The equal sign is optional.
7282 @cindex @option{-gnatr} (@command{gcc})
7283 @cindex pragma Restrictions
7284 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7285 so that violation of restrictions causes warnings rather than illegalities.
7286 This is useful during the development process when new restrictions are added
7287 or investigated. The switch also causes pragma Profile to be treated as
7288 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7289 restriction warnings rather than restrictions.
7292 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7293 @cindex @option{-gnatR} (@command{gcc})
7294 This switch controls output from the compiler of a listing showing
7295 representation information for declared types and objects. For
7296 @option{-gnatR0}, no information is output (equivalent to omitting
7297 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7298 so @option{-gnatR} with no parameter has the same effect), size and alignment
7299 information is listed for declared array and record types. For
7300 @option{-gnatR2}, size and alignment information is listed for all
7301 declared types and objects. Finally @option{-gnatR3} includes symbolic
7302 expressions for values that are computed at run time for
7303 variant records. These symbolic expressions have a mostly obvious
7304 format with #n being used to represent the value of the n'th
7305 discriminant. See source files @file{repinfo.ads/adb} in the
7306 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7307 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7308 the output is to a file with the name @file{^file.rep^file_REP^} where
7309 file is the name of the corresponding source file.
7312 @item /REPRESENTATION_INFO
7313 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7314 This qualifier controls output from the compiler of a listing showing
7315 representation information for declared types and objects. For
7316 @option{/REPRESENTATION_INFO=NONE}, no information is output
7317 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7318 @option{/REPRESENTATION_INFO} without option is equivalent to
7319 @option{/REPRESENTATION_INFO=ARRAYS}.
7320 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7321 information is listed for declared array and record types. For
7322 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7323 is listed for all expression information for values that are computed
7324 at run time for variant records. These symbolic expressions have a mostly
7325 obvious format with #n being used to represent the value of the n'th
7326 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7327 @code{GNAT} sources for full details on the format of
7328 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7329 If _FILE is added at the end of an option
7330 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7331 then the output is to a file with the name @file{file_REP} where
7332 file is the name of the corresponding source file.
7334 Note that it is possible for record components to have zero size. In
7335 this case, the component clause uses an obvious extension of permitted
7336 Ada syntax, for example @code{at 0 range 0 .. -1}.
7338 Representation information requires that code be generated (since it is the
7339 code generator that lays out complex data structures). If an attempt is made
7340 to output representation information when no code is generated, for example
7341 when a subunit is compiled on its own, then no information can be generated
7342 and the compiler outputs a message to this effect.
7345 @cindex @option{-gnatS} (@command{gcc})
7346 The use of the switch @option{-gnatS} for an
7347 Ada compilation will cause the compiler to output a
7348 representation of package Standard in a form very
7349 close to standard Ada. It is not quite possible to
7350 do this entirely in standard Ada (since new
7351 numeric base types cannot be created in standard
7352 Ada), but the output is easily
7353 readable to any Ada programmer, and is useful to
7354 determine the characteristics of target dependent
7355 types in package Standard.
7358 @cindex @option{-gnatx} (@command{gcc})
7359 Normally the compiler generates full cross-referencing information in
7360 the @file{ALI} file. This information is used by a number of tools,
7361 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7362 suppresses this information. This saves some space and may slightly
7363 speed up compilation, but means that these tools cannot be used.
7366 @node Exception Handling Control
7367 @subsection Exception Handling Control
7370 GNAT uses two methods for handling exceptions at run-time. The
7371 @code{setjmp/longjmp} method saves the context when entering
7372 a frame with an exception handler. Then when an exception is
7373 raised, the context can be restored immediately, without the
7374 need for tracing stack frames. This method provides very fast
7375 exception propagation, but introduces significant overhead for
7376 the use of exception handlers, even if no exception is raised.
7378 The other approach is called ``zero cost'' exception handling.
7379 With this method, the compiler builds static tables to describe
7380 the exception ranges. No dynamic code is required when entering
7381 a frame containing an exception handler. When an exception is
7382 raised, the tables are used to control a back trace of the
7383 subprogram invocation stack to locate the required exception
7384 handler. This method has considerably poorer performance for
7385 the propagation of exceptions, but there is no overhead for
7386 exception handlers if no exception is raised. Note that in this
7387 mode and in the context of mixed Ada and C/C++ programming,
7388 to propagate an exception through a C/C++ code, the C/C++ code
7389 must be compiled with the @option{-funwind-tables} GCC's
7392 The following switches may be used to control which of the
7393 two exception handling methods is used.
7399 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7400 This switch causes the setjmp/longjmp run-time (when available) to be used
7401 for exception handling. If the default
7402 mechanism for the target is zero cost exceptions, then
7403 this switch can be used to modify this default, and must be
7404 used for all units in the partition.
7405 This option is rarely used. One case in which it may be
7406 advantageous is if you have an application where exception
7407 raising is common and the overall performance of the
7408 application is improved by favoring exception propagation.
7411 @cindex @option{--RTS=zcx} (@command{gnatmake})
7412 @cindex Zero Cost Exceptions
7413 This switch causes the zero cost approach to be used
7414 for exception handling. If this is the default mechanism for the
7415 target (see below), then this switch is unneeded. If the default
7416 mechanism for the target is setjmp/longjmp exceptions, then
7417 this switch can be used to modify this default, and must be
7418 used for all units in the partition.
7419 This option can only be used if the zero cost approach
7420 is available for the target in use, otherwise it will generate an error.
7424 The same option @option{--RTS} must be used both for @command{gcc}
7425 and @command{gnatbind}. Passing this option to @command{gnatmake}
7426 (@pxref{Switches for gnatmake}) will ensure the required consistency
7427 through the compilation and binding steps.
7429 @node Units to Sources Mapping Files
7430 @subsection Units to Sources Mapping Files
7434 @item -gnatem=@var{path}
7435 @cindex @option{-gnatem} (@command{gcc})
7436 A mapping file is a way to communicate to the compiler two mappings:
7437 from unit names to file names (without any directory information) and from
7438 file names to path names (with full directory information). These mappings
7439 are used by the compiler to short-circuit the path search.
7441 The use of mapping files is not required for correct operation of the
7442 compiler, but mapping files can improve efficiency, particularly when
7443 sources are read over a slow network connection. In normal operation,
7444 you need not be concerned with the format or use of mapping files,
7445 and the @option{-gnatem} switch is not a switch that you would use
7446 explicitly. It is intended primarily for use by automatic tools such as
7447 @command{gnatmake} running under the project file facility. The
7448 description here of the format of mapping files is provided
7449 for completeness and for possible use by other tools.
7451 A mapping file is a sequence of sets of three lines. In each set, the
7452 first line is the unit name, in lower case, with @code{%s} appended
7453 for specs and @code{%b} appended for bodies; the second line is the
7454 file name; and the third line is the path name.
7460 /gnat/project1/sources/main.2.ada
7463 When the switch @option{-gnatem} is specified, the compiler will
7464 create in memory the two mappings from the specified file. If there is
7465 any problem (nonexistent file, truncated file or duplicate entries),
7466 no mapping will be created.
7468 Several @option{-gnatem} switches may be specified; however, only the
7469 last one on the command line will be taken into account.
7471 When using a project file, @command{gnatmake} creates a temporary
7472 mapping file and communicates it to the compiler using this switch.
7476 @node Integrated Preprocessing
7477 @subsection Integrated Preprocessing
7480 GNAT sources may be preprocessed immediately before compilation.
7481 In this case, the actual
7482 text of the source is not the text of the source file, but is derived from it
7483 through a process called preprocessing. Integrated preprocessing is specified
7484 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7485 indicates, through a text file, the preprocessing data to be used.
7486 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7489 Note that when integrated preprocessing is used, the output from the
7490 preprocessor is not written to any external file. Instead it is passed
7491 internally to the compiler. If you need to preserve the result of
7492 preprocessing in a file, then you should use @command{gnatprep}
7493 to perform the desired preprocessing in stand-alone mode.
7496 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7497 used when Integrated Preprocessing is used. The reason is that preprocessing
7498 with another Preprocessing Data file without changing the sources will
7499 not trigger recompilation without this switch.
7502 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7503 always trigger recompilation for sources that are preprocessed,
7504 because @command{gnatmake} cannot compute the checksum of the source after
7508 The actual preprocessing function is described in details in section
7509 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7510 preprocessing is triggered and parameterized.
7514 @item -gnatep=@var{file}
7515 @cindex @option{-gnatep} (@command{gcc})
7516 This switch indicates to the compiler the file name (without directory
7517 information) of the preprocessor data file to use. The preprocessor data file
7518 should be found in the source directories.
7521 A preprocessing data file is a text file with significant lines indicating
7522 how should be preprocessed either a specific source or all sources not
7523 mentioned in other lines. A significant line is a nonempty, non-comment line.
7524 Comments are similar to Ada comments.
7527 Each significant line starts with either a literal string or the character '*'.
7528 A literal string is the file name (without directory information) of the source
7529 to preprocess. A character '*' indicates the preprocessing for all the sources
7530 that are not specified explicitly on other lines (order of the lines is not
7531 significant). It is an error to have two lines with the same file name or two
7532 lines starting with the character '*'.
7535 After the file name or the character '*', another optional literal string
7536 indicating the file name of the definition file to be used for preprocessing
7537 (@pxref{Form of Definitions File}). The definition files are found by the
7538 compiler in one of the source directories. In some cases, when compiling
7539 a source in a directory other than the current directory, if the definition
7540 file is in the current directory, it may be necessary to add the current
7541 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7542 the compiler would not find the definition file.
7545 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7546 be found. Those ^switches^switches^ are:
7551 Causes both preprocessor lines and the lines deleted by
7552 preprocessing to be replaced by blank lines, preserving the line number.
7553 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7554 it cancels the effect of @option{-c}.
7557 Causes both preprocessor lines and the lines deleted
7558 by preprocessing to be retained as comments marked
7559 with the special string ``@code{--! }''.
7561 @item -Dsymbol=value
7562 Define or redefine a symbol, associated with value. A symbol is an Ada
7563 identifier, or an Ada reserved word, with the exception of @code{if},
7564 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7565 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7566 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7567 same name defined in a definition file.
7570 Causes a sorted list of symbol names and values to be
7571 listed on the standard output file.
7574 Causes undefined symbols to be treated as having the value @code{FALSE}
7576 of a preprocessor test. In the absence of this option, an undefined symbol in
7577 a @code{#if} or @code{#elsif} test will be treated as an error.
7582 Examples of valid lines in a preprocessor data file:
7585 "toto.adb" "prep.def" -u
7586 -- preprocess "toto.adb", using definition file "prep.def",
7587 -- undefined symbol are False.
7590 -- preprocess all other sources without a definition file;
7591 -- suppressed lined are commented; symbol VERSION has the value V101.
7593 "titi.adb" "prep2.def" -s
7594 -- preprocess "titi.adb", using definition file "prep2.def";
7595 -- list all symbols with their values.
7598 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7599 @cindex @option{-gnateD} (@command{gcc})
7600 Define or redefine a preprocessing symbol, associated with value. If no value
7601 is given on the command line, then the value of the symbol is @code{True}.
7602 A symbol is an identifier, following normal Ada (case-insensitive)
7603 rules for its syntax, and value is any sequence (including an empty sequence)
7604 of characters from the set (letters, digits, period, underline).
7605 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7606 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7609 A symbol declared with this ^switch^switch^ on the command line replaces a
7610 symbol with the same name either in a definition file or specified with a
7611 ^switch^switch^ -D in the preprocessor data file.
7614 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7617 When integrated preprocessing is performed and the preprocessor modifies
7618 the source text, write the result of this preprocessing into a file
7619 <source>^.prep^_prep^.
7623 @node Code Generation Control
7624 @subsection Code Generation Control
7628 The GCC technology provides a wide range of target dependent
7629 @option{-m} switches for controlling
7630 details of code generation with respect to different versions of
7631 architectures. This includes variations in instruction sets (e.g.@:
7632 different members of the power pc family), and different requirements
7633 for optimal arrangement of instructions (e.g.@: different members of
7634 the x86 family). The list of available @option{-m} switches may be
7635 found in the GCC documentation.
7637 Use of these @option{-m} switches may in some cases result in improved
7640 The GNAT Pro technology is tested and qualified without any
7641 @option{-m} switches,
7642 so generally the most reliable approach is to avoid the use of these
7643 switches. However, we generally expect most of these switches to work
7644 successfully with GNAT Pro, and many customers have reported successful
7645 use of these options.
7647 Our general advice is to avoid the use of @option{-m} switches unless
7648 special needs lead to requirements in this area. In particular,
7649 there is no point in using @option{-m} switches to improve performance
7650 unless you actually see a performance improvement.
7654 @subsection Return Codes
7655 @cindex Return Codes
7656 @cindex @option{/RETURN_CODES=VMS}
7659 On VMS, GNAT compiled programs return POSIX-style codes by default,
7660 e.g.@: @option{/RETURN_CODES=POSIX}.
7662 To enable VMS style return codes, use GNAT BIND and LINK with the option
7663 @option{/RETURN_CODES=VMS}. For example:
7666 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7667 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7671 Programs built with /RETURN_CODES=VMS are suitable to be called in
7672 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7673 are suitable for spawning with appropriate GNAT RTL routines.
7677 @node Search Paths and the Run-Time Library (RTL)
7678 @section Search Paths and the Run-Time Library (RTL)
7681 With the GNAT source-based library system, the compiler must be able to
7682 find source files for units that are needed by the unit being compiled.
7683 Search paths are used to guide this process.
7685 The compiler compiles one source file whose name must be given
7686 explicitly on the command line. In other words, no searching is done
7687 for this file. To find all other source files that are needed (the most
7688 common being the specs of units), the compiler examines the following
7689 directories, in the following order:
7693 The directory containing the source file of the main unit being compiled
7694 (the file name on the command line).
7697 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7698 @command{gcc} command line, in the order given.
7701 @findex ADA_PRJ_INCLUDE_FILE
7702 Each of the directories listed in the text file whose name is given
7703 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7706 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7707 driver when project files are used. It should not normally be set
7711 @findex ADA_INCLUDE_PATH
7712 Each of the directories listed in the value of the
7713 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7715 Construct this value
7716 exactly as the @env{PATH} environment variable: a list of directory
7717 names separated by colons (semicolons when working with the NT version).
7720 Normally, define this value as a logical name containing a comma separated
7721 list of directory names.
7723 This variable can also be defined by means of an environment string
7724 (an argument to the HP C exec* set of functions).
7728 DEFINE ANOTHER_PATH FOO:[BAG]
7729 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7732 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7733 first, followed by the standard Ada
7734 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7735 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7736 (Text_IO, Sequential_IO, etc)
7737 instead of the standard Ada packages. Thus, in order to get the standard Ada
7738 packages by default, ADA_INCLUDE_PATH must be redefined.
7742 The content of the @file{ada_source_path} file which is part of the GNAT
7743 installation tree and is used to store standard libraries such as the
7744 GNAT Run Time Library (RTL) source files.
7746 @ref{Installing a library}
7751 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7752 inhibits the use of the directory
7753 containing the source file named in the command line. You can still
7754 have this directory on your search path, but in this case it must be
7755 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7757 Specifying the switch @option{-nostdinc}
7758 inhibits the search of the default location for the GNAT Run Time
7759 Library (RTL) source files.
7761 The compiler outputs its object files and ALI files in the current
7764 Caution: The object file can be redirected with the @option{-o} switch;
7765 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7766 so the @file{ALI} file will not go to the right place. Therefore, you should
7767 avoid using the @option{-o} switch.
7771 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7772 children make up the GNAT RTL, together with the simple @code{System.IO}
7773 package used in the @code{"Hello World"} example. The sources for these units
7774 are needed by the compiler and are kept together in one directory. Not
7775 all of the bodies are needed, but all of the sources are kept together
7776 anyway. In a normal installation, you need not specify these directory
7777 names when compiling or binding. Either the environment variables or
7778 the built-in defaults cause these files to be found.
7780 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7781 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7782 consisting of child units of @code{GNAT}. This is a collection of generally
7783 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7784 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7786 Besides simplifying access to the RTL, a major use of search paths is
7787 in compiling sources from multiple directories. This can make
7788 development environments much more flexible.
7790 @node Order of Compilation Issues
7791 @section Order of Compilation Issues
7794 If, in our earlier example, there was a spec for the @code{hello}
7795 procedure, it would be contained in the file @file{hello.ads}; yet this
7796 file would not have to be explicitly compiled. This is the result of the
7797 model we chose to implement library management. Some of the consequences
7798 of this model are as follows:
7802 There is no point in compiling specs (except for package
7803 specs with no bodies) because these are compiled as needed by clients. If
7804 you attempt a useless compilation, you will receive an error message.
7805 It is also useless to compile subunits because they are compiled as needed
7809 There are no order of compilation requirements: performing a
7810 compilation never obsoletes anything. The only way you can obsolete
7811 something and require recompilations is to modify one of the
7812 source files on which it depends.
7815 There is no library as such, apart from the ALI files
7816 (@pxref{The Ada Library Information Files}, for information on the format
7817 of these files). For now we find it convenient to create separate ALI files,
7818 but eventually the information therein may be incorporated into the object
7822 When you compile a unit, the source files for the specs of all units
7823 that it @code{with}'s, all its subunits, and the bodies of any generics it
7824 instantiates must be available (reachable by the search-paths mechanism
7825 described above), or you will receive a fatal error message.
7832 The following are some typical Ada compilation command line examples:
7835 @item $ gcc -c xyz.adb
7836 Compile body in file @file{xyz.adb} with all default options.
7839 @item $ gcc -c -O2 -gnata xyz-def.adb
7842 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7845 Compile the child unit package in file @file{xyz-def.adb} with extensive
7846 optimizations, and pragma @code{Assert}/@code{Debug} statements
7849 @item $ gcc -c -gnatc abc-def.adb
7850 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7854 @node Binding Using gnatbind
7855 @chapter Binding Using @code{gnatbind}
7859 * Running gnatbind::
7860 * Switches for gnatbind::
7861 * Command-Line Access::
7862 * Search Paths for gnatbind::
7863 * Examples of gnatbind Usage::
7867 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7868 to bind compiled GNAT objects.
7870 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7871 driver (see @ref{The GNAT Driver and Project Files}).
7873 The @code{gnatbind} program performs four separate functions:
7877 Checks that a program is consistent, in accordance with the rules in
7878 Chapter 10 of the Ada Reference Manual. In particular, error
7879 messages are generated if a program uses inconsistent versions of a
7883 Checks that an acceptable order of elaboration exists for the program
7884 and issues an error message if it cannot find an order of elaboration
7885 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7888 Generates a main program incorporating the given elaboration order.
7889 This program is a small Ada package (body and spec) that
7890 must be subsequently compiled
7891 using the GNAT compiler. The necessary compilation step is usually
7892 performed automatically by @command{gnatlink}. The two most important
7893 functions of this program
7894 are to call the elaboration routines of units in an appropriate order
7895 and to call the main program.
7898 Determines the set of object files required by the given main program.
7899 This information is output in the forms of comments in the generated program,
7900 to be read by the @command{gnatlink} utility used to link the Ada application.
7903 @node Running gnatbind
7904 @section Running @code{gnatbind}
7907 The form of the @code{gnatbind} command is
7910 @c $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7911 @c Expanding @ovar macro inline (explanation in macro def comments)
7912 $ gnatbind @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]} @r{[}@var{switches}@r{]}
7916 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7917 unit body. @code{gnatbind} constructs an Ada
7918 package in two files whose names are
7919 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7920 For example, if given the
7921 parameter @file{hello.ali}, for a main program contained in file
7922 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7923 and @file{b~hello.adb}.
7925 When doing consistency checking, the binder takes into consideration
7926 any source files it can locate. For example, if the binder determines
7927 that the given main program requires the package @code{Pack}, whose
7929 file is @file{pack.ali} and whose corresponding source spec file is
7930 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7931 (using the same search path conventions as previously described for the
7932 @command{gcc} command). If it can locate this source file, it checks that
7934 or source checksums of the source and its references to in @file{ALI} files
7935 match. In other words, any @file{ALI} files that mentions this spec must have
7936 resulted from compiling this version of the source file (or in the case
7937 where the source checksums match, a version close enough that the
7938 difference does not matter).
7940 @cindex Source files, use by binder
7941 The effect of this consistency checking, which includes source files, is
7942 that the binder ensures that the program is consistent with the latest
7943 version of the source files that can be located at bind time. Editing a
7944 source file without compiling files that depend on the source file cause
7945 error messages to be generated by the binder.
7947 For example, suppose you have a main program @file{hello.adb} and a
7948 package @code{P}, from file @file{p.ads} and you perform the following
7953 Enter @code{gcc -c hello.adb} to compile the main program.
7956 Enter @code{gcc -c p.ads} to compile package @code{P}.
7959 Edit file @file{p.ads}.
7962 Enter @code{gnatbind hello}.
7966 At this point, the file @file{p.ali} contains an out-of-date time stamp
7967 because the file @file{p.ads} has been edited. The attempt at binding
7968 fails, and the binder generates the following error messages:
7971 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7972 error: "p.ads" has been modified and must be recompiled
7976 Now both files must be recompiled as indicated, and then the bind can
7977 succeed, generating a main program. You need not normally be concerned
7978 with the contents of this file, but for reference purposes a sample
7979 binder output file is given in @ref{Example of Binder Output File}.
7981 In most normal usage, the default mode of @command{gnatbind} which is to
7982 generate the main package in Ada, as described in the previous section.
7983 In particular, this means that any Ada programmer can read and understand
7984 the generated main program. It can also be debugged just like any other
7985 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7986 @command{gnatbind} and @command{gnatlink}.
7988 @node Switches for gnatbind
7989 @section Switches for @command{gnatbind}
7992 The following switches are available with @code{gnatbind}; details will
7993 be presented in subsequent sections.
7996 * Consistency-Checking Modes::
7997 * Binder Error Message Control::
7998 * Elaboration Control::
8000 * Binding with Non-Ada Main Programs::
8001 * Binding Programs with No Main Subprogram::
8008 @cindex @option{--version} @command{gnatbind}
8009 Display Copyright and version, then exit disregarding all other options.
8012 @cindex @option{--help} @command{gnatbind}
8013 If @option{--version} was not used, display usage, then exit disregarding
8017 @cindex @option{-a} @command{gnatbind}
8018 Indicates that, if supported by the platform, the adainit procedure should
8019 be treated as an initialisation routine by the linker (a constructor). This
8020 is intended to be used by the Project Manager to automatically initialize
8021 shared Stand-Alone Libraries.
8023 @item ^-aO^/OBJECT_SEARCH^
8024 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
8025 Specify directory to be searched for ALI files.
8027 @item ^-aI^/SOURCE_SEARCH^
8028 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8029 Specify directory to be searched for source file.
8031 @item ^-A^/ALI_LIST^@r{[=}@var{filename}@r{]}
8032 @cindex @option{^-A^/ALI_LIST^} (@command{gnatbind})
8033 Output ALI list (to standard output or to the named file).
8035 @item ^-b^/REPORT_ERRORS=BRIEF^
8036 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
8037 Generate brief messages to @file{stderr} even if verbose mode set.
8039 @item ^-c^/NOOUTPUT^
8040 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
8041 Check only, no generation of binder output file.
8043 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8044 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8045 This switch can be used to change the default task stack size value
8046 to a specified size @var{nn}, which is expressed in bytes by default, or
8047 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8049 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8050 in effect, to completing all task specs with
8051 @smallexample @c ada
8052 pragma Storage_Size (nn);
8054 When they do not already have such a pragma.
8056 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8057 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8058 This switch can be used to change the default secondary stack size value
8059 to a specified size @var{nn}, which is expressed in bytes by default, or
8060 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8063 The secondary stack is used to deal with functions that return a variable
8064 sized result, for example a function returning an unconstrained
8065 String. There are two ways in which this secondary stack is allocated.
8067 For most targets, the secondary stack is growing on demand and is allocated
8068 as a chain of blocks in the heap. The -D option is not very
8069 relevant. It only give some control over the size of the allocated
8070 blocks (whose size is the minimum of the default secondary stack size value,
8071 and the actual size needed for the current allocation request).
8073 For certain targets, notably VxWorks 653,
8074 the secondary stack is allocated by carving off a fixed ratio chunk of the
8075 primary task stack. The -D option is used to define the
8076 size of the environment task's secondary stack.
8078 @item ^-e^/ELABORATION_DEPENDENCIES^
8079 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8080 Output complete list of elaboration-order dependencies.
8082 @item ^-E^/STORE_TRACEBACKS^
8083 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8084 Store tracebacks in exception occurrences when the target supports it.
8085 This is the default with the zero cost exception mechanism.
8087 @c The following may get moved to an appendix
8088 This option is currently supported on the following targets:
8089 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8091 See also the packages @code{GNAT.Traceback} and
8092 @code{GNAT.Traceback.Symbolic} for more information.
8094 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8095 @command{gcc} option.
8098 @item ^-F^/FORCE_ELABS_FLAGS^
8099 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8100 Force the checks of elaboration flags. @command{gnatbind} does not normally
8101 generate checks of elaboration flags for the main executable, except when
8102 a Stand-Alone Library is used. However, there are cases when this cannot be
8103 detected by gnatbind. An example is importing an interface of a Stand-Alone
8104 Library through a pragma Import and only specifying through a linker switch
8105 this Stand-Alone Library. This switch is used to guarantee that elaboration
8106 flag checks are generated.
8109 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8110 Output usage (help) information
8113 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8114 Specify directory to be searched for source and ALI files.
8116 @item ^-I-^/NOCURRENT_DIRECTORY^
8117 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8118 Do not look for sources in the current directory where @code{gnatbind} was
8119 invoked, and do not look for ALI files in the directory containing the
8120 ALI file named in the @code{gnatbind} command line.
8122 @item ^-l^/ORDER_OF_ELABORATION^
8123 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8124 Output chosen elaboration order.
8126 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8127 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8128 Bind the units for library building. In this case the adainit and
8129 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8130 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8131 ^@var{xxx}final^@var{XXX}FINAL^.
8132 Implies ^-n^/NOCOMPILE^.
8134 (@xref{GNAT and Libraries}, for more details.)
8137 On OpenVMS, these init and final procedures are exported in uppercase
8138 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8139 the init procedure will be "TOTOINIT" and the exported name of the final
8140 procedure will be "TOTOFINAL".
8143 @item ^-Mxyz^/RENAME_MAIN=xyz^
8144 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8145 Rename generated main program from main to xyz. This option is
8146 supported on cross environments only.
8148 @item ^-m^/ERROR_LIMIT=^@var{n}
8149 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8150 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8151 in the range 1..999999. The default value if no switch is
8152 given is 9999. If the number of warnings reaches this limit, then a
8153 message is output and further warnings are suppressed, the bind
8154 continues in this case. If the number of errors reaches this
8155 limit, then a message is output and the bind is abandoned.
8156 A value of zero means that no limit is enforced. The equal
8160 Furthermore, under Windows, the sources pointed to by the libraries path
8161 set in the registry are not searched for.
8165 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8169 @cindex @option{-nostdinc} (@command{gnatbind})
8170 Do not look for sources in the system default directory.
8173 @cindex @option{-nostdlib} (@command{gnatbind})
8174 Do not look for library files in the system default directory.
8176 @item --RTS=@var{rts-path}
8177 @cindex @option{--RTS} (@code{gnatbind})
8178 Specifies the default location of the runtime library. Same meaning as the
8179 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8181 @item ^-o ^/OUTPUT=^@var{file}
8182 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8183 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8184 Note that if this option is used, then linking must be done manually,
8185 gnatlink cannot be used.
8187 @item ^-O^/OBJECT_LIST^@r{[=}@var{filename}@r{]}
8188 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8189 Output object list (to standard output or to the named file).
8191 @item ^-p^/PESSIMISTIC_ELABORATION^
8192 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8193 Pessimistic (worst-case) elaboration order
8196 @cindex @option{^-R^-R^} (@command{gnatbind})
8197 Output closure source list.
8199 @item ^-s^/READ_SOURCES=ALL^
8200 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8201 Require all source files to be present.
8203 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8204 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8205 Specifies the value to be used when detecting uninitialized scalar
8206 objects with pragma Initialize_Scalars.
8207 The @var{xxx} ^string specified with the switch^option^ may be either
8209 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8210 @item ``@option{^lo^LOW^}'' for the lowest possible value
8211 @item ``@option{^hi^HIGH^}'' for the highest possible value
8212 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8213 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8216 In addition, you can specify @option{-Sev} to indicate that the value is
8217 to be set at run time. In this case, the program will look for an environment
8218 @cindex GNAT_INIT_SCALARS
8219 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8220 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8221 If no environment variable is found, or if it does not have a valid value,
8222 then the default is @option{in} (invalid values).
8226 @cindex @option{-static} (@code{gnatbind})
8227 Link against a static GNAT run time.
8230 @cindex @option{-shared} (@code{gnatbind})
8231 Link against a shared GNAT run time when available.
8234 @item ^-t^/NOTIME_STAMP_CHECK^
8235 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8236 Tolerate time stamp and other consistency errors
8238 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8239 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8240 Set the time slice value to @var{n} milliseconds. If the system supports
8241 the specification of a specific time slice value, then the indicated value
8242 is used. If the system does not support specific time slice values, but
8243 does support some general notion of round-robin scheduling, then any
8244 nonzero value will activate round-robin scheduling.
8246 A value of zero is treated specially. It turns off time
8247 slicing, and in addition, indicates to the tasking run time that the
8248 semantics should match as closely as possible the Annex D
8249 requirements of the Ada RM, and in particular sets the default
8250 scheduling policy to @code{FIFO_Within_Priorities}.
8252 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8253 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8254 Enable dynamic stack usage, with @var{n} results stored and displayed
8255 at program termination. A result is generated when a task
8256 terminates. Results that can't be stored are displayed on the fly, at
8257 task termination. This option is currently not supported on Itanium
8258 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8260 @item ^-v^/REPORT_ERRORS=VERBOSE^
8261 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8262 Verbose mode. Write error messages, header, summary output to
8267 @cindex @option{-w} (@code{gnatbind})
8268 Warning mode (@var{x}=s/e for suppress/treat as error)
8272 @item /WARNINGS=NORMAL
8273 @cindex @option{/WARNINGS} (@code{gnatbind})
8274 Normal warnings mode. Warnings are issued but ignored
8276 @item /WARNINGS=SUPPRESS
8277 @cindex @option{/WARNINGS} (@code{gnatbind})
8278 All warning messages are suppressed
8280 @item /WARNINGS=ERROR
8281 @cindex @option{/WARNINGS} (@code{gnatbind})
8282 Warning messages are treated as fatal errors
8285 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8286 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8287 Override default wide character encoding for standard Text_IO files.
8289 @item ^-x^/READ_SOURCES=NONE^
8290 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8291 Exclude source files (check object consistency only).
8294 @item /READ_SOURCES=AVAILABLE
8295 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8296 Default mode, in which sources are checked for consistency only if
8300 @item ^-y^/ENABLE_LEAP_SECONDS^
8301 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8302 Enable leap seconds support in @code{Ada.Calendar} and its children.
8304 @item ^-z^/ZERO_MAIN^
8305 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8311 You may obtain this listing of switches by running @code{gnatbind} with
8315 @node Consistency-Checking Modes
8316 @subsection Consistency-Checking Modes
8319 As described earlier, by default @code{gnatbind} checks
8320 that object files are consistent with one another and are consistent
8321 with any source files it can locate. The following switches control binder
8326 @item ^-s^/READ_SOURCES=ALL^
8327 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8328 Require source files to be present. In this mode, the binder must be
8329 able to locate all source files that are referenced, in order to check
8330 their consistency. In normal mode, if a source file cannot be located it
8331 is simply ignored. If you specify this switch, a missing source
8334 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8335 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8336 Override default wide character encoding for standard Text_IO files.
8337 Normally the default wide character encoding method used for standard
8338 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8339 the main source input (see description of switch
8340 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8341 use of this switch for the binder (which has the same set of
8342 possible arguments) overrides this default as specified.
8344 @item ^-x^/READ_SOURCES=NONE^
8345 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8346 Exclude source files. In this mode, the binder only checks that ALI
8347 files are consistent with one another. Source files are not accessed.
8348 The binder runs faster in this mode, and there is still a guarantee that
8349 the resulting program is self-consistent.
8350 If a source file has been edited since it was last compiled, and you
8351 specify this switch, the binder will not detect that the object
8352 file is out of date with respect to the source file. Note that this is the
8353 mode that is automatically used by @command{gnatmake} because in this
8354 case the checking against sources has already been performed by
8355 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8358 @item /READ_SOURCES=AVAILABLE
8359 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8360 This is the default mode in which source files are checked if they are
8361 available, and ignored if they are not available.
8365 @node Binder Error Message Control
8366 @subsection Binder Error Message Control
8369 The following switches provide control over the generation of error
8370 messages from the binder:
8374 @item ^-v^/REPORT_ERRORS=VERBOSE^
8375 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8376 Verbose mode. In the normal mode, brief error messages are generated to
8377 @file{stderr}. If this switch is present, a header is written
8378 to @file{stdout} and any error messages are directed to @file{stdout}.
8379 All that is written to @file{stderr} is a brief summary message.
8381 @item ^-b^/REPORT_ERRORS=BRIEF^
8382 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8383 Generate brief error messages to @file{stderr} even if verbose mode is
8384 specified. This is relevant only when used with the
8385 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8389 @cindex @option{-m} (@code{gnatbind})
8390 Limits the number of error messages to @var{n}, a decimal integer in the
8391 range 1-999. The binder terminates immediately if this limit is reached.
8394 @cindex @option{-M} (@code{gnatbind})
8395 Renames the generated main program from @code{main} to @code{xxx}.
8396 This is useful in the case of some cross-building environments, where
8397 the actual main program is separate from the one generated
8401 @item ^-ws^/WARNINGS=SUPPRESS^
8402 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8404 Suppress all warning messages.
8406 @item ^-we^/WARNINGS=ERROR^
8407 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8408 Treat any warning messages as fatal errors.
8411 @item /WARNINGS=NORMAL
8412 Standard mode with warnings generated, but warnings do not get treated
8416 @item ^-t^/NOTIME_STAMP_CHECK^
8417 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8418 @cindex Time stamp checks, in binder
8419 @cindex Binder consistency checks
8420 @cindex Consistency checks, in binder
8421 The binder performs a number of consistency checks including:
8425 Check that time stamps of a given source unit are consistent
8427 Check that checksums of a given source unit are consistent
8429 Check that consistent versions of @code{GNAT} were used for compilation
8431 Check consistency of configuration pragmas as required
8435 Normally failure of such checks, in accordance with the consistency
8436 requirements of the Ada Reference Manual, causes error messages to be
8437 generated which abort the binder and prevent the output of a binder
8438 file and subsequent link to obtain an executable.
8440 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8441 into warnings, so that
8442 binding and linking can continue to completion even in the presence of such
8443 errors. The result may be a failed link (due to missing symbols), or a
8444 non-functional executable which has undefined semantics.
8445 @emph{This means that
8446 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8450 @node Elaboration Control
8451 @subsection Elaboration Control
8454 The following switches provide additional control over the elaboration
8455 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8458 @item ^-p^/PESSIMISTIC_ELABORATION^
8459 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8460 Normally the binder attempts to choose an elaboration order that is
8461 likely to minimize the likelihood of an elaboration order error resulting
8462 in raising a @code{Program_Error} exception. This switch reverses the
8463 action of the binder, and requests that it deliberately choose an order
8464 that is likely to maximize the likelihood of an elaboration error.
8465 This is useful in ensuring portability and avoiding dependence on
8466 accidental fortuitous elaboration ordering.
8468 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8470 elaboration checking is used (@option{-gnatE} switch used for compilation).
8471 This is because in the default static elaboration mode, all necessary
8472 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8473 These implicit pragmas are still respected by the binder in
8474 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8475 safe elaboration order is assured.
8478 @node Output Control
8479 @subsection Output Control
8482 The following switches allow additional control over the output
8483 generated by the binder.
8488 @item ^-c^/NOOUTPUT^
8489 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8490 Check only. Do not generate the binder output file. In this mode the
8491 binder performs all error checks but does not generate an output file.
8493 @item ^-e^/ELABORATION_DEPENDENCIES^
8494 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8495 Output complete list of elaboration-order dependencies, showing the
8496 reason for each dependency. This output can be rather extensive but may
8497 be useful in diagnosing problems with elaboration order. The output is
8498 written to @file{stdout}.
8501 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8502 Output usage information. The output is written to @file{stdout}.
8504 @item ^-K^/LINKER_OPTION_LIST^
8505 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8506 Output linker options to @file{stdout}. Includes library search paths,
8507 contents of pragmas Ident and Linker_Options, and libraries added
8510 @item ^-l^/ORDER_OF_ELABORATION^
8511 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8512 Output chosen elaboration order. The output is written to @file{stdout}.
8514 @item ^-O^/OBJECT_LIST^
8515 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8516 Output full names of all the object files that must be linked to provide
8517 the Ada component of the program. The output is written to @file{stdout}.
8518 This list includes the files explicitly supplied and referenced by the user
8519 as well as implicitly referenced run-time unit files. The latter are
8520 omitted if the corresponding units reside in shared libraries. The
8521 directory names for the run-time units depend on the system configuration.
8523 @item ^-o ^/OUTPUT=^@var{file}
8524 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8525 Set name of output file to @var{file} instead of the normal
8526 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8527 binder generated body filename.
8528 Note that if this option is used, then linking must be done manually.
8529 It is not possible to use gnatlink in this case, since it cannot locate
8532 @item ^-r^/RESTRICTION_LIST^
8533 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8534 Generate list of @code{pragma Restrictions} that could be applied to
8535 the current unit. This is useful for code audit purposes, and also may
8536 be used to improve code generation in some cases.
8540 @node Binding with Non-Ada Main Programs
8541 @subsection Binding with Non-Ada Main Programs
8544 In our description so far we have assumed that the main
8545 program is in Ada, and that the task of the binder is to generate a
8546 corresponding function @code{main} that invokes this Ada main
8547 program. GNAT also supports the building of executable programs where
8548 the main program is not in Ada, but some of the called routines are
8549 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8550 The following switch is used in this situation:
8554 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8555 No main program. The main program is not in Ada.
8559 In this case, most of the functions of the binder are still required,
8560 but instead of generating a main program, the binder generates a file
8561 containing the following callable routines:
8566 You must call this routine to initialize the Ada part of the program by
8567 calling the necessary elaboration routines. A call to @code{adainit} is
8568 required before the first call to an Ada subprogram.
8570 Note that it is assumed that the basic execution environment must be setup
8571 to be appropriate for Ada execution at the point where the first Ada
8572 subprogram is called. In particular, if the Ada code will do any
8573 floating-point operations, then the FPU must be setup in an appropriate
8574 manner. For the case of the x86, for example, full precision mode is
8575 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8576 that the FPU is in the right state.
8580 You must call this routine to perform any library-level finalization
8581 required by the Ada subprograms. A call to @code{adafinal} is required
8582 after the last call to an Ada subprogram, and before the program
8587 If the @option{^-n^/NOMAIN^} switch
8588 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8589 @cindex Binder, multiple input files
8590 is given, more than one ALI file may appear on
8591 the command line for @code{gnatbind}. The normal @dfn{closure}
8592 calculation is performed for each of the specified units. Calculating
8593 the closure means finding out the set of units involved by tracing
8594 @code{with} references. The reason it is necessary to be able to
8595 specify more than one ALI file is that a given program may invoke two or
8596 more quite separate groups of Ada units.
8598 The binder takes the name of its output file from the last specified ALI
8599 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8600 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8601 The output is an Ada unit in source form that can be compiled with GNAT.
8602 This compilation occurs automatically as part of the @command{gnatlink}
8605 Currently the GNAT run time requires a FPU using 80 bits mode
8606 precision. Under targets where this is not the default it is required to
8607 call GNAT.Float_Control.Reset before using floating point numbers (this
8608 include float computation, float input and output) in the Ada code. A
8609 side effect is that this could be the wrong mode for the foreign code
8610 where floating point computation could be broken after this call.
8612 @node Binding Programs with No Main Subprogram
8613 @subsection Binding Programs with No Main Subprogram
8616 It is possible to have an Ada program which does not have a main
8617 subprogram. This program will call the elaboration routines of all the
8618 packages, then the finalization routines.
8620 The following switch is used to bind programs organized in this manner:
8623 @item ^-z^/ZERO_MAIN^
8624 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8625 Normally the binder checks that the unit name given on the command line
8626 corresponds to a suitable main subprogram. When this switch is used,
8627 a list of ALI files can be given, and the execution of the program
8628 consists of elaboration of these units in an appropriate order. Note
8629 that the default wide character encoding method for standard Text_IO
8630 files is always set to Brackets if this switch is set (you can use
8632 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8635 @node Command-Line Access
8636 @section Command-Line Access
8639 The package @code{Ada.Command_Line} provides access to the command-line
8640 arguments and program name. In order for this interface to operate
8641 correctly, the two variables
8653 are declared in one of the GNAT library routines. These variables must
8654 be set from the actual @code{argc} and @code{argv} values passed to the
8655 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8656 generates the C main program to automatically set these variables.
8657 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8658 set these variables. If they are not set, the procedures in
8659 @code{Ada.Command_Line} will not be available, and any attempt to use
8660 them will raise @code{Constraint_Error}. If command line access is
8661 required, your main program must set @code{gnat_argc} and
8662 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8665 @node Search Paths for gnatbind
8666 @section Search Paths for @code{gnatbind}
8669 The binder takes the name of an ALI file as its argument and needs to
8670 locate source files as well as other ALI files to verify object consistency.
8672 For source files, it follows exactly the same search rules as @command{gcc}
8673 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8674 directories searched are:
8678 The directory containing the ALI file named in the command line, unless
8679 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8682 All directories specified by @option{^-I^/SEARCH^}
8683 switches on the @code{gnatbind}
8684 command line, in the order given.
8687 @findex ADA_PRJ_OBJECTS_FILE
8688 Each of the directories listed in the text file whose name is given
8689 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8692 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8693 driver when project files are used. It should not normally be set
8697 @findex ADA_OBJECTS_PATH
8698 Each of the directories listed in the value of the
8699 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8701 Construct this value
8702 exactly as the @env{PATH} environment variable: a list of directory
8703 names separated by colons (semicolons when working with the NT version
8707 Normally, define this value as a logical name containing a comma separated
8708 list of directory names.
8710 This variable can also be defined by means of an environment string
8711 (an argument to the HP C exec* set of functions).
8715 DEFINE ANOTHER_PATH FOO:[BAG]
8716 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8719 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8720 first, followed by the standard Ada
8721 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8722 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8723 (Text_IO, Sequential_IO, etc)
8724 instead of the standard Ada packages. Thus, in order to get the standard Ada
8725 packages by default, ADA_OBJECTS_PATH must be redefined.
8729 The content of the @file{ada_object_path} file which is part of the GNAT
8730 installation tree and is used to store standard libraries such as the
8731 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8734 @ref{Installing a library}
8739 In the binder the switch @option{^-I^/SEARCH^}
8740 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8741 is used to specify both source and
8742 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8743 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8744 instead if you want to specify
8745 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8746 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8747 if you want to specify library paths
8748 only. This means that for the binder
8749 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8750 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8751 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8752 The binder generates the bind file (a C language source file) in the
8753 current working directory.
8759 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8760 children make up the GNAT Run-Time Library, together with the package
8761 GNAT and its children, which contain a set of useful additional
8762 library functions provided by GNAT. The sources for these units are
8763 needed by the compiler and are kept together in one directory. The ALI
8764 files and object files generated by compiling the RTL are needed by the
8765 binder and the linker and are kept together in one directory, typically
8766 different from the directory containing the sources. In a normal
8767 installation, you need not specify these directory names when compiling
8768 or binding. Either the environment variables or the built-in defaults
8769 cause these files to be found.
8771 Besides simplifying access to the RTL, a major use of search paths is
8772 in compiling sources from multiple directories. This can make
8773 development environments much more flexible.
8775 @node Examples of gnatbind Usage
8776 @section Examples of @code{gnatbind} Usage
8779 This section contains a number of examples of using the GNAT binding
8780 utility @code{gnatbind}.
8783 @item gnatbind hello
8784 The main program @code{Hello} (source program in @file{hello.adb}) is
8785 bound using the standard switch settings. The generated main program is
8786 @file{b~hello.adb}. This is the normal, default use of the binder.
8789 @item gnatbind hello -o mainprog.adb
8792 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8794 The main program @code{Hello} (source program in @file{hello.adb}) is
8795 bound using the standard switch settings. The generated main program is
8796 @file{mainprog.adb} with the associated spec in
8797 @file{mainprog.ads}. Note that you must specify the body here not the
8798 spec. Note that if this option is used, then linking must be done manually,
8799 since gnatlink will not be able to find the generated file.
8802 @c ------------------------------------
8803 @node Linking Using gnatlink
8804 @chapter Linking Using @command{gnatlink}
8805 @c ------------------------------------
8809 This chapter discusses @command{gnatlink}, a tool that links
8810 an Ada program and builds an executable file. This utility
8811 invokes the system linker ^(via the @command{gcc} command)^^
8812 with a correct list of object files and library references.
8813 @command{gnatlink} automatically determines the list of files and
8814 references for the Ada part of a program. It uses the binder file
8815 generated by the @command{gnatbind} to determine this list.
8817 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8818 driver (see @ref{The GNAT Driver and Project Files}).
8821 * Running gnatlink::
8822 * Switches for gnatlink::
8825 @node Running gnatlink
8826 @section Running @command{gnatlink}
8829 The form of the @command{gnatlink} command is
8832 @c $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8833 @c @ovar{non-Ada objects} @ovar{linker options}
8834 @c Expanding @ovar macro inline (explanation in macro def comments)
8835 $ gnatlink @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]}
8836 @r{[}@var{non-Ada objects}@r{]} @r{[}@var{linker options}@r{]}
8841 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8843 or linker options) may be in any order, provided that no non-Ada object may
8844 be mistaken for a main @file{ALI} file.
8845 Any file name @file{F} without the @file{.ali}
8846 extension will be taken as the main @file{ALI} file if a file exists
8847 whose name is the concatenation of @file{F} and @file{.ali}.
8850 @file{@var{mainprog}.ali} references the ALI file of the main program.
8851 The @file{.ali} extension of this file can be omitted. From this
8852 reference, @command{gnatlink} locates the corresponding binder file
8853 @file{b~@var{mainprog}.adb} and, using the information in this file along
8854 with the list of non-Ada objects and linker options, constructs a
8855 linker command file to create the executable.
8857 The arguments other than the @command{gnatlink} switches and the main
8858 @file{ALI} file are passed to the linker uninterpreted.
8859 They typically include the names of
8860 object files for units written in other languages than Ada and any library
8861 references required to resolve references in any of these foreign language
8862 units, or in @code{Import} pragmas in any Ada units.
8864 @var{linker options} is an optional list of linker specific
8866 The default linker called by gnatlink is @command{gcc} which in
8867 turn calls the appropriate system linker.
8868 Standard options for the linker such as @option{-lmy_lib} or
8869 @option{-Ldir} can be added as is.
8870 For options that are not recognized by
8871 @command{gcc} as linker options, use the @command{gcc} switches
8872 @option{-Xlinker} or @option{-Wl,}.
8873 Refer to the GCC documentation for
8874 details. Here is an example showing how to generate a linker map:
8877 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8880 Using @var{linker options} it is possible to set the program stack and
8883 See @ref{Setting Stack Size from gnatlink} and
8884 @ref{Setting Heap Size from gnatlink}.
8887 @command{gnatlink} determines the list of objects required by the Ada
8888 program and prepends them to the list of objects passed to the linker.
8889 @command{gnatlink} also gathers any arguments set by the use of
8890 @code{pragma Linker_Options} and adds them to the list of arguments
8891 presented to the linker.
8894 @command{gnatlink} accepts the following types of extra files on the command
8895 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8896 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8897 handled according to their extension.
8900 @node Switches for gnatlink
8901 @section Switches for @command{gnatlink}
8904 The following switches are available with the @command{gnatlink} utility:
8910 @cindex @option{--version} @command{gnatlink}
8911 Display Copyright and version, then exit disregarding all other options.
8914 @cindex @option{--help} @command{gnatlink}
8915 If @option{--version} was not used, display usage, then exit disregarding
8918 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8919 @cindex Command line length
8920 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8921 On some targets, the command line length is limited, and @command{gnatlink}
8922 will generate a separate file for the linker if the list of object files
8924 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8925 to be generated even if
8926 the limit is not exceeded. This is useful in some cases to deal with
8927 special situations where the command line length is exceeded.
8930 @cindex Debugging information, including
8931 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8932 The option to include debugging information causes the Ada bind file (in
8933 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8934 @option{^-g^/DEBUG^}.
8935 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8936 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8937 Without @option{^-g^/DEBUG^}, the binder removes these files by
8938 default. The same procedure apply if a C bind file was generated using
8939 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8940 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8942 @item ^-n^/NOCOMPILE^
8943 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8944 Do not compile the file generated by the binder. This may be used when
8945 a link is rerun with different options, but there is no need to recompile
8949 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8950 Causes additional information to be output, including a full list of the
8951 included object files. This switch option is most useful when you want
8952 to see what set of object files are being used in the link step.
8954 @item ^-v -v^/VERBOSE/VERBOSE^
8955 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8956 Very verbose mode. Requests that the compiler operate in verbose mode when
8957 it compiles the binder file, and that the system linker run in verbose mode.
8959 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8960 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8961 @var{exec-name} specifies an alternate name for the generated
8962 executable program. If this switch is omitted, the executable has the same
8963 name as the main unit. For example, @code{gnatlink try.ali} creates
8964 an executable called @file{^try^TRY.EXE^}.
8967 @item -b @var{target}
8968 @cindex @option{-b} (@command{gnatlink})
8969 Compile your program to run on @var{target}, which is the name of a
8970 system configuration. You must have a GNAT cross-compiler built if
8971 @var{target} is not the same as your host system.
8974 @cindex @option{-B} (@command{gnatlink})
8975 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8976 from @var{dir} instead of the default location. Only use this switch
8977 when multiple versions of the GNAT compiler are available.
8978 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8979 for further details. You would normally use the @option{-b} or
8980 @option{-V} switch instead.
8982 @item --GCC=@var{compiler_name}
8983 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8984 Program used for compiling the binder file. The default is
8985 @command{gcc}. You need to use quotes around @var{compiler_name} if
8986 @code{compiler_name} contains spaces or other separator characters.
8987 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8988 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8989 inserted after your command name. Thus in the above example the compiler
8990 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8991 A limitation of this syntax is that the name and path name of the executable
8992 itself must not include any embedded spaces. If the compiler executable is
8993 different from the default one (gcc or <prefix>-gcc), then the back-end
8994 switches in the ALI file are not used to compile the binder generated source.
8995 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8996 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8997 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8998 is taken into account. However, all the additional switches are also taken
9000 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9001 @option{--GCC="bar -x -y -z -t"}.
9003 @item --LINK=@var{name}
9004 @cindex @option{--LINK=} (@command{gnatlink})
9005 @var{name} is the name of the linker to be invoked. This is especially
9006 useful in mixed language programs since languages such as C++ require
9007 their own linker to be used. When this switch is omitted, the default
9008 name for the linker is @command{gcc}. When this switch is used, the
9009 specified linker is called instead of @command{gcc} with exactly the same
9010 parameters that would have been passed to @command{gcc} so if the desired
9011 linker requires different parameters it is necessary to use a wrapper
9012 script that massages the parameters before invoking the real linker. It
9013 may be useful to control the exact invocation by using the verbose
9019 @item /DEBUG=TRACEBACK
9020 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9021 This qualifier causes sufficient information to be included in the
9022 executable file to allow a traceback, but does not include the full
9023 symbol information needed by the debugger.
9025 @item /IDENTIFICATION="<string>"
9026 @code{"<string>"} specifies the string to be stored in the image file
9027 identification field in the image header.
9028 It overrides any pragma @code{Ident} specified string.
9030 @item /NOINHIBIT-EXEC
9031 Generate the executable file even if there are linker warnings.
9033 @item /NOSTART_FILES
9034 Don't link in the object file containing the ``main'' transfer address.
9035 Used when linking with a foreign language main program compiled with an
9039 Prefer linking with object libraries over sharable images, even without
9045 @node The GNAT Make Program gnatmake
9046 @chapter The GNAT Make Program @command{gnatmake}
9050 * Running gnatmake::
9051 * Switches for gnatmake::
9052 * Mode Switches for gnatmake::
9053 * Notes on the Command Line::
9054 * How gnatmake Works::
9055 * Examples of gnatmake Usage::
9058 A typical development cycle when working on an Ada program consists of
9059 the following steps:
9063 Edit some sources to fix bugs.
9069 Compile all sources affected.
9079 The third step can be tricky, because not only do the modified files
9080 @cindex Dependency rules
9081 have to be compiled, but any files depending on these files must also be
9082 recompiled. The dependency rules in Ada can be quite complex, especially
9083 in the presence of overloading, @code{use} clauses, generics and inlined
9086 @command{gnatmake} automatically takes care of the third and fourth steps
9087 of this process. It determines which sources need to be compiled,
9088 compiles them, and binds and links the resulting object files.
9090 Unlike some other Ada make programs, the dependencies are always
9091 accurately recomputed from the new sources. The source based approach of
9092 the GNAT compilation model makes this possible. This means that if
9093 changes to the source program cause corresponding changes in
9094 dependencies, they will always be tracked exactly correctly by
9097 @node Running gnatmake
9098 @section Running @command{gnatmake}
9101 The usual form of the @command{gnatmake} command is
9104 @c $ gnatmake @ovar{switches} @var{file_name}
9105 @c @ovar{file_names} @ovar{mode_switches}
9106 @c Expanding @ovar macro inline (explanation in macro def comments)
9107 $ gnatmake @r{[}@var{switches}@r{]} @var{file_name}
9108 @r{[}@var{file_names}@r{]} @r{[}@var{mode_switches}@r{]}
9112 The only required argument is one @var{file_name}, which specifies
9113 a compilation unit that is a main program. Several @var{file_names} can be
9114 specified: this will result in several executables being built.
9115 If @code{switches} are present, they can be placed before the first
9116 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9117 If @var{mode_switches} are present, they must always be placed after
9118 the last @var{file_name} and all @code{switches}.
9120 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9121 extension may be omitted from the @var{file_name} arguments. However, if
9122 you are using non-standard extensions, then it is required that the
9123 extension be given. A relative or absolute directory path can be
9124 specified in a @var{file_name}, in which case, the input source file will
9125 be searched for in the specified directory only. Otherwise, the input
9126 source file will first be searched in the directory where
9127 @command{gnatmake} was invoked and if it is not found, it will be search on
9128 the source path of the compiler as described in
9129 @ref{Search Paths and the Run-Time Library (RTL)}.
9131 All @command{gnatmake} output (except when you specify
9132 @option{^-M^/DEPENDENCIES_LIST^}) is to
9133 @file{stderr}. The output produced by the
9134 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9137 @node Switches for gnatmake
9138 @section Switches for @command{gnatmake}
9141 You may specify any of the following switches to @command{gnatmake}:
9147 @cindex @option{--version} @command{gnatmake}
9148 Display Copyright and version, then exit disregarding all other options.
9151 @cindex @option{--help} @command{gnatmake}
9152 If @option{--version} was not used, display usage, then exit disregarding
9156 @item --GCC=@var{compiler_name}
9157 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9158 Program used for compiling. The default is `@command{gcc}'. You need to use
9159 quotes around @var{compiler_name} if @code{compiler_name} contains
9160 spaces or other separator characters. As an example @option{--GCC="foo -x
9161 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9162 compiler. A limitation of this syntax is that the name and path name of
9163 the executable itself must not include any embedded spaces. Note that
9164 switch @option{-c} is always inserted after your command name. Thus in the
9165 above example the compiler command that will be used by @command{gnatmake}
9166 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9167 used, only the last @var{compiler_name} is taken into account. However,
9168 all the additional switches are also taken into account. Thus,
9169 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9170 @option{--GCC="bar -x -y -z -t"}.
9172 @item --GNATBIND=@var{binder_name}
9173 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9174 Program used for binding. The default is `@code{gnatbind}'. You need to
9175 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9176 or other separator characters. As an example @option{--GNATBIND="bar -x
9177 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9178 binder. Binder switches that are normally appended by @command{gnatmake}
9179 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9180 A limitation of this syntax is that the name and path name of the executable
9181 itself must not include any embedded spaces.
9183 @item --GNATLINK=@var{linker_name}
9184 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9185 Program used for linking. The default is `@command{gnatlink}'. You need to
9186 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9187 or other separator characters. As an example @option{--GNATLINK="lan -x
9188 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9189 linker. Linker switches that are normally appended by @command{gnatmake} to
9190 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9191 A limitation of this syntax is that the name and path name of the executable
9192 itself must not include any embedded spaces.
9196 @item ^--subdirs^/SUBDIRS^=subdir
9197 Actual object directory of each project file is the subdirectory subdir of the
9198 object directory specified or defauted in the project file.
9200 @item ^--unchecked-shared-lib-imports^/UNCHECKED_SHARED_LIB_IMPORTS^
9201 By default, shared library projects are not allowed to import static library
9202 projects. When this switch is used on the command line, this restriction is
9205 @item ^-a^/ALL_FILES^
9206 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9207 Consider all files in the make process, even the GNAT internal system
9208 files (for example, the predefined Ada library files), as well as any
9209 locked files. Locked files are files whose ALI file is write-protected.
9211 @command{gnatmake} does not check these files,
9212 because the assumption is that the GNAT internal files are properly up
9213 to date, and also that any write protected ALI files have been properly
9214 installed. Note that if there is an installation problem, such that one
9215 of these files is not up to date, it will be properly caught by the
9217 You may have to specify this switch if you are working on GNAT
9218 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9219 in conjunction with @option{^-f^/FORCE_COMPILE^}
9220 if you need to recompile an entire application,
9221 including run-time files, using special configuration pragmas,
9222 such as a @code{Normalize_Scalars} pragma.
9225 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9228 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9231 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9234 @item ^-b^/ACTIONS=BIND^
9235 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9236 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9237 compilation and binding, but no link.
9238 Can be combined with @option{^-l^/ACTIONS=LINK^}
9239 to do binding and linking. When not combined with
9240 @option{^-c^/ACTIONS=COMPILE^}
9241 all the units in the closure of the main program must have been previously
9242 compiled and must be up to date. The root unit specified by @var{file_name}
9243 may be given without extension, with the source extension or, if no GNAT
9244 Project File is specified, with the ALI file extension.
9246 @item ^-c^/ACTIONS=COMPILE^
9247 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9248 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9249 is also specified. Do not perform linking, except if both
9250 @option{^-b^/ACTIONS=BIND^} and
9251 @option{^-l^/ACTIONS=LINK^} are also specified.
9252 If the root unit specified by @var{file_name} is not a main unit, this is the
9253 default. Otherwise @command{gnatmake} will attempt binding and linking
9254 unless all objects are up to date and the executable is more recent than
9258 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9259 Use a temporary mapping file. A mapping file is a way to communicate
9260 to the compiler two mappings: from unit names to file names (without
9261 any directory information) and from file names to path names (with
9262 full directory information). A mapping file can make the compiler's
9263 file searches faster, especially if there are many source directories,
9264 or the sources are read over a slow network connection. If
9265 @option{^-P^/PROJECT_FILE^} is used, a mapping file is always used, so
9266 @option{^-C^/MAPPING^} is unnecessary; in this case the mapping file
9267 is initially populated based on the project file. If
9268 @option{^-C^/MAPPING^} is used without
9269 @option{^-P^/PROJECT_FILE^},
9270 the mapping file is initially empty. Each invocation of the compiler
9271 will add any newly accessed sources to the mapping file.
9273 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9274 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9275 Use a specific mapping file. The file, specified as a path name (absolute or
9276 relative) by this switch, should already exist, otherwise the switch is
9277 ineffective. The specified mapping file will be communicated to the compiler.
9278 This switch is not compatible with a project file
9279 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9280 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9282 @item ^-d^/DISPLAY_PROGRESS^
9283 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9284 Display progress for each source, up to date or not, as a single line
9287 completed x out of y (zz%)
9290 If the file needs to be compiled this is displayed after the invocation of
9291 the compiler. These lines are displayed even in quiet output mode.
9293 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9294 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9295 Put all object files and ALI file in directory @var{dir}.
9296 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9297 and ALI files go in the current working directory.
9299 This switch cannot be used when using a project file.
9303 @cindex @option{-eL} (@command{gnatmake})
9304 @cindex symbolic links
9305 Follow all symbolic links when processing project files.
9306 This should be used if your project uses symbolic links for files or
9307 directories, but is not needed in other cases.
9309 @cindex naming scheme
9310 This also assumes that no directory matches the naming scheme for files (for
9311 instance that you do not have a directory called "sources.ads" when using the
9312 default GNAT naming scheme).
9314 When you do not have to use this switch (ie by default), gnatmake is able to
9315 save a lot of system calls (several per source file and object file), which
9316 can result in a significant speed up to load and manipulate a project file,
9317 especially when using source files from a remote system.
9321 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9322 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9323 Output the commands for the compiler, the binder and the linker
9324 on ^standard output^SYS$OUTPUT^,
9325 instead of ^standard error^SYS$ERROR^.
9327 @item ^-f^/FORCE_COMPILE^
9328 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9329 Force recompilations. Recompile all sources, even though some object
9330 files may be up to date, but don't recompile predefined or GNAT internal
9331 files or locked files (files with a write-protected ALI file),
9332 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9334 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9335 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9336 When using project files, if some errors or warnings are detected during
9337 parsing and verbose mode is not in effect (no use of switch
9338 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9339 file, rather than its simple file name.
9342 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9343 Enable debugging. This switch is simply passed to the compiler and to the
9346 @item ^-i^/IN_PLACE^
9347 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9348 In normal mode, @command{gnatmake} compiles all object files and ALI files
9349 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9350 then instead object files and ALI files that already exist are overwritten
9351 in place. This means that once a large project is organized into separate
9352 directories in the desired manner, then @command{gnatmake} will automatically
9353 maintain and update this organization. If no ALI files are found on the
9354 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9355 the new object and ALI files are created in the
9356 directory containing the source being compiled. If another organization
9357 is desired, where objects and sources are kept in different directories,
9358 a useful technique is to create dummy ALI files in the desired directories.
9359 When detecting such a dummy file, @command{gnatmake} will be forced to
9360 recompile the corresponding source file, and it will be put the resulting
9361 object and ALI files in the directory where it found the dummy file.
9363 @item ^-j^/PROCESSES=^@var{n}
9364 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9365 @cindex Parallel make
9366 Use @var{n} processes to carry out the (re)compilations. On a
9367 multiprocessor machine compilations will occur in parallel. In the
9368 event of compilation errors, messages from various compilations might
9369 get interspersed (but @command{gnatmake} will give you the full ordered
9370 list of failing compiles at the end). If this is problematic, rerun
9371 the make process with n set to 1 to get a clean list of messages.
9373 @item ^-k^/CONTINUE_ON_ERROR^
9374 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9375 Keep going. Continue as much as possible after a compilation error. To
9376 ease the programmer's task in case of compilation errors, the list of
9377 sources for which the compile fails is given when @command{gnatmake}
9380 If @command{gnatmake} is invoked with several @file{file_names} and with this
9381 switch, if there are compilation errors when building an executable,
9382 @command{gnatmake} will not attempt to build the following executables.
9384 @item ^-l^/ACTIONS=LINK^
9385 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9386 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9387 and linking. Linking will not be performed if combined with
9388 @option{^-c^/ACTIONS=COMPILE^}
9389 but not with @option{^-b^/ACTIONS=BIND^}.
9390 When not combined with @option{^-b^/ACTIONS=BIND^}
9391 all the units in the closure of the main program must have been previously
9392 compiled and must be up to date, and the main program needs to have been bound.
9393 The root unit specified by @var{file_name}
9394 may be given without extension, with the source extension or, if no GNAT
9395 Project File is specified, with the ALI file extension.
9397 @item ^-m^/MINIMAL_RECOMPILATION^
9398 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9399 Specify that the minimum necessary amount of recompilations
9400 be performed. In this mode @command{gnatmake} ignores time
9401 stamp differences when the only
9402 modifications to a source file consist in adding/removing comments,
9403 empty lines, spaces or tabs. This means that if you have changed the
9404 comments in a source file or have simply reformatted it, using this
9405 switch will tell @command{gnatmake} not to recompile files that depend on it
9406 (provided other sources on which these files depend have undergone no
9407 semantic modifications). Note that the debugging information may be
9408 out of date with respect to the sources if the @option{-m} switch causes
9409 a compilation to be switched, so the use of this switch represents a
9410 trade-off between compilation time and accurate debugging information.
9412 @item ^-M^/DEPENDENCIES_LIST^
9413 @cindex Dependencies, producing list
9414 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9415 Check if all objects are up to date. If they are, output the object
9416 dependences to @file{stdout} in a form that can be directly exploited in
9417 a @file{Makefile}. By default, each source file is prefixed with its
9418 (relative or absolute) directory name. This name is whatever you
9419 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9420 and @option{^-I^/SEARCH^} switches. If you use
9421 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9422 @option{^-q^/QUIET^}
9423 (see below), only the source file names,
9424 without relative paths, are output. If you just specify the
9425 @option{^-M^/DEPENDENCIES_LIST^}
9426 switch, dependencies of the GNAT internal system files are omitted. This
9427 is typically what you want. If you also specify
9428 the @option{^-a^/ALL_FILES^} switch,
9429 dependencies of the GNAT internal files are also listed. Note that
9430 dependencies of the objects in external Ada libraries (see switch
9431 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9434 @item ^-n^/DO_OBJECT_CHECK^
9435 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9436 Don't compile, bind, or link. Checks if all objects are up to date.
9437 If they are not, the full name of the first file that needs to be
9438 recompiled is printed.
9439 Repeated use of this option, followed by compiling the indicated source
9440 file, will eventually result in recompiling all required units.
9442 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9443 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9444 Output executable name. The name of the final executable program will be
9445 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9446 name for the executable will be the name of the input file in appropriate form
9447 for an executable file on the host system.
9449 This switch cannot be used when invoking @command{gnatmake} with several
9452 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9453 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9454 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9455 automatically missing object directories, library directories and exec
9458 @item ^-P^/PROJECT_FILE=^@var{project}
9459 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9460 Use project file @var{project}. Only one such switch can be used.
9461 @xref{gnatmake and Project Files}.
9464 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9465 Quiet. When this flag is not set, the commands carried out by
9466 @command{gnatmake} are displayed.
9468 @item ^-s^/SWITCH_CHECK/^
9469 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9470 Recompile if compiler switches have changed since last compilation.
9471 All compiler switches but -I and -o are taken into account in the
9473 orders between different ``first letter'' switches are ignored, but
9474 orders between same switches are taken into account. For example,
9475 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9476 is equivalent to @option{-O -g}.
9478 This switch is recommended when Integrated Preprocessing is used.
9481 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9482 Unique. Recompile at most the main files. It implies -c. Combined with
9483 -f, it is equivalent to calling the compiler directly. Note that using
9484 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9485 (@pxref{Project Files and Main Subprograms}).
9487 @item ^-U^/ALL_PROJECTS^
9488 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9489 When used without a project file or with one or several mains on the command
9490 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9491 on the command line, all sources of all project files are checked and compiled
9492 if not up to date, and libraries are rebuilt, if necessary.
9495 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9496 Verbose. Display the reason for all recompilations @command{gnatmake}
9497 decides are necessary, with the highest verbosity level.
9499 @item ^-vl^/LOW_VERBOSITY^
9500 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9501 Verbosity level Low. Display fewer lines than in verbosity Medium.
9503 @item ^-vm^/MEDIUM_VERBOSITY^
9504 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9505 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9507 @item ^-vh^/HIGH_VERBOSITY^
9508 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9509 Verbosity level High. Equivalent to ^-v^/REASONS^.
9511 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9512 Indicate the verbosity of the parsing of GNAT project files.
9513 @xref{Switches Related to Project Files}.
9515 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9516 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9517 Indicate that sources that are not part of any Project File may be compiled.
9518 Normally, when using Project Files, only sources that are part of a Project
9519 File may be compile. When this switch is used, a source outside of all Project
9520 Files may be compiled. The ALI file and the object file will be put in the
9521 object directory of the main Project. The compilation switches used will only
9522 be those specified on the command line. Even when
9523 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9524 command line need to be sources of a project file.
9526 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9527 Indicate that external variable @var{name} has the value @var{value}.
9528 The Project Manager will use this value for occurrences of
9529 @code{external(name)} when parsing the project file.
9530 @xref{Switches Related to Project Files}.
9533 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9534 No main subprogram. Bind and link the program even if the unit name
9535 given on the command line is a package name. The resulting executable
9536 will execute the elaboration routines of the package and its closure,
9537 then the finalization routines.
9542 @item @command{gcc} @asis{switches}
9544 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9545 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9548 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9549 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9550 automatically treated as a compiler switch, and passed on to all
9551 compilations that are carried out.
9556 Source and library search path switches:
9560 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9561 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9562 When looking for source files also look in directory @var{dir}.
9563 The order in which source files search is undertaken is
9564 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9566 @item ^-aL^/SKIP_MISSING=^@var{dir}
9567 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9568 Consider @var{dir} as being an externally provided Ada library.
9569 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9570 files have been located in directory @var{dir}. This allows you to have
9571 missing bodies for the units in @var{dir} and to ignore out of date bodies
9572 for the same units. You still need to specify
9573 the location of the specs for these units by using the switches
9574 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9575 or @option{^-I^/SEARCH=^@var{dir}}.
9576 Note: this switch is provided for compatibility with previous versions
9577 of @command{gnatmake}. The easier method of causing standard libraries
9578 to be excluded from consideration is to write-protect the corresponding
9581 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9582 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9583 When searching for library and object files, look in directory
9584 @var{dir}. The order in which library files are searched is described in
9585 @ref{Search Paths for gnatbind}.
9587 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9588 @cindex Search paths, for @command{gnatmake}
9589 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9590 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9591 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9593 @item ^-I^/SEARCH=^@var{dir}
9594 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9595 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9596 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9598 @item ^-I-^/NOCURRENT_DIRECTORY^
9599 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9600 @cindex Source files, suppressing search
9601 Do not look for source files in the directory containing the source
9602 file named in the command line.
9603 Do not look for ALI or object files in the directory
9604 where @command{gnatmake} was invoked.
9606 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9607 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9608 @cindex Linker libraries
9609 Add directory @var{dir} to the list of directories in which the linker
9610 will search for libraries. This is equivalent to
9611 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9613 Furthermore, under Windows, the sources pointed to by the libraries path
9614 set in the registry are not searched for.
9618 @cindex @option{-nostdinc} (@command{gnatmake})
9619 Do not look for source files in the system default directory.
9622 @cindex @option{-nostdlib} (@command{gnatmake})
9623 Do not look for library files in the system default directory.
9625 @item --RTS=@var{rts-path}
9626 @cindex @option{--RTS} (@command{gnatmake})
9627 Specifies the default location of the runtime library. GNAT looks for the
9629 in the following directories, and stops as soon as a valid runtime is found
9630 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9631 @file{ada_object_path} present):
9634 @item <current directory>/$rts_path
9636 @item <default-search-dir>/$rts_path
9638 @item <default-search-dir>/rts-$rts_path
9642 The selected path is handled like a normal RTS path.
9646 @node Mode Switches for gnatmake
9647 @section Mode Switches for @command{gnatmake}
9650 The mode switches (referred to as @code{mode_switches}) allow the
9651 inclusion of switches that are to be passed to the compiler itself, the
9652 binder or the linker. The effect of a mode switch is to cause all
9653 subsequent switches up to the end of the switch list, or up to the next
9654 mode switch, to be interpreted as switches to be passed on to the
9655 designated component of GNAT.
9659 @item -cargs @var{switches}
9660 @cindex @option{-cargs} (@command{gnatmake})
9661 Compiler switches. Here @var{switches} is a list of switches
9662 that are valid switches for @command{gcc}. They will be passed on to
9663 all compile steps performed by @command{gnatmake}.
9665 @item -bargs @var{switches}
9666 @cindex @option{-bargs} (@command{gnatmake})
9667 Binder switches. Here @var{switches} is a list of switches
9668 that are valid switches for @code{gnatbind}. They will be passed on to
9669 all bind steps performed by @command{gnatmake}.
9671 @item -largs @var{switches}
9672 @cindex @option{-largs} (@command{gnatmake})
9673 Linker switches. Here @var{switches} is a list of switches
9674 that are valid switches for @command{gnatlink}. They will be passed on to
9675 all link steps performed by @command{gnatmake}.
9677 @item -margs @var{switches}
9678 @cindex @option{-margs} (@command{gnatmake})
9679 Make switches. The switches are directly interpreted by @command{gnatmake},
9680 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9684 @node Notes on the Command Line
9685 @section Notes on the Command Line
9688 This section contains some additional useful notes on the operation
9689 of the @command{gnatmake} command.
9693 @cindex Recompilation, by @command{gnatmake}
9694 If @command{gnatmake} finds no ALI files, it recompiles the main program
9695 and all other units required by the main program.
9696 This means that @command{gnatmake}
9697 can be used for the initial compile, as well as during subsequent steps of
9698 the development cycle.
9701 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9702 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9703 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9707 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9708 is used to specify both source and
9709 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9710 instead if you just want to specify
9711 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9712 if you want to specify library paths
9716 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9717 This may conveniently be used to exclude standard libraries from
9718 consideration and in particular it means that the use of the
9719 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9720 unless @option{^-a^/ALL_FILES^} is also specified.
9723 @command{gnatmake} has been designed to make the use of Ada libraries
9724 particularly convenient. Assume you have an Ada library organized
9725 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9726 of your Ada compilation units,
9727 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9728 specs of these units, but no bodies. Then to compile a unit
9729 stored in @code{main.adb}, which uses this Ada library you would just type
9733 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9736 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9737 /SKIP_MISSING=@i{[OBJ_DIR]} main
9742 Using @command{gnatmake} along with the
9743 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9744 switch provides a mechanism for avoiding unnecessary recompilations. Using
9746 you can update the comments/format of your
9747 source files without having to recompile everything. Note, however, that
9748 adding or deleting lines in a source files may render its debugging
9749 info obsolete. If the file in question is a spec, the impact is rather
9750 limited, as that debugging info will only be useful during the
9751 elaboration phase of your program. For bodies the impact can be more
9752 significant. In all events, your debugger will warn you if a source file
9753 is more recent than the corresponding object, and alert you to the fact
9754 that the debugging information may be out of date.
9757 @node How gnatmake Works
9758 @section How @command{gnatmake} Works
9761 Generally @command{gnatmake} automatically performs all necessary
9762 recompilations and you don't need to worry about how it works. However,
9763 it may be useful to have some basic understanding of the @command{gnatmake}
9764 approach and in particular to understand how it uses the results of
9765 previous compilations without incorrectly depending on them.
9767 First a definition: an object file is considered @dfn{up to date} if the
9768 corresponding ALI file exists and if all the source files listed in the
9769 dependency section of this ALI file have time stamps matching those in
9770 the ALI file. This means that neither the source file itself nor any
9771 files that it depends on have been modified, and hence there is no need
9772 to recompile this file.
9774 @command{gnatmake} works by first checking if the specified main unit is up
9775 to date. If so, no compilations are required for the main unit. If not,
9776 @command{gnatmake} compiles the main program to build a new ALI file that
9777 reflects the latest sources. Then the ALI file of the main unit is
9778 examined to find all the source files on which the main program depends,
9779 and @command{gnatmake} recursively applies the above procedure on all these
9782 This process ensures that @command{gnatmake} only trusts the dependencies
9783 in an existing ALI file if they are known to be correct. Otherwise it
9784 always recompiles to determine a new, guaranteed accurate set of
9785 dependencies. As a result the program is compiled ``upside down'' from what may
9786 be more familiar as the required order of compilation in some other Ada
9787 systems. In particular, clients are compiled before the units on which
9788 they depend. The ability of GNAT to compile in any order is critical in
9789 allowing an order of compilation to be chosen that guarantees that
9790 @command{gnatmake} will recompute a correct set of new dependencies if
9793 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9794 imported by several of the executables, it will be recompiled at most once.
9796 Note: when using non-standard naming conventions
9797 (@pxref{Using Other File Names}), changing through a configuration pragmas
9798 file the version of a source and invoking @command{gnatmake} to recompile may
9799 have no effect, if the previous version of the source is still accessible
9800 by @command{gnatmake}. It may be necessary to use the switch
9801 ^-f^/FORCE_COMPILE^.
9803 @node Examples of gnatmake Usage
9804 @section Examples of @command{gnatmake} Usage
9807 @item gnatmake hello.adb
9808 Compile all files necessary to bind and link the main program
9809 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9810 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9812 @item gnatmake main1 main2 main3
9813 Compile all files necessary to bind and link the main programs
9814 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9815 (containing unit @code{Main2}) and @file{main3.adb}
9816 (containing unit @code{Main3}) and bind and link the resulting object files
9817 to generate three executable files @file{^main1^MAIN1.EXE^},
9818 @file{^main2^MAIN2.EXE^}
9819 and @file{^main3^MAIN3.EXE^}.
9822 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9826 @item gnatmake Main_Unit /QUIET
9827 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9828 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9830 Compile all files necessary to bind and link the main program unit
9831 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9832 be done with optimization level 2 and the order of elaboration will be
9833 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9834 displaying commands it is executing.
9837 @c *************************
9838 @node Improving Performance
9839 @chapter Improving Performance
9840 @cindex Improving performance
9843 This chapter presents several topics related to program performance.
9844 It first describes some of the tradeoffs that need to be considered
9845 and some of the techniques for making your program run faster.
9846 It then documents the @command{gnatelim} tool and unused subprogram/data
9847 elimination feature, which can reduce the size of program executables.
9849 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9850 driver (see @ref{The GNAT Driver and Project Files}).
9854 * Performance Considerations::
9855 * Text_IO Suggestions::
9856 * Reducing Size of Ada Executables with gnatelim::
9857 * Reducing Size of Executables with unused subprogram/data elimination::
9861 @c *****************************
9862 @node Performance Considerations
9863 @section Performance Considerations
9866 The GNAT system provides a number of options that allow a trade-off
9871 performance of the generated code
9874 speed of compilation
9877 minimization of dependences and recompilation
9880 the degree of run-time checking.
9884 The defaults (if no options are selected) aim at improving the speed
9885 of compilation and minimizing dependences, at the expense of performance
9886 of the generated code:
9893 no inlining of subprogram calls
9896 all run-time checks enabled except overflow and elaboration checks
9900 These options are suitable for most program development purposes. This
9901 chapter describes how you can modify these choices, and also provides
9902 some guidelines on debugging optimized code.
9905 * Controlling Run-Time Checks::
9906 * Use of Restrictions::
9907 * Optimization Levels::
9908 * Debugging Optimized Code::
9909 * Inlining of Subprograms::
9910 * Other Optimization Switches::
9911 * Optimization and Strict Aliasing::
9914 * Coverage Analysis::
9918 @node Controlling Run-Time Checks
9919 @subsection Controlling Run-Time Checks
9922 By default, GNAT generates all run-time checks, except integer overflow
9923 checks, stack overflow checks, and checks for access before elaboration on
9924 subprogram calls. The latter are not required in default mode, because all
9925 necessary checking is done at compile time.
9926 @cindex @option{-gnatp} (@command{gcc})
9927 @cindex @option{-gnato} (@command{gcc})
9928 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9929 be modified. @xref{Run-Time Checks}.
9931 Our experience is that the default is suitable for most development
9934 We treat integer overflow specially because these
9935 are quite expensive and in our experience are not as important as other
9936 run-time checks in the development process. Note that division by zero
9937 is not considered an overflow check, and divide by zero checks are
9938 generated where required by default.
9940 Elaboration checks are off by default, and also not needed by default, since
9941 GNAT uses a static elaboration analysis approach that avoids the need for
9942 run-time checking. This manual contains a full chapter discussing the issue
9943 of elaboration checks, and if the default is not satisfactory for your use,
9944 you should read this chapter.
9946 For validity checks, the minimal checks required by the Ada Reference
9947 Manual (for case statements and assignments to array elements) are on
9948 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9949 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9950 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9951 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9952 are also suppressed entirely if @option{-gnatp} is used.
9954 @cindex Overflow checks
9955 @cindex Checks, overflow
9958 @cindex pragma Suppress
9959 @cindex pragma Unsuppress
9960 Note that the setting of the switches controls the default setting of
9961 the checks. They may be modified using either @code{pragma Suppress} (to
9962 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9963 checks) in the program source.
9965 @node Use of Restrictions
9966 @subsection Use of Restrictions
9969 The use of pragma Restrictions allows you to control which features are
9970 permitted in your program. Apart from the obvious point that if you avoid
9971 relatively expensive features like finalization (enforceable by the use
9972 of pragma Restrictions (No_Finalization), the use of this pragma does not
9973 affect the generated code in most cases.
9975 One notable exception to this rule is that the possibility of task abort
9976 results in some distributed overhead, particularly if finalization or
9977 exception handlers are used. The reason is that certain sections of code
9978 have to be marked as non-abortable.
9980 If you use neither the @code{abort} statement, nor asynchronous transfer
9981 of control (@code{select @dots{} then abort}), then this distributed overhead
9982 is removed, which may have a general positive effect in improving
9983 overall performance. Especially code involving frequent use of tasking
9984 constructs and controlled types will show much improved performance.
9985 The relevant restrictions pragmas are
9987 @smallexample @c ada
9988 pragma Restrictions (No_Abort_Statements);
9989 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9993 It is recommended that these restriction pragmas be used if possible. Note
9994 that this also means that you can write code without worrying about the
9995 possibility of an immediate abort at any point.
9997 @node Optimization Levels
9998 @subsection Optimization Levels
9999 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
10002 Without any optimization ^option,^qualifier,^
10003 the compiler's goal is to reduce the cost of
10004 compilation and to make debugging produce the expected results.
10005 Statements are independent: if you stop the program with a breakpoint between
10006 statements, you can then assign a new value to any variable or change
10007 the program counter to any other statement in the subprogram and get exactly
10008 the results you would expect from the source code.
10010 Turning on optimization makes the compiler attempt to improve the
10011 performance and/or code size at the expense of compilation time and
10012 possibly the ability to debug the program.
10014 If you use multiple
10015 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10016 the last such option is the one that is effective.
10019 The default is optimization off. This results in the fastest compile
10020 times, but GNAT makes absolutely no attempt to optimize, and the
10021 generated programs are considerably larger and slower than when
10022 optimization is enabled. You can use the
10024 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10025 @option{-O2}, @option{-O3}, and @option{-Os})
10028 @code{OPTIMIZE} qualifier
10030 to @command{gcc} to control the optimization level:
10033 @item ^-O0^/OPTIMIZE=NONE^
10034 No optimization (the default);
10035 generates unoptimized code but has
10036 the fastest compilation time.
10038 Note that many other compilers do fairly extensive optimization
10039 even if ``no optimization'' is specified. With gcc, it is
10040 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10041 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10042 really does mean no optimization at all. This difference between
10043 gcc and other compilers should be kept in mind when doing
10044 performance comparisons.
10046 @item ^-O1^/OPTIMIZE=SOME^
10047 Moderate optimization;
10048 optimizes reasonably well but does not
10049 degrade compilation time significantly.
10051 @item ^-O2^/OPTIMIZE=ALL^
10053 @itemx /OPTIMIZE=DEVELOPMENT
10056 generates highly optimized code and has
10057 the slowest compilation time.
10059 @item ^-O3^/OPTIMIZE=INLINING^
10060 Full optimization as in @option{-O2},
10061 and also attempts automatic inlining of small
10062 subprograms within a unit (@pxref{Inlining of Subprograms}).
10064 @item ^-Os^/OPTIMIZE=SPACE^
10065 Optimize space usage of resulting program.
10069 Higher optimization levels perform more global transformations on the
10070 program and apply more expensive analysis algorithms in order to generate
10071 faster and more compact code. The price in compilation time, and the
10072 resulting improvement in execution time,
10073 both depend on the particular application and the hardware environment.
10074 You should experiment to find the best level for your application.
10076 Since the precise set of optimizations done at each level will vary from
10077 release to release (and sometime from target to target), it is best to think
10078 of the optimization settings in general terms.
10079 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10080 the GNU Compiler Collection (GCC)}, for details about
10081 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10082 individually enable or disable specific optimizations.
10084 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10085 been tested extensively at all optimization levels. There are some bugs
10086 which appear only with optimization turned on, but there have also been
10087 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10088 level of optimization does not improve the reliability of the code
10089 generator, which in practice is highly reliable at all optimization
10092 Note regarding the use of @option{-O3}: The use of this optimization level
10093 is generally discouraged with GNAT, since it often results in larger
10094 executables which run more slowly. See further discussion of this point
10095 in @ref{Inlining of Subprograms}.
10097 @node Debugging Optimized Code
10098 @subsection Debugging Optimized Code
10099 @cindex Debugging optimized code
10100 @cindex Optimization and debugging
10103 Although it is possible to do a reasonable amount of debugging at
10105 nonzero optimization levels,
10106 the higher the level the more likely that
10109 @option{/OPTIMIZE} settings other than @code{NONE},
10110 such settings will make it more likely that
10112 source-level constructs will have been eliminated by optimization.
10113 For example, if a loop is strength-reduced, the loop
10114 control variable may be completely eliminated and thus cannot be
10115 displayed in the debugger.
10116 This can only happen at @option{-O2} or @option{-O3}.
10117 Explicit temporary variables that you code might be eliminated at
10118 ^level^setting^ @option{-O1} or higher.
10120 The use of the @option{^-g^/DEBUG^} switch,
10121 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10122 which is needed for source-level debugging,
10123 affects the size of the program executable on disk,
10124 and indeed the debugging information can be quite large.
10125 However, it has no effect on the generated code (and thus does not
10126 degrade performance)
10128 Since the compiler generates debugging tables for a compilation unit before
10129 it performs optimizations, the optimizing transformations may invalidate some
10130 of the debugging data. You therefore need to anticipate certain
10131 anomalous situations that may arise while debugging optimized code.
10132 These are the most common cases:
10136 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10138 the PC bouncing back and forth in the code. This may result from any of
10139 the following optimizations:
10143 @i{Common subexpression elimination:} using a single instance of code for a
10144 quantity that the source computes several times. As a result you
10145 may not be able to stop on what looks like a statement.
10148 @i{Invariant code motion:} moving an expression that does not change within a
10149 loop, to the beginning of the loop.
10152 @i{Instruction scheduling:} moving instructions so as to
10153 overlap loads and stores (typically) with other code, or in
10154 general to move computations of values closer to their uses. Often
10155 this causes you to pass an assignment statement without the assignment
10156 happening and then later bounce back to the statement when the
10157 value is actually needed. Placing a breakpoint on a line of code
10158 and then stepping over it may, therefore, not always cause all the
10159 expected side-effects.
10163 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10164 two identical pieces of code are merged and the program counter suddenly
10165 jumps to a statement that is not supposed to be executed, simply because
10166 it (and the code following) translates to the same thing as the code
10167 that @emph{was} supposed to be executed. This effect is typically seen in
10168 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10169 a @code{break} in a C @code{^switch^switch^} statement.
10172 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10173 There are various reasons for this effect:
10177 In a subprogram prologue, a parameter may not yet have been moved to its
10181 A variable may be dead, and its register re-used. This is
10182 probably the most common cause.
10185 As mentioned above, the assignment of a value to a variable may
10189 A variable may be eliminated entirely by value propagation or
10190 other means. In this case, GCC may incorrectly generate debugging
10191 information for the variable
10195 In general, when an unexpected value appears for a local variable or parameter
10196 you should first ascertain if that value was actually computed by
10197 your program, as opposed to being incorrectly reported by the debugger.
10199 array elements in an object designated by an access value
10200 are generally less of a problem, once you have ascertained that the access
10202 Typically, this means checking variables in the preceding code and in the
10203 calling subprogram to verify that the value observed is explainable from other
10204 values (one must apply the procedure recursively to those
10205 other values); or re-running the code and stopping a little earlier
10206 (perhaps before the call) and stepping to better see how the variable obtained
10207 the value in question; or continuing to step @emph{from} the point of the
10208 strange value to see if code motion had simply moved the variable's
10213 In light of such anomalies, a recommended technique is to use @option{-O0}
10214 early in the software development cycle, when extensive debugging capabilities
10215 are most needed, and then move to @option{-O1} and later @option{-O2} as
10216 the debugger becomes less critical.
10217 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10218 a release management issue.
10220 Note that if you use @option{-g} you can then use the @command{strip} program
10221 on the resulting executable,
10222 which removes both debugging information and global symbols.
10225 @node Inlining of Subprograms
10226 @subsection Inlining of Subprograms
10229 A call to a subprogram in the current unit is inlined if all the
10230 following conditions are met:
10234 The optimization level is at least @option{-O1}.
10237 The called subprogram is suitable for inlining: It must be small enough
10238 and not contain something that @command{gcc} cannot support in inlined
10242 @cindex pragma Inline
10244 Either @code{pragma Inline} applies to the subprogram, or it is local
10245 to the unit and called once from within it, or it is small and automatic
10246 inlining (optimization level @option{-O3}) is specified.
10250 Calls to subprograms in @code{with}'ed units are normally not inlined.
10251 To achieve actual inlining (that is, replacement of the call by the code
10252 in the body of the subprogram), the following conditions must all be true.
10256 The optimization level is at least @option{-O1}.
10259 The called subprogram is suitable for inlining: It must be small enough
10260 and not contain something that @command{gcc} cannot support in inlined
10264 The call appears in a body (not in a package spec).
10267 There is a @code{pragma Inline} for the subprogram.
10270 @cindex @option{-gnatn} (@command{gcc})
10271 The @option{^-gnatn^/INLINE^} switch
10272 is used in the @command{gcc} command line
10275 Even if all these conditions are met, it may not be possible for
10276 the compiler to inline the call, due to the length of the body,
10277 or features in the body that make it impossible for the compiler
10278 to do the inlining.
10280 Note that specifying the @option{-gnatn} switch causes additional
10281 compilation dependencies. Consider the following:
10283 @smallexample @c ada
10303 With the default behavior (no @option{-gnatn} switch specified), the
10304 compilation of the @code{Main} procedure depends only on its own source,
10305 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10306 means that editing the body of @code{R} does not require recompiling
10309 On the other hand, the call @code{R.Q} is not inlined under these
10310 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10311 is compiled, the call will be inlined if the body of @code{Q} is small
10312 enough, but now @code{Main} depends on the body of @code{R} in
10313 @file{r.adb} as well as on the spec. This means that if this body is edited,
10314 the main program must be recompiled. Note that this extra dependency
10315 occurs whether or not the call is in fact inlined by @command{gcc}.
10317 The use of front end inlining with @option{-gnatN} generates similar
10318 additional dependencies.
10320 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10321 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10322 can be used to prevent
10323 all inlining. This switch overrides all other conditions and ensures
10324 that no inlining occurs. The extra dependences resulting from
10325 @option{-gnatn} will still be active, even if
10326 this switch is used to suppress the resulting inlining actions.
10328 @cindex @option{-fno-inline-functions} (@command{gcc})
10329 Note: The @option{-fno-inline-functions} switch can be used to prevent
10330 automatic inlining of small subprograms if @option{-O3} is used.
10332 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10333 Note: The @option{-fno-inline-functions-called-once} switch
10334 can be used to prevent inlining of subprograms local to the unit
10335 and called once from within it if @option{-O1} is used.
10337 Note regarding the use of @option{-O3}: There is no difference in inlining
10338 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10339 pragma @code{Inline} assuming the use of @option{-gnatn}
10340 or @option{-gnatN} (the switches that activate inlining). If you have used
10341 pragma @code{Inline} in appropriate cases, then it is usually much better
10342 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10343 in this case only has the effect of inlining subprograms you did not
10344 think should be inlined. We often find that the use of @option{-O3} slows
10345 down code by performing excessive inlining, leading to increased instruction
10346 cache pressure from the increased code size. So the bottom line here is
10347 that you should not automatically assume that @option{-O3} is better than
10348 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10349 it actually improves performance.
10351 @node Other Optimization Switches
10352 @subsection Other Optimization Switches
10353 @cindex Optimization Switches
10355 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10356 @command{gcc} optimization switches are potentially usable. These switches
10357 have not been extensively tested with GNAT but can generally be expected
10358 to work. Examples of switches in this category are
10359 @option{-funroll-loops} and
10360 the various target-specific @option{-m} options (in particular, it has been
10361 observed that @option{-march=pentium4} can significantly improve performance
10362 on appropriate machines). For full details of these switches, see
10363 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10364 the GNU Compiler Collection (GCC)}.
10366 @node Optimization and Strict Aliasing
10367 @subsection Optimization and Strict Aliasing
10369 @cindex Strict Aliasing
10370 @cindex No_Strict_Aliasing
10373 The strong typing capabilities of Ada allow an optimizer to generate
10374 efficient code in situations where other languages would be forced to
10375 make worst case assumptions preventing such optimizations. Consider
10376 the following example:
10378 @smallexample @c ada
10381 type Int1 is new Integer;
10382 type Int2 is new Integer;
10383 type Int1A is access Int1;
10384 type Int2A is access Int2;
10391 for J in Data'Range loop
10392 if Data (J) = Int1V.all then
10393 Int2V.all := Int2V.all + 1;
10402 In this example, since the variable @code{Int1V} can only access objects
10403 of type @code{Int1}, and @code{Int2V} can only access objects of type
10404 @code{Int2}, there is no possibility that the assignment to
10405 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10406 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10407 for all iterations of the loop and avoid the extra memory reference
10408 required to dereference it each time through the loop.
10410 This kind of optimization, called strict aliasing analysis, is
10411 triggered by specifying an optimization level of @option{-O2} or
10412 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10413 when access values are involved.
10415 However, although this optimization is always correct in terms of
10416 the formal semantics of the Ada Reference Manual, difficulties can
10417 arise if features like @code{Unchecked_Conversion} are used to break
10418 the typing system. Consider the following complete program example:
10420 @smallexample @c ada
10423 type int1 is new integer;
10424 type int2 is new integer;
10425 type a1 is access int1;
10426 type a2 is access int2;
10431 function to_a2 (Input : a1) return a2;
10434 with Unchecked_Conversion;
10436 function to_a2 (Input : a1) return a2 is
10438 new Unchecked_Conversion (a1, a2);
10440 return to_a2u (Input);
10446 with Text_IO; use Text_IO;
10448 v1 : a1 := new int1;
10449 v2 : a2 := to_a2 (v1);
10453 put_line (int1'image (v1.all));
10459 This program prints out 0 in @option{-O0} or @option{-O1}
10460 mode, but it prints out 1 in @option{-O2} mode. That's
10461 because in strict aliasing mode, the compiler can and
10462 does assume that the assignment to @code{v2.all} could not
10463 affect the value of @code{v1.all}, since different types
10466 This behavior is not a case of non-conformance with the standard, since
10467 the Ada RM specifies that an unchecked conversion where the resulting
10468 bit pattern is not a correct value of the target type can result in an
10469 abnormal value and attempting to reference an abnormal value makes the
10470 execution of a program erroneous. That's the case here since the result
10471 does not point to an object of type @code{int2}. This means that the
10472 effect is entirely unpredictable.
10474 However, although that explanation may satisfy a language
10475 lawyer, in practice an applications programmer expects an
10476 unchecked conversion involving pointers to create true
10477 aliases and the behavior of printing 1 seems plain wrong.
10478 In this case, the strict aliasing optimization is unwelcome.
10480 Indeed the compiler recognizes this possibility, and the
10481 unchecked conversion generates a warning:
10484 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10485 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10486 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10490 Unfortunately the problem is recognized when compiling the body of
10491 package @code{p2}, but the actual "bad" code is generated while
10492 compiling the body of @code{m} and this latter compilation does not see
10493 the suspicious @code{Unchecked_Conversion}.
10495 As implied by the warning message, there are approaches you can use to
10496 avoid the unwanted strict aliasing optimization in a case like this.
10498 One possibility is to simply avoid the use of @option{-O2}, but
10499 that is a bit drastic, since it throws away a number of useful
10500 optimizations that do not involve strict aliasing assumptions.
10502 A less drastic approach is to compile the program using the
10503 option @option{-fno-strict-aliasing}. Actually it is only the
10504 unit containing the dereferencing of the suspicious pointer
10505 that needs to be compiled. So in this case, if we compile
10506 unit @code{m} with this switch, then we get the expected
10507 value of zero printed. Analyzing which units might need
10508 the switch can be painful, so a more reasonable approach
10509 is to compile the entire program with options @option{-O2}
10510 and @option{-fno-strict-aliasing}. If the performance is
10511 satisfactory with this combination of options, then the
10512 advantage is that the entire issue of possible "wrong"
10513 optimization due to strict aliasing is avoided.
10515 To avoid the use of compiler switches, the configuration
10516 pragma @code{No_Strict_Aliasing} with no parameters may be
10517 used to specify that for all access types, the strict
10518 aliasing optimization should be suppressed.
10520 However, these approaches are still overkill, in that they causes
10521 all manipulations of all access values to be deoptimized. A more
10522 refined approach is to concentrate attention on the specific
10523 access type identified as problematic.
10525 First, if a careful analysis of uses of the pointer shows
10526 that there are no possible problematic references, then
10527 the warning can be suppressed by bracketing the
10528 instantiation of @code{Unchecked_Conversion} to turn
10531 @smallexample @c ada
10532 pragma Warnings (Off);
10534 new Unchecked_Conversion (a1, a2);
10535 pragma Warnings (On);
10539 Of course that approach is not appropriate for this particular
10540 example, since indeed there is a problematic reference. In this
10541 case we can take one of two other approaches.
10543 The first possibility is to move the instantiation of unchecked
10544 conversion to the unit in which the type is declared. In
10545 this example, we would move the instantiation of
10546 @code{Unchecked_Conversion} from the body of package
10547 @code{p2} to the spec of package @code{p1}. Now the
10548 warning disappears. That's because any use of the
10549 access type knows there is a suspicious unchecked
10550 conversion, and the strict aliasing optimization
10551 is automatically suppressed for the type.
10553 If it is not practical to move the unchecked conversion to the same unit
10554 in which the destination access type is declared (perhaps because the
10555 source type is not visible in that unit), you may use pragma
10556 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10557 same declarative sequence as the declaration of the access type:
10559 @smallexample @c ada
10560 type a2 is access int2;
10561 pragma No_Strict_Aliasing (a2);
10565 Here again, the compiler now knows that the strict aliasing optimization
10566 should be suppressed for any reference to type @code{a2} and the
10567 expected behavior is obtained.
10569 Finally, note that although the compiler can generate warnings for
10570 simple cases of unchecked conversions, there are tricker and more
10571 indirect ways of creating type incorrect aliases which the compiler
10572 cannot detect. Examples are the use of address overlays and unchecked
10573 conversions involving composite types containing access types as
10574 components. In such cases, no warnings are generated, but there can
10575 still be aliasing problems. One safe coding practice is to forbid the
10576 use of address clauses for type overlaying, and to allow unchecked
10577 conversion only for primitive types. This is not really a significant
10578 restriction since any possible desired effect can be achieved by
10579 unchecked conversion of access values.
10581 The aliasing analysis done in strict aliasing mode can certainly
10582 have significant benefits. We have seen cases of large scale
10583 application code where the time is increased by up to 5% by turning
10584 this optimization off. If you have code that includes significant
10585 usage of unchecked conversion, you might want to just stick with
10586 @option{-O1} and avoid the entire issue. If you get adequate
10587 performance at this level of optimization level, that's probably
10588 the safest approach. If tests show that you really need higher
10589 levels of optimization, then you can experiment with @option{-O2}
10590 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10591 has on size and speed of the code. If you really need to use
10592 @option{-O2} with strict aliasing in effect, then you should
10593 review any uses of unchecked conversion of access types,
10594 particularly if you are getting the warnings described above.
10597 @node Coverage Analysis
10598 @subsection Coverage Analysis
10601 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10602 the user to determine the distribution of execution time across a program,
10603 @pxref{Profiling} for details of usage.
10607 @node Text_IO Suggestions
10608 @section @code{Text_IO} Suggestions
10609 @cindex @code{Text_IO} and performance
10612 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10613 the requirement of maintaining page and line counts. If performance
10614 is critical, a recommendation is to use @code{Stream_IO} instead of
10615 @code{Text_IO} for volume output, since this package has less overhead.
10617 If @code{Text_IO} must be used, note that by default output to the standard
10618 output and standard error files is unbuffered (this provides better
10619 behavior when output statements are used for debugging, or if the
10620 progress of a program is observed by tracking the output, e.g. by
10621 using the Unix @command{tail -f} command to watch redirected output.
10623 If you are generating large volumes of output with @code{Text_IO} and
10624 performance is an important factor, use a designated file instead
10625 of the standard output file, or change the standard output file to
10626 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10630 @node Reducing Size of Ada Executables with gnatelim
10631 @section Reducing Size of Ada Executables with @code{gnatelim}
10635 This section describes @command{gnatelim}, a tool which detects unused
10636 subprograms and helps the compiler to create a smaller executable for your
10641 * Running gnatelim::
10642 * Processing Precompiled Libraries::
10643 * Correcting the List of Eliminate Pragmas::
10644 * Making Your Executables Smaller::
10645 * Summary of the gnatelim Usage Cycle::
10648 @node About gnatelim
10649 @subsection About @code{gnatelim}
10652 When a program shares a set of Ada
10653 packages with other programs, it may happen that this program uses
10654 only a fraction of the subprograms defined in these packages. The code
10655 created for these unused subprograms increases the size of the executable.
10657 @code{gnatelim} tracks unused subprograms in an Ada program and
10658 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10659 subprograms that are declared but never called. By placing the list of
10660 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10661 recompiling your program, you may decrease the size of its executable,
10662 because the compiler will not generate the code for 'eliminated' subprograms.
10663 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10664 information about this pragma.
10666 @code{gnatelim} needs as its input data the name of the main subprogram.
10668 If a set of source files is specified as @code{gnatelim} arguments, it
10669 treats these files as a complete set of sources making up a program to
10670 analyse, and analyses only these sources.
10672 After a full successful build of the main subprogram @code{gnatelim} can be
10673 called without specifying sources to analyse, in this case it computes
10674 the source closure of the main unit from the @file{ALI} files.
10676 The following command will create the set of @file{ALI} files needed for
10680 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10683 Note that @code{gnatelim} does not need object files.
10685 @node Running gnatelim
10686 @subsection Running @code{gnatelim}
10689 @code{gnatelim} has the following command-line interface:
10692 $ gnatelim [@var{switches}] ^-main^?MAIN^=@var{main_unit_name} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
10696 @var{main_unit_name} should be a name of a source file that contains the main
10697 subprogram of a program (partition).
10699 Each @var{filename} is the name (including the extension) of a source
10700 file to process. ``Wildcards'' are allowed, and
10701 the file name may contain path information.
10703 @samp{@var{gcc_switches}} is a list of switches for
10704 @command{gcc}. They will be passed on to all compiler invocations made by
10705 @command{gnatelim} to generate the ASIS trees. Here you can provide
10706 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
10707 use the @option{-gnatec} switch to set the configuration file etc.
10709 @code{gnatelim} has the following switches:
10713 @item ^-files^/FILES^=@var{filename}
10714 @cindex @option{^-files^/FILES^} (@code{gnatelim})
10715 Take the argument source files from the specified file. This file should be an
10716 ordinary text file containing file names separated by spaces or
10717 line breaks. You can use this switch more than once in the same call to
10718 @command{gnatelim}. You also can combine this switch with
10719 an explicit list of files.
10722 @cindex @option{^-log^/LOG^} (@command{gnatelim})
10723 Duplicate all the output sent to @file{stderr} into a log file. The log file
10724 is named @file{gnatelim.log} and is located in the current directory.
10726 @item ^-log^/LOGFILE^=@var{filename}
10727 @cindex @option{^-log^/LOGFILE^} (@command{gnatelim})
10728 Duplicate all the output sent to @file{stderr} into a specified log file.
10730 @cindex @option{^--no-elim-dispatch^/NO_DISPATCH^} (@command{gnatelim})
10731 @item ^--no-elim-dispatch^/NO_DISPATCH^
10732 Do not generate pragmas for dispatching operations.
10734 @cindex @option{^-o^/OUTPUT^} (@command{gnatelim})
10735 @item ^-o^/OUTPUT^=@var{report_file}
10736 Put @command{gnatelim} output into a specified file. If this file already exists,
10737 it is overridden. If this switch is not used, @command{gnatelim} outputs its results
10741 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10742 Quiet mode: by default @code{gnatelim} outputs to the standard error
10743 stream the number of program units left to be processed. This option turns
10746 @cindex @option{^-t^/TIME^} (@command{gnatelim})
10748 Print out execution time.
10750 @item ^-v^/VERBOSE^
10751 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10752 Verbose mode: @code{gnatelim} version information is printed as Ada
10753 comments to the standard output stream. Also, in addition to the number of
10754 program units left @code{gnatelim} will output the name of the current unit
10757 @item ^-wq^/WARNINGS=QUIET^
10758 @cindex @option{^-wq^/WARNINGS=QUIET^} (@command{gnatelim})
10759 Quet warning mode - some warnings are suppressed. In particular warnings that
10760 indicate that the analysed set of sources is incomplete to make up a
10761 partition and that some subprogram bodies are missing are not generated.
10764 @node Processing Precompiled Libraries
10765 @subsection Processing Precompiled Libraries
10768 If some program uses a precompiled Ada library, it can be processed by
10769 @code{gnatelim} in a usual way. @code{gnatelim} will newer generate an
10770 Eliminate pragma for a subprogram if the body of this subprogram has not
10771 been analysed, this is a typical case for subprograms from precompiled
10772 libraries. Switch @option{^-wq^/WARNINGS=QUIET^} may be used to suppress
10773 warnings about missing source files and non-analyzed subprogram bodies
10774 that can be generated when processing precompiled Ada libraries.
10776 @node Correcting the List of Eliminate Pragmas
10777 @subsection Correcting the List of Eliminate Pragmas
10780 In some rare cases @code{gnatelim} may try to eliminate
10781 subprograms that are actually called in the program. In this case, the
10782 compiler will generate an error message of the form:
10785 main.adb:4:08: cannot reference subprogram "P" eliminated at elim.out:5
10789 You will need to manually remove the wrong @code{Eliminate} pragmas from
10790 the configuration file indicated in the error message. You should recompile
10791 your program from scratch after that, because you need a consistent
10792 configuration file(s) during the entire compilation.
10794 @node Making Your Executables Smaller
10795 @subsection Making Your Executables Smaller
10798 In order to get a smaller executable for your program you now have to
10799 recompile the program completely with the configuration file containing
10800 pragmas Eliminate generated by gnatelim. If these pragmas are placed in
10801 @file{gnat.adc} file located in your current directory, just do:
10804 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10808 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10809 recompile everything
10810 with the set of pragmas @code{Eliminate} that you have obtained with
10811 @command{gnatelim}).
10813 Be aware that the set of @code{Eliminate} pragmas is specific to each
10814 program. It is not recommended to merge sets of @code{Eliminate}
10815 pragmas created for different programs in one configuration file.
10817 @node Summary of the gnatelim Usage Cycle
10818 @subsection Summary of the @code{gnatelim} Usage Cycle
10821 Here is a quick summary of the steps to be taken in order to reduce
10822 the size of your executables with @code{gnatelim}. You may use
10823 other GNAT options to control the optimization level,
10824 to produce the debugging information, to set search path, etc.
10828 Create a complete set of @file{ALI} files (if the program has not been
10832 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10836 Generate a list of @code{Eliminate} pragmas in default configuration file
10837 @file{gnat.adc} in the current directory
10840 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10843 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10848 Recompile the application
10851 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10856 @node Reducing Size of Executables with unused subprogram/data elimination
10857 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10858 @findex unused subprogram/data elimination
10861 This section describes how you can eliminate unused subprograms and data from
10862 your executable just by setting options at compilation time.
10865 * About unused subprogram/data elimination::
10866 * Compilation options::
10867 * Example of unused subprogram/data elimination::
10870 @node About unused subprogram/data elimination
10871 @subsection About unused subprogram/data elimination
10874 By default, an executable contains all code and data of its composing objects
10875 (directly linked or coming from statically linked libraries), even data or code
10876 never used by this executable.
10878 This feature will allow you to eliminate such unused code from your
10879 executable, making it smaller (in disk and in memory).
10881 This functionality is available on all Linux platforms except for the IA-64
10882 architecture and on all cross platforms using the ELF binary file format.
10883 In both cases GNU binutils version 2.16 or later are required to enable it.
10885 @node Compilation options
10886 @subsection Compilation options
10889 The operation of eliminating the unused code and data from the final executable
10890 is directly performed by the linker.
10892 In order to do this, it has to work with objects compiled with the
10894 @option{-ffunction-sections} @option{-fdata-sections}.
10895 @cindex @option{-ffunction-sections} (@command{gcc})
10896 @cindex @option{-fdata-sections} (@command{gcc})
10897 These options are usable with C and Ada files.
10898 They will place respectively each
10899 function or data in a separate section in the resulting object file.
10901 Once the objects and static libraries are created with these options, the
10902 linker can perform the dead code elimination. You can do this by setting
10903 the @option{-Wl,--gc-sections} option to gcc command or in the
10904 @option{-largs} section of @command{gnatmake}. This will perform a
10905 garbage collection of code and data never referenced.
10907 If the linker performs a partial link (@option{-r} ld linker option), then you
10908 will need to provide one or several entry point using the
10909 @option{-e} / @option{--entry} ld option.
10911 Note that objects compiled without the @option{-ffunction-sections} and
10912 @option{-fdata-sections} options can still be linked with the executable.
10913 However, no dead code elimination will be performed on those objects (they will
10916 The GNAT static library is now compiled with -ffunction-sections and
10917 -fdata-sections on some platforms. This allows you to eliminate the unused code
10918 and data of the GNAT library from your executable.
10920 @node Example of unused subprogram/data elimination
10921 @subsection Example of unused subprogram/data elimination
10924 Here is a simple example:
10926 @smallexample @c ada
10935 Used_Data : Integer;
10936 Unused_Data : Integer;
10938 procedure Used (Data : Integer);
10939 procedure Unused (Data : Integer);
10942 package body Aux is
10943 procedure Used (Data : Integer) is
10948 procedure Unused (Data : Integer) is
10950 Unused_Data := Data;
10956 @code{Unused} and @code{Unused_Data} are never referenced in this code
10957 excerpt, and hence they may be safely removed from the final executable.
10962 $ nm test | grep used
10963 020015f0 T aux__unused
10964 02005d88 B aux__unused_data
10965 020015cc T aux__used
10966 02005d84 B aux__used_data
10968 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10969 -largs -Wl,--gc-sections
10971 $ nm test | grep used
10972 02005350 T aux__used
10973 0201ffe0 B aux__used_data
10977 It can be observed that the procedure @code{Unused} and the object
10978 @code{Unused_Data} are removed by the linker when using the
10979 appropriate options.
10981 @c ********************************
10982 @node Renaming Files Using gnatchop
10983 @chapter Renaming Files Using @code{gnatchop}
10987 This chapter discusses how to handle files with multiple units by using
10988 the @code{gnatchop} utility. This utility is also useful in renaming
10989 files to meet the standard GNAT default file naming conventions.
10992 * Handling Files with Multiple Units::
10993 * Operating gnatchop in Compilation Mode::
10994 * Command Line for gnatchop::
10995 * Switches for gnatchop::
10996 * Examples of gnatchop Usage::
10999 @node Handling Files with Multiple Units
11000 @section Handling Files with Multiple Units
11003 The basic compilation model of GNAT requires that a file submitted to the
11004 compiler have only one unit and there be a strict correspondence
11005 between the file name and the unit name.
11007 The @code{gnatchop} utility allows both of these rules to be relaxed,
11008 allowing GNAT to process files which contain multiple compilation units
11009 and files with arbitrary file names. @code{gnatchop}
11010 reads the specified file and generates one or more output files,
11011 containing one unit per file. The unit and the file name correspond,
11012 as required by GNAT.
11014 If you want to permanently restructure a set of ``foreign'' files so that
11015 they match the GNAT rules, and do the remaining development using the
11016 GNAT structure, you can simply use @command{gnatchop} once, generate the
11017 new set of files and work with them from that point on.
11019 Alternatively, if you want to keep your files in the ``foreign'' format,
11020 perhaps to maintain compatibility with some other Ada compilation
11021 system, you can set up a procedure where you use @command{gnatchop} each
11022 time you compile, regarding the source files that it writes as temporary
11023 files that you throw away.
11025 Note that if your file containing multiple units starts with a byte order
11026 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11027 will each start with a copy of this BOM, meaning that they can be compiled
11028 automatically in UTF-8 mode without needing to specify an explicit encoding.
11030 @node Operating gnatchop in Compilation Mode
11031 @section Operating gnatchop in Compilation Mode
11034 The basic function of @code{gnatchop} is to take a file with multiple units
11035 and split it into separate files. The boundary between files is reasonably
11036 clear, except for the issue of comments and pragmas. In default mode, the
11037 rule is that any pragmas between units belong to the previous unit, except
11038 that configuration pragmas always belong to the following unit. Any comments
11039 belong to the following unit. These rules
11040 almost always result in the right choice of
11041 the split point without needing to mark it explicitly and most users will
11042 find this default to be what they want. In this default mode it is incorrect to
11043 submit a file containing only configuration pragmas, or one that ends in
11044 configuration pragmas, to @code{gnatchop}.
11046 However, using a special option to activate ``compilation mode'',
11048 can perform another function, which is to provide exactly the semantics
11049 required by the RM for handling of configuration pragmas in a compilation.
11050 In the absence of configuration pragmas (at the main file level), this
11051 option has no effect, but it causes such configuration pragmas to be handled
11052 in a quite different manner.
11054 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11055 only configuration pragmas, then this file is appended to the
11056 @file{gnat.adc} file in the current directory. This behavior provides
11057 the required behavior described in the RM for the actions to be taken
11058 on submitting such a file to the compiler, namely that these pragmas
11059 should apply to all subsequent compilations in the same compilation
11060 environment. Using GNAT, the current directory, possibly containing a
11061 @file{gnat.adc} file is the representation
11062 of a compilation environment. For more information on the
11063 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11065 Second, in compilation mode, if @code{gnatchop}
11066 is given a file that starts with
11067 configuration pragmas, and contains one or more units, then these
11068 configuration pragmas are prepended to each of the chopped files. This
11069 behavior provides the required behavior described in the RM for the
11070 actions to be taken on compiling such a file, namely that the pragmas
11071 apply to all units in the compilation, but not to subsequently compiled
11074 Finally, if configuration pragmas appear between units, they are appended
11075 to the previous unit. This results in the previous unit being illegal,
11076 since the compiler does not accept configuration pragmas that follow
11077 a unit. This provides the required RM behavior that forbids configuration
11078 pragmas other than those preceding the first compilation unit of a
11081 For most purposes, @code{gnatchop} will be used in default mode. The
11082 compilation mode described above is used only if you need exactly
11083 accurate behavior with respect to compilations, and you have files
11084 that contain multiple units and configuration pragmas. In this
11085 circumstance the use of @code{gnatchop} with the compilation mode
11086 switch provides the required behavior, and is for example the mode
11087 in which GNAT processes the ACVC tests.
11089 @node Command Line for gnatchop
11090 @section Command Line for @code{gnatchop}
11093 The @code{gnatchop} command has the form:
11096 @c $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11097 @c @ovar{directory}
11098 @c Expanding @ovar macro inline (explanation in macro def comments)
11099 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11100 @r{[}@var{directory}@r{]}
11104 The only required argument is the file name of the file to be chopped.
11105 There are no restrictions on the form of this file name. The file itself
11106 contains one or more Ada units, in normal GNAT format, concatenated
11107 together. As shown, more than one file may be presented to be chopped.
11109 When run in default mode, @code{gnatchop} generates one output file in
11110 the current directory for each unit in each of the files.
11112 @var{directory}, if specified, gives the name of the directory to which
11113 the output files will be written. If it is not specified, all files are
11114 written to the current directory.
11116 For example, given a
11117 file called @file{hellofiles} containing
11119 @smallexample @c ada
11124 with Text_IO; use Text_IO;
11127 Put_Line ("Hello");
11137 $ gnatchop ^hellofiles^HELLOFILES.^
11141 generates two files in the current directory, one called
11142 @file{hello.ads} containing the single line that is the procedure spec,
11143 and the other called @file{hello.adb} containing the remaining text. The
11144 original file is not affected. The generated files can be compiled in
11148 When gnatchop is invoked on a file that is empty or that contains only empty
11149 lines and/or comments, gnatchop will not fail, but will not produce any
11152 For example, given a
11153 file called @file{toto.txt} containing
11155 @smallexample @c ada
11167 $ gnatchop ^toto.txt^TOT.TXT^
11171 will not produce any new file and will result in the following warnings:
11174 toto.txt:1:01: warning: empty file, contains no compilation units
11175 no compilation units found
11176 no source files written
11179 @node Switches for gnatchop
11180 @section Switches for @code{gnatchop}
11183 @command{gnatchop} recognizes the following switches:
11189 @cindex @option{--version} @command{gnatchop}
11190 Display Copyright and version, then exit disregarding all other options.
11193 @cindex @option{--help} @command{gnatchop}
11194 If @option{--version} was not used, display usage, then exit disregarding
11197 @item ^-c^/COMPILATION^
11198 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11199 Causes @code{gnatchop} to operate in compilation mode, in which
11200 configuration pragmas are handled according to strict RM rules. See
11201 previous section for a full description of this mode.
11204 @item -gnat@var{xxx}
11205 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11206 used to parse the given file. Not all @var{xxx} options make sense,
11207 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11208 process a source file that uses Latin-2 coding for identifiers.
11212 Causes @code{gnatchop} to generate a brief help summary to the standard
11213 output file showing usage information.
11215 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11216 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11217 Limit generated file names to the specified number @code{mm}
11219 This is useful if the
11220 resulting set of files is required to be interoperable with systems
11221 which limit the length of file names.
11223 If no value is given, or
11224 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11225 a default of 39, suitable for OpenVMS Alpha
11226 Systems, is assumed
11229 No space is allowed between the @option{-k} and the numeric value. The numeric
11230 value may be omitted in which case a default of @option{-k8},
11232 with DOS-like file systems, is used. If no @option{-k} switch
11234 there is no limit on the length of file names.
11237 @item ^-p^/PRESERVE^
11238 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11239 Causes the file ^modification^creation^ time stamp of the input file to be
11240 preserved and used for the time stamp of the output file(s). This may be
11241 useful for preserving coherency of time stamps in an environment where
11242 @code{gnatchop} is used as part of a standard build process.
11245 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11246 Causes output of informational messages indicating the set of generated
11247 files to be suppressed. Warnings and error messages are unaffected.
11249 @item ^-r^/REFERENCE^
11250 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11251 @findex Source_Reference
11252 Generate @code{Source_Reference} pragmas. Use this switch if the output
11253 files are regarded as temporary and development is to be done in terms
11254 of the original unchopped file. This switch causes
11255 @code{Source_Reference} pragmas to be inserted into each of the
11256 generated files to refers back to the original file name and line number.
11257 The result is that all error messages refer back to the original
11259 In addition, the debugging information placed into the object file (when
11260 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11262 also refers back to this original file so that tools like profilers and
11263 debuggers will give information in terms of the original unchopped file.
11265 If the original file to be chopped itself contains
11266 a @code{Source_Reference}
11267 pragma referencing a third file, then gnatchop respects
11268 this pragma, and the generated @code{Source_Reference} pragmas
11269 in the chopped file refer to the original file, with appropriate
11270 line numbers. This is particularly useful when @code{gnatchop}
11271 is used in conjunction with @code{gnatprep} to compile files that
11272 contain preprocessing statements and multiple units.
11274 @item ^-v^/VERBOSE^
11275 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11276 Causes @code{gnatchop} to operate in verbose mode. The version
11277 number and copyright notice are output, as well as exact copies of
11278 the gnat1 commands spawned to obtain the chop control information.
11280 @item ^-w^/OVERWRITE^
11281 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11282 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11283 fatal error if there is already a file with the same name as a
11284 file it would otherwise output, in other words if the files to be
11285 chopped contain duplicated units. This switch bypasses this
11286 check, and causes all but the last instance of such duplicated
11287 units to be skipped.
11290 @item --GCC=@var{xxxx}
11291 @cindex @option{--GCC=} (@code{gnatchop})
11292 Specify the path of the GNAT parser to be used. When this switch is used,
11293 no attempt is made to add the prefix to the GNAT parser executable.
11297 @node Examples of gnatchop Usage
11298 @section Examples of @code{gnatchop} Usage
11302 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11305 @item gnatchop -w hello_s.ada prerelease/files
11308 Chops the source file @file{hello_s.ada}. The output files will be
11309 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11311 files with matching names in that directory (no files in the current
11312 directory are modified).
11314 @item gnatchop ^archive^ARCHIVE.^
11315 Chops the source file @file{^archive^ARCHIVE.^}
11316 into the current directory. One
11317 useful application of @code{gnatchop} is in sending sets of sources
11318 around, for example in email messages. The required sources are simply
11319 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11321 @command{gnatchop} is used at the other end to reconstitute the original
11324 @item gnatchop file1 file2 file3 direc
11325 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11326 the resulting files in the directory @file{direc}. Note that if any units
11327 occur more than once anywhere within this set of files, an error message
11328 is generated, and no files are written. To override this check, use the
11329 @option{^-w^/OVERWRITE^} switch,
11330 in which case the last occurrence in the last file will
11331 be the one that is output, and earlier duplicate occurrences for a given
11332 unit will be skipped.
11335 @node Configuration Pragmas
11336 @chapter Configuration Pragmas
11337 @cindex Configuration pragmas
11338 @cindex Pragmas, configuration
11341 Configuration pragmas include those pragmas described as
11342 such in the Ada Reference Manual, as well as
11343 implementation-dependent pragmas that are configuration pragmas.
11344 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11345 for details on these additional GNAT-specific configuration pragmas.
11346 Most notably, the pragma @code{Source_File_Name}, which allows
11347 specifying non-default names for source files, is a configuration
11348 pragma. The following is a complete list of configuration pragmas
11349 recognized by GNAT:
11357 Assume_No_Invalid_Values
11362 Compile_Time_Warning
11364 Component_Alignment
11365 Convention_Identifier
11373 External_Name_Casing
11376 Float_Representation
11389 Priority_Specific_Dispatching
11392 Propagate_Exceptions
11395 Restricted_Run_Time
11397 Restrictions_Warnings
11400 Source_File_Name_Project
11403 Suppress_Exception_Locations
11404 Task_Dispatching_Policy
11410 Wide_Character_Encoding
11415 * Handling of Configuration Pragmas::
11416 * The Configuration Pragmas Files::
11419 @node Handling of Configuration Pragmas
11420 @section Handling of Configuration Pragmas
11422 Configuration pragmas may either appear at the start of a compilation
11423 unit, in which case they apply only to that unit, or they may apply to
11424 all compilations performed in a given compilation environment.
11426 GNAT also provides the @code{gnatchop} utility to provide an automatic
11427 way to handle configuration pragmas following the semantics for
11428 compilations (that is, files with multiple units), described in the RM.
11429 See @ref{Operating gnatchop in Compilation Mode} for details.
11430 However, for most purposes, it will be more convenient to edit the
11431 @file{gnat.adc} file that contains configuration pragmas directly,
11432 as described in the following section.
11434 @node The Configuration Pragmas Files
11435 @section The Configuration Pragmas Files
11436 @cindex @file{gnat.adc}
11439 In GNAT a compilation environment is defined by the current
11440 directory at the time that a compile command is given. This current
11441 directory is searched for a file whose name is @file{gnat.adc}. If
11442 this file is present, it is expected to contain one or more
11443 configuration pragmas that will be applied to the current compilation.
11444 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11447 Configuration pragmas may be entered into the @file{gnat.adc} file
11448 either by running @code{gnatchop} on a source file that consists only of
11449 configuration pragmas, or more conveniently by
11450 direct editing of the @file{gnat.adc} file, which is a standard format
11453 In addition to @file{gnat.adc}, additional files containing configuration
11454 pragmas may be applied to the current compilation using the switch
11455 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11456 contains only configuration pragmas. These configuration pragmas are
11457 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11458 is present and switch @option{-gnatA} is not used).
11460 It is allowed to specify several switches @option{-gnatec}, all of which
11461 will be taken into account.
11463 If you are using project file, a separate mechanism is provided using
11464 project attributes, see @ref{Specifying Configuration Pragmas} for more
11468 Of special interest to GNAT OpenVMS Alpha is the following
11469 configuration pragma:
11471 @smallexample @c ada
11473 pragma Extend_System (Aux_DEC);
11478 In the presence of this pragma, GNAT adds to the definition of the
11479 predefined package SYSTEM all the additional types and subprograms that are
11480 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11483 @node Handling Arbitrary File Naming Conventions Using gnatname
11484 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11485 @cindex Arbitrary File Naming Conventions
11488 * Arbitrary File Naming Conventions::
11489 * Running gnatname::
11490 * Switches for gnatname::
11491 * Examples of gnatname Usage::
11494 @node Arbitrary File Naming Conventions
11495 @section Arbitrary File Naming Conventions
11498 The GNAT compiler must be able to know the source file name of a compilation
11499 unit. When using the standard GNAT default file naming conventions
11500 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11501 does not need additional information.
11504 When the source file names do not follow the standard GNAT default file naming
11505 conventions, the GNAT compiler must be given additional information through
11506 a configuration pragmas file (@pxref{Configuration Pragmas})
11508 When the non-standard file naming conventions are well-defined,
11509 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11510 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11511 if the file naming conventions are irregular or arbitrary, a number
11512 of pragma @code{Source_File_Name} for individual compilation units
11514 To help maintain the correspondence between compilation unit names and
11515 source file names within the compiler,
11516 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11519 @node Running gnatname
11520 @section Running @code{gnatname}
11523 The usual form of the @code{gnatname} command is
11526 @c $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11527 @c @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11528 @c Expanding @ovar macro inline (explanation in macro def comments)
11529 $ gnatname @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]}
11530 @r{[}--and @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]}@r{]}
11534 All of the arguments are optional. If invoked without any argument,
11535 @code{gnatname} will display its usage.
11538 When used with at least one naming pattern, @code{gnatname} will attempt to
11539 find all the compilation units in files that follow at least one of the
11540 naming patterns. To find these compilation units,
11541 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11545 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11546 Each Naming Pattern is enclosed between double quotes (or single
11547 quotes on Windows).
11548 A Naming Pattern is a regular expression similar to the wildcard patterns
11549 used in file names by the Unix shells or the DOS prompt.
11552 @code{gnatname} may be called with several sections of directories/patterns.
11553 Sections are separated by switch @code{--and}. In each section, there must be
11554 at least one pattern. If no directory is specified in a section, the current
11555 directory (or the project directory is @code{-P} is used) is implied.
11556 The options other that the directory switches and the patterns apply globally
11557 even if they are in different sections.
11560 Examples of Naming Patterns are
11569 For a more complete description of the syntax of Naming Patterns,
11570 see the second kind of regular expressions described in @file{g-regexp.ads}
11571 (the ``Glob'' regular expressions).
11574 When invoked with no switch @code{-P}, @code{gnatname} will create a
11575 configuration pragmas file @file{gnat.adc} in the current working directory,
11576 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11579 @node Switches for gnatname
11580 @section Switches for @code{gnatname}
11583 Switches for @code{gnatname} must precede any specified Naming Pattern.
11586 You may specify any of the following switches to @code{gnatname}:
11592 @cindex @option{--version} @command{gnatname}
11593 Display Copyright and version, then exit disregarding all other options.
11596 @cindex @option{--help} @command{gnatname}
11597 If @option{--version} was not used, display usage, then exit disregarding
11601 Start another section of directories/patterns.
11603 @item ^-c^/CONFIG_FILE=^@file{file}
11604 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11605 Create a configuration pragmas file @file{file} (instead of the default
11608 There may be zero, one or more space between @option{-c} and
11611 @file{file} may include directory information. @file{file} must be
11612 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11613 When a switch @option{^-c^/CONFIG_FILE^} is
11614 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11616 @item ^-d^/SOURCE_DIRS=^@file{dir}
11617 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11618 Look for source files in directory @file{dir}. There may be zero, one or more
11619 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11620 When a switch @option{^-d^/SOURCE_DIRS^}
11621 is specified, the current working directory will not be searched for source
11622 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11623 or @option{^-D^/DIR_FILES^} switch.
11624 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11625 If @file{dir} is a relative path, it is relative to the directory of
11626 the configuration pragmas file specified with switch
11627 @option{^-c^/CONFIG_FILE^},
11628 or to the directory of the project file specified with switch
11629 @option{^-P^/PROJECT_FILE^} or,
11630 if neither switch @option{^-c^/CONFIG_FILE^}
11631 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11632 current working directory. The directory
11633 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11635 @item ^-D^/DIRS_FILE=^@file{file}
11636 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11637 Look for source files in all directories listed in text file @file{file}.
11638 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11640 @file{file} must be an existing, readable text file.
11641 Each nonempty line in @file{file} must be a directory.
11642 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11643 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11646 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11647 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11648 Foreign patterns. Using this switch, it is possible to add sources of languages
11649 other than Ada to the list of sources of a project file.
11650 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11653 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11656 will look for Ada units in all files with the @file{.ada} extension,
11657 and will add to the list of file for project @file{prj.gpr} the C files
11658 with extension @file{.^c^C^}.
11661 @cindex @option{^-h^/HELP^} (@code{gnatname})
11662 Output usage (help) information. The output is written to @file{stdout}.
11664 @item ^-P^/PROJECT_FILE=^@file{proj}
11665 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11666 Create or update project file @file{proj}. There may be zero, one or more space
11667 between @option{-P} and @file{proj}. @file{proj} may include directory
11668 information. @file{proj} must be writable.
11669 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11670 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11671 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11673 @item ^-v^/VERBOSE^
11674 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11675 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11676 This includes name of the file written, the name of the directories to search
11677 and, for each file in those directories whose name matches at least one of
11678 the Naming Patterns, an indication of whether the file contains a unit,
11679 and if so the name of the unit.
11681 @item ^-v -v^/VERBOSE /VERBOSE^
11682 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11683 Very Verbose mode. In addition to the output produced in verbose mode,
11684 for each file in the searched directories whose name matches none of
11685 the Naming Patterns, an indication is given that there is no match.
11687 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11688 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11689 Excluded patterns. Using this switch, it is possible to exclude some files
11690 that would match the name patterns. For example,
11692 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11695 will look for Ada units in all files with the @file{.ada} extension,
11696 except those whose names end with @file{_nt.ada}.
11700 @node Examples of gnatname Usage
11701 @section Examples of @code{gnatname} Usage
11705 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11711 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11716 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11717 and be writable. In addition, the directory
11718 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11719 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11722 Note the optional spaces after @option{-c} and @option{-d}.
11727 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11728 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11731 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11732 /EXCLUDED_PATTERN=*_nt_body.ada
11733 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11734 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11738 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11739 even in conjunction with one or several switches
11740 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11741 are used in this example.
11743 @c *****************************************
11744 @c * G N A T P r o j e c t M a n a g e r *
11745 @c *****************************************
11747 @c ------ macros for projects.texi
11748 @c These macros are needed when building the gprbuild documentation, but
11749 @c should have no effect in the gnat user's guide
11751 @macro CODESAMPLE{TXT}
11759 @macro PROJECTFILE{TXT}
11763 @c simulates a newline when in a @CODESAMPLE
11774 @macro TIPHTML{TXT}
11778 @macro IMPORTANT{TXT}
11793 @include projects.texi
11795 @c *****************************************
11796 @c * Cross-referencing tools
11797 @c *****************************************
11799 @node The Cross-Referencing Tools gnatxref and gnatfind
11800 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
11805 The compiler generates cross-referencing information (unless
11806 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
11807 This information indicates where in the source each entity is declared and
11808 referenced. Note that entities in package Standard are not included, but
11809 entities in all other predefined units are included in the output.
11811 Before using any of these two tools, you need to compile successfully your
11812 application, so that GNAT gets a chance to generate the cross-referencing
11815 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
11816 information to provide the user with the capability to easily locate the
11817 declaration and references to an entity. These tools are quite similar,
11818 the difference being that @code{gnatfind} is intended for locating
11819 definitions and/or references to a specified entity or entities, whereas
11820 @code{gnatxref} is oriented to generating a full report of all
11823 To use these tools, you must not compile your application using the
11824 @option{-gnatx} switch on the @command{gnatmake} command line
11825 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
11826 information will not be generated.
11828 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
11829 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
11832 * Switches for gnatxref::
11833 * Switches for gnatfind::
11834 * Project Files for gnatxref and gnatfind::
11835 * Regular Expressions in gnatfind and gnatxref::
11836 * Examples of gnatxref Usage::
11837 * Examples of gnatfind Usage::
11840 @node Switches for gnatxref
11841 @section @code{gnatxref} Switches
11844 The command invocation for @code{gnatxref} is:
11846 @c $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
11847 @c Expanding @ovar macro inline (explanation in macro def comments)
11848 $ gnatxref @r{[}@var{switches}@r{]} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
11857 identifies the source files for which a report is to be generated. The
11858 ``with''ed units will be processed too. You must provide at least one file.
11860 These file names are considered to be regular expressions, so for instance
11861 specifying @file{source*.adb} is the same as giving every file in the current
11862 directory whose name starts with @file{source} and whose extension is
11865 You shouldn't specify any directory name, just base names. @command{gnatxref}
11866 and @command{gnatfind} will be able to locate these files by themselves using
11867 the source path. If you specify directories, no result is produced.
11872 The switches can be:
11876 @cindex @option{--version} @command{gnatxref}
11877 Display Copyright and version, then exit disregarding all other options.
11880 @cindex @option{--help} @command{gnatxref}
11881 If @option{--version} was not used, display usage, then exit disregarding
11884 @item ^-a^/ALL_FILES^
11885 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
11886 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
11887 the read-only files found in the library search path. Otherwise, these files
11888 will be ignored. This option can be used to protect Gnat sources or your own
11889 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
11890 much faster, and their output much smaller. Read-only here refers to access
11891 or permissions status in the file system for the current user.
11894 @cindex @option{-aIDIR} (@command{gnatxref})
11895 When looking for source files also look in directory DIR. The order in which
11896 source file search is undertaken is the same as for @command{gnatmake}.
11899 @cindex @option{-aODIR} (@command{gnatxref})
11900 When searching for library and object files, look in directory
11901 DIR. The order in which library files are searched is the same as for
11902 @command{gnatmake}.
11905 @cindex @option{-nostdinc} (@command{gnatxref})
11906 Do not look for sources in the system default directory.
11909 @cindex @option{-nostdlib} (@command{gnatxref})
11910 Do not look for library files in the system default directory.
11912 @item --ext=@var{extension}
11913 @cindex @option{--ext} (@command{gnatxref})
11914 Specify an alternate ali file extension. The default is @code{ali} and other
11915 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
11916 switch. Note that if this switch overrides the default, which means that only
11917 the new extension will be considered.
11919 @item --RTS=@var{rts-path}
11920 @cindex @option{--RTS} (@command{gnatxref})
11921 Specifies the default location of the runtime library. Same meaning as the
11922 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
11924 @item ^-d^/DERIVED_TYPES^
11925 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
11926 If this switch is set @code{gnatxref} will output the parent type
11927 reference for each matching derived types.
11929 @item ^-f^/FULL_PATHNAME^
11930 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
11931 If this switch is set, the output file names will be preceded by their
11932 directory (if the file was found in the search path). If this switch is
11933 not set, the directory will not be printed.
11935 @item ^-g^/IGNORE_LOCALS^
11936 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
11937 If this switch is set, information is output only for library-level
11938 entities, ignoring local entities. The use of this switch may accelerate
11939 @code{gnatfind} and @code{gnatxref}.
11942 @cindex @option{-IDIR} (@command{gnatxref})
11943 Equivalent to @samp{-aODIR -aIDIR}.
11946 @cindex @option{-pFILE} (@command{gnatxref})
11947 Specify a project file to use @xref{GNAT Project Manager}.
11948 If you need to use the @file{.gpr}
11949 project files, you should use gnatxref through the GNAT driver
11950 (@command{gnat xref -Pproject}).
11952 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
11953 project file in the current directory.
11955 If a project file is either specified or found by the tools, then the content
11956 of the source directory and object directory lines are added as if they
11957 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
11958 and @samp{^-aO^OBJECT_SEARCH^}.
11960 Output only unused symbols. This may be really useful if you give your
11961 main compilation unit on the command line, as @code{gnatxref} will then
11962 display every unused entity and 'with'ed package.
11966 Instead of producing the default output, @code{gnatxref} will generate a
11967 @file{tags} file that can be used by vi. For examples how to use this
11968 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
11969 to the standard output, thus you will have to redirect it to a file.
11975 All these switches may be in any order on the command line, and may even
11976 appear after the file names. They need not be separated by spaces, thus
11977 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
11978 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
11980 @node Switches for gnatfind
11981 @section @code{gnatfind} Switches
11984 The command line for @code{gnatfind} is:
11987 @c $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
11988 @c @r{[}@var{file1} @var{file2} @dots{}]
11989 @c Expanding @ovar macro inline (explanation in macro def comments)
11990 $ gnatfind @r{[}@var{switches}@r{]} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
11991 @r{[}@var{file1} @var{file2} @dots{}@r{]}
11999 An entity will be output only if it matches the regular expression found
12000 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
12002 Omitting the pattern is equivalent to specifying @samp{*}, which
12003 will match any entity. Note that if you do not provide a pattern, you
12004 have to provide both a sourcefile and a line.
12006 Entity names are given in Latin-1, with uppercase/lowercase equivalence
12007 for matching purposes. At the current time there is no support for
12008 8-bit codes other than Latin-1, or for wide characters in identifiers.
12011 @code{gnatfind} will look for references, bodies or declarations
12012 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
12013 and column @var{column}. See @ref{Examples of gnatfind Usage}
12014 for syntax examples.
12017 is a decimal integer identifying the line number containing
12018 the reference to the entity (or entities) to be located.
12021 is a decimal integer identifying the exact location on the
12022 line of the first character of the identifier for the
12023 entity reference. Columns are numbered from 1.
12025 @item file1 file2 @dots{}
12026 The search will be restricted to these source files. If none are given, then
12027 the search will be done for every library file in the search path.
12028 These file must appear only after the pattern or sourcefile.
12030 These file names are considered to be regular expressions, so for instance
12031 specifying @file{source*.adb} is the same as giving every file in the current
12032 directory whose name starts with @file{source} and whose extension is
12035 The location of the spec of the entity will always be displayed, even if it
12036 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
12037 occurrences of the entity in the separate units of the ones given on the
12038 command line will also be displayed.
12040 Note that if you specify at least one file in this part, @code{gnatfind} may
12041 sometimes not be able to find the body of the subprograms.
12046 At least one of 'sourcefile' or 'pattern' has to be present on
12049 The following switches are available:
12053 @cindex @option{--version} @command{gnatfind}
12054 Display Copyright and version, then exit disregarding all other options.
12057 @cindex @option{--help} @command{gnatfind}
12058 If @option{--version} was not used, display usage, then exit disregarding
12061 @item ^-a^/ALL_FILES^
12062 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
12063 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
12064 the read-only files found in the library search path. Otherwise, these files
12065 will be ignored. This option can be used to protect Gnat sources or your own
12066 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
12067 much faster, and their output much smaller. Read-only here refers to access
12068 or permission status in the file system for the current user.
12071 @cindex @option{-aIDIR} (@command{gnatfind})
12072 When looking for source files also look in directory DIR. The order in which
12073 source file search is undertaken is the same as for @command{gnatmake}.
12076 @cindex @option{-aODIR} (@command{gnatfind})
12077 When searching for library and object files, look in directory
12078 DIR. The order in which library files are searched is the same as for
12079 @command{gnatmake}.
12082 @cindex @option{-nostdinc} (@command{gnatfind})
12083 Do not look for sources in the system default directory.
12086 @cindex @option{-nostdlib} (@command{gnatfind})
12087 Do not look for library files in the system default directory.
12089 @item --ext=@var{extension}
12090 @cindex @option{--ext} (@command{gnatfind})
12091 Specify an alternate ali file extension. The default is @code{ali} and other
12092 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
12093 switch. Note that if this switch overrides the default, which means that only
12094 the new extension will be considered.
12096 @item --RTS=@var{rts-path}
12097 @cindex @option{--RTS} (@command{gnatfind})
12098 Specifies the default location of the runtime library. Same meaning as the
12099 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
12101 @item ^-d^/DERIVED_TYPE_INFORMATION^
12102 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
12103 If this switch is set, then @code{gnatfind} will output the parent type
12104 reference for each matching derived types.
12106 @item ^-e^/EXPRESSIONS^
12107 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
12108 By default, @code{gnatfind} accept the simple regular expression set for
12109 @samp{pattern}. If this switch is set, then the pattern will be
12110 considered as full Unix-style regular expression.
12112 @item ^-f^/FULL_PATHNAME^
12113 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
12114 If this switch is set, the output file names will be preceded by their
12115 directory (if the file was found in the search path). If this switch is
12116 not set, the directory will not be printed.
12118 @item ^-g^/IGNORE_LOCALS^
12119 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
12120 If this switch is set, information is output only for library-level
12121 entities, ignoring local entities. The use of this switch may accelerate
12122 @code{gnatfind} and @code{gnatxref}.
12125 @cindex @option{-IDIR} (@command{gnatfind})
12126 Equivalent to @samp{-aODIR -aIDIR}.
12129 @cindex @option{-pFILE} (@command{gnatfind})
12130 Specify a project file (@pxref{GNAT Project Manager}) to use.
12131 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
12132 project file in the current directory.
12134 If a project file is either specified or found by the tools, then the content
12135 of the source directory and object directory lines are added as if they
12136 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
12137 @samp{^-aO^/OBJECT_SEARCH^}.
12139 @item ^-r^/REFERENCES^
12140 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
12141 By default, @code{gnatfind} will output only the information about the
12142 declaration, body or type completion of the entities. If this switch is
12143 set, the @code{gnatfind} will locate every reference to the entities in
12144 the files specified on the command line (or in every file in the search
12145 path if no file is given on the command line).
12147 @item ^-s^/PRINT_LINES^
12148 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
12149 If this switch is set, then @code{gnatfind} will output the content
12150 of the Ada source file lines were the entity was found.
12152 @item ^-t^/TYPE_HIERARCHY^
12153 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
12154 If this switch is set, then @code{gnatfind} will output the type hierarchy for
12155 the specified type. It act like -d option but recursively from parent
12156 type to parent type. When this switch is set it is not possible to
12157 specify more than one file.
12162 All these switches may be in any order on the command line, and may even
12163 appear after the file names. They need not be separated by spaces, thus
12164 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
12165 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
12167 As stated previously, gnatfind will search in every directory in the
12168 search path. You can force it to look only in the current directory if
12169 you specify @code{*} at the end of the command line.
12171 @node Project Files for gnatxref and gnatfind
12172 @section Project Files for @command{gnatxref} and @command{gnatfind}
12175 Project files allow a programmer to specify how to compile its
12176 application, where to find sources, etc. These files are used
12178 primarily by GPS, but they can also be used
12181 @code{gnatxref} and @code{gnatfind}.
12183 A project file name must end with @file{.gpr}. If a single one is
12184 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
12185 extract the information from it. If multiple project files are found, none of
12186 them is read, and you have to use the @samp{-p} switch to specify the one
12189 The following lines can be included, even though most of them have default
12190 values which can be used in most cases.
12191 The lines can be entered in any order in the file.
12192 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
12193 each line. If you have multiple instances, only the last one is taken into
12198 [default: @code{"^./^[]^"}]
12199 specifies a directory where to look for source files. Multiple @code{src_dir}
12200 lines can be specified and they will be searched in the order they
12204 [default: @code{"^./^[]^"}]
12205 specifies a directory where to look for object and library files. Multiple
12206 @code{obj_dir} lines can be specified, and they will be searched in the order
12209 @item comp_opt=SWITCHES
12210 [default: @code{""}]
12211 creates a variable which can be referred to subsequently by using
12212 the @code{$@{comp_opt@}} notation. This is intended to store the default
12213 switches given to @command{gnatmake} and @command{gcc}.
12215 @item bind_opt=SWITCHES
12216 [default: @code{""}]
12217 creates a variable which can be referred to subsequently by using
12218 the @samp{$@{bind_opt@}} notation. This is intended to store the default
12219 switches given to @command{gnatbind}.
12221 @item link_opt=SWITCHES
12222 [default: @code{""}]
12223 creates a variable which can be referred to subsequently by using
12224 the @samp{$@{link_opt@}} notation. This is intended to store the default
12225 switches given to @command{gnatlink}.
12227 @item main=EXECUTABLE
12228 [default: @code{""}]
12229 specifies the name of the executable for the application. This variable can
12230 be referred to in the following lines by using the @samp{$@{main@}} notation.
12233 @item comp_cmd=COMMAND
12234 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
12237 @item comp_cmd=COMMAND
12238 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
12240 specifies the command used to compile a single file in the application.
12243 @item make_cmd=COMMAND
12244 [default: @code{"GNAT MAKE $@{main@}
12245 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
12246 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
12247 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
12250 @item make_cmd=COMMAND
12251 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
12252 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
12253 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
12255 specifies the command used to recompile the whole application.
12257 @item run_cmd=COMMAND
12258 [default: @code{"$@{main@}"}]
12259 specifies the command used to run the application.
12261 @item debug_cmd=COMMAND
12262 [default: @code{"gdb $@{main@}"}]
12263 specifies the command used to debug the application
12268 @command{gnatxref} and @command{gnatfind} only take into account the
12269 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
12271 @node Regular Expressions in gnatfind and gnatxref
12272 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
12275 As specified in the section about @command{gnatfind}, the pattern can be a
12276 regular expression. Actually, there are to set of regular expressions
12277 which are recognized by the program:
12280 @item globbing patterns
12281 These are the most usual regular expression. They are the same that you
12282 generally used in a Unix shell command line, or in a DOS session.
12284 Here is a more formal grammar:
12291 term ::= elmt -- matches elmt
12292 term ::= elmt elmt -- concatenation (elmt then elmt)
12293 term ::= * -- any string of 0 or more characters
12294 term ::= ? -- matches any character
12295 term ::= [char @{char@}] -- matches any character listed
12296 term ::= [char - char] -- matches any character in range
12300 @item full regular expression
12301 The second set of regular expressions is much more powerful. This is the
12302 type of regular expressions recognized by utilities such a @file{grep}.
12304 The following is the form of a regular expression, expressed in Ada
12305 reference manual style BNF is as follows
12312 regexp ::= term @{| term@} -- alternation (term or term @dots{})
12314 term ::= item @{item@} -- concatenation (item then item)
12316 item ::= elmt -- match elmt
12317 item ::= elmt * -- zero or more elmt's
12318 item ::= elmt + -- one or more elmt's
12319 item ::= elmt ? -- matches elmt or nothing
12322 elmt ::= nschar -- matches given character
12323 elmt ::= [nschar @{nschar@}] -- matches any character listed
12324 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
12325 elmt ::= [char - char] -- matches chars in given range
12326 elmt ::= \ char -- matches given character
12327 elmt ::= . -- matches any single character
12328 elmt ::= ( regexp ) -- parens used for grouping
12330 char ::= any character, including special characters
12331 nschar ::= any character except ()[].*+?^^^
12335 Following are a few examples:
12339 will match any of the two strings @samp{abcde} and @samp{fghi},
12342 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
12343 @samp{abcccd}, and so on,
12346 will match any string which has only lowercase characters in it (and at
12347 least one character.
12352 @node Examples of gnatxref Usage
12353 @section Examples of @code{gnatxref} Usage
12355 @subsection General Usage
12358 For the following examples, we will consider the following units:
12360 @smallexample @c ada
12366 3: procedure Foo (B : in Integer);
12373 1: package body Main is
12374 2: procedure Foo (B : in Integer) is
12385 2: procedure Print (B : Integer);
12394 The first thing to do is to recompile your application (for instance, in
12395 that case just by doing a @samp{gnatmake main}, so that GNAT generates
12396 the cross-referencing information.
12397 You can then issue any of the following commands:
12399 @item gnatxref main.adb
12400 @code{gnatxref} generates cross-reference information for main.adb
12401 and every unit 'with'ed by main.adb.
12403 The output would be:
12411 Decl: main.ads 3:20
12412 Body: main.adb 2:20
12413 Ref: main.adb 4:13 5:13 6:19
12416 Ref: main.adb 6:8 7:8
12426 Decl: main.ads 3:15
12427 Body: main.adb 2:15
12430 Body: main.adb 1:14
12433 Ref: main.adb 6:12 7:12
12437 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
12438 its body is in main.adb, line 1, column 14 and is not referenced any where.
12440 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
12441 it referenced in main.adb, line 6 column 12 and line 7 column 12.
12443 @item gnatxref package1.adb package2.ads
12444 @code{gnatxref} will generates cross-reference information for
12445 package1.adb, package2.ads and any other package 'with'ed by any
12451 @subsection Using gnatxref with vi
12453 @code{gnatxref} can generate a tags file output, which can be used
12454 directly from @command{vi}. Note that the standard version of @command{vi}
12455 will not work properly with overloaded symbols. Consider using another
12456 free implementation of @command{vi}, such as @command{vim}.
12459 $ gnatxref -v gnatfind.adb > tags
12463 will generate the tags file for @code{gnatfind} itself (if the sources
12464 are in the search path!).
12466 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
12467 (replacing @var{entity} by whatever you are looking for), and vi will
12468 display a new file with the corresponding declaration of entity.
12471 @node Examples of gnatfind Usage
12472 @section Examples of @code{gnatfind} Usage
12476 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
12477 Find declarations for all entities xyz referenced at least once in
12478 main.adb. The references are search in every library file in the search
12481 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
12484 The output will look like:
12486 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
12487 ^directory/^[directory]^main.adb:24:10: xyz <= body
12488 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
12492 that is to say, one of the entities xyz found in main.adb is declared at
12493 line 12 of main.ads (and its body is in main.adb), and another one is
12494 declared at line 45 of foo.ads
12496 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
12497 This is the same command as the previous one, instead @code{gnatfind} will
12498 display the content of the Ada source file lines.
12500 The output will look like:
12503 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
12505 ^directory/^[directory]^main.adb:24:10: xyz <= body
12507 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
12512 This can make it easier to find exactly the location your are looking
12515 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
12516 Find references to all entities containing an x that are
12517 referenced on line 123 of main.ads.
12518 The references will be searched only in main.ads and foo.adb.
12520 @item gnatfind main.ads:123
12521 Find declarations and bodies for all entities that are referenced on
12522 line 123 of main.ads.
12524 This is the same as @code{gnatfind "*":main.adb:123}.
12526 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
12527 Find the declaration for the entity referenced at column 45 in
12528 line 123 of file main.adb in directory mydir. Note that it
12529 is usual to omit the identifier name when the column is given,
12530 since the column position identifies a unique reference.
12532 The column has to be the beginning of the identifier, and should not
12533 point to any character in the middle of the identifier.
12537 @c *********************************
12538 @node The GNAT Pretty-Printer gnatpp
12539 @chapter The GNAT Pretty-Printer @command{gnatpp}
12541 @cindex Pretty-Printer
12544 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
12545 for source reformatting / pretty-printing.
12546 It takes an Ada source file as input and generates a reformatted
12548 You can specify various style directives via switches; e.g.,
12549 identifier case conventions, rules of indentation, and comment layout.
12551 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
12552 tree for the input source and thus requires the input to be syntactically and
12553 semantically legal.
12554 If this condition is not met, @command{gnatpp} will terminate with an
12555 error message; no output file will be generated.
12557 If the source files presented to @command{gnatpp} contain
12558 preprocessing directives, then the output file will
12559 correspond to the generated source after all
12560 preprocessing is carried out. There is no way
12561 using @command{gnatpp} to obtain pretty printed files that
12562 include the preprocessing directives.
12564 If the compilation unit
12565 contained in the input source depends semantically upon units located
12566 outside the current directory, you have to provide the source search path
12567 when invoking @command{gnatpp}, if these units are contained in files with
12568 names that do not follow the GNAT file naming rules, you have to provide
12569 the configuration file describing the corresponding naming scheme;
12570 see the description of the @command{gnatpp}
12571 switches below. Another possibility is to use a project file and to
12572 call @command{gnatpp} through the @command{gnat} driver
12574 The @command{gnatpp} command has the form
12577 @c $ gnatpp @ovar{switches} @var{filename}
12578 @c Expanding @ovar macro inline (explanation in macro def comments)
12579 $ gnatpp @r{[}@var{switches}@r{]} @var{filename} @r{[}-cargs @var{gcc_switches}@r{]}
12586 @var{switches} is an optional sequence of switches defining such properties as
12587 the formatting rules, the source search path, and the destination for the
12591 @var{filename} is the name (including the extension) of the source file to
12592 reformat; ``wildcards'' or several file names on the same gnatpp command are
12593 allowed. The file name may contain path information; it does not have to
12594 follow the GNAT file naming rules
12597 @samp{@var{gcc_switches}} is a list of switches for
12598 @command{gcc}. They will be passed on to all compiler invocations made by
12599 @command{gnatelim} to generate the ASIS trees. Here you can provide
12600 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
12601 use the @option{-gnatec} switch to set the configuration file etc.
12605 * Switches for gnatpp::
12606 * Formatting Rules::
12609 @node Switches for gnatpp
12610 @section Switches for @command{gnatpp}
12613 The following subsections describe the various switches accepted by
12614 @command{gnatpp}, organized by category.
12617 You specify a switch by supplying a name and generally also a value.
12618 In many cases the values for a switch with a given name are incompatible with
12620 (for example the switch that controls the casing of a reserved word may have
12621 exactly one value: upper case, lower case, or
12622 mixed case) and thus exactly one such switch can be in effect for an
12623 invocation of @command{gnatpp}.
12624 If more than one is supplied, the last one is used.
12625 However, some values for the same switch are mutually compatible.
12626 You may supply several such switches to @command{gnatpp}, but then
12627 each must be specified in full, with both the name and the value.
12628 Abbreviated forms (the name appearing once, followed by each value) are
12630 For example, to set
12631 the alignment of the assignment delimiter both in declarations and in
12632 assignment statements, you must write @option{-A2A3}
12633 (or @option{-A2 -A3}), but not @option{-A23}.
12637 In many cases the set of options for a given qualifier are incompatible with
12638 each other (for example the qualifier that controls the casing of a reserved
12639 word may have exactly one option, which specifies either upper case, lower
12640 case, or mixed case), and thus exactly one such option can be in effect for
12641 an invocation of @command{gnatpp}.
12642 If more than one is supplied, the last one is used.
12643 However, some qualifiers have options that are mutually compatible,
12644 and then you may then supply several such options when invoking
12648 In most cases, it is obvious whether or not the
12649 ^values for a switch with a given name^options for a given qualifier^
12650 are compatible with each other.
12651 When the semantics might not be evident, the summaries below explicitly
12652 indicate the effect.
12655 * Alignment Control::
12657 * Construct Layout Control::
12658 * General Text Layout Control::
12659 * Other Formatting Options::
12660 * Setting the Source Search Path::
12661 * Output File Control::
12662 * Other gnatpp Switches::
12665 @node Alignment Control
12666 @subsection Alignment Control
12667 @cindex Alignment control in @command{gnatpp}
12670 Programs can be easier to read if certain constructs are vertically aligned.
12671 By default all alignments are set ON.
12672 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
12673 OFF, and then use one or more of the other
12674 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
12675 to activate alignment for specific constructs.
12678 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
12682 Set all alignments to ON
12685 @item ^-A0^/ALIGN=OFF^
12686 Set all alignments to OFF
12688 @item ^-A1^/ALIGN=COLONS^
12689 Align @code{:} in declarations
12691 @item ^-A2^/ALIGN=DECLARATIONS^
12692 Align @code{:=} in initializations in declarations
12694 @item ^-A3^/ALIGN=STATEMENTS^
12695 Align @code{:=} in assignment statements
12697 @item ^-A4^/ALIGN=ARROWS^
12698 Align @code{=>} in associations
12700 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
12701 Align @code{at} keywords in the component clauses in record
12702 representation clauses
12706 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
12709 @node Casing Control
12710 @subsection Casing Control
12711 @cindex Casing control in @command{gnatpp}
12714 @command{gnatpp} allows you to specify the casing for reserved words,
12715 pragma names, attribute designators and identifiers.
12716 For identifiers you may define a
12717 general rule for name casing but also override this rule
12718 via a set of dictionary files.
12720 Three types of casing are supported: lower case, upper case, and mixed case.
12721 Lower and upper case are self-explanatory (but since some letters in
12722 Latin1 and other GNAT-supported character sets
12723 exist only in lower-case form, an upper case conversion will have no
12725 ``Mixed case'' means that the first letter, and also each letter immediately
12726 following an underscore, are converted to their uppercase forms;
12727 all the other letters are converted to their lowercase forms.
12730 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
12731 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
12732 Attribute designators are lower case
12734 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
12735 Attribute designators are upper case
12737 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
12738 Attribute designators are mixed case (this is the default)
12740 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
12741 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
12742 Keywords (technically, these are known in Ada as @emph{reserved words}) are
12743 lower case (this is the default)
12745 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
12746 Keywords are upper case
12748 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
12749 @item ^-nD^/NAME_CASING=AS_DECLARED^
12750 Name casing for defining occurrences are as they appear in the source file
12751 (this is the default)
12753 @item ^-nU^/NAME_CASING=UPPER_CASE^
12754 Names are in upper case
12756 @item ^-nL^/NAME_CASING=LOWER_CASE^
12757 Names are in lower case
12759 @item ^-nM^/NAME_CASING=MIXED_CASE^
12760 Names are in mixed case
12762 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
12763 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
12764 Pragma names are lower case
12766 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
12767 Pragma names are upper case
12769 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
12770 Pragma names are mixed case (this is the default)
12772 @item ^-D@var{file}^/DICTIONARY=@var{file}^
12773 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
12774 Use @var{file} as a @emph{dictionary file} that defines
12775 the casing for a set of specified names,
12776 thereby overriding the effect on these names by
12777 any explicit or implicit
12778 ^-n^/NAME_CASING^ switch.
12779 To supply more than one dictionary file,
12780 use ^several @option{-D} switches^a list of files as options^.
12783 @option{gnatpp} implicitly uses a @emph{default dictionary file}
12784 to define the casing for the Ada predefined names and
12785 the names declared in the GNAT libraries.
12787 @item ^-D-^/SPECIFIC_CASING^
12788 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
12789 Do not use the default dictionary file;
12790 instead, use the casing
12791 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
12796 The structure of a dictionary file, and details on the conventions
12797 used in the default dictionary file, are defined in @ref{Name Casing}.
12799 The @option{^-D-^/SPECIFIC_CASING^} and
12800 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
12803 @node Construct Layout Control
12804 @subsection Construct Layout Control
12805 @cindex Layout control in @command{gnatpp}
12808 This group of @command{gnatpp} switches controls the layout of comments and
12809 complex syntactic constructs. See @ref{Formatting Comments} for details
12813 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
12814 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
12815 All the comments remain unchanged
12817 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
12818 GNAT-style comment line indentation (this is the default).
12820 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
12821 Reference-manual comment line indentation.
12823 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
12824 GNAT-style comment beginning
12826 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
12827 Reformat comment blocks
12829 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
12830 Keep unchanged special form comments
12832 Reformat comment blocks
12834 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
12835 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
12836 GNAT-style layout (this is the default)
12838 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
12841 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
12844 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
12846 All the VT characters are removed from the comment text. All the HT characters
12847 are expanded with the sequences of space characters to get to the next tab
12850 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
12851 @item ^--no-separate-is^/NO_SEPARATE_IS^
12852 Do not place the keyword @code{is} on a separate line in a subprogram body in
12853 case if the spec occupies more then one line.
12855 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
12856 @item ^--separate-label^/SEPARATE_LABEL^
12857 Place statement label(s) on a separate line, with the following statement
12860 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
12861 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
12862 Place the keyword @code{loop} in FOR and WHILE loop statements and the
12863 keyword @code{then} in IF statements on a separate line.
12865 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
12866 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
12867 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
12868 keyword @code{then} in IF statements on a separate line. This option is
12869 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
12871 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
12872 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
12873 Start each USE clause in a context clause from a separate line.
12875 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
12876 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
12877 Use a separate line for a loop or block statement name, but do not use an extra
12878 indentation level for the statement itself.
12884 The @option{-c1} and @option{-c2} switches are incompatible.
12885 The @option{-c3} and @option{-c4} switches are compatible with each other and
12886 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
12887 the other comment formatting switches.
12889 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
12894 For the @option{/COMMENTS_LAYOUT} qualifier:
12897 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
12899 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
12900 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
12904 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
12905 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
12908 @node General Text Layout Control
12909 @subsection General Text Layout Control
12912 These switches allow control over line length and indentation.
12915 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
12916 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
12917 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
12919 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
12920 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
12921 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
12923 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
12924 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
12925 Indentation level for continuation lines (relative to the line being
12926 continued), @var{nnn} from 1@dots{}9.
12928 value is one less then the (normal) indentation level, unless the
12929 indentation is set to 1 (in which case the default value for continuation
12930 line indentation is also 1)
12933 @node Other Formatting Options
12934 @subsection Other Formatting Options
12937 These switches control the inclusion of missing end/exit labels, and
12938 the indentation level in @b{case} statements.
12941 @item ^-e^/NO_MISSED_LABELS^
12942 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
12943 Do not insert missing end/exit labels. An end label is the name of
12944 a construct that may optionally be repeated at the end of the
12945 construct's declaration;
12946 e.g., the names of packages, subprograms, and tasks.
12947 An exit label is the name of a loop that may appear as target
12948 of an exit statement within the loop.
12949 By default, @command{gnatpp} inserts these end/exit labels when
12950 they are absent from the original source. This option suppresses such
12951 insertion, so that the formatted source reflects the original.
12953 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
12954 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
12955 Insert a Form Feed character after a pragma Page.
12957 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
12958 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
12959 Do not use an additional indentation level for @b{case} alternatives
12960 and variants if there are @var{nnn} or more (the default
12962 If @var{nnn} is 0, an additional indentation level is
12963 used for @b{case} alternatives and variants regardless of their number.
12966 @node Setting the Source Search Path
12967 @subsection Setting the Source Search Path
12970 To define the search path for the input source file, @command{gnatpp}
12971 uses the same switches as the GNAT compiler, with the same effects.
12974 @item ^-I^/SEARCH=^@var{dir}
12975 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
12976 The same as the corresponding gcc switch
12978 @item ^-I-^/NOCURRENT_DIRECTORY^
12979 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
12980 The same as the corresponding gcc switch
12982 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
12983 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
12984 The same as the corresponding gcc switch
12986 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
12987 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
12988 The same as the corresponding gcc switch
12992 @node Output File Control
12993 @subsection Output File Control
12996 By default the output is sent to the file whose name is obtained by appending
12997 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
12998 (if the file with this name already exists, it is unconditionally overwritten).
12999 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
13000 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
13002 The output may be redirected by the following switches:
13005 @item ^-pipe^/STANDARD_OUTPUT^
13006 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
13007 Send the output to @code{Standard_Output}
13009 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
13010 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
13011 Write the output into @var{output_file}.
13012 If @var{output_file} already exists, @command{gnatpp} terminates without
13013 reading or processing the input file.
13015 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
13016 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
13017 Write the output into @var{output_file}, overwriting the existing file
13018 (if one is present).
13020 @item ^-r^/REPLACE^
13021 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
13022 Replace the input source file with the reformatted output, and copy the
13023 original input source into the file whose name is obtained by appending the
13024 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
13025 If a file with this name already exists, @command{gnatpp} terminates without
13026 reading or processing the input file.
13028 @item ^-rf^/OVERRIDING_REPLACE^
13029 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
13030 Like @option{^-r^/REPLACE^} except that if the file with the specified name
13031 already exists, it is overwritten.
13033 @item ^-rnb^/REPLACE_NO_BACKUP^
13034 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
13035 Replace the input source file with the reformatted output without
13036 creating any backup copy of the input source.
13038 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
13039 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
13040 Specifies the format of the reformatted output file. The @var{xxx}
13041 ^string specified with the switch^option^ may be either
13043 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
13044 @item ``@option{^crlf^CRLF^}''
13045 the same as @option{^crlf^CRLF^}
13046 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
13047 @item ``@option{^lf^LF^}''
13048 the same as @option{^unix^UNIX^}
13051 @item ^-W^/RESULT_ENCODING=^@var{e}
13052 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
13053 Specify the wide character encoding method used to write the code in the
13055 @var{e} is one of the following:
13063 Upper half encoding
13065 @item ^s^SHIFT_JIS^
13075 Brackets encoding (default value)
13081 Options @option{^-pipe^/STANDARD_OUTPUT^},
13082 @option{^-o^/OUTPUT^} and
13083 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
13084 contains only one file to reformat.
13086 @option{^--eol^/END_OF_LINE^}
13088 @option{^-W^/RESULT_ENCODING^}
13089 cannot be used together
13090 with @option{^-pipe^/STANDARD_OUTPUT^} option.
13092 @node Other gnatpp Switches
13093 @subsection Other @code{gnatpp} Switches
13096 The additional @command{gnatpp} switches are defined in this subsection.
13099 @item ^-files @var{filename}^/FILES=@var{filename}^
13100 @cindex @option{^-files^/FILES^} (@code{gnatpp})
13101 Take the argument source files from the specified file. This file should be an
13102 ordinary text file containing file names separated by spaces or
13103 line breaks. You can use this switch more than once in the same call to
13104 @command{gnatpp}. You also can combine this switch with an explicit list of
13107 @item ^-v^/VERBOSE^
13108 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
13110 @command{gnatpp} generates version information and then
13111 a trace of the actions it takes to produce or obtain the ASIS tree.
13113 @item ^-w^/WARNINGS^
13114 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
13116 @command{gnatpp} generates a warning whenever it cannot provide
13117 a required layout in the result source.
13120 @node Formatting Rules
13121 @section Formatting Rules
13124 The following subsections show how @command{gnatpp} treats ``white space'',
13125 comments, program layout, and name casing.
13126 They provide the detailed descriptions of the switches shown above.
13129 * White Space and Empty Lines::
13130 * Formatting Comments::
13131 * Construct Layout::
13135 @node White Space and Empty Lines
13136 @subsection White Space and Empty Lines
13139 @command{gnatpp} does not have an option to control space characters.
13140 It will add or remove spaces according to the style illustrated by the
13141 examples in the @cite{Ada Reference Manual}.
13143 The only format effectors
13144 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
13145 that will appear in the output file are platform-specific line breaks,
13146 and also format effectors within (but not at the end of) comments.
13147 In particular, each horizontal tab character that is not inside
13148 a comment will be treated as a space and thus will appear in the
13149 output file as zero or more spaces depending on
13150 the reformatting of the line in which it appears.
13151 The only exception is a Form Feed character, which is inserted after a
13152 pragma @code{Page} when @option{-ff} is set.
13154 The output file will contain no lines with trailing ``white space'' (spaces,
13157 Empty lines in the original source are preserved
13158 only if they separate declarations or statements.
13159 In such contexts, a
13160 sequence of two or more empty lines is replaced by exactly one empty line.
13161 Note that a blank line will be removed if it separates two ``comment blocks''
13162 (a comment block is a sequence of whole-line comments).
13163 In order to preserve a visual separation between comment blocks, use an
13164 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
13165 Likewise, if for some reason you wish to have a sequence of empty lines,
13166 use a sequence of empty comments instead.
13168 @node Formatting Comments
13169 @subsection Formatting Comments
13172 Comments in Ada code are of two kinds:
13175 a @emph{whole-line comment}, which appears by itself (possibly preceded by
13176 ``white space'') on a line
13179 an @emph{end-of-line comment}, which follows some other Ada lexical element
13184 The indentation of a whole-line comment is that of either
13185 the preceding or following line in
13186 the formatted source, depending on switch settings as will be described below.
13188 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
13189 between the end of the preceding Ada lexical element and the beginning
13190 of the comment as appear in the original source,
13191 unless either the comment has to be split to
13192 satisfy the line length limitation, or else the next line contains a
13193 whole line comment that is considered a continuation of this end-of-line
13194 comment (because it starts at the same position).
13196 cases, the start of the end-of-line comment is moved right to the nearest
13197 multiple of the indentation level.
13198 This may result in a ``line overflow'' (the right-shifted comment extending
13199 beyond the maximum line length), in which case the comment is split as
13202 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
13203 (GNAT-style comment line indentation)
13204 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
13205 (reference-manual comment line indentation).
13206 With reference-manual style, a whole-line comment is indented as if it
13207 were a declaration or statement at the same place
13208 (i.e., according to the indentation of the preceding line(s)).
13209 With GNAT style, a whole-line comment that is immediately followed by an
13210 @b{if} or @b{case} statement alternative, a record variant, or the reserved
13211 word @b{begin}, is indented based on the construct that follows it.
13214 @smallexample @c ada
13226 Reference-manual indentation produces:
13228 @smallexample @c ada
13240 while GNAT-style indentation produces:
13242 @smallexample @c ada
13254 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
13255 (GNAT style comment beginning) has the following
13260 For each whole-line comment that does not end with two hyphens,
13261 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
13262 to ensure that there are at least two spaces between these hyphens and the
13263 first non-blank character of the comment.
13267 For an end-of-line comment, if in the original source the next line is a
13268 whole-line comment that starts at the same position
13269 as the end-of-line comment,
13270 then the whole-line comment (and all whole-line comments
13271 that follow it and that start at the same position)
13272 will start at this position in the output file.
13275 That is, if in the original source we have:
13277 @smallexample @c ada
13280 A := B + C; -- B must be in the range Low1..High1
13281 -- C must be in the range Low2..High2
13282 --B+C will be in the range Low1+Low2..High1+High2
13288 Then in the formatted source we get
13290 @smallexample @c ada
13293 A := B + C; -- B must be in the range Low1..High1
13294 -- C must be in the range Low2..High2
13295 -- B+C will be in the range Low1+Low2..High1+High2
13301 A comment that exceeds the line length limit will be split.
13303 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
13304 the line belongs to a reformattable block, splitting the line generates a
13305 @command{gnatpp} warning.
13306 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
13307 comments may be reformatted in typical
13308 word processor style (that is, moving words between lines and putting as
13309 many words in a line as possible).
13312 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
13313 that has a special format (that is, a character that is neither a letter nor digit
13314 not white space nor line break immediately following the leading @code{--} of
13315 the comment) should be without any change moved from the argument source
13316 into reformatted source. This switch allows to preserve comments that are used
13317 as a special marks in the code (e.g.@: SPARK annotation).
13319 @node Construct Layout
13320 @subsection Construct Layout
13323 In several cases the suggested layout in the Ada Reference Manual includes
13324 an extra level of indentation that many programmers prefer to avoid. The
13325 affected cases include:
13329 @item Record type declaration (RM 3.8)
13331 @item Record representation clause (RM 13.5.1)
13333 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
13335 @item Block statement in case if a block has a statement identifier (RM 5.6)
13339 In compact mode (when GNAT style layout or compact layout is set),
13340 the pretty printer uses one level of indentation instead
13341 of two. This is achieved in the record definition and record representation
13342 clause cases by putting the @code{record} keyword on the same line as the
13343 start of the declaration or representation clause, and in the block and loop
13344 case by putting the block or loop header on the same line as the statement
13348 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
13349 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
13350 layout on the one hand, and uncompact layout
13351 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
13352 can be illustrated by the following examples:
13356 @multitable @columnfractions .5 .5
13357 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
13360 @smallexample @c ada
13367 @smallexample @c ada
13376 @smallexample @c ada
13378 a at 0 range 0 .. 31;
13379 b at 4 range 0 .. 31;
13383 @smallexample @c ada
13386 a at 0 range 0 .. 31;
13387 b at 4 range 0 .. 31;
13392 @smallexample @c ada
13400 @smallexample @c ada
13410 @smallexample @c ada
13411 Clear : for J in 1 .. 10 loop
13416 @smallexample @c ada
13418 for J in 1 .. 10 loop
13429 GNAT style, compact layout Uncompact layout
13431 type q is record type q is
13432 a : integer; record
13433 b : integer; a : integer;
13434 end record; b : integer;
13437 for q use record for q use
13438 a at 0 range 0 .. 31; record
13439 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
13440 end record; b at 4 range 0 .. 31;
13443 Block : declare Block :
13444 A : Integer := 3; declare
13445 begin A : Integer := 3;
13447 end Block; Proc (A, A);
13450 Clear : for J in 1 .. 10 loop Clear :
13451 A (J) := 0; for J in 1 .. 10 loop
13452 end loop Clear; A (J) := 0;
13459 A further difference between GNAT style layout and compact layout is that
13460 GNAT style layout inserts empty lines as separation for
13461 compound statements, return statements and bodies.
13463 Note that the layout specified by
13464 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
13465 for named block and loop statements overrides the layout defined by these
13466 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
13467 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
13468 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
13471 @subsection Name Casing
13474 @command{gnatpp} always converts the usage occurrence of a (simple) name to
13475 the same casing as the corresponding defining identifier.
13477 You control the casing for defining occurrences via the
13478 @option{^-n^/NAME_CASING^} switch.
13480 With @option{-nD} (``as declared'', which is the default),
13483 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
13485 defining occurrences appear exactly as in the source file
13486 where they are declared.
13487 The other ^values for this switch^options for this qualifier^ ---
13488 @option{^-nU^UPPER_CASE^},
13489 @option{^-nL^LOWER_CASE^},
13490 @option{^-nM^MIXED_CASE^} ---
13492 ^upper, lower, or mixed case, respectively^the corresponding casing^.
13493 If @command{gnatpp} changes the casing of a defining
13494 occurrence, it analogously changes the casing of all the
13495 usage occurrences of this name.
13497 If the defining occurrence of a name is not in the source compilation unit
13498 currently being processed by @command{gnatpp}, the casing of each reference to
13499 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
13500 switch (subject to the dictionary file mechanism described below).
13501 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
13503 casing for the defining occurrence of the name.
13505 Some names may need to be spelled with casing conventions that are not
13506 covered by the upper-, lower-, and mixed-case transformations.
13507 You can arrange correct casing by placing such names in a
13508 @emph{dictionary file},
13509 and then supplying a @option{^-D^/DICTIONARY^} switch.
13510 The casing of names from dictionary files overrides
13511 any @option{^-n^/NAME_CASING^} switch.
13513 To handle the casing of Ada predefined names and the names from GNAT libraries,
13514 @command{gnatpp} assumes a default dictionary file.
13515 The name of each predefined entity is spelled with the same casing as is used
13516 for the entity in the @cite{Ada Reference Manual}.
13517 The name of each entity in the GNAT libraries is spelled with the same casing
13518 as is used in the declaration of that entity.
13520 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
13521 default dictionary file.
13522 Instead, the casing for predefined and GNAT-defined names will be established
13523 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
13524 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
13525 will appear as just shown,
13526 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
13527 To ensure that even such names are rendered in uppercase,
13528 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
13529 (or else, less conveniently, place these names in upper case in a dictionary
13532 A dictionary file is
13533 a plain text file; each line in this file can be either a blank line
13534 (containing only space characters and ASCII.HT characters), an Ada comment
13535 line, or the specification of exactly one @emph{casing schema}.
13537 A casing schema is a string that has the following syntax:
13541 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
13543 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
13548 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
13549 @var{identifier} lexical element and the @var{letter_or_digit} category.)
13551 The casing schema string can be followed by white space and/or an Ada-style
13552 comment; any amount of white space is allowed before the string.
13554 If a dictionary file is passed as
13556 the value of a @option{-D@var{file}} switch
13559 an option to the @option{/DICTIONARY} qualifier
13562 simple name and every identifier, @command{gnatpp} checks if the dictionary
13563 defines the casing for the name or for some of its parts (the term ``subword''
13564 is used below to denote the part of a name which is delimited by ``_'' or by
13565 the beginning or end of the word and which does not contain any ``_'' inside):
13569 if the whole name is in the dictionary, @command{gnatpp} uses for this name
13570 the casing defined by the dictionary; no subwords are checked for this word
13573 for every subword @command{gnatpp} checks if the dictionary contains the
13574 corresponding string of the form @code{*@var{simple_identifier}*},
13575 and if it does, the casing of this @var{simple_identifier} is used
13579 if the whole name does not contain any ``_'' inside, and if for this name
13580 the dictionary contains two entries - one of the form @var{identifier},
13581 and another - of the form *@var{simple_identifier}*, then the first one
13582 is applied to define the casing of this name
13585 if more than one dictionary file is passed as @command{gnatpp} switches, each
13586 dictionary adds new casing exceptions and overrides all the existing casing
13587 exceptions set by the previous dictionaries
13590 when @command{gnatpp} checks if the word or subword is in the dictionary,
13591 this check is not case sensitive
13595 For example, suppose we have the following source to reformat:
13597 @smallexample @c ada
13600 name1 : integer := 1;
13601 name4_name3_name2 : integer := 2;
13602 name2_name3_name4 : Boolean;
13605 name2_name3_name4 := name4_name3_name2 > name1;
13611 And suppose we have two dictionaries:
13628 If @command{gnatpp} is called with the following switches:
13632 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
13635 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
13640 then we will get the following name casing in the @command{gnatpp} output:
13642 @smallexample @c ada
13645 NAME1 : Integer := 1;
13646 Name4_NAME3_Name2 : Integer := 2;
13647 Name2_NAME3_Name4 : Boolean;
13650 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
13655 @c *********************************
13656 @node The GNAT Metric Tool gnatmetric
13657 @chapter The GNAT Metric Tool @command{gnatmetric}
13659 @cindex Metric tool
13662 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
13663 for computing various program metrics.
13664 It takes an Ada source file as input and generates a file containing the
13665 metrics data as output. Various switches control which
13666 metrics are computed and output.
13668 @command{gnatmetric} generates and uses the ASIS
13669 tree for the input source and thus requires the input to be syntactically and
13670 semantically legal.
13671 If this condition is not met, @command{gnatmetric} will generate
13672 an error message; no metric information for this file will be
13673 computed and reported.
13675 If the compilation unit contained in the input source depends semantically
13676 upon units in files located outside the current directory, you have to provide
13677 the source search path when invoking @command{gnatmetric}.
13678 If it depends semantically upon units that are contained
13679 in files with names that do not follow the GNAT file naming rules, you have to
13680 provide the configuration file describing the corresponding naming scheme (see
13681 the description of the @command{gnatmetric} switches below.)
13682 Alternatively, you may use a project file and invoke @command{gnatmetric}
13683 through the @command{gnat} driver.
13685 The @command{gnatmetric} command has the form
13688 @c $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
13689 @c Expanding @ovar macro inline (explanation in macro def comments)
13690 $ gnatmetric @r{[}@var{switches}@r{]} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
13697 @var{switches} specify the metrics to compute and define the destination for
13701 Each @var{filename} is the name (including the extension) of a source
13702 file to process. ``Wildcards'' are allowed, and
13703 the file name may contain path information.
13704 If no @var{filename} is supplied, then the @var{switches} list must contain
13706 @option{-files} switch (@pxref{Other gnatmetric Switches}).
13707 Including both a @option{-files} switch and one or more
13708 @var{filename} arguments is permitted.
13711 @samp{@var{gcc_switches}} is a list of switches for
13712 @command{gcc}. They will be passed on to all compiler invocations made by
13713 @command{gnatmetric} to generate the ASIS trees. Here you can provide
13714 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
13715 and use the @option{-gnatec} switch to set the configuration file.
13719 * Switches for gnatmetric::
13722 @node Switches for gnatmetric
13723 @section Switches for @command{gnatmetric}
13726 The following subsections describe the various switches accepted by
13727 @command{gnatmetric}, organized by category.
13730 * Output Files Control::
13731 * Disable Metrics For Local Units::
13732 * Specifying a set of metrics to compute::
13733 * Other gnatmetric Switches::
13734 * Generate project-wide metrics::
13737 @node Output Files Control
13738 @subsection Output File Control
13739 @cindex Output file control in @command{gnatmetric}
13742 @command{gnatmetric} has two output formats. It can generate a
13743 textual (human-readable) form, and also XML. By default only textual
13744 output is generated.
13746 When generating the output in textual form, @command{gnatmetric} creates
13747 for each Ada source file a corresponding text file
13748 containing the computed metrics, except for the case when the set of metrics
13749 specified by gnatmetric parameters consists only of metrics that are computed
13750 for the whole set of analyzed sources, but not for each Ada source.
13751 By default, this file is placed in the same directory as where the source
13752 file is located, and its name is obtained
13753 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
13756 All the output information generated in XML format is placed in a single
13757 file. By default this file is placed in the current directory and has the
13758 name ^@file{metrix.xml}^@file{METRIX$XML}^.
13760 Some of the computed metrics are summed over the units passed to
13761 @command{gnatmetric}; for example, the total number of lines of code.
13762 By default this information is sent to @file{stdout}, but a file
13763 can be specified with the @option{-og} switch.
13765 The following switches control the @command{gnatmetric} output:
13768 @cindex @option{^-x^/XML^} (@command{gnatmetric})
13770 Generate the XML output
13772 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
13774 Generate the XML output and the XML schema file that describes the structure
13775 of the XML metric report, this schema is assigned to the XML file. The schema
13776 file has the same name as the XML output file with @file{.xml} suffix replaced
13779 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
13780 @item ^-nt^/NO_TEXT^
13781 Do not generate the output in text form (implies @option{^-x^/XML^})
13783 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
13784 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
13785 Put text files with detailed metrics into @var{output_dir}
13787 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
13788 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
13789 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
13790 in the name of the output file.
13792 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
13793 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
13794 Put global metrics into @var{file_name}
13796 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
13797 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
13798 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
13800 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
13801 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
13802 Use ``short'' source file names in the output. (The @command{gnatmetric}
13803 output includes the name(s) of the Ada source file(s) from which the metrics
13804 are computed. By default each name includes the absolute path. The
13805 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
13806 to exclude all directory information from the file names that are output.)
13810 @node Disable Metrics For Local Units
13811 @subsection Disable Metrics For Local Units
13812 @cindex Disable Metrics For Local Units in @command{gnatmetric}
13815 @command{gnatmetric} relies on the GNAT compilation model @minus{}
13817 unit per one source file. It computes line metrics for the whole source
13818 file, and it also computes syntax
13819 and complexity metrics for the file's outermost unit.
13821 By default, @command{gnatmetric} will also compute all metrics for certain
13822 kinds of locally declared program units:
13826 subprogram (and generic subprogram) bodies;
13829 package (and generic package) specs and bodies;
13832 task object and type specifications and bodies;
13835 protected object and type specifications and bodies.
13839 These kinds of entities will be referred to as
13840 @emph{eligible local program units}, or simply @emph{eligible local units},
13841 @cindex Eligible local unit (for @command{gnatmetric})
13842 in the discussion below.
13844 Note that a subprogram declaration, generic instantiation,
13845 or renaming declaration only receives metrics
13846 computation when it appear as the outermost entity
13849 Suppression of metrics computation for eligible local units can be
13850 obtained via the following switch:
13853 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
13854 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
13855 Do not compute detailed metrics for eligible local program units
13859 @node Specifying a set of metrics to compute
13860 @subsection Specifying a set of metrics to compute
13863 By default all the metrics are computed and reported. The switches
13864 described in this subsection allow you to control, on an individual
13865 basis, whether metrics are computed and
13866 reported. If at least one positive metric
13867 switch is specified (that is, a switch that defines that a given
13868 metric or set of metrics is to be computed), then only
13869 explicitly specified metrics are reported.
13872 * Line Metrics Control::
13873 * Syntax Metrics Control::
13874 * Complexity Metrics Control::
13875 * Object-Oriented Metrics Control::
13878 @node Line Metrics Control
13879 @subsubsection Line Metrics Control
13880 @cindex Line metrics control in @command{gnatmetric}
13883 For any (legal) source file, and for each of its
13884 eligible local program units, @command{gnatmetric} computes the following
13889 the total number of lines;
13892 the total number of code lines (i.e., non-blank lines that are not comments)
13895 the number of comment lines
13898 the number of code lines containing end-of-line comments;
13901 the comment percentage: the ratio between the number of lines that contain
13902 comments and the number of all non-blank lines, expressed as a percentage;
13905 the number of empty lines and lines containing only space characters and/or
13906 format effectors (blank lines)
13909 the average number of code lines in subprogram bodies, task bodies, entry
13910 bodies and statement sequences in package bodies (this metric is only computed
13911 across the whole set of the analyzed units)
13916 @command{gnatmetric} sums the values of the line metrics for all the
13917 files being processed and then generates the cumulative results. The tool
13918 also computes for all the files being processed the average number of code
13921 You can use the following switches to select the specific line metrics
13922 to be computed and reported.
13925 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
13928 @cindex @option{--no-lines@var{x}}
13931 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
13932 Report all the line metrics
13934 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
13935 Do not report any of line metrics
13937 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
13938 Report the number of all lines
13940 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
13941 Do not report the number of all lines
13943 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
13944 Report the number of code lines
13946 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
13947 Do not report the number of code lines
13949 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
13950 Report the number of comment lines
13952 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
13953 Do not report the number of comment lines
13955 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
13956 Report the number of code lines containing
13957 end-of-line comments
13959 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
13960 Do not report the number of code lines containing
13961 end-of-line comments
13963 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
13964 Report the comment percentage in the program text
13966 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
13967 Do not report the comment percentage in the program text
13969 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
13970 Report the number of blank lines
13972 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
13973 Do not report the number of blank lines
13975 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
13976 Report the average number of code lines in subprogram bodies, task bodies,
13977 entry bodies and statement sequences in package bodies. The metric is computed
13978 and reported for the whole set of processed Ada sources only.
13980 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
13981 Do not report the average number of code lines in subprogram bodies,
13982 task bodies, entry bodies and statement sequences in package bodies.
13986 @node Syntax Metrics Control
13987 @subsubsection Syntax Metrics Control
13988 @cindex Syntax metrics control in @command{gnatmetric}
13991 @command{gnatmetric} computes various syntactic metrics for the
13992 outermost unit and for each eligible local unit:
13995 @item LSLOC (``Logical Source Lines Of Code'')
13996 The total number of declarations and the total number of statements
13998 @item Maximal static nesting level of inner program units
14000 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
14001 package, a task unit, a protected unit, a
14002 protected entry, a generic unit, or an explicitly declared subprogram other
14003 than an enumeration literal.''
14005 @item Maximal nesting level of composite syntactic constructs
14006 This corresponds to the notion of the
14007 maximum nesting level in the GNAT built-in style checks
14008 (@pxref{Style Checking})
14012 For the outermost unit in the file, @command{gnatmetric} additionally computes
14013 the following metrics:
14016 @item Public subprograms
14017 This metric is computed for package specs. It is the
14018 number of subprograms and generic subprograms declared in the visible
14019 part (including the visible part of nested packages, protected objects, and
14022 @item All subprograms
14023 This metric is computed for bodies and subunits. The
14024 metric is equal to a total number of subprogram bodies in the compilation
14026 Neither generic instantiations nor renamings-as-a-body nor body stubs
14027 are counted. Any subprogram body is counted, independently of its nesting
14028 level and enclosing constructs. Generic bodies and bodies of protected
14029 subprograms are counted in the same way as ``usual'' subprogram bodies.
14032 This metric is computed for package specs and
14033 generic package declarations. It is the total number of types
14034 that can be referenced from outside this compilation unit, plus the
14035 number of types from all the visible parts of all the visible generic
14036 packages. Generic formal types are not counted. Only types, not subtypes,
14040 Along with the total number of public types, the following
14041 types are counted and reported separately:
14048 Root tagged types (abstract, non-abstract, private, non-private). Type
14049 extensions are @emph{not} counted
14052 Private types (including private extensions)
14063 This metric is computed for any compilation unit. It is equal to the total
14064 number of the declarations of different types given in the compilation unit.
14065 The private and the corresponding full type declaration are counted as one
14066 type declaration. Incomplete type declarations and generic formal types
14068 No distinction is made among different kinds of types (abstract,
14069 private etc.); the total number of types is computed and reported.
14074 By default, all the syntax metrics are computed and reported. You can use the
14075 following switches to select specific syntax metrics.
14079 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
14082 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
14085 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
14086 Report all the syntax metrics
14088 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
14089 Do not report any of syntax metrics
14091 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
14092 Report the total number of declarations
14094 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
14095 Do not report the total number of declarations
14097 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
14098 Report the total number of statements
14100 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
14101 Do not report the total number of statements
14103 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
14104 Report the number of public subprograms in a compilation unit
14106 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
14107 Do not report the number of public subprograms in a compilation unit
14109 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
14110 Report the number of all the subprograms in a compilation unit
14112 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
14113 Do not report the number of all the subprograms in a compilation unit
14115 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
14116 Report the number of public types in a compilation unit
14118 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
14119 Do not report the number of public types in a compilation unit
14121 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
14122 Report the number of all the types in a compilation unit
14124 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
14125 Do not report the number of all the types in a compilation unit
14127 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
14128 Report the maximal program unit nesting level
14130 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
14131 Do not report the maximal program unit nesting level
14133 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
14134 Report the maximal construct nesting level
14136 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
14137 Do not report the maximal construct nesting level
14141 @node Complexity Metrics Control
14142 @subsubsection Complexity Metrics Control
14143 @cindex Complexity metrics control in @command{gnatmetric}
14146 For a program unit that is an executable body (a subprogram body (including
14147 generic bodies), task body, entry body or a package body containing
14148 its own statement sequence) @command{gnatmetric} computes the following
14149 complexity metrics:
14153 McCabe cyclomatic complexity;
14156 McCabe essential complexity;
14159 maximal loop nesting level
14164 The McCabe complexity metrics are defined
14165 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
14167 According to McCabe, both control statements and short-circuit control forms
14168 should be taken into account when computing cyclomatic complexity. For each
14169 body, we compute three metric values:
14173 the complexity introduced by control
14174 statements only, without taking into account short-circuit forms,
14177 the complexity introduced by short-circuit control forms only, and
14181 cyclomatic complexity, which is the sum of these two values.
14185 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
14186 the code in the exception handlers and in all the nested program units.
14188 By default, all the complexity metrics are computed and reported.
14189 For more fine-grained control you can use
14190 the following switches:
14193 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
14196 @cindex @option{--no-complexity@var{x}}
14199 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
14200 Report all the complexity metrics
14202 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
14203 Do not report any of complexity metrics
14205 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
14206 Report the McCabe Cyclomatic Complexity
14208 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
14209 Do not report the McCabe Cyclomatic Complexity
14211 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
14212 Report the Essential Complexity
14214 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
14215 Do not report the Essential Complexity
14217 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
14218 Report maximal loop nesting level
14220 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
14221 Do not report maximal loop nesting level
14223 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
14224 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
14225 task bodies, entry bodies and statement sequences in package bodies.
14226 The metric is computed and reported for whole set of processed Ada sources
14229 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
14230 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
14231 bodies, task bodies, entry bodies and statement sequences in package bodies
14233 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
14234 @item ^-ne^/NO_EXITS_AS_GOTOS^
14235 Do not consider @code{exit} statements as @code{goto}s when
14236 computing Essential Complexity
14238 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
14239 Report the extra exit points for subprogram bodies. As an exit point, this
14240 metric counts @code{return} statements and raise statements in case when the
14241 raised exception is not handled in the same body. In case of a function this
14242 metric subtracts 1 from the number of exit points, because a function body
14243 must contain at least one @code{return} statement.
14245 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
14246 Do not report the extra exit points for subprogram bodies
14250 @node Object-Oriented Metrics Control
14251 @subsubsection Object-Oriented Metrics Control
14252 @cindex Object-Oriented metrics control in @command{gnatmetric}
14255 @cindex Coupling metrics (in in @command{gnatmetric})
14256 Coupling metrics are object-oriented metrics that measure the
14257 dependencies between a given class (or a group of classes) and the
14258 ``external world'' (that is, the other classes in the program). In this
14259 subsection the term ``class'' is used in its
14260 traditional object-oriented programming sense
14261 (an instantiable module that contains data and/or method members).
14262 A @emph{category} (of classes)
14263 is a group of closely related classes that are reused and/or
14266 A class @code{K}'s @emph{efferent coupling} is the number of classes
14267 that @code{K} depends upon.
14268 A category's efferent coupling is the number of classes outside the
14269 category that the classes inside the category depend upon.
14271 A class @code{K}'s @emph{afferent coupling} is the number of classes
14272 that depend upon @code{K}.
14273 A category's afferent coupling is the number of classes outside the
14274 category that depend on classes belonging to the category.
14276 Ada's implementation of the object-oriented paradigm does not use the
14277 traditional class notion, so the definition of the coupling
14278 metrics for Ada maps the class and class category notions
14279 onto Ada constructs.
14281 For the coupling metrics, several kinds of modules -- a library package,
14282 a library generic package, and a library generic package instantiation --
14283 that define a tagged type or an interface type are
14284 considered to be a class. A category consists of a library package (or
14285 a library generic package) that defines a tagged or an interface type,
14286 together with all its descendant (generic) packages that define tagged
14287 or interface types. For any package counted as a class,
14288 its body and subunits (if any) are considered
14289 together with its spec when counting the dependencies, and coupling
14290 metrics are reported for spec units only. For dependencies
14291 between classes, the Ada semantic dependencies are considered.
14292 For coupling metrics, only dependencies on units that are considered as
14293 classes, are considered.
14295 When computing coupling metrics, @command{gnatmetric} counts only
14296 dependencies between units that are arguments of the gnatmetric call.
14297 Coupling metrics are program-wide (or project-wide) metrics, so to
14298 get a valid result, you should call @command{gnatmetric} for
14299 the whole set of sources that make up your program. It can be done
14300 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
14301 option (see See @ref{The GNAT Driver and Project Files} for details.
14303 By default, all the coupling metrics are disabled. You can use the following
14304 switches to specify the coupling metrics to be computed and reported:
14309 @cindex @option{--package@var{x}} (@command{gnatmetric})
14310 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
14311 @cindex @option{--category@var{x}} (@command{gnatmetric})
14312 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
14316 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
14319 @item ^--coupling-all^/COUPLING_METRICS=ALL^
14320 Report all the coupling metrics
14322 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
14323 Do not report any of metrics
14325 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
14326 Report package efferent coupling
14328 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
14329 Do not report package efferent coupling
14331 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
14332 Report package afferent coupling
14334 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
14335 Do not report package afferent coupling
14337 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
14338 Report category efferent coupling
14340 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
14341 Do not report category efferent coupling
14343 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
14344 Report category afferent coupling
14346 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
14347 Do not report category afferent coupling
14351 @node Other gnatmetric Switches
14352 @subsection Other @code{gnatmetric} Switches
14355 Additional @command{gnatmetric} switches are as follows:
14358 @item ^-files @var{filename}^/FILES=@var{filename}^
14359 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
14360 Take the argument source files from the specified file. This file should be an
14361 ordinary text file containing file names separated by spaces or
14362 line breaks. You can use this switch more than once in the same call to
14363 @command{gnatmetric}. You also can combine this switch with
14364 an explicit list of files.
14366 @item ^-v^/VERBOSE^
14367 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
14369 @command{gnatmetric} generates version information and then
14370 a trace of sources being processed.
14372 @item ^-dv^/DEBUG_OUTPUT^
14373 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
14375 @command{gnatmetric} generates various messages useful to understand what
14376 happens during the metrics computation
14379 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
14383 @node Generate project-wide metrics
14384 @subsection Generate project-wide metrics
14386 In order to compute metrics on all units of a given project, you can use
14387 the @command{gnat} driver along with the @option{-P} option:
14393 If the project @code{proj} depends upon other projects, you can compute
14394 the metrics on the project closure using the @option{-U} option:
14396 gnat metric -Pproj -U
14400 Finally, if not all the units are relevant to a particular main
14401 program in the project closure, you can generate metrics for the set
14402 of units needed to create a given main program (unit closure) using
14403 the @option{-U} option followed by the name of the main unit:
14405 gnat metric -Pproj -U main
14409 @c ***********************************
14410 @node File Name Krunching Using gnatkr
14411 @chapter File Name Krunching Using @code{gnatkr}
14415 This chapter discusses the method used by the compiler to shorten
14416 the default file names chosen for Ada units so that they do not
14417 exceed the maximum length permitted. It also describes the
14418 @code{gnatkr} utility that can be used to determine the result of
14419 applying this shortening.
14423 * Krunching Method::
14424 * Examples of gnatkr Usage::
14428 @section About @code{gnatkr}
14431 The default file naming rule in GNAT
14432 is that the file name must be derived from
14433 the unit name. The exact default rule is as follows:
14436 Take the unit name and replace all dots by hyphens.
14438 If such a replacement occurs in the
14439 second character position of a name, and the first character is
14440 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
14441 then replace the dot by the character
14442 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
14443 instead of a minus.
14445 The reason for this exception is to avoid clashes
14446 with the standard names for children of System, Ada, Interfaces,
14447 and GNAT, which use the prefixes
14448 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
14451 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
14452 switch of the compiler activates a ``krunching''
14453 circuit that limits file names to nn characters (where nn is a decimal
14454 integer). For example, using OpenVMS,
14455 where the maximum file name length is
14456 39, the value of nn is usually set to 39, but if you want to generate
14457 a set of files that would be usable if ported to a system with some
14458 different maximum file length, then a different value can be specified.
14459 The default value of 39 for OpenVMS need not be specified.
14461 The @code{gnatkr} utility can be used to determine the krunched name for
14462 a given file, when krunched to a specified maximum length.
14465 @section Using @code{gnatkr}
14468 The @code{gnatkr} command has the form
14472 @c $ gnatkr @var{name} @ovar{length}
14473 @c Expanding @ovar macro inline (explanation in macro def comments)
14474 $ gnatkr @var{name} @r{[}@var{length}@r{]}
14480 $ gnatkr @var{name} /COUNT=nn
14485 @var{name} is the uncrunched file name, derived from the name of the unit
14486 in the standard manner described in the previous section (i.e., in particular
14487 all dots are replaced by hyphens). The file name may or may not have an
14488 extension (defined as a suffix of the form period followed by arbitrary
14489 characters other than period). If an extension is present then it will
14490 be preserved in the output. For example, when krunching @file{hellofile.ads}
14491 to eight characters, the result will be hellofil.ads.
14493 Note: for compatibility with previous versions of @code{gnatkr} dots may
14494 appear in the name instead of hyphens, but the last dot will always be
14495 taken as the start of an extension. So if @code{gnatkr} is given an argument
14496 such as @file{Hello.World.adb} it will be treated exactly as if the first
14497 period had been a hyphen, and for example krunching to eight characters
14498 gives the result @file{hellworl.adb}.
14500 Note that the result is always all lower case (except on OpenVMS where it is
14501 all upper case). Characters of the other case are folded as required.
14503 @var{length} represents the length of the krunched name. The default
14504 when no argument is given is ^8^39^ characters. A length of zero stands for
14505 unlimited, in other words do not chop except for system files where the
14506 implied crunching length is always eight characters.
14509 The output is the krunched name. The output has an extension only if the
14510 original argument was a file name with an extension.
14512 @node Krunching Method
14513 @section Krunching Method
14516 The initial file name is determined by the name of the unit that the file
14517 contains. The name is formed by taking the full expanded name of the
14518 unit and replacing the separating dots with hyphens and
14519 using ^lowercase^uppercase^
14520 for all letters, except that a hyphen in the second character position is
14521 replaced by a ^tilde^dollar sign^ if the first character is
14522 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
14523 The extension is @code{.ads} for a
14524 spec and @code{.adb} for a body.
14525 Krunching does not affect the extension, but the file name is shortened to
14526 the specified length by following these rules:
14530 The name is divided into segments separated by hyphens, tildes or
14531 underscores and all hyphens, tildes, and underscores are
14532 eliminated. If this leaves the name short enough, we are done.
14535 If the name is too long, the longest segment is located (left-most
14536 if there are two of equal length), and shortened by dropping
14537 its last character. This is repeated until the name is short enough.
14539 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
14540 to fit the name into 8 characters as required by some operating systems.
14543 our-strings-wide_fixed 22
14544 our strings wide fixed 19
14545 our string wide fixed 18
14546 our strin wide fixed 17
14547 our stri wide fixed 16
14548 our stri wide fixe 15
14549 our str wide fixe 14
14550 our str wid fixe 13
14556 Final file name: oustwifi.adb
14560 The file names for all predefined units are always krunched to eight
14561 characters. The krunching of these predefined units uses the following
14562 special prefix replacements:
14566 replaced by @file{^a^A^-}
14569 replaced by @file{^g^G^-}
14572 replaced by @file{^i^I^-}
14575 replaced by @file{^s^S^-}
14578 These system files have a hyphen in the second character position. That
14579 is why normal user files replace such a character with a
14580 ^tilde^dollar sign^, to
14581 avoid confusion with system file names.
14583 As an example of this special rule, consider
14584 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
14587 ada-strings-wide_fixed 22
14588 a- strings wide fixed 18
14589 a- string wide fixed 17
14590 a- strin wide fixed 16
14591 a- stri wide fixed 15
14592 a- stri wide fixe 14
14593 a- str wide fixe 13
14599 Final file name: a-stwifi.adb
14603 Of course no file shortening algorithm can guarantee uniqueness over all
14604 possible unit names, and if file name krunching is used then it is your
14605 responsibility to ensure that no name clashes occur. The utility
14606 program @code{gnatkr} is supplied for conveniently determining the
14607 krunched name of a file.
14609 @node Examples of gnatkr Usage
14610 @section Examples of @code{gnatkr} Usage
14617 $ gnatkr very_long_unit_name.ads --> velounna.ads
14618 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
14619 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
14620 $ gnatkr grandparent-parent-child --> grparchi
14622 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
14623 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
14626 @node Preprocessing Using gnatprep
14627 @chapter Preprocessing Using @code{gnatprep}
14631 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
14633 Although designed for use with GNAT, @code{gnatprep} does not depend on any
14634 special GNAT features.
14635 For further discussion of conditional compilation in general, see
14636 @ref{Conditional Compilation}.
14639 * Preprocessing Symbols::
14641 * Switches for gnatprep::
14642 * Form of Definitions File::
14643 * Form of Input Text for gnatprep::
14646 @node Preprocessing Symbols
14647 @section Preprocessing Symbols
14650 Preprocessing symbols are defined in definition files and referred to in
14651 sources to be preprocessed. A Preprocessing symbol is an identifier, following
14652 normal Ada (case-insensitive) rules for its syntax, with the restriction that
14653 all characters need to be in the ASCII set (no accented letters).
14655 @node Using gnatprep
14656 @section Using @code{gnatprep}
14659 To call @code{gnatprep} use
14662 @c $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
14663 @c Expanding @ovar macro inline (explanation in macro def comments)
14664 $ gnatprep @r{[}@var{switches}@r{]} @var{infile} @var{outfile} @r{[}@var{deffile}@r{]}
14671 is an optional sequence of switches as described in the next section.
14674 is the full name of the input file, which is an Ada source
14675 file containing preprocessor directives.
14678 is the full name of the output file, which is an Ada source
14679 in standard Ada form. When used with GNAT, this file name will
14680 normally have an ads or adb suffix.
14683 is the full name of a text file containing definitions of
14684 preprocessing symbols to be referenced by the preprocessor. This argument is
14685 optional, and can be replaced by the use of the @option{-D} switch.
14689 @node Switches for gnatprep
14690 @section Switches for @code{gnatprep}
14695 @item ^-b^/BLANK_LINES^
14696 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
14697 Causes both preprocessor lines and the lines deleted by
14698 preprocessing to be replaced by blank lines in the output source file,
14699 preserving line numbers in the output file.
14701 @item ^-c^/COMMENTS^
14702 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
14703 Causes both preprocessor lines and the lines deleted
14704 by preprocessing to be retained in the output source as comments marked
14705 with the special string @code{"--! "}. This option will result in line numbers
14706 being preserved in the output file.
14708 @item ^-C^/REPLACE_IN_COMMENTS^
14709 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
14710 Causes comments to be scanned. Normally comments are ignored by gnatprep.
14711 If this option is specified, then comments are scanned and any $symbol
14712 substitutions performed as in program text. This is particularly useful
14713 when structured comments are used (e.g., when writing programs in the
14714 SPARK dialect of Ada). Note that this switch is not available when
14715 doing integrated preprocessing (it would be useless in this context
14716 since comments are ignored by the compiler in any case).
14718 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
14719 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
14720 Defines a new preprocessing symbol, associated with value. If no value is given
14721 on the command line, then symbol is considered to be @code{True}. This switch
14722 can be used in place of a definition file.
14726 @cindex @option{/REMOVE} (@command{gnatprep})
14727 This is the default setting which causes lines deleted by preprocessing
14728 to be entirely removed from the output file.
14731 @item ^-r^/REFERENCE^
14732 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
14733 Causes a @code{Source_Reference} pragma to be generated that
14734 references the original input file, so that error messages will use
14735 the file name of this original file. The use of this switch implies
14736 that preprocessor lines are not to be removed from the file, so its
14737 use will force @option{^-b^/BLANK_LINES^} mode if
14738 @option{^-c^/COMMENTS^}
14739 has not been specified explicitly.
14741 Note that if the file to be preprocessed contains multiple units, then
14742 it will be necessary to @code{gnatchop} the output file from
14743 @code{gnatprep}. If a @code{Source_Reference} pragma is present
14744 in the preprocessed file, it will be respected by
14745 @code{gnatchop ^-r^/REFERENCE^}
14746 so that the final chopped files will correctly refer to the original
14747 input source file for @code{gnatprep}.
14749 @item ^-s^/SYMBOLS^
14750 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
14751 Causes a sorted list of symbol names and values to be
14752 listed on the standard output file.
14754 @item ^-u^/UNDEFINED^
14755 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
14756 Causes undefined symbols to be treated as having the value FALSE in the context
14757 of a preprocessor test. In the absence of this option, an undefined symbol in
14758 a @code{#if} or @code{#elsif} test will be treated as an error.
14764 Note: if neither @option{-b} nor @option{-c} is present,
14765 then preprocessor lines and
14766 deleted lines are completely removed from the output, unless -r is
14767 specified, in which case -b is assumed.
14770 @node Form of Definitions File
14771 @section Form of Definitions File
14774 The definitions file contains lines of the form
14781 where symbol is a preprocessing symbol, and value is one of the following:
14785 Empty, corresponding to a null substitution
14787 A string literal using normal Ada syntax
14789 Any sequence of characters from the set
14790 (letters, digits, period, underline).
14794 Comment lines may also appear in the definitions file, starting with
14795 the usual @code{--},
14796 and comments may be added to the definitions lines.
14798 @node Form of Input Text for gnatprep
14799 @section Form of Input Text for @code{gnatprep}
14802 The input text may contain preprocessor conditional inclusion lines,
14803 as well as general symbol substitution sequences.
14805 The preprocessor conditional inclusion commands have the form
14810 #if @i{expression} @r{[}then@r{]}
14812 #elsif @i{expression} @r{[}then@r{]}
14814 #elsif @i{expression} @r{[}then@r{]}
14825 In this example, @i{expression} is defined by the following grammar:
14827 @i{expression} ::= <symbol>
14828 @i{expression} ::= <symbol> = "<value>"
14829 @i{expression} ::= <symbol> = <symbol>
14830 @i{expression} ::= <symbol> 'Defined
14831 @i{expression} ::= not @i{expression}
14832 @i{expression} ::= @i{expression} and @i{expression}
14833 @i{expression} ::= @i{expression} or @i{expression}
14834 @i{expression} ::= @i{expression} and then @i{expression}
14835 @i{expression} ::= @i{expression} or else @i{expression}
14836 @i{expression} ::= ( @i{expression} )
14839 The following restriction exists: it is not allowed to have "and" or "or"
14840 following "not" in the same expression without parentheses. For example, this
14847 This should be one of the following:
14855 For the first test (@i{expression} ::= <symbol>) the symbol must have
14856 either the value true or false, that is to say the right-hand of the
14857 symbol definition must be one of the (case-insensitive) literals
14858 @code{True} or @code{False}. If the value is true, then the
14859 corresponding lines are included, and if the value is false, they are
14862 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
14863 the symbol has been defined in the definition file or by a @option{-D}
14864 switch on the command line. Otherwise, the test is false.
14866 The equality tests are case insensitive, as are all the preprocessor lines.
14868 If the symbol referenced is not defined in the symbol definitions file,
14869 then the effect depends on whether or not switch @option{-u}
14870 is specified. If so, then the symbol is treated as if it had the value
14871 false and the test fails. If this switch is not specified, then
14872 it is an error to reference an undefined symbol. It is also an error to
14873 reference a symbol that is defined with a value other than @code{True}
14876 The use of the @code{not} operator inverts the sense of this logical test.
14877 The @code{not} operator cannot be combined with the @code{or} or @code{and}
14878 operators, without parentheses. For example, "if not X or Y then" is not
14879 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
14881 The @code{then} keyword is optional as shown
14883 The @code{#} must be the first non-blank character on a line, but
14884 otherwise the format is free form. Spaces or tabs may appear between
14885 the @code{#} and the keyword. The keywords and the symbols are case
14886 insensitive as in normal Ada code. Comments may be used on a
14887 preprocessor line, but other than that, no other tokens may appear on a
14888 preprocessor line. Any number of @code{elsif} clauses can be present,
14889 including none at all. The @code{else} is optional, as in Ada.
14891 The @code{#} marking the start of a preprocessor line must be the first
14892 non-blank character on the line, i.e., it must be preceded only by
14893 spaces or horizontal tabs.
14895 Symbol substitution outside of preprocessor lines is obtained by using
14903 anywhere within a source line, except in a comment or within a
14904 string literal. The identifier
14905 following the @code{$} must match one of the symbols defined in the symbol
14906 definition file, and the result is to substitute the value of the
14907 symbol in place of @code{$symbol} in the output file.
14909 Note that although the substitution of strings within a string literal
14910 is not possible, it is possible to have a symbol whose defined value is
14911 a string literal. So instead of setting XYZ to @code{hello} and writing:
14914 Header : String := "$XYZ";
14918 you should set XYZ to @code{"hello"} and write:
14921 Header : String := $XYZ;
14925 and then the substitution will occur as desired.
14928 @node The GNAT Run-Time Library Builder gnatlbr
14929 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
14931 @cindex Library builder
14934 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
14935 supplied configuration pragmas.
14938 * Running gnatlbr::
14939 * Switches for gnatlbr::
14940 * Examples of gnatlbr Usage::
14943 @node Running gnatlbr
14944 @section Running @code{gnatlbr}
14947 The @code{gnatlbr} command has the form
14950 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
14953 @node Switches for gnatlbr
14954 @section Switches for @code{gnatlbr}
14957 @code{gnatlbr} recognizes the following switches:
14961 @item /CREATE=directory
14962 @cindex @code{/CREATE} (@code{gnatlbr})
14963 Create the new run-time library in the specified directory.
14965 @item /SET=directory
14966 @cindex @code{/SET} (@code{gnatlbr})
14967 Make the library in the specified directory the current run-time library.
14969 @item /DELETE=directory
14970 @cindex @code{/DELETE} (@code{gnatlbr})
14971 Delete the run-time library in the specified directory.
14974 @cindex @code{/CONFIG} (@code{gnatlbr})
14975 With /CREATE: Use the configuration pragmas in the specified file when
14976 building the library.
14978 With /SET: Use the configuration pragmas in the specified file when
14983 @node Examples of gnatlbr Usage
14984 @section Example of @code{gnatlbr} Usage
14987 Contents of VAXFLOAT.ADC:
14988 pragma Float_Representation (VAX_Float);
14990 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
14992 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
14997 @node The GNAT Library Browser gnatls
14998 @chapter The GNAT Library Browser @code{gnatls}
15000 @cindex Library browser
15003 @code{gnatls} is a tool that outputs information about compiled
15004 units. It gives the relationship between objects, unit names and source
15005 files. It can also be used to check the source dependencies of a unit
15006 as well as various characteristics.
15008 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
15009 driver (see @ref{The GNAT Driver and Project Files}).
15013 * Switches for gnatls::
15014 * Examples of gnatls Usage::
15017 @node Running gnatls
15018 @section Running @code{gnatls}
15021 The @code{gnatls} command has the form
15024 $ gnatls switches @var{object_or_ali_file}
15028 The main argument is the list of object or @file{ali} files
15029 (@pxref{The Ada Library Information Files})
15030 for which information is requested.
15032 In normal mode, without additional option, @code{gnatls} produces a
15033 four-column listing. Each line represents information for a specific
15034 object. The first column gives the full path of the object, the second
15035 column gives the name of the principal unit in this object, the third
15036 column gives the status of the source and the fourth column gives the
15037 full path of the source representing this unit.
15038 Here is a simple example of use:
15042 ^./^[]^demo1.o demo1 DIF demo1.adb
15043 ^./^[]^demo2.o demo2 OK demo2.adb
15044 ^./^[]^hello.o h1 OK hello.adb
15045 ^./^[]^instr-child.o instr.child MOK instr-child.adb
15046 ^./^[]^instr.o instr OK instr.adb
15047 ^./^[]^tef.o tef DIF tef.adb
15048 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
15049 ^./^[]^tgef.o tgef DIF tgef.adb
15053 The first line can be interpreted as follows: the main unit which is
15055 object file @file{demo1.o} is demo1, whose main source is in
15056 @file{demo1.adb}. Furthermore, the version of the source used for the
15057 compilation of demo1 has been modified (DIF). Each source file has a status
15058 qualifier which can be:
15061 @item OK (unchanged)
15062 The version of the source file used for the compilation of the
15063 specified unit corresponds exactly to the actual source file.
15065 @item MOK (slightly modified)
15066 The version of the source file used for the compilation of the
15067 specified unit differs from the actual source file but not enough to
15068 require recompilation. If you use gnatmake with the qualifier
15069 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
15070 MOK will not be recompiled.
15072 @item DIF (modified)
15073 No version of the source found on the path corresponds to the source
15074 used to build this object.
15076 @item ??? (file not found)
15077 No source file was found for this unit.
15079 @item HID (hidden, unchanged version not first on PATH)
15080 The version of the source that corresponds exactly to the source used
15081 for compilation has been found on the path but it is hidden by another
15082 version of the same source that has been modified.
15086 @node Switches for gnatls
15087 @section Switches for @code{gnatls}
15090 @code{gnatls} recognizes the following switches:
15094 @cindex @option{--version} @command{gnatls}
15095 Display Copyright and version, then exit disregarding all other options.
15098 @cindex @option{--help} @command{gnatls}
15099 If @option{--version} was not used, display usage, then exit disregarding
15102 @item ^-a^/ALL_UNITS^
15103 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
15104 Consider all units, including those of the predefined Ada library.
15105 Especially useful with @option{^-d^/DEPENDENCIES^}.
15107 @item ^-d^/DEPENDENCIES^
15108 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
15109 List sources from which specified units depend on.
15111 @item ^-h^/OUTPUT=OPTIONS^
15112 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
15113 Output the list of options.
15115 @item ^-o^/OUTPUT=OBJECTS^
15116 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
15117 Only output information about object files.
15119 @item ^-s^/OUTPUT=SOURCES^
15120 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
15121 Only output information about source files.
15123 @item ^-u^/OUTPUT=UNITS^
15124 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
15125 Only output information about compilation units.
15127 @item ^-files^/FILES^=@var{file}
15128 @cindex @option{^-files^/FILES^} (@code{gnatls})
15129 Take as arguments the files listed in text file @var{file}.
15130 Text file @var{file} may contain empty lines that are ignored.
15131 Each nonempty line should contain the name of an existing file.
15132 Several such switches may be specified simultaneously.
15134 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
15135 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
15136 @itemx ^-I^/SEARCH=^@var{dir}
15137 @itemx ^-I-^/NOCURRENT_DIRECTORY^
15139 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
15140 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
15141 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
15142 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
15143 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
15144 flags (@pxref{Switches for gnatmake}).
15146 @item --RTS=@var{rts-path}
15147 @cindex @option{--RTS} (@code{gnatls})
15148 Specifies the default location of the runtime library. Same meaning as the
15149 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15151 @item ^-v^/OUTPUT=VERBOSE^
15152 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
15153 Verbose mode. Output the complete source, object and project paths. Do not use
15154 the default column layout but instead use long format giving as much as
15155 information possible on each requested units, including special
15156 characteristics such as:
15159 @item Preelaborable
15160 The unit is preelaborable in the Ada sense.
15163 No elaboration code has been produced by the compiler for this unit.
15166 The unit is pure in the Ada sense.
15168 @item Elaborate_Body
15169 The unit contains a pragma Elaborate_Body.
15172 The unit contains a pragma Remote_Types.
15174 @item Shared_Passive
15175 The unit contains a pragma Shared_Passive.
15178 This unit is part of the predefined environment and cannot be modified
15181 @item Remote_Call_Interface
15182 The unit contains a pragma Remote_Call_Interface.
15188 @node Examples of gnatls Usage
15189 @section Example of @code{gnatls} Usage
15193 Example of using the verbose switch. Note how the source and
15194 object paths are affected by the -I switch.
15197 $ gnatls -v -I.. demo1.o
15199 GNATLS 5.03w (20041123-34)
15200 Copyright 1997-2004 Free Software Foundation, Inc.
15202 Source Search Path:
15203 <Current_Directory>
15205 /home/comar/local/adainclude/
15207 Object Search Path:
15208 <Current_Directory>
15210 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
15212 Project Search Path:
15213 <Current_Directory>
15214 /home/comar/local/lib/gnat/
15219 Kind => subprogram body
15220 Flags => No_Elab_Code
15221 Source => demo1.adb modified
15225 The following is an example of use of the dependency list.
15226 Note the use of the -s switch
15227 which gives a straight list of source files. This can be useful for
15228 building specialized scripts.
15231 $ gnatls -d demo2.o
15232 ./demo2.o demo2 OK demo2.adb
15238 $ gnatls -d -s -a demo1.o
15240 /home/comar/local/adainclude/ada.ads
15241 /home/comar/local/adainclude/a-finali.ads
15242 /home/comar/local/adainclude/a-filico.ads
15243 /home/comar/local/adainclude/a-stream.ads
15244 /home/comar/local/adainclude/a-tags.ads
15247 /home/comar/local/adainclude/gnat.ads
15248 /home/comar/local/adainclude/g-io.ads
15250 /home/comar/local/adainclude/system.ads
15251 /home/comar/local/adainclude/s-exctab.ads
15252 /home/comar/local/adainclude/s-finimp.ads
15253 /home/comar/local/adainclude/s-finroo.ads
15254 /home/comar/local/adainclude/s-secsta.ads
15255 /home/comar/local/adainclude/s-stalib.ads
15256 /home/comar/local/adainclude/s-stoele.ads
15257 /home/comar/local/adainclude/s-stratt.ads
15258 /home/comar/local/adainclude/s-tasoli.ads
15259 /home/comar/local/adainclude/s-unstyp.ads
15260 /home/comar/local/adainclude/unchconv.ads
15266 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
15268 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
15269 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
15270 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
15271 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
15272 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
15276 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
15277 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
15279 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
15280 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
15281 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
15282 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
15283 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
15284 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
15285 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
15286 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
15287 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
15288 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
15289 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
15293 @node Cleaning Up Using gnatclean
15294 @chapter Cleaning Up Using @code{gnatclean}
15296 @cindex Cleaning tool
15299 @code{gnatclean} is a tool that allows the deletion of files produced by the
15300 compiler, binder and linker, including ALI files, object files, tree files,
15301 expanded source files, library files, interface copy source files, binder
15302 generated files and executable files.
15305 * Running gnatclean::
15306 * Switches for gnatclean::
15307 @c * Examples of gnatclean Usage::
15310 @node Running gnatclean
15311 @section Running @code{gnatclean}
15314 The @code{gnatclean} command has the form:
15317 $ gnatclean switches @var{names}
15321 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
15322 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
15323 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
15326 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
15327 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
15328 the linker. In informative-only mode, specified by switch
15329 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
15330 normal mode is listed, but no file is actually deleted.
15332 @node Switches for gnatclean
15333 @section Switches for @code{gnatclean}
15336 @code{gnatclean} recognizes the following switches:
15340 @cindex @option{--version} @command{gnatclean}
15341 Display Copyright and version, then exit disregarding all other options.
15344 @cindex @option{--help} @command{gnatclean}
15345 If @option{--version} was not used, display usage, then exit disregarding
15348 @item ^--subdirs^/SUBDIRS^=subdir
15349 Actual object directory of each project file is the subdirectory subdir of the
15350 object directory specified or defauted in the project file.
15352 @item ^--unchecked-shared-lib-imports^/UNCHECKED_SHARED_LIB_IMPORTS^
15353 By default, shared library projects are not allowed to import static library
15354 projects. When this switch is used on the command line, this restriction is
15357 @item ^-c^/COMPILER_FILES_ONLY^
15358 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
15359 Only attempt to delete the files produced by the compiler, not those produced
15360 by the binder or the linker. The files that are not to be deleted are library
15361 files, interface copy files, binder generated files and executable files.
15363 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
15364 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
15365 Indicate that ALI and object files should normally be found in directory
15368 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
15369 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
15370 When using project files, if some errors or warnings are detected during
15371 parsing and verbose mode is not in effect (no use of switch
15372 ^-v^/VERBOSE^), then error lines start with the full path name of the project
15373 file, rather than its simple file name.
15376 @cindex @option{^-h^/HELP^} (@code{gnatclean})
15377 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
15379 @item ^-n^/NODELETE^
15380 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
15381 Informative-only mode. Do not delete any files. Output the list of the files
15382 that would have been deleted if this switch was not specified.
15384 @item ^-P^/PROJECT_FILE=^@var{project}
15385 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
15386 Use project file @var{project}. Only one such switch can be used.
15387 When cleaning a project file, the files produced by the compilation of the
15388 immediate sources or inherited sources of the project files are to be
15389 deleted. This is not depending on the presence or not of executable names
15390 on the command line.
15393 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
15394 Quiet output. If there are no errors, do not output anything, except in
15395 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
15396 (switch ^-n^/NODELETE^).
15398 @item ^-r^/RECURSIVE^
15399 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
15400 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
15401 clean all imported and extended project files, recursively. If this switch
15402 is not specified, only the files related to the main project file are to be
15403 deleted. This switch has no effect if no project file is specified.
15405 @item ^-v^/VERBOSE^
15406 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
15409 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
15410 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
15411 Indicates the verbosity of the parsing of GNAT project files.
15412 @xref{Switches Related to Project Files}.
15414 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
15415 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
15416 Indicates that external variable @var{name} has the value @var{value}.
15417 The Project Manager will use this value for occurrences of
15418 @code{external(name)} when parsing the project file.
15419 @xref{Switches Related to Project Files}.
15421 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
15422 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
15423 When searching for ALI and object files, look in directory
15426 @item ^-I^/SEARCH=^@var{dir}
15427 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
15428 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
15430 @item ^-I-^/NOCURRENT_DIRECTORY^
15431 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
15432 @cindex Source files, suppressing search
15433 Do not look for ALI or object files in the directory
15434 where @code{gnatclean} was invoked.
15438 @c @node Examples of gnatclean Usage
15439 @c @section Examples of @code{gnatclean} Usage
15442 @node GNAT and Libraries
15443 @chapter GNAT and Libraries
15444 @cindex Library, building, installing, using
15447 This chapter describes how to build and use libraries with GNAT, and also shows
15448 how to recompile the GNAT run-time library. You should be familiar with the
15449 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
15453 * Introduction to Libraries in GNAT::
15454 * General Ada Libraries::
15455 * Stand-alone Ada Libraries::
15456 * Rebuilding the GNAT Run-Time Library::
15459 @node Introduction to Libraries in GNAT
15460 @section Introduction to Libraries in GNAT
15463 A library is, conceptually, a collection of objects which does not have its
15464 own main thread of execution, but rather provides certain services to the
15465 applications that use it. A library can be either statically linked with the
15466 application, in which case its code is directly included in the application,
15467 or, on platforms that support it, be dynamically linked, in which case
15468 its code is shared by all applications making use of this library.
15470 GNAT supports both types of libraries.
15471 In the static case, the compiled code can be provided in different ways. The
15472 simplest approach is to provide directly the set of objects resulting from
15473 compilation of the library source files. Alternatively, you can group the
15474 objects into an archive using whatever commands are provided by the operating
15475 system. For the latter case, the objects are grouped into a shared library.
15477 In the GNAT environment, a library has three types of components:
15483 @xref{The Ada Library Information Files}.
15485 Object files, an archive or a shared library.
15489 A GNAT library may expose all its source files, which is useful for
15490 documentation purposes. Alternatively, it may expose only the units needed by
15491 an external user to make use of the library. That is to say, the specs
15492 reflecting the library services along with all the units needed to compile
15493 those specs, which can include generic bodies or any body implementing an
15494 inlined routine. In the case of @emph{stand-alone libraries} those exposed
15495 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
15497 All compilation units comprising an application, including those in a library,
15498 need to be elaborated in an order partially defined by Ada's semantics. GNAT
15499 computes the elaboration order from the @file{ALI} files and this is why they
15500 constitute a mandatory part of GNAT libraries.
15501 @emph{Stand-alone libraries} are the exception to this rule because a specific
15502 library elaboration routine is produced independently of the application(s)
15505 @node General Ada Libraries
15506 @section General Ada Libraries
15509 * Building a library::
15510 * Installing a library::
15511 * Using a library::
15514 @node Building a library
15515 @subsection Building a library
15518 The easiest way to build a library is to use the Project Manager,
15519 which supports a special type of project called a @emph{Library Project}
15520 (@pxref{Library Projects}).
15522 A project is considered a library project, when two project-level attributes
15523 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
15524 control different aspects of library configuration, additional optional
15525 project-level attributes can be specified:
15528 This attribute controls whether the library is to be static or dynamic
15530 @item Library_Version
15531 This attribute specifies the library version; this value is used
15532 during dynamic linking of shared libraries to determine if the currently
15533 installed versions of the binaries are compatible.
15535 @item Library_Options
15537 These attributes specify additional low-level options to be used during
15538 library generation, and redefine the actual application used to generate
15543 The GNAT Project Manager takes full care of the library maintenance task,
15544 including recompilation of the source files for which objects do not exist
15545 or are not up to date, assembly of the library archive, and installation of
15546 the library (i.e., copying associated source, object and @file{ALI} files
15547 to the specified location).
15549 Here is a simple library project file:
15550 @smallexample @c ada
15552 for Source_Dirs use ("src1", "src2");
15553 for Object_Dir use "obj";
15554 for Library_Name use "mylib";
15555 for Library_Dir use "lib";
15556 for Library_Kind use "dynamic";
15561 and the compilation command to build and install the library:
15563 @smallexample @c ada
15564 $ gnatmake -Pmy_lib
15568 It is not entirely trivial to perform manually all the steps required to
15569 produce a library. We recommend that you use the GNAT Project Manager
15570 for this task. In special cases where this is not desired, the necessary
15571 steps are discussed below.
15573 There are various possibilities for compiling the units that make up the
15574 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
15575 with a conventional script. For simple libraries, it is also possible to create
15576 a dummy main program which depends upon all the packages that comprise the
15577 interface of the library. This dummy main program can then be given to
15578 @command{gnatmake}, which will ensure that all necessary objects are built.
15580 After this task is accomplished, you should follow the standard procedure
15581 of the underlying operating system to produce the static or shared library.
15583 Here is an example of such a dummy program:
15584 @smallexample @c ada
15586 with My_Lib.Service1;
15587 with My_Lib.Service2;
15588 with My_Lib.Service3;
15589 procedure My_Lib_Dummy is
15597 Here are the generic commands that will build an archive or a shared library.
15600 # compiling the library
15601 $ gnatmake -c my_lib_dummy.adb
15603 # we don't need the dummy object itself
15604 $ rm my_lib_dummy.o my_lib_dummy.ali
15606 # create an archive with the remaining objects
15607 $ ar rc libmy_lib.a *.o
15608 # some systems may require "ranlib" to be run as well
15610 # or create a shared library
15611 $ gcc -shared -o libmy_lib.so *.o
15612 # some systems may require the code to have been compiled with -fPIC
15614 # remove the object files that are now in the library
15617 # Make the ALI files read-only so that gnatmake will not try to
15618 # regenerate the objects that are in the library
15623 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
15624 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
15625 be accessed by the directive @option{-l@var{xxx}} at link time.
15627 @node Installing a library
15628 @subsection Installing a library
15629 @cindex @code{ADA_PROJECT_PATH}
15630 @cindex @code{GPR_PROJECT_PATH}
15633 If you use project files, library installation is part of the library build
15634 process (@pxref{Installing a library with project files}).
15636 When project files are not an option, it is also possible, but not recommended,
15637 to install the library so that the sources needed to use the library are on the
15638 Ada source path and the ALI files & libraries be on the Ada Object path (see
15639 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
15640 administrator can place general-purpose libraries in the default compiler
15641 paths, by specifying the libraries' location in the configuration files
15642 @file{ada_source_path} and @file{ada_object_path}. These configuration files
15643 must be located in the GNAT installation tree at the same place as the gcc spec
15644 file. The location of the gcc spec file can be determined as follows:
15650 The configuration files mentioned above have a simple format: each line
15651 must contain one unique directory name.
15652 Those names are added to the corresponding path
15653 in their order of appearance in the file. The names can be either absolute
15654 or relative; in the latter case, they are relative to where theses files
15657 The files @file{ada_source_path} and @file{ada_object_path} might not be
15659 GNAT installation, in which case, GNAT will look for its run-time library in
15660 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
15661 objects and @file{ALI} files). When the files exist, the compiler does not
15662 look in @file{adainclude} and @file{adalib}, and thus the
15663 @file{ada_source_path} file
15664 must contain the location for the GNAT run-time sources (which can simply
15665 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
15666 contain the location for the GNAT run-time objects (which can simply
15669 You can also specify a new default path to the run-time library at compilation
15670 time with the switch @option{--RTS=rts-path}. You can thus choose / change
15671 the run-time library you want your program to be compiled with. This switch is
15672 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
15673 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
15675 It is possible to install a library before or after the standard GNAT
15676 library, by reordering the lines in the configuration files. In general, a
15677 library must be installed before the GNAT library if it redefines
15680 @node Using a library
15681 @subsection Using a library
15683 @noindent Once again, the project facility greatly simplifies the use of
15684 libraries. In this context, using a library is just a matter of adding a
15685 @code{with} clause in the user project. For instance, to make use of the
15686 library @code{My_Lib} shown in examples in earlier sections, you can
15689 @smallexample @c projectfile
15696 Even if you have a third-party, non-Ada library, you can still use GNAT's
15697 Project Manager facility to provide a wrapper for it. For example, the
15698 following project, when @code{with}ed by your main project, will link with the
15699 third-party library @file{liba.a}:
15701 @smallexample @c projectfile
15704 for Externally_Built use "true";
15705 for Source_Files use ();
15706 for Library_Dir use "lib";
15707 for Library_Name use "a";
15708 for Library_Kind use "static";
15712 This is an alternative to the use of @code{pragma Linker_Options}. It is
15713 especially interesting in the context of systems with several interdependent
15714 static libraries where finding a proper linker order is not easy and best be
15715 left to the tools having visibility over project dependence information.
15718 In order to use an Ada library manually, you need to make sure that this
15719 library is on both your source and object path
15720 (see @ref{Search Paths and the Run-Time Library (RTL)}
15721 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
15722 in an archive or a shared library, you need to specify the desired
15723 library at link time.
15725 For example, you can use the library @file{mylib} installed in
15726 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
15729 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
15734 This can be expressed more simply:
15739 when the following conditions are met:
15742 @file{/dir/my_lib_src} has been added by the user to the environment
15743 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
15744 @file{ada_source_path}
15746 @file{/dir/my_lib_obj} has been added by the user to the environment
15747 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
15748 @file{ada_object_path}
15750 a pragma @code{Linker_Options} has been added to one of the sources.
15753 @smallexample @c ada
15754 pragma Linker_Options ("-lmy_lib");
15758 @node Stand-alone Ada Libraries
15759 @section Stand-alone Ada Libraries
15760 @cindex Stand-alone library, building, using
15763 * Introduction to Stand-alone Libraries::
15764 * Building a Stand-alone Library::
15765 * Creating a Stand-alone Library to be used in a non-Ada context::
15766 * Restrictions in Stand-alone Libraries::
15769 @node Introduction to Stand-alone Libraries
15770 @subsection Introduction to Stand-alone Libraries
15773 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
15775 elaborate the Ada units that are included in the library. In contrast with
15776 an ordinary library, which consists of all sources, objects and @file{ALI}
15778 library, a SAL may specify a restricted subset of compilation units
15779 to serve as a library interface. In this case, the fully
15780 self-sufficient set of files will normally consist of an objects
15781 archive, the sources of interface units' specs, and the @file{ALI}
15782 files of interface units.
15783 If an interface spec contains a generic unit or an inlined subprogram,
15785 source must also be provided; if the units that must be provided in the source
15786 form depend on other units, the source and @file{ALI} files of those must
15789 The main purpose of a SAL is to minimize the recompilation overhead of client
15790 applications when a new version of the library is installed. Specifically,
15791 if the interface sources have not changed, client applications do not need to
15792 be recompiled. If, furthermore, a SAL is provided in the shared form and its
15793 version, controlled by @code{Library_Version} attribute, is not changed,
15794 then the clients do not need to be relinked.
15796 SALs also allow the library providers to minimize the amount of library source
15797 text exposed to the clients. Such ``information hiding'' might be useful or
15798 necessary for various reasons.
15800 Stand-alone libraries are also well suited to be used in an executable whose
15801 main routine is not written in Ada.
15803 @node Building a Stand-alone Library
15804 @subsection Building a Stand-alone Library
15807 GNAT's Project facility provides a simple way of building and installing
15808 stand-alone libraries; see @ref{Stand-alone Library Projects}.
15809 To be a Stand-alone Library Project, in addition to the two attributes
15810 that make a project a Library Project (@code{Library_Name} and
15811 @code{Library_Dir}; see @ref{Library Projects}), the attribute
15812 @code{Library_Interface} must be defined. For example:
15814 @smallexample @c projectfile
15816 for Library_Dir use "lib_dir";
15817 for Library_Name use "dummy";
15818 for Library_Interface use ("int1", "int1.child");
15823 Attribute @code{Library_Interface} has a non-empty string list value,
15824 each string in the list designating a unit contained in an immediate source
15825 of the project file.
15827 When a Stand-alone Library is built, first the binder is invoked to build
15828 a package whose name depends on the library name
15829 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
15830 This binder-generated package includes initialization and
15831 finalization procedures whose
15832 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
15834 above). The object corresponding to this package is included in the library.
15836 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
15837 calling of these procedures if a static SAL is built, or if a shared SAL
15839 with the project-level attribute @code{Library_Auto_Init} set to
15842 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
15843 (those that are listed in attribute @code{Library_Interface}) are copied to
15844 the Library Directory. As a consequence, only the Interface Units may be
15845 imported from Ada units outside of the library. If other units are imported,
15846 the binding phase will fail.
15848 The attribute @code{Library_Src_Dir} may be specified for a
15849 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
15850 single string value. Its value must be the path (absolute or relative to the
15851 project directory) of an existing directory. This directory cannot be the
15852 object directory or one of the source directories, but it can be the same as
15853 the library directory. The sources of the Interface
15854 Units of the library that are needed by an Ada client of the library will be
15855 copied to the designated directory, called the Interface Copy directory.
15856 These sources include the specs of the Interface Units, but they may also
15857 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
15858 are used, or when there is a generic unit in the spec. Before the sources
15859 are copied to the Interface Copy directory, an attempt is made to delete all
15860 files in the Interface Copy directory.
15862 Building stand-alone libraries by hand is somewhat tedious, but for those
15863 occasions when it is necessary here are the steps that you need to perform:
15866 Compile all library sources.
15869 Invoke the binder with the switch @option{-n} (No Ada main program),
15870 with all the @file{ALI} files of the interfaces, and
15871 with the switch @option{-L} to give specific names to the @code{init}
15872 and @code{final} procedures. For example:
15874 gnatbind -n int1.ali int2.ali -Lsal1
15878 Compile the binder generated file:
15884 Link the dynamic library with all the necessary object files,
15885 indicating to the linker the names of the @code{init} (and possibly
15886 @code{final}) procedures for automatic initialization (and finalization).
15887 The built library should be placed in a directory different from
15888 the object directory.
15891 Copy the @code{ALI} files of the interface to the library directory,
15892 add in this copy an indication that it is an interface to a SAL
15893 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
15894 with letter ``P'') and make the modified copy of the @file{ALI} file
15899 Using SALs is not different from using other libraries
15900 (see @ref{Using a library}).
15902 @node Creating a Stand-alone Library to be used in a non-Ada context
15903 @subsection Creating a Stand-alone Library to be used in a non-Ada context
15906 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
15909 The only extra step required is to ensure that library interface subprograms
15910 are compatible with the main program, by means of @code{pragma Export}
15911 or @code{pragma Convention}.
15913 Here is an example of simple library interface for use with C main program:
15915 @smallexample @c ada
15916 package My_Package is
15918 procedure Do_Something;
15919 pragma Export (C, Do_Something, "do_something");
15921 procedure Do_Something_Else;
15922 pragma Export (C, Do_Something_Else, "do_something_else");
15928 On the foreign language side, you must provide a ``foreign'' view of the
15929 library interface; remember that it should contain elaboration routines in
15930 addition to interface subprograms.
15932 The example below shows the content of @code{mylib_interface.h} (note
15933 that there is no rule for the naming of this file, any name can be used)
15935 /* the library elaboration procedure */
15936 extern void mylibinit (void);
15938 /* the library finalization procedure */
15939 extern void mylibfinal (void);
15941 /* the interface exported by the library */
15942 extern void do_something (void);
15943 extern void do_something_else (void);
15947 Libraries built as explained above can be used from any program, provided
15948 that the elaboration procedures (named @code{mylibinit} in the previous
15949 example) are called before the library services are used. Any number of
15950 libraries can be used simultaneously, as long as the elaboration
15951 procedure of each library is called.
15953 Below is an example of a C program that uses the @code{mylib} library.
15956 #include "mylib_interface.h"
15961 /* First, elaborate the library before using it */
15964 /* Main program, using the library exported entities */
15966 do_something_else ();
15968 /* Library finalization at the end of the program */
15975 Note that invoking any library finalization procedure generated by
15976 @code{gnatbind} shuts down the Ada run-time environment.
15978 finalization of all Ada libraries must be performed at the end of the program.
15979 No call to these libraries or to the Ada run-time library should be made
15980 after the finalization phase.
15982 @node Restrictions in Stand-alone Libraries
15983 @subsection Restrictions in Stand-alone Libraries
15986 The pragmas listed below should be used with caution inside libraries,
15987 as they can create incompatibilities with other Ada libraries:
15989 @item pragma @code{Locking_Policy}
15990 @item pragma @code{Queuing_Policy}
15991 @item pragma @code{Task_Dispatching_Policy}
15992 @item pragma @code{Unreserve_All_Interrupts}
15996 When using a library that contains such pragmas, the user must make sure
15997 that all libraries use the same pragmas with the same values. Otherwise,
15998 @code{Program_Error} will
15999 be raised during the elaboration of the conflicting
16000 libraries. The usage of these pragmas and its consequences for the user
16001 should therefore be well documented.
16003 Similarly, the traceback in the exception occurrence mechanism should be
16004 enabled or disabled in a consistent manner across all libraries.
16005 Otherwise, Program_Error will be raised during the elaboration of the
16006 conflicting libraries.
16008 If the @code{Version} or @code{Body_Version}
16009 attributes are used inside a library, then you need to
16010 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
16011 libraries, so that version identifiers can be properly computed.
16012 In practice these attributes are rarely used, so this is unlikely
16013 to be a consideration.
16015 @node Rebuilding the GNAT Run-Time Library
16016 @section Rebuilding the GNAT Run-Time Library
16017 @cindex GNAT Run-Time Library, rebuilding
16018 @cindex Building the GNAT Run-Time Library
16019 @cindex Rebuilding the GNAT Run-Time Library
16020 @cindex Run-Time Library, rebuilding
16023 It may be useful to recompile the GNAT library in various contexts, the
16024 most important one being the use of partition-wide configuration pragmas
16025 such as @code{Normalize_Scalars}. A special Makefile called
16026 @code{Makefile.adalib} is provided to that effect and can be found in
16027 the directory containing the GNAT library. The location of this
16028 directory depends on the way the GNAT environment has been installed and can
16029 be determined by means of the command:
16036 The last entry in the object search path usually contains the
16037 gnat library. This Makefile contains its own documentation and in
16038 particular the set of instructions needed to rebuild a new library and
16041 @node Using the GNU make Utility
16042 @chapter Using the GNU @code{make} Utility
16046 This chapter offers some examples of makefiles that solve specific
16047 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
16048 make, make, GNU @code{make}}), nor does it try to replace the
16049 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
16051 All the examples in this section are specific to the GNU version of
16052 make. Although @command{make} is a standard utility, and the basic language
16053 is the same, these examples use some advanced features found only in
16057 * Using gnatmake in a Makefile::
16058 * Automatically Creating a List of Directories::
16059 * Generating the Command Line Switches::
16060 * Overcoming Command Line Length Limits::
16063 @node Using gnatmake in a Makefile
16064 @section Using gnatmake in a Makefile
16069 Complex project organizations can be handled in a very powerful way by
16070 using GNU make combined with gnatmake. For instance, here is a Makefile
16071 which allows you to build each subsystem of a big project into a separate
16072 shared library. Such a makefile allows you to significantly reduce the link
16073 time of very big applications while maintaining full coherence at
16074 each step of the build process.
16076 The list of dependencies are handled automatically by
16077 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
16078 the appropriate directories.
16080 Note that you should also read the example on how to automatically
16081 create the list of directories
16082 (@pxref{Automatically Creating a List of Directories})
16083 which might help you in case your project has a lot of subdirectories.
16088 @font@heightrm=cmr8
16091 ## This Makefile is intended to be used with the following directory
16093 ## - The sources are split into a series of csc (computer software components)
16094 ## Each of these csc is put in its own directory.
16095 ## Their name are referenced by the directory names.
16096 ## They will be compiled into shared library (although this would also work
16097 ## with static libraries
16098 ## - The main program (and possibly other packages that do not belong to any
16099 ## csc is put in the top level directory (where the Makefile is).
16100 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
16101 ## \_ second_csc (sources) __ lib (will contain the library)
16103 ## Although this Makefile is build for shared library, it is easy to modify
16104 ## to build partial link objects instead (modify the lines with -shared and
16107 ## With this makefile, you can change any file in the system or add any new
16108 ## file, and everything will be recompiled correctly (only the relevant shared
16109 ## objects will be recompiled, and the main program will be re-linked).
16111 # The list of computer software component for your project. This might be
16112 # generated automatically.
16115 # Name of the main program (no extension)
16118 # If we need to build objects with -fPIC, uncomment the following line
16121 # The following variable should give the directory containing libgnat.so
16122 # You can get this directory through 'gnatls -v'. This is usually the last
16123 # directory in the Object_Path.
16126 # The directories for the libraries
16127 # (This macro expands the list of CSC to the list of shared libraries, you
16128 # could simply use the expanded form:
16129 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
16130 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
16132 $@{MAIN@}: objects $@{LIB_DIR@}
16133 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
16134 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
16137 # recompile the sources
16138 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
16140 # Note: In a future version of GNAT, the following commands will be simplified
16141 # by a new tool, gnatmlib
16143 mkdir -p $@{dir $@@ @}
16144 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
16145 cd $@{dir $@@ @} && cp -f ../*.ali .
16147 # The dependencies for the modules
16148 # Note that we have to force the expansion of *.o, since in some cases
16149 # make won't be able to do it itself.
16150 aa/lib/libaa.so: $@{wildcard aa/*.o@}
16151 bb/lib/libbb.so: $@{wildcard bb/*.o@}
16152 cc/lib/libcc.so: $@{wildcard cc/*.o@}
16154 # Make sure all of the shared libraries are in the path before starting the
16157 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
16160 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
16161 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
16162 $@{RM@} $@{CSC_LIST:%=%/*.o@}
16163 $@{RM@} *.o *.ali $@{MAIN@}
16166 @node Automatically Creating a List of Directories
16167 @section Automatically Creating a List of Directories
16170 In most makefiles, you will have to specify a list of directories, and
16171 store it in a variable. For small projects, it is often easier to
16172 specify each of them by hand, since you then have full control over what
16173 is the proper order for these directories, which ones should be
16176 However, in larger projects, which might involve hundreds of
16177 subdirectories, it might be more convenient to generate this list
16180 The example below presents two methods. The first one, although less
16181 general, gives you more control over the list. It involves wildcard
16182 characters, that are automatically expanded by @command{make}. Its
16183 shortcoming is that you need to explicitly specify some of the
16184 organization of your project, such as for instance the directory tree
16185 depth, whether some directories are found in a separate tree, @enddots{}
16187 The second method is the most general one. It requires an external
16188 program, called @command{find}, which is standard on all Unix systems. All
16189 the directories found under a given root directory will be added to the
16195 @font@heightrm=cmr8
16198 # The examples below are based on the following directory hierarchy:
16199 # All the directories can contain any number of files
16200 # ROOT_DIRECTORY -> a -> aa -> aaa
16203 # -> b -> ba -> baa
16206 # This Makefile creates a variable called DIRS, that can be reused any time
16207 # you need this list (see the other examples in this section)
16209 # The root of your project's directory hierarchy
16213 # First method: specify explicitly the list of directories
16214 # This allows you to specify any subset of all the directories you need.
16217 DIRS := a/aa/ a/ab/ b/ba/
16220 # Second method: use wildcards
16221 # Note that the argument(s) to wildcard below should end with a '/'.
16222 # Since wildcards also return file names, we have to filter them out
16223 # to avoid duplicate directory names.
16224 # We thus use make's @code{dir} and @code{sort} functions.
16225 # It sets DIRs to the following value (note that the directories aaa and baa
16226 # are not given, unless you change the arguments to wildcard).
16227 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
16230 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
16231 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
16234 # Third method: use an external program
16235 # This command is much faster if run on local disks, avoiding NFS slowdowns.
16236 # This is the most complete command: it sets DIRs to the following value:
16237 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
16240 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
16244 @node Generating the Command Line Switches
16245 @section Generating the Command Line Switches
16248 Once you have created the list of directories as explained in the
16249 previous section (@pxref{Automatically Creating a List of Directories}),
16250 you can easily generate the command line arguments to pass to gnatmake.
16252 For the sake of completeness, this example assumes that the source path
16253 is not the same as the object path, and that you have two separate lists
16257 # see "Automatically creating a list of directories" to create
16262 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
16263 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
16266 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
16269 @node Overcoming Command Line Length Limits
16270 @section Overcoming Command Line Length Limits
16273 One problem that might be encountered on big projects is that many
16274 operating systems limit the length of the command line. It is thus hard to give
16275 gnatmake the list of source and object directories.
16277 This example shows how you can set up environment variables, which will
16278 make @command{gnatmake} behave exactly as if the directories had been
16279 specified on the command line, but have a much higher length limit (or
16280 even none on most systems).
16282 It assumes that you have created a list of directories in your Makefile,
16283 using one of the methods presented in
16284 @ref{Automatically Creating a List of Directories}.
16285 For the sake of completeness, we assume that the object
16286 path (where the ALI files are found) is different from the sources patch.
16288 Note a small trick in the Makefile below: for efficiency reasons, we
16289 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
16290 expanded immediately by @code{make}. This way we overcome the standard
16291 make behavior which is to expand the variables only when they are
16294 On Windows, if you are using the standard Windows command shell, you must
16295 replace colons with semicolons in the assignments to these variables.
16300 @font@heightrm=cmr8
16303 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
16304 # This is the same thing as putting the -I arguments on the command line.
16305 # (the equivalent of using -aI on the command line would be to define
16306 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
16307 # You can of course have different values for these variables.
16309 # Note also that we need to keep the previous values of these variables, since
16310 # they might have been set before running 'make' to specify where the GNAT
16311 # library is installed.
16313 # see "Automatically creating a list of directories" to create these
16319 space:=$@{empty@} $@{empty@}
16320 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
16321 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
16322 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
16323 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
16324 export ADA_INCLUDE_PATH
16325 export ADA_OBJECT_PATH
16332 @node Memory Management Issues
16333 @chapter Memory Management Issues
16336 This chapter describes some useful memory pools provided in the GNAT library
16337 and in particular the GNAT Debug Pool facility, which can be used to detect
16338 incorrect uses of access values (including ``dangling references'').
16340 It also describes the @command{gnatmem} tool, which can be used to track down
16345 * Some Useful Memory Pools::
16346 * The GNAT Debug Pool Facility::
16348 * The gnatmem Tool::
16352 @node Some Useful Memory Pools
16353 @section Some Useful Memory Pools
16354 @findex Memory Pool
16355 @cindex storage, pool
16358 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
16359 storage pool. Allocations use the standard system call @code{malloc} while
16360 deallocations use the standard system call @code{free}. No reclamation is
16361 performed when the pool goes out of scope. For performance reasons, the
16362 standard default Ada allocators/deallocators do not use any explicit storage
16363 pools but if they did, they could use this storage pool without any change in
16364 behavior. That is why this storage pool is used when the user
16365 manages to make the default implicit allocator explicit as in this example:
16366 @smallexample @c ada
16367 type T1 is access Something;
16368 -- no Storage pool is defined for T2
16369 type T2 is access Something_Else;
16370 for T2'Storage_Pool use T1'Storage_Pool;
16371 -- the above is equivalent to
16372 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
16376 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
16377 pool. The allocation strategy is similar to @code{Pool_Local}'s
16378 except that the all
16379 storage allocated with this pool is reclaimed when the pool object goes out of
16380 scope. This pool provides a explicit mechanism similar to the implicit one
16381 provided by several Ada 83 compilers for allocations performed through a local
16382 access type and whose purpose was to reclaim memory when exiting the
16383 scope of a given local access. As an example, the following program does not
16384 leak memory even though it does not perform explicit deallocation:
16386 @smallexample @c ada
16387 with System.Pool_Local;
16388 procedure Pooloc1 is
16389 procedure Internal is
16390 type A is access Integer;
16391 X : System.Pool_Local.Unbounded_Reclaim_Pool;
16392 for A'Storage_Pool use X;
16395 for I in 1 .. 50 loop
16400 for I in 1 .. 100 loop
16407 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
16408 @code{Storage_Size} is specified for an access type.
16409 The whole storage for the pool is
16410 allocated at once, usually on the stack at the point where the access type is
16411 elaborated. It is automatically reclaimed when exiting the scope where the
16412 access type is defined. This package is not intended to be used directly by the
16413 user and it is implicitly used for each such declaration:
16415 @smallexample @c ada
16416 type T1 is access Something;
16417 for T1'Storage_Size use 10_000;
16420 @node The GNAT Debug Pool Facility
16421 @section The GNAT Debug Pool Facility
16423 @cindex storage, pool, memory corruption
16426 The use of unchecked deallocation and unchecked conversion can easily
16427 lead to incorrect memory references. The problems generated by such
16428 references are usually difficult to tackle because the symptoms can be
16429 very remote from the origin of the problem. In such cases, it is
16430 very helpful to detect the problem as early as possible. This is the
16431 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
16433 In order to use the GNAT specific debugging pool, the user must
16434 associate a debug pool object with each of the access types that may be
16435 related to suspected memory problems. See Ada Reference Manual 13.11.
16436 @smallexample @c ada
16437 type Ptr is access Some_Type;
16438 Pool : GNAT.Debug_Pools.Debug_Pool;
16439 for Ptr'Storage_Pool use Pool;
16443 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
16444 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
16445 allow the user to redefine allocation and deallocation strategies. They
16446 also provide a checkpoint for each dereference, through the use of
16447 the primitive operation @code{Dereference} which is implicitly called at
16448 each dereference of an access value.
16450 Once an access type has been associated with a debug pool, operations on
16451 values of the type may raise four distinct exceptions,
16452 which correspond to four potential kinds of memory corruption:
16455 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
16457 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
16459 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
16461 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
16465 For types associated with a Debug_Pool, dynamic allocation is performed using
16466 the standard GNAT allocation routine. References to all allocated chunks of
16467 memory are kept in an internal dictionary. Several deallocation strategies are
16468 provided, whereupon the user can choose to release the memory to the system,
16469 keep it allocated for further invalid access checks, or fill it with an easily
16470 recognizable pattern for debug sessions. The memory pattern is the old IBM
16471 hexadecimal convention: @code{16#DEADBEEF#}.
16473 See the documentation in the file g-debpoo.ads for more information on the
16474 various strategies.
16476 Upon each dereference, a check is made that the access value denotes a
16477 properly allocated memory location. Here is a complete example of use of
16478 @code{Debug_Pools}, that includes typical instances of memory corruption:
16479 @smallexample @c ada
16483 with Gnat.Io; use Gnat.Io;
16484 with Unchecked_Deallocation;
16485 with Unchecked_Conversion;
16486 with GNAT.Debug_Pools;
16487 with System.Storage_Elements;
16488 with Ada.Exceptions; use Ada.Exceptions;
16489 procedure Debug_Pool_Test is
16491 type T is access Integer;
16492 type U is access all T;
16494 P : GNAT.Debug_Pools.Debug_Pool;
16495 for T'Storage_Pool use P;
16497 procedure Free is new Unchecked_Deallocation (Integer, T);
16498 function UC is new Unchecked_Conversion (U, T);
16501 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
16511 Put_Line (Integer'Image(B.all));
16513 when E : others => Put_Line ("raised: " & Exception_Name (E));
16518 when E : others => Put_Line ("raised: " & Exception_Name (E));
16522 Put_Line (Integer'Image(B.all));
16524 when E : others => Put_Line ("raised: " & Exception_Name (E));
16529 when E : others => Put_Line ("raised: " & Exception_Name (E));
16532 end Debug_Pool_Test;
16536 The debug pool mechanism provides the following precise diagnostics on the
16537 execution of this erroneous program:
16540 Total allocated bytes : 0
16541 Total deallocated bytes : 0
16542 Current Water Mark: 0
16546 Total allocated bytes : 8
16547 Total deallocated bytes : 0
16548 Current Water Mark: 8
16551 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
16552 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
16553 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
16554 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
16556 Total allocated bytes : 8
16557 Total deallocated bytes : 4
16558 Current Water Mark: 4
16563 @node The gnatmem Tool
16564 @section The @command{gnatmem} Tool
16568 The @code{gnatmem} utility monitors dynamic allocation and
16569 deallocation activity in a program, and displays information about
16570 incorrect deallocations and possible sources of memory leaks.
16571 It is designed to work in association with a static runtime library
16572 only and in this context provides three types of information:
16575 General information concerning memory management, such as the total
16576 number of allocations and deallocations, the amount of allocated
16577 memory and the high water mark, i.e.@: the largest amount of allocated
16578 memory in the course of program execution.
16581 Backtraces for all incorrect deallocations, that is to say deallocations
16582 which do not correspond to a valid allocation.
16585 Information on each allocation that is potentially the origin of a memory
16590 * Running gnatmem::
16591 * Switches for gnatmem::
16592 * Example of gnatmem Usage::
16595 @node Running gnatmem
16596 @subsection Running @code{gnatmem}
16599 @code{gnatmem} makes use of the output created by the special version of
16600 allocation and deallocation routines that record call information. This
16601 allows to obtain accurate dynamic memory usage history at a minimal cost to
16602 the execution speed. Note however, that @code{gnatmem} is not supported on
16603 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
16604 Solaris and Windows NT/2000/XP (x86).
16607 The @code{gnatmem} command has the form
16610 @c $ gnatmem @ovar{switches} user_program
16611 @c Expanding @ovar macro inline (explanation in macro def comments)
16612 $ gnatmem @r{[}@var{switches}@r{]} @var{user_program}
16616 The program must have been linked with the instrumented version of the
16617 allocation and deallocation routines. This is done by linking with the
16618 @file{libgmem.a} library. For correct symbolic backtrace information,
16619 the user program should be compiled with debugging options
16620 (see @ref{Switches for gcc}). For example to build @file{my_program}:
16623 $ gnatmake -g my_program -largs -lgmem
16627 As library @file{libgmem.a} contains an alternate body for package
16628 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
16629 when an executable is linked with library @file{libgmem.a}. It is then not
16630 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
16633 When @file{my_program} is executed, the file @file{gmem.out} is produced.
16634 This file contains information about all allocations and deallocations
16635 performed by the program. It is produced by the instrumented allocations and
16636 deallocations routines and will be used by @code{gnatmem}.
16638 In order to produce symbolic backtrace information for allocations and
16639 deallocations performed by the GNAT run-time library, you need to use a
16640 version of that library that has been compiled with the @option{-g} switch
16641 (see @ref{Rebuilding the GNAT Run-Time Library}).
16643 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
16644 examine. If the location of @file{gmem.out} file was not explicitly supplied by
16645 @option{-i} switch, gnatmem will assume that this file can be found in the
16646 current directory. For example, after you have executed @file{my_program},
16647 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
16650 $ gnatmem my_program
16654 This will produce the output with the following format:
16656 *************** debut cc
16658 $ gnatmem my_program
16662 Total number of allocations : 45
16663 Total number of deallocations : 6
16664 Final Water Mark (non freed mem) : 11.29 Kilobytes
16665 High Water Mark : 11.40 Kilobytes
16670 Allocation Root # 2
16671 -------------------
16672 Number of non freed allocations : 11
16673 Final Water Mark (non freed mem) : 1.16 Kilobytes
16674 High Water Mark : 1.27 Kilobytes
16676 my_program.adb:23 my_program.alloc
16682 The first block of output gives general information. In this case, the
16683 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
16684 Unchecked_Deallocation routine occurred.
16687 Subsequent paragraphs display information on all allocation roots.
16688 An allocation root is a specific point in the execution of the program
16689 that generates some dynamic allocation, such as a ``@code{@b{new}}''
16690 construct. This root is represented by an execution backtrace (or subprogram
16691 call stack). By default the backtrace depth for allocations roots is 1, so
16692 that a root corresponds exactly to a source location. The backtrace can
16693 be made deeper, to make the root more specific.
16695 @node Switches for gnatmem
16696 @subsection Switches for @code{gnatmem}
16699 @code{gnatmem} recognizes the following switches:
16704 @cindex @option{-q} (@code{gnatmem})
16705 Quiet. Gives the minimum output needed to identify the origin of the
16706 memory leaks. Omits statistical information.
16709 @cindex @var{N} (@code{gnatmem})
16710 N is an integer literal (usually between 1 and 10) which controls the
16711 depth of the backtraces defining allocation root. The default value for
16712 N is 1. The deeper the backtrace, the more precise the localization of
16713 the root. Note that the total number of roots can depend on this
16714 parameter. This parameter must be specified @emph{before} the name of the
16715 executable to be analyzed, to avoid ambiguity.
16718 @cindex @option{-b} (@code{gnatmem})
16719 This switch has the same effect as just depth parameter.
16721 @item -i @var{file}
16722 @cindex @option{-i} (@code{gnatmem})
16723 Do the @code{gnatmem} processing starting from @file{file}, rather than
16724 @file{gmem.out} in the current directory.
16727 @cindex @option{-m} (@code{gnatmem})
16728 This switch causes @code{gnatmem} to mask the allocation roots that have less
16729 than n leaks. The default value is 1. Specifying the value of 0 will allow to
16730 examine even the roots that didn't result in leaks.
16733 @cindex @option{-s} (@code{gnatmem})
16734 This switch causes @code{gnatmem} to sort the allocation roots according to the
16735 specified order of sort criteria, each identified by a single letter. The
16736 currently supported criteria are @code{n, h, w} standing respectively for
16737 number of unfreed allocations, high watermark, and final watermark
16738 corresponding to a specific root. The default order is @code{nwh}.
16742 @node Example of gnatmem Usage
16743 @subsection Example of @code{gnatmem} Usage
16746 The following example shows the use of @code{gnatmem}
16747 on a simple memory-leaking program.
16748 Suppose that we have the following Ada program:
16750 @smallexample @c ada
16753 with Unchecked_Deallocation;
16754 procedure Test_Gm is
16756 type T is array (1..1000) of Integer;
16757 type Ptr is access T;
16758 procedure Free is new Unchecked_Deallocation (T, Ptr);
16761 procedure My_Alloc is
16766 procedure My_DeAlloc is
16774 for I in 1 .. 5 loop
16775 for J in I .. 5 loop
16786 The program needs to be compiled with debugging option and linked with
16787 @code{gmem} library:
16790 $ gnatmake -g test_gm -largs -lgmem
16794 Then we execute the program as usual:
16801 Then @code{gnatmem} is invoked simply with
16807 which produces the following output (result may vary on different platforms):
16812 Total number of allocations : 18
16813 Total number of deallocations : 5
16814 Final Water Mark (non freed mem) : 53.00 Kilobytes
16815 High Water Mark : 56.90 Kilobytes
16817 Allocation Root # 1
16818 -------------------
16819 Number of non freed allocations : 11
16820 Final Water Mark (non freed mem) : 42.97 Kilobytes
16821 High Water Mark : 46.88 Kilobytes
16823 test_gm.adb:11 test_gm.my_alloc
16825 Allocation Root # 2
16826 -------------------
16827 Number of non freed allocations : 1
16828 Final Water Mark (non freed mem) : 10.02 Kilobytes
16829 High Water Mark : 10.02 Kilobytes
16831 s-secsta.adb:81 system.secondary_stack.ss_init
16833 Allocation Root # 3
16834 -------------------
16835 Number of non freed allocations : 1
16836 Final Water Mark (non freed mem) : 12 Bytes
16837 High Water Mark : 12 Bytes
16839 s-secsta.adb:181 system.secondary_stack.ss_init
16843 Note that the GNAT run time contains itself a certain number of
16844 allocations that have no corresponding deallocation,
16845 as shown here for root #2 and root
16846 #3. This is a normal behavior when the number of non-freed allocations
16847 is one, it allocates dynamic data structures that the run time needs for
16848 the complete lifetime of the program. Note also that there is only one
16849 allocation root in the user program with a single line back trace:
16850 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
16851 program shows that 'My_Alloc' is called at 2 different points in the
16852 source (line 21 and line 24). If those two allocation roots need to be
16853 distinguished, the backtrace depth parameter can be used:
16856 $ gnatmem 3 test_gm
16860 which will give the following output:
16865 Total number of allocations : 18
16866 Total number of deallocations : 5
16867 Final Water Mark (non freed mem) : 53.00 Kilobytes
16868 High Water Mark : 56.90 Kilobytes
16870 Allocation Root # 1
16871 -------------------
16872 Number of non freed allocations : 10
16873 Final Water Mark (non freed mem) : 39.06 Kilobytes
16874 High Water Mark : 42.97 Kilobytes
16876 test_gm.adb:11 test_gm.my_alloc
16877 test_gm.adb:24 test_gm
16878 b_test_gm.c:52 main
16880 Allocation Root # 2
16881 -------------------
16882 Number of non freed allocations : 1
16883 Final Water Mark (non freed mem) : 10.02 Kilobytes
16884 High Water Mark : 10.02 Kilobytes
16886 s-secsta.adb:81 system.secondary_stack.ss_init
16887 s-secsta.adb:283 <system__secondary_stack___elabb>
16888 b_test_gm.c:33 adainit
16890 Allocation Root # 3
16891 -------------------
16892 Number of non freed allocations : 1
16893 Final Water Mark (non freed mem) : 3.91 Kilobytes
16894 High Water Mark : 3.91 Kilobytes
16896 test_gm.adb:11 test_gm.my_alloc
16897 test_gm.adb:21 test_gm
16898 b_test_gm.c:52 main
16900 Allocation Root # 4
16901 -------------------
16902 Number of non freed allocations : 1
16903 Final Water Mark (non freed mem) : 12 Bytes
16904 High Water Mark : 12 Bytes
16906 s-secsta.adb:181 system.secondary_stack.ss_init
16907 s-secsta.adb:283 <system__secondary_stack___elabb>
16908 b_test_gm.c:33 adainit
16912 The allocation root #1 of the first example has been split in 2 roots #1
16913 and #3 thanks to the more precise associated backtrace.
16917 @node Stack Related Facilities
16918 @chapter Stack Related Facilities
16921 This chapter describes some useful tools associated with stack
16922 checking and analysis. In
16923 particular, it deals with dynamic and static stack usage measurements.
16926 * Stack Overflow Checking::
16927 * Static Stack Usage Analysis::
16928 * Dynamic Stack Usage Analysis::
16931 @node Stack Overflow Checking
16932 @section Stack Overflow Checking
16933 @cindex Stack Overflow Checking
16934 @cindex -fstack-check
16937 For most operating systems, @command{gcc} does not perform stack overflow
16938 checking by default. This means that if the main environment task or
16939 some other task exceeds the available stack space, then unpredictable
16940 behavior will occur. Most native systems offer some level of protection by
16941 adding a guard page at the end of each task stack. This mechanism is usually
16942 not enough for dealing properly with stack overflow situations because
16943 a large local variable could ``jump'' above the guard page.
16944 Furthermore, when the
16945 guard page is hit, there may not be any space left on the stack for executing
16946 the exception propagation code. Enabling stack checking avoids
16949 To activate stack checking, compile all units with the gcc option
16950 @option{-fstack-check}. For example:
16953 gcc -c -fstack-check package1.adb
16957 Units compiled with this option will generate extra instructions to check
16958 that any use of the stack (for procedure calls or for declaring local
16959 variables in declare blocks) does not exceed the available stack space.
16960 If the space is exceeded, then a @code{Storage_Error} exception is raised.
16962 For declared tasks, the stack size is controlled by the size
16963 given in an applicable @code{Storage_Size} pragma or by the value specified
16964 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
16965 the default size as defined in the GNAT runtime otherwise.
16967 For the environment task, the stack size depends on
16968 system defaults and is unknown to the compiler. Stack checking
16969 may still work correctly if a fixed
16970 size stack is allocated, but this cannot be guaranteed.
16972 To ensure that a clean exception is signalled for stack
16973 overflow, set the environment variable
16974 @env{GNAT_STACK_LIMIT} to indicate the maximum
16975 stack area that can be used, as in:
16976 @cindex GNAT_STACK_LIMIT
16979 SET GNAT_STACK_LIMIT 1600
16983 The limit is given in kilobytes, so the above declaration would
16984 set the stack limit of the environment task to 1.6 megabytes.
16985 Note that the only purpose of this usage is to limit the amount
16986 of stack used by the environment task. If it is necessary to
16987 increase the amount of stack for the environment task, then this
16988 is an operating systems issue, and must be addressed with the
16989 appropriate operating systems commands.
16992 To have a fixed size stack in the environment task, the stack must be put
16993 in the P0 address space and its size specified. Use these switches to
16997 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
17001 The quotes are required to keep case. The number after @samp{STACK=} is the
17002 size of the environmental task stack in pagelets (512 bytes). In this example
17003 the stack size is about 2 megabytes.
17006 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
17007 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
17008 more details about the @option{/p0image} qualifier and the @option{stack}
17012 @node Static Stack Usage Analysis
17013 @section Static Stack Usage Analysis
17014 @cindex Static Stack Usage Analysis
17015 @cindex -fstack-usage
17018 A unit compiled with @option{-fstack-usage} will generate an extra file
17020 the maximum amount of stack used, on a per-function basis.
17021 The file has the same
17022 basename as the target object file with a @file{.su} extension.
17023 Each line of this file is made up of three fields:
17027 The name of the function.
17031 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
17034 The second field corresponds to the size of the known part of the function
17037 The qualifier @code{static} means that the function frame size
17039 It usually means that all local variables have a static size.
17040 In this case, the second field is a reliable measure of the function stack
17043 The qualifier @code{dynamic} means that the function frame size is not static.
17044 It happens mainly when some local variables have a dynamic size. When this
17045 qualifier appears alone, the second field is not a reliable measure
17046 of the function stack analysis. When it is qualified with @code{bounded}, it
17047 means that the second field is a reliable maximum of the function stack
17050 @node Dynamic Stack Usage Analysis
17051 @section Dynamic Stack Usage Analysis
17054 It is possible to measure the maximum amount of stack used by a task, by
17055 adding a switch to @command{gnatbind}, as:
17058 $ gnatbind -u0 file
17062 With this option, at each task termination, its stack usage is output on
17064 It is not always convenient to output the stack usage when the program
17065 is still running. Hence, it is possible to delay this output until program
17066 termination. for a given number of tasks specified as the argument of the
17067 @option{-u} option. For instance:
17070 $ gnatbind -u100 file
17074 will buffer the stack usage information of the first 100 tasks to terminate and
17075 output this info at program termination. Results are displayed in four
17079 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
17086 is a number associated with each task.
17089 is the name of the task analyzed.
17092 is the maximum size for the stack.
17095 is the measure done by the stack analyzer. In order to prevent overflow, the stack
17096 is not entirely analyzed, and it's not possible to know exactly how
17097 much has actually been used. The report thus contains the theoretical stack usage
17098 (Value) and the possible variation (Variation) around this value.
17103 The environment task stack, e.g., the stack that contains the main unit, is
17104 only processed when the environment variable GNAT_STACK_LIMIT is set.
17107 @c *********************************
17109 @c *********************************
17110 @node Verifying Properties Using gnatcheck
17111 @chapter Verifying Properties Using @command{gnatcheck}
17113 @cindex @command{gnatcheck}
17116 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
17117 of Ada source files according to a given set of semantic rules.
17120 In order to check compliance with a given rule, @command{gnatcheck} has to
17121 semantically analyze the Ada sources.
17122 Therefore, checks can only be performed on
17123 legal Ada units. Moreover, when a unit depends semantically upon units located
17124 outside the current directory, the source search path has to be provided when
17125 calling @command{gnatcheck}, either through a specified project file or
17126 through @command{gnatcheck} switches as described below.
17128 A number of rules are predefined in @command{gnatcheck} and are described
17129 later in this chapter.
17130 You can also add new rules, by modifying the @command{gnatcheck} code and
17131 rebuilding the tool. In order to add a simple rule making some local checks,
17132 a small amount of straightforward ASIS-based programming is usually needed.
17134 Project support for @command{gnatcheck} is provided by the GNAT
17135 driver (see @ref{The GNAT Driver and Project Files}).
17137 Invoking @command{gnatcheck} on the command line has the form:
17140 @c $ gnatcheck @ovar{switches} @{@var{filename}@}
17141 @c @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
17142 @c @r{[}-cargs @var{gcc_switches}@r{]} -rules @var{rule_options}
17143 @c Expanding @ovar macro inline (explanation in macro def comments)
17144 $ gnatcheck @r{[}@var{switches}@r{]} @{@var{filename}@}
17145 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
17146 @r{[}-cargs @var{gcc_switches}@r{]} -rules @var{rule_options}
17153 @var{switches} specify the general tool options
17156 Each @var{filename} is the name (including the extension) of a source
17157 file to process. ``Wildcards'' are allowed, and
17158 the file name may contain path information.
17161 Each @var{arg_list_filename} is the name (including the extension) of a text
17162 file containing the names of the source files to process, separated by spaces
17166 @var{gcc_switches} is a list of switches for
17167 @command{gcc}. They will be passed on to all compiler invocations made by
17168 @command{gnatcheck} to generate the ASIS trees. Here you can provide
17169 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17170 and use the @option{-gnatec} switch to set the configuration file.
17173 @var{rule_options} is a list of options for controlling a set of
17174 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
17178 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be
17182 * Format of the Report File::
17183 * General gnatcheck Switches::
17184 * gnatcheck Rule Options::
17185 * Adding the Results of Compiler Checks to gnatcheck Output::
17186 * Project-Wide Checks::
17188 * Predefined Rules::
17189 * Example of gnatcheck Usage::
17192 @node Format of the Report File
17193 @section Format of the Report File
17194 @cindex Report file (for @code{gnatcheck})
17197 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
17199 It also creates a text file that
17200 contains the complete report of the last gnatcheck run. By default this file
17201 is named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the
17202 current directory; the @option{^-o^/OUTPUT^} option can be used to change the
17203 name and/or location of the report file. This report contains:
17205 @item date and time of @command{gnatcheck} run, the version of
17206 the tool that has generated this report and the full parameters
17207 of the @command{gnatcheck} invocation;
17208 @item list of enabled rules;
17209 @item total number of detected violations;
17210 @item list of source files where rule violations have been detected;
17211 @item list of source files where no violations have been detected.
17214 @node General gnatcheck Switches
17215 @section General @command{gnatcheck} Switches
17218 The following switches control the general @command{gnatcheck} behavior
17222 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
17224 Process all units including those with read-only ALI files such as
17225 those from the GNAT Run-Time library.
17229 @cindex @option{-d} (@command{gnatcheck})
17234 @cindex @option{-dd} (@command{gnatcheck})
17236 Progress indicator mode (for use in GPS).
17239 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
17241 List the predefined and user-defined rules. For more details see
17242 @ref{Predefined Rules}.
17244 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
17246 Use full source locations references in the report file. For a construct from
17247 a generic instantiation a full source location is a chain from the location
17248 of this construct in the generic unit to the place where this unit is
17251 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
17253 Duplicate all the output sent to @file{stderr} into a log file. The log file
17254 is named @file{gnatcheck.log} and is located in the current directory.
17256 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
17257 @item ^-m@i{nnnn}^/DIAGNOSTIC_LIMIT=@i{nnnn}^
17258 Maximum number of diagnostics to be sent to @file{stdout}, where @i{nnnn} is in
17259 the range 0@dots{}1000;
17260 the default value is 500. Zero means that there is no limitation on
17261 the number of diagnostic messages to be output.
17263 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
17265 Quiet mode. All the diagnostics about rule violations are placed in the
17266 @command{gnatcheck} report file only, without duplication on @file{stdout}.
17268 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
17270 Short format of the report file (no version information, no list of applied
17271 rules, no list of checked sources is included)
17273 @cindex @option{^--include-file=@var{file}^/INCLUDE_FILE=@var{file}^} (@command{gnatcheck})
17274 @item ^--include-file^/INCLUDE_FILE^
17275 Append the content of the specified text file to the report file
17277 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
17279 Print out execution time.
17281 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
17282 @item ^-v^/VERBOSE^
17283 Verbose mode; @command{gnatcheck} generates version information and then
17284 a trace of sources being processed.
17286 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
17287 @item ^-o ^/OUTPUT=^@var{report_file}
17288 Set name of report file file to @var{report_file} .
17292 @node gnatcheck Rule Options
17293 @section @command{gnatcheck} Rule Options
17296 The following options control the processing performed by
17297 @command{gnatcheck}.
17300 @cindex @option{+ALL} (@command{gnatcheck})
17302 Turn all the rule checks ON.
17304 @cindex @option{-ALL} (@command{gnatcheck})
17306 Turn all the rule checks OFF.
17308 @cindex @option{+R} (@command{gnatcheck})
17309 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
17310 Turn on the check for a specified rule with the specified parameter, if any.
17311 @var{rule_id} must be the identifier of one of the currently implemented rules
17312 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
17313 are not case-sensitive. The @var{param} item must
17314 be a string representing a valid parameter(s) for the specified rule.
17315 If it contains any space characters then this string must be enclosed in
17318 @cindex @option{-R} (@command{gnatcheck})
17319 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
17320 Turn off the check for a specified rule with the specified parameter, if any.
17322 @cindex @option{-from} (@command{gnatcheck})
17323 @item -from=@var{rule_option_filename}
17324 Read the rule options from the text file @var{rule_option_filename}, referred
17325 to as a ``coding standard file'' below.
17330 The default behavior is that all the rule checks are disabled.
17332 A coding standard file is a text file that contains a set of rule options
17334 @cindex Coding standard file (for @code{gnatcheck})
17335 The file may contain empty lines and Ada-style comments (comment
17336 lines and end-of-line comments). There can be several rule options on a
17337 single line (separated by a space).
17339 A coding standard file may reference other coding standard files by including
17340 more @option{-from=@var{rule_option_filename}}
17341 options, each such option being replaced with the content of the
17342 corresponding coding standard file during processing. In case a
17343 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
17344 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
17345 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
17346 processing fails with an error message.
17349 @node Adding the Results of Compiler Checks to gnatcheck Output
17350 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
17353 The @command{gnatcheck} tool can include in the generated diagnostic messages
17355 the report file the results of the checks performed by the compiler. Though
17356 disabled by default, this effect may be obtained by using @option{+R} with
17357 the following rule identifiers and parameters:
17361 To record restrictions violations (which are performed by the compiler if the
17362 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
17363 use the @code{Restrictions} rule
17364 with the same parameters as pragma
17365 @code{Restrictions} or @code{Restriction_Warnings}.
17368 To record compiler style checks (@pxref{Style Checking}), use the
17369 @code{Style_Checks} rule.
17370 This rule takes a parameter in one of the following forms:
17374 which enables the standard style checks corresponding to the @option{-gnatyy}
17375 GNAT style check option, or
17378 a string with the same
17379 structure and semantics as the @code{string_LITERAL} parameter of the
17380 GNAT pragma @code{Style_Checks}
17381 (for further information about this pragma,
17382 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
17387 @code{+RStyle_Checks:O} rule option activates
17388 the compiler style check that corresponds to
17389 @code{-gnatyO} style check option.
17392 To record compiler warnings (@pxref{Warning Message Control}), use the
17393 @code{Warnings} rule with a parameter that is a valid
17394 @i{static_string_expression} argument of the GNAT pragma @code{Warnings}
17395 (for further information about this pragma,
17396 @pxref{Pragma Warnings,,,gnat_rm, GNAT Reference Manual}).
17397 Note that in case of gnatcheck
17398 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
17399 all the specific warnings, but not suppresses the warning mode,
17400 and 'e' parameter, corresponding to @option{-gnatwe} that means
17401 "treat warnings as errors", does not have any effect.
17405 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
17406 option with the corresponding restriction name as a parameter. @code{-R} is
17407 not available for @code{Style_Checks} and @code{Warnings} options, to disable
17408 warnings and style checks, use the corresponding warning and style options.
17410 @node Project-Wide Checks
17411 @section Project-Wide Checks
17412 @cindex Project-wide checks (for @command{gnatcheck})
17415 In order to perform checks on all units of a given project, you can use
17416 the GNAT driver along with the @option{-P} option:
17418 gnat check -Pproj -rules -from=my_rules
17422 If the project @code{proj} depends upon other projects, you can perform
17423 checks on the project closure using the @option{-U} option:
17425 gnat check -Pproj -U -rules -from=my_rules
17429 Finally, if not all the units are relevant to a particular main
17430 program in the project closure, you can perform checks for the set
17431 of units needed to create a given main program (unit closure) using
17432 the @option{-U} option followed by the name of the main unit:
17434 gnat check -Pproj -U main -rules -from=my_rules
17438 @node Rule exemption
17439 @section Rule exemption
17440 @cindex Rule exemption (for @command{gnatcheck})
17443 One of the most useful applications of @command{gnatcheck} is to
17444 automate the enforcement of project-specific coding standards,
17445 for example in safety-critical systems where particular features
17446 must be restricted in order to simplify the certification effort.
17447 However, it may sometimes be appropriate to violate a coding standard rule,
17448 and in such cases the rationale for the violation should be provided
17449 in the source program itself so that the individuals
17450 reviewing or maintaining the program can immediately understand the intent.
17452 The @command{gnatcheck} tool supports this practice with the notion of
17453 a ``rule exemption'' covering a specific source code section. Normally
17454 rule violation messages are issued both on @file{stderr}
17455 and in a report file. In contrast, exempted violations are not listed on
17456 @file{stderr}; thus users invoking @command{gnatcheck} interactively
17457 (e.g. in its GPS interface) do not need to pay attention to known and
17458 justified violations. However, exempted violations along with their
17459 justification are documented in a special section of the report file that
17460 @command{gnatcheck} generates.
17463 * Using pragma Annotate to Control Rule Exemption::
17464 * gnatcheck Annotations Rules::
17467 @node Using pragma Annotate to Control Rule Exemption
17468 @subsection Using pragma @code{Annotate} to Control Rule Exemption
17469 @cindex Using pragma Annotate to control rule exemption
17472 Rule exemption is controlled by pragma @code{Annotate} when its first
17473 argument is ``gnatcheck''. The syntax of @command{gnatcheck}'s
17474 exemption control annotations is as follows:
17476 @smallexample @c ada
17478 pragma Annotate (gnatcheck, @i{exemption_control}, @i{Rule_Name}, [@i{justification}]);
17480 @i{exemption_control} ::= Exempt_On | Exempt_Off
17482 @i{Rule_Name} ::= string_literal
17484 @i{justification} ::= string_literal
17489 When a @command{gnatcheck} annotation has more then four arguments,
17490 @command{gnatcheck} issues a warning and ignores the additional arguments.
17491 If the additional arguments do not follow the syntax above,
17492 @command{gnatcheck} emits a warning and ignores the annotation.
17494 The @i{@code{Rule_Name}} argument should be the name of some existing
17495 @command{gnatcheck} rule.
17496 Otherwise a warning message is generated and the pragma is
17497 ignored. If @code{Rule_Name} denotes a rule that is not activated by the given
17498 @command{gnatcheck} call, the pragma is ignored and no warning is issued.
17500 A source code section where an exemption is active for a given rule is
17501 delimited by an @code{exempt_on} and @code{exempt_off} annotation pair:
17503 @smallexample @c ada
17504 pragma Annotate (gnatcheck, Exempt_On, Rule_Name, "justification");
17505 -- source code section
17506 pragma Annotate (gnatcheck, Exempt_Off, Rule_Name);
17510 @node gnatcheck Annotations Rules
17511 @subsection @command{gnatcheck} Annotations Rules
17512 @cindex @command{gnatcheck} annotations rules
17517 An ``Exempt_Off'' annotation can only appear after a corresponding
17518 ``Exempt_On'' annotation.
17521 Exempted source code sections are only based on the source location of the
17522 annotations. Any source construct between the two
17523 annotations is part of the exempted source code section.
17526 Exempted source code sections for different rules are independent. They can
17527 be nested or intersect with one another without limitation.
17528 Creating nested or intersecting source code sections for the same rule is
17532 Malformed exempted source code sections are reported by a warning, and
17533 the corresponding rule exemptions are ignored.
17536 When an exempted source code section does not contain at least one violation
17537 of the exempted rule, a warning is emitted on @file{stderr}.
17540 If an ``Exempt_On'' annotation pragma does not have a matching
17541 ``Exempt_Off'' annotation pragma in the same compilation unit, then the
17542 exemption for the given rule is ignored and a warning is issued.
17546 @node Predefined Rules
17547 @section Predefined Rules
17548 @cindex Predefined rules (for @command{gnatcheck})
17551 @c (Jan 2007) Since the global rules are still under development and are not
17552 @c documented, there is no point in explaining the difference between
17553 @c global and local rules
17555 A rule in @command{gnatcheck} is either local or global.
17556 A @emph{local rule} is a rule that applies to a well-defined section
17557 of a program and that can be checked by analyzing only this section.
17558 A @emph{global rule} requires analysis of some global properties of the
17559 whole program (mostly related to the program call graph).
17560 As of @value{NOW}, the implementation of global rules should be
17561 considered to be at a preliminary stage. You can use the
17562 @option{+GLOBAL} option to enable all the global rules, and the
17563 @option{-GLOBAL} rule option to disable all the global rules.
17565 All the global rules in the list below are
17566 so indicated by marking them ``GLOBAL''.
17567 This +GLOBAL and -GLOBAL options are not
17568 included in the list of gnatcheck options above, because at the moment they
17569 are considered as a temporary debug options.
17571 @command{gnatcheck} performs rule checks for generic
17572 instances only for global rules. This limitation may be relaxed in a later
17577 The predefined rules implemented in @command{gnatcheck}
17578 are described in a companion document,
17579 @cite{GNATcheck Reference Manual -- Predefined Rules}.
17580 The rule identifier is
17581 used as a parameter of @command{gnatcheck}'s @option{+R} or @option{-R}
17585 @node Example of gnatcheck Usage
17586 @section Example of @command{gnatcheck} Usage
17589 Here is a simple example. Suppose that in the current directory we have a
17590 project file named @file{gnatcheck_example.gpr} with the following content:
17592 @smallexample @c projectfile
17593 project Gnatcheck_Example is
17595 for Source_Dirs use ("src");
17596 for Object_Dir use "obj";
17597 for Main use ("main.adb");
17600 for Default_Switches ("ada") use ("-rules", "-from=coding_standard");
17603 end Gnatcheck_Example;
17607 And the file named @file{coding_standard} is also located in the current
17608 directory and has the following content:
17611 -----------------------------------------------------
17612 -- This is a sample gnatcheck coding standard file --
17613 -----------------------------------------------------
17615 -- First, turning on rules, that are directly implemented in gnatcheck
17616 +RAbstract_Type_Declarations
17619 +RFloat_Equality_Checks
17620 +REXIT_Statements_With_No_Loop_Name
17622 -- Then, activating compiler checks of interest:
17624 -- This style check checks if a unit name is present on END keyword that
17625 -- is the end of the unit declaration
17629 And the subdirectory @file{src} contains the following Ada sources:
17633 @smallexample @c ada
17635 type T is abstract tagged private;
17636 procedure P (X : T) is abstract;
17639 type My_Float is digits 8;
17640 function Is_Equal (L, R : My_Float) return Boolean;
17643 type T is abstract tagged null record;
17650 @smallexample @c ada
17651 package body Pack is
17652 package body Inner is
17653 function Is_Equal (L, R : My_Float) return Boolean is
17662 and @file{main.adb}
17664 @smallexample @c ada
17665 with Pack; use Pack;
17669 (gnatcheck, Exempt_On, "Anonymous_Arrays", "this one is fine");
17670 Float_Array : array (1 .. 10) of Inner.My_Float;
17671 pragma Annotate (gnatcheck, Exempt_Off, "Anonymous_Arrays");
17673 Another_Float_Array : array (1 .. 10) of Inner.My_Float;
17677 B : Boolean := False;
17680 for J in Float_Array'Range loop
17681 if Is_Equal (Float_Array (J), Another_Float_Array (J)) then
17690 And suppose we call @command{gnatcheck} from the current directory using
17691 the @command{gnat} driver:
17694 gnat check -Pgnatcheck_example.gpr
17698 As a result, @command{gnatcheck} is called to check all the files from the
17699 project @file{gnatcheck_example.gpr} using the coding standard defined by
17700 the file @file{coding_standard}. As the result, the @command{gnatcheck}
17701 report file named @file{gnatcheck.out} will be created in the current
17702 directory, and it will have the following content:
17705 RULE CHECKING REPORT
17709 Date and time of execution: 2009.10.28 14:17
17710 Tool version: GNATCHECK (built with ASIS 2.0.R for GNAT Pro 6.3.0w (20091016))
17713 gnatcheck -files=.../GNAT-TEMP-000004.TMP -cargs -gnatec=.../GNAT-TEMP-000003.TMP -rules -from=coding_standard
17715 Coding standard (applied rules):
17716 Abstract_Type_Declarations
17718 EXIT_Statements_With_No_Loop_Name
17719 Float_Equality_Checks
17722 Compiler style checks: -gnatye
17724 Number of coding standard violations: 6
17725 Number of exempted coding standard violations: 1
17727 2. DETECTED RULE VIOLATIONS
17729 2.1. NON-EXEMPTED VIOLATIONS
17731 Source files with non-exempted violations
17736 List of violations grouped by files, and ordered by increasing source location:
17738 pack.ads:2:4: declaration of abstract type
17739 pack.ads:5:4: declaration of local package
17740 pack.ads:10:30: declaration of abstract type
17741 pack.ads:11:1: (style) "end Pack" required
17742 pack.adb:5:19: use of equality operation for float values
17743 pack.adb:6:7: (style) "end Is_Equal" required
17744 main.adb:9:26: anonymous array type
17745 main.adb:19:10: exit statement with no loop name
17747 2.2. EXEMPTED VIOLATIONS
17749 Source files with exempted violations
17752 List of violations grouped by files, and ordered by increasing source location:
17754 main.adb:6:18: anonymous array type
17757 2.3. SOURCE FILES WITH NO VIOLATION
17759 No files without violations
17765 @c *********************************
17766 @node Creating Sample Bodies Using gnatstub
17767 @chapter Creating Sample Bodies Using @command{gnatstub}
17771 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
17772 for library unit declarations.
17774 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
17775 driver (see @ref{The GNAT Driver and Project Files}).
17777 To create a body stub, @command{gnatstub} has to compile the library
17778 unit declaration. Therefore, bodies can be created only for legal
17779 library units. Moreover, if a library unit depends semantically upon
17780 units located outside the current directory, you have to provide
17781 the source search path when calling @command{gnatstub}, see the description
17782 of @command{gnatstub} switches below.
17784 By default, all the program unit body stubs generated by @code{gnatstub}
17785 raise the predefined @code{Program_Error} exception, which will catch
17786 accidental calls of generated stubs. This behavior can be changed with
17787 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
17790 * Running gnatstub::
17791 * Switches for gnatstub::
17794 @node Running gnatstub
17795 @section Running @command{gnatstub}
17798 @command{gnatstub} has the command-line interface of the form
17801 @c $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
17802 @c Expanding @ovar macro inline (explanation in macro def comments)
17803 $ gnatstub @r{[}@var{switches}@r{]} @var{filename} @r{[}@var{directory}@r{]} @r{[}-cargs @var{gcc_switches}@r{]}
17810 is the name of the source file that contains a library unit declaration
17811 for which a body must be created. The file name may contain the path
17813 The file name does not have to follow the GNAT file name conventions. If the
17815 does not follow GNAT file naming conventions, the name of the body file must
17817 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
17818 If the file name follows the GNAT file naming
17819 conventions and the name of the body file is not provided,
17822 of the body file from the argument file name by replacing the @file{.ads}
17824 with the @file{.adb} suffix.
17827 indicates the directory in which the body stub is to be placed (the default
17831 @item @samp{@var{gcc_switches}} is a list of switches for
17832 @command{gcc}. They will be passed on to all compiler invocations made by
17833 @command{gnatelim} to generate the ASIS trees. Here you can provide
17834 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17835 use the @option{-gnatec} switch to set the configuration file etc.
17838 is an optional sequence of switches as described in the next section
17841 @node Switches for gnatstub
17842 @section Switches for @command{gnatstub}
17848 @cindex @option{^-f^/FULL^} (@command{gnatstub})
17849 If the destination directory already contains a file with the name of the
17851 for the argument spec file, replace it with the generated body stub.
17853 @item ^-hs^/HEADER=SPEC^
17854 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
17855 Put the comment header (i.e., all the comments preceding the
17856 compilation unit) from the source of the library unit declaration
17857 into the body stub.
17859 @item ^-hg^/HEADER=GENERAL^
17860 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
17861 Put a sample comment header into the body stub.
17863 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
17864 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
17865 Use the content of the file as the comment header for a generated body stub.
17869 @cindex @option{-IDIR} (@command{gnatstub})
17871 @cindex @option{-I-} (@command{gnatstub})
17874 @item /NOCURRENT_DIRECTORY
17875 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
17877 ^These switches have ^This switch has^ the same meaning as in calls to
17879 ^They define ^It defines ^ the source search path in the call to
17880 @command{gcc} issued
17881 by @command{gnatstub} to compile an argument source file.
17883 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
17884 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
17885 This switch has the same meaning as in calls to @command{gcc}.
17886 It defines the additional configuration file to be passed to the call to
17887 @command{gcc} issued
17888 by @command{gnatstub} to compile an argument source file.
17890 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
17891 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
17892 (@var{n} is a non-negative integer). Set the maximum line length in the
17893 body stub to @var{n}; the default is 79. The maximum value that can be
17894 specified is 32767. Note that in the special case of configuration
17895 pragma files, the maximum is always 32767 regardless of whether or
17896 not this switch appears.
17898 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
17899 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
17900 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
17901 the generated body sample to @var{n}.
17902 The default indentation is 3.
17904 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
17905 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
17906 Order local bodies alphabetically. (By default local bodies are ordered
17907 in the same way as the corresponding local specs in the argument spec file.)
17909 @item ^-i^/INDENTATION=^@var{n}
17910 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
17911 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
17913 @item ^-k^/TREE_FILE=SAVE^
17914 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
17915 Do not remove the tree file (i.e., the snapshot of the compiler internal
17916 structures used by @command{gnatstub}) after creating the body stub.
17918 @item ^-l^/LINE_LENGTH=^@var{n}
17919 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
17920 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
17922 @item ^--no-exception^/NO_EXCEPTION^
17923 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
17924 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
17925 This is not always possible for function stubs.
17927 @item ^--no-local-header^/NO_LOCAL_HEADER^
17928 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
17929 Do not place local comment header with unit name before body stub for a
17932 @item ^-o ^/BODY=^@var{body-name}
17933 @cindex @option{^-o^/BODY^} (@command{gnatstub})
17934 Body file name. This should be set if the argument file name does not
17936 the GNAT file naming
17937 conventions. If this switch is omitted the default name for the body will be
17939 from the argument file name according to the GNAT file naming conventions.
17942 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
17943 Quiet mode: do not generate a confirmation when a body is
17944 successfully created, and do not generate a message when a body is not
17948 @item ^-r^/TREE_FILE=REUSE^
17949 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
17950 Reuse the tree file (if it exists) instead of creating it. Instead of
17951 creating the tree file for the library unit declaration, @command{gnatstub}
17952 tries to find it in the current directory and use it for creating
17953 a body. If the tree file is not found, no body is created. This option
17954 also implies @option{^-k^/SAVE^}, whether or not
17955 the latter is set explicitly.
17957 @item ^-t^/TREE_FILE=OVERWRITE^
17958 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
17959 Overwrite the existing tree file. If the current directory already
17960 contains the file which, according to the GNAT file naming rules should
17961 be considered as a tree file for the argument source file,
17963 will refuse to create the tree file needed to create a sample body
17964 unless this option is set.
17966 @item ^-v^/VERBOSE^
17967 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
17968 Verbose mode: generate version information.
17972 @c *********************************
17973 @node Generating Ada Bindings for C and C++ headers
17974 @chapter Generating Ada Bindings for C and C++ headers
17978 GNAT now comes with a binding generator for C and C++ headers which is
17979 intended to do 95% of the tedious work of generating Ada specs from C
17980 or C++ header files.
17982 Note that this capability is not intended to generate 100% correct Ada specs,
17983 and will is some cases require manual adjustments, although it can often
17984 be used out of the box in practice.
17986 Some of the known limitations include:
17989 @item only very simple character constant macros are translated into Ada
17990 constants. Function macros (macros with arguments) are partially translated
17991 as comments, to be completed manually if needed.
17992 @item some extensions (e.g. vector types) are not supported
17993 @item pointers to pointers or complex structures are mapped to System.Address
17996 The code generated is using the Ada 2005 syntax, which makes it
17997 easier to interface with other languages than previous versions of Ada.
18000 * Running the binding generator::
18001 * Generating bindings for C++ headers::
18005 @node Running the binding generator
18006 @section Running the binding generator
18009 The binding generator is part of the @command{gcc} compiler and can be
18010 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
18011 spec files for the header files specified on the command line, and all
18012 header files needed by these files transitivitely. For example:
18015 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
18016 $ gcc -c -gnat05 *.ads
18019 will generate, under GNU/Linux, the following files: @file{time_h.ads},
18020 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
18021 correspond to the files @file{/usr/include/time.h},
18022 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
18023 mode these Ada specs.
18025 The @code{-C} switch tells @command{gcc} to extract comments from headers,
18026 and will attempt to generate corresponding Ada comments.
18028 If you want to generate a single Ada file and not the transitive closure, you
18029 can use instead the @option{-fdump-ada-spec-slim} switch.
18031 Note that we recommend when possible to use the @command{g++} driver to
18032 generate bindings, even for most C headers, since this will in general
18033 generate better Ada specs. For generating bindings for C++ headers, it is
18034 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
18035 is equivalent in this case. If @command{g++} cannot work on your C headers
18036 because of incompatibilities between C and C++, then you can fallback to
18037 @command{gcc} instead.
18039 For an example of better bindings generated from the C++ front-end,
18040 the name of the parameters (when available) are actually ignored by the C
18041 front-end. Consider the following C header:
18044 extern void foo (int variable);
18047 with the C front-end, @code{variable} is ignored, and the above is handled as:
18050 extern void foo (int);
18053 generating a generic:
18056 procedure foo (param1 : int);
18059 with the C++ front-end, the name is available, and we generate:
18062 procedure foo (variable : int);
18065 In some cases, the generated bindings will be more complete or more meaningful
18066 when defining some macros, which you can do via the @option{-D} switch. This
18067 is for example the case with @file{Xlib.h} under GNU/Linux:
18070 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
18073 The above will generate more complete bindings than a straight call without
18074 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
18076 In other cases, it is not possible to parse a header file in a stand alone
18077 manner, because other include files need to be included first. In this
18078 case, the solution is to create a small header file including the needed
18079 @code{#include} and possible @code{#define} directives. For example, to
18080 generate Ada bindings for @file{readline/readline.h}, you need to first
18081 include @file{stdio.h}, so you can create a file with the following two
18082 lines in e.g. @file{readline1.h}:
18086 #include <readline/readline.h>
18089 and then generate Ada bindings from this file:
18092 $ g++ -c -fdump-ada-spec readline1.h
18095 @node Generating bindings for C++ headers
18096 @section Generating bindings for C++ headers
18099 Generating bindings for C++ headers is done using the same options, always
18100 with the @command{g++} compiler.
18102 In this mode, C++ classes will be mapped to Ada tagged types, constructors
18103 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
18104 multiple inheritance of abstract classes will be mapped to Ada interfaces
18105 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
18106 information on interfacing to C++).
18108 For example, given the following C++ header file:
18115 virtual int Number_Of_Teeth () = 0;
18120 virtual void Set_Owner (char* Name) = 0;
18126 virtual void Set_Age (int New_Age);
18129 class Dog : Animal, Carnivore, Domestic @{
18134 virtual int Number_Of_Teeth ();
18135 virtual void Set_Owner (char* Name);
18143 The corresponding Ada code is generated:
18145 @smallexample @c ada
18148 package Class_Carnivore is
18149 type Carnivore is limited interface;
18150 pragma Import (CPP, Carnivore);
18152 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
18154 use Class_Carnivore;
18156 package Class_Domestic is
18157 type Domestic is limited interface;
18158 pragma Import (CPP, Domestic);
18160 procedure Set_Owner
18161 (this : access Domestic;
18162 Name : Interfaces.C.Strings.chars_ptr) is abstract;
18164 use Class_Domestic;
18166 package Class_Animal is
18167 type Animal is tagged limited record
18168 Age_Count : aliased int;
18170 pragma Import (CPP, Animal);
18172 procedure Set_Age (this : access Animal; New_Age : int);
18173 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
18177 package Class_Dog is
18178 type Dog is new Animal and Carnivore and Domestic with record
18179 Tooth_Count : aliased int;
18180 Owner : Interfaces.C.Strings.chars_ptr;
18182 pragma Import (CPP, Dog);
18184 function Number_Of_Teeth (this : access Dog) return int;
18185 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
18187 procedure Set_Owner
18188 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
18189 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
18191 function New_Dog return Dog;
18192 pragma CPP_Constructor (New_Dog);
18193 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
18204 @item -fdump-ada-spec
18205 @cindex @option{-fdump-ada-spec} (@command{gcc})
18206 Generate Ada spec files for the given header files transitively (including
18207 all header files that these headers depend upon).
18209 @item -fdump-ada-spec-slim
18210 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
18211 Generate Ada spec files for the header files specified on the command line
18215 @cindex @option{-C} (@command{gcc})
18216 Extract comments from headers and generate Ada comments in the Ada spec files.
18219 @node Other Utility Programs
18220 @chapter Other Utility Programs
18223 This chapter discusses some other utility programs available in the Ada
18227 * Using Other Utility Programs with GNAT::
18228 * The External Symbol Naming Scheme of GNAT::
18229 * Converting Ada Files to html with gnathtml::
18230 * Installing gnathtml::
18237 @node Using Other Utility Programs with GNAT
18238 @section Using Other Utility Programs with GNAT
18241 The object files generated by GNAT are in standard system format and in
18242 particular the debugging information uses this format. This means
18243 programs generated by GNAT can be used with existing utilities that
18244 depend on these formats.
18247 In general, any utility program that works with C will also often work with
18248 Ada programs generated by GNAT. This includes software utilities such as
18249 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
18253 @node The External Symbol Naming Scheme of GNAT
18254 @section The External Symbol Naming Scheme of GNAT
18257 In order to interpret the output from GNAT, when using tools that are
18258 originally intended for use with other languages, it is useful to
18259 understand the conventions used to generate link names from the Ada
18262 All link names are in all lowercase letters. With the exception of library
18263 procedure names, the mechanism used is simply to use the full expanded
18264 Ada name with dots replaced by double underscores. For example, suppose
18265 we have the following package spec:
18267 @smallexample @c ada
18278 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
18279 the corresponding link name is @code{qrs__mn}.
18281 Of course if a @code{pragma Export} is used this may be overridden:
18283 @smallexample @c ada
18288 pragma Export (Var1, C, External_Name => "var1_name");
18290 pragma Export (Var2, C, Link_Name => "var2_link_name");
18297 In this case, the link name for @var{Var1} is whatever link name the
18298 C compiler would assign for the C function @var{var1_name}. This typically
18299 would be either @var{var1_name} or @var{_var1_name}, depending on operating
18300 system conventions, but other possibilities exist. The link name for
18301 @var{Var2} is @var{var2_link_name}, and this is not operating system
18305 One exception occurs for library level procedures. A potential ambiguity
18306 arises between the required name @code{_main} for the C main program,
18307 and the name we would otherwise assign to an Ada library level procedure
18308 called @code{Main} (which might well not be the main program).
18310 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
18311 names. So if we have a library level procedure such as
18313 @smallexample @c ada
18316 procedure Hello (S : String);
18322 the external name of this procedure will be @var{_ada_hello}.
18325 @node Converting Ada Files to html with gnathtml
18326 @section Converting Ada Files to HTML with @code{gnathtml}
18329 This @code{Perl} script allows Ada source files to be browsed using
18330 standard Web browsers. For installation procedure, see the section
18331 @xref{Installing gnathtml}.
18333 Ada reserved keywords are highlighted in a bold font and Ada comments in
18334 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
18335 switch to suppress the generation of cross-referencing information, user
18336 defined variables and types will appear in a different color; you will
18337 be able to click on any identifier and go to its declaration.
18339 The command line is as follow:
18341 @c $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
18342 @c Expanding @ovar macro inline (explanation in macro def comments)
18343 $ perl gnathtml.pl @r{[}@var{^switches^options^}@r{]} @var{ada-files}
18347 You can pass it as many Ada files as you want. @code{gnathtml} will generate
18348 an html file for every ada file, and a global file called @file{index.htm}.
18349 This file is an index of every identifier defined in the files.
18351 The available ^switches^options^ are the following ones:
18355 @cindex @option{-83} (@code{gnathtml})
18356 Only the Ada 83 subset of keywords will be highlighted.
18358 @item -cc @var{color}
18359 @cindex @option{-cc} (@code{gnathtml})
18360 This option allows you to change the color used for comments. The default
18361 value is green. The color argument can be any name accepted by html.
18364 @cindex @option{-d} (@code{gnathtml})
18365 If the Ada files depend on some other files (for instance through
18366 @code{with} clauses, the latter files will also be converted to html.
18367 Only the files in the user project will be converted to html, not the files
18368 in the run-time library itself.
18371 @cindex @option{-D} (@code{gnathtml})
18372 This command is the same as @option{-d} above, but @command{gnathtml} will
18373 also look for files in the run-time library, and generate html files for them.
18375 @item -ext @var{extension}
18376 @cindex @option{-ext} (@code{gnathtml})
18377 This option allows you to change the extension of the generated HTML files.
18378 If you do not specify an extension, it will default to @file{htm}.
18381 @cindex @option{-f} (@code{gnathtml})
18382 By default, gnathtml will generate html links only for global entities
18383 ('with'ed units, global variables and types,@dots{}). If you specify
18384 @option{-f} on the command line, then links will be generated for local
18387 @item -l @var{number}
18388 @cindex @option{-l} (@code{gnathtml})
18389 If this ^switch^option^ is provided and @var{number} is not 0, then
18390 @code{gnathtml} will number the html files every @var{number} line.
18393 @cindex @option{-I} (@code{gnathtml})
18394 Specify a directory to search for library files (@file{.ALI} files) and
18395 source files. You can provide several -I switches on the command line,
18396 and the directories will be parsed in the order of the command line.
18399 @cindex @option{-o} (@code{gnathtml})
18400 Specify the output directory for html files. By default, gnathtml will
18401 saved the generated html files in a subdirectory named @file{html/}.
18403 @item -p @var{file}
18404 @cindex @option{-p} (@code{gnathtml})
18405 If you are using Emacs and the most recent Emacs Ada mode, which provides
18406 a full Integrated Development Environment for compiling, checking,
18407 running and debugging applications, you may use @file{.gpr} files
18408 to give the directories where Emacs can find sources and object files.
18410 Using this ^switch^option^, you can tell gnathtml to use these files.
18411 This allows you to get an html version of your application, even if it
18412 is spread over multiple directories.
18414 @item -sc @var{color}
18415 @cindex @option{-sc} (@code{gnathtml})
18416 This ^switch^option^ allows you to change the color used for symbol
18418 The default value is red. The color argument can be any name accepted by html.
18420 @item -t @var{file}
18421 @cindex @option{-t} (@code{gnathtml})
18422 This ^switch^option^ provides the name of a file. This file contains a list of
18423 file names to be converted, and the effect is exactly as though they had
18424 appeared explicitly on the command line. This
18425 is the recommended way to work around the command line length limit on some
18430 @node Installing gnathtml
18431 @section Installing @code{gnathtml}
18434 @code{Perl} needs to be installed on your machine to run this script.
18435 @code{Perl} is freely available for almost every architecture and
18436 Operating System via the Internet.
18438 On Unix systems, you may want to modify the first line of the script
18439 @code{gnathtml}, to explicitly tell the Operating system where Perl
18440 is. The syntax of this line is:
18442 #!full_path_name_to_perl
18446 Alternatively, you may run the script using the following command line:
18449 @c $ perl gnathtml.pl @ovar{switches} @var{files}
18450 @c Expanding @ovar macro inline (explanation in macro def comments)
18451 $ perl gnathtml.pl @r{[}@var{switches}@r{]} @var{files}
18460 The GNAT distribution provides an Ada 95 template for the HP Language
18461 Sensitive Editor (LSE), a component of DECset. In order to
18462 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
18469 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
18470 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
18471 the collection phase with the /DEBUG qualifier.
18474 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
18475 $ DEFINE LIB$DEBUG PCA$COLLECTOR
18476 $ RUN/DEBUG <PROGRAM_NAME>
18482 @c ******************************
18483 @node Code Coverage and Profiling
18484 @chapter Code Coverage and Profiling
18485 @cindex Code Coverage
18489 This chapter describes how to use @code{gcov} - coverage testing tool - and
18490 @code{gprof} - profiler tool - on your Ada programs.
18493 * Code Coverage of Ada Programs using gcov::
18494 * Profiling an Ada Program using gprof::
18497 @node Code Coverage of Ada Programs using gcov
18498 @section Code Coverage of Ada Programs using gcov
18500 @cindex -fprofile-arcs
18501 @cindex -ftest-coverage
18503 @cindex Code Coverage
18506 @code{gcov} is a test coverage program: it analyzes the execution of a given
18507 program on selected tests, to help you determine the portions of the program
18508 that are still untested.
18510 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
18511 User's Guide. You can refer to this documentation for a more complete
18514 This chapter provides a quick startup guide, and
18515 details some Gnat-specific features.
18518 * Quick startup guide::
18522 @node Quick startup guide
18523 @subsection Quick startup guide
18525 In order to perform coverage analysis of a program using @code{gcov}, 3
18530 Code instrumentation during the compilation process
18532 Execution of the instrumented program
18534 Execution of the @code{gcov} tool to generate the result.
18537 The code instrumentation needed by gcov is created at the object level:
18538 The source code is not modified in any way, because the instrumentation code is
18539 inserted by gcc during the compilation process. To compile your code with code
18540 coverage activated, you need to recompile your whole project using the
18542 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
18543 @code{-fprofile-arcs}.
18546 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
18547 -largs -fprofile-arcs
18550 This compilation process will create @file{.gcno} files together with
18551 the usual object files.
18553 Once the program is compiled with coverage instrumentation, you can
18554 run it as many times as needed - on portions of a test suite for
18555 example. The first execution will produce @file{.gcda} files at the
18556 same location as the @file{.gcno} files. The following executions
18557 will update those files, so that a cumulative result of the covered
18558 portions of the program is generated.
18560 Finally, you need to call the @code{gcov} tool. The different options of
18561 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
18563 This will create annotated source files with a @file{.gcov} extension:
18564 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
18566 @node Gnat specifics
18567 @subsection Gnat specifics
18569 Because Ada semantics, portions of the source code may be shared among
18570 several object files. This is the case for example when generics are
18571 involved, when inlining is active or when declarations generate initialisation
18572 calls. In order to take
18573 into account this shared code, you need to call @code{gcov} on all
18574 source files of the tested program at once.
18576 The list of source files might exceed the system's maximum command line
18577 length. In order to bypass this limitation, a new mechanism has been
18578 implemented in @code{gcov}: you can now list all your project's files into a
18579 text file, and provide this file to gcov as a parameter, preceded by a @@
18580 (e.g. @samp{gcov @@mysrclist.txt}).
18582 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
18583 not supported as there can be unresolved symbols during the final link.
18585 @node Profiling an Ada Program using gprof
18586 @section Profiling an Ada Program using gprof
18592 This section is not meant to be an exhaustive documentation of @code{gprof}.
18593 Full documentation for it can be found in the GNU Profiler User's Guide
18594 documentation that is part of this GNAT distribution.
18596 Profiling a program helps determine the parts of a program that are executed
18597 most often, and are therefore the most time-consuming.
18599 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
18600 better handle Ada programs and multitasking.
18601 It is currently supported on the following platforms
18606 solaris sparc/sparc64/x86
18612 In order to profile a program using @code{gprof}, 3 steps are needed:
18616 Code instrumentation, requiring a full recompilation of the project with the
18619 Execution of the program under the analysis conditions, i.e. with the desired
18622 Analysis of the results using the @code{gprof} tool.
18626 The following sections detail the different steps, and indicate how
18627 to interpret the results:
18629 * Compilation for profiling::
18630 * Program execution::
18632 * Interpretation of profiling results::
18635 @node Compilation for profiling
18636 @subsection Compilation for profiling
18640 In order to profile a program the first step is to tell the compiler
18641 to generate the necessary profiling information. The compiler switch to be used
18642 is @code{-pg}, which must be added to other compilation switches. This
18643 switch needs to be specified both during compilation and link stages, and can
18644 be specified once when using gnatmake:
18647 gnatmake -f -pg -P my_project
18651 Note that only the objects that were compiled with the @samp{-pg} switch will be
18652 profiled; if you need to profile your whole project, use the
18653 @samp{-f} gnatmake switch to force full recompilation.
18655 @node Program execution
18656 @subsection Program execution
18659 Once the program has been compiled for profiling, you can run it as usual.
18661 The only constraint imposed by profiling is that the program must terminate
18662 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
18665 Once the program completes execution, a data file called @file{gmon.out} is
18666 generated in the directory where the program was launched from. If this file
18667 already exists, it will be overwritten.
18669 @node Running gprof
18670 @subsection Running gprof
18673 The @code{gprof} tool is called as follow:
18676 gprof my_prog gmon.out
18687 The complete form of the gprof command line is the following:
18690 gprof [^switches^options^] [executable [data-file]]
18694 @code{gprof} supports numerous ^switch^options^. The order of these
18695 ^switch^options^ does not matter. The full list of options can be found in
18696 the GNU Profiler User's Guide documentation that comes with this documentation.
18698 The following is the subset of those switches that is most relevant:
18702 @item --demangle[=@var{style}]
18703 @itemx --no-demangle
18704 @cindex @option{--demangle} (@code{gprof})
18705 These options control whether symbol names should be demangled when
18706 printing output. The default is to demangle C++ symbols. The
18707 @code{--no-demangle} option may be used to turn off demangling. Different
18708 compilers have different mangling styles. The optional demangling style
18709 argument can be used to choose an appropriate demangling style for your
18710 compiler, in particular Ada symbols generated by GNAT can be demangled using
18711 @code{--demangle=gnat}.
18713 @item -e @var{function_name}
18714 @cindex @option{-e} (@code{gprof})
18715 The @samp{-e @var{function}} option tells @code{gprof} not to print
18716 information about the function @var{function_name} (and its
18717 children@dots{}) in the call graph. The function will still be listed
18718 as a child of any functions that call it, but its index number will be
18719 shown as @samp{[not printed]}. More than one @samp{-e} option may be
18720 given; only one @var{function_name} may be indicated with each @samp{-e}
18723 @item -E @var{function_name}
18724 @cindex @option{-E} (@code{gprof})
18725 The @code{-E @var{function}} option works like the @code{-e} option, but
18726 execution time spent in the function (and children who were not called from
18727 anywhere else), will not be used to compute the percentages-of-time for
18728 the call graph. More than one @samp{-E} option may be given; only one
18729 @var{function_name} may be indicated with each @samp{-E} option.
18731 @item -f @var{function_name}
18732 @cindex @option{-f} (@code{gprof})
18733 The @samp{-f @var{function}} option causes @code{gprof} to limit the
18734 call graph to the function @var{function_name} and its children (and
18735 their children@dots{}). More than one @samp{-f} option may be given;
18736 only one @var{function_name} may be indicated with each @samp{-f}
18739 @item -F @var{function_name}
18740 @cindex @option{-F} (@code{gprof})
18741 The @samp{-F @var{function}} option works like the @code{-f} option, but
18742 only time spent in the function and its children (and their
18743 children@dots{}) will be used to determine total-time and
18744 percentages-of-time for the call graph. More than one @samp{-F} option
18745 may be given; only one @var{function_name} may be indicated with each
18746 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
18750 @node Interpretation of profiling results
18751 @subsection Interpretation of profiling results
18755 The results of the profiling analysis are represented by two arrays: the
18756 'flat profile' and the 'call graph'. Full documentation of those outputs
18757 can be found in the GNU Profiler User's Guide.
18759 The flat profile shows the time spent in each function of the program, and how
18760 many time it has been called. This allows you to locate easily the most
18761 time-consuming functions.
18763 The call graph shows, for each subprogram, the subprograms that call it,
18764 and the subprograms that it calls. It also provides an estimate of the time
18765 spent in each of those callers/called subprograms.
18768 @c ******************************
18769 @node Running and Debugging Ada Programs
18770 @chapter Running and Debugging Ada Programs
18774 This chapter discusses how to debug Ada programs.
18776 It applies to GNAT on the Alpha OpenVMS platform;
18777 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
18778 since HP has implemented Ada support in the OpenVMS debugger on I64.
18781 An incorrect Ada program may be handled in three ways by the GNAT compiler:
18785 The illegality may be a violation of the static semantics of Ada. In
18786 that case GNAT diagnoses the constructs in the program that are illegal.
18787 It is then a straightforward matter for the user to modify those parts of
18791 The illegality may be a violation of the dynamic semantics of Ada. In
18792 that case the program compiles and executes, but may generate incorrect
18793 results, or may terminate abnormally with some exception.
18796 When presented with a program that contains convoluted errors, GNAT
18797 itself may terminate abnormally without providing full diagnostics on
18798 the incorrect user program.
18802 * The GNAT Debugger GDB::
18804 * Introduction to GDB Commands::
18805 * Using Ada Expressions::
18806 * Calling User-Defined Subprograms::
18807 * Using the Next Command in a Function::
18810 * Debugging Generic Units::
18811 * Remote Debugging using gdbserver::
18812 * GNAT Abnormal Termination or Failure to Terminate::
18813 * Naming Conventions for GNAT Source Files::
18814 * Getting Internal Debugging Information::
18815 * Stack Traceback::
18821 @node The GNAT Debugger GDB
18822 @section The GNAT Debugger GDB
18825 @code{GDB} is a general purpose, platform-independent debugger that
18826 can be used to debug mixed-language programs compiled with @command{gcc},
18827 and in particular is capable of debugging Ada programs compiled with
18828 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
18829 complex Ada data structures.
18831 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
18833 located in the GNU:[DOCS] directory,
18835 for full details on the usage of @code{GDB}, including a section on
18836 its usage on programs. This manual should be consulted for full
18837 details. The section that follows is a brief introduction to the
18838 philosophy and use of @code{GDB}.
18840 When GNAT programs are compiled, the compiler optionally writes debugging
18841 information into the generated object file, including information on
18842 line numbers, and on declared types and variables. This information is
18843 separate from the generated code. It makes the object files considerably
18844 larger, but it does not add to the size of the actual executable that
18845 will be loaded into memory, and has no impact on run-time performance. The
18846 generation of debug information is triggered by the use of the
18847 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
18848 used to carry out the compilations. It is important to emphasize that
18849 the use of these options does not change the generated code.
18851 The debugging information is written in standard system formats that
18852 are used by many tools, including debuggers and profilers. The format
18853 of the information is typically designed to describe C types and
18854 semantics, but GNAT implements a translation scheme which allows full
18855 details about Ada types and variables to be encoded into these
18856 standard C formats. Details of this encoding scheme may be found in
18857 the file exp_dbug.ads in the GNAT source distribution. However, the
18858 details of this encoding are, in general, of no interest to a user,
18859 since @code{GDB} automatically performs the necessary decoding.
18861 When a program is bound and linked, the debugging information is
18862 collected from the object files, and stored in the executable image of
18863 the program. Again, this process significantly increases the size of
18864 the generated executable file, but it does not increase the size of
18865 the executable program itself. Furthermore, if this program is run in
18866 the normal manner, it runs exactly as if the debug information were
18867 not present, and takes no more actual memory.
18869 However, if the program is run under control of @code{GDB}, the
18870 debugger is activated. The image of the program is loaded, at which
18871 point it is ready to run. If a run command is given, then the program
18872 will run exactly as it would have if @code{GDB} were not present. This
18873 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
18874 entirely non-intrusive until a breakpoint is encountered. If no
18875 breakpoint is ever hit, the program will run exactly as it would if no
18876 debugger were present. When a breakpoint is hit, @code{GDB} accesses
18877 the debugging information and can respond to user commands to inspect
18878 variables, and more generally to report on the state of execution.
18882 @section Running GDB
18885 This section describes how to initiate the debugger.
18886 @c The above sentence is really just filler, but it was otherwise
18887 @c clumsy to get the first paragraph nonindented given the conditional
18888 @c nature of the description
18891 The debugger can be launched from a @code{GPS} menu or
18892 directly from the command line. The description below covers the latter use.
18893 All the commands shown can be used in the @code{GPS} debug console window,
18894 but there are usually more GUI-based ways to achieve the same effect.
18897 The command to run @code{GDB} is
18900 $ ^gdb program^GDB PROGRAM^
18904 where @code{^program^PROGRAM^} is the name of the executable file. This
18905 activates the debugger and results in a prompt for debugger commands.
18906 The simplest command is simply @code{run}, which causes the program to run
18907 exactly as if the debugger were not present. The following section
18908 describes some of the additional commands that can be given to @code{GDB}.
18910 @c *******************************
18911 @node Introduction to GDB Commands
18912 @section Introduction to GDB Commands
18915 @code{GDB} contains a large repertoire of commands. @xref{Top,,
18916 Debugging with GDB, gdb, Debugging with GDB},
18918 located in the GNU:[DOCS] directory,
18920 for extensive documentation on the use
18921 of these commands, together with examples of their use. Furthermore,
18922 the command @command{help} invoked from within GDB activates a simple help
18923 facility which summarizes the available commands and their options.
18924 In this section we summarize a few of the most commonly
18925 used commands to give an idea of what @code{GDB} is about. You should create
18926 a simple program with debugging information and experiment with the use of
18927 these @code{GDB} commands on the program as you read through the
18931 @item set args @var{arguments}
18932 The @var{arguments} list above is a list of arguments to be passed to
18933 the program on a subsequent run command, just as though the arguments
18934 had been entered on a normal invocation of the program. The @code{set args}
18935 command is not needed if the program does not require arguments.
18938 The @code{run} command causes execution of the program to start from
18939 the beginning. If the program is already running, that is to say if
18940 you are currently positioned at a breakpoint, then a prompt will ask
18941 for confirmation that you want to abandon the current execution and
18944 @item breakpoint @var{location}
18945 The breakpoint command sets a breakpoint, that is to say a point at which
18946 execution will halt and @code{GDB} will await further
18947 commands. @var{location} is
18948 either a line number within a file, given in the format @code{file:linenumber},
18949 or it is the name of a subprogram. If you request that a breakpoint be set on
18950 a subprogram that is overloaded, a prompt will ask you to specify on which of
18951 those subprograms you want to breakpoint. You can also
18952 specify that all of them should be breakpointed. If the program is run
18953 and execution encounters the breakpoint, then the program
18954 stops and @code{GDB} signals that the breakpoint was encountered by
18955 printing the line of code before which the program is halted.
18957 @item catch exception @var{name}
18958 This command causes the program execution to stop whenever exception
18959 @var{name} is raised. If @var{name} is omitted, then the execution is
18960 suspended when any exception is raised.
18962 @item print @var{expression}
18963 This will print the value of the given expression. Most simple
18964 Ada expression formats are properly handled by @code{GDB}, so the expression
18965 can contain function calls, variables, operators, and attribute references.
18968 Continues execution following a breakpoint, until the next breakpoint or the
18969 termination of the program.
18972 Executes a single line after a breakpoint. If the next statement
18973 is a subprogram call, execution continues into (the first statement of)
18974 the called subprogram.
18977 Executes a single line. If this line is a subprogram call, executes and
18978 returns from the call.
18981 Lists a few lines around the current source location. In practice, it
18982 is usually more convenient to have a separate edit window open with the
18983 relevant source file displayed. Successive applications of this command
18984 print subsequent lines. The command can be given an argument which is a
18985 line number, in which case it displays a few lines around the specified one.
18988 Displays a backtrace of the call chain. This command is typically
18989 used after a breakpoint has occurred, to examine the sequence of calls that
18990 leads to the current breakpoint. The display includes one line for each
18991 activation record (frame) corresponding to an active subprogram.
18994 At a breakpoint, @code{GDB} can display the values of variables local
18995 to the current frame. The command @code{up} can be used to
18996 examine the contents of other active frames, by moving the focus up
18997 the stack, that is to say from callee to caller, one frame at a time.
19000 Moves the focus of @code{GDB} down from the frame currently being
19001 examined to the frame of its callee (the reverse of the previous command),
19003 @item frame @var{n}
19004 Inspect the frame with the given number. The value 0 denotes the frame
19005 of the current breakpoint, that is to say the top of the call stack.
19010 The above list is a very short introduction to the commands that
19011 @code{GDB} provides. Important additional capabilities, including conditional
19012 breakpoints, the ability to execute command sequences on a breakpoint,
19013 the ability to debug at the machine instruction level and many other
19014 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
19015 Debugging with GDB}. Note that most commands can be abbreviated
19016 (for example, c for continue, bt for backtrace).
19018 @node Using Ada Expressions
19019 @section Using Ada Expressions
19020 @cindex Ada expressions
19023 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
19024 extensions. The philosophy behind the design of this subset is
19028 That @code{GDB} should provide basic literals and access to operations for
19029 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
19030 leaving more sophisticated computations to subprograms written into the
19031 program (which therefore may be called from @code{GDB}).
19034 That type safety and strict adherence to Ada language restrictions
19035 are not particularly important to the @code{GDB} user.
19038 That brevity is important to the @code{GDB} user.
19042 Thus, for brevity, the debugger acts as if there were
19043 implicit @code{with} and @code{use} clauses in effect for all user-written
19044 packages, thus making it unnecessary to fully qualify most names with
19045 their packages, regardless of context. Where this causes ambiguity,
19046 @code{GDB} asks the user's intent.
19048 For details on the supported Ada syntax, see @ref{Top,, Debugging with
19049 GDB, gdb, Debugging with GDB}.
19051 @node Calling User-Defined Subprograms
19052 @section Calling User-Defined Subprograms
19055 An important capability of @code{GDB} is the ability to call user-defined
19056 subprograms while debugging. This is achieved simply by entering
19057 a subprogram call statement in the form:
19060 call subprogram-name (parameters)
19064 The keyword @code{call} can be omitted in the normal case where the
19065 @code{subprogram-name} does not coincide with any of the predefined
19066 @code{GDB} commands.
19068 The effect is to invoke the given subprogram, passing it the
19069 list of parameters that is supplied. The parameters can be expressions and
19070 can include variables from the program being debugged. The
19071 subprogram must be defined
19072 at the library level within your program, and @code{GDB} will call the
19073 subprogram within the environment of your program execution (which
19074 means that the subprogram is free to access or even modify variables
19075 within your program).
19077 The most important use of this facility is in allowing the inclusion of
19078 debugging routines that are tailored to particular data structures
19079 in your program. Such debugging routines can be written to provide a suitably
19080 high-level description of an abstract type, rather than a low-level dump
19081 of its physical layout. After all, the standard
19082 @code{GDB print} command only knows the physical layout of your
19083 types, not their abstract meaning. Debugging routines can provide information
19084 at the desired semantic level and are thus enormously useful.
19086 For example, when debugging GNAT itself, it is crucial to have access to
19087 the contents of the tree nodes used to represent the program internally.
19088 But tree nodes are represented simply by an integer value (which in turn
19089 is an index into a table of nodes).
19090 Using the @code{print} command on a tree node would simply print this integer
19091 value, which is not very useful. But the PN routine (defined in file
19092 treepr.adb in the GNAT sources) takes a tree node as input, and displays
19093 a useful high level representation of the tree node, which includes the
19094 syntactic category of the node, its position in the source, the integers
19095 that denote descendant nodes and parent node, as well as varied
19096 semantic information. To study this example in more detail, you might want to
19097 look at the body of the PN procedure in the stated file.
19099 @node Using the Next Command in a Function
19100 @section Using the Next Command in a Function
19103 When you use the @code{next} command in a function, the current source
19104 location will advance to the next statement as usual. A special case
19105 arises in the case of a @code{return} statement.
19107 Part of the code for a return statement is the ``epilog'' of the function.
19108 This is the code that returns to the caller. There is only one copy of
19109 this epilog code, and it is typically associated with the last return
19110 statement in the function if there is more than one return. In some
19111 implementations, this epilog is associated with the first statement
19114 The result is that if you use the @code{next} command from a return
19115 statement that is not the last return statement of the function you
19116 may see a strange apparent jump to the last return statement or to
19117 the start of the function. You should simply ignore this odd jump.
19118 The value returned is always that from the first return statement
19119 that was stepped through.
19121 @node Ada Exceptions
19122 @section Stopping when Ada Exceptions are Raised
19126 You can set catchpoints that stop the program execution when your program
19127 raises selected exceptions.
19130 @item catch exception
19131 Set a catchpoint that stops execution whenever (any task in the) program
19132 raises any exception.
19134 @item catch exception @var{name}
19135 Set a catchpoint that stops execution whenever (any task in the) program
19136 raises the exception @var{name}.
19138 @item catch exception unhandled
19139 Set a catchpoint that stops executino whenever (any task in the) program
19140 raises an exception for which there is no handler.
19142 @item info exceptions
19143 @itemx info exceptions @var{regexp}
19144 The @code{info exceptions} command permits the user to examine all defined
19145 exceptions within Ada programs. With a regular expression, @var{regexp}, as
19146 argument, prints out only those exceptions whose name matches @var{regexp}.
19154 @code{GDB} allows the following task-related commands:
19158 This command shows a list of current Ada tasks, as in the following example:
19165 ID TID P-ID Thread Pri State Name
19166 1 8088000 0 807e000 15 Child Activation Wait main_task
19167 2 80a4000 1 80ae000 15 Accept/Select Wait b
19168 3 809a800 1 80a4800 15 Child Activation Wait a
19169 * 4 80ae800 3 80b8000 15 Running c
19173 In this listing, the asterisk before the first task indicates it to be the
19174 currently running task. The first column lists the task ID that is used
19175 to refer to tasks in the following commands.
19177 @item break @var{linespec} task @var{taskid}
19178 @itemx break @var{linespec} task @var{taskid} if @dots{}
19179 @cindex Breakpoints and tasks
19180 These commands are like the @code{break @dots{} thread @dots{}}.
19181 @var{linespec} specifies source lines.
19183 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
19184 to specify that you only want @code{GDB} to stop the program when a
19185 particular Ada task reaches this breakpoint. @var{taskid} is one of the
19186 numeric task identifiers assigned by @code{GDB}, shown in the first
19187 column of the @samp{info tasks} display.
19189 If you do not specify @samp{task @var{taskid}} when you set a
19190 breakpoint, the breakpoint applies to @emph{all} tasks of your
19193 You can use the @code{task} qualifier on conditional breakpoints as
19194 well; in this case, place @samp{task @var{taskid}} before the
19195 breakpoint condition (before the @code{if}).
19197 @item task @var{taskno}
19198 @cindex Task switching
19200 This command allows to switch to the task referred by @var{taskno}. In
19201 particular, This allows to browse the backtrace of the specified
19202 task. It is advised to switch back to the original task before
19203 continuing execution otherwise the scheduling of the program may be
19208 For more detailed information on the tasking support,
19209 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
19211 @node Debugging Generic Units
19212 @section Debugging Generic Units
19213 @cindex Debugging Generic Units
19217 GNAT always uses code expansion for generic instantiation. This means that
19218 each time an instantiation occurs, a complete copy of the original code is
19219 made, with appropriate substitutions of formals by actuals.
19221 It is not possible to refer to the original generic entities in
19222 @code{GDB}, but it is always possible to debug a particular instance of
19223 a generic, by using the appropriate expanded names. For example, if we have
19225 @smallexample @c ada
19230 generic package k is
19231 procedure kp (v1 : in out integer);
19235 procedure kp (v1 : in out integer) is
19241 package k1 is new k;
19242 package k2 is new k;
19244 var : integer := 1;
19257 Then to break on a call to procedure kp in the k2 instance, simply
19261 (gdb) break g.k2.kp
19265 When the breakpoint occurs, you can step through the code of the
19266 instance in the normal manner and examine the values of local variables, as for
19269 @node Remote Debugging using gdbserver
19270 @section Remote Debugging using gdbserver
19271 @cindex Remote Debugging using gdbserver
19274 On platforms where gdbserver is supported, it is possible to use this tool
19275 to debug your application remotely. This can be useful in situations
19276 where the program needs to be run on a target host that is different
19277 from the host used for development, particularly when the target has
19278 a limited amount of resources (either CPU and/or memory).
19280 To do so, start your program using gdbserver on the target machine.
19281 gdbserver then automatically suspends the execution of your program
19282 at its entry point, waiting for a debugger to connect to it. The
19283 following commands starts an application and tells gdbserver to
19284 wait for a connection with the debugger on localhost port 4444.
19287 $ gdbserver localhost:4444 program
19288 Process program created; pid = 5685
19289 Listening on port 4444
19292 Once gdbserver has started listening, we can tell the debugger to establish
19293 a connection with this gdbserver, and then start the same debugging session
19294 as if the program was being debugged on the same host, directly under
19295 the control of GDB.
19299 (gdb) target remote targethost:4444
19300 Remote debugging using targethost:4444
19301 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
19303 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
19307 Breakpoint 1, foo () at foo.adb:4
19311 It is also possible to use gdbserver to attach to an already running
19312 program, in which case the execution of that program is simply suspended
19313 until the connection between the debugger and gdbserver is established.
19315 For more information on how to use gdbserver, @ref{Top, Server, Using
19316 the gdbserver Program, gdb, Debugging with GDB}. GNAT Pro provides support
19317 for gdbserver on x86-linux, x86-windows and x86_64-linux.
19319 @node GNAT Abnormal Termination or Failure to Terminate
19320 @section GNAT Abnormal Termination or Failure to Terminate
19321 @cindex GNAT Abnormal Termination or Failure to Terminate
19324 When presented with programs that contain serious errors in syntax
19326 GNAT may on rare occasions experience problems in operation, such
19328 segmentation fault or illegal memory access, raising an internal
19329 exception, terminating abnormally, or failing to terminate at all.
19330 In such cases, you can activate
19331 various features of GNAT that can help you pinpoint the construct in your
19332 program that is the likely source of the problem.
19334 The following strategies are presented in increasing order of
19335 difficulty, corresponding to your experience in using GNAT and your
19336 familiarity with compiler internals.
19340 Run @command{gcc} with the @option{-gnatf}. This first
19341 switch causes all errors on a given line to be reported. In its absence,
19342 only the first error on a line is displayed.
19344 The @option{-gnatdO} switch causes errors to be displayed as soon as they
19345 are encountered, rather than after compilation is terminated. If GNAT
19346 terminates prematurely or goes into an infinite loop, the last error
19347 message displayed may help to pinpoint the culprit.
19350 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
19351 mode, @command{gcc} produces ongoing information about the progress of the
19352 compilation and provides the name of each procedure as code is
19353 generated. This switch allows you to find which Ada procedure was being
19354 compiled when it encountered a code generation problem.
19357 @cindex @option{-gnatdc} switch
19358 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
19359 switch that does for the front-end what @option{^-v^VERBOSE^} does
19360 for the back end. The system prints the name of each unit,
19361 either a compilation unit or nested unit, as it is being analyzed.
19363 Finally, you can start
19364 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
19365 front-end of GNAT, and can be run independently (normally it is just
19366 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
19367 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
19368 @code{where} command is the first line of attack; the variable
19369 @code{lineno} (seen by @code{print lineno}), used by the second phase of
19370 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
19371 which the execution stopped, and @code{input_file name} indicates the name of
19375 @node Naming Conventions for GNAT Source Files
19376 @section Naming Conventions for GNAT Source Files
19379 In order to examine the workings of the GNAT system, the following
19380 brief description of its organization may be helpful:
19384 Files with prefix @file{^sc^SC^} contain the lexical scanner.
19387 All files prefixed with @file{^par^PAR^} are components of the parser. The
19388 numbers correspond to chapters of the Ada Reference Manual. For example,
19389 parsing of select statements can be found in @file{par-ch9.adb}.
19392 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
19393 numbers correspond to chapters of the Ada standard. For example, all
19394 issues involving context clauses can be found in @file{sem_ch10.adb}. In
19395 addition, some features of the language require sufficient special processing
19396 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
19397 dynamic dispatching, etc.
19400 All files prefixed with @file{^exp^EXP^} perform normalization and
19401 expansion of the intermediate representation (abstract syntax tree, or AST).
19402 these files use the same numbering scheme as the parser and semantics files.
19403 For example, the construction of record initialization procedures is done in
19404 @file{exp_ch3.adb}.
19407 The files prefixed with @file{^bind^BIND^} implement the binder, which
19408 verifies the consistency of the compilation, determines an order of
19409 elaboration, and generates the bind file.
19412 The files @file{atree.ads} and @file{atree.adb} detail the low-level
19413 data structures used by the front-end.
19416 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
19417 the abstract syntax tree as produced by the parser.
19420 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
19421 all entities, computed during semantic analysis.
19424 Library management issues are dealt with in files with prefix
19430 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
19431 defined in Annex A.
19436 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
19437 defined in Annex B.
19441 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
19442 both language-defined children and GNAT run-time routines.
19446 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
19447 general-purpose packages, fully documented in their specs. All
19448 the other @file{.c} files are modifications of common @command{gcc} files.
19451 @node Getting Internal Debugging Information
19452 @section Getting Internal Debugging Information
19455 Most compilers have internal debugging switches and modes. GNAT
19456 does also, except GNAT internal debugging switches and modes are not
19457 secret. A summary and full description of all the compiler and binder
19458 debug flags are in the file @file{debug.adb}. You must obtain the
19459 sources of the compiler to see the full detailed effects of these flags.
19461 The switches that print the source of the program (reconstructed from
19462 the internal tree) are of general interest for user programs, as are the
19464 the full internal tree, and the entity table (the symbol table
19465 information). The reconstructed source provides a readable version of the
19466 program after the front-end has completed analysis and expansion,
19467 and is useful when studying the performance of specific constructs.
19468 For example, constraint checks are indicated, complex aggregates
19469 are replaced with loops and assignments, and tasking primitives
19470 are replaced with run-time calls.
19472 @node Stack Traceback
19473 @section Stack Traceback
19475 @cindex stack traceback
19476 @cindex stack unwinding
19479 Traceback is a mechanism to display the sequence of subprogram calls that
19480 leads to a specified execution point in a program. Often (but not always)
19481 the execution point is an instruction at which an exception has been raised.
19482 This mechanism is also known as @i{stack unwinding} because it obtains
19483 its information by scanning the run-time stack and recovering the activation
19484 records of all active subprograms. Stack unwinding is one of the most
19485 important tools for program debugging.
19487 The first entry stored in traceback corresponds to the deepest calling level,
19488 that is to say the subprogram currently executing the instruction
19489 from which we want to obtain the traceback.
19491 Note that there is no runtime performance penalty when stack traceback
19492 is enabled, and no exception is raised during program execution.
19495 * Non-Symbolic Traceback::
19496 * Symbolic Traceback::
19499 @node Non-Symbolic Traceback
19500 @subsection Non-Symbolic Traceback
19501 @cindex traceback, non-symbolic
19504 Note: this feature is not supported on all platforms. See
19505 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
19509 * Tracebacks From an Unhandled Exception::
19510 * Tracebacks From Exception Occurrences (non-symbolic)::
19511 * Tracebacks From Anywhere in a Program (non-symbolic)::
19514 @node Tracebacks From an Unhandled Exception
19515 @subsubsection Tracebacks From an Unhandled Exception
19518 A runtime non-symbolic traceback is a list of addresses of call instructions.
19519 To enable this feature you must use the @option{-E}
19520 @code{gnatbind}'s option. With this option a stack traceback is stored as part
19521 of exception information. You can retrieve this information using the
19522 @code{addr2line} tool.
19524 Here is a simple example:
19526 @smallexample @c ada
19532 raise Constraint_Error;
19547 $ gnatmake stb -bargs -E
19550 Execution terminated by unhandled exception
19551 Exception name: CONSTRAINT_ERROR
19553 Call stack traceback locations:
19554 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
19558 As we see the traceback lists a sequence of addresses for the unhandled
19559 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
19560 guess that this exception come from procedure P1. To translate these
19561 addresses into the source lines where the calls appear, the
19562 @code{addr2line} tool, described below, is invaluable. The use of this tool
19563 requires the program to be compiled with debug information.
19566 $ gnatmake -g stb -bargs -E
19569 Execution terminated by unhandled exception
19570 Exception name: CONSTRAINT_ERROR
19572 Call stack traceback locations:
19573 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
19575 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
19576 0x4011f1 0x77e892a4
19578 00401373 at d:/stb/stb.adb:5
19579 0040138B at d:/stb/stb.adb:10
19580 0040139C at d:/stb/stb.adb:14
19581 00401335 at d:/stb/b~stb.adb:104
19582 004011C4 at /build/@dots{}/crt1.c:200
19583 004011F1 at /build/@dots{}/crt1.c:222
19584 77E892A4 in ?? at ??:0
19588 The @code{addr2line} tool has several other useful options:
19592 to get the function name corresponding to any location
19594 @item --demangle=gnat
19595 to use the gnat decoding mode for the function names. Note that
19596 for binutils version 2.9.x the option is simply @option{--demangle}.
19600 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
19601 0x40139c 0x401335 0x4011c4 0x4011f1
19603 00401373 in stb.p1 at d:/stb/stb.adb:5
19604 0040138B in stb.p2 at d:/stb/stb.adb:10
19605 0040139C in stb at d:/stb/stb.adb:14
19606 00401335 in main at d:/stb/b~stb.adb:104
19607 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
19608 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
19612 From this traceback we can see that the exception was raised in
19613 @file{stb.adb} at line 5, which was reached from a procedure call in
19614 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
19615 which contains the call to the main program.
19616 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
19617 and the output will vary from platform to platform.
19619 It is also possible to use @code{GDB} with these traceback addresses to debug
19620 the program. For example, we can break at a given code location, as reported
19621 in the stack traceback:
19627 Furthermore, this feature is not implemented inside Windows DLL. Only
19628 the non-symbolic traceback is reported in this case.
19631 (gdb) break *0x401373
19632 Breakpoint 1 at 0x401373: file stb.adb, line 5.
19636 It is important to note that the stack traceback addresses
19637 do not change when debug information is included. This is particularly useful
19638 because it makes it possible to release software without debug information (to
19639 minimize object size), get a field report that includes a stack traceback
19640 whenever an internal bug occurs, and then be able to retrieve the sequence
19641 of calls with the same program compiled with debug information.
19643 @node Tracebacks From Exception Occurrences (non-symbolic)
19644 @subsubsection Tracebacks From Exception Occurrences
19647 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
19648 The stack traceback is attached to the exception information string, and can
19649 be retrieved in an exception handler within the Ada program, by means of the
19650 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
19652 @smallexample @c ada
19654 with Ada.Exceptions;
19659 use Ada.Exceptions;
19667 Text_IO.Put_Line (Exception_Information (E));
19681 This program will output:
19686 Exception name: CONSTRAINT_ERROR
19687 Message: stb.adb:12
19688 Call stack traceback locations:
19689 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
19692 @node Tracebacks From Anywhere in a Program (non-symbolic)
19693 @subsubsection Tracebacks From Anywhere in a Program
19696 It is also possible to retrieve a stack traceback from anywhere in a
19697 program. For this you need to
19698 use the @code{GNAT.Traceback} API. This package includes a procedure called
19699 @code{Call_Chain} that computes a complete stack traceback, as well as useful
19700 display procedures described below. It is not necessary to use the
19701 @option{-E gnatbind} option in this case, because the stack traceback mechanism
19702 is invoked explicitly.
19705 In the following example we compute a traceback at a specific location in
19706 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
19707 convert addresses to strings:
19709 @smallexample @c ada
19711 with GNAT.Traceback;
19712 with GNAT.Debug_Utilities;
19718 use GNAT.Traceback;
19721 TB : Tracebacks_Array (1 .. 10);
19722 -- We are asking for a maximum of 10 stack frames.
19724 -- Len will receive the actual number of stack frames returned.
19726 Call_Chain (TB, Len);
19728 Text_IO.Put ("In STB.P1 : ");
19730 for K in 1 .. Len loop
19731 Text_IO.Put (Debug_Utilities.Image (TB (K)));
19752 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
19753 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
19757 You can then get further information by invoking the @code{addr2line}
19758 tool as described earlier (note that the hexadecimal addresses
19759 need to be specified in C format, with a leading ``0x'').
19761 @node Symbolic Traceback
19762 @subsection Symbolic Traceback
19763 @cindex traceback, symbolic
19766 A symbolic traceback is a stack traceback in which procedure names are
19767 associated with each code location.
19770 Note that this feature is not supported on all platforms. See
19771 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
19772 list of currently supported platforms.
19775 Note that the symbolic traceback requires that the program be compiled
19776 with debug information. If it is not compiled with debug information
19777 only the non-symbolic information will be valid.
19780 * Tracebacks From Exception Occurrences (symbolic)::
19781 * Tracebacks From Anywhere in a Program (symbolic)::
19784 @node Tracebacks From Exception Occurrences (symbolic)
19785 @subsubsection Tracebacks From Exception Occurrences
19787 @smallexample @c ada
19789 with GNAT.Traceback.Symbolic;
19795 raise Constraint_Error;
19812 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
19817 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
19820 0040149F in stb.p1 at stb.adb:8
19821 004014B7 in stb.p2 at stb.adb:13
19822 004014CF in stb.p3 at stb.adb:18
19823 004015DD in ada.stb at stb.adb:22
19824 00401461 in main at b~stb.adb:168
19825 004011C4 in __mingw_CRTStartup at crt1.c:200
19826 004011F1 in mainCRTStartup at crt1.c:222
19827 77E892A4 in ?? at ??:0
19831 In the above example the ``.\'' syntax in the @command{gnatmake} command
19832 is currently required by @command{addr2line} for files that are in
19833 the current working directory.
19834 Moreover, the exact sequence of linker options may vary from platform
19836 The above @option{-largs} section is for Windows platforms. By contrast,
19837 under Unix there is no need for the @option{-largs} section.
19838 Differences across platforms are due to details of linker implementation.
19840 @node Tracebacks From Anywhere in a Program (symbolic)
19841 @subsubsection Tracebacks From Anywhere in a Program
19844 It is possible to get a symbolic stack traceback
19845 from anywhere in a program, just as for non-symbolic tracebacks.
19846 The first step is to obtain a non-symbolic
19847 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
19848 information. Here is an example:
19850 @smallexample @c ada
19852 with GNAT.Traceback;
19853 with GNAT.Traceback.Symbolic;
19858 use GNAT.Traceback;
19859 use GNAT.Traceback.Symbolic;
19862 TB : Tracebacks_Array (1 .. 10);
19863 -- We are asking for a maximum of 10 stack frames.
19865 -- Len will receive the actual number of stack frames returned.
19867 Call_Chain (TB, Len);
19868 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
19881 @c ******************************
19883 @node Compatibility with HP Ada
19884 @chapter Compatibility with HP Ada
19885 @cindex Compatibility
19890 @cindex Compatibility between GNAT and HP Ada
19891 This chapter compares HP Ada (formerly known as ``DEC Ada'')
19892 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
19893 GNAT is highly compatible
19894 with HP Ada, and it should generally be straightforward to port code
19895 from the HP Ada environment to GNAT. However, there are a few language
19896 and implementation differences of which the user must be aware. These
19897 differences are discussed in this chapter. In
19898 addition, the operating environment and command structure for the
19899 compiler are different, and these differences are also discussed.
19901 For further details on these and other compatibility issues,
19902 see Appendix E of the HP publication
19903 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
19905 Except where otherwise indicated, the description of GNAT for OpenVMS
19906 applies to both the Alpha and I64 platforms.
19908 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
19909 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
19911 The discussion in this chapter addresses specifically the implementation
19912 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
19913 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
19914 GNAT always follows the Alpha implementation.
19916 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
19917 attributes are recognized, although only a subset of them can sensibly
19918 be implemented. The description of pragmas in
19919 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
19920 indicates whether or not they are applicable to non-VMS systems.
19923 * Ada Language Compatibility::
19924 * Differences in the Definition of Package System::
19925 * Language-Related Features::
19926 * The Package STANDARD::
19927 * The Package SYSTEM::
19928 * Tasking and Task-Related Features::
19929 * Pragmas and Pragma-Related Features::
19930 * Library of Predefined Units::
19932 * Main Program Definition::
19933 * Implementation-Defined Attributes::
19934 * Compiler and Run-Time Interfacing::
19935 * Program Compilation and Library Management::
19937 * Implementation Limits::
19938 * Tools and Utilities::
19941 @node Ada Language Compatibility
19942 @section Ada Language Compatibility
19945 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
19946 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
19947 with Ada 83, and therefore Ada 83 programs will compile
19948 and run under GNAT with
19949 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
19950 provides details on specific incompatibilities.
19952 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
19953 as well as the pragma @code{ADA_83}, to force the compiler to
19954 operate in Ada 83 mode. This mode does not guarantee complete
19955 conformance to Ada 83, but in practice is sufficient to
19956 eliminate most sources of incompatibilities.
19957 In particular, it eliminates the recognition of the
19958 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
19959 in Ada 83 programs is legal, and handles the cases of packages
19960 with optional bodies, and generics that instantiate unconstrained
19961 types without the use of @code{(<>)}.
19963 @node Differences in the Definition of Package System
19964 @section Differences in the Definition of Package @code{System}
19967 An Ada compiler is allowed to add
19968 implementation-dependent declarations to package @code{System}.
19970 GNAT does not take advantage of this permission, and the version of
19971 @code{System} provided by GNAT exactly matches that defined in the Ada
19974 However, HP Ada adds an extensive set of declarations to package
19976 as fully documented in the HP Ada manuals. To minimize changes required
19977 for programs that make use of these extensions, GNAT provides the pragma
19978 @code{Extend_System} for extending the definition of package System. By using:
19979 @cindex pragma @code{Extend_System}
19980 @cindex @code{Extend_System} pragma
19982 @smallexample @c ada
19985 pragma Extend_System (Aux_DEC);
19991 the set of definitions in @code{System} is extended to include those in
19992 package @code{System.Aux_DEC}.
19993 @cindex @code{System.Aux_DEC} package
19994 @cindex @code{Aux_DEC} package (child of @code{System})
19995 These definitions are incorporated directly into package @code{System},
19996 as though they had been declared there. For a
19997 list of the declarations added, see the spec of this package,
19998 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
19999 @cindex @file{s-auxdec.ads} file
20000 The pragma @code{Extend_System} is a configuration pragma, which means that
20001 it can be placed in the file @file{gnat.adc}, so that it will automatically
20002 apply to all subsequent compilations. See @ref{Configuration Pragmas},
20003 for further details.
20005 An alternative approach that avoids the use of the non-standard
20006 @code{Extend_System} pragma is to add a context clause to the unit that
20007 references these facilities:
20009 @smallexample @c ada
20011 with System.Aux_DEC;
20012 use System.Aux_DEC;
20017 The effect is not quite semantically identical to incorporating
20018 the declarations directly into package @code{System},
20019 but most programs will not notice a difference
20020 unless they use prefix notation (e.g.@: @code{System.Integer_8})
20021 to reference the entities directly in package @code{System}.
20022 For units containing such references,
20023 the prefixes must either be removed, or the pragma @code{Extend_System}
20026 @node Language-Related Features
20027 @section Language-Related Features
20030 The following sections highlight differences in types,
20031 representations of types, operations, alignment, and
20035 * Integer Types and Representations::
20036 * Floating-Point Types and Representations::
20037 * Pragmas Float_Representation and Long_Float::
20038 * Fixed-Point Types and Representations::
20039 * Record and Array Component Alignment::
20040 * Address Clauses::
20041 * Other Representation Clauses::
20044 @node Integer Types and Representations
20045 @subsection Integer Types and Representations
20048 The set of predefined integer types is identical in HP Ada and GNAT.
20049 Furthermore the representation of these integer types is also identical,
20050 including the capability of size clauses forcing biased representation.
20053 HP Ada for OpenVMS Alpha systems has defined the
20054 following additional integer types in package @code{System}:
20071 @code{LARGEST_INTEGER}
20075 In GNAT, the first four of these types may be obtained from the
20076 standard Ada package @code{Interfaces}.
20077 Alternatively, by use of the pragma @code{Extend_System}, identical
20078 declarations can be referenced directly in package @code{System}.
20079 On both GNAT and HP Ada, the maximum integer size is 64 bits.
20081 @node Floating-Point Types and Representations
20082 @subsection Floating-Point Types and Representations
20083 @cindex Floating-Point types
20086 The set of predefined floating-point types is identical in HP Ada and GNAT.
20087 Furthermore the representation of these floating-point
20088 types is also identical. One important difference is that the default
20089 representation for HP Ada is @code{VAX_Float}, but the default representation
20092 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
20093 pragma @code{Float_Representation} as described in the HP Ada
20095 For example, the declarations:
20097 @smallexample @c ada
20099 type F_Float is digits 6;
20100 pragma Float_Representation (VAX_Float, F_Float);
20105 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
20107 This set of declarations actually appears in @code{System.Aux_DEC},
20109 the full set of additional floating-point declarations provided in
20110 the HP Ada version of package @code{System}.
20111 This and similar declarations may be accessed in a user program
20112 by using pragma @code{Extend_System}. The use of this
20113 pragma, and the related pragma @code{Long_Float} is described in further
20114 detail in the following section.
20116 @node Pragmas Float_Representation and Long_Float
20117 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
20120 HP Ada provides the pragma @code{Float_Representation}, which
20121 acts as a program library switch to allow control over
20122 the internal representation chosen for the predefined
20123 floating-point types declared in the package @code{Standard}.
20124 The format of this pragma is as follows:
20126 @smallexample @c ada
20128 pragma Float_Representation(VAX_Float | IEEE_Float);
20133 This pragma controls the representation of floating-point
20138 @code{VAX_Float} specifies that floating-point
20139 types are represented by default with the VAX system hardware types
20140 @code{F-floating}, @code{D-floating}, @code{G-floating}.
20141 Note that the @code{H-floating}
20142 type was available only on VAX systems, and is not available
20143 in either HP Ada or GNAT.
20146 @code{IEEE_Float} specifies that floating-point
20147 types are represented by default with the IEEE single and
20148 double floating-point types.
20152 GNAT provides an identical implementation of the pragma
20153 @code{Float_Representation}, except that it functions as a
20154 configuration pragma. Note that the
20155 notion of configuration pragma corresponds closely to the
20156 HP Ada notion of a program library switch.
20158 When no pragma is used in GNAT, the default is @code{IEEE_Float},
20160 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
20161 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
20162 advisable to change the format of numbers passed to standard library
20163 routines, and if necessary explicit type conversions may be needed.
20165 The use of @code{IEEE_Float} is recommended in GNAT since it is more
20166 efficient, and (given that it conforms to an international standard)
20167 potentially more portable.
20168 The situation in which @code{VAX_Float} may be useful is in interfacing
20169 to existing code and data that expect the use of @code{VAX_Float}.
20170 In such a situation use the predefined @code{VAX_Float}
20171 types in package @code{System}, as extended by
20172 @code{Extend_System}. For example, use @code{System.F_Float}
20173 to specify the 32-bit @code{F-Float} format.
20176 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
20177 to allow control over the internal representation chosen
20178 for the predefined type @code{Long_Float} and for floating-point
20179 type declarations with digits specified in the range 7 .. 15.
20180 The format of this pragma is as follows:
20182 @smallexample @c ada
20184 pragma Long_Float (D_FLOAT | G_FLOAT);
20188 @node Fixed-Point Types and Representations
20189 @subsection Fixed-Point Types and Representations
20192 On HP Ada for OpenVMS Alpha systems, rounding is
20193 away from zero for both positive and negative numbers.
20194 Therefore, @code{+0.5} rounds to @code{1},
20195 and @code{-0.5} rounds to @code{-1}.
20197 On GNAT the results of operations
20198 on fixed-point types are in accordance with the Ada
20199 rules. In particular, results of operations on decimal
20200 fixed-point types are truncated.
20202 @node Record and Array Component Alignment
20203 @subsection Record and Array Component Alignment
20206 On HP Ada for OpenVMS Alpha, all non-composite components
20207 are aligned on natural boundaries. For example, 1-byte
20208 components are aligned on byte boundaries, 2-byte
20209 components on 2-byte boundaries, 4-byte components on 4-byte
20210 byte boundaries, and so on. The OpenVMS Alpha hardware
20211 runs more efficiently with naturally aligned data.
20213 On GNAT, alignment rules are compatible
20214 with HP Ada for OpenVMS Alpha.
20216 @node Address Clauses
20217 @subsection Address Clauses
20220 In HP Ada and GNAT, address clauses are supported for
20221 objects and imported subprograms.
20222 The predefined type @code{System.Address} is a private type
20223 in both compilers on Alpha OpenVMS, with the same representation
20224 (it is simply a machine pointer). Addition, subtraction, and comparison
20225 operations are available in the standard Ada package
20226 @code{System.Storage_Elements}, or in package @code{System}
20227 if it is extended to include @code{System.Aux_DEC} using a
20228 pragma @code{Extend_System} as previously described.
20230 Note that code that @code{with}'s both this extended package @code{System}
20231 and the package @code{System.Storage_Elements} should not @code{use}
20232 both packages, or ambiguities will result. In general it is better
20233 not to mix these two sets of facilities. The Ada package was
20234 designed specifically to provide the kind of features that HP Ada
20235 adds directly to package @code{System}.
20237 The type @code{System.Address} is a 64-bit integer type in GNAT for
20238 I64 OpenVMS. For more information,
20239 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
20241 GNAT is compatible with HP Ada in its handling of address
20242 clauses, except for some limitations in
20243 the form of address clauses for composite objects with
20244 initialization. Such address clauses are easily replaced
20245 by the use of an explicitly-defined constant as described
20246 in the Ada Reference Manual (13.1(22)). For example, the sequence
20249 @smallexample @c ada
20251 X, Y : Integer := Init_Func;
20252 Q : String (X .. Y) := "abc";
20254 for Q'Address use Compute_Address;
20259 will be rejected by GNAT, since the address cannot be computed at the time
20260 that @code{Q} is declared. To achieve the intended effect, write instead:
20262 @smallexample @c ada
20265 X, Y : Integer := Init_Func;
20266 Q_Address : constant Address := Compute_Address;
20267 Q : String (X .. Y) := "abc";
20269 for Q'Address use Q_Address;
20275 which will be accepted by GNAT (and other Ada compilers), and is also
20276 compatible with Ada 83. A fuller description of the restrictions
20277 on address specifications is found in @ref{Top, GNAT Reference Manual,
20278 About This Guide, gnat_rm, GNAT Reference Manual}.
20280 @node Other Representation Clauses
20281 @subsection Other Representation Clauses
20284 GNAT implements in a compatible manner all the representation
20285 clauses supported by HP Ada. In addition, GNAT
20286 implements the representation clause forms that were introduced in Ada 95,
20287 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
20289 @node The Package STANDARD
20290 @section The Package @code{STANDARD}
20293 The package @code{STANDARD}, as implemented by HP Ada, is fully
20294 described in the @cite{Ada Reference Manual} and in the
20295 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
20296 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
20298 In addition, HP Ada supports the Latin-1 character set in
20299 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
20300 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
20301 the type @code{WIDE_CHARACTER}.
20303 The floating-point types supported by GNAT are those
20304 supported by HP Ada, but the defaults are different, and are controlled by
20305 pragmas. See @ref{Floating-Point Types and Representations}, for details.
20307 @node The Package SYSTEM
20308 @section The Package @code{SYSTEM}
20311 HP Ada provides a specific version of the package
20312 @code{SYSTEM} for each platform on which the language is implemented.
20313 For the complete spec of the package @code{SYSTEM}, see
20314 Appendix F of the @cite{HP Ada Language Reference Manual}.
20316 On HP Ada, the package @code{SYSTEM} includes the following conversion
20319 @item @code{TO_ADDRESS(INTEGER)}
20321 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
20323 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
20325 @item @code{TO_INTEGER(ADDRESS)}
20327 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
20329 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
20330 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
20334 By default, GNAT supplies a version of @code{SYSTEM} that matches
20335 the definition given in the @cite{Ada Reference Manual}.
20337 is a subset of the HP system definitions, which is as
20338 close as possible to the original definitions. The only difference
20339 is that the definition of @code{SYSTEM_NAME} is different:
20341 @smallexample @c ada
20343 type Name is (SYSTEM_NAME_GNAT);
20344 System_Name : constant Name := SYSTEM_NAME_GNAT;
20349 Also, GNAT adds the Ada declarations for
20350 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
20352 However, the use of the following pragma causes GNAT
20353 to extend the definition of package @code{SYSTEM} so that it
20354 encompasses the full set of HP-specific extensions,
20355 including the functions listed above:
20357 @smallexample @c ada
20359 pragma Extend_System (Aux_DEC);
20364 The pragma @code{Extend_System} is a configuration pragma that
20365 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
20366 Extend_System,,, gnat_rm, GNAT Reference Manual}, for further details.
20368 HP Ada does not allow the recompilation of the package
20369 @code{SYSTEM}. Instead HP Ada provides several pragmas
20370 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
20371 to modify values in the package @code{SYSTEM}.
20372 On OpenVMS Alpha systems, the pragma
20373 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
20374 its single argument.
20376 GNAT does permit the recompilation of package @code{SYSTEM} using
20377 the special switch @option{-gnatg}, and this switch can be used if
20378 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
20379 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
20380 or @code{MEMORY_SIZE} by any other means.
20382 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
20383 enumeration literal @code{SYSTEM_NAME_GNAT}.
20385 The definitions provided by the use of
20387 @smallexample @c ada
20388 pragma Extend_System (AUX_Dec);
20392 are virtually identical to those provided by the HP Ada 83 package
20393 @code{SYSTEM}. One important difference is that the name of the
20395 function for type @code{UNSIGNED_LONGWORD} is changed to
20396 @code{TO_ADDRESS_LONG}.
20397 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual}, for a
20398 discussion of why this change was necessary.
20401 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
20403 an extension to Ada 83 not strictly compatible with the reference manual.
20404 GNAT, in order to be exactly compatible with the standard,
20405 does not provide this capability. In HP Ada 83, the
20406 point of this definition is to deal with a call like:
20408 @smallexample @c ada
20409 TO_ADDRESS (16#12777#);
20413 Normally, according to Ada 83 semantics, one would expect this to be
20414 ambiguous, since it matches both the @code{INTEGER} and
20415 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
20416 However, in HP Ada 83, there is no ambiguity, since the
20417 definition using @i{universal_integer} takes precedence.
20419 In GNAT, since the version with @i{universal_integer} cannot be supplied,
20421 not possible to be 100% compatible. Since there are many programs using
20422 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
20424 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
20425 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
20427 @smallexample @c ada
20428 function To_Address (X : Integer) return Address;
20429 pragma Pure_Function (To_Address);
20431 function To_Address_Long (X : Unsigned_Longword) return Address;
20432 pragma Pure_Function (To_Address_Long);
20436 This means that programs using @code{TO_ADDRESS} for
20437 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
20439 @node Tasking and Task-Related Features
20440 @section Tasking and Task-Related Features
20443 This section compares the treatment of tasking in GNAT
20444 and in HP Ada for OpenVMS Alpha.
20445 The GNAT description applies to both Alpha and I64 OpenVMS.
20446 For detailed information on tasking in
20447 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
20448 relevant run-time reference manual.
20451 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
20452 * Assigning Task IDs::
20453 * Task IDs and Delays::
20454 * Task-Related Pragmas::
20455 * Scheduling and Task Priority::
20457 * External Interrupts::
20460 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
20461 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
20464 On OpenVMS Alpha systems, each Ada task (except a passive
20465 task) is implemented as a single stream of execution
20466 that is created and managed by the kernel. On these
20467 systems, HP Ada tasking support is based on DECthreads,
20468 an implementation of the POSIX standard for threads.
20470 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
20471 code that calls DECthreads routines can be used together.
20472 The interaction between Ada tasks and DECthreads routines
20473 can have some benefits. For example when on OpenVMS Alpha,
20474 HP Ada can call C code that is already threaded.
20476 GNAT uses the facilities of DECthreads,
20477 and Ada tasks are mapped to threads.
20479 @node Assigning Task IDs
20480 @subsection Assigning Task IDs
20483 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
20484 the environment task that executes the main program. On
20485 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
20486 that have been created but are not yet activated.
20488 On OpenVMS Alpha systems, task IDs are assigned at
20489 activation. On GNAT systems, task IDs are also assigned at
20490 task creation but do not have the same form or values as
20491 task ID values in HP Ada. There is no null task, and the
20492 environment task does not have a specific task ID value.
20494 @node Task IDs and Delays
20495 @subsection Task IDs and Delays
20498 On OpenVMS Alpha systems, tasking delays are implemented
20499 using Timer System Services. The Task ID is used for the
20500 identification of the timer request (the @code{REQIDT} parameter).
20501 If Timers are used in the application take care not to use
20502 @code{0} for the identification, because cancelling such a timer
20503 will cancel all timers and may lead to unpredictable results.
20505 @node Task-Related Pragmas
20506 @subsection Task-Related Pragmas
20509 Ada supplies the pragma @code{TASK_STORAGE}, which allows
20510 specification of the size of the guard area for a task
20511 stack. (The guard area forms an area of memory that has no
20512 read or write access and thus helps in the detection of
20513 stack overflow.) On OpenVMS Alpha systems, if the pragma
20514 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
20515 area is created. In the absence of a pragma @code{TASK_STORAGE},
20516 a default guard area is created.
20518 GNAT supplies the following task-related pragmas:
20521 @item @code{TASK_INFO}
20523 This pragma appears within a task definition and
20524 applies to the task in which it appears. The argument
20525 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
20527 @item @code{TASK_STORAGE}
20529 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
20530 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
20531 @code{SUPPRESS}, and @code{VOLATILE}.
20533 @node Scheduling and Task Priority
20534 @subsection Scheduling and Task Priority
20537 HP Ada implements the Ada language requirement that
20538 when two tasks are eligible for execution and they have
20539 different priorities, the lower priority task does not
20540 execute while the higher priority task is waiting. The HP
20541 Ada Run-Time Library keeps a task running until either the
20542 task is suspended or a higher priority task becomes ready.
20544 On OpenVMS Alpha systems, the default strategy is round-
20545 robin with preemption. Tasks of equal priority take turns
20546 at the processor. A task is run for a certain period of
20547 time and then placed at the tail of the ready queue for
20548 its priority level.
20550 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
20551 which can be used to enable or disable round-robin
20552 scheduling of tasks with the same priority.
20553 See the relevant HP Ada run-time reference manual for
20554 information on using the pragmas to control HP Ada task
20557 GNAT follows the scheduling rules of Annex D (Real-Time
20558 Annex) of the @cite{Ada Reference Manual}. In general, this
20559 scheduling strategy is fully compatible with HP Ada
20560 although it provides some additional constraints (as
20561 fully documented in Annex D).
20562 GNAT implements time slicing control in a manner compatible with
20563 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
20564 are identical to the HP Ada 83 pragma of the same name.
20565 Note that it is not possible to mix GNAT tasking and
20566 HP Ada 83 tasking in the same program, since the two run-time
20567 libraries are not compatible.
20569 @node The Task Stack
20570 @subsection The Task Stack
20573 In HP Ada, a task stack is allocated each time a
20574 non-passive task is activated. As soon as the task is
20575 terminated, the storage for the task stack is deallocated.
20576 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
20577 a default stack size is used. Also, regardless of the size
20578 specified, some additional space is allocated for task
20579 management purposes. On OpenVMS Alpha systems, at least
20580 one page is allocated.
20582 GNAT handles task stacks in a similar manner. In accordance with
20583 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
20584 an alternative method for controlling the task stack size.
20585 The specification of the attribute @code{T'STORAGE_SIZE} is also
20586 supported in a manner compatible with HP Ada.
20588 @node External Interrupts
20589 @subsection External Interrupts
20592 On HP Ada, external interrupts can be associated with task entries.
20593 GNAT is compatible with HP Ada in its handling of external interrupts.
20595 @node Pragmas and Pragma-Related Features
20596 @section Pragmas and Pragma-Related Features
20599 Both HP Ada and GNAT supply all language-defined pragmas
20600 as specified by the Ada 83 standard. GNAT also supplies all
20601 language-defined pragmas introduced by Ada 95 and Ada 2005.
20602 In addition, GNAT implements the implementation-defined pragmas
20606 @item @code{AST_ENTRY}
20608 @item @code{COMMON_OBJECT}
20610 @item @code{COMPONENT_ALIGNMENT}
20612 @item @code{EXPORT_EXCEPTION}
20614 @item @code{EXPORT_FUNCTION}
20616 @item @code{EXPORT_OBJECT}
20618 @item @code{EXPORT_PROCEDURE}
20620 @item @code{EXPORT_VALUED_PROCEDURE}
20622 @item @code{FLOAT_REPRESENTATION}
20626 @item @code{IMPORT_EXCEPTION}
20628 @item @code{IMPORT_FUNCTION}
20630 @item @code{IMPORT_OBJECT}
20632 @item @code{IMPORT_PROCEDURE}
20634 @item @code{IMPORT_VALUED_PROCEDURE}
20636 @item @code{INLINE_GENERIC}
20638 @item @code{INTERFACE_NAME}
20640 @item @code{LONG_FLOAT}
20642 @item @code{MAIN_STORAGE}
20644 @item @code{PASSIVE}
20646 @item @code{PSECT_OBJECT}
20648 @item @code{SHARE_GENERIC}
20650 @item @code{SUPPRESS_ALL}
20652 @item @code{TASK_STORAGE}
20654 @item @code{TIME_SLICE}
20660 These pragmas are all fully implemented, with the exception of @code{TITLE},
20661 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
20662 recognized, but which have no
20663 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
20664 use of Ada protected objects. In GNAT, all generics are inlined.
20666 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
20667 a separate subprogram specification which must appear before the
20670 GNAT also supplies a number of implementation-defined pragmas as follows:
20672 @item @code{ABORT_DEFER}
20674 @item @code{ADA_83}
20676 @item @code{ADA_95}
20678 @item @code{ADA_05}
20680 @item @code{ANNOTATE}
20682 @item @code{ASSERT}
20684 @item @code{C_PASS_BY_COPY}
20686 @item @code{CPP_CLASS}
20688 @item @code{CPP_CONSTRUCTOR}
20690 @item @code{CPP_DESTRUCTOR}
20694 @item @code{EXTEND_SYSTEM}
20696 @item @code{LINKER_ALIAS}
20698 @item @code{LINKER_SECTION}
20700 @item @code{MACHINE_ATTRIBUTE}
20702 @item @code{NO_RETURN}
20704 @item @code{PURE_FUNCTION}
20706 @item @code{SOURCE_FILE_NAME}
20708 @item @code{SOURCE_REFERENCE}
20710 @item @code{TASK_INFO}
20712 @item @code{UNCHECKED_UNION}
20714 @item @code{UNIMPLEMENTED_UNIT}
20716 @item @code{UNIVERSAL_DATA}
20718 @item @code{UNSUPPRESS}
20720 @item @code{WARNINGS}
20722 @item @code{WEAK_EXTERNAL}
20726 For full details on these GNAT implementation-defined pragmas,
20727 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20731 * Restrictions on the Pragma INLINE::
20732 * Restrictions on the Pragma INTERFACE::
20733 * Restrictions on the Pragma SYSTEM_NAME::
20736 @node Restrictions on the Pragma INLINE
20737 @subsection Restrictions on Pragma @code{INLINE}
20740 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
20742 @item Parameters cannot have a task type.
20744 @item Function results cannot be task types, unconstrained
20745 array types, or unconstrained types with discriminants.
20747 @item Bodies cannot declare the following:
20749 @item Subprogram body or stub (imported subprogram is allowed)
20753 @item Generic declarations
20755 @item Instantiations
20759 @item Access types (types derived from access types allowed)
20761 @item Array or record types
20763 @item Dependent tasks
20765 @item Direct recursive calls of subprogram or containing
20766 subprogram, directly or via a renaming
20772 In GNAT, the only restriction on pragma @code{INLINE} is that the
20773 body must occur before the call if both are in the same
20774 unit, and the size must be appropriately small. There are
20775 no other specific restrictions which cause subprograms to
20776 be incapable of being inlined.
20778 @node Restrictions on the Pragma INTERFACE
20779 @subsection Restrictions on Pragma @code{INTERFACE}
20782 The following restrictions on pragma @code{INTERFACE}
20783 are enforced by both HP Ada and GNAT:
20785 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
20786 Default is the default on OpenVMS Alpha systems.
20788 @item Parameter passing: Language specifies default
20789 mechanisms but can be overridden with an @code{EXPORT} pragma.
20792 @item Ada: Use internal Ada rules.
20794 @item Bliss, C: Parameters must be mode @code{in}; cannot be
20795 record or task type. Result cannot be a string, an
20796 array, or a record.
20798 @item Fortran: Parameters cannot have a task type. Result cannot
20799 be a string, an array, or a record.
20804 GNAT is entirely upwards compatible with HP Ada, and in addition allows
20805 record parameters for all languages.
20807 @node Restrictions on the Pragma SYSTEM_NAME
20808 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
20811 For HP Ada for OpenVMS Alpha, the enumeration literal
20812 for the type @code{NAME} is @code{OPENVMS_AXP}.
20813 In GNAT, the enumeration
20814 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
20816 @node Library of Predefined Units
20817 @section Library of Predefined Units
20820 A library of predefined units is provided as part of the
20821 HP Ada and GNAT implementations. HP Ada does not provide
20822 the package @code{MACHINE_CODE} but instead recommends importing
20825 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
20826 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
20828 The HP Ada Predefined Library units are modified to remove post-Ada 83
20829 incompatibilities and to make them interoperable with GNAT
20830 (@pxref{Changes to DECLIB}, for details).
20831 The units are located in the @file{DECLIB} directory.
20833 The GNAT RTL is contained in
20834 the @file{ADALIB} directory, and
20835 the default search path is set up to find @code{DECLIB} units in preference
20836 to @code{ADALIB} units with the same name (@code{TEXT_IO},
20837 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
20840 * Changes to DECLIB::
20843 @node Changes to DECLIB
20844 @subsection Changes to @code{DECLIB}
20847 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
20848 compatibility are minor and include the following:
20851 @item Adjusting the location of pragmas and record representation
20852 clauses to obey Ada 95 (and thus Ada 2005) rules
20854 @item Adding the proper notation to generic formal parameters
20855 that take unconstrained types in instantiation
20857 @item Adding pragma @code{ELABORATE_BODY} to package specs
20858 that have package bodies not otherwise allowed
20860 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
20861 ``@code{PROTECTD}''.
20862 Currently these are found only in the @code{STARLET} package spec.
20864 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
20865 where the address size is constrained to 32 bits.
20869 None of the above changes is visible to users.
20875 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
20878 @item Command Language Interpreter (CLI interface)
20880 @item DECtalk Run-Time Library (DTK interface)
20882 @item Librarian utility routines (LBR interface)
20884 @item General Purpose Run-Time Library (LIB interface)
20886 @item Math Run-Time Library (MTH interface)
20888 @item National Character Set Run-Time Library (NCS interface)
20890 @item Compiled Code Support Run-Time Library (OTS interface)
20892 @item Parallel Processing Run-Time Library (PPL interface)
20894 @item Screen Management Run-Time Library (SMG interface)
20896 @item Sort Run-Time Library (SOR interface)
20898 @item String Run-Time Library (STR interface)
20900 @item STARLET System Library
20903 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
20905 @item X Windows Toolkit (XT interface)
20907 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
20911 GNAT provides implementations of these HP bindings in the @code{DECLIB}
20912 directory, on both the Alpha and I64 OpenVMS platforms.
20914 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
20916 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
20917 A pragma @code{Linker_Options} has been added to packages @code{Xm},
20918 @code{Xt}, and @code{X_Lib}
20919 causing the default X/Motif sharable image libraries to be linked in. This
20920 is done via options files named @file{xm.opt}, @file{xt.opt}, and
20921 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
20923 It may be necessary to edit these options files to update or correct the
20924 library names if, for example, the newer X/Motif bindings from
20925 @file{ADA$EXAMPLES}
20926 had been (previous to installing GNAT) copied and renamed to supersede the
20927 default @file{ADA$PREDEFINED} versions.
20930 * Shared Libraries and Options Files::
20931 * Interfaces to C::
20934 @node Shared Libraries and Options Files
20935 @subsection Shared Libraries and Options Files
20938 When using the HP Ada
20939 predefined X and Motif bindings, the linking with their sharable images is
20940 done automatically by @command{GNAT LINK}.
20941 When using other X and Motif bindings, you need
20942 to add the corresponding sharable images to the command line for
20943 @code{GNAT LINK}. When linking with shared libraries, or with
20944 @file{.OPT} files, you must
20945 also add them to the command line for @command{GNAT LINK}.
20947 A shared library to be used with GNAT is built in the same way as other
20948 libraries under VMS. The VMS Link command can be used in standard fashion.
20950 @node Interfaces to C
20951 @subsection Interfaces to C
20955 provides the following Ada types and operations:
20958 @item C types package (@code{C_TYPES})
20960 @item C strings (@code{C_TYPES.NULL_TERMINATED})
20962 @item Other_types (@code{SHORT_INT})
20966 Interfacing to C with GNAT, you can use the above approach
20967 described for HP Ada or the facilities of Annex B of
20968 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
20969 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
20970 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
20972 The @option{-gnatF} qualifier forces default and explicit
20973 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
20974 to be uppercased for compatibility with the default behavior
20975 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
20977 @node Main Program Definition
20978 @section Main Program Definition
20981 The following section discusses differences in the
20982 definition of main programs on HP Ada and GNAT.
20983 On HP Ada, main programs are defined to meet the
20984 following conditions:
20986 @item Procedure with no formal parameters (returns @code{0} upon
20989 @item Procedure with no formal parameters (returns @code{42} when
20990 an unhandled exception is raised)
20992 @item Function with no formal parameters whose returned value
20993 is of a discrete type
20995 @item Procedure with one @code{out} formal of a discrete type for
20996 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
21001 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
21002 a main function or main procedure returns a discrete
21003 value whose size is less than 64 bits (32 on VAX systems),
21004 the value is zero- or sign-extended as appropriate.
21005 On GNAT, main programs are defined as follows:
21007 @item Must be a non-generic, parameterless subprogram that
21008 is either a procedure or function returning an Ada
21009 @code{STANDARD.INTEGER} (the predefined type)
21011 @item Cannot be a generic subprogram or an instantiation of a
21015 @node Implementation-Defined Attributes
21016 @section Implementation-Defined Attributes
21019 GNAT provides all HP Ada implementation-defined
21022 @node Compiler and Run-Time Interfacing
21023 @section Compiler and Run-Time Interfacing
21026 HP Ada provides the following qualifiers to pass options to the linker
21029 @item @option{/WAIT} and @option{/SUBMIT}
21031 @item @option{/COMMAND}
21033 @item @option{/@r{[}NO@r{]}MAP}
21035 @item @option{/OUTPUT=@var{file-spec}}
21037 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
21041 To pass options to the linker, GNAT provides the following
21045 @item @option{/EXECUTABLE=@var{exec-name}}
21047 @item @option{/VERBOSE}
21049 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
21053 For more information on these switches, see
21054 @ref{Switches for gnatlink}.
21055 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
21056 to control optimization. HP Ada also supplies the
21059 @item @code{OPTIMIZE}
21061 @item @code{INLINE}
21063 @item @code{INLINE_GENERIC}
21065 @item @code{SUPPRESS_ALL}
21067 @item @code{PASSIVE}
21071 In GNAT, optimization is controlled strictly by command
21072 line parameters, as described in the corresponding section of this guide.
21073 The HP pragmas for control of optimization are
21074 recognized but ignored.
21076 Note that in GNAT, the default is optimization off, whereas in HP Ada
21077 the default is that optimization is turned on.
21079 @node Program Compilation and Library Management
21080 @section Program Compilation and Library Management
21083 HP Ada and GNAT provide a comparable set of commands to
21084 build programs. HP Ada also provides a program library,
21085 which is a concept that does not exist on GNAT. Instead,
21086 GNAT provides directories of sources that are compiled as
21089 The following table summarizes
21090 the HP Ada commands and provides
21091 equivalent GNAT commands. In this table, some GNAT
21092 equivalents reflect the fact that GNAT does not use the
21093 concept of a program library. Instead, it uses a model
21094 in which collections of source and object files are used
21095 in a manner consistent with other languages like C and
21096 Fortran. Therefore, standard system file commands are used
21097 to manipulate these elements. Those GNAT commands are marked with
21099 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
21102 @multitable @columnfractions .35 .65
21104 @item @emph{HP Ada Command}
21105 @tab @emph{GNAT Equivalent / Description}
21107 @item @command{ADA}
21108 @tab @command{GNAT COMPILE}@*
21109 Invokes the compiler to compile one or more Ada source files.
21111 @item @command{ACS ATTACH}@*
21112 @tab [No equivalent]@*
21113 Switches control of terminal from current process running the program
21116 @item @command{ACS CHECK}
21117 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
21118 Forms the execution closure of one
21119 or more compiled units and checks completeness and currency.
21121 @item @command{ACS COMPILE}
21122 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
21123 Forms the execution closure of one or
21124 more specified units, checks completeness and currency,
21125 identifies units that have revised source files, compiles same,
21126 and recompiles units that are or will become obsolete.
21127 Also completes incomplete generic instantiations.
21129 @item @command{ACS COPY FOREIGN}
21131 Copies a foreign object file into the program library as a
21134 @item @command{ACS COPY UNIT}
21136 Copies a compiled unit from one program library to another.
21138 @item @command{ACS CREATE LIBRARY}
21139 @tab Create /directory (*)@*
21140 Creates a program library.
21142 @item @command{ACS CREATE SUBLIBRARY}
21143 @tab Create /directory (*)@*
21144 Creates a program sublibrary.
21146 @item @command{ACS DELETE LIBRARY}
21148 Deletes a program library and its contents.
21150 @item @command{ACS DELETE SUBLIBRARY}
21152 Deletes a program sublibrary and its contents.
21154 @item @command{ACS DELETE UNIT}
21155 @tab Delete file (*)@*
21156 On OpenVMS systems, deletes one or more compiled units from
21157 the current program library.
21159 @item @command{ACS DIRECTORY}
21160 @tab Directory (*)@*
21161 On OpenVMS systems, lists units contained in the current
21164 @item @command{ACS ENTER FOREIGN}
21166 Allows the import of a foreign body as an Ada library
21167 spec and enters a reference to a pointer.
21169 @item @command{ACS ENTER UNIT}
21171 Enters a reference (pointer) from the current program library to
21172 a unit compiled into another program library.
21174 @item @command{ACS EXIT}
21175 @tab [No equivalent]@*
21176 Exits from the program library manager.
21178 @item @command{ACS EXPORT}
21180 Creates an object file that contains system-specific object code
21181 for one or more units. With GNAT, object files can simply be copied
21182 into the desired directory.
21184 @item @command{ACS EXTRACT SOURCE}
21186 Allows access to the copied source file for each Ada compilation unit
21188 @item @command{ACS HELP}
21189 @tab @command{HELP GNAT}@*
21190 Provides online help.
21192 @item @command{ACS LINK}
21193 @tab @command{GNAT LINK}@*
21194 Links an object file containing Ada units into an executable file.
21196 @item @command{ACS LOAD}
21198 Loads (partially compiles) Ada units into the program library.
21199 Allows loading a program from a collection of files into a library
21200 without knowing the relationship among units.
21202 @item @command{ACS MERGE}
21204 Merges into the current program library, one or more units from
21205 another library where they were modified.
21207 @item @command{ACS RECOMPILE}
21208 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
21209 Recompiles from external or copied source files any obsolete
21210 unit in the closure. Also, completes any incomplete generic
21213 @item @command{ACS REENTER}
21214 @tab @command{GNAT MAKE}@*
21215 Reenters current references to units compiled after last entered
21216 with the @command{ACS ENTER UNIT} command.
21218 @item @command{ACS SET LIBRARY}
21219 @tab Set default (*)@*
21220 Defines a program library to be the compilation context as well
21221 as the target library for compiler output and commands in general.
21223 @item @command{ACS SET PRAGMA}
21224 @tab Edit @file{gnat.adc} (*)@*
21225 Redefines specified values of the library characteristics
21226 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
21227 and @code{Float_Representation}.
21229 @item @command{ACS SET SOURCE}
21230 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
21231 Defines the source file search list for the @command{ACS COMPILE} command.
21233 @item @command{ACS SHOW LIBRARY}
21234 @tab Directory (*)@*
21235 Lists information about one or more program libraries.
21237 @item @command{ACS SHOW PROGRAM}
21238 @tab [No equivalent]@*
21239 Lists information about the execution closure of one or
21240 more units in the program library.
21242 @item @command{ACS SHOW SOURCE}
21243 @tab Show logical @code{ADA_INCLUDE_PATH}@*
21244 Shows the source file search used when compiling units.
21246 @item @command{ACS SHOW VERSION}
21247 @tab Compile with @option{VERBOSE} option
21248 Displays the version number of the compiler and program library
21251 @item @command{ACS SPAWN}
21252 @tab [No equivalent]@*
21253 Creates a subprocess of the current process (same as @command{DCL SPAWN}
21256 @item @command{ACS VERIFY}
21257 @tab [No equivalent]@*
21258 Performs a series of consistency checks on a program library to
21259 determine whether the library structure and library files are in
21266 @section Input-Output
21269 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
21270 Management Services (RMS) to perform operations on
21274 HP Ada and GNAT predefine an identical set of input-
21275 output packages. To make the use of the
21276 generic @code{TEXT_IO} operations more convenient, HP Ada
21277 provides predefined library packages that instantiate the
21278 integer and floating-point operations for the predefined
21279 integer and floating-point types as shown in the following table.
21281 @multitable @columnfractions .45 .55
21282 @item @emph{Package Name} @tab Instantiation
21284 @item @code{INTEGER_TEXT_IO}
21285 @tab @code{INTEGER_IO(INTEGER)}
21287 @item @code{SHORT_INTEGER_TEXT_IO}
21288 @tab @code{INTEGER_IO(SHORT_INTEGER)}
21290 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
21291 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
21293 @item @code{FLOAT_TEXT_IO}
21294 @tab @code{FLOAT_IO(FLOAT)}
21296 @item @code{LONG_FLOAT_TEXT_IO}
21297 @tab @code{FLOAT_IO(LONG_FLOAT)}
21301 The HP Ada predefined packages and their operations
21302 are implemented using OpenVMS Alpha files and input-output
21303 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
21304 Familiarity with the following is recommended:
21306 @item RMS file organizations and access methods
21308 @item OpenVMS file specifications and directories
21310 @item OpenVMS File Definition Language (FDL)
21314 GNAT provides I/O facilities that are completely
21315 compatible with HP Ada. The distribution includes the
21316 standard HP Ada versions of all I/O packages, operating
21317 in a manner compatible with HP Ada. In particular, the
21318 following packages are by default the HP Ada (Ada 83)
21319 versions of these packages rather than the renamings
21320 suggested in Annex J of the Ada Reference Manual:
21322 @item @code{TEXT_IO}
21324 @item @code{SEQUENTIAL_IO}
21326 @item @code{DIRECT_IO}
21330 The use of the standard child package syntax (for
21331 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
21333 GNAT provides HP-compatible predefined instantiations
21334 of the @code{TEXT_IO} packages, and also
21335 provides the standard predefined instantiations required
21336 by the @cite{Ada Reference Manual}.
21338 For further information on how GNAT interfaces to the file
21339 system or how I/O is implemented in programs written in
21340 mixed languages, see @ref{Implementation of the Standard I/O,,,
21341 gnat_rm, GNAT Reference Manual}.
21342 This chapter covers the following:
21344 @item Standard I/O packages
21346 @item @code{FORM} strings
21348 @item @code{ADA.DIRECT_IO}
21350 @item @code{ADA.SEQUENTIAL_IO}
21352 @item @code{ADA.TEXT_IO}
21354 @item Stream pointer positioning
21356 @item Reading and writing non-regular files
21358 @item @code{GET_IMMEDIATE}
21360 @item Treating @code{TEXT_IO} files as streams
21367 @node Implementation Limits
21368 @section Implementation Limits
21371 The following table lists implementation limits for HP Ada
21373 @multitable @columnfractions .60 .20 .20
21375 @item @emph{Compilation Parameter}
21380 @item In a subprogram or entry declaration, maximum number of
21381 formal parameters that are of an unconstrained record type
21386 @item Maximum identifier length (number of characters)
21391 @item Maximum number of characters in a source line
21396 @item Maximum collection size (number of bytes)
21401 @item Maximum number of discriminants for a record type
21406 @item Maximum number of formal parameters in an entry or
21407 subprogram declaration
21412 @item Maximum number of dimensions in an array type
21417 @item Maximum number of library units and subunits in a compilation.
21422 @item Maximum number of library units and subunits in an execution.
21427 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
21428 or @code{PSECT_OBJECT}
21433 @item Maximum number of enumeration literals in an enumeration type
21439 @item Maximum number of lines in a source file
21444 @item Maximum number of bits in any object
21449 @item Maximum size of the static portion of a stack frame (approximate)
21454 @node Tools and Utilities
21455 @section Tools and Utilities
21458 The following table lists some of the OpenVMS development tools
21459 available for HP Ada, and the corresponding tools for
21460 use with @value{EDITION} on Alpha and I64 platforms.
21461 Aside from the debugger, all the OpenVMS tools identified are part
21462 of the DECset package.
21465 @c Specify table in TeX since Texinfo does a poor job
21469 \settabs\+Language-Sensitive Editor\quad
21470 &Product with HP Ada\quad
21473 &\it Product with HP Ada
21474 & \it Product with GNAT Pro\cr
21476 \+Code Management System
21480 \+Language-Sensitive Editor
21482 & emacs or HP LSE (Alpha)\cr
21492 & OpenVMS Debug (I64)\cr
21494 \+Source Code Analyzer /
21511 \+Coverage Analyzer
21515 \+Module Management
21517 & Not applicable\cr
21527 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
21528 @c the TeX version above for the printed version
21530 @c @multitable @columnfractions .3 .4 .4
21531 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
21533 @tab @i{Tool with HP Ada}
21534 @tab @i{Tool with @value{EDITION}}
21535 @item Code Management@*System
21538 @item Language-Sensitive@*Editor
21540 @tab emacs or HP LSE (Alpha)
21549 @tab OpenVMS Debug (I64)
21550 @item Source Code Analyzer /@*Cross Referencer
21554 @tab HP Digital Test@*Manager (DTM)
21556 @item Performance and@*Coverage Analyzer
21559 @item Module Management@*System
21561 @tab Not applicable
21568 @c **************************************
21569 @node Platform-Specific Information for the Run-Time Libraries
21570 @appendix Platform-Specific Information for the Run-Time Libraries
21571 @cindex Tasking and threads libraries
21572 @cindex Threads libraries and tasking
21573 @cindex Run-time libraries (platform-specific information)
21576 The GNAT run-time implementation may vary with respect to both the
21577 underlying threads library and the exception handling scheme.
21578 For threads support, one or more of the following are supplied:
21580 @item @b{native threads library}, a binding to the thread package from
21581 the underlying operating system
21583 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
21584 POSIX thread package
21588 For exception handling, either or both of two models are supplied:
21590 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
21591 Most programs should experience a substantial speed improvement by
21592 being compiled with a ZCX run-time.
21593 This is especially true for
21594 tasking applications or applications with many exception handlers.}
21595 @cindex Zero-Cost Exceptions
21596 @cindex ZCX (Zero-Cost Exceptions)
21597 which uses binder-generated tables that
21598 are interrogated at run time to locate a handler
21600 @item @b{setjmp / longjmp} (``SJLJ''),
21601 @cindex setjmp/longjmp Exception Model
21602 @cindex SJLJ (setjmp/longjmp Exception Model)
21603 which uses dynamically-set data to establish
21604 the set of handlers
21608 This appendix summarizes which combinations of threads and exception support
21609 are supplied on various GNAT platforms.
21610 It then shows how to select a particular library either
21611 permanently or temporarily,
21612 explains the properties of (and tradeoffs among) the various threads
21613 libraries, and provides some additional
21614 information about several specific platforms.
21617 * Summary of Run-Time Configurations::
21618 * Specifying a Run-Time Library::
21619 * Choosing the Scheduling Policy::
21620 * Solaris-Specific Considerations::
21621 * Linux-Specific Considerations::
21622 * AIX-Specific Considerations::
21623 * Irix-Specific Considerations::
21624 * RTX-Specific Considerations::
21625 * HP-UX-Specific Considerations::
21628 @node Summary of Run-Time Configurations
21629 @section Summary of Run-Time Configurations
21631 @multitable @columnfractions .30 .70
21632 @item @b{alpha-openvms}
21633 @item @code{@ @ }@i{rts-native (default)}
21634 @item @code{@ @ @ @ }Tasking @tab native VMS threads
21635 @item @code{@ @ @ @ }Exceptions @tab ZCX
21637 @item @b{alpha-tru64}
21638 @item @code{@ @ }@i{rts-native (default)}
21639 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
21640 @item @code{@ @ @ @ }Exceptions @tab ZCX
21642 @item @code{@ @ }@i{rts-sjlj}
21643 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
21644 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21646 @item @b{ia64-hp_linux}
21647 @item @code{@ @ }@i{rts-native (default)}
21648 @item @code{@ @ @ @ }Tasking @tab pthread library
21649 @item @code{@ @ @ @ }Exceptions @tab ZCX
21651 @item @b{ia64-hpux}
21652 @item @code{@ @ }@i{rts-native (default)}
21653 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21654 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21656 @item @b{ia64-openvms}
21657 @item @code{@ @ }@i{rts-native (default)}
21658 @item @code{@ @ @ @ }Tasking @tab native VMS threads
21659 @item @code{@ @ @ @ }Exceptions @tab ZCX
21661 @item @b{ia64-sgi_linux}
21662 @item @code{@ @ }@i{rts-native (default)}
21663 @item @code{@ @ @ @ }Tasking @tab pthread library
21664 @item @code{@ @ @ @ }Exceptions @tab ZCX
21666 @item @b{mips-irix}
21667 @item @code{@ @ }@i{rts-native (default)}
21668 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
21669 @item @code{@ @ @ @ }Exceptions @tab ZCX
21672 @item @code{@ @ }@i{rts-native (default)}
21673 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21674 @item @code{@ @ @ @ }Exceptions @tab ZCX
21676 @item @code{@ @ }@i{rts-sjlj}
21677 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21678 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21681 @item @code{@ @ }@i{rts-native (default)}
21682 @item @code{@ @ @ @ }Tasking @tab native AIX threads
21683 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21685 @item @b{ppc-darwin}
21686 @item @code{@ @ }@i{rts-native (default)}
21687 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
21688 @item @code{@ @ @ @ }Exceptions @tab ZCX
21690 @item @b{sparc-solaris} @tab
21691 @item @code{@ @ }@i{rts-native (default)}
21692 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21693 @item @code{@ @ @ @ }Exceptions @tab ZCX
21695 @item @code{@ @ }@i{rts-pthread}
21696 @item @code{@ @ @ @ }Tasking @tab pthread library
21697 @item @code{@ @ @ @ }Exceptions @tab ZCX
21699 @item @code{@ @ }@i{rts-sjlj}
21700 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21701 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21703 @item @b{sparc64-solaris} @tab
21704 @item @code{@ @ }@i{rts-native (default)}
21705 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21706 @item @code{@ @ @ @ }Exceptions @tab ZCX
21708 @item @b{x86-linux}
21709 @item @code{@ @ }@i{rts-native (default)}
21710 @item @code{@ @ @ @ }Tasking @tab pthread library
21711 @item @code{@ @ @ @ }Exceptions @tab ZCX
21713 @item @code{@ @ }@i{rts-sjlj}
21714 @item @code{@ @ @ @ }Tasking @tab pthread library
21715 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21718 @item @code{@ @ }@i{rts-native (default)}
21719 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
21720 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21722 @item @b{x86-solaris}
21723 @item @code{@ @ }@i{rts-native (default)}
21724 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
21725 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21727 @item @b{x86-windows}
21728 @item @code{@ @ }@i{rts-native (default)}
21729 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
21730 @item @code{@ @ @ @ }Exceptions @tab ZCX
21732 @item @code{@ @ }@i{rts-sjlj (default)}
21733 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
21734 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21736 @item @b{x86-windows-rtx}
21737 @item @code{@ @ }@i{rts-rtx-rtss (default)}
21738 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
21739 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21741 @item @code{@ @ }@i{rts-rtx-w32}
21742 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
21743 @item @code{@ @ @ @ }Exceptions @tab ZCX
21745 @item @b{x86_64-linux}
21746 @item @code{@ @ }@i{rts-native (default)}
21747 @item @code{@ @ @ @ }Tasking @tab pthread library
21748 @item @code{@ @ @ @ }Exceptions @tab ZCX
21750 @item @code{@ @ }@i{rts-sjlj}
21751 @item @code{@ @ @ @ }Tasking @tab pthread library
21752 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21756 @node Specifying a Run-Time Library
21757 @section Specifying a Run-Time Library
21760 The @file{adainclude} subdirectory containing the sources of the GNAT
21761 run-time library, and the @file{adalib} subdirectory containing the
21762 @file{ALI} files and the static and/or shared GNAT library, are located
21763 in the gcc target-dependent area:
21766 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
21770 As indicated above, on some platforms several run-time libraries are supplied.
21771 These libraries are installed in the target dependent area and
21772 contain a complete source and binary subdirectory. The detailed description
21773 below explains the differences between the different libraries in terms of
21774 their thread support.
21776 The default run-time library (when GNAT is installed) is @emph{rts-native}.
21777 This default run time is selected by the means of soft links.
21778 For example on x86-linux:
21784 +--- adainclude----------+
21786 +--- adalib-----------+ |
21788 +--- rts-native | |
21790 | +--- adainclude <---+
21792 | +--- adalib <----+
21803 If the @i{rts-sjlj} library is to be selected on a permanent basis,
21804 these soft links can be modified with the following commands:
21808 $ rm -f adainclude adalib
21809 $ ln -s rts-sjlj/adainclude adainclude
21810 $ ln -s rts-sjlj/adalib adalib
21814 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
21815 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
21816 @file{$target/ada_object_path}.
21818 Selecting another run-time library temporarily can be
21819 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
21820 @cindex @option{--RTS} option
21822 @node Choosing the Scheduling Policy
21823 @section Choosing the Scheduling Policy
21826 When using a POSIX threads implementation, you have a choice of several
21827 scheduling policies: @code{SCHED_FIFO},
21828 @cindex @code{SCHED_FIFO} scheduling policy
21830 @cindex @code{SCHED_RR} scheduling policy
21831 and @code{SCHED_OTHER}.
21832 @cindex @code{SCHED_OTHER} scheduling policy
21833 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
21834 or @code{SCHED_RR} requires special (e.g., root) privileges.
21836 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
21838 @cindex @code{SCHED_FIFO} scheduling policy
21839 you can use one of the following:
21843 @code{pragma Time_Slice (0.0)}
21844 @cindex pragma Time_Slice
21846 the corresponding binder option @option{-T0}
21847 @cindex @option{-T0} option
21849 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
21850 @cindex pragma Task_Dispatching_Policy
21854 To specify @code{SCHED_RR},
21855 @cindex @code{SCHED_RR} scheduling policy
21856 you should use @code{pragma Time_Slice} with a
21857 value greater than @code{0.0}, or else use the corresponding @option{-T}
21860 @node Solaris-Specific Considerations
21861 @section Solaris-Specific Considerations
21862 @cindex Solaris Sparc threads libraries
21865 This section addresses some topics related to the various threads libraries
21869 * Solaris Threads Issues::
21872 @node Solaris Threads Issues
21873 @subsection Solaris Threads Issues
21876 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
21877 library based on POSIX threads --- @emph{rts-pthread}.
21878 @cindex rts-pthread threads library
21879 This run-time library has the advantage of being mostly shared across all
21880 POSIX-compliant thread implementations, and it also provides under
21881 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
21882 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
21883 and @code{PTHREAD_PRIO_PROTECT}
21884 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
21885 semantics that can be selected using the predefined pragma
21886 @code{Locking_Policy}
21887 @cindex pragma Locking_Policy (under rts-pthread)
21889 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
21890 @cindex @code{Inheritance_Locking} (under rts-pthread)
21891 @cindex @code{Ceiling_Locking} (under rts-pthread)
21893 As explained above, the native run-time library is based on the Solaris thread
21894 library (@code{libthread}) and is the default library.
21896 When the Solaris threads library is used (this is the default), programs
21897 compiled with GNAT can automatically take advantage of
21898 and can thus execute on multiple processors.
21899 The user can alternatively specify a processor on which the program should run
21900 to emulate a single-processor system. The multiprocessor / uniprocessor choice
21902 setting the environment variable @env{GNAT_PROCESSOR}
21903 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
21904 to one of the following:
21908 Use the default configuration (run the program on all
21909 available processors) - this is the same as having @code{GNAT_PROCESSOR}
21913 Let the run-time implementation choose one processor and run the program on
21916 @item 0 .. Last_Proc
21917 Run the program on the specified processor.
21918 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
21919 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
21922 @node Linux-Specific Considerations
21923 @section Linux-Specific Considerations
21924 @cindex Linux threads libraries
21927 On GNU/Linux without NPTL support (usually system with GNU C Library
21928 older than 2.3), the signal model is not POSIX compliant, which means
21929 that to send a signal to the process, you need to send the signal to all
21930 threads, e.g.@: by using @code{killpg()}.
21932 @node AIX-Specific Considerations
21933 @section AIX-Specific Considerations
21934 @cindex AIX resolver library
21937 On AIX, the resolver library initializes some internal structure on
21938 the first call to @code{get*by*} functions, which are used to implement
21939 @code{GNAT.Sockets.Get_Host_By_Name} and
21940 @code{GNAT.Sockets.Get_Host_By_Address}.
21941 If such initialization occurs within an Ada task, and the stack size for
21942 the task is the default size, a stack overflow may occur.
21944 To avoid this overflow, the user should either ensure that the first call
21945 to @code{GNAT.Sockets.Get_Host_By_Name} or
21946 @code{GNAT.Sockets.Get_Host_By_Addrss}
21947 occurs in the environment task, or use @code{pragma Storage_Size} to
21948 specify a sufficiently large size for the stack of the task that contains
21951 @node Irix-Specific Considerations
21952 @section Irix-Specific Considerations
21953 @cindex Irix libraries
21956 The GCC support libraries coming with the Irix compiler have moved to
21957 their canonical place with respect to the general Irix ABI related
21958 conventions. Running applications built with the default shared GNAT
21959 run-time now requires the LD_LIBRARY_PATH environment variable to
21960 include this location. A possible way to achieve this is to issue the
21961 following command line on a bash prompt:
21965 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
21969 @node RTX-Specific Considerations
21970 @section RTX-Specific Considerations
21971 @cindex RTX libraries
21974 The Real-time Extension (RTX) to Windows is based on the Windows Win32
21975 API. Applications can be built to work in two different modes:
21979 Windows executables that run in Ring 3 to utilize memory protection
21980 (@emph{rts-rtx-w32}).
21983 Real-time subsystem (RTSS) executables that run in Ring 0, where
21984 performance can be optimized with RTSS applications taking precedent
21985 over all Windows applications (@emph{rts-rtx-rtss}). This mode requires
21986 the Microsoft linker to handle RTSS libraries.
21990 @node HP-UX-Specific Considerations
21991 @section HP-UX-Specific Considerations
21992 @cindex HP-UX Scheduling
21995 On HP-UX, appropriate privileges are required to change the scheduling
21996 parameters of a task. The calling process must have appropriate
21997 privileges or be a member of a group having @code{PRIV_RTSCHED} access to
21998 successfully change the scheduling parameters.
22000 By default, GNAT uses the @code{SCHED_HPUX} policy. To have access to the
22001 priority range 0-31 either the @code{FIFO_Within_Priorities} or the
22002 @code{Round_Robin_Within_Priorities} scheduling policies need to be set.
22004 To specify the @code{FIFO_Within_Priorities} scheduling policy you can use
22005 one of the following:
22009 @code{pragma Time_Slice (0.0)}
22010 @cindex pragma Time_Slice
22012 the corresponding binder option @option{-T0}
22013 @cindex @option{-T0} option
22015 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
22016 @cindex pragma Task_Dispatching_Policy
22020 To specify the @code{Round_Robin_Within_Priorities}, scheduling policy
22021 you should use @code{pragma Time_Slice} with a
22022 value greater than @code{0.0}, or use the corresponding @option{-T}
22023 binder option, or set the @code{pragma Task_Dispatching_Policy
22024 (Round_Robin_Within_Priorities)}.
22026 @c *******************************
22027 @node Example of Binder Output File
22028 @appendix Example of Binder Output File
22031 This Appendix displays the source code for @command{gnatbind}'s output
22032 file generated for a simple ``Hello World'' program.
22033 Comments have been added for clarification purposes.
22035 @smallexample @c adanocomment
22039 -- The package is called Ada_Main unless this name is actually used
22040 -- as a unit name in the partition, in which case some other unique
22044 package ada_main is
22046 Elab_Final_Code : Integer;
22047 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
22049 -- The main program saves the parameters (argument count,
22050 -- argument values, environment pointer) in global variables
22051 -- for later access by other units including
22052 -- Ada.Command_Line.
22054 gnat_argc : Integer;
22055 gnat_argv : System.Address;
22056 gnat_envp : System.Address;
22058 -- The actual variables are stored in a library routine. This
22059 -- is useful for some shared library situations, where there
22060 -- are problems if variables are not in the library.
22062 pragma Import (C, gnat_argc);
22063 pragma Import (C, gnat_argv);
22064 pragma Import (C, gnat_envp);
22066 -- The exit status is similarly an external location
22068 gnat_exit_status : Integer;
22069 pragma Import (C, gnat_exit_status);
22071 GNAT_Version : constant String :=
22072 "GNAT Version: 6.0.0w (20061115)";
22073 pragma Export (C, GNAT_Version, "__gnat_version");
22075 -- This is the generated adafinal routine that performs
22076 -- finalization at the end of execution. In the case where
22077 -- Ada is the main program, this main program makes a call
22078 -- to adafinal at program termination.
22080 procedure adafinal;
22081 pragma Export (C, adafinal, "adafinal");
22083 -- This is the generated adainit routine that performs
22084 -- initialization at the start of execution. In the case
22085 -- where Ada is the main program, this main program makes
22086 -- a call to adainit at program startup.
22089 pragma Export (C, adainit, "adainit");
22091 -- This routine is called at the start of execution. It is
22092 -- a dummy routine that is used by the debugger to breakpoint
22093 -- at the start of execution.
22095 procedure Break_Start;
22096 pragma Import (C, Break_Start, "__gnat_break_start");
22098 -- This is the actual generated main program (it would be
22099 -- suppressed if the no main program switch were used). As
22100 -- required by standard system conventions, this program has
22101 -- the external name main.
22105 argv : System.Address;
22106 envp : System.Address)
22108 pragma Export (C, main, "main");
22110 -- The following set of constants give the version
22111 -- identification values for every unit in the bound
22112 -- partition. This identification is computed from all
22113 -- dependent semantic units, and corresponds to the
22114 -- string that would be returned by use of the
22115 -- Body_Version or Version attributes.
22117 type Version_32 is mod 2 ** 32;
22118 u00001 : constant Version_32 := 16#7880BEB3#;
22119 u00002 : constant Version_32 := 16#0D24CBD0#;
22120 u00003 : constant Version_32 := 16#3283DBEB#;
22121 u00004 : constant Version_32 := 16#2359F9ED#;
22122 u00005 : constant Version_32 := 16#664FB847#;
22123 u00006 : constant Version_32 := 16#68E803DF#;
22124 u00007 : constant Version_32 := 16#5572E604#;
22125 u00008 : constant Version_32 := 16#46B173D8#;
22126 u00009 : constant Version_32 := 16#156A40CF#;
22127 u00010 : constant Version_32 := 16#033DABE0#;
22128 u00011 : constant Version_32 := 16#6AB38FEA#;
22129 u00012 : constant Version_32 := 16#22B6217D#;
22130 u00013 : constant Version_32 := 16#68A22947#;
22131 u00014 : constant Version_32 := 16#18CC4A56#;
22132 u00015 : constant Version_32 := 16#08258E1B#;
22133 u00016 : constant Version_32 := 16#367D5222#;
22134 u00017 : constant Version_32 := 16#20C9ECA4#;
22135 u00018 : constant Version_32 := 16#50D32CB6#;
22136 u00019 : constant Version_32 := 16#39A8BB77#;
22137 u00020 : constant Version_32 := 16#5CF8FA2B#;
22138 u00021 : constant Version_32 := 16#2F1EB794#;
22139 u00022 : constant Version_32 := 16#31AB6444#;
22140 u00023 : constant Version_32 := 16#1574B6E9#;
22141 u00024 : constant Version_32 := 16#5109C189#;
22142 u00025 : constant Version_32 := 16#56D770CD#;
22143 u00026 : constant Version_32 := 16#02F9DE3D#;
22144 u00027 : constant Version_32 := 16#08AB6B2C#;
22145 u00028 : constant Version_32 := 16#3FA37670#;
22146 u00029 : constant Version_32 := 16#476457A0#;
22147 u00030 : constant Version_32 := 16#731E1B6E#;
22148 u00031 : constant Version_32 := 16#23C2E789#;
22149 u00032 : constant Version_32 := 16#0F1BD6A1#;
22150 u00033 : constant Version_32 := 16#7C25DE96#;
22151 u00034 : constant Version_32 := 16#39ADFFA2#;
22152 u00035 : constant Version_32 := 16#571DE3E7#;
22153 u00036 : constant Version_32 := 16#5EB646AB#;
22154 u00037 : constant Version_32 := 16#4249379B#;
22155 u00038 : constant Version_32 := 16#0357E00A#;
22156 u00039 : constant Version_32 := 16#3784FB72#;
22157 u00040 : constant Version_32 := 16#2E723019#;
22158 u00041 : constant Version_32 := 16#623358EA#;
22159 u00042 : constant Version_32 := 16#107F9465#;
22160 u00043 : constant Version_32 := 16#6843F68A#;
22161 u00044 : constant Version_32 := 16#63305874#;
22162 u00045 : constant Version_32 := 16#31E56CE1#;
22163 u00046 : constant Version_32 := 16#02917970#;
22164 u00047 : constant Version_32 := 16#6CCBA70E#;
22165 u00048 : constant Version_32 := 16#41CD4204#;
22166 u00049 : constant Version_32 := 16#572E3F58#;
22167 u00050 : constant Version_32 := 16#20729FF5#;
22168 u00051 : constant Version_32 := 16#1D4F93E8#;
22169 u00052 : constant Version_32 := 16#30B2EC3D#;
22170 u00053 : constant Version_32 := 16#34054F96#;
22171 u00054 : constant Version_32 := 16#5A199860#;
22172 u00055 : constant Version_32 := 16#0E7F912B#;
22173 u00056 : constant Version_32 := 16#5760634A#;
22174 u00057 : constant Version_32 := 16#5D851835#;
22176 -- The following Export pragmas export the version numbers
22177 -- with symbolic names ending in B (for body) or S
22178 -- (for spec) so that they can be located in a link. The
22179 -- information provided here is sufficient to track down
22180 -- the exact versions of units used in a given build.
22182 pragma Export (C, u00001, "helloB");
22183 pragma Export (C, u00002, "system__standard_libraryB");
22184 pragma Export (C, u00003, "system__standard_libraryS");
22185 pragma Export (C, u00004, "adaS");
22186 pragma Export (C, u00005, "ada__text_ioB");
22187 pragma Export (C, u00006, "ada__text_ioS");
22188 pragma Export (C, u00007, "ada__exceptionsB");
22189 pragma Export (C, u00008, "ada__exceptionsS");
22190 pragma Export (C, u00009, "gnatS");
22191 pragma Export (C, u00010, "gnat__heap_sort_aB");
22192 pragma Export (C, u00011, "gnat__heap_sort_aS");
22193 pragma Export (C, u00012, "systemS");
22194 pragma Export (C, u00013, "system__exception_tableB");
22195 pragma Export (C, u00014, "system__exception_tableS");
22196 pragma Export (C, u00015, "gnat__htableB");
22197 pragma Export (C, u00016, "gnat__htableS");
22198 pragma Export (C, u00017, "system__exceptionsS");
22199 pragma Export (C, u00018, "system__machine_state_operationsB");
22200 pragma Export (C, u00019, "system__machine_state_operationsS");
22201 pragma Export (C, u00020, "system__machine_codeS");
22202 pragma Export (C, u00021, "system__storage_elementsB");
22203 pragma Export (C, u00022, "system__storage_elementsS");
22204 pragma Export (C, u00023, "system__secondary_stackB");
22205 pragma Export (C, u00024, "system__secondary_stackS");
22206 pragma Export (C, u00025, "system__parametersB");
22207 pragma Export (C, u00026, "system__parametersS");
22208 pragma Export (C, u00027, "system__soft_linksB");
22209 pragma Export (C, u00028, "system__soft_linksS");
22210 pragma Export (C, u00029, "system__stack_checkingB");
22211 pragma Export (C, u00030, "system__stack_checkingS");
22212 pragma Export (C, u00031, "system__tracebackB");
22213 pragma Export (C, u00032, "system__tracebackS");
22214 pragma Export (C, u00033, "ada__streamsS");
22215 pragma Export (C, u00034, "ada__tagsB");
22216 pragma Export (C, u00035, "ada__tagsS");
22217 pragma Export (C, u00036, "system__string_opsB");
22218 pragma Export (C, u00037, "system__string_opsS");
22219 pragma Export (C, u00038, "interfacesS");
22220 pragma Export (C, u00039, "interfaces__c_streamsB");
22221 pragma Export (C, u00040, "interfaces__c_streamsS");
22222 pragma Export (C, u00041, "system__file_ioB");
22223 pragma Export (C, u00042, "system__file_ioS");
22224 pragma Export (C, u00043, "ada__finalizationB");
22225 pragma Export (C, u00044, "ada__finalizationS");
22226 pragma Export (C, u00045, "system__finalization_rootB");
22227 pragma Export (C, u00046, "system__finalization_rootS");
22228 pragma Export (C, u00047, "system__finalization_implementationB");
22229 pragma Export (C, u00048, "system__finalization_implementationS");
22230 pragma Export (C, u00049, "system__string_ops_concat_3B");
22231 pragma Export (C, u00050, "system__string_ops_concat_3S");
22232 pragma Export (C, u00051, "system__stream_attributesB");
22233 pragma Export (C, u00052, "system__stream_attributesS");
22234 pragma Export (C, u00053, "ada__io_exceptionsS");
22235 pragma Export (C, u00054, "system__unsigned_typesS");
22236 pragma Export (C, u00055, "system__file_control_blockS");
22237 pragma Export (C, u00056, "ada__finalization__list_controllerB");
22238 pragma Export (C, u00057, "ada__finalization__list_controllerS");
22240 -- BEGIN ELABORATION ORDER
22243 -- gnat.heap_sort_a (spec)
22244 -- gnat.heap_sort_a (body)
22245 -- gnat.htable (spec)
22246 -- gnat.htable (body)
22247 -- interfaces (spec)
22249 -- system.machine_code (spec)
22250 -- system.parameters (spec)
22251 -- system.parameters (body)
22252 -- interfaces.c_streams (spec)
22253 -- interfaces.c_streams (body)
22254 -- system.standard_library (spec)
22255 -- ada.exceptions (spec)
22256 -- system.exception_table (spec)
22257 -- system.exception_table (body)
22258 -- ada.io_exceptions (spec)
22259 -- system.exceptions (spec)
22260 -- system.storage_elements (spec)
22261 -- system.storage_elements (body)
22262 -- system.machine_state_operations (spec)
22263 -- system.machine_state_operations (body)
22264 -- system.secondary_stack (spec)
22265 -- system.stack_checking (spec)
22266 -- system.soft_links (spec)
22267 -- system.soft_links (body)
22268 -- system.stack_checking (body)
22269 -- system.secondary_stack (body)
22270 -- system.standard_library (body)
22271 -- system.string_ops (spec)
22272 -- system.string_ops (body)
22275 -- ada.streams (spec)
22276 -- system.finalization_root (spec)
22277 -- system.finalization_root (body)
22278 -- system.string_ops_concat_3 (spec)
22279 -- system.string_ops_concat_3 (body)
22280 -- system.traceback (spec)
22281 -- system.traceback (body)
22282 -- ada.exceptions (body)
22283 -- system.unsigned_types (spec)
22284 -- system.stream_attributes (spec)
22285 -- system.stream_attributes (body)
22286 -- system.finalization_implementation (spec)
22287 -- system.finalization_implementation (body)
22288 -- ada.finalization (spec)
22289 -- ada.finalization (body)
22290 -- ada.finalization.list_controller (spec)
22291 -- ada.finalization.list_controller (body)
22292 -- system.file_control_block (spec)
22293 -- system.file_io (spec)
22294 -- system.file_io (body)
22295 -- ada.text_io (spec)
22296 -- ada.text_io (body)
22298 -- END ELABORATION ORDER
22302 -- The following source file name pragmas allow the generated file
22303 -- names to be unique for different main programs. They are needed
22304 -- since the package name will always be Ada_Main.
22306 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
22307 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
22309 -- Generated package body for Ada_Main starts here
22311 package body ada_main is
22313 -- The actual finalization is performed by calling the
22314 -- library routine in System.Standard_Library.Adafinal
22316 procedure Do_Finalize;
22317 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
22324 procedure adainit is
22326 -- These booleans are set to True once the associated unit has
22327 -- been elaborated. It is also used to avoid elaborating the
22328 -- same unit twice.
22331 pragma Import (Ada, E040, "interfaces__c_streams_E");
22334 pragma Import (Ada, E008, "ada__exceptions_E");
22337 pragma Import (Ada, E014, "system__exception_table_E");
22340 pragma Import (Ada, E053, "ada__io_exceptions_E");
22343 pragma Import (Ada, E017, "system__exceptions_E");
22346 pragma Import (Ada, E024, "system__secondary_stack_E");
22349 pragma Import (Ada, E030, "system__stack_checking_E");
22352 pragma Import (Ada, E028, "system__soft_links_E");
22355 pragma Import (Ada, E035, "ada__tags_E");
22358 pragma Import (Ada, E033, "ada__streams_E");
22361 pragma Import (Ada, E046, "system__finalization_root_E");
22364 pragma Import (Ada, E048, "system__finalization_implementation_E");
22367 pragma Import (Ada, E044, "ada__finalization_E");
22370 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
22373 pragma Import (Ada, E055, "system__file_control_block_E");
22376 pragma Import (Ada, E042, "system__file_io_E");
22379 pragma Import (Ada, E006, "ada__text_io_E");
22381 -- Set_Globals is a library routine that stores away the
22382 -- value of the indicated set of global values in global
22383 -- variables within the library.
22385 procedure Set_Globals
22386 (Main_Priority : Integer;
22387 Time_Slice_Value : Integer;
22388 WC_Encoding : Character;
22389 Locking_Policy : Character;
22390 Queuing_Policy : Character;
22391 Task_Dispatching_Policy : Character;
22392 Adafinal : System.Address;
22393 Unreserve_All_Interrupts : Integer;
22394 Exception_Tracebacks : Integer);
22395 @findex __gnat_set_globals
22396 pragma Import (C, Set_Globals, "__gnat_set_globals");
22398 -- SDP_Table_Build is a library routine used to build the
22399 -- exception tables. See unit Ada.Exceptions in files
22400 -- a-except.ads/adb for full details of how zero cost
22401 -- exception handling works. This procedure, the call to
22402 -- it, and the two following tables are all omitted if the
22403 -- build is in longjmp/setjmp exception mode.
22405 @findex SDP_Table_Build
22406 @findex Zero Cost Exceptions
22407 procedure SDP_Table_Build
22408 (SDP_Addresses : System.Address;
22409 SDP_Count : Natural;
22410 Elab_Addresses : System.Address;
22411 Elab_Addr_Count : Natural);
22412 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
22414 -- Table of Unit_Exception_Table addresses. Used for zero
22415 -- cost exception handling to build the top level table.
22417 ST : aliased constant array (1 .. 23) of System.Address := (
22419 Ada.Text_Io'UET_Address,
22420 Ada.Exceptions'UET_Address,
22421 Gnat.Heap_Sort_A'UET_Address,
22422 System.Exception_Table'UET_Address,
22423 System.Machine_State_Operations'UET_Address,
22424 System.Secondary_Stack'UET_Address,
22425 System.Parameters'UET_Address,
22426 System.Soft_Links'UET_Address,
22427 System.Stack_Checking'UET_Address,
22428 System.Traceback'UET_Address,
22429 Ada.Streams'UET_Address,
22430 Ada.Tags'UET_Address,
22431 System.String_Ops'UET_Address,
22432 Interfaces.C_Streams'UET_Address,
22433 System.File_Io'UET_Address,
22434 Ada.Finalization'UET_Address,
22435 System.Finalization_Root'UET_Address,
22436 System.Finalization_Implementation'UET_Address,
22437 System.String_Ops_Concat_3'UET_Address,
22438 System.Stream_Attributes'UET_Address,
22439 System.File_Control_Block'UET_Address,
22440 Ada.Finalization.List_Controller'UET_Address);
22442 -- Table of addresses of elaboration routines. Used for
22443 -- zero cost exception handling to make sure these
22444 -- addresses are included in the top level procedure
22447 EA : aliased constant array (1 .. 23) of System.Address := (
22448 adainit'Code_Address,
22449 Do_Finalize'Code_Address,
22450 Ada.Exceptions'Elab_Spec'Address,
22451 System.Exceptions'Elab_Spec'Address,
22452 Interfaces.C_Streams'Elab_Spec'Address,
22453 System.Exception_Table'Elab_Body'Address,
22454 Ada.Io_Exceptions'Elab_Spec'Address,
22455 System.Stack_Checking'Elab_Spec'Address,
22456 System.Soft_Links'Elab_Body'Address,
22457 System.Secondary_Stack'Elab_Body'Address,
22458 Ada.Tags'Elab_Spec'Address,
22459 Ada.Tags'Elab_Body'Address,
22460 Ada.Streams'Elab_Spec'Address,
22461 System.Finalization_Root'Elab_Spec'Address,
22462 Ada.Exceptions'Elab_Body'Address,
22463 System.Finalization_Implementation'Elab_Spec'Address,
22464 System.Finalization_Implementation'Elab_Body'Address,
22465 Ada.Finalization'Elab_Spec'Address,
22466 Ada.Finalization.List_Controller'Elab_Spec'Address,
22467 System.File_Control_Block'Elab_Spec'Address,
22468 System.File_Io'Elab_Body'Address,
22469 Ada.Text_Io'Elab_Spec'Address,
22470 Ada.Text_Io'Elab_Body'Address);
22472 -- Start of processing for adainit
22476 -- Call SDP_Table_Build to build the top level procedure
22477 -- table for zero cost exception handling (omitted in
22478 -- longjmp/setjmp mode).
22480 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
22482 -- Call Set_Globals to record various information for
22483 -- this partition. The values are derived by the binder
22484 -- from information stored in the ali files by the compiler.
22486 @findex __gnat_set_globals
22488 (Main_Priority => -1,
22489 -- Priority of main program, -1 if no pragma Priority used
22491 Time_Slice_Value => -1,
22492 -- Time slice from Time_Slice pragma, -1 if none used
22494 WC_Encoding => 'b',
22495 -- Wide_Character encoding used, default is brackets
22497 Locking_Policy => ' ',
22498 -- Locking_Policy used, default of space means not
22499 -- specified, otherwise it is the first character of
22500 -- the policy name.
22502 Queuing_Policy => ' ',
22503 -- Queuing_Policy used, default of space means not
22504 -- specified, otherwise it is the first character of
22505 -- the policy name.
22507 Task_Dispatching_Policy => ' ',
22508 -- Task_Dispatching_Policy used, default of space means
22509 -- not specified, otherwise first character of the
22512 Adafinal => System.Null_Address,
22513 -- Address of Adafinal routine, not used anymore
22515 Unreserve_All_Interrupts => 0,
22516 -- Set true if pragma Unreserve_All_Interrupts was used
22518 Exception_Tracebacks => 0);
22519 -- Indicates if exception tracebacks are enabled
22521 Elab_Final_Code := 1;
22523 -- Now we have the elaboration calls for all units in the partition.
22524 -- The Elab_Spec and Elab_Body attributes generate references to the
22525 -- implicit elaboration procedures generated by the compiler for
22526 -- each unit that requires elaboration.
22529 Interfaces.C_Streams'Elab_Spec;
22533 Ada.Exceptions'Elab_Spec;
22536 System.Exception_Table'Elab_Body;
22540 Ada.Io_Exceptions'Elab_Spec;
22544 System.Exceptions'Elab_Spec;
22548 System.Stack_Checking'Elab_Spec;
22551 System.Soft_Links'Elab_Body;
22556 System.Secondary_Stack'Elab_Body;
22560 Ada.Tags'Elab_Spec;
22563 Ada.Tags'Elab_Body;
22567 Ada.Streams'Elab_Spec;
22571 System.Finalization_Root'Elab_Spec;
22575 Ada.Exceptions'Elab_Body;
22579 System.Finalization_Implementation'Elab_Spec;
22582 System.Finalization_Implementation'Elab_Body;
22586 Ada.Finalization'Elab_Spec;
22590 Ada.Finalization.List_Controller'Elab_Spec;
22594 System.File_Control_Block'Elab_Spec;
22598 System.File_Io'Elab_Body;
22602 Ada.Text_Io'Elab_Spec;
22605 Ada.Text_Io'Elab_Body;
22609 Elab_Final_Code := 0;
22617 procedure adafinal is
22626 -- main is actually a function, as in the ANSI C standard,
22627 -- defined to return the exit status. The three parameters
22628 -- are the argument count, argument values and environment
22631 @findex Main Program
22634 argv : System.Address;
22635 envp : System.Address)
22638 -- The initialize routine performs low level system
22639 -- initialization using a standard library routine which
22640 -- sets up signal handling and performs any other
22641 -- required setup. The routine can be found in file
22644 @findex __gnat_initialize
22645 procedure initialize;
22646 pragma Import (C, initialize, "__gnat_initialize");
22648 -- The finalize routine performs low level system
22649 -- finalization using a standard library routine. The
22650 -- routine is found in file a-final.c and in the standard
22651 -- distribution is a dummy routine that does nothing, so
22652 -- really this is a hook for special user finalization.
22654 @findex __gnat_finalize
22655 procedure finalize;
22656 pragma Import (C, finalize, "__gnat_finalize");
22658 -- We get to the main program of the partition by using
22659 -- pragma Import because if we try to with the unit and
22660 -- call it Ada style, then not only do we waste time
22661 -- recompiling it, but also, we don't really know the right
22662 -- switches (e.g.@: identifier character set) to be used
22665 procedure Ada_Main_Program;
22666 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
22668 -- Start of processing for main
22671 -- Save global variables
22677 -- Call low level system initialization
22681 -- Call our generated Ada initialization routine
22685 -- This is the point at which we want the debugger to get
22690 -- Now we call the main program of the partition
22694 -- Perform Ada finalization
22698 -- Perform low level system finalization
22702 -- Return the proper exit status
22703 return (gnat_exit_status);
22706 -- This section is entirely comments, so it has no effect on the
22707 -- compilation of the Ada_Main package. It provides the list of
22708 -- object files and linker options, as well as some standard
22709 -- libraries needed for the link. The gnatlink utility parses
22710 -- this b~hello.adb file to read these comment lines to generate
22711 -- the appropriate command line arguments for the call to the
22712 -- system linker. The BEGIN/END lines are used for sentinels for
22713 -- this parsing operation.
22715 -- The exact file names will of course depend on the environment,
22716 -- host/target and location of files on the host system.
22718 @findex Object file list
22719 -- BEGIN Object file/option list
22722 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
22723 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
22724 -- END Object file/option list
22730 The Ada code in the above example is exactly what is generated by the
22731 binder. We have added comments to more clearly indicate the function
22732 of each part of the generated @code{Ada_Main} package.
22734 The code is standard Ada in all respects, and can be processed by any
22735 tools that handle Ada. In particular, it is possible to use the debugger
22736 in Ada mode to debug the generated @code{Ada_Main} package. For example,
22737 suppose that for reasons that you do not understand, your program is crashing
22738 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
22739 you can place a breakpoint on the call:
22741 @smallexample @c ada
22742 Ada.Text_Io'Elab_Body;
22746 and trace the elaboration routine for this package to find out where
22747 the problem might be (more usually of course you would be debugging
22748 elaboration code in your own application).
22750 @node Elaboration Order Handling in GNAT
22751 @appendix Elaboration Order Handling in GNAT
22752 @cindex Order of elaboration
22753 @cindex Elaboration control
22756 * Elaboration Code::
22757 * Checking the Elaboration Order::
22758 * Controlling the Elaboration Order::
22759 * Controlling Elaboration in GNAT - Internal Calls::
22760 * Controlling Elaboration in GNAT - External Calls::
22761 * Default Behavior in GNAT - Ensuring Safety::
22762 * Treatment of Pragma Elaborate::
22763 * Elaboration Issues for Library Tasks::
22764 * Mixing Elaboration Models::
22765 * What to Do If the Default Elaboration Behavior Fails::
22766 * Elaboration for Access-to-Subprogram Values::
22767 * Summary of Procedures for Elaboration Control::
22768 * Other Elaboration Order Considerations::
22772 This chapter describes the handling of elaboration code in Ada and
22773 in GNAT, and discusses how the order of elaboration of program units can
22774 be controlled in GNAT, either automatically or with explicit programming
22777 @node Elaboration Code
22778 @section Elaboration Code
22781 Ada provides rather general mechanisms for executing code at elaboration
22782 time, that is to say before the main program starts executing. Such code arises
22786 @item Initializers for variables.
22787 Variables declared at the library level, in package specs or bodies, can
22788 require initialization that is performed at elaboration time, as in:
22789 @smallexample @c ada
22791 Sqrt_Half : Float := Sqrt (0.5);
22795 @item Package initialization code
22796 Code in a @code{BEGIN-END} section at the outer level of a package body is
22797 executed as part of the package body elaboration code.
22799 @item Library level task allocators
22800 Tasks that are declared using task allocators at the library level
22801 start executing immediately and hence can execute at elaboration time.
22805 Subprogram calls are possible in any of these contexts, which means that
22806 any arbitrary part of the program may be executed as part of the elaboration
22807 code. It is even possible to write a program which does all its work at
22808 elaboration time, with a null main program, although stylistically this
22809 would usually be considered an inappropriate way to structure
22812 An important concern arises in the context of elaboration code:
22813 we have to be sure that it is executed in an appropriate order. What we
22814 have is a series of elaboration code sections, potentially one section
22815 for each unit in the program. It is important that these execute
22816 in the correct order. Correctness here means that, taking the above
22817 example of the declaration of @code{Sqrt_Half},
22818 if some other piece of
22819 elaboration code references @code{Sqrt_Half},
22820 then it must run after the
22821 section of elaboration code that contains the declaration of
22824 There would never be any order of elaboration problem if we made a rule
22825 that whenever you @code{with} a unit, you must elaborate both the spec and body
22826 of that unit before elaborating the unit doing the @code{with}'ing:
22828 @smallexample @c ada
22832 package Unit_2 is @dots{}
22838 would require that both the body and spec of @code{Unit_1} be elaborated
22839 before the spec of @code{Unit_2}. However, a rule like that would be far too
22840 restrictive. In particular, it would make it impossible to have routines
22841 in separate packages that were mutually recursive.
22843 You might think that a clever enough compiler could look at the actual
22844 elaboration code and determine an appropriate correct order of elaboration,
22845 but in the general case, this is not possible. Consider the following
22848 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
22850 the variable @code{Sqrt_1}, which is declared in the elaboration code
22851 of the body of @code{Unit_1}:
22853 @smallexample @c ada
22855 Sqrt_1 : Float := Sqrt (0.1);
22860 The elaboration code of the body of @code{Unit_1} also contains:
22862 @smallexample @c ada
22865 if expression_1 = 1 then
22866 Q := Unit_2.Func_2;
22873 @code{Unit_2} is exactly parallel,
22874 it has a procedure @code{Func_2} that references
22875 the variable @code{Sqrt_2}, which is declared in the elaboration code of
22876 the body @code{Unit_2}:
22878 @smallexample @c ada
22880 Sqrt_2 : Float := Sqrt (0.1);
22885 The elaboration code of the body of @code{Unit_2} also contains:
22887 @smallexample @c ada
22890 if expression_2 = 2 then
22891 Q := Unit_1.Func_1;
22898 Now the question is, which of the following orders of elaboration is
22923 If you carefully analyze the flow here, you will see that you cannot tell
22924 at compile time the answer to this question.
22925 If @code{expression_1} is not equal to 1,
22926 and @code{expression_2} is not equal to 2,
22927 then either order is acceptable, because neither of the function calls is
22928 executed. If both tests evaluate to true, then neither order is acceptable
22929 and in fact there is no correct order.
22931 If one of the two expressions is true, and the other is false, then one
22932 of the above orders is correct, and the other is incorrect. For example,
22933 if @code{expression_1} /= 1 and @code{expression_2} = 2,
22934 then the call to @code{Func_1}
22935 will occur, but not the call to @code{Func_2.}
22936 This means that it is essential
22937 to elaborate the body of @code{Unit_1} before
22938 the body of @code{Unit_2}, so the first
22939 order of elaboration is correct and the second is wrong.
22941 By making @code{expression_1} and @code{expression_2}
22942 depend on input data, or perhaps
22943 the time of day, we can make it impossible for the compiler or binder
22944 to figure out which of these expressions will be true, and hence it
22945 is impossible to guarantee a safe order of elaboration at run time.
22947 @node Checking the Elaboration Order
22948 @section Checking the Elaboration Order
22951 In some languages that involve the same kind of elaboration problems,
22952 e.g.@: Java and C++, the programmer is expected to worry about these
22953 ordering problems himself, and it is common to
22954 write a program in which an incorrect elaboration order gives
22955 surprising results, because it references variables before they
22957 Ada is designed to be a safe language, and a programmer-beware approach is
22958 clearly not sufficient. Consequently, the language provides three lines
22962 @item Standard rules
22963 Some standard rules restrict the possible choice of elaboration
22964 order. In particular, if you @code{with} a unit, then its spec is always
22965 elaborated before the unit doing the @code{with}. Similarly, a parent
22966 spec is always elaborated before the child spec, and finally
22967 a spec is always elaborated before its corresponding body.
22969 @item Dynamic elaboration checks
22970 @cindex Elaboration checks
22971 @cindex Checks, elaboration
22972 Dynamic checks are made at run time, so that if some entity is accessed
22973 before it is elaborated (typically by means of a subprogram call)
22974 then the exception (@code{Program_Error}) is raised.
22976 @item Elaboration control
22977 Facilities are provided for the programmer to specify the desired order
22981 Let's look at these facilities in more detail. First, the rules for
22982 dynamic checking. One possible rule would be simply to say that the
22983 exception is raised if you access a variable which has not yet been
22984 elaborated. The trouble with this approach is that it could require
22985 expensive checks on every variable reference. Instead Ada has two
22986 rules which are a little more restrictive, but easier to check, and
22990 @item Restrictions on calls
22991 A subprogram can only be called at elaboration time if its body
22992 has been elaborated. The rules for elaboration given above guarantee
22993 that the spec of the subprogram has been elaborated before the
22994 call, but not the body. If this rule is violated, then the
22995 exception @code{Program_Error} is raised.
22997 @item Restrictions on instantiations
22998 A generic unit can only be instantiated if the body of the generic
22999 unit has been elaborated. Again, the rules for elaboration given above
23000 guarantee that the spec of the generic unit has been elaborated
23001 before the instantiation, but not the body. If this rule is
23002 violated, then the exception @code{Program_Error} is raised.
23006 The idea is that if the body has been elaborated, then any variables
23007 it references must have been elaborated; by checking for the body being
23008 elaborated we guarantee that none of its references causes any
23009 trouble. As we noted above, this is a little too restrictive, because a
23010 subprogram that has no non-local references in its body may in fact be safe
23011 to call. However, it really would be unsafe to rely on this, because
23012 it would mean that the caller was aware of details of the implementation
23013 in the body. This goes against the basic tenets of Ada.
23015 A plausible implementation can be described as follows.
23016 A Boolean variable is associated with each subprogram
23017 and each generic unit. This variable is initialized to False, and is set to
23018 True at the point body is elaborated. Every call or instantiation checks the
23019 variable, and raises @code{Program_Error} if the variable is False.
23021 Note that one might think that it would be good enough to have one Boolean
23022 variable for each package, but that would not deal with cases of trying
23023 to call a body in the same package as the call
23024 that has not been elaborated yet.
23025 Of course a compiler may be able to do enough analysis to optimize away
23026 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
23027 does such optimizations, but still the easiest conceptual model is to
23028 think of there being one variable per subprogram.
23030 @node Controlling the Elaboration Order
23031 @section Controlling the Elaboration Order
23034 In the previous section we discussed the rules in Ada which ensure
23035 that @code{Program_Error} is raised if an incorrect elaboration order is
23036 chosen. This prevents erroneous executions, but we need mechanisms to
23037 specify a correct execution and avoid the exception altogether.
23038 To achieve this, Ada provides a number of features for controlling
23039 the order of elaboration. We discuss these features in this section.
23041 First, there are several ways of indicating to the compiler that a given
23042 unit has no elaboration problems:
23045 @item packages that do not require a body
23046 A library package that does not require a body does not permit
23047 a body (this rule was introduced in Ada 95).
23048 Thus if we have a such a package, as in:
23050 @smallexample @c ada
23053 package Definitions is
23055 type m is new integer;
23057 type a is array (1 .. 10) of m;
23058 type b is array (1 .. 20) of m;
23066 A package that @code{with}'s @code{Definitions} may safely instantiate
23067 @code{Definitions.Subp} because the compiler can determine that there
23068 definitely is no package body to worry about in this case
23071 @cindex pragma Pure
23073 Places sufficient restrictions on a unit to guarantee that
23074 no call to any subprogram in the unit can result in an
23075 elaboration problem. This means that the compiler does not need
23076 to worry about the point of elaboration of such units, and in
23077 particular, does not need to check any calls to any subprograms
23080 @item pragma Preelaborate
23081 @findex Preelaborate
23082 @cindex pragma Preelaborate
23083 This pragma places slightly less stringent restrictions on a unit than
23085 but these restrictions are still sufficient to ensure that there
23086 are no elaboration problems with any calls to the unit.
23088 @item pragma Elaborate_Body
23089 @findex Elaborate_Body
23090 @cindex pragma Elaborate_Body
23091 This pragma requires that the body of a unit be elaborated immediately
23092 after its spec. Suppose a unit @code{A} has such a pragma,
23093 and unit @code{B} does
23094 a @code{with} of unit @code{A}. Recall that the standard rules require
23095 the spec of unit @code{A}
23096 to be elaborated before the @code{with}'ing unit; given the pragma in
23097 @code{A}, we also know that the body of @code{A}
23098 will be elaborated before @code{B}, so
23099 that calls to @code{A} are safe and do not need a check.
23104 unlike pragma @code{Pure} and pragma @code{Preelaborate},
23106 @code{Elaborate_Body} does not guarantee that the program is
23107 free of elaboration problems, because it may not be possible
23108 to satisfy the requested elaboration order.
23109 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
23111 marks @code{Unit_1} as @code{Elaborate_Body},
23112 and not @code{Unit_2,} then the order of
23113 elaboration will be:
23125 Now that means that the call to @code{Func_1} in @code{Unit_2}
23126 need not be checked,
23127 it must be safe. But the call to @code{Func_2} in
23128 @code{Unit_1} may still fail if
23129 @code{Expression_1} is equal to 1,
23130 and the programmer must still take
23131 responsibility for this not being the case.
23133 If all units carry a pragma @code{Elaborate_Body}, then all problems are
23134 eliminated, except for calls entirely within a body, which are
23135 in any case fully under programmer control. However, using the pragma
23136 everywhere is not always possible.
23137 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
23138 we marked both of them as having pragma @code{Elaborate_Body}, then
23139 clearly there would be no possible elaboration order.
23141 The above pragmas allow a server to guarantee safe use by clients, and
23142 clearly this is the preferable approach. Consequently a good rule
23143 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
23144 and if this is not possible,
23145 mark them as @code{Elaborate_Body} if possible.
23146 As we have seen, there are situations where neither of these
23147 three pragmas can be used.
23148 So we also provide methods for clients to control the
23149 order of elaboration of the servers on which they depend:
23152 @item pragma Elaborate (unit)
23154 @cindex pragma Elaborate
23155 This pragma is placed in the context clause, after a @code{with} clause,
23156 and it requires that the body of the named unit be elaborated before
23157 the unit in which the pragma occurs. The idea is to use this pragma
23158 if the current unit calls at elaboration time, directly or indirectly,
23159 some subprogram in the named unit.
23161 @item pragma Elaborate_All (unit)
23162 @findex Elaborate_All
23163 @cindex pragma Elaborate_All
23164 This is a stronger version of the Elaborate pragma. Consider the
23168 Unit A @code{with}'s unit B and calls B.Func in elab code
23169 Unit B @code{with}'s unit C, and B.Func calls C.Func
23173 Now if we put a pragma @code{Elaborate (B)}
23174 in unit @code{A}, this ensures that the
23175 body of @code{B} is elaborated before the call, but not the
23176 body of @code{C}, so
23177 the call to @code{C.Func} could still cause @code{Program_Error} to
23180 The effect of a pragma @code{Elaborate_All} is stronger, it requires
23181 not only that the body of the named unit be elaborated before the
23182 unit doing the @code{with}, but also the bodies of all units that the
23183 named unit uses, following @code{with} links transitively. For example,
23184 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
23186 not only that the body of @code{B} be elaborated before @code{A},
23188 body of @code{C}, because @code{B} @code{with}'s @code{C}.
23192 We are now in a position to give a usage rule in Ada for avoiding
23193 elaboration problems, at least if dynamic dispatching and access to
23194 subprogram values are not used. We will handle these cases separately
23197 The rule is simple. If a unit has elaboration code that can directly or
23198 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
23199 a generic package in a @code{with}'ed unit,
23200 then if the @code{with}'ed unit does not have
23201 pragma @code{Pure} or @code{Preelaborate}, then the client should have
23202 a pragma @code{Elaborate_All}
23203 for the @code{with}'ed unit. By following this rule a client is
23204 assured that calls can be made without risk of an exception.
23206 For generic subprogram instantiations, the rule can be relaxed to
23207 require only a pragma @code{Elaborate} since elaborating the body
23208 of a subprogram cannot cause any transitive elaboration (we are
23209 not calling the subprogram in this case, just elaborating its
23212 If this rule is not followed, then a program may be in one of four
23216 @item No order exists
23217 No order of elaboration exists which follows the rules, taking into
23218 account any @code{Elaborate}, @code{Elaborate_All},
23219 or @code{Elaborate_Body} pragmas. In
23220 this case, an Ada compiler must diagnose the situation at bind
23221 time, and refuse to build an executable program.
23223 @item One or more orders exist, all incorrect
23224 One or more acceptable elaboration orders exist, and all of them
23225 generate an elaboration order problem. In this case, the binder
23226 can build an executable program, but @code{Program_Error} will be raised
23227 when the program is run.
23229 @item Several orders exist, some right, some incorrect
23230 One or more acceptable elaboration orders exists, and some of them
23231 work, and some do not. The programmer has not controlled
23232 the order of elaboration, so the binder may or may not pick one of
23233 the correct orders, and the program may or may not raise an
23234 exception when it is run. This is the worst case, because it means
23235 that the program may fail when moved to another compiler, or even
23236 another version of the same compiler.
23238 @item One or more orders exists, all correct
23239 One ore more acceptable elaboration orders exist, and all of them
23240 work. In this case the program runs successfully. This state of
23241 affairs can be guaranteed by following the rule we gave above, but
23242 may be true even if the rule is not followed.
23246 Note that one additional advantage of following our rules on the use
23247 of @code{Elaborate} and @code{Elaborate_All}
23248 is that the program continues to stay in the ideal (all orders OK) state
23249 even if maintenance
23250 changes some bodies of some units. Conversely, if a program that does
23251 not follow this rule happens to be safe at some point, this state of affairs
23252 may deteriorate silently as a result of maintenance changes.
23254 You may have noticed that the above discussion did not mention
23255 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
23256 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
23257 code in the body makes calls to some other unit, so it is still necessary
23258 to use @code{Elaborate_All} on such units.
23260 @node Controlling Elaboration in GNAT - Internal Calls
23261 @section Controlling Elaboration in GNAT - Internal Calls
23264 In the case of internal calls, i.e., calls within a single package, the
23265 programmer has full control over the order of elaboration, and it is up
23266 to the programmer to elaborate declarations in an appropriate order. For
23269 @smallexample @c ada
23272 function One return Float;
23276 function One return Float is
23285 will obviously raise @code{Program_Error} at run time, because function
23286 One will be called before its body is elaborated. In this case GNAT will
23287 generate a warning that the call will raise @code{Program_Error}:
23293 2. function One return Float;
23295 4. Q : Float := One;
23297 >>> warning: cannot call "One" before body is elaborated
23298 >>> warning: Program_Error will be raised at run time
23301 6. function One return Float is
23314 Note that in this particular case, it is likely that the call is safe, because
23315 the function @code{One} does not access any global variables.
23316 Nevertheless in Ada, we do not want the validity of the check to depend on
23317 the contents of the body (think about the separate compilation case), so this
23318 is still wrong, as we discussed in the previous sections.
23320 The error is easily corrected by rearranging the declarations so that the
23321 body of @code{One} appears before the declaration containing the call
23322 (note that in Ada 95 and Ada 2005,
23323 declarations can appear in any order, so there is no restriction that
23324 would prevent this reordering, and if we write:
23326 @smallexample @c ada
23329 function One return Float;
23331 function One return Float is
23342 then all is well, no warning is generated, and no
23343 @code{Program_Error} exception
23345 Things are more complicated when a chain of subprograms is executed:
23347 @smallexample @c ada
23350 function A return Integer;
23351 function B return Integer;
23352 function C return Integer;
23354 function B return Integer is begin return A; end;
23355 function C return Integer is begin return B; end;
23359 function A return Integer is begin return 1; end;
23365 Now the call to @code{C}
23366 at elaboration time in the declaration of @code{X} is correct, because
23367 the body of @code{C} is already elaborated,
23368 and the call to @code{B} within the body of
23369 @code{C} is correct, but the call
23370 to @code{A} within the body of @code{B} is incorrect, because the body
23371 of @code{A} has not been elaborated, so @code{Program_Error}
23372 will be raised on the call to @code{A}.
23373 In this case GNAT will generate a
23374 warning that @code{Program_Error} may be
23375 raised at the point of the call. Let's look at the warning:
23381 2. function A return Integer;
23382 3. function B return Integer;
23383 4. function C return Integer;
23385 6. function B return Integer is begin return A; end;
23387 >>> warning: call to "A" before body is elaborated may
23388 raise Program_Error
23389 >>> warning: "B" called at line 7
23390 >>> warning: "C" called at line 9
23392 7. function C return Integer is begin return B; end;
23394 9. X : Integer := C;
23396 11. function A return Integer is begin return 1; end;
23406 Note that the message here says ``may raise'', instead of the direct case,
23407 where the message says ``will be raised''. That's because whether
23409 actually called depends in general on run-time flow of control.
23410 For example, if the body of @code{B} said
23412 @smallexample @c ada
23415 function B return Integer is
23417 if some-condition-depending-on-input-data then
23428 then we could not know until run time whether the incorrect call to A would
23429 actually occur, so @code{Program_Error} might
23430 or might not be raised. It is possible for a compiler to
23431 do a better job of analyzing bodies, to
23432 determine whether or not @code{Program_Error}
23433 might be raised, but it certainly
23434 couldn't do a perfect job (that would require solving the halting problem
23435 and is provably impossible), and because this is a warning anyway, it does
23436 not seem worth the effort to do the analysis. Cases in which it
23437 would be relevant are rare.
23439 In practice, warnings of either of the forms given
23440 above will usually correspond to
23441 real errors, and should be examined carefully and eliminated.
23442 In the rare case where a warning is bogus, it can be suppressed by any of
23443 the following methods:
23447 Compile with the @option{-gnatws} switch set
23450 Suppress @code{Elaboration_Check} for the called subprogram
23453 Use pragma @code{Warnings_Off} to turn warnings off for the call
23457 For the internal elaboration check case,
23458 GNAT by default generates the
23459 necessary run-time checks to ensure
23460 that @code{Program_Error} is raised if any
23461 call fails an elaboration check. Of course this can only happen if a
23462 warning has been issued as described above. The use of pragma
23463 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
23464 some of these checks, meaning that it may be possible (but is not
23465 guaranteed) for a program to be able to call a subprogram whose body
23466 is not yet elaborated, without raising a @code{Program_Error} exception.
23468 @node Controlling Elaboration in GNAT - External Calls
23469 @section Controlling Elaboration in GNAT - External Calls
23472 The previous section discussed the case in which the execution of a
23473 particular thread of elaboration code occurred entirely within a
23474 single unit. This is the easy case to handle, because a programmer
23475 has direct and total control over the order of elaboration, and
23476 furthermore, checks need only be generated in cases which are rare
23477 and which the compiler can easily detect.
23478 The situation is more complex when separate compilation is taken into account.
23479 Consider the following:
23481 @smallexample @c ada
23485 function Sqrt (Arg : Float) return Float;
23488 package body Math is
23489 function Sqrt (Arg : Float) return Float is
23498 X : Float := Math.Sqrt (0.5);
23511 where @code{Main} is the main program. When this program is executed, the
23512 elaboration code must first be executed, and one of the jobs of the
23513 binder is to determine the order in which the units of a program are
23514 to be elaborated. In this case we have four units: the spec and body
23516 the spec of @code{Stuff} and the body of @code{Main}).
23517 In what order should the four separate sections of elaboration code
23520 There are some restrictions in the order of elaboration that the binder
23521 can choose. In particular, if unit U has a @code{with}
23522 for a package @code{X}, then you
23523 are assured that the spec of @code{X}
23524 is elaborated before U , but you are
23525 not assured that the body of @code{X}
23526 is elaborated before U.
23527 This means that in the above case, the binder is allowed to choose the
23538 but that's not good, because now the call to @code{Math.Sqrt}
23539 that happens during
23540 the elaboration of the @code{Stuff}
23541 spec happens before the body of @code{Math.Sqrt} is
23542 elaborated, and hence causes @code{Program_Error} exception to be raised.
23543 At first glance, one might say that the binder is misbehaving, because
23544 obviously you want to elaborate the body of something you @code{with}
23546 that is not a general rule that can be followed in all cases. Consider
23548 @smallexample @c ada
23551 package X is @dots{}
23553 package Y is @dots{}
23556 package body Y is @dots{}
23559 package body X is @dots{}
23565 This is a common arrangement, and, apart from the order of elaboration
23566 problems that might arise in connection with elaboration code, this works fine.
23567 A rule that says that you must first elaborate the body of anything you
23568 @code{with} cannot work in this case:
23569 the body of @code{X} @code{with}'s @code{Y},
23570 which means you would have to
23571 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
23573 you have to elaborate the body of @code{X} first, but @dots{} and we have a
23574 loop that cannot be broken.
23576 It is true that the binder can in many cases guess an order of elaboration
23577 that is unlikely to cause a @code{Program_Error}
23578 exception to be raised, and it tries to do so (in the
23579 above example of @code{Math/Stuff/Spec}, the GNAT binder will
23581 elaborate the body of @code{Math} right after its spec, so all will be well).
23583 However, a program that blindly relies on the binder to be helpful can
23584 get into trouble, as we discussed in the previous sections, so
23586 provides a number of facilities for assisting the programmer in
23587 developing programs that are robust with respect to elaboration order.
23589 @node Default Behavior in GNAT - Ensuring Safety
23590 @section Default Behavior in GNAT - Ensuring Safety
23593 The default behavior in GNAT ensures elaboration safety. In its
23594 default mode GNAT implements the
23595 rule we previously described as the right approach. Let's restate it:
23599 @emph{If a unit has elaboration code that can directly or indirectly make a
23600 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
23601 package in a @code{with}'ed unit, then if the @code{with}'ed unit
23602 does not have pragma @code{Pure} or
23603 @code{Preelaborate}, then the client should have an
23604 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
23606 @emph{In the case of instantiating a generic subprogram, it is always
23607 sufficient to have only an @code{Elaborate} pragma for the
23608 @code{with}'ed unit.}
23612 By following this rule a client is assured that calls and instantiations
23613 can be made without risk of an exception.
23615 In this mode GNAT traces all calls that are potentially made from
23616 elaboration code, and puts in any missing implicit @code{Elaborate}
23617 and @code{Elaborate_All} pragmas.
23618 The advantage of this approach is that no elaboration problems
23619 are possible if the binder can find an elaboration order that is
23620 consistent with these implicit @code{Elaborate} and
23621 @code{Elaborate_All} pragmas. The
23622 disadvantage of this approach is that no such order may exist.
23624 If the binder does not generate any diagnostics, then it means that it has
23625 found an elaboration order that is guaranteed to be safe. However, the binder
23626 may still be relying on implicitly generated @code{Elaborate} and
23627 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
23630 If it is important to guarantee portability, then the compilations should
23633 (warn on elaboration problems) switch. This will cause warning messages
23634 to be generated indicating the missing @code{Elaborate} and
23635 @code{Elaborate_All} pragmas.
23636 Consider the following source program:
23638 @smallexample @c ada
23643 m : integer := k.r;
23650 where it is clear that there
23651 should be a pragma @code{Elaborate_All}
23652 for unit @code{k}. An implicit pragma will be generated, and it is
23653 likely that the binder will be able to honor it. However, if you want
23654 to port this program to some other Ada compiler than GNAT.
23655 it is safer to include the pragma explicitly in the source. If this
23656 unit is compiled with the
23658 switch, then the compiler outputs a warning:
23665 3. m : integer := k.r;
23667 >>> warning: call to "r" may raise Program_Error
23668 >>> warning: missing pragma Elaborate_All for "k"
23676 and these warnings can be used as a guide for supplying manually
23677 the missing pragmas. It is usually a bad idea to use this warning
23678 option during development. That's because it will warn you when
23679 you need to put in a pragma, but cannot warn you when it is time
23680 to take it out. So the use of pragma @code{Elaborate_All} may lead to
23681 unnecessary dependencies and even false circularities.
23683 This default mode is more restrictive than the Ada Reference
23684 Manual, and it is possible to construct programs which will compile
23685 using the dynamic model described there, but will run into a
23686 circularity using the safer static model we have described.
23688 Of course any Ada compiler must be able to operate in a mode
23689 consistent with the requirements of the Ada Reference Manual,
23690 and in particular must have the capability of implementing the
23691 standard dynamic model of elaboration with run-time checks.
23693 In GNAT, this standard mode can be achieved either by the use of
23694 the @option{-gnatE} switch on the compiler (@command{gcc} or
23695 @command{gnatmake}) command, or by the use of the configuration pragma:
23697 @smallexample @c ada
23698 pragma Elaboration_Checks (DYNAMIC);
23702 Either approach will cause the unit affected to be compiled using the
23703 standard dynamic run-time elaboration checks described in the Ada
23704 Reference Manual. The static model is generally preferable, since it
23705 is clearly safer to rely on compile and link time checks rather than
23706 run-time checks. However, in the case of legacy code, it may be
23707 difficult to meet the requirements of the static model. This
23708 issue is further discussed in
23709 @ref{What to Do If the Default Elaboration Behavior Fails}.
23711 Note that the static model provides a strict subset of the allowed
23712 behavior and programs of the Ada Reference Manual, so if you do
23713 adhere to the static model and no circularities exist,
23714 then you are assured that your program will
23715 work using the dynamic model, providing that you remove any
23716 pragma Elaborate statements from the source.
23718 @node Treatment of Pragma Elaborate
23719 @section Treatment of Pragma Elaborate
23720 @cindex Pragma Elaborate
23723 The use of @code{pragma Elaborate}
23724 should generally be avoided in Ada 95 and Ada 2005 programs,
23725 since there is no guarantee that transitive calls
23726 will be properly handled. Indeed at one point, this pragma was placed
23727 in Annex J (Obsolescent Features), on the grounds that it is never useful.
23729 Now that's a bit restrictive. In practice, the case in which
23730 @code{pragma Elaborate} is useful is when the caller knows that there
23731 are no transitive calls, or that the called unit contains all necessary
23732 transitive @code{pragma Elaborate} statements, and legacy code often
23733 contains such uses.
23735 Strictly speaking the static mode in GNAT should ignore such pragmas,
23736 since there is no assurance at compile time that the necessary safety
23737 conditions are met. In practice, this would cause GNAT to be incompatible
23738 with correctly written Ada 83 code that had all necessary
23739 @code{pragma Elaborate} statements in place. Consequently, we made the
23740 decision that GNAT in its default mode will believe that if it encounters
23741 a @code{pragma Elaborate} then the programmer knows what they are doing,
23742 and it will trust that no elaboration errors can occur.
23744 The result of this decision is two-fold. First to be safe using the
23745 static mode, you should remove all @code{pragma Elaborate} statements.
23746 Second, when fixing circularities in existing code, you can selectively
23747 use @code{pragma Elaborate} statements to convince the static mode of
23748 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
23751 When using the static mode with @option{-gnatwl}, any use of
23752 @code{pragma Elaborate} will generate a warning about possible
23755 @node Elaboration Issues for Library Tasks
23756 @section Elaboration Issues for Library Tasks
23757 @cindex Library tasks, elaboration issues
23758 @cindex Elaboration of library tasks
23761 In this section we examine special elaboration issues that arise for
23762 programs that declare library level tasks.
23764 Generally the model of execution of an Ada program is that all units are
23765 elaborated, and then execution of the program starts. However, the
23766 declaration of library tasks definitely does not fit this model. The
23767 reason for this is that library tasks start as soon as they are declared
23768 (more precisely, as soon as the statement part of the enclosing package
23769 body is reached), that is to say before elaboration
23770 of the program is complete. This means that if such a task calls a
23771 subprogram, or an entry in another task, the callee may or may not be
23772 elaborated yet, and in the standard
23773 Reference Manual model of dynamic elaboration checks, you can even
23774 get timing dependent Program_Error exceptions, since there can be
23775 a race between the elaboration code and the task code.
23777 The static model of elaboration in GNAT seeks to avoid all such
23778 dynamic behavior, by being conservative, and the conservative
23779 approach in this particular case is to assume that all the code
23780 in a task body is potentially executed at elaboration time if
23781 a task is declared at the library level.
23783 This can definitely result in unexpected circularities. Consider
23784 the following example
23786 @smallexample @c ada
23792 type My_Int is new Integer;
23794 function Ident (M : My_Int) return My_Int;
23798 package body Decls is
23799 task body Lib_Task is
23805 function Ident (M : My_Int) return My_Int is
23813 procedure Put_Val (Arg : Decls.My_Int);
23817 package body Utils is
23818 procedure Put_Val (Arg : Decls.My_Int) is
23820 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23827 Decls.Lib_Task.Start;
23832 If the above example is compiled in the default static elaboration
23833 mode, then a circularity occurs. The circularity comes from the call
23834 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
23835 this call occurs in elaboration code, we need an implicit pragma
23836 @code{Elaborate_All} for @code{Utils}. This means that not only must
23837 the spec and body of @code{Utils} be elaborated before the body
23838 of @code{Decls}, but also the spec and body of any unit that is
23839 @code{with'ed} by the body of @code{Utils} must also be elaborated before
23840 the body of @code{Decls}. This is the transitive implication of
23841 pragma @code{Elaborate_All} and it makes sense, because in general
23842 the body of @code{Put_Val} might have a call to something in a
23843 @code{with'ed} unit.
23845 In this case, the body of Utils (actually its spec) @code{with's}
23846 @code{Decls}. Unfortunately this means that the body of @code{Decls}
23847 must be elaborated before itself, in case there is a call from the
23848 body of @code{Utils}.
23850 Here is the exact chain of events we are worrying about:
23854 In the body of @code{Decls} a call is made from within the body of a library
23855 task to a subprogram in the package @code{Utils}. Since this call may
23856 occur at elaboration time (given that the task is activated at elaboration
23857 time), we have to assume the worst, i.e., that the
23858 call does happen at elaboration time.
23861 This means that the body and spec of @code{Util} must be elaborated before
23862 the body of @code{Decls} so that this call does not cause an access before
23866 Within the body of @code{Util}, specifically within the body of
23867 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
23871 One such @code{with}'ed package is package @code{Decls}, so there
23872 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
23873 In fact there is such a call in this example, but we would have to
23874 assume that there was such a call even if it were not there, since
23875 we are not supposed to write the body of @code{Decls} knowing what
23876 is in the body of @code{Utils}; certainly in the case of the
23877 static elaboration model, the compiler does not know what is in
23878 other bodies and must assume the worst.
23881 This means that the spec and body of @code{Decls} must also be
23882 elaborated before we elaborate the unit containing the call, but
23883 that unit is @code{Decls}! This means that the body of @code{Decls}
23884 must be elaborated before itself, and that's a circularity.
23888 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
23889 the body of @code{Decls} you will get a true Ada Reference Manual
23890 circularity that makes the program illegal.
23892 In practice, we have found that problems with the static model of
23893 elaboration in existing code often arise from library tasks, so
23894 we must address this particular situation.
23896 Note that if we compile and run the program above, using the dynamic model of
23897 elaboration (that is to say use the @option{-gnatE} switch),
23898 then it compiles, binds,
23899 links, and runs, printing the expected result of 2. Therefore in some sense
23900 the circularity here is only apparent, and we need to capture
23901 the properties of this program that distinguish it from other library-level
23902 tasks that have real elaboration problems.
23904 We have four possible answers to this question:
23909 Use the dynamic model of elaboration.
23911 If we use the @option{-gnatE} switch, then as noted above, the program works.
23912 Why is this? If we examine the task body, it is apparent that the task cannot
23914 @code{accept} statement until after elaboration has been completed, because
23915 the corresponding entry call comes from the main program, not earlier.
23916 This is why the dynamic model works here. But that's really giving
23917 up on a precise analysis, and we prefer to take this approach only if we cannot
23919 problem in any other manner. So let us examine two ways to reorganize
23920 the program to avoid the potential elaboration problem.
23923 Split library tasks into separate packages.
23925 Write separate packages, so that library tasks are isolated from
23926 other declarations as much as possible. Let us look at a variation on
23929 @smallexample @c ada
23937 package body Decls1 is
23938 task body Lib_Task is
23946 type My_Int is new Integer;
23947 function Ident (M : My_Int) return My_Int;
23951 package body Decls2 is
23952 function Ident (M : My_Int) return My_Int is
23960 procedure Put_Val (Arg : Decls2.My_Int);
23964 package body Utils is
23965 procedure Put_Val (Arg : Decls2.My_Int) is
23967 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
23974 Decls1.Lib_Task.Start;
23979 All we have done is to split @code{Decls} into two packages, one
23980 containing the library task, and one containing everything else. Now
23981 there is no cycle, and the program compiles, binds, links and executes
23982 using the default static model of elaboration.
23985 Declare separate task types.
23987 A significant part of the problem arises because of the use of the
23988 single task declaration form. This means that the elaboration of
23989 the task type, and the elaboration of the task itself (i.e.@: the
23990 creation of the task) happen at the same time. A good rule
23991 of style in Ada is to always create explicit task types. By
23992 following the additional step of placing task objects in separate
23993 packages from the task type declaration, many elaboration problems
23994 are avoided. Here is another modified example of the example program:
23996 @smallexample @c ada
23998 task type Lib_Task_Type is
24002 type My_Int is new Integer;
24004 function Ident (M : My_Int) return My_Int;
24008 package body Decls is
24009 task body Lib_Task_Type is
24015 function Ident (M : My_Int) return My_Int is
24023 procedure Put_Val (Arg : Decls.My_Int);
24027 package body Utils is
24028 procedure Put_Val (Arg : Decls.My_Int) is
24030 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
24036 Lib_Task : Decls.Lib_Task_Type;
24042 Declst.Lib_Task.Start;
24047 What we have done here is to replace the @code{task} declaration in
24048 package @code{Decls} with a @code{task type} declaration. Then we
24049 introduce a separate package @code{Declst} to contain the actual
24050 task object. This separates the elaboration issues for
24051 the @code{task type}
24052 declaration, which causes no trouble, from the elaboration issues
24053 of the task object, which is also unproblematic, since it is now independent
24054 of the elaboration of @code{Utils}.
24055 This separation of concerns also corresponds to
24056 a generally sound engineering principle of separating declarations
24057 from instances. This version of the program also compiles, binds, links,
24058 and executes, generating the expected output.
24061 Use No_Entry_Calls_In_Elaboration_Code restriction.
24062 @cindex No_Entry_Calls_In_Elaboration_Code
24064 The previous two approaches described how a program can be restructured
24065 to avoid the special problems caused by library task bodies. in practice,
24066 however, such restructuring may be difficult to apply to existing legacy code,
24067 so we must consider solutions that do not require massive rewriting.
24069 Let us consider more carefully why our original sample program works
24070 under the dynamic model of elaboration. The reason is that the code
24071 in the task body blocks immediately on the @code{accept}
24072 statement. Now of course there is nothing to prohibit elaboration
24073 code from making entry calls (for example from another library level task),
24074 so we cannot tell in isolation that
24075 the task will not execute the accept statement during elaboration.
24077 However, in practice it is very unusual to see elaboration code
24078 make any entry calls, and the pattern of tasks starting
24079 at elaboration time and then immediately blocking on @code{accept} or
24080 @code{select} statements is very common. What this means is that
24081 the compiler is being too pessimistic when it analyzes the
24082 whole package body as though it might be executed at elaboration
24085 If we know that the elaboration code contains no entry calls, (a very safe
24086 assumption most of the time, that could almost be made the default
24087 behavior), then we can compile all units of the program under control
24088 of the following configuration pragma:
24091 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
24095 This pragma can be placed in the @file{gnat.adc} file in the usual
24096 manner. If we take our original unmodified program and compile it
24097 in the presence of a @file{gnat.adc} containing the above pragma,
24098 then once again, we can compile, bind, link, and execute, obtaining
24099 the expected result. In the presence of this pragma, the compiler does
24100 not trace calls in a task body, that appear after the first @code{accept}
24101 or @code{select} statement, and therefore does not report a potential
24102 circularity in the original program.
24104 The compiler will check to the extent it can that the above
24105 restriction is not violated, but it is not always possible to do a
24106 complete check at compile time, so it is important to use this
24107 pragma only if the stated restriction is in fact met, that is to say
24108 no task receives an entry call before elaboration of all units is completed.
24112 @node Mixing Elaboration Models
24113 @section Mixing Elaboration Models
24115 So far, we have assumed that the entire program is either compiled
24116 using the dynamic model or static model, ensuring consistency. It
24117 is possible to mix the two models, but rules have to be followed
24118 if this mixing is done to ensure that elaboration checks are not
24121 The basic rule is that @emph{a unit compiled with the static model cannot
24122 be @code{with'ed} by a unit compiled with the dynamic model}. The
24123 reason for this is that in the static model, a unit assumes that
24124 its clients guarantee to use (the equivalent of) pragma
24125 @code{Elaborate_All} so that no elaboration checks are required
24126 in inner subprograms, and this assumption is violated if the
24127 client is compiled with dynamic checks.
24129 The precise rule is as follows. A unit that is compiled with dynamic
24130 checks can only @code{with} a unit that meets at least one of the
24131 following criteria:
24136 The @code{with'ed} unit is itself compiled with dynamic elaboration
24137 checks (that is with the @option{-gnatE} switch.
24140 The @code{with'ed} unit is an internal GNAT implementation unit from
24141 the System, Interfaces, Ada, or GNAT hierarchies.
24144 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
24147 The @code{with'ing} unit (that is the client) has an explicit pragma
24148 @code{Elaborate_All} for the @code{with'ed} unit.
24153 If this rule is violated, that is if a unit with dynamic elaboration
24154 checks @code{with's} a unit that does not meet one of the above four
24155 criteria, then the binder (@code{gnatbind}) will issue a warning
24156 similar to that in the following example:
24159 warning: "x.ads" has dynamic elaboration checks and with's
24160 warning: "y.ads" which has static elaboration checks
24164 These warnings indicate that the rule has been violated, and that as a result
24165 elaboration checks may be missed in the resulting executable file.
24166 This warning may be suppressed using the @option{-ws} binder switch
24167 in the usual manner.
24169 One useful application of this mixing rule is in the case of a subsystem
24170 which does not itself @code{with} units from the remainder of the
24171 application. In this case, the entire subsystem can be compiled with
24172 dynamic checks to resolve a circularity in the subsystem, while
24173 allowing the main application that uses this subsystem to be compiled
24174 using the more reliable default static model.
24176 @node What to Do If the Default Elaboration Behavior Fails
24177 @section What to Do If the Default Elaboration Behavior Fails
24180 If the binder cannot find an acceptable order, it outputs detailed
24181 diagnostics. For example:
24187 error: elaboration circularity detected
24188 info: "proc (body)" must be elaborated before "pack (body)"
24189 info: reason: Elaborate_All probably needed in unit "pack (body)"
24190 info: recompile "pack (body)" with -gnatwl
24191 info: for full details
24192 info: "proc (body)"
24193 info: is needed by its spec:
24194 info: "proc (spec)"
24195 info: which is withed by:
24196 info: "pack (body)"
24197 info: "pack (body)" must be elaborated before "proc (body)"
24198 info: reason: pragma Elaborate in unit "proc (body)"
24204 In this case we have a cycle that the binder cannot break. On the one
24205 hand, there is an explicit pragma Elaborate in @code{proc} for
24206 @code{pack}. This means that the body of @code{pack} must be elaborated
24207 before the body of @code{proc}. On the other hand, there is elaboration
24208 code in @code{pack} that calls a subprogram in @code{proc}. This means
24209 that for maximum safety, there should really be a pragma
24210 Elaborate_All in @code{pack} for @code{proc} which would require that
24211 the body of @code{proc} be elaborated before the body of
24212 @code{pack}. Clearly both requirements cannot be satisfied.
24213 Faced with a circularity of this kind, you have three different options.
24216 @item Fix the program
24217 The most desirable option from the point of view of long-term maintenance
24218 is to rearrange the program so that the elaboration problems are avoided.
24219 One useful technique is to place the elaboration code into separate
24220 child packages. Another is to move some of the initialization code to
24221 explicitly called subprograms, where the program controls the order
24222 of initialization explicitly. Although this is the most desirable option,
24223 it may be impractical and involve too much modification, especially in
24224 the case of complex legacy code.
24226 @item Perform dynamic checks
24227 If the compilations are done using the
24229 (dynamic elaboration check) switch, then GNAT behaves in a quite different
24230 manner. Dynamic checks are generated for all calls that could possibly result
24231 in raising an exception. With this switch, the compiler does not generate
24232 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
24233 exactly as specified in the @cite{Ada Reference Manual}.
24234 The binder will generate
24235 an executable program that may or may not raise @code{Program_Error}, and then
24236 it is the programmer's job to ensure that it does not raise an exception. Note
24237 that it is important to compile all units with the switch, it cannot be used
24240 @item Suppress checks
24241 The drawback of dynamic checks is that they generate a
24242 significant overhead at run time, both in space and time. If you
24243 are absolutely sure that your program cannot raise any elaboration
24244 exceptions, and you still want to use the dynamic elaboration model,
24245 then you can use the configuration pragma
24246 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
24247 example this pragma could be placed in the @file{gnat.adc} file.
24249 @item Suppress checks selectively
24250 When you know that certain calls or instantiations in elaboration code cannot
24251 possibly lead to an elaboration error, and the binder nevertheless complains
24252 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
24253 elaboration circularities, it is possible to remove those warnings locally and
24254 obtain a program that will bind. Clearly this can be unsafe, and it is the
24255 responsibility of the programmer to make sure that the resulting program has no
24256 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
24257 used with different granularity to suppress warnings and break elaboration
24262 Place the pragma that names the called subprogram in the declarative part
24263 that contains the call.
24266 Place the pragma in the declarative part, without naming an entity. This
24267 disables warnings on all calls in the corresponding declarative region.
24270 Place the pragma in the package spec that declares the called subprogram,
24271 and name the subprogram. This disables warnings on all elaboration calls to
24275 Place the pragma in the package spec that declares the called subprogram,
24276 without naming any entity. This disables warnings on all elaboration calls to
24277 all subprograms declared in this spec.
24279 @item Use Pragma Elaborate
24280 As previously described in section @xref{Treatment of Pragma Elaborate},
24281 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
24282 that no elaboration checks are required on calls to the designated unit.
24283 There may be cases in which the caller knows that no transitive calls
24284 can occur, so that a @code{pragma Elaborate} will be sufficient in a
24285 case where @code{pragma Elaborate_All} would cause a circularity.
24289 These five cases are listed in order of decreasing safety, and therefore
24290 require increasing programmer care in their application. Consider the
24293 @smallexample @c adanocomment
24295 function F1 return Integer;
24300 function F2 return Integer;
24301 function Pure (x : integer) return integer;
24302 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
24303 -- pragma Suppress (Elaboration_Check); -- (4)
24307 package body Pack1 is
24308 function F1 return Integer is
24312 Val : integer := Pack2.Pure (11); -- Elab. call (1)
24315 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
24316 -- pragma Suppress(Elaboration_Check); -- (2)
24318 X1 := Pack2.F2 + 1; -- Elab. call (2)
24323 package body Pack2 is
24324 function F2 return Integer is
24328 function Pure (x : integer) return integer is
24330 return x ** 3 - 3 * x;
24334 with Pack1, Ada.Text_IO;
24337 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
24340 In the absence of any pragmas, an attempt to bind this program produces
24341 the following diagnostics:
24347 error: elaboration circularity detected
24348 info: "pack1 (body)" must be elaborated before "pack1 (body)"
24349 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
24350 info: recompile "pack1 (body)" with -gnatwl for full details
24351 info: "pack1 (body)"
24352 info: must be elaborated along with its spec:
24353 info: "pack1 (spec)"
24354 info: which is withed by:
24355 info: "pack2 (body)"
24356 info: which must be elaborated along with its spec:
24357 info: "pack2 (spec)"
24358 info: which is withed by:
24359 info: "pack1 (body)"
24362 The sources of the circularity are the two calls to @code{Pack2.Pure} and
24363 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
24364 F2 is safe, even though F2 calls F1, because the call appears after the
24365 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
24366 remove the warning on the call. It is also possible to use pragma (2)
24367 because there are no other potentially unsafe calls in the block.
24370 The call to @code{Pure} is safe because this function does not depend on the
24371 state of @code{Pack2}. Therefore any call to this function is safe, and it
24372 is correct to place pragma (3) in the corresponding package spec.
24375 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
24376 warnings on all calls to functions declared therein. Note that this is not
24377 necessarily safe, and requires more detailed examination of the subprogram
24378 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
24379 be already elaborated.
24383 It is hard to generalize on which of these four approaches should be
24384 taken. Obviously if it is possible to fix the program so that the default
24385 treatment works, this is preferable, but this may not always be practical.
24386 It is certainly simple enough to use
24388 but the danger in this case is that, even if the GNAT binder
24389 finds a correct elaboration order, it may not always do so,
24390 and certainly a binder from another Ada compiler might not. A
24391 combination of testing and analysis (for which the warnings generated
24394 switch can be useful) must be used to ensure that the program is free
24395 of errors. One switch that is useful in this testing is the
24396 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
24399 Normally the binder tries to find an order that has the best chance
24400 of avoiding elaboration problems. However, if this switch is used, the binder
24401 plays a devil's advocate role, and tries to choose the order that
24402 has the best chance of failing. If your program works even with this
24403 switch, then it has a better chance of being error free, but this is still
24406 For an example of this approach in action, consider the C-tests (executable
24407 tests) from the ACVC suite. If these are compiled and run with the default
24408 treatment, then all but one of them succeed without generating any error
24409 diagnostics from the binder. However, there is one test that fails, and
24410 this is not surprising, because the whole point of this test is to ensure
24411 that the compiler can handle cases where it is impossible to determine
24412 a correct order statically, and it checks that an exception is indeed
24413 raised at run time.
24415 This one test must be compiled and run using the
24417 switch, and then it passes. Alternatively, the entire suite can
24418 be run using this switch. It is never wrong to run with the dynamic
24419 elaboration switch if your code is correct, and we assume that the
24420 C-tests are indeed correct (it is less efficient, but efficiency is
24421 not a factor in running the ACVC tests.)
24423 @node Elaboration for Access-to-Subprogram Values
24424 @section Elaboration for Access-to-Subprogram Values
24425 @cindex Access-to-subprogram
24428 Access-to-subprogram types (introduced in Ada 95) complicate
24429 the handling of elaboration. The trouble is that it becomes
24430 impossible to tell at compile time which procedure
24431 is being called. This means that it is not possible for the binder
24432 to analyze the elaboration requirements in this case.
24434 If at the point at which the access value is created
24435 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
24436 the body of the subprogram is
24437 known to have been elaborated, then the access value is safe, and its use
24438 does not require a check. This may be achieved by appropriate arrangement
24439 of the order of declarations if the subprogram is in the current unit,
24440 or, if the subprogram is in another unit, by using pragma
24441 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
24442 on the referenced unit.
24444 If the referenced body is not known to have been elaborated at the point
24445 the access value is created, then any use of the access value must do a
24446 dynamic check, and this dynamic check will fail and raise a
24447 @code{Program_Error} exception if the body has not been elaborated yet.
24448 GNAT will generate the necessary checks, and in addition, if the
24450 switch is set, will generate warnings that such checks are required.
24452 The use of dynamic dispatching for tagged types similarly generates
24453 a requirement for dynamic checks, and premature calls to any primitive
24454 operation of a tagged type before the body of the operation has been
24455 elaborated, will result in the raising of @code{Program_Error}.
24457 @node Summary of Procedures for Elaboration Control
24458 @section Summary of Procedures for Elaboration Control
24459 @cindex Elaboration control
24462 First, compile your program with the default options, using none of
24463 the special elaboration control switches. If the binder successfully
24464 binds your program, then you can be confident that, apart from issues
24465 raised by the use of access-to-subprogram types and dynamic dispatching,
24466 the program is free of elaboration errors. If it is important that the
24467 program be portable, then use the
24469 switch to generate warnings about missing @code{Elaborate} or
24470 @code{Elaborate_All} pragmas, and supply the missing pragmas.
24472 If the program fails to bind using the default static elaboration
24473 handling, then you can fix the program to eliminate the binder
24474 message, or recompile the entire program with the
24475 @option{-gnatE} switch to generate dynamic elaboration checks,
24476 and, if you are sure there really are no elaboration problems,
24477 use a global pragma @code{Suppress (Elaboration_Check)}.
24479 @node Other Elaboration Order Considerations
24480 @section Other Elaboration Order Considerations
24482 This section has been entirely concerned with the issue of finding a valid
24483 elaboration order, as defined by the Ada Reference Manual. In a case
24484 where several elaboration orders are valid, the task is to find one
24485 of the possible valid elaboration orders (and the static model in GNAT
24486 will ensure that this is achieved).
24488 The purpose of the elaboration rules in the Ada Reference Manual is to
24489 make sure that no entity is accessed before it has been elaborated. For
24490 a subprogram, this means that the spec and body must have been elaborated
24491 before the subprogram is called. For an object, this means that the object
24492 must have been elaborated before its value is read or written. A violation
24493 of either of these two requirements is an access before elaboration order,
24494 and this section has been all about avoiding such errors.
24496 In the case where more than one order of elaboration is possible, in the
24497 sense that access before elaboration errors are avoided, then any one of
24498 the orders is ``correct'' in the sense that it meets the requirements of
24499 the Ada Reference Manual, and no such error occurs.
24501 However, it may be the case for a given program, that there are
24502 constraints on the order of elaboration that come not from consideration
24503 of avoiding elaboration errors, but rather from extra-lingual logic
24504 requirements. Consider this example:
24506 @smallexample @c ada
24507 with Init_Constants;
24508 package Constants is
24513 package Init_Constants is
24514 procedure P; -- require a body
24515 end Init_Constants;
24518 package body Init_Constants is
24519 procedure P is begin null; end;
24523 end Init_Constants;
24527 Z : Integer := Constants.X + Constants.Y;
24531 with Text_IO; use Text_IO;
24534 Put_Line (Calc.Z'Img);
24539 In this example, there is more than one valid order of elaboration. For
24540 example both the following are correct orders:
24543 Init_Constants spec
24546 Init_Constants body
24551 Init_Constants spec
24552 Init_Constants body
24559 There is no language rule to prefer one or the other, both are correct
24560 from an order of elaboration point of view. But the programmatic effects
24561 of the two orders are very different. In the first, the elaboration routine
24562 of @code{Calc} initializes @code{Z} to zero, and then the main program
24563 runs with this value of zero. But in the second order, the elaboration
24564 routine of @code{Calc} runs after the body of Init_Constants has set
24565 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
24568 One could perhaps by applying pretty clever non-artificial intelligence
24569 to the situation guess that it is more likely that the second order of
24570 elaboration is the one desired, but there is no formal linguistic reason
24571 to prefer one over the other. In fact in this particular case, GNAT will
24572 prefer the second order, because of the rule that bodies are elaborated
24573 as soon as possible, but it's just luck that this is what was wanted
24574 (if indeed the second order was preferred).
24576 If the program cares about the order of elaboration routines in a case like
24577 this, it is important to specify the order required. In this particular
24578 case, that could have been achieved by adding to the spec of Calc:
24580 @smallexample @c ada
24581 pragma Elaborate_All (Constants);
24585 which requires that the body (if any) and spec of @code{Constants},
24586 as well as the body and spec of any unit @code{with}'ed by
24587 @code{Constants} be elaborated before @code{Calc} is elaborated.
24589 Clearly no automatic method can always guess which alternative you require,
24590 and if you are working with legacy code that had constraints of this kind
24591 which were not properly specified by adding @code{Elaborate} or
24592 @code{Elaborate_All} pragmas, then indeed it is possible that two different
24593 compilers can choose different orders.
24595 However, GNAT does attempt to diagnose the common situation where there
24596 are uninitialized variables in the visible part of a package spec, and the
24597 corresponding package body has an elaboration block that directly or
24598 indirectly initialized one or more of these variables. This is the situation
24599 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
24600 a warning that suggests this addition if it detects this situation.
24602 The @code{gnatbind}
24603 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
24604 out problems. This switch causes bodies to be elaborated as late as possible
24605 instead of as early as possible. In the example above, it would have forced
24606 the choice of the first elaboration order. If you get different results
24607 when using this switch, and particularly if one set of results is right,
24608 and one is wrong as far as you are concerned, it shows that you have some
24609 missing @code{Elaborate} pragmas. For the example above, we have the
24613 gnatmake -f -q main
24616 gnatmake -f -q main -bargs -p
24622 It is of course quite unlikely that both these results are correct, so
24623 it is up to you in a case like this to investigate the source of the
24624 difference, by looking at the two elaboration orders that are chosen,
24625 and figuring out which is correct, and then adding the necessary
24626 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
24630 @c *******************************
24631 @node Conditional Compilation
24632 @appendix Conditional Compilation
24633 @c *******************************
24634 @cindex Conditional compilation
24637 It is often necessary to arrange for a single source program
24638 to serve multiple purposes, where it is compiled in different
24639 ways to achieve these different goals. Some examples of the
24640 need for this feature are
24643 @item Adapting a program to a different hardware environment
24644 @item Adapting a program to a different target architecture
24645 @item Turning debugging features on and off
24646 @item Arranging for a program to compile with different compilers
24650 In C, or C++, the typical approach would be to use the preprocessor
24651 that is defined as part of the language. The Ada language does not
24652 contain such a feature. This is not an oversight, but rather a very
24653 deliberate design decision, based on the experience that overuse of
24654 the preprocessing features in C and C++ can result in programs that
24655 are extremely difficult to maintain. For example, if we have ten
24656 switches that can be on or off, this means that there are a thousand
24657 separate programs, any one of which might not even be syntactically
24658 correct, and even if syntactically correct, the resulting program
24659 might not work correctly. Testing all combinations can quickly become
24662 Nevertheless, the need to tailor programs certainly exists, and in
24663 this Appendix we will discuss how this can
24664 be achieved using Ada in general, and GNAT in particular.
24667 * Use of Boolean Constants::
24668 * Debugging - A Special Case::
24669 * Conditionalizing Declarations::
24670 * Use of Alternative Implementations::
24674 @node Use of Boolean Constants
24675 @section Use of Boolean Constants
24678 In the case where the difference is simply which code
24679 sequence is executed, the cleanest solution is to use Boolean
24680 constants to control which code is executed.
24682 @smallexample @c ada
24684 FP_Initialize_Required : constant Boolean := True;
24686 if FP_Initialize_Required then
24693 Not only will the code inside the @code{if} statement not be executed if
24694 the constant Boolean is @code{False}, but it will also be completely
24695 deleted from the program.
24696 However, the code is only deleted after the @code{if} statement
24697 has been checked for syntactic and semantic correctness.
24698 (In contrast, with preprocessors the code is deleted before the
24699 compiler ever gets to see it, so it is not checked until the switch
24701 @cindex Preprocessors (contrasted with conditional compilation)
24703 Typically the Boolean constants will be in a separate package,
24706 @smallexample @c ada
24709 FP_Initialize_Required : constant Boolean := True;
24710 Reset_Available : constant Boolean := False;
24717 The @code{Config} package exists in multiple forms for the various targets,
24718 with an appropriate script selecting the version of @code{Config} needed.
24719 Then any other unit requiring conditional compilation can do a @code{with}
24720 of @code{Config} to make the constants visible.
24723 @node Debugging - A Special Case
24724 @section Debugging - A Special Case
24727 A common use of conditional code is to execute statements (for example
24728 dynamic checks, or output of intermediate results) under control of a
24729 debug switch, so that the debugging behavior can be turned on and off.
24730 This can be done using a Boolean constant to control whether the code
24733 @smallexample @c ada
24736 Put_Line ("got to the first stage!");
24744 @smallexample @c ada
24746 if Debugging and then Temperature > 999.0 then
24747 raise Temperature_Crazy;
24753 Since this is a common case, there are special features to deal with
24754 this in a convenient manner. For the case of tests, Ada 2005 has added
24755 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
24756 @cindex pragma @code{Assert}
24757 on the @code{Assert} pragma that has always been available in GNAT, so this
24758 feature may be used with GNAT even if you are not using Ada 2005 features.
24759 The use of pragma @code{Assert} is described in
24760 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
24761 example, the last test could be written:
24763 @smallexample @c ada
24764 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
24770 @smallexample @c ada
24771 pragma Assert (Temperature <= 999.0);
24775 In both cases, if assertions are active and the temperature is excessive,
24776 the exception @code{Assert_Failure} will be raised, with the given string in
24777 the first case or a string indicating the location of the pragma in the second
24778 case used as the exception message.
24780 You can turn assertions on and off by using the @code{Assertion_Policy}
24782 @cindex pragma @code{Assertion_Policy}
24783 This is an Ada 2005 pragma which is implemented in all modes by
24784 GNAT, but only in the latest versions of GNAT which include Ada 2005
24785 capability. Alternatively, you can use the @option{-gnata} switch
24786 @cindex @option{-gnata} switch
24787 to enable assertions from the command line (this is recognized by all versions
24790 For the example above with the @code{Put_Line}, the GNAT-specific pragma
24791 @code{Debug} can be used:
24792 @cindex pragma @code{Debug}
24794 @smallexample @c ada
24795 pragma Debug (Put_Line ("got to the first stage!"));
24799 If debug pragmas are enabled, the argument, which must be of the form of
24800 a procedure call, is executed (in this case, @code{Put_Line} will be called).
24801 Only one call can be present, but of course a special debugging procedure
24802 containing any code you like can be included in the program and then
24803 called in a pragma @code{Debug} argument as needed.
24805 One advantage of pragma @code{Debug} over the @code{if Debugging then}
24806 construct is that pragma @code{Debug} can appear in declarative contexts,
24807 such as at the very beginning of a procedure, before local declarations have
24810 Debug pragmas are enabled using either the @option{-gnata} switch that also
24811 controls assertions, or with a separate Debug_Policy pragma.
24812 @cindex pragma @code{Debug_Policy}
24813 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
24814 in Ada 95 and Ada 83 programs as well), and is analogous to
24815 pragma @code{Assertion_Policy} to control assertions.
24817 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
24818 and thus they can appear in @file{gnat.adc} if you are not using a
24819 project file, or in the file designated to contain configuration pragmas
24821 They then apply to all subsequent compilations. In practice the use of
24822 the @option{-gnata} switch is often the most convenient method of controlling
24823 the status of these pragmas.
24825 Note that a pragma is not a statement, so in contexts where a statement
24826 sequence is required, you can't just write a pragma on its own. You have
24827 to add a @code{null} statement.
24829 @smallexample @c ada
24832 @dots{} -- some statements
24834 pragma Assert (Num_Cases < 10);
24841 @node Conditionalizing Declarations
24842 @section Conditionalizing Declarations
24845 In some cases, it may be necessary to conditionalize declarations to meet
24846 different requirements. For example we might want a bit string whose length
24847 is set to meet some hardware message requirement.
24849 In some cases, it may be possible to do this using declare blocks controlled
24850 by conditional constants:
24852 @smallexample @c ada
24854 if Small_Machine then
24856 X : Bit_String (1 .. 10);
24862 X : Large_Bit_String (1 .. 1000);
24871 Note that in this approach, both declarations are analyzed by the
24872 compiler so this can only be used where both declarations are legal,
24873 even though one of them will not be used.
24875 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
24876 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
24877 that are parameterized by these constants. For example
24879 @smallexample @c ada
24882 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
24888 If @code{Bits_Per_Word} is set to 32, this generates either
24890 @smallexample @c ada
24893 Field1 at 0 range 0 .. 32;
24899 for the big endian case, or
24901 @smallexample @c ada
24904 Field1 at 0 range 10 .. 32;
24910 for the little endian case. Since a powerful subset of Ada expression
24911 notation is usable for creating static constants, clever use of this
24912 feature can often solve quite difficult problems in conditionalizing
24913 compilation (note incidentally that in Ada 95, the little endian
24914 constant was introduced as @code{System.Default_Bit_Order}, so you do not
24915 need to define this one yourself).
24918 @node Use of Alternative Implementations
24919 @section Use of Alternative Implementations
24922 In some cases, none of the approaches described above are adequate. This
24923 can occur for example if the set of declarations required is radically
24924 different for two different configurations.
24926 In this situation, the official Ada way of dealing with conditionalizing
24927 such code is to write separate units for the different cases. As long as
24928 this does not result in excessive duplication of code, this can be done
24929 without creating maintenance problems. The approach is to share common
24930 code as far as possible, and then isolate the code and declarations
24931 that are different. Subunits are often a convenient method for breaking
24932 out a piece of a unit that is to be conditionalized, with separate files
24933 for different versions of the subunit for different targets, where the
24934 build script selects the right one to give to the compiler.
24935 @cindex Subunits (and conditional compilation)
24937 As an example, consider a situation where a new feature in Ada 2005
24938 allows something to be done in a really nice way. But your code must be able
24939 to compile with an Ada 95 compiler. Conceptually you want to say:
24941 @smallexample @c ada
24944 @dots{} neat Ada 2005 code
24946 @dots{} not quite as neat Ada 95 code
24952 where @code{Ada_2005} is a Boolean constant.
24954 But this won't work when @code{Ada_2005} is set to @code{False},
24955 since the @code{then} clause will be illegal for an Ada 95 compiler.
24956 (Recall that although such unreachable code would eventually be deleted
24957 by the compiler, it still needs to be legal. If it uses features
24958 introduced in Ada 2005, it will be illegal in Ada 95.)
24960 So instead we write
24962 @smallexample @c ada
24963 procedure Insert is separate;
24967 Then we have two files for the subunit @code{Insert}, with the two sets of
24969 If the package containing this is called @code{File_Queries}, then we might
24973 @item @file{file_queries-insert-2005.adb}
24974 @item @file{file_queries-insert-95.adb}
24978 and the build script renames the appropriate file to
24981 file_queries-insert.adb
24985 and then carries out the compilation.
24987 This can also be done with project files' naming schemes. For example:
24989 @smallexample @c project
24990 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
24994 Note also that with project files it is desirable to use a different extension
24995 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
24996 conflict may arise through another commonly used feature: to declare as part
24997 of the project a set of directories containing all the sources obeying the
24998 default naming scheme.
25000 The use of alternative units is certainly feasible in all situations,
25001 and for example the Ada part of the GNAT run-time is conditionalized
25002 based on the target architecture using this approach. As a specific example,
25003 consider the implementation of the AST feature in VMS. There is one
25011 which is the same for all architectures, and three bodies:
25015 used for all non-VMS operating systems
25016 @item s-asthan-vms-alpha.adb
25017 used for VMS on the Alpha
25018 @item s-asthan-vms-ia64.adb
25019 used for VMS on the ia64
25023 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
25024 this operating system feature is not available, and the two remaining
25025 versions interface with the corresponding versions of VMS to provide
25026 VMS-compatible AST handling. The GNAT build script knows the architecture
25027 and operating system, and automatically selects the right version,
25028 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
25030 Another style for arranging alternative implementations is through Ada's
25031 access-to-subprogram facility.
25032 In case some functionality is to be conditionally included,
25033 you can declare an access-to-procedure variable @code{Ref} that is initialized
25034 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
25036 In some library package, set @code{Ref} to @code{Proc'Access} for some
25037 procedure @code{Proc} that performs the relevant processing.
25038 The initialization only occurs if the library package is included in the
25040 The same idea can also be implemented using tagged types and dispatching
25044 @node Preprocessing
25045 @section Preprocessing
25046 @cindex Preprocessing
25049 Although it is quite possible to conditionalize code without the use of
25050 C-style preprocessing, as described earlier in this section, it is
25051 nevertheless convenient in some cases to use the C approach. Moreover,
25052 older Ada compilers have often provided some preprocessing capability,
25053 so legacy code may depend on this approach, even though it is not
25056 To accommodate such use, GNAT provides a preprocessor (modeled to a large
25057 extent on the various preprocessors that have been used
25058 with legacy code on other compilers, to enable easier transition).
25060 The preprocessor may be used in two separate modes. It can be used quite
25061 separately from the compiler, to generate a separate output source file
25062 that is then fed to the compiler as a separate step. This is the
25063 @code{gnatprep} utility, whose use is fully described in
25064 @ref{Preprocessing Using gnatprep}.
25065 @cindex @code{gnatprep}
25067 The preprocessing language allows such constructs as
25071 #if DEBUG or PRIORITY > 4 then
25072 bunch of declarations
25074 completely different bunch of declarations
25080 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
25081 defined either on the command line or in a separate file.
25083 The other way of running the preprocessor is even closer to the C style and
25084 often more convenient. In this approach the preprocessing is integrated into
25085 the compilation process. The compiler is fed the preprocessor input which
25086 includes @code{#if} lines etc, and then the compiler carries out the
25087 preprocessing internally and processes the resulting output.
25088 For more details on this approach, see @ref{Integrated Preprocessing}.
25091 @c *******************************
25092 @node Inline Assembler
25093 @appendix Inline Assembler
25094 @c *******************************
25097 If you need to write low-level software that interacts directly
25098 with the hardware, Ada provides two ways to incorporate assembly
25099 language code into your program. First, you can import and invoke
25100 external routines written in assembly language, an Ada feature fully
25101 supported by GNAT@. However, for small sections of code it may be simpler
25102 or more efficient to include assembly language statements directly
25103 in your Ada source program, using the facilities of the implementation-defined
25104 package @code{System.Machine_Code}, which incorporates the gcc
25105 Inline Assembler. The Inline Assembler approach offers a number of advantages,
25106 including the following:
25109 @item No need to use non-Ada tools
25110 @item Consistent interface over different targets
25111 @item Automatic usage of the proper calling conventions
25112 @item Access to Ada constants and variables
25113 @item Definition of intrinsic routines
25114 @item Possibility of inlining a subprogram comprising assembler code
25115 @item Code optimizer can take Inline Assembler code into account
25118 This chapter presents a series of examples to show you how to use
25119 the Inline Assembler. Although it focuses on the Intel x86,
25120 the general approach applies also to other processors.
25121 It is assumed that you are familiar with Ada
25122 and with assembly language programming.
25125 * Basic Assembler Syntax::
25126 * A Simple Example of Inline Assembler::
25127 * Output Variables in Inline Assembler::
25128 * Input Variables in Inline Assembler::
25129 * Inlining Inline Assembler Code::
25130 * Other Asm Functionality::
25133 @c ---------------------------------------------------------------------------
25134 @node Basic Assembler Syntax
25135 @section Basic Assembler Syntax
25138 The assembler used by GNAT and gcc is based not on the Intel assembly
25139 language, but rather on a language that descends from the AT&T Unix
25140 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
25141 The following table summarizes the main features of @emph{as} syntax
25142 and points out the differences from the Intel conventions.
25143 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
25144 pre-processor) documentation for further information.
25147 @item Register names
25148 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
25150 Intel: No extra punctuation; for example @code{eax}
25152 @item Immediate operand
25153 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
25155 Intel: No extra punctuation; for example @code{4}
25158 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
25160 Intel: No extra punctuation; for example @code{loc}
25162 @item Memory contents
25163 gcc / @emph{as}: No extra punctuation; for example @code{loc}
25165 Intel: Square brackets; for example @code{[loc]}
25167 @item Register contents
25168 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
25170 Intel: Square brackets; for example @code{[eax]}
25172 @item Hexadecimal numbers
25173 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
25175 Intel: Trailing ``h''; for example @code{A0h}
25178 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
25181 Intel: Implicit, deduced by assembler; for example @code{mov}
25183 @item Instruction repetition
25184 gcc / @emph{as}: Split into two lines; for example
25190 Intel: Keep on one line; for example @code{rep stosl}
25192 @item Order of operands
25193 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
25195 Intel: Destination first; for example @code{mov eax, 4}
25198 @c ---------------------------------------------------------------------------
25199 @node A Simple Example of Inline Assembler
25200 @section A Simple Example of Inline Assembler
25203 The following example will generate a single assembly language statement,
25204 @code{nop}, which does nothing. Despite its lack of run-time effect,
25205 the example will be useful in illustrating the basics of
25206 the Inline Assembler facility.
25208 @smallexample @c ada
25210 with System.Machine_Code; use System.Machine_Code;
25211 procedure Nothing is
25218 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
25219 here it takes one parameter, a @emph{template string} that must be a static
25220 expression and that will form the generated instruction.
25221 @code{Asm} may be regarded as a compile-time procedure that parses
25222 the template string and additional parameters (none here),
25223 from which it generates a sequence of assembly language instructions.
25225 The examples in this chapter will illustrate several of the forms
25226 for invoking @code{Asm}; a complete specification of the syntax
25227 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
25230 Under the standard GNAT conventions, the @code{Nothing} procedure
25231 should be in a file named @file{nothing.adb}.
25232 You can build the executable in the usual way:
25236 However, the interesting aspect of this example is not its run-time behavior
25237 but rather the generated assembly code.
25238 To see this output, invoke the compiler as follows:
25240 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
25242 where the options are:
25246 compile only (no bind or link)
25248 generate assembler listing
25249 @item -fomit-frame-pointer
25250 do not set up separate stack frames
25252 do not add runtime checks
25255 This gives a human-readable assembler version of the code. The resulting
25256 file will have the same name as the Ada source file, but with a @code{.s}
25257 extension. In our example, the file @file{nothing.s} has the following
25262 .file "nothing.adb"
25264 ___gnu_compiled_ada:
25267 .globl __ada_nothing
25279 The assembly code you included is clearly indicated by
25280 the compiler, between the @code{#APP} and @code{#NO_APP}
25281 delimiters. The character before the 'APP' and 'NOAPP'
25282 can differ on different targets. For example, GNU/Linux uses '#APP' while
25283 on NT you will see '/APP'.
25285 If you make a mistake in your assembler code (such as using the
25286 wrong size modifier, or using a wrong operand for the instruction) GNAT
25287 will report this error in a temporary file, which will be deleted when
25288 the compilation is finished. Generating an assembler file will help
25289 in such cases, since you can assemble this file separately using the
25290 @emph{as} assembler that comes with gcc.
25292 Assembling the file using the command
25295 as @file{nothing.s}
25298 will give you error messages whose lines correspond to the assembler
25299 input file, so you can easily find and correct any mistakes you made.
25300 If there are no errors, @emph{as} will generate an object file
25301 @file{nothing.out}.
25303 @c ---------------------------------------------------------------------------
25304 @node Output Variables in Inline Assembler
25305 @section Output Variables in Inline Assembler
25308 The examples in this section, showing how to access the processor flags,
25309 illustrate how to specify the destination operands for assembly language
25312 @smallexample @c ada
25314 with Interfaces; use Interfaces;
25315 with Ada.Text_IO; use Ada.Text_IO;
25316 with System.Machine_Code; use System.Machine_Code;
25317 procedure Get_Flags is
25318 Flags : Unsigned_32;
25321 Asm ("pushfl" & LF & HT & -- push flags on stack
25322 "popl %%eax" & LF & HT & -- load eax with flags
25323 "movl %%eax, %0", -- store flags in variable
25324 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25325 Put_Line ("Flags register:" & Flags'Img);
25330 In order to have a nicely aligned assembly listing, we have separated
25331 multiple assembler statements in the Asm template string with linefeed
25332 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
25333 The resulting section of the assembly output file is:
25340 movl %eax, -40(%ebp)
25345 It would have been legal to write the Asm invocation as:
25348 Asm ("pushfl popl %%eax movl %%eax, %0")
25351 but in the generated assembler file, this would come out as:
25355 pushfl popl %eax movl %eax, -40(%ebp)
25359 which is not so convenient for the human reader.
25361 We use Ada comments
25362 at the end of each line to explain what the assembler instructions
25363 actually do. This is a useful convention.
25365 When writing Inline Assembler instructions, you need to precede each register
25366 and variable name with a percent sign. Since the assembler already requires
25367 a percent sign at the beginning of a register name, you need two consecutive
25368 percent signs for such names in the Asm template string, thus @code{%%eax}.
25369 In the generated assembly code, one of the percent signs will be stripped off.
25371 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
25372 variables: operands you later define using @code{Input} or @code{Output}
25373 parameters to @code{Asm}.
25374 An output variable is illustrated in
25375 the third statement in the Asm template string:
25379 The intent is to store the contents of the eax register in a variable that can
25380 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
25381 necessarily work, since the compiler might optimize by using a register
25382 to hold Flags, and the expansion of the @code{movl} instruction would not be
25383 aware of this optimization. The solution is not to store the result directly
25384 but rather to advise the compiler to choose the correct operand form;
25385 that is the purpose of the @code{%0} output variable.
25387 Information about the output variable is supplied in the @code{Outputs}
25388 parameter to @code{Asm}:
25390 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25393 The output is defined by the @code{Asm_Output} attribute of the target type;
25394 the general format is
25396 Type'Asm_Output (constraint_string, variable_name)
25399 The constraint string directs the compiler how
25400 to store/access the associated variable. In the example
25402 Unsigned_32'Asm_Output ("=m", Flags);
25404 the @code{"m"} (memory) constraint tells the compiler that the variable
25405 @code{Flags} should be stored in a memory variable, thus preventing
25406 the optimizer from keeping it in a register. In contrast,
25408 Unsigned_32'Asm_Output ("=r", Flags);
25410 uses the @code{"r"} (register) constraint, telling the compiler to
25411 store the variable in a register.
25413 If the constraint is preceded by the equal character (@strong{=}), it tells
25414 the compiler that the variable will be used to store data into it.
25416 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
25417 allowing the optimizer to choose whatever it deems best.
25419 There are a fairly large number of constraints, but the ones that are
25420 most useful (for the Intel x86 processor) are the following:
25426 global (i.e.@: can be stored anywhere)
25444 use one of eax, ebx, ecx or edx
25446 use one of eax, ebx, ecx, edx, esi or edi
25449 The full set of constraints is described in the gcc and @emph{as}
25450 documentation; note that it is possible to combine certain constraints
25451 in one constraint string.
25453 You specify the association of an output variable with an assembler operand
25454 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
25456 @smallexample @c ada
25458 Asm ("pushfl" & LF & HT & -- push flags on stack
25459 "popl %%eax" & LF & HT & -- load eax with flags
25460 "movl %%eax, %0", -- store flags in variable
25461 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25465 @code{%0} will be replaced in the expanded code by the appropriate operand,
25467 the compiler decided for the @code{Flags} variable.
25469 In general, you may have any number of output variables:
25472 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
25474 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
25475 of @code{Asm_Output} attributes
25479 @smallexample @c ada
25481 Asm ("movl %%eax, %0" & LF & HT &
25482 "movl %%ebx, %1" & LF & HT &
25484 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
25485 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
25486 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
25490 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
25491 in the Ada program.
25493 As a variation on the @code{Get_Flags} example, we can use the constraints
25494 string to direct the compiler to store the eax register into the @code{Flags}
25495 variable, instead of including the store instruction explicitly in the
25496 @code{Asm} template string:
25498 @smallexample @c ada
25500 with Interfaces; use Interfaces;
25501 with Ada.Text_IO; use Ada.Text_IO;
25502 with System.Machine_Code; use System.Machine_Code;
25503 procedure Get_Flags_2 is
25504 Flags : Unsigned_32;
25507 Asm ("pushfl" & LF & HT & -- push flags on stack
25508 "popl %%eax", -- save flags in eax
25509 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
25510 Put_Line ("Flags register:" & Flags'Img);
25516 The @code{"a"} constraint tells the compiler that the @code{Flags}
25517 variable will come from the eax register. Here is the resulting code:
25525 movl %eax,-40(%ebp)
25530 The compiler generated the store of eax into Flags after
25531 expanding the assembler code.
25533 Actually, there was no need to pop the flags into the eax register;
25534 more simply, we could just pop the flags directly into the program variable:
25536 @smallexample @c ada
25538 with Interfaces; use Interfaces;
25539 with Ada.Text_IO; use Ada.Text_IO;
25540 with System.Machine_Code; use System.Machine_Code;
25541 procedure Get_Flags_3 is
25542 Flags : Unsigned_32;
25545 Asm ("pushfl" & LF & HT & -- push flags on stack
25546 "pop %0", -- save flags in Flags
25547 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25548 Put_Line ("Flags register:" & Flags'Img);
25553 @c ---------------------------------------------------------------------------
25554 @node Input Variables in Inline Assembler
25555 @section Input Variables in Inline Assembler
25558 The example in this section illustrates how to specify the source operands
25559 for assembly language statements.
25560 The program simply increments its input value by 1:
25562 @smallexample @c ada
25564 with Interfaces; use Interfaces;
25565 with Ada.Text_IO; use Ada.Text_IO;
25566 with System.Machine_Code; use System.Machine_Code;
25567 procedure Increment is
25569 function Incr (Value : Unsigned_32) return Unsigned_32 is
25570 Result : Unsigned_32;
25573 Inputs => Unsigned_32'Asm_Input ("a", Value),
25574 Outputs => Unsigned_32'Asm_Output ("=a", Result));
25578 Value : Unsigned_32;
25582 Put_Line ("Value before is" & Value'Img);
25583 Value := Incr (Value);
25584 Put_Line ("Value after is" & Value'Img);
25589 The @code{Outputs} parameter to @code{Asm} specifies
25590 that the result will be in the eax register and that it is to be stored
25591 in the @code{Result} variable.
25593 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
25594 but with an @code{Asm_Input} attribute.
25595 The @code{"="} constraint, indicating an output value, is not present.
25597 You can have multiple input variables, in the same way that you can have more
25598 than one output variable.
25600 The parameter count (%0, %1) etc, now starts at the first input
25601 statement, and continues with the output statements.
25602 When both parameters use the same variable, the
25603 compiler will treat them as the same %n operand, which is the case here.
25605 Just as the @code{Outputs} parameter causes the register to be stored into the
25606 target variable after execution of the assembler statements, so does the
25607 @code{Inputs} parameter cause its variable to be loaded into the register
25608 before execution of the assembler statements.
25610 Thus the effect of the @code{Asm} invocation is:
25612 @item load the 32-bit value of @code{Value} into eax
25613 @item execute the @code{incl %eax} instruction
25614 @item store the contents of eax into the @code{Result} variable
25617 The resulting assembler file (with @option{-O2} optimization) contains:
25620 _increment__incr.1:
25633 @c ---------------------------------------------------------------------------
25634 @node Inlining Inline Assembler Code
25635 @section Inlining Inline Assembler Code
25638 For a short subprogram such as the @code{Incr} function in the previous
25639 section, the overhead of the call and return (creating / deleting the stack
25640 frame) can be significant, compared to the amount of code in the subprogram
25641 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
25642 which directs the compiler to expand invocations of the subprogram at the
25643 point(s) of call, instead of setting up a stack frame for out-of-line calls.
25644 Here is the resulting program:
25646 @smallexample @c ada
25648 with Interfaces; use Interfaces;
25649 with Ada.Text_IO; use Ada.Text_IO;
25650 with System.Machine_Code; use System.Machine_Code;
25651 procedure Increment_2 is
25653 function Incr (Value : Unsigned_32) return Unsigned_32 is
25654 Result : Unsigned_32;
25657 Inputs => Unsigned_32'Asm_Input ("a", Value),
25658 Outputs => Unsigned_32'Asm_Output ("=a", Result));
25661 pragma Inline (Increment);
25663 Value : Unsigned_32;
25667 Put_Line ("Value before is" & Value'Img);
25668 Value := Increment (Value);
25669 Put_Line ("Value after is" & Value'Img);
25674 Compile the program with both optimization (@option{-O2}) and inlining
25675 (@option{-gnatn}) enabled.
25677 The @code{Incr} function is still compiled as usual, but at the
25678 point in @code{Increment} where our function used to be called:
25683 call _increment__incr.1
25688 the code for the function body directly appears:
25701 thus saving the overhead of stack frame setup and an out-of-line call.
25703 @c ---------------------------------------------------------------------------
25704 @node Other Asm Functionality
25705 @section Other @code{Asm} Functionality
25708 This section describes two important parameters to the @code{Asm}
25709 procedure: @code{Clobber}, which identifies register usage;
25710 and @code{Volatile}, which inhibits unwanted optimizations.
25713 * The Clobber Parameter::
25714 * The Volatile Parameter::
25717 @c ---------------------------------------------------------------------------
25718 @node The Clobber Parameter
25719 @subsection The @code{Clobber} Parameter
25722 One of the dangers of intermixing assembly language and a compiled language
25723 such as Ada is that the compiler needs to be aware of which registers are
25724 being used by the assembly code. In some cases, such as the earlier examples,
25725 the constraint string is sufficient to indicate register usage (e.g.,
25727 the eax register). But more generally, the compiler needs an explicit
25728 identification of the registers that are used by the Inline Assembly
25731 Using a register that the compiler doesn't know about
25732 could be a side effect of an instruction (like @code{mull}
25733 storing its result in both eax and edx).
25734 It can also arise from explicit register usage in your
25735 assembly code; for example:
25738 Asm ("movl %0, %%ebx" & LF & HT &
25740 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25741 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
25745 where the compiler (since it does not analyze the @code{Asm} template string)
25746 does not know you are using the ebx register.
25748 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
25749 to identify the registers that will be used by your assembly code:
25753 Asm ("movl %0, %%ebx" & LF & HT &
25755 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25756 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
25761 The Clobber parameter is a static string expression specifying the
25762 register(s) you are using. Note that register names are @emph{not} prefixed
25763 by a percent sign. Also, if more than one register is used then their names
25764 are separated by commas; e.g., @code{"eax, ebx"}
25766 The @code{Clobber} parameter has several additional uses:
25768 @item Use ``register'' name @code{cc} to indicate that flags might have changed
25769 @item Use ``register'' name @code{memory} if you changed a memory location
25772 @c ---------------------------------------------------------------------------
25773 @node The Volatile Parameter
25774 @subsection The @code{Volatile} Parameter
25775 @cindex Volatile parameter
25778 Compiler optimizations in the presence of Inline Assembler may sometimes have
25779 unwanted effects. For example, when an @code{Asm} invocation with an input
25780 variable is inside a loop, the compiler might move the loading of the input
25781 variable outside the loop, regarding it as a one-time initialization.
25783 If this effect is not desired, you can disable such optimizations by setting
25784 the @code{Volatile} parameter to @code{True}; for example:
25786 @smallexample @c ada
25788 Asm ("movl %0, %%ebx" & LF & HT &
25790 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25791 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
25797 By default, @code{Volatile} is set to @code{False} unless there is no
25798 @code{Outputs} parameter.
25800 Although setting @code{Volatile} to @code{True} prevents unwanted
25801 optimizations, it will also disable other optimizations that might be
25802 important for efficiency. In general, you should set @code{Volatile}
25803 to @code{True} only if the compiler's optimizations have created
25805 @c END OF INLINE ASSEMBLER CHAPTER
25806 @c ===============================
25808 @c ***********************************
25809 @c * Compatibility and Porting Guide *
25810 @c ***********************************
25811 @node Compatibility and Porting Guide
25812 @appendix Compatibility and Porting Guide
25815 This chapter describes the compatibility issues that may arise between
25816 GNAT and other Ada compilation systems (including those for Ada 83),
25817 and shows how GNAT can expedite porting
25818 applications developed in other Ada environments.
25821 * Compatibility with Ada 83::
25822 * Compatibility between Ada 95 and Ada 2005::
25823 * Implementation-dependent characteristics::
25824 * Compatibility with Other Ada Systems::
25825 * Representation Clauses::
25827 @c Brief section is only in non-VMS version
25828 @c Full chapter is in VMS version
25829 * Compatibility with HP Ada 83::
25832 * Transitioning to 64-Bit GNAT for OpenVMS::
25836 @node Compatibility with Ada 83
25837 @section Compatibility with Ada 83
25838 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
25841 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
25842 particular, the design intention was that the difficulties associated
25843 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
25844 that occur when moving from one Ada 83 system to another.
25846 However, there are a number of points at which there are minor
25847 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
25848 full details of these issues,
25849 and should be consulted for a complete treatment.
25851 following subsections treat the most likely issues to be encountered.
25854 * Legal Ada 83 programs that are illegal in Ada 95::
25855 * More deterministic semantics::
25856 * Changed semantics::
25857 * Other language compatibility issues::
25860 @node Legal Ada 83 programs that are illegal in Ada 95
25861 @subsection Legal Ada 83 programs that are illegal in Ada 95
25863 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
25864 Ada 95 and thus also in Ada 2005:
25867 @item Character literals
25868 Some uses of character literals are ambiguous. Since Ada 95 has introduced
25869 @code{Wide_Character} as a new predefined character type, some uses of
25870 character literals that were legal in Ada 83 are illegal in Ada 95.
25872 @smallexample @c ada
25873 for Char in 'A' .. 'Z' loop @dots{} end loop;
25877 The problem is that @code{'A'} and @code{'Z'} could be from either
25878 @code{Character} or @code{Wide_Character}. The simplest correction
25879 is to make the type explicit; e.g.:
25880 @smallexample @c ada
25881 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
25884 @item New reserved words
25885 The identifiers @code{abstract}, @code{aliased}, @code{protected},
25886 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
25887 Existing Ada 83 code using any of these identifiers must be edited to
25888 use some alternative name.
25890 @item Freezing rules
25891 The rules in Ada 95 are slightly different with regard to the point at
25892 which entities are frozen, and representation pragmas and clauses are
25893 not permitted past the freeze point. This shows up most typically in
25894 the form of an error message complaining that a representation item
25895 appears too late, and the appropriate corrective action is to move
25896 the item nearer to the declaration of the entity to which it refers.
25898 A particular case is that representation pragmas
25901 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
25903 cannot be applied to a subprogram body. If necessary, a separate subprogram
25904 declaration must be introduced to which the pragma can be applied.
25906 @item Optional bodies for library packages
25907 In Ada 83, a package that did not require a package body was nevertheless
25908 allowed to have one. This lead to certain surprises in compiling large
25909 systems (situations in which the body could be unexpectedly ignored by the
25910 binder). In Ada 95, if a package does not require a body then it is not
25911 permitted to have a body. To fix this problem, simply remove a redundant
25912 body if it is empty, or, if it is non-empty, introduce a dummy declaration
25913 into the spec that makes the body required. One approach is to add a private
25914 part to the package declaration (if necessary), and define a parameterless
25915 procedure called @code{Requires_Body}, which must then be given a dummy
25916 procedure body in the package body, which then becomes required.
25917 Another approach (assuming that this does not introduce elaboration
25918 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
25919 since one effect of this pragma is to require the presence of a package body.
25921 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
25922 In Ada 95, the exception @code{Numeric_Error} is a renaming of
25923 @code{Constraint_Error}.
25924 This means that it is illegal to have separate exception handlers for
25925 the two exceptions. The fix is simply to remove the handler for the
25926 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
25927 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
25929 @item Indefinite subtypes in generics
25930 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
25931 as the actual for a generic formal private type, but then the instantiation
25932 would be illegal if there were any instances of declarations of variables
25933 of this type in the generic body. In Ada 95, to avoid this clear violation
25934 of the methodological principle known as the ``contract model'',
25935 the generic declaration explicitly indicates whether
25936 or not such instantiations are permitted. If a generic formal parameter
25937 has explicit unknown discriminants, indicated by using @code{(<>)} after the
25938 type name, then it can be instantiated with indefinite types, but no
25939 stand-alone variables can be declared of this type. Any attempt to declare
25940 such a variable will result in an illegality at the time the generic is
25941 declared. If the @code{(<>)} notation is not used, then it is illegal
25942 to instantiate the generic with an indefinite type.
25943 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
25944 It will show up as a compile time error, and
25945 the fix is usually simply to add the @code{(<>)} to the generic declaration.
25948 @node More deterministic semantics
25949 @subsection More deterministic semantics
25953 Conversions from real types to integer types round away from 0. In Ada 83
25954 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
25955 implementation freedom was intended to support unbiased rounding in
25956 statistical applications, but in practice it interfered with portability.
25957 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
25958 is required. Numeric code may be affected by this change in semantics.
25959 Note, though, that this issue is no worse than already existed in Ada 83
25960 when porting code from one vendor to another.
25963 The Real-Time Annex introduces a set of policies that define the behavior of
25964 features that were implementation dependent in Ada 83, such as the order in
25965 which open select branches are executed.
25968 @node Changed semantics
25969 @subsection Changed semantics
25972 The worst kind of incompatibility is one where a program that is legal in
25973 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
25974 possible in Ada 83. Fortunately this is extremely rare, but the one
25975 situation that you should be alert to is the change in the predefined type
25976 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
25979 @item Range of type @code{Character}
25980 The range of @code{Standard.Character} is now the full 256 characters
25981 of Latin-1, whereas in most Ada 83 implementations it was restricted
25982 to 128 characters. Although some of the effects of
25983 this change will be manifest in compile-time rejection of legal
25984 Ada 83 programs it is possible for a working Ada 83 program to have
25985 a different effect in Ada 95, one that was not permitted in Ada 83.
25986 As an example, the expression
25987 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
25988 delivers @code{255} as its value.
25989 In general, you should look at the logic of any
25990 character-processing Ada 83 program and see whether it needs to be adapted
25991 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
25992 character handling package that may be relevant if code needs to be adapted
25993 to account for the additional Latin-1 elements.
25994 The desirable fix is to
25995 modify the program to accommodate the full character set, but in some cases
25996 it may be convenient to define a subtype or derived type of Character that
25997 covers only the restricted range.
26001 @node Other language compatibility issues
26002 @subsection Other language compatibility issues
26005 @item @option{-gnat83} switch
26006 All implementations of GNAT provide a switch that causes GNAT to operate
26007 in Ada 83 mode. In this mode, some but not all compatibility problems
26008 of the type described above are handled automatically. For example, the
26009 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
26010 as identifiers as in Ada 83.
26012 in practice, it is usually advisable to make the necessary modifications
26013 to the program to remove the need for using this switch.
26014 See @ref{Compiling Different Versions of Ada}.
26016 @item Support for removed Ada 83 pragmas and attributes
26017 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
26018 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
26019 compilers are allowed, but not required, to implement these missing
26020 elements. In contrast with some other compilers, GNAT implements all
26021 such pragmas and attributes, eliminating this compatibility concern. These
26022 include @code{pragma Interface} and the floating point type attributes
26023 (@code{Emax}, @code{Mantissa}, etc.), among other items.
26027 @node Compatibility between Ada 95 and Ada 2005
26028 @section Compatibility between Ada 95 and Ada 2005
26029 @cindex Compatibility between Ada 95 and Ada 2005
26032 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
26033 a number of incompatibilities. Several are enumerated below;
26034 for a complete description please see the
26035 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
26036 @cite{Rationale for Ada 2005}.
26039 @item New reserved words.
26040 The words @code{interface}, @code{overriding} and @code{synchronized} are
26041 reserved in Ada 2005.
26042 A pre-Ada 2005 program that uses any of these as an identifier will be
26045 @item New declarations in predefined packages.
26046 A number of packages in the predefined environment contain new declarations:
26047 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
26048 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
26049 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
26050 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
26051 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
26052 If an Ada 95 program does a @code{with} and @code{use} of any of these
26053 packages, the new declarations may cause name clashes.
26055 @item Access parameters.
26056 A nondispatching subprogram with an access parameter cannot be renamed
26057 as a dispatching operation. This was permitted in Ada 95.
26059 @item Access types, discriminants, and constraints.
26060 Rule changes in this area have led to some incompatibilities; for example,
26061 constrained subtypes of some access types are not permitted in Ada 2005.
26063 @item Aggregates for limited types.
26064 The allowance of aggregates for limited types in Ada 2005 raises the
26065 possibility of ambiguities in legal Ada 95 programs, since additional types
26066 now need to be considered in expression resolution.
26068 @item Fixed-point multiplication and division.
26069 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
26070 were legal in Ada 95 and invoked the predefined versions of these operations,
26072 The ambiguity may be resolved either by applying a type conversion to the
26073 expression, or by explicitly invoking the operation from package
26076 @item Return-by-reference types.
26077 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
26078 can declare a function returning a value from an anonymous access type.
26082 @node Implementation-dependent characteristics
26083 @section Implementation-dependent characteristics
26085 Although the Ada language defines the semantics of each construct as
26086 precisely as practical, in some situations (for example for reasons of
26087 efficiency, or where the effect is heavily dependent on the host or target
26088 platform) the implementation is allowed some freedom. In porting Ada 83
26089 code to GNAT, you need to be aware of whether / how the existing code
26090 exercised such implementation dependencies. Such characteristics fall into
26091 several categories, and GNAT offers specific support in assisting the
26092 transition from certain Ada 83 compilers.
26095 * Implementation-defined pragmas::
26096 * Implementation-defined attributes::
26098 * Elaboration order::
26099 * Target-specific aspects::
26102 @node Implementation-defined pragmas
26103 @subsection Implementation-defined pragmas
26106 Ada compilers are allowed to supplement the language-defined pragmas, and
26107 these are a potential source of non-portability. All GNAT-defined pragmas
26108 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
26109 Reference Manual}, and these include several that are specifically
26110 intended to correspond to other vendors' Ada 83 pragmas.
26111 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
26112 For compatibility with HP Ada 83, GNAT supplies the pragmas
26113 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
26114 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
26115 and @code{Volatile}.
26116 Other relevant pragmas include @code{External} and @code{Link_With}.
26117 Some vendor-specific
26118 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
26120 avoiding compiler rejection of units that contain such pragmas; they are not
26121 relevant in a GNAT context and hence are not otherwise implemented.
26123 @node Implementation-defined attributes
26124 @subsection Implementation-defined attributes
26126 Analogous to pragmas, the set of attributes may be extended by an
26127 implementation. All GNAT-defined attributes are described in
26128 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
26129 Manual}, and these include several that are specifically intended
26130 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
26131 the attribute @code{VADS_Size} may be useful. For compatibility with HP
26132 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
26136 @subsection Libraries
26138 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
26139 code uses vendor-specific libraries then there are several ways to manage
26140 this in Ada 95 or Ada 2005:
26143 If the source code for the libraries (specs and bodies) are
26144 available, then the libraries can be migrated in the same way as the
26147 If the source code for the specs but not the bodies are
26148 available, then you can reimplement the bodies.
26150 Some features introduced by Ada 95 obviate the need for library support. For
26151 example most Ada 83 vendors supplied a package for unsigned integers. The
26152 Ada 95 modular type feature is the preferred way to handle this need, so
26153 instead of migrating or reimplementing the unsigned integer package it may
26154 be preferable to retrofit the application using modular types.
26157 @node Elaboration order
26158 @subsection Elaboration order
26160 The implementation can choose any elaboration order consistent with the unit
26161 dependency relationship. This freedom means that some orders can result in
26162 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
26163 to invoke a subprogram its body has been elaborated, or to instantiate a
26164 generic before the generic body has been elaborated. By default GNAT
26165 attempts to choose a safe order (one that will not encounter access before
26166 elaboration problems) by implicitly inserting @code{Elaborate} or
26167 @code{Elaborate_All} pragmas where
26168 needed. However, this can lead to the creation of elaboration circularities
26169 and a resulting rejection of the program by gnatbind. This issue is
26170 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
26171 In brief, there are several
26172 ways to deal with this situation:
26176 Modify the program to eliminate the circularities, e.g.@: by moving
26177 elaboration-time code into explicitly-invoked procedures
26179 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
26180 @code{Elaborate} pragmas, and then inhibit the generation of implicit
26181 @code{Elaborate_All}
26182 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
26183 (by selectively suppressing elaboration checks via pragma
26184 @code{Suppress(Elaboration_Check)} when it is safe to do so).
26187 @node Target-specific aspects
26188 @subsection Target-specific aspects
26190 Low-level applications need to deal with machine addresses, data
26191 representations, interfacing with assembler code, and similar issues. If
26192 such an Ada 83 application is being ported to different target hardware (for
26193 example where the byte endianness has changed) then you will need to
26194 carefully examine the program logic; the porting effort will heavily depend
26195 on the robustness of the original design. Moreover, Ada 95 (and thus
26196 Ada 2005) are sometimes
26197 incompatible with typical Ada 83 compiler practices regarding implicit
26198 packing, the meaning of the Size attribute, and the size of access values.
26199 GNAT's approach to these issues is described in @ref{Representation Clauses}.
26201 @node Compatibility with Other Ada Systems
26202 @section Compatibility with Other Ada Systems
26205 If programs avoid the use of implementation dependent and
26206 implementation defined features, as documented in the @cite{Ada
26207 Reference Manual}, there should be a high degree of portability between
26208 GNAT and other Ada systems. The following are specific items which
26209 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
26210 compilers, but do not affect porting code to GNAT@.
26211 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
26212 the following issues may or may not arise for Ada 2005 programs
26213 when other compilers appear.)
26216 @item Ada 83 Pragmas and Attributes
26217 Ada 95 compilers are allowed, but not required, to implement the missing
26218 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
26219 GNAT implements all such pragmas and attributes, eliminating this as
26220 a compatibility concern, but some other Ada 95 compilers reject these
26221 pragmas and attributes.
26223 @item Specialized Needs Annexes
26224 GNAT implements the full set of special needs annexes. At the
26225 current time, it is the only Ada 95 compiler to do so. This means that
26226 programs making use of these features may not be portable to other Ada
26227 95 compilation systems.
26229 @item Representation Clauses
26230 Some other Ada 95 compilers implement only the minimal set of
26231 representation clauses required by the Ada 95 reference manual. GNAT goes
26232 far beyond this minimal set, as described in the next section.
26235 @node Representation Clauses
26236 @section Representation Clauses
26239 The Ada 83 reference manual was quite vague in describing both the minimal
26240 required implementation of representation clauses, and also their precise
26241 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
26242 minimal set of capabilities required is still quite limited.
26244 GNAT implements the full required set of capabilities in
26245 Ada 95 and Ada 2005, but also goes much further, and in particular
26246 an effort has been made to be compatible with existing Ada 83 usage to the
26247 greatest extent possible.
26249 A few cases exist in which Ada 83 compiler behavior is incompatible with
26250 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
26251 intentional or accidental dependence on specific implementation dependent
26252 characteristics of these Ada 83 compilers. The following is a list of
26253 the cases most likely to arise in existing Ada 83 code.
26256 @item Implicit Packing
26257 Some Ada 83 compilers allowed a Size specification to cause implicit
26258 packing of an array or record. This could cause expensive implicit
26259 conversions for change of representation in the presence of derived
26260 types, and the Ada design intends to avoid this possibility.
26261 Subsequent AI's were issued to make it clear that such implicit
26262 change of representation in response to a Size clause is inadvisable,
26263 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
26264 Reference Manuals as implementation advice that is followed by GNAT@.
26265 The problem will show up as an error
26266 message rejecting the size clause. The fix is simply to provide
26267 the explicit pragma @code{Pack}, or for more fine tuned control, provide
26268 a Component_Size clause.
26270 @item Meaning of Size Attribute
26271 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
26272 the minimal number of bits required to hold values of the type. For example,
26273 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
26274 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
26275 some 32 in this situation. This problem will usually show up as a compile
26276 time error, but not always. It is a good idea to check all uses of the
26277 'Size attribute when porting Ada 83 code. The GNAT specific attribute
26278 Object_Size can provide a useful way of duplicating the behavior of
26279 some Ada 83 compiler systems.
26281 @item Size of Access Types
26282 A common assumption in Ada 83 code is that an access type is in fact a pointer,
26283 and that therefore it will be the same size as a System.Address value. This
26284 assumption is true for GNAT in most cases with one exception. For the case of
26285 a pointer to an unconstrained array type (where the bounds may vary from one
26286 value of the access type to another), the default is to use a ``fat pointer'',
26287 which is represented as two separate pointers, one to the bounds, and one to
26288 the array. This representation has a number of advantages, including improved
26289 efficiency. However, it may cause some difficulties in porting existing Ada 83
26290 code which makes the assumption that, for example, pointers fit in 32 bits on
26291 a machine with 32-bit addressing.
26293 To get around this problem, GNAT also permits the use of ``thin pointers'' for
26294 access types in this case (where the designated type is an unconstrained array
26295 type). These thin pointers are indeed the same size as a System.Address value.
26296 To specify a thin pointer, use a size clause for the type, for example:
26298 @smallexample @c ada
26299 type X is access all String;
26300 for X'Size use Standard'Address_Size;
26304 which will cause the type X to be represented using a single pointer.
26305 When using this representation, the bounds are right behind the array.
26306 This representation is slightly less efficient, and does not allow quite
26307 such flexibility in the use of foreign pointers or in using the
26308 Unrestricted_Access attribute to create pointers to non-aliased objects.
26309 But for any standard portable use of the access type it will work in
26310 a functionally correct manner and allow porting of existing code.
26311 Note that another way of forcing a thin pointer representation
26312 is to use a component size clause for the element size in an array,
26313 or a record representation clause for an access field in a record.
26317 @c This brief section is only in the non-VMS version
26318 @c The complete chapter on HP Ada is in the VMS version
26319 @node Compatibility with HP Ada 83
26320 @section Compatibility with HP Ada 83
26323 The VMS version of GNAT fully implements all the pragmas and attributes
26324 provided by HP Ada 83, as well as providing the standard HP Ada 83
26325 libraries, including Starlet. In addition, data layouts and parameter
26326 passing conventions are highly compatible. This means that porting
26327 existing HP Ada 83 code to GNAT in VMS systems should be easier than
26328 most other porting efforts. The following are some of the most
26329 significant differences between GNAT and HP Ada 83.
26332 @item Default floating-point representation
26333 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
26334 it is VMS format. GNAT does implement the necessary pragmas
26335 (Long_Float, Float_Representation) for changing this default.
26338 The package System in GNAT exactly corresponds to the definition in the
26339 Ada 95 reference manual, which means that it excludes many of the
26340 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
26341 that contains the additional definitions, and a special pragma,
26342 Extend_System allows this package to be treated transparently as an
26343 extension of package System.
26346 The definitions provided by Aux_DEC are exactly compatible with those
26347 in the HP Ada 83 version of System, with one exception.
26348 HP Ada provides the following declarations:
26350 @smallexample @c ada
26351 TO_ADDRESS (INTEGER)
26352 TO_ADDRESS (UNSIGNED_LONGWORD)
26353 TO_ADDRESS (@i{universal_integer})
26357 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
26358 an extension to Ada 83 not strictly compatible with the reference manual.
26359 In GNAT, we are constrained to be exactly compatible with the standard,
26360 and this means we cannot provide this capability. In HP Ada 83, the
26361 point of this definition is to deal with a call like:
26363 @smallexample @c ada
26364 TO_ADDRESS (16#12777#);
26368 Normally, according to the Ada 83 standard, one would expect this to be
26369 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
26370 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
26371 definition using @i{universal_integer} takes precedence.
26373 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
26374 is not possible to be 100% compatible. Since there are many programs using
26375 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
26376 to change the name of the function in the UNSIGNED_LONGWORD case, so the
26377 declarations provided in the GNAT version of AUX_Dec are:
26379 @smallexample @c ada
26380 function To_Address (X : Integer) return Address;
26381 pragma Pure_Function (To_Address);
26383 function To_Address_Long (X : Unsigned_Longword)
26385 pragma Pure_Function (To_Address_Long);
26389 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
26390 change the name to TO_ADDRESS_LONG@.
26392 @item Task_Id values
26393 The Task_Id values assigned will be different in the two systems, and GNAT
26394 does not provide a specified value for the Task_Id of the environment task,
26395 which in GNAT is treated like any other declared task.
26399 For full details on these and other less significant compatibility issues,
26400 see appendix E of the HP publication entitled @cite{HP Ada, Technical
26401 Overview and Comparison on HP Platforms}.
26403 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
26404 attributes are recognized, although only a subset of them can sensibly
26405 be implemented. The description of pragmas in @ref{Implementation
26406 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
26407 indicates whether or not they are applicable to non-VMS systems.
26411 @node Transitioning to 64-Bit GNAT for OpenVMS
26412 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
26415 This section is meant to assist users of pre-2006 @value{EDITION}
26416 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
26417 the version of the GNAT technology supplied in 2006 and later for
26418 OpenVMS on both Alpha and I64.
26421 * Introduction to transitioning::
26422 * Migration of 32 bit code::
26423 * Taking advantage of 64 bit addressing::
26424 * Technical details::
26427 @node Introduction to transitioning
26428 @subsection Introduction
26431 64-bit @value{EDITION} for Open VMS has been designed to meet
26436 Providing a full conforming implementation of Ada 95 and Ada 2005
26439 Allowing maximum backward compatibility, thus easing migration of existing
26443 Supplying a path for exploiting the full 64-bit address range
26447 Ada's strong typing semantics has made it
26448 impractical to have different 32-bit and 64-bit modes. As soon as
26449 one object could possibly be outside the 32-bit address space, this
26450 would make it necessary for the @code{System.Address} type to be 64 bits.
26451 In particular, this would cause inconsistencies if 32-bit code is
26452 called from 64-bit code that raises an exception.
26454 This issue has been resolved by always using 64-bit addressing
26455 at the system level, but allowing for automatic conversions between
26456 32-bit and 64-bit addresses where required. Thus users who
26457 do not currently require 64-bit addressing capabilities, can
26458 recompile their code with only minimal changes (and indeed
26459 if the code is written in portable Ada, with no assumptions about
26460 the size of the @code{Address} type, then no changes at all are necessary).
26462 this approach provides a simple, gradual upgrade path to future
26463 use of larger memories than available for 32-bit systems.
26464 Also, newly written applications or libraries will by default
26465 be fully compatible with future systems exploiting 64-bit
26466 addressing capabilities.
26468 @ref{Migration of 32 bit code}, will focus on porting applications
26469 that do not require more than 2 GB of
26470 addressable memory. This code will be referred to as
26471 @emph{32-bit code}.
26472 For applications intending to exploit the full 64-bit address space,
26473 @ref{Taking advantage of 64 bit addressing},
26474 will consider further changes that may be required.
26475 Such code will be referred to below as @emph{64-bit code}.
26477 @node Migration of 32 bit code
26478 @subsection Migration of 32-bit code
26483 * Unchecked conversions::
26484 * Predefined constants::
26485 * Interfacing with C::
26486 * Experience with source compatibility::
26489 @node Address types
26490 @subsubsection Address types
26493 To solve the problem of mixing 64-bit and 32-bit addressing,
26494 while maintaining maximum backward compatibility, the following
26495 approach has been taken:
26499 @code{System.Address} always has a size of 64 bits
26502 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
26506 Since @code{System.Short_Address} is a subtype of @code{System.Address},
26507 a @code{Short_Address}
26508 may be used where an @code{Address} is required, and vice versa, without
26509 needing explicit type conversions.
26510 By virtue of the Open VMS parameter passing conventions,
26512 and exported subprograms that have 32-bit address parameters are
26513 compatible with those that have 64-bit address parameters.
26514 (See @ref{Making code 64 bit clean} for details.)
26516 The areas that may need attention are those where record types have
26517 been defined that contain components of the type @code{System.Address}, and
26518 where objects of this type are passed to code expecting a record layout with
26521 Different compilers on different platforms cannot be
26522 expected to represent the same type in the same way,
26523 since alignment constraints
26524 and other system-dependent properties affect the compiler's decision.
26525 For that reason, Ada code
26526 generally uses representation clauses to specify the expected
26527 layout where required.
26529 If such a representation clause uses 32 bits for a component having
26530 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
26531 will detect that error and produce a specific diagnostic message.
26532 The developer should then determine whether the representation
26533 should be 64 bits or not and make either of two changes:
26534 change the size to 64 bits and leave the type as @code{System.Address}, or
26535 leave the size as 32 bits and change the type to @code{System.Short_Address}.
26536 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
26537 required in any code setting or accessing the field; the compiler will
26538 automatically perform any needed conversions between address
26542 @subsubsection Access types
26545 By default, objects designated by access values are always
26546 allocated in the 32-bit
26547 address space. Thus legacy code will never contain
26548 any objects that are not addressable with 32-bit addresses, and
26549 the compiler will never raise exceptions as result of mixing
26550 32-bit and 64-bit addresses.
26552 However, the access values themselves are represented in 64 bits, for optimum
26553 performance and future compatibility with 64-bit code. As was
26554 the case with @code{System.Address}, the compiler will give an error message
26555 if an object or record component has a representation clause that
26556 requires the access value to fit in 32 bits. In such a situation,
26557 an explicit size clause for the access type, specifying 32 bits,
26558 will have the desired effect.
26560 General access types (declared with @code{access all}) can never be
26561 32 bits, as values of such types must be able to refer to any object
26562 of the designated type,
26563 including objects residing outside the 32-bit address range.
26564 Existing Ada 83 code will not contain such type definitions,
26565 however, since general access types were introduced in Ada 95.
26567 @node Unchecked conversions
26568 @subsubsection Unchecked conversions
26571 In the case of an @code{Unchecked_Conversion} where the source type is a
26572 64-bit access type or the type @code{System.Address}, and the target
26573 type is a 32-bit type, the compiler will generate a warning.
26574 Even though the generated code will still perform the required
26575 conversions, it is highly recommended in these cases to use
26576 respectively a 32-bit access type or @code{System.Short_Address}
26577 as the source type.
26579 @node Predefined constants
26580 @subsubsection Predefined constants
26583 The following table shows the correspondence between pre-2006 versions of
26584 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
26587 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
26588 @item @b{Constant} @tab @b{Old} @tab @b{New}
26589 @item @code{System.Word_Size} @tab 32 @tab 64
26590 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
26591 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
26592 @item @code{System.Address_Size} @tab 32 @tab 64
26596 If you need to refer to the specific
26597 memory size of a 32-bit implementation, instead of the
26598 actual memory size, use @code{System.Short_Memory_Size}
26599 rather than @code{System.Memory_Size}.
26600 Similarly, references to @code{System.Address_Size} may need
26601 to be replaced by @code{System.Short_Address'Size}.
26602 The program @command{gnatfind} may be useful for locating
26603 references to the above constants, so that you can verify that they
26606 @node Interfacing with C
26607 @subsubsection Interfacing with C
26610 In order to minimize the impact of the transition to 64-bit addresses on
26611 legacy programs, some fundamental types in the @code{Interfaces.C}
26612 package hierarchy continue to be represented in 32 bits.
26613 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
26614 This eases integration with the default HP C layout choices, for example
26615 as found in the system routines in @code{DECC$SHR.EXE}.
26616 Because of this implementation choice, the type fully compatible with
26617 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
26618 Depending on the context the compiler will issue a
26619 warning or an error when type @code{Address} is used, alerting the user to a
26620 potential problem. Otherwise 32-bit programs that use
26621 @code{Interfaces.C} should normally not require code modifications
26623 The other issue arising with C interfacing concerns pragma @code{Convention}.
26624 For VMS 64-bit systems, there is an issue of the appropriate default size
26625 of C convention pointers in the absence of an explicit size clause. The HP
26626 C compiler can choose either 32 or 64 bits depending on compiler options.
26627 GNAT chooses 32-bits rather than 64-bits in the default case where no size
26628 clause is given. This proves a better choice for porting 32-bit legacy
26629 applications. In order to have a 64-bit representation, it is necessary to
26630 specify a size representation clause. For example:
26632 @smallexample @c ada
26633 type int_star is access Interfaces.C.int;
26634 pragma Convention(C, int_star);
26635 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
26638 @node Experience with source compatibility
26639 @subsubsection Experience with source compatibility
26642 The Security Server and STARLET on I64 provide an interesting ``test case''
26643 for source compatibility issues, since it is in such system code
26644 where assumptions about @code{Address} size might be expected to occur.
26645 Indeed, there were a small number of occasions in the Security Server
26646 file @file{jibdef.ads}
26647 where a representation clause for a record type specified
26648 32 bits for a component of type @code{Address}.
26649 All of these errors were detected by the compiler.
26650 The repair was obvious and immediate; to simply replace @code{Address} by
26651 @code{Short_Address}.
26653 In the case of STARLET, there were several record types that should
26654 have had representation clauses but did not. In these record types
26655 there was an implicit assumption that an @code{Address} value occupied
26657 These compiled without error, but their usage resulted in run-time error
26658 returns from STARLET system calls.
26659 Future GNAT technology enhancements may include a tool that detects and flags
26660 these sorts of potential source code porting problems.
26662 @c ****************************************
26663 @node Taking advantage of 64 bit addressing
26664 @subsection Taking advantage of 64-bit addressing
26667 * Making code 64 bit clean::
26668 * Allocating memory from the 64 bit storage pool::
26669 * Restrictions on use of 64 bit objects::
26670 * Using 64 bit storage pools by default::
26671 * General access types::
26672 * STARLET and other predefined libraries::
26675 @node Making code 64 bit clean
26676 @subsubsection Making code 64-bit clean
26679 In order to prevent problems that may occur when (parts of) a
26680 system start using memory outside the 32-bit address range,
26681 we recommend some additional guidelines:
26685 For imported subprograms that take parameters of the
26686 type @code{System.Address}, ensure that these subprograms can
26687 indeed handle 64-bit addresses. If not, or when in doubt,
26688 change the subprogram declaration to specify
26689 @code{System.Short_Address} instead.
26692 Resolve all warnings related to size mismatches in
26693 unchecked conversions. Failing to do so causes
26694 erroneous execution if the source object is outside
26695 the 32-bit address space.
26698 (optional) Explicitly use the 32-bit storage pool
26699 for access types used in a 32-bit context, or use
26700 generic access types where possible
26701 (@pxref{Restrictions on use of 64 bit objects}).
26705 If these rules are followed, the compiler will automatically insert
26706 any necessary checks to ensure that no addresses or access values
26707 passed to 32-bit code ever refer to objects outside the 32-bit
26709 Any attempt to do this will raise @code{Constraint_Error}.
26711 @node Allocating memory from the 64 bit storage pool
26712 @subsubsection Allocating memory from the 64-bit storage pool
26715 For any access type @code{T} that potentially requires memory allocations
26716 beyond the 32-bit address space,
26717 use the following representation clause:
26719 @smallexample @c ada
26720 for T'Storage_Pool use System.Pool_64;
26723 @node Restrictions on use of 64 bit objects
26724 @subsubsection Restrictions on use of 64-bit objects
26727 Taking the address of an object allocated from a 64-bit storage pool,
26728 and then passing this address to a subprogram expecting
26729 @code{System.Short_Address},
26730 or assigning it to a variable of type @code{Short_Address}, will cause
26731 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
26732 (@pxref{Making code 64 bit clean}), or checks are suppressed,
26733 no exception is raised and execution
26734 will become erroneous.
26736 @node Using 64 bit storage pools by default
26737 @subsubsection Using 64-bit storage pools by default
26740 In some cases it may be desirable to have the compiler allocate
26741 from 64-bit storage pools by default. This may be the case for
26742 libraries that are 64-bit clean, but may be used in both 32-bit
26743 and 64-bit contexts. For these cases the following configuration
26744 pragma may be specified:
26746 @smallexample @c ada
26747 pragma Pool_64_Default;
26751 Any code compiled in the context of this pragma will by default
26752 use the @code{System.Pool_64} storage pool. This default may be overridden
26753 for a specific access type @code{T} by the representation clause:
26755 @smallexample @c ada
26756 for T'Storage_Pool use System.Pool_32;
26760 Any object whose address may be passed to a subprogram with a
26761 @code{Short_Address} argument, or assigned to a variable of type
26762 @code{Short_Address}, needs to be allocated from this pool.
26764 @node General access types
26765 @subsubsection General access types
26768 Objects designated by access values from a
26769 general access type (declared with @code{access all}) are never allocated
26770 from a 64-bit storage pool. Code that uses general access types will
26771 accept objects allocated in either 32-bit or 64-bit address spaces,
26772 but never allocate objects outside the 32-bit address space.
26773 Using general access types ensures maximum compatibility with both
26774 32-bit and 64-bit code.
26776 @node STARLET and other predefined libraries
26777 @subsubsection STARLET and other predefined libraries
26780 All code that comes as part of GNAT is 64-bit clean, but the
26781 restrictions given in @ref{Restrictions on use of 64 bit objects},
26782 still apply. Look at the package
26783 specs to see in which contexts objects allocated
26784 in 64-bit address space are acceptable.
26786 @node Technical details
26787 @subsection Technical details
26790 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
26791 Ada standard with respect to the type of @code{System.Address}. Previous
26792 versions of GNAT Pro have defined this type as private and implemented it as a
26795 In order to allow defining @code{System.Short_Address} as a proper subtype,
26796 and to match the implicit sign extension in parameter passing,
26797 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
26798 visible (i.e., non-private) integer type.
26799 Standard operations on the type, such as the binary operators ``+'', ``-'',
26800 etc., that take @code{Address} operands and return an @code{Address} result,
26801 have been hidden by declaring these
26802 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
26803 ambiguities that would otherwise result from overloading.
26804 (Note that, although @code{Address} is a visible integer type,
26805 good programming practice dictates against exploiting the type's
26806 integer properties such as literals, since this will compromise
26809 Defining @code{Address} as a visible integer type helps achieve
26810 maximum compatibility for existing Ada code,
26811 without sacrificing the capabilities of the 64-bit architecture.
26814 @c ************************************************
26816 @node Microsoft Windows Topics
26817 @appendix Microsoft Windows Topics
26823 This chapter describes topics that are specific to the Microsoft Windows
26824 platforms (NT, 2000, and XP Professional).
26827 * Using GNAT on Windows::
26828 * Using a network installation of GNAT::
26829 * CONSOLE and WINDOWS subsystems::
26830 * Temporary Files::
26831 * Mixed-Language Programming on Windows::
26832 * Windows Calling Conventions::
26833 * Introduction to Dynamic Link Libraries (DLLs)::
26834 * Using DLLs with GNAT::
26835 * Building DLLs with GNAT::
26836 * Building DLLs with GNAT Project files::
26837 * Building DLLs with gnatdll::
26838 * GNAT and Windows Resources::
26839 * Debugging a DLL::
26840 * Setting Stack Size from gnatlink::
26841 * Setting Heap Size from gnatlink::
26844 @node Using GNAT on Windows
26845 @section Using GNAT on Windows
26848 One of the strengths of the GNAT technology is that its tool set
26849 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
26850 @code{gdb} debugger, etc.) is used in the same way regardless of the
26853 On Windows this tool set is complemented by a number of Microsoft-specific
26854 tools that have been provided to facilitate interoperability with Windows
26855 when this is required. With these tools:
26860 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
26864 You can use any Dynamically Linked Library (DLL) in your Ada code (both
26865 relocatable and non-relocatable DLLs are supported).
26868 You can build Ada DLLs for use in other applications. These applications
26869 can be written in a language other than Ada (e.g., C, C++, etc). Again both
26870 relocatable and non-relocatable Ada DLLs are supported.
26873 You can include Windows resources in your Ada application.
26876 You can use or create COM/DCOM objects.
26880 Immediately below are listed all known general GNAT-for-Windows restrictions.
26881 Other restrictions about specific features like Windows Resources and DLLs
26882 are listed in separate sections below.
26887 It is not possible to use @code{GetLastError} and @code{SetLastError}
26888 when tasking, protected records, or exceptions are used. In these
26889 cases, in order to implement Ada semantics, the GNAT run-time system
26890 calls certain Win32 routines that set the last error variable to 0 upon
26891 success. It should be possible to use @code{GetLastError} and
26892 @code{SetLastError} when tasking, protected record, and exception
26893 features are not used, but it is not guaranteed to work.
26896 It is not possible to link against Microsoft libraries except for
26897 import libraries. The library must be built to be compatible with
26898 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
26899 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
26900 not be compatible with the GNAT runtime. Even if the library is
26901 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
26904 When the compilation environment is located on FAT32 drives, users may
26905 experience recompilations of the source files that have not changed if
26906 Daylight Saving Time (DST) state has changed since the last time files
26907 were compiled. NTFS drives do not have this problem.
26910 No components of the GNAT toolset use any entries in the Windows
26911 registry. The only entries that can be created are file associations and
26912 PATH settings, provided the user has chosen to create them at installation
26913 time, as well as some minimal book-keeping information needed to correctly
26914 uninstall or integrate different GNAT products.
26917 @node Using a network installation of GNAT
26918 @section Using a network installation of GNAT
26921 Make sure the system on which GNAT is installed is accessible from the
26922 current machine, i.e., the install location is shared over the network.
26923 Shared resources are accessed on Windows by means of UNC paths, which
26924 have the format @code{\\server\sharename\path}
26926 In order to use such a network installation, simply add the UNC path of the
26927 @file{bin} directory of your GNAT installation in front of your PATH. For
26928 example, if GNAT is installed in @file{\GNAT} directory of a share location
26929 called @file{c-drive} on a machine @file{LOKI}, the following command will
26932 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
26934 Be aware that every compilation using the network installation results in the
26935 transfer of large amounts of data across the network and will likely cause
26936 serious performance penalty.
26938 @node CONSOLE and WINDOWS subsystems
26939 @section CONSOLE and WINDOWS subsystems
26940 @cindex CONSOLE Subsystem
26941 @cindex WINDOWS Subsystem
26945 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
26946 (which is the default subsystem) will always create a console when
26947 launching the application. This is not something desirable when the
26948 application has a Windows GUI. To get rid of this console the
26949 application must be using the @code{WINDOWS} subsystem. To do so
26950 the @option{-mwindows} linker option must be specified.
26953 $ gnatmake winprog -largs -mwindows
26956 @node Temporary Files
26957 @section Temporary Files
26958 @cindex Temporary files
26961 It is possible to control where temporary files gets created by setting
26962 the @env{TMP} environment variable. The file will be created:
26965 @item Under the directory pointed to by the @env{TMP} environment variable if
26966 this directory exists.
26968 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
26969 set (or not pointing to a directory) and if this directory exists.
26971 @item Under the current working directory otherwise.
26975 This allows you to determine exactly where the temporary
26976 file will be created. This is particularly useful in networked
26977 environments where you may not have write access to some
26980 @node Mixed-Language Programming on Windows
26981 @section Mixed-Language Programming on Windows
26984 Developing pure Ada applications on Windows is no different than on
26985 other GNAT-supported platforms. However, when developing or porting an
26986 application that contains a mix of Ada and C/C++, the choice of your
26987 Windows C/C++ development environment conditions your overall
26988 interoperability strategy.
26990 If you use @command{gcc} to compile the non-Ada part of your application,
26991 there are no Windows-specific restrictions that affect the overall
26992 interoperability with your Ada code. If you plan to use
26993 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
26994 the following limitations:
26998 You cannot link your Ada code with an object or library generated with
26999 Microsoft tools if these use the @code{.tls} section (Thread Local
27000 Storage section) since the GNAT linker does not yet support this section.
27003 You cannot link your Ada code with an object or library generated with
27004 Microsoft tools if these use I/O routines other than those provided in
27005 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
27006 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
27007 libraries can cause a conflict with @code{msvcrt.dll} services. For
27008 instance Visual C++ I/O stream routines conflict with those in
27013 If you do want to use the Microsoft tools for your non-Ada code and hit one
27014 of the above limitations, you have two choices:
27018 Encapsulate your non-Ada code in a DLL to be linked with your Ada
27019 application. In this case, use the Microsoft or whatever environment to
27020 build the DLL and use GNAT to build your executable
27021 (@pxref{Using DLLs with GNAT}).
27024 Or you can encapsulate your Ada code in a DLL to be linked with the
27025 other part of your application. In this case, use GNAT to build the DLL
27026 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
27027 environment to build your executable.
27030 @node Windows Calling Conventions
27031 @section Windows Calling Conventions
27036 * C Calling Convention::
27037 * Stdcall Calling Convention::
27038 * Win32 Calling Convention::
27039 * DLL Calling Convention::
27043 When a subprogram @code{F} (caller) calls a subprogram @code{G}
27044 (callee), there are several ways to push @code{G}'s parameters on the
27045 stack and there are several possible scenarios to clean up the stack
27046 upon @code{G}'s return. A calling convention is an agreed upon software
27047 protocol whereby the responsibilities between the caller (@code{F}) and
27048 the callee (@code{G}) are clearly defined. Several calling conventions
27049 are available for Windows:
27053 @code{C} (Microsoft defined)
27056 @code{Stdcall} (Microsoft defined)
27059 @code{Win32} (GNAT specific)
27062 @code{DLL} (GNAT specific)
27065 @node C Calling Convention
27066 @subsection @code{C} Calling Convention
27069 This is the default calling convention used when interfacing to C/C++
27070 routines compiled with either @command{gcc} or Microsoft Visual C++.
27072 In the @code{C} calling convention subprogram parameters are pushed on the
27073 stack by the caller from right to left. The caller itself is in charge of
27074 cleaning up the stack after the call. In addition, the name of a routine
27075 with @code{C} calling convention is mangled by adding a leading underscore.
27077 The name to use on the Ada side when importing (or exporting) a routine
27078 with @code{C} calling convention is the name of the routine. For
27079 instance the C function:
27082 int get_val (long);
27086 should be imported from Ada as follows:
27088 @smallexample @c ada
27090 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
27091 pragma Import (C, Get_Val, External_Name => "get_val");
27096 Note that in this particular case the @code{External_Name} parameter could
27097 have been omitted since, when missing, this parameter is taken to be the
27098 name of the Ada entity in lower case. When the @code{Link_Name} parameter
27099 is missing, as in the above example, this parameter is set to be the
27100 @code{External_Name} with a leading underscore.
27102 When importing a variable defined in C, you should always use the @code{C}
27103 calling convention unless the object containing the variable is part of a
27104 DLL (in which case you should use the @code{Stdcall} calling
27105 convention, @pxref{Stdcall Calling Convention}).
27107 @node Stdcall Calling Convention
27108 @subsection @code{Stdcall} Calling Convention
27111 This convention, which was the calling convention used for Pascal
27112 programs, is used by Microsoft for all the routines in the Win32 API for
27113 efficiency reasons. It must be used to import any routine for which this
27114 convention was specified.
27116 In the @code{Stdcall} calling convention subprogram parameters are pushed
27117 on the stack by the caller from right to left. The callee (and not the
27118 caller) is in charge of cleaning the stack on routine exit. In addition,
27119 the name of a routine with @code{Stdcall} calling convention is mangled by
27120 adding a leading underscore (as for the @code{C} calling convention) and a
27121 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
27122 bytes) of the parameters passed to the routine.
27124 The name to use on the Ada side when importing a C routine with a
27125 @code{Stdcall} calling convention is the name of the C routine. The leading
27126 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
27127 the compiler. For instance the Win32 function:
27130 @b{APIENTRY} int get_val (long);
27134 should be imported from Ada as follows:
27136 @smallexample @c ada
27138 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
27139 pragma Import (Stdcall, Get_Val);
27140 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
27145 As for the @code{C} calling convention, when the @code{External_Name}
27146 parameter is missing, it is taken to be the name of the Ada entity in lower
27147 case. If instead of writing the above import pragma you write:
27149 @smallexample @c ada
27151 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
27152 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
27157 then the imported routine is @code{_retrieve_val@@4}. However, if instead
27158 of specifying the @code{External_Name} parameter you specify the
27159 @code{Link_Name} as in the following example:
27161 @smallexample @c ada
27163 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
27164 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
27169 then the imported routine is @code{retrieve_val}, that is, there is no
27170 decoration at all. No leading underscore and no Stdcall suffix
27171 @code{@@}@code{@var{nn}}.
27174 This is especially important as in some special cases a DLL's entry
27175 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
27176 name generated for a call has it.
27179 It is also possible to import variables defined in a DLL by using an
27180 import pragma for a variable. As an example, if a DLL contains a
27181 variable defined as:
27188 then, to access this variable from Ada you should write:
27190 @smallexample @c ada
27192 My_Var : Interfaces.C.int;
27193 pragma Import (Stdcall, My_Var);
27198 Note that to ease building cross-platform bindings this convention
27199 will be handled as a @code{C} calling convention on non-Windows platforms.
27201 @node Win32 Calling Convention
27202 @subsection @code{Win32} Calling Convention
27205 This convention, which is GNAT-specific is fully equivalent to the
27206 @code{Stdcall} calling convention described above.
27208 @node DLL Calling Convention
27209 @subsection @code{DLL} Calling Convention
27212 This convention, which is GNAT-specific is fully equivalent to the
27213 @code{Stdcall} calling convention described above.
27215 @node Introduction to Dynamic Link Libraries (DLLs)
27216 @section Introduction to Dynamic Link Libraries (DLLs)
27220 A Dynamically Linked Library (DLL) is a library that can be shared by
27221 several applications running under Windows. A DLL can contain any number of
27222 routines and variables.
27224 One advantage of DLLs is that you can change and enhance them without
27225 forcing all the applications that depend on them to be relinked or
27226 recompiled. However, you should be aware than all calls to DLL routines are
27227 slower since, as you will understand below, such calls are indirect.
27229 To illustrate the remainder of this section, suppose that an application
27230 wants to use the services of a DLL @file{API.dll}. To use the services
27231 provided by @file{API.dll} you must statically link against the DLL or
27232 an import library which contains a jump table with an entry for each
27233 routine and variable exported by the DLL. In the Microsoft world this
27234 import library is called @file{API.lib}. When using GNAT this import
27235 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
27236 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
27238 After you have linked your application with the DLL or the import library
27239 and you run your application, here is what happens:
27243 Your application is loaded into memory.
27246 The DLL @file{API.dll} is mapped into the address space of your
27247 application. This means that:
27251 The DLL will use the stack of the calling thread.
27254 The DLL will use the virtual address space of the calling process.
27257 The DLL will allocate memory from the virtual address space of the calling
27261 Handles (pointers) can be safely exchanged between routines in the DLL
27262 routines and routines in the application using the DLL.
27266 The entries in the jump table (from the import library @file{libAPI.dll.a}
27267 or @file{API.lib} or automatically created when linking against a DLL)
27268 which is part of your application are initialized with the addresses
27269 of the routines and variables in @file{API.dll}.
27272 If present in @file{API.dll}, routines @code{DllMain} or
27273 @code{DllMainCRTStartup} are invoked. These routines typically contain
27274 the initialization code needed for the well-being of the routines and
27275 variables exported by the DLL.
27279 There is an additional point which is worth mentioning. In the Windows
27280 world there are two kind of DLLs: relocatable and non-relocatable
27281 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
27282 in the target application address space. If the addresses of two
27283 non-relocatable DLLs overlap and these happen to be used by the same
27284 application, a conflict will occur and the application will run
27285 incorrectly. Hence, when possible, it is always preferable to use and
27286 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
27287 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
27288 User's Guide) removes the debugging symbols from the DLL but the DLL can
27289 still be relocated.
27291 As a side note, an interesting difference between Microsoft DLLs and
27292 Unix shared libraries, is the fact that on most Unix systems all public
27293 routines are exported by default in a Unix shared library, while under
27294 Windows it is possible (but not required) to list exported routines in
27295 a definition file (@pxref{The Definition File}).
27297 @node Using DLLs with GNAT
27298 @section Using DLLs with GNAT
27301 * Creating an Ada Spec for the DLL Services::
27302 * Creating an Import Library::
27306 To use the services of a DLL, say @file{API.dll}, in your Ada application
27311 The Ada spec for the routines and/or variables you want to access in
27312 @file{API.dll}. If not available this Ada spec must be built from the C/C++
27313 header files provided with the DLL.
27316 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
27317 mentioned an import library is a statically linked library containing the
27318 import table which will be filled at load time to point to the actual
27319 @file{API.dll} routines. Sometimes you don't have an import library for the
27320 DLL you want to use. The following sections will explain how to build
27321 one. Note that this is optional.
27324 The actual DLL, @file{API.dll}.
27328 Once you have all the above, to compile an Ada application that uses the
27329 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
27330 you simply issue the command
27333 $ gnatmake my_ada_app -largs -lAPI
27337 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
27338 tells the GNAT linker to look first for a library named @file{API.lib}
27339 (Microsoft-style name) and if not found for a libraries named
27340 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
27341 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
27342 contains the following pragma
27344 @smallexample @c ada
27345 pragma Linker_Options ("-lAPI");
27349 you do not have to add @option{-largs -lAPI} at the end of the
27350 @command{gnatmake} command.
27352 If any one of the items above is missing you will have to create it
27353 yourself. The following sections explain how to do so using as an
27354 example a fictitious DLL called @file{API.dll}.
27356 @node Creating an Ada Spec for the DLL Services
27357 @subsection Creating an Ada Spec for the DLL Services
27360 A DLL typically comes with a C/C++ header file which provides the
27361 definitions of the routines and variables exported by the DLL. The Ada
27362 equivalent of this header file is a package spec that contains definitions
27363 for the imported entities. If the DLL you intend to use does not come with
27364 an Ada spec you have to generate one such spec yourself. For example if
27365 the header file of @file{API.dll} is a file @file{api.h} containing the
27366 following two definitions:
27378 then the equivalent Ada spec could be:
27380 @smallexample @c ada
27383 with Interfaces.C.Strings;
27388 function Get (Str : C.Strings.Chars_Ptr) return C.int;
27391 pragma Import (C, Get);
27392 pragma Import (DLL, Some_Var);
27399 Note that a variable is
27400 @strong{always imported with a Stdcall convention}. A function
27401 can have @code{C} or @code{Stdcall} convention.
27402 (@pxref{Windows Calling Conventions}).
27404 @node Creating an Import Library
27405 @subsection Creating an Import Library
27406 @cindex Import library
27409 * The Definition File::
27410 * GNAT-Style Import Library::
27411 * Microsoft-Style Import Library::
27415 If a Microsoft-style import library @file{API.lib} or a GNAT-style
27416 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
27417 with @file{API.dll} you can skip this section. You can also skip this
27418 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
27419 as in this case it is possible to link directly against the
27420 DLL. Otherwise read on.
27422 @node The Definition File
27423 @subsubsection The Definition File
27424 @cindex Definition file
27428 As previously mentioned, and unlike Unix systems, the list of symbols
27429 that are exported from a DLL must be provided explicitly in Windows.
27430 The main goal of a definition file is precisely that: list the symbols
27431 exported by a DLL. A definition file (usually a file with a @code{.def}
27432 suffix) has the following structure:
27437 @r{[}LIBRARY @var{name}@r{]}
27438 @r{[}DESCRIPTION @var{string}@r{]}
27448 @item LIBRARY @var{name}
27449 This section, which is optional, gives the name of the DLL.
27451 @item DESCRIPTION @var{string}
27452 This section, which is optional, gives a description string that will be
27453 embedded in the import library.
27456 This section gives the list of exported symbols (procedures, functions or
27457 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
27458 section of @file{API.def} looks like:
27472 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
27473 (@pxref{Windows Calling Conventions}) for a Stdcall
27474 calling convention function in the exported symbols list.
27477 There can actually be other sections in a definition file, but these
27478 sections are not relevant to the discussion at hand.
27480 @node GNAT-Style Import Library
27481 @subsubsection GNAT-Style Import Library
27484 To create a static import library from @file{API.dll} with the GNAT tools
27485 you should proceed as follows:
27489 Create the definition file @file{API.def} (@pxref{The Definition File}).
27490 For that use the @code{dll2def} tool as follows:
27493 $ dll2def API.dll > API.def
27497 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
27498 to standard output the list of entry points in the DLL. Note that if
27499 some routines in the DLL have the @code{Stdcall} convention
27500 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
27501 suffix then you'll have to edit @file{api.def} to add it, and specify
27502 @option{-k} to @command{gnatdll} when creating the import library.
27505 Here are some hints to find the right @code{@@}@var{nn} suffix.
27509 If you have the Microsoft import library (.lib), it is possible to get
27510 the right symbols by using Microsoft @code{dumpbin} tool (see the
27511 corresponding Microsoft documentation for further details).
27514 $ dumpbin /exports api.lib
27518 If you have a message about a missing symbol at link time the compiler
27519 tells you what symbol is expected. You just have to go back to the
27520 definition file and add the right suffix.
27524 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
27525 (@pxref{Using gnatdll}) as follows:
27528 $ gnatdll -e API.def -d API.dll
27532 @code{gnatdll} takes as input a definition file @file{API.def} and the
27533 name of the DLL containing the services listed in the definition file
27534 @file{API.dll}. The name of the static import library generated is
27535 computed from the name of the definition file as follows: if the
27536 definition file name is @var{xyz}@code{.def}, the import library name will
27537 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
27538 @option{-e} could have been removed because the name of the definition
27539 file (before the ``@code{.def}'' suffix) is the same as the name of the
27540 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
27543 @node Microsoft-Style Import Library
27544 @subsubsection Microsoft-Style Import Library
27547 With GNAT you can either use a GNAT-style or Microsoft-style import
27548 library. A Microsoft import library is needed only if you plan to make an
27549 Ada DLL available to applications developed with Microsoft
27550 tools (@pxref{Mixed-Language Programming on Windows}).
27552 To create a Microsoft-style import library for @file{API.dll} you
27553 should proceed as follows:
27557 Create the definition file @file{API.def} from the DLL. For this use either
27558 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
27559 tool (see the corresponding Microsoft documentation for further details).
27562 Build the actual import library using Microsoft's @code{lib} utility:
27565 $ lib -machine:IX86 -def:API.def -out:API.lib
27569 If you use the above command the definition file @file{API.def} must
27570 contain a line giving the name of the DLL:
27577 See the Microsoft documentation for further details about the usage of
27581 @node Building DLLs with GNAT
27582 @section Building DLLs with GNAT
27583 @cindex DLLs, building
27586 This section explain how to build DLLs using the GNAT built-in DLL
27587 support. With the following procedure it is straight forward to build
27588 and use DLLs with GNAT.
27592 @item building object files
27594 The first step is to build all objects files that are to be included
27595 into the DLL. This is done by using the standard @command{gnatmake} tool.
27597 @item building the DLL
27599 To build the DLL you must use @command{gcc}'s @option{-shared}
27600 option. It is quite simple to use this method:
27603 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
27606 It is important to note that in this case all symbols found in the
27607 object files are automatically exported. It is possible to restrict
27608 the set of symbols to export by passing to @command{gcc} a definition
27609 file, @pxref{The Definition File}. For example:
27612 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
27615 If you use a definition file you must export the elaboration procedures
27616 for every package that required one. Elaboration procedures are named
27617 using the package name followed by "_E".
27619 @item preparing DLL to be used
27621 For the DLL to be used by client programs the bodies must be hidden
27622 from it and the .ali set with read-only attribute. This is very important
27623 otherwise GNAT will recompile all packages and will not actually use
27624 the code in the DLL. For example:
27628 $ copy *.ads *.ali api.dll apilib
27629 $ attrib +R apilib\*.ali
27634 At this point it is possible to use the DLL by directly linking
27635 against it. Note that you must use the GNAT shared runtime when using
27636 GNAT shared libraries. This is achieved by using @option{-shared} binder's
27640 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
27643 @node Building DLLs with GNAT Project files
27644 @section Building DLLs with GNAT Project files
27645 @cindex DLLs, building
27648 There is nothing specific to Windows in the build process.
27649 @pxref{Library Projects}.
27652 Due to a system limitation, it is not possible under Windows to create threads
27653 when inside the @code{DllMain} routine which is used for auto-initialization
27654 of shared libraries, so it is not possible to have library level tasks in SALs.
27656 @node Building DLLs with gnatdll
27657 @section Building DLLs with gnatdll
27658 @cindex DLLs, building
27661 * Limitations When Using Ada DLLs from Ada::
27662 * Exporting Ada Entities::
27663 * Ada DLLs and Elaboration::
27664 * Ada DLLs and Finalization::
27665 * Creating a Spec for Ada DLLs::
27666 * Creating the Definition File::
27671 Note that it is preferred to use the built-in GNAT DLL support
27672 (@pxref{Building DLLs with GNAT}) or GNAT Project files
27673 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
27675 This section explains how to build DLLs containing Ada code using
27676 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
27677 remainder of this section.
27679 The steps required to build an Ada DLL that is to be used by Ada as well as
27680 non-Ada applications are as follows:
27684 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
27685 @code{Stdcall} calling convention to avoid any Ada name mangling for the
27686 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
27687 skip this step if you plan to use the Ada DLL only from Ada applications.
27690 Your Ada code must export an initialization routine which calls the routine
27691 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
27692 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
27693 routine exported by the Ada DLL must be invoked by the clients of the DLL
27694 to initialize the DLL.
27697 When useful, the DLL should also export a finalization routine which calls
27698 routine @code{adafinal} generated by @command{gnatbind} to perform the
27699 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
27700 The finalization routine exported by the Ada DLL must be invoked by the
27701 clients of the DLL when the DLL services are no further needed.
27704 You must provide a spec for the services exported by the Ada DLL in each
27705 of the programming languages to which you plan to make the DLL available.
27708 You must provide a definition file listing the exported entities
27709 (@pxref{The Definition File}).
27712 Finally you must use @code{gnatdll} to produce the DLL and the import
27713 library (@pxref{Using gnatdll}).
27717 Note that a relocatable DLL stripped using the @code{strip}
27718 binutils tool will not be relocatable anymore. To build a DLL without
27719 debug information pass @code{-largs -s} to @code{gnatdll}. This
27720 restriction does not apply to a DLL built using a Library Project.
27721 @pxref{Library Projects}.
27723 @node Limitations When Using Ada DLLs from Ada
27724 @subsection Limitations When Using Ada DLLs from Ada
27727 When using Ada DLLs from Ada applications there is a limitation users
27728 should be aware of. Because on Windows the GNAT run time is not in a DLL of
27729 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
27730 each Ada DLL includes the services of the GNAT run time that are necessary
27731 to the Ada code inside the DLL. As a result, when an Ada program uses an
27732 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
27733 one in the main program.
27735 It is therefore not possible to exchange GNAT run-time objects between the
27736 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
27737 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
27740 It is completely safe to exchange plain elementary, array or record types,
27741 Windows object handles, etc.
27743 @node Exporting Ada Entities
27744 @subsection Exporting Ada Entities
27745 @cindex Export table
27748 Building a DLL is a way to encapsulate a set of services usable from any
27749 application. As a result, the Ada entities exported by a DLL should be
27750 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
27751 any Ada name mangling. As an example here is an Ada package
27752 @code{API}, spec and body, exporting two procedures, a function, and a
27755 @smallexample @c ada
27758 with Interfaces.C; use Interfaces;
27760 Count : C.int := 0;
27761 function Factorial (Val : C.int) return C.int;
27763 procedure Initialize_API;
27764 procedure Finalize_API;
27765 -- Initialization & Finalization routines. More in the next section.
27767 pragma Export (C, Initialize_API);
27768 pragma Export (C, Finalize_API);
27769 pragma Export (C, Count);
27770 pragma Export (C, Factorial);
27776 @smallexample @c ada
27779 package body API is
27780 function Factorial (Val : C.int) return C.int is
27783 Count := Count + 1;
27784 for K in 1 .. Val loop
27790 procedure Initialize_API is
27792 pragma Import (C, Adainit);
27795 end Initialize_API;
27797 procedure Finalize_API is
27798 procedure Adafinal;
27799 pragma Import (C, Adafinal);
27809 If the Ada DLL you are building will only be used by Ada applications
27810 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
27811 convention. As an example, the previous package could be written as
27814 @smallexample @c ada
27818 Count : Integer := 0;
27819 function Factorial (Val : Integer) return Integer;
27821 procedure Initialize_API;
27822 procedure Finalize_API;
27823 -- Initialization and Finalization routines.
27829 @smallexample @c ada
27832 package body API is
27833 function Factorial (Val : Integer) return Integer is
27834 Fact : Integer := 1;
27836 Count := Count + 1;
27837 for K in 1 .. Val loop
27844 -- The remainder of this package body is unchanged.
27851 Note that if you do not export the Ada entities with a @code{C} or
27852 @code{Stdcall} convention you will have to provide the mangled Ada names
27853 in the definition file of the Ada DLL
27854 (@pxref{Creating the Definition File}).
27856 @node Ada DLLs and Elaboration
27857 @subsection Ada DLLs and Elaboration
27858 @cindex DLLs and elaboration
27861 The DLL that you are building contains your Ada code as well as all the
27862 routines in the Ada library that are needed by it. The first thing a
27863 user of your DLL must do is elaborate the Ada code
27864 (@pxref{Elaboration Order Handling in GNAT}).
27866 To achieve this you must export an initialization routine
27867 (@code{Initialize_API} in the previous example), which must be invoked
27868 before using any of the DLL services. This elaboration routine must call
27869 the Ada elaboration routine @code{adainit} generated by the GNAT binder
27870 (@pxref{Binding with Non-Ada Main Programs}). See the body of
27871 @code{Initialize_Api} for an example. Note that the GNAT binder is
27872 automatically invoked during the DLL build process by the @code{gnatdll}
27873 tool (@pxref{Using gnatdll}).
27875 When a DLL is loaded, Windows systematically invokes a routine called
27876 @code{DllMain}. It would therefore be possible to call @code{adainit}
27877 directly from @code{DllMain} without having to provide an explicit
27878 initialization routine. Unfortunately, it is not possible to call
27879 @code{adainit} from the @code{DllMain} if your program has library level
27880 tasks because access to the @code{DllMain} entry point is serialized by
27881 the system (that is, only a single thread can execute ``through'' it at a
27882 time), which means that the GNAT run time will deadlock waiting for the
27883 newly created task to complete its initialization.
27885 @node Ada DLLs and Finalization
27886 @subsection Ada DLLs and Finalization
27887 @cindex DLLs and finalization
27890 When the services of an Ada DLL are no longer needed, the client code should
27891 invoke the DLL finalization routine, if available. The DLL finalization
27892 routine is in charge of releasing all resources acquired by the DLL. In the
27893 case of the Ada code contained in the DLL, this is achieved by calling
27894 routine @code{adafinal} generated by the GNAT binder
27895 (@pxref{Binding with Non-Ada Main Programs}).
27896 See the body of @code{Finalize_Api} for an
27897 example. As already pointed out the GNAT binder is automatically invoked
27898 during the DLL build process by the @code{gnatdll} tool
27899 (@pxref{Using gnatdll}).
27901 @node Creating a Spec for Ada DLLs
27902 @subsection Creating a Spec for Ada DLLs
27905 To use the services exported by the Ada DLL from another programming
27906 language (e.g.@: C), you have to translate the specs of the exported Ada
27907 entities in that language. For instance in the case of @code{API.dll},
27908 the corresponding C header file could look like:
27913 extern int *_imp__count;
27914 #define count (*_imp__count)
27915 int factorial (int);
27921 It is important to understand that when building an Ada DLL to be used by
27922 other Ada applications, you need two different specs for the packages
27923 contained in the DLL: one for building the DLL and the other for using
27924 the DLL. This is because the @code{DLL} calling convention is needed to
27925 use a variable defined in a DLL, but when building the DLL, the variable
27926 must have either the @code{Ada} or @code{C} calling convention. As an
27927 example consider a DLL comprising the following package @code{API}:
27929 @smallexample @c ada
27933 Count : Integer := 0;
27935 -- Remainder of the package omitted.
27942 After producing a DLL containing package @code{API}, the spec that
27943 must be used to import @code{API.Count} from Ada code outside of the
27946 @smallexample @c ada
27951 pragma Import (DLL, Count);
27957 @node Creating the Definition File
27958 @subsection Creating the Definition File
27961 The definition file is the last file needed to build the DLL. It lists
27962 the exported symbols. As an example, the definition file for a DLL
27963 containing only package @code{API} (where all the entities are exported
27964 with a @code{C} calling convention) is:
27979 If the @code{C} calling convention is missing from package @code{API},
27980 then the definition file contains the mangled Ada names of the above
27981 entities, which in this case are:
27990 api__initialize_api
27995 @node Using gnatdll
27996 @subsection Using @code{gnatdll}
28000 * gnatdll Example::
28001 * gnatdll behind the Scenes::
28006 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
28007 and non-Ada sources that make up your DLL have been compiled.
28008 @code{gnatdll} is actually in charge of two distinct tasks: build the
28009 static import library for the DLL and the actual DLL. The form of the
28010 @code{gnatdll} command is
28014 @c $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
28015 @c Expanding @ovar macro inline (explanation in macro def comments)
28016 $ gnatdll @r{[}@var{switches}@r{]} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
28021 where @var{list-of-files} is a list of ALI and object files. The object
28022 file list must be the exact list of objects corresponding to the non-Ada
28023 sources whose services are to be included in the DLL. The ALI file list
28024 must be the exact list of ALI files for the corresponding Ada sources
28025 whose services are to be included in the DLL. If @var{list-of-files} is
28026 missing, only the static import library is generated.
28029 You may specify any of the following switches to @code{gnatdll}:
28032 @c @item -a@ovar{address}
28033 @c Expanding @ovar macro inline (explanation in macro def comments)
28034 @item -a@r{[}@var{address}@r{]}
28035 @cindex @option{-a} (@code{gnatdll})
28036 Build a non-relocatable DLL at @var{address}. If @var{address} is not
28037 specified the default address @var{0x11000000} will be used. By default,
28038 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
28039 advise the reader to build relocatable DLL.
28041 @item -b @var{address}
28042 @cindex @option{-b} (@code{gnatdll})
28043 Set the relocatable DLL base address. By default the address is
28046 @item -bargs @var{opts}
28047 @cindex @option{-bargs} (@code{gnatdll})
28048 Binder options. Pass @var{opts} to the binder.
28050 @item -d @var{dllfile}
28051 @cindex @option{-d} (@code{gnatdll})
28052 @var{dllfile} is the name of the DLL. This switch must be present for
28053 @code{gnatdll} to do anything. The name of the generated import library is
28054 obtained algorithmically from @var{dllfile} as shown in the following
28055 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
28056 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
28057 by option @option{-e}) is obtained algorithmically from @var{dllfile}
28058 as shown in the following example:
28059 if @var{dllfile} is @code{xyz.dll}, the definition
28060 file used is @code{xyz.def}.
28062 @item -e @var{deffile}
28063 @cindex @option{-e} (@code{gnatdll})
28064 @var{deffile} is the name of the definition file.
28067 @cindex @option{-g} (@code{gnatdll})
28068 Generate debugging information. This information is stored in the object
28069 file and copied from there to the final DLL file by the linker,
28070 where it can be read by the debugger. You must use the
28071 @option{-g} switch if you plan on using the debugger or the symbolic
28075 @cindex @option{-h} (@code{gnatdll})
28076 Help mode. Displays @code{gnatdll} switch usage information.
28079 @cindex @option{-I} (@code{gnatdll})
28080 Direct @code{gnatdll} to search the @var{dir} directory for source and
28081 object files needed to build the DLL.
28082 (@pxref{Search Paths and the Run-Time Library (RTL)}).
28085 @cindex @option{-k} (@code{gnatdll})
28086 Removes the @code{@@}@var{nn} suffix from the import library's exported
28087 names, but keeps them for the link names. You must specify this
28088 option if you want to use a @code{Stdcall} function in a DLL for which
28089 the @code{@@}@var{nn} suffix has been removed. This is the case for most
28090 of the Windows NT DLL for example. This option has no effect when
28091 @option{-n} option is specified.
28093 @item -l @var{file}
28094 @cindex @option{-l} (@code{gnatdll})
28095 The list of ALI and object files used to build the DLL are listed in
28096 @var{file}, instead of being given in the command line. Each line in
28097 @var{file} contains the name of an ALI or object file.
28100 @cindex @option{-n} (@code{gnatdll})
28101 No Import. Do not create the import library.
28104 @cindex @option{-q} (@code{gnatdll})
28105 Quiet mode. Do not display unnecessary messages.
28108 @cindex @option{-v} (@code{gnatdll})
28109 Verbose mode. Display extra information.
28111 @item -largs @var{opts}
28112 @cindex @option{-largs} (@code{gnatdll})
28113 Linker options. Pass @var{opts} to the linker.
28116 @node gnatdll Example
28117 @subsubsection @code{gnatdll} Example
28120 As an example the command to build a relocatable DLL from @file{api.adb}
28121 once @file{api.adb} has been compiled and @file{api.def} created is
28124 $ gnatdll -d api.dll api.ali
28128 The above command creates two files: @file{libapi.dll.a} (the import
28129 library) and @file{api.dll} (the actual DLL). If you want to create
28130 only the DLL, just type:
28133 $ gnatdll -d api.dll -n api.ali
28137 Alternatively if you want to create just the import library, type:
28140 $ gnatdll -d api.dll
28143 @node gnatdll behind the Scenes
28144 @subsubsection @code{gnatdll} behind the Scenes
28147 This section details the steps involved in creating a DLL. @code{gnatdll}
28148 does these steps for you. Unless you are interested in understanding what
28149 goes on behind the scenes, you should skip this section.
28151 We use the previous example of a DLL containing the Ada package @code{API},
28152 to illustrate the steps necessary to build a DLL. The starting point is a
28153 set of objects that will make up the DLL and the corresponding ALI
28154 files. In the case of this example this means that @file{api.o} and
28155 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
28160 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
28161 the information necessary to generate relocation information for the
28167 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
28172 In addition to the base file, the @command{gnatlink} command generates an
28173 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
28174 asks @command{gnatlink} to generate the routines @code{DllMain} and
28175 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
28176 is loaded into memory.
28179 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
28180 export table (@file{api.exp}). The export table contains the relocation
28181 information in a form which can be used during the final link to ensure
28182 that the Windows loader is able to place the DLL anywhere in memory.
28186 $ dlltool --dllname api.dll --def api.def --base-file api.base \
28187 --output-exp api.exp
28192 @code{gnatdll} builds the base file using the new export table. Note that
28193 @command{gnatbind} must be called once again since the binder generated file
28194 has been deleted during the previous call to @command{gnatlink}.
28199 $ gnatlink api -o api.jnk api.exp -mdll
28200 -Wl,--base-file,api.base
28205 @code{gnatdll} builds the new export table using the new base file and
28206 generates the DLL import library @file{libAPI.dll.a}.
28210 $ dlltool --dllname api.dll --def api.def --base-file api.base \
28211 --output-exp api.exp --output-lib libAPI.a
28216 Finally @code{gnatdll} builds the relocatable DLL using the final export
28222 $ gnatlink api api.exp -o api.dll -mdll
28227 @node Using dlltool
28228 @subsubsection Using @code{dlltool}
28231 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
28232 DLLs and static import libraries. This section summarizes the most
28233 common @code{dlltool} switches. The form of the @code{dlltool} command
28237 @c $ dlltool @ovar{switches}
28238 @c Expanding @ovar macro inline (explanation in macro def comments)
28239 $ dlltool @r{[}@var{switches}@r{]}
28243 @code{dlltool} switches include:
28246 @item --base-file @var{basefile}
28247 @cindex @option{--base-file} (@command{dlltool})
28248 Read the base file @var{basefile} generated by the linker. This switch
28249 is used to create a relocatable DLL.
28251 @item --def @var{deffile}
28252 @cindex @option{--def} (@command{dlltool})
28253 Read the definition file.
28255 @item --dllname @var{name}
28256 @cindex @option{--dllname} (@command{dlltool})
28257 Gives the name of the DLL. This switch is used to embed the name of the
28258 DLL in the static import library generated by @code{dlltool} with switch
28259 @option{--output-lib}.
28262 @cindex @option{-k} (@command{dlltool})
28263 Kill @code{@@}@var{nn} from exported names
28264 (@pxref{Windows Calling Conventions}
28265 for a discussion about @code{Stdcall}-style symbols.
28268 @cindex @option{--help} (@command{dlltool})
28269 Prints the @code{dlltool} switches with a concise description.
28271 @item --output-exp @var{exportfile}
28272 @cindex @option{--output-exp} (@command{dlltool})
28273 Generate an export file @var{exportfile}. The export file contains the
28274 export table (list of symbols in the DLL) and is used to create the DLL.
28276 @item --output-lib @var{libfile}
28277 @cindex @option{--output-lib} (@command{dlltool})
28278 Generate a static import library @var{libfile}.
28281 @cindex @option{-v} (@command{dlltool})
28284 @item --as @var{assembler-name}
28285 @cindex @option{--as} (@command{dlltool})
28286 Use @var{assembler-name} as the assembler. The default is @code{as}.
28289 @node GNAT and Windows Resources
28290 @section GNAT and Windows Resources
28291 @cindex Resources, windows
28294 * Building Resources::
28295 * Compiling Resources::
28296 * Using Resources::
28300 Resources are an easy way to add Windows specific objects to your
28301 application. The objects that can be added as resources include:
28330 This section explains how to build, compile and use resources.
28332 @node Building Resources
28333 @subsection Building Resources
28334 @cindex Resources, building
28337 A resource file is an ASCII file. By convention resource files have an
28338 @file{.rc} extension.
28339 The easiest way to build a resource file is to use Microsoft tools
28340 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
28341 @code{dlgedit.exe} to build dialogs.
28342 It is always possible to build an @file{.rc} file yourself by writing a
28345 It is not our objective to explain how to write a resource file. A
28346 complete description of the resource script language can be found in the
28347 Microsoft documentation.
28349 @node Compiling Resources
28350 @subsection Compiling Resources
28353 @cindex Resources, compiling
28356 This section describes how to build a GNAT-compatible (COFF) object file
28357 containing the resources. This is done using the Resource Compiler
28358 @code{windres} as follows:
28361 $ windres -i myres.rc -o myres.o
28365 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
28366 file. You can specify an alternate preprocessor (usually named
28367 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
28368 parameter. A list of all possible options may be obtained by entering
28369 the command @code{windres} @option{--help}.
28371 It is also possible to use the Microsoft resource compiler @code{rc.exe}
28372 to produce a @file{.res} file (binary resource file). See the
28373 corresponding Microsoft documentation for further details. In this case
28374 you need to use @code{windres} to translate the @file{.res} file to a
28375 GNAT-compatible object file as follows:
28378 $ windres -i myres.res -o myres.o
28381 @node Using Resources
28382 @subsection Using Resources
28383 @cindex Resources, using
28386 To include the resource file in your program just add the
28387 GNAT-compatible object file for the resource(s) to the linker
28388 arguments. With @command{gnatmake} this is done by using the @option{-largs}
28392 $ gnatmake myprog -largs myres.o
28395 @node Debugging a DLL
28396 @section Debugging a DLL
28397 @cindex DLL debugging
28400 * Program and DLL Both Built with GCC/GNAT::
28401 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
28405 Debugging a DLL is similar to debugging a standard program. But
28406 we have to deal with two different executable parts: the DLL and the
28407 program that uses it. We have the following four possibilities:
28411 The program and the DLL are built with @code{GCC/GNAT}.
28413 The program is built with foreign tools and the DLL is built with
28416 The program is built with @code{GCC/GNAT} and the DLL is built with
28422 In this section we address only cases one and two above.
28423 There is no point in trying to debug
28424 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
28425 information in it. To do so you must use a debugger compatible with the
28426 tools suite used to build the DLL.
28428 @node Program and DLL Both Built with GCC/GNAT
28429 @subsection Program and DLL Both Built with GCC/GNAT
28432 This is the simplest case. Both the DLL and the program have @code{GDB}
28433 compatible debugging information. It is then possible to break anywhere in
28434 the process. Let's suppose here that the main procedure is named
28435 @code{ada_main} and that in the DLL there is an entry point named
28439 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
28440 program must have been built with the debugging information (see GNAT -g
28441 switch). Here are the step-by-step instructions for debugging it:
28444 @item Launch @code{GDB} on the main program.
28450 @item Start the program and stop at the beginning of the main procedure
28457 This step is required to be able to set a breakpoint inside the DLL. As long
28458 as the program is not run, the DLL is not loaded. This has the
28459 consequence that the DLL debugging information is also not loaded, so it is not
28460 possible to set a breakpoint in the DLL.
28462 @item Set a breakpoint inside the DLL
28465 (gdb) break ada_dll
28472 At this stage a breakpoint is set inside the DLL. From there on
28473 you can use the standard approach to debug the whole program
28474 (@pxref{Running and Debugging Ada Programs}).
28477 @c This used to work, probably because the DLLs were non-relocatable
28478 @c keep this section around until the problem is sorted out.
28480 To break on the @code{DllMain} routine it is not possible to follow
28481 the procedure above. At the time the program stop on @code{ada_main}
28482 the @code{DllMain} routine as already been called. Either you can use
28483 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
28486 @item Launch @code{GDB} on the main program.
28492 @item Load DLL symbols
28495 (gdb) add-sym api.dll
28498 @item Set a breakpoint inside the DLL
28501 (gdb) break ada_dll.adb:45
28504 Note that at this point it is not possible to break using the routine symbol
28505 directly as the program is not yet running. The solution is to break
28506 on the proper line (break in @file{ada_dll.adb} line 45).
28508 @item Start the program
28517 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
28518 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
28521 * Debugging the DLL Directly::
28522 * Attaching to a Running Process::
28526 In this case things are slightly more complex because it is not possible to
28527 start the main program and then break at the beginning to load the DLL and the
28528 associated DLL debugging information. It is not possible to break at the
28529 beginning of the program because there is no @code{GDB} debugging information,
28530 and therefore there is no direct way of getting initial control. This
28531 section addresses this issue by describing some methods that can be used
28532 to break somewhere in the DLL to debug it.
28535 First suppose that the main procedure is named @code{main} (this is for
28536 example some C code built with Microsoft Visual C) and that there is a
28537 DLL named @code{test.dll} containing an Ada entry point named
28541 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
28542 been built with debugging information (see GNAT -g option).
28544 @node Debugging the DLL Directly
28545 @subsubsection Debugging the DLL Directly
28549 Find out the executable starting address
28552 $ objdump --file-header main.exe
28555 The starting address is reported on the last line. For example:
28558 main.exe: file format pei-i386
28559 architecture: i386, flags 0x0000010a:
28560 EXEC_P, HAS_DEBUG, D_PAGED
28561 start address 0x00401010
28565 Launch the debugger on the executable.
28572 Set a breakpoint at the starting address, and launch the program.
28575 $ (gdb) break *0x00401010
28579 The program will stop at the given address.
28582 Set a breakpoint on a DLL subroutine.
28585 (gdb) break ada_dll.adb:45
28588 Or if you want to break using a symbol on the DLL, you need first to
28589 select the Ada language (language used by the DLL).
28592 (gdb) set language ada
28593 (gdb) break ada_dll
28597 Continue the program.
28604 This will run the program until it reaches the breakpoint that has been
28605 set. From that point you can use the standard way to debug a program
28606 as described in (@pxref{Running and Debugging Ada Programs}).
28611 It is also possible to debug the DLL by attaching to a running process.
28613 @node Attaching to a Running Process
28614 @subsubsection Attaching to a Running Process
28615 @cindex DLL debugging, attach to process
28618 With @code{GDB} it is always possible to debug a running process by
28619 attaching to it. It is possible to debug a DLL this way. The limitation
28620 of this approach is that the DLL must run long enough to perform the
28621 attach operation. It may be useful for instance to insert a time wasting
28622 loop in the code of the DLL to meet this criterion.
28626 @item Launch the main program @file{main.exe}.
28632 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
28633 that the process PID for @file{main.exe} is 208.
28641 @item Attach to the running process to be debugged.
28647 @item Load the process debugging information.
28650 (gdb) symbol-file main.exe
28653 @item Break somewhere in the DLL.
28656 (gdb) break ada_dll
28659 @item Continue process execution.
28668 This last step will resume the process execution, and stop at
28669 the breakpoint we have set. From there you can use the standard
28670 approach to debug a program as described in
28671 (@pxref{Running and Debugging Ada Programs}).
28673 @node Setting Stack Size from gnatlink
28674 @section Setting Stack Size from @command{gnatlink}
28677 It is possible to specify the program stack size at link time. On modern
28678 versions of Windows, starting with XP, this is mostly useful to set the size of
28679 the main stack (environment task). The other task stacks are set with pragma
28680 Storage_Size or with the @command{gnatbind -d} command.
28682 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
28683 reserve size of individual tasks, the link-time stack size applies to all
28684 tasks, and pragma Storage_Size has no effect.
28685 In particular, Stack Overflow checks are made against this
28686 link-time specified size.
28688 This setting can be done with
28689 @command{gnatlink} using either:
28693 @item using @option{-Xlinker} linker option
28696 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
28699 This sets the stack reserve size to 0x10000 bytes and the stack commit
28700 size to 0x1000 bytes.
28702 @item using @option{-Wl} linker option
28705 $ gnatlink hello -Wl,--stack=0x1000000
28708 This sets the stack reserve size to 0x1000000 bytes. Note that with
28709 @option{-Wl} option it is not possible to set the stack commit size
28710 because the coma is a separator for this option.
28714 @node Setting Heap Size from gnatlink
28715 @section Setting Heap Size from @command{gnatlink}
28718 Under Windows systems, it is possible to specify the program heap size from
28719 @command{gnatlink} using either:
28723 @item using @option{-Xlinker} linker option
28726 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
28729 This sets the heap reserve size to 0x10000 bytes and the heap commit
28730 size to 0x1000 bytes.
28732 @item using @option{-Wl} linker option
28735 $ gnatlink hello -Wl,--heap=0x1000000
28738 This sets the heap reserve size to 0x1000000 bytes. Note that with
28739 @option{-Wl} option it is not possible to set the heap commit size
28740 because the coma is a separator for this option.
28746 @c **********************************
28747 @c * GNU Free Documentation License *
28748 @c **********************************
28750 @c GNU Free Documentation License
28752 @node Index,,GNU Free Documentation License, Top
28758 @c Put table of contents at end, otherwise it precedes the "title page" in
28759 @c the .txt version
28760 @c Edit the pdf file to move the contents to the beginning, after the title