1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
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14 @setfilename gnat_ugn.info
17 Copyright @copyright{} 1995-2005, 2006, 2007, 2008 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.2 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
71 @c cause the document build to fail.
73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
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84 @c This flag is used where the text refers to conditions that exist when the
85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * Other Utility Programs::
191 * Running and Debugging Ada Programs::
193 * Code Coverage and Profiling::
196 * Compatibility with HP Ada::
198 * Platform-Specific Information for the Run-Time Libraries::
199 * Example of Binder Output File::
200 * Elaboration Order Handling in GNAT::
201 * Conditional Compilation::
203 * Compatibility and Porting Guide::
205 * Microsoft Windows Topics::
207 * GNU Free Documentation License::
210 --- The Detailed Node Listing ---
214 * What This Guide Contains::
215 * What You Should Know before Reading This Guide::
216 * Related Information::
219 Getting Started with GNAT
222 * Running a Simple Ada Program::
223 * Running a Program with Multiple Units::
224 * Using the gnatmake Utility::
226 * Editing with Emacs::
229 * Introduction to GPS::
232 The GNAT Compilation Model
234 * Source Representation::
235 * Foreign Language Representation::
236 * File Naming Rules::
237 * Using Other File Names::
238 * Alternative File Naming Schemes::
239 * Generating Object Files::
240 * Source Dependencies::
241 * The Ada Library Information Files::
242 * Binding an Ada Program::
243 * Mixed Language Programming::
245 * Building Mixed Ada & C++ Programs::
246 * Comparison between GNAT and C/C++ Compilation Models::
248 * Comparison between GNAT and Conventional Ada Library Models::
250 * Placement of temporary files::
253 Foreign Language Representation
256 * Other 8-Bit Codes::
257 * Wide Character Encodings::
259 Compiling Ada Programs With gcc
261 * Compiling Programs::
263 * Search Paths and the Run-Time Library (RTL)::
264 * Order of Compilation Issues::
269 * Output and Error Message Control::
270 * Warning Message Control::
271 * Debugging and Assertion Control::
272 * Validity Checking::
275 * Using gcc for Syntax Checking::
276 * Using gcc for Semantic Checking::
277 * Compiling Different Versions of Ada::
278 * Character Set Control::
279 * File Naming Control::
280 * Subprogram Inlining Control::
281 * Auxiliary Output Control::
282 * Debugging Control::
283 * Exception Handling Control::
284 * Units to Sources Mapping Files::
285 * Integrated Preprocessing::
290 Binding Ada Programs With gnatbind
293 * Switches for gnatbind::
294 * Command-Line Access::
295 * Search Paths for gnatbind::
296 * Examples of gnatbind Usage::
298 Switches for gnatbind
300 * Consistency-Checking Modes::
301 * Binder Error Message Control::
302 * Elaboration Control::
304 * Binding with Non-Ada Main Programs::
305 * Binding Programs with No Main Subprogram::
307 Linking Using gnatlink
310 * Switches for gnatlink::
312 The GNAT Make Program gnatmake
315 * Switches for gnatmake::
316 * Mode Switches for gnatmake::
317 * Notes on the Command Line::
318 * How gnatmake Works::
319 * Examples of gnatmake Usage::
321 Improving Performance
322 * Performance Considerations::
323 * Text_IO Suggestions::
324 * Reducing Size of Ada Executables with gnatelim::
325 * Reducing Size of Executables with unused subprogram/data elimination::
327 Performance Considerations
328 * Controlling Run-Time Checks::
329 * Use of Restrictions::
330 * Optimization Levels::
331 * Debugging Optimized Code::
332 * Inlining of Subprograms::
333 * Other Optimization Switches::
334 * Optimization and Strict Aliasing::
336 * Coverage Analysis::
339 Reducing Size of Ada Executables with gnatelim
342 * Correcting the List of Eliminate Pragmas::
343 * Making Your Executables Smaller::
344 * Summary of the gnatelim Usage Cycle::
346 Reducing Size of Executables with unused subprogram/data elimination
347 * About unused subprogram/data elimination::
348 * Compilation options::
350 Renaming Files Using gnatchop
352 * Handling Files with Multiple Units::
353 * Operating gnatchop in Compilation Mode::
354 * Command Line for gnatchop::
355 * Switches for gnatchop::
356 * Examples of gnatchop Usage::
358 Configuration Pragmas
360 * Handling of Configuration Pragmas::
361 * The Configuration Pragmas Files::
363 Handling Arbitrary File Naming Conventions Using gnatname
365 * Arbitrary File Naming Conventions::
367 * Switches for gnatname::
368 * Examples of gnatname Usage::
373 * Examples of Project Files::
374 * Project File Syntax::
375 * Objects and Sources in Project Files::
376 * Importing Projects::
377 * Project Extension::
378 * Project Hierarchy Extension::
379 * External References in Project Files::
380 * Packages in Project Files::
381 * Variables from Imported Projects::
384 * Stand-alone Library Projects::
385 * Switches Related to Project Files::
386 * Tools Supporting Project Files::
387 * An Extended Example::
388 * Project File Complete Syntax::
390 The Cross-Referencing Tools gnatxref and gnatfind
392 * gnatxref Switches::
393 * gnatfind Switches::
394 * Project Files for gnatxref and gnatfind::
395 * Regular Expressions in gnatfind and gnatxref::
396 * Examples of gnatxref Usage::
397 * Examples of gnatfind Usage::
399 The GNAT Pretty-Printer gnatpp
401 * Switches for gnatpp::
404 The GNAT Metrics Tool gnatmetric
406 * Switches for gnatmetric::
408 File Name Krunching Using gnatkr
413 * Examples of gnatkr Usage::
415 Preprocessing Using gnatprep
416 * Preprocessing Symbols::
418 * Switches for gnatprep::
419 * Form of Definitions File::
420 * Form of Input Text for gnatprep::
423 The GNAT Run-Time Library Builder gnatlbr
426 * Switches for gnatlbr::
427 * Examples of gnatlbr Usage::
430 The GNAT Library Browser gnatls
433 * Switches for gnatls::
434 * Examples of gnatls Usage::
436 Cleaning Up Using gnatclean
438 * Running gnatclean::
439 * Switches for gnatclean::
440 @c * Examples of gnatclean Usage::
446 * Introduction to Libraries in GNAT::
447 * General Ada Libraries::
448 * Stand-alone Ada Libraries::
449 * Rebuilding the GNAT Run-Time Library::
451 Using the GNU make Utility
453 * Using gnatmake in a Makefile::
454 * Automatically Creating a List of Directories::
455 * Generating the Command Line Switches::
456 * Overcoming Command Line Length Limits::
459 Memory Management Issues
461 * Some Useful Memory Pools::
462 * The GNAT Debug Pool Facility::
467 Stack Related Facilities
469 * Stack Overflow Checking::
470 * Static Stack Usage Analysis::
471 * Dynamic Stack Usage Analysis::
473 Some Useful Memory Pools
475 The GNAT Debug Pool Facility
481 * Switches for gnatmem::
482 * Example of gnatmem Usage::
485 Verifying Properties Using gnatcheck
487 * Format of the Report File::
488 * General gnatcheck Switches::
489 * gnatcheck Rule Options::
490 * Adding the Results of Compiler Checks to gnatcheck Output::
491 * Project-Wide Checks::
494 Sample Bodies Using gnatstub
497 * Switches for gnatstub::
499 Other Utility Programs
501 * Using Other Utility Programs with GNAT::
502 * The External Symbol Naming Scheme of GNAT::
503 * Converting Ada Files to html with gnathtml::
506 Code Coverage and Profiling
508 * Code Coverage of Ada Programs using gcov::
509 * Profiling an Ada Program using gprof::
512 Running and Debugging Ada Programs
514 * The GNAT Debugger GDB::
516 * Introduction to GDB Commands::
517 * Using Ada Expressions::
518 * Calling User-Defined Subprograms::
519 * Using the Next Command in a Function::
522 * Debugging Generic Units::
523 * GNAT Abnormal Termination or Failure to Terminate::
524 * Naming Conventions for GNAT Source Files::
525 * Getting Internal Debugging Information::
533 Compatibility with HP Ada
535 * Ada Language Compatibility::
536 * Differences in the Definition of Package System::
537 * Language-Related Features::
538 * The Package STANDARD::
539 * The Package SYSTEM::
540 * Tasking and Task-Related Features::
541 * Pragmas and Pragma-Related Features::
542 * Library of Predefined Units::
544 * Main Program Definition::
545 * Implementation-Defined Attributes::
546 * Compiler and Run-Time Interfacing::
547 * Program Compilation and Library Management::
549 * Implementation Limits::
550 * Tools and Utilities::
552 Language-Related Features
554 * Integer Types and Representations::
555 * Floating-Point Types and Representations::
556 * Pragmas Float_Representation and Long_Float::
557 * Fixed-Point Types and Representations::
558 * Record and Array Component Alignment::
560 * Other Representation Clauses::
562 Tasking and Task-Related Features
564 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
565 * Assigning Task IDs::
566 * Task IDs and Delays::
567 * Task-Related Pragmas::
568 * Scheduling and Task Priority::
570 * External Interrupts::
572 Pragmas and Pragma-Related Features
574 * Restrictions on the Pragma INLINE::
575 * Restrictions on the Pragma INTERFACE::
576 * Restrictions on the Pragma SYSTEM_NAME::
578 Library of Predefined Units
580 * Changes to DECLIB::
584 * Shared Libraries and Options Files::
588 Platform-Specific Information for the Run-Time Libraries
590 * Summary of Run-Time Configurations::
591 * Specifying a Run-Time Library::
592 * Choosing the Scheduling Policy::
593 * Solaris-Specific Considerations::
594 * Linux-Specific Considerations::
595 * AIX-Specific Considerations::
596 * Irix-Specific Considerations::
598 Example of Binder Output File
600 Elaboration Order Handling in GNAT
603 * Checking the Elaboration Order::
604 * Controlling the Elaboration Order::
605 * Controlling Elaboration in GNAT - Internal Calls::
606 * Controlling Elaboration in GNAT - External Calls::
607 * Default Behavior in GNAT - Ensuring Safety::
608 * Treatment of Pragma Elaborate::
609 * Elaboration Issues for Library Tasks::
610 * Mixing Elaboration Models::
611 * What to Do If the Default Elaboration Behavior Fails::
612 * Elaboration for Access-to-Subprogram Values::
613 * Summary of Procedures for Elaboration Control::
614 * Other Elaboration Order Considerations::
616 Conditional Compilation
617 * Use of Boolean Constants::
618 * Debugging - A Special Case::
619 * Conditionalizing Declarations::
620 * Use of Alternative Implementations::
625 * Basic Assembler Syntax::
626 * A Simple Example of Inline Assembler::
627 * Output Variables in Inline Assembler::
628 * Input Variables in Inline Assembler::
629 * Inlining Inline Assembler Code::
630 * Other Asm Functionality::
632 Compatibility and Porting Guide
634 * Compatibility with Ada 83::
635 * Compatibility between Ada 95 and Ada 2005::
636 * Implementation-dependent characteristics::
638 @c This brief section is only in the non-VMS version
639 @c The complete chapter on HP Ada issues is in the VMS version
640 * Compatibility with HP Ada 83::
642 * Compatibility with Other Ada Systems::
643 * Representation Clauses::
645 * Transitioning to 64-Bit GNAT for OpenVMS::
649 Microsoft Windows Topics
651 * Using GNAT on Windows::
652 * CONSOLE and WINDOWS subsystems::
654 * Mixed-Language Programming on Windows::
655 * Windows Calling Conventions::
656 * Introduction to Dynamic Link Libraries (DLLs)::
657 * Using DLLs with GNAT::
658 * Building DLLs with GNAT::
659 * GNAT and Windows Resources::
661 * Setting Stack Size from gnatlink::
662 * Setting Heap Size from gnatlink::
669 @node About This Guide
670 @unnumbered About This Guide
674 This guide describes the use of @value{EDITION},
675 a compiler and software development toolset for the full Ada
676 programming language, implemented on OpenVMS for HP's Alpha and
677 Integrity server (I64) platforms.
680 This guide describes the use of @value{EDITION},
681 a compiler and software development
682 toolset for the full Ada programming language.
684 It documents the features of the compiler and tools, and explains
685 how to use them to build Ada applications.
687 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
688 Ada 83 compatibility mode.
689 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
690 but you can override with a compiler switch
691 (@pxref{Compiling Different Versions of Ada})
692 to explicitly specify the language version.
693 Throughout this manual, references to ``Ada'' without a year suffix
694 apply to both the Ada 95 and Ada 2005 versions of the language.
698 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
699 ``GNAT'' in the remainder of this document.
706 * What This Guide Contains::
707 * What You Should Know before Reading This Guide::
708 * Related Information::
712 @node What This Guide Contains
713 @unnumberedsec What This Guide Contains
716 This guide contains the following chapters:
720 @ref{Getting Started with GNAT}, describes how to get started compiling
721 and running Ada programs with the GNAT Ada programming environment.
723 @ref{The GNAT Compilation Model}, describes the compilation model used
727 @ref{Compiling Using gcc}, describes how to compile
728 Ada programs with @command{gcc}, the Ada compiler.
731 @ref{Binding Using gnatbind}, describes how to
732 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
736 @ref{Linking Using gnatlink},
737 describes @command{gnatlink}, a
738 program that provides for linking using the GNAT run-time library to
739 construct a program. @command{gnatlink} can also incorporate foreign language
740 object units into the executable.
743 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
744 utility that automatically determines the set of sources
745 needed by an Ada compilation unit, and executes the necessary compilations
749 @ref{Improving Performance}, shows various techniques for making your
750 Ada program run faster or take less space.
751 It discusses the effect of the compiler's optimization switch and
752 also describes the @command{gnatelim} tool and unused subprogram/data
756 @ref{Renaming Files Using gnatchop}, describes
757 @code{gnatchop}, a utility that allows you to preprocess a file that
758 contains Ada source code, and split it into one or more new files, one
759 for each compilation unit.
762 @ref{Configuration Pragmas}, describes the configuration pragmas
766 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
767 shows how to override the default GNAT file naming conventions,
768 either for an individual unit or globally.
771 @ref{GNAT Project Manager}, describes how to use project files
772 to organize large projects.
775 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
776 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
777 way to navigate through sources.
780 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
781 version of an Ada source file with control over casing, indentation,
782 comment placement, and other elements of program presentation style.
785 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
786 metrics for an Ada source file, such as the number of types and subprograms,
787 and assorted complexity measures.
790 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
791 file name krunching utility, used to handle shortened
792 file names on operating systems with a limit on the length of names.
795 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
796 preprocessor utility that allows a single source file to be used to
797 generate multiple or parameterized source files by means of macro
802 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
803 a tool for rebuilding the GNAT run time with user-supplied
804 configuration pragmas.
808 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
809 utility that displays information about compiled units, including dependences
810 on the corresponding sources files, and consistency of compilations.
813 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
814 to delete files that are produced by the compiler, binder and linker.
818 @ref{GNAT and Libraries}, describes the process of creating and using
819 Libraries with GNAT. It also describes how to recompile the GNAT run-time
823 @ref{Using the GNU make Utility}, describes some techniques for using
824 the GNAT toolset in Makefiles.
828 @ref{Memory Management Issues}, describes some useful predefined storage pools
829 and in particular the GNAT Debug Pool facility, which helps detect incorrect
832 It also describes @command{gnatmem}, a utility that monitors dynamic
833 allocation and deallocation and helps detect ``memory leaks''.
837 @ref{Stack Related Facilities}, describes some useful tools associated with
838 stack checking and analysis.
841 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
842 a utility that checks Ada code against a set of rules.
845 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
846 a utility that generates empty but compilable bodies for library units.
849 @ref{Other Utility Programs}, discusses several other GNAT utilities,
850 including @code{gnathtml}.
854 @ref{Code Coverage and Profiling}, describes how to perform a structural
855 coverage and profile the execution of Ada programs.
859 @ref{Running and Debugging Ada Programs}, describes how to run and debug
864 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
865 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
866 developed by Digital Equipment Corporation and currently supported by HP.}
867 for OpenVMS Alpha. This product was formerly known as DEC Ada,
870 historical compatibility reasons, the relevant libraries still use the
875 @ref{Platform-Specific Information for the Run-Time Libraries},
876 describes the various run-time
877 libraries supported by GNAT on various platforms and explains how to
878 choose a particular library.
881 @ref{Example of Binder Output File}, shows the source code for the binder
882 output file for a sample program.
885 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
886 you deal with elaboration order issues.
889 @ref{Conditional Compilation}, describes how to model conditional compilation,
890 both with Ada in general and with GNAT facilities in particular.
893 @ref{Inline Assembler}, shows how to use the inline assembly facility
897 @ref{Compatibility and Porting Guide}, contains sections on compatibility
898 of GNAT with other Ada development environments (including Ada 83 systems),
899 to assist in porting code from those environments.
903 @ref{Microsoft Windows Topics}, presents information relevant to the
904 Microsoft Windows platform.
908 @c *************************************************
909 @node What You Should Know before Reading This Guide
910 @c *************************************************
911 @unnumberedsec What You Should Know before Reading This Guide
913 @cindex Ada 95 Language Reference Manual
914 @cindex Ada 2005 Language Reference Manual
916 This guide assumes a basic familiarity with the Ada 95 language, as
917 described in the International Standard ANSI/ISO/IEC-8652:1995, January
919 It does not require knowledge of the new features introduced by Ada 2005,
920 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
922 Both reference manuals are included in the GNAT documentation
925 @node Related Information
926 @unnumberedsec Related Information
929 For further information about related tools, refer to the following
934 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
935 Reference Manual}, which contains all reference material for the GNAT
936 implementation of Ada.
940 @cite{Using the GNAT Programming Studio}, which describes the GPS
941 Integrated Development Environment.
944 @cite{GNAT Programming Studio Tutorial}, which introduces the
945 main GPS features through examples.
949 @cite{Ada 95 Reference Manual}, which contains reference
950 material for the Ada 95 programming language.
953 @cite{Ada 2005 Reference Manual}, which contains reference
954 material for the Ada 2005 programming language.
957 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
959 in the GNU:[DOCS] directory,
961 for all details on the use of the GNU source-level debugger.
964 @xref{Top,, The extensible self-documenting text editor, emacs,
967 located in the GNU:[DOCS] directory if the EMACS kit is installed,
969 for full information on the extensible editor and programming
976 @unnumberedsec Conventions
978 @cindex Typographical conventions
981 Following are examples of the typographical and graphic conventions used
986 @code{Functions}, @command{utility program names}, @code{standard names},
990 @option{Option flags}
993 @file{File names}, @samp{button names}, and @samp{field names}.
996 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1003 @r{[}optional information or parameters@r{]}
1006 Examples are described by text
1008 and then shown this way.
1013 Commands that are entered by the user are preceded in this manual by the
1014 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1015 uses this sequence as a prompt, then the commands will appear exactly as
1016 you see them in the manual. If your system uses some other prompt, then
1017 the command will appear with the @code{$} replaced by whatever prompt
1018 character you are using.
1021 Full file names are shown with the ``@code{/}'' character
1022 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1023 If you are using GNAT on a Windows platform, please note that
1024 the ``@code{\}'' character should be used instead.
1027 @c ****************************
1028 @node Getting Started with GNAT
1029 @chapter Getting Started with GNAT
1032 This chapter describes some simple ways of using GNAT to build
1033 executable Ada programs.
1035 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1036 show how to use the command line environment.
1037 @ref{Introduction to GPS}, provides a brief
1038 introduction to the GNAT Programming Studio, a visually-oriented
1039 Integrated Development Environment for GNAT.
1040 GPS offers a graphical ``look and feel'', support for development in
1041 other programming languages, comprehensive browsing features, and
1042 many other capabilities.
1043 For information on GPS please refer to
1044 @cite{Using the GNAT Programming Studio}.
1049 * Running a Simple Ada Program::
1050 * Running a Program with Multiple Units::
1051 * Using the gnatmake Utility::
1053 * Editing with Emacs::
1056 * Introduction to GPS::
1061 @section Running GNAT
1064 Three steps are needed to create an executable file from an Ada source
1069 The source file(s) must be compiled.
1071 The file(s) must be bound using the GNAT binder.
1073 All appropriate object files must be linked to produce an executable.
1077 All three steps are most commonly handled by using the @command{gnatmake}
1078 utility program that, given the name of the main program, automatically
1079 performs the necessary compilation, binding and linking steps.
1081 @node Running a Simple Ada Program
1082 @section Running a Simple Ada Program
1085 Any text editor may be used to prepare an Ada program.
1087 used, the optional Ada mode may be helpful in laying out the program.)
1089 program text is a normal text file. We will assume in our initial
1090 example that you have used your editor to prepare the following
1091 standard format text file:
1093 @smallexample @c ada
1095 with Ada.Text_IO; use Ada.Text_IO;
1098 Put_Line ("Hello WORLD!");
1104 This file should be named @file{hello.adb}.
1105 With the normal default file naming conventions, GNAT requires
1107 contain a single compilation unit whose file name is the
1109 with periods replaced by hyphens; the
1110 extension is @file{ads} for a
1111 spec and @file{adb} for a body.
1112 You can override this default file naming convention by use of the
1113 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1114 Alternatively, if you want to rename your files according to this default
1115 convention, which is probably more convenient if you will be using GNAT
1116 for all your compilations, then the @code{gnatchop} utility
1117 can be used to generate correctly-named source files
1118 (@pxref{Renaming Files Using gnatchop}).
1120 You can compile the program using the following command (@code{$} is used
1121 as the command prompt in the examples in this document):
1128 @command{gcc} is the command used to run the compiler. This compiler is
1129 capable of compiling programs in several languages, including Ada and
1130 C. It assumes that you have given it an Ada program if the file extension is
1131 either @file{.ads} or @file{.adb}, and it will then call
1132 the GNAT compiler to compile the specified file.
1135 The @option{-c} switch is required. It tells @command{gcc} to only do a
1136 compilation. (For C programs, @command{gcc} can also do linking, but this
1137 capability is not used directly for Ada programs, so the @option{-c}
1138 switch must always be present.)
1141 This compile command generates a file
1142 @file{hello.o}, which is the object
1143 file corresponding to your Ada program. It also generates
1144 an ``Ada Library Information'' file @file{hello.ali},
1145 which contains additional information used to check
1146 that an Ada program is consistent.
1147 To build an executable file,
1148 use @code{gnatbind} to bind the program
1149 and @command{gnatlink} to link it. The
1150 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1151 @file{ALI} file, but the default extension of @file{.ali} can
1152 be omitted. This means that in the most common case, the argument
1153 is simply the name of the main program:
1161 A simpler method of carrying out these steps is to use
1163 a master program that invokes all the required
1164 compilation, binding and linking tools in the correct order. In particular,
1165 @command{gnatmake} automatically recompiles any sources that have been
1166 modified since they were last compiled, or sources that depend
1167 on such modified sources, so that ``version skew'' is avoided.
1168 @cindex Version skew (avoided by @command{gnatmake})
1171 $ gnatmake hello.adb
1175 The result is an executable program called @file{hello}, which can be
1183 assuming that the current directory is on the search path
1184 for executable programs.
1187 and, if all has gone well, you will see
1194 appear in response to this command.
1196 @c ****************************************
1197 @node Running a Program with Multiple Units
1198 @section Running a Program with Multiple Units
1201 Consider a slightly more complicated example that has three files: a
1202 main program, and the spec and body of a package:
1204 @smallexample @c ada
1207 package Greetings is
1212 with Ada.Text_IO; use Ada.Text_IO;
1213 package body Greetings is
1216 Put_Line ("Hello WORLD!");
1219 procedure Goodbye is
1221 Put_Line ("Goodbye WORLD!");
1238 Following the one-unit-per-file rule, place this program in the
1239 following three separate files:
1243 spec of package @code{Greetings}
1246 body of package @code{Greetings}
1249 body of main program
1253 To build an executable version of
1254 this program, we could use four separate steps to compile, bind, and link
1255 the program, as follows:
1259 $ gcc -c greetings.adb
1265 Note that there is no required order of compilation when using GNAT.
1266 In particular it is perfectly fine to compile the main program first.
1267 Also, it is not necessary to compile package specs in the case where
1268 there is an accompanying body; you only need to compile the body. If you want
1269 to submit these files to the compiler for semantic checking and not code
1270 generation, then use the
1271 @option{-gnatc} switch:
1274 $ gcc -c greetings.ads -gnatc
1278 Although the compilation can be done in separate steps as in the
1279 above example, in practice it is almost always more convenient
1280 to use the @command{gnatmake} tool. All you need to know in this case
1281 is the name of the main program's source file. The effect of the above four
1282 commands can be achieved with a single one:
1285 $ gnatmake gmain.adb
1289 In the next section we discuss the advantages of using @command{gnatmake} in
1292 @c *****************************
1293 @node Using the gnatmake Utility
1294 @section Using the @command{gnatmake} Utility
1297 If you work on a program by compiling single components at a time using
1298 @command{gcc}, you typically keep track of the units you modify. In order to
1299 build a consistent system, you compile not only these units, but also any
1300 units that depend on the units you have modified.
1301 For example, in the preceding case,
1302 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1303 you edit @file{greetings.ads}, you must recompile both
1304 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1305 units that depend on @file{greetings.ads}.
1307 @code{gnatbind} will warn you if you forget one of these compilation
1308 steps, so that it is impossible to generate an inconsistent program as a
1309 result of forgetting to do a compilation. Nevertheless it is tedious and
1310 error-prone to keep track of dependencies among units.
1311 One approach to handle the dependency-bookkeeping is to use a
1312 makefile. However, makefiles present maintenance problems of their own:
1313 if the dependencies change as you change the program, you must make
1314 sure that the makefile is kept up-to-date manually, which is also an
1315 error-prone process.
1317 The @command{gnatmake} utility takes care of these details automatically.
1318 Invoke it using either one of the following forms:
1321 $ gnatmake gmain.adb
1322 $ gnatmake ^gmain^GMAIN^
1326 The argument is the name of the file containing the main program;
1327 you may omit the extension. @command{gnatmake}
1328 examines the environment, automatically recompiles any files that need
1329 recompiling, and binds and links the resulting set of object files,
1330 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1331 In a large program, it
1332 can be extremely helpful to use @command{gnatmake}, because working out by hand
1333 what needs to be recompiled can be difficult.
1335 Note that @command{gnatmake}
1336 takes into account all the Ada rules that
1337 establish dependencies among units. These include dependencies that result
1338 from inlining subprogram bodies, and from
1339 generic instantiation. Unlike some other
1340 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1341 found by the compiler on a previous compilation, which may possibly
1342 be wrong when sources change. @command{gnatmake} determines the exact set of
1343 dependencies from scratch each time it is run.
1346 @node Editing with Emacs
1347 @section Editing with Emacs
1351 Emacs is an extensible self-documenting text editor that is available in a
1352 separate VMSINSTAL kit.
1354 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1355 click on the Emacs Help menu and run the Emacs Tutorial.
1356 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1357 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1359 Documentation on Emacs and other tools is available in Emacs under the
1360 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1361 use the middle mouse button to select a topic (e.g.@: Emacs).
1363 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1364 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1365 get to the Emacs manual.
1366 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1369 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1370 which is sufficiently extensible to provide for a complete programming
1371 environment and shell for the sophisticated user.
1375 @node Introduction to GPS
1376 @section Introduction to GPS
1377 @cindex GPS (GNAT Programming Studio)
1378 @cindex GNAT Programming Studio (GPS)
1380 Although the command line interface (@command{gnatmake}, etc.) alone
1381 is sufficient, a graphical Interactive Development
1382 Environment can make it easier for you to compose, navigate, and debug
1383 programs. This section describes the main features of GPS
1384 (``GNAT Programming Studio''), the GNAT graphical IDE.
1385 You will see how to use GPS to build and debug an executable, and
1386 you will also learn some of the basics of the GNAT ``project'' facility.
1388 GPS enables you to do much more than is presented here;
1389 e.g., you can produce a call graph, interface to a third-party
1390 Version Control System, and inspect the generated assembly language
1392 Indeed, GPS also supports languages other than Ada.
1393 Such additional information, and an explanation of all of the GPS menu
1394 items. may be found in the on-line help, which includes
1395 a user's guide and a tutorial (these are also accessible from the GNAT
1399 * Building a New Program with GPS::
1400 * Simple Debugging with GPS::
1403 @node Building a New Program with GPS
1404 @subsection Building a New Program with GPS
1406 GPS invokes the GNAT compilation tools using information
1407 contained in a @emph{project} (also known as a @emph{project file}):
1408 a collection of properties such
1409 as source directories, identities of main subprograms, tool switches, etc.,
1410 and their associated values.
1411 See @ref{GNAT Project Manager} for details.
1412 In order to run GPS, you will need to either create a new project
1413 or else open an existing one.
1415 This section will explain how you can use GPS to create a project,
1416 to associate Ada source files with a project, and to build and run
1420 @item @emph{Creating a project}
1422 Invoke GPS, either from the command line or the platform's IDE.
1423 After it starts, GPS will display a ``Welcome'' screen with three
1428 @code{Start with default project in directory}
1431 @code{Create new project with wizard}
1434 @code{Open existing project}
1438 Select @code{Create new project with wizard} and press @code{OK}.
1439 A new window will appear. In the text box labeled with
1440 @code{Enter the name of the project to create}, type @file{sample}
1441 as the project name.
1442 In the next box, browse to choose the directory in which you
1443 would like to create the project file.
1444 After selecting an appropriate directory, press @code{Forward}.
1446 A window will appear with the title
1447 @code{Version Control System Configuration}.
1448 Simply press @code{Forward}.
1450 A window will appear with the title
1451 @code{Please select the source directories for this project}.
1452 The directory that you specified for the project file will be selected
1453 by default as the one to use for sources; simply press @code{Forward}.
1455 A window will appear with the title
1456 @code{Please select the build directory for this project}.
1457 The directory that you specified for the project file will be selected
1458 by default for object files and executables;
1459 simply press @code{Forward}.
1461 A window will appear with the title
1462 @code{Please select the main units for this project}.
1463 You will supply this information later, after creating the source file.
1464 Simply press @code{Forward} for now.
1466 A window will appear with the title
1467 @code{Please select the switches to build the project}.
1468 Press @code{Apply}. This will create a project file named
1469 @file{sample.prj} in the directory that you had specified.
1471 @item @emph{Creating and saving the source file}
1473 After you create the new project, a GPS window will appear, which is
1474 partitioned into two main sections:
1478 A @emph{Workspace area}, initially greyed out, which you will use for
1479 creating and editing source files
1482 Directly below, a @emph{Messages area}, which initially displays a
1483 ``Welcome'' message.
1484 (If the Messages area is not visible, drag its border upward to expand it.)
1488 Select @code{File} on the menu bar, and then the @code{New} command.
1489 The Workspace area will become white, and you can now
1490 enter the source program explicitly.
1491 Type the following text
1493 @smallexample @c ada
1495 with Ada.Text_IO; use Ada.Text_IO;
1498 Put_Line("Hello from GPS!");
1504 Select @code{File}, then @code{Save As}, and enter the source file name
1506 The file will be saved in the same directory you specified as the
1507 location of the default project file.
1509 @item @emph{Updating the project file}
1511 You need to add the new source file to the project.
1513 the @code{Project} menu and then @code{Edit project properties}.
1514 Click the @code{Main files} tab on the left, and then the
1516 Choose @file{hello.adb} from the list, and press @code{Open}.
1517 The project settings window will reflect this action.
1520 @item @emph{Building and running the program}
1522 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1523 and select @file{hello.adb}.
1524 The Messages window will display the resulting invocations of @command{gcc},
1525 @command{gnatbind}, and @command{gnatlink}
1526 (reflecting the default switch settings from the
1527 project file that you created) and then a ``successful compilation/build''
1530 To run the program, choose the @code{Build} menu, then @code{Run}, and
1531 select @command{hello}.
1532 An @emph{Arguments Selection} window will appear.
1533 There are no command line arguments, so just click @code{OK}.
1535 The Messages window will now display the program's output (the string
1536 @code{Hello from GPS}), and at the bottom of the GPS window a status
1537 update is displayed (@code{Run: hello}).
1538 Close the GPS window (or select @code{File}, then @code{Exit}) to
1539 terminate this GPS session.
1542 @node Simple Debugging with GPS
1543 @subsection Simple Debugging with GPS
1545 This section illustrates basic debugging techniques (setting breakpoints,
1546 examining/modifying variables, single stepping).
1549 @item @emph{Opening a project}
1551 Start GPS and select @code{Open existing project}; browse to
1552 specify the project file @file{sample.prj} that you had created in the
1555 @item @emph{Creating a source file}
1557 Select @code{File}, then @code{New}, and type in the following program:
1559 @smallexample @c ada
1561 with Ada.Text_IO; use Ada.Text_IO;
1562 procedure Example is
1563 Line : String (1..80);
1566 Put_Line("Type a line of text at each prompt; an empty line to exit");
1570 Put_Line (Line (1..N) );
1578 Select @code{File}, then @code{Save as}, and enter the file name
1581 @item @emph{Updating the project file}
1583 Add @code{Example} as a new main unit for the project:
1586 Select @code{Project}, then @code{Edit Project Properties}.
1589 Select the @code{Main files} tab, click @code{Add}, then
1590 select the file @file{example.adb} from the list, and
1592 You will see the file name appear in the list of main units
1598 @item @emph{Building/running the executable}
1600 To build the executable
1601 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1603 Run the program to see its effect (in the Messages area).
1604 Each line that you enter is displayed; an empty line will
1605 cause the loop to exit and the program to terminate.
1607 @item @emph{Debugging the program}
1609 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1610 which are required for debugging, are on by default when you create
1612 Thus unless you intentionally remove these settings, you will be able
1613 to debug any program that you develop using GPS.
1616 @item @emph{Initializing}
1618 Select @code{Debug}, then @code{Initialize}, then @file{example}
1620 @item @emph{Setting a breakpoint}
1622 After performing the initialization step, you will observe a small
1623 icon to the right of each line number.
1624 This serves as a toggle for breakpoints; clicking the icon will
1625 set a breakpoint at the corresponding line (the icon will change to
1626 a red circle with an ``x''), and clicking it again
1627 will remove the breakpoint / reset the icon.
1629 For purposes of this example, set a breakpoint at line 10 (the
1630 statement @code{Put_Line@ (Line@ (1..N));}
1632 @item @emph{Starting program execution}
1634 Select @code{Debug}, then @code{Run}. When the
1635 @code{Program Arguments} window appears, click @code{OK}.
1636 A console window will appear; enter some line of text,
1637 e.g.@: @code{abcde}, at the prompt.
1638 The program will pause execution when it gets to the
1639 breakpoint, and the corresponding line is highlighted.
1641 @item @emph{Examining a variable}
1643 Move the mouse over one of the occurrences of the variable @code{N}.
1644 You will see the value (5) displayed, in ``tool tip'' fashion.
1645 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1646 You will see information about @code{N} appear in the @code{Debugger Data}
1647 pane, showing the value as 5.
1649 @item @emph{Assigning a new value to a variable}
1651 Right click on the @code{N} in the @code{Debugger Data} pane, and
1652 select @code{Set value of N}.
1653 When the input window appears, enter the value @code{4} and click
1655 This value does not automatically appear in the @code{Debugger Data}
1656 pane; to see it, right click again on the @code{N} in the
1657 @code{Debugger Data} pane and select @code{Update value}.
1658 The new value, 4, will appear in red.
1660 @item @emph{Single stepping}
1662 Select @code{Debug}, then @code{Next}.
1663 This will cause the next statement to be executed, in this case the
1664 call of @code{Put_Line} with the string slice.
1665 Notice in the console window that the displayed string is simply
1666 @code{abcd} and not @code{abcde} which you had entered.
1667 This is because the upper bound of the slice is now 4 rather than 5.
1669 @item @emph{Removing a breakpoint}
1671 Toggle the breakpoint icon at line 10.
1673 @item @emph{Resuming execution from a breakpoint}
1675 Select @code{Debug}, then @code{Continue}.
1676 The program will reach the next iteration of the loop, and
1677 wait for input after displaying the prompt.
1678 This time, just hit the @kbd{Enter} key.
1679 The value of @code{N} will be 0, and the program will terminate.
1680 The console window will disappear.
1685 @node The GNAT Compilation Model
1686 @chapter The GNAT Compilation Model
1687 @cindex GNAT compilation model
1688 @cindex Compilation model
1691 * Source Representation::
1692 * Foreign Language Representation::
1693 * File Naming Rules::
1694 * Using Other File Names::
1695 * Alternative File Naming Schemes::
1696 * Generating Object Files::
1697 * Source Dependencies::
1698 * The Ada Library Information Files::
1699 * Binding an Ada Program::
1700 * Mixed Language Programming::
1702 * Building Mixed Ada & C++ Programs::
1703 * Comparison between GNAT and C/C++ Compilation Models::
1705 * Comparison between GNAT and Conventional Ada Library Models::
1707 * Placement of temporary files::
1712 This chapter describes the compilation model used by GNAT. Although
1713 similar to that used by other languages, such as C and C++, this model
1714 is substantially different from the traditional Ada compilation models,
1715 which are based on a library. The model is initially described without
1716 reference to the library-based model. If you have not previously used an
1717 Ada compiler, you need only read the first part of this chapter. The
1718 last section describes and discusses the differences between the GNAT
1719 model and the traditional Ada compiler models. If you have used other
1720 Ada compilers, this section will help you to understand those
1721 differences, and the advantages of the GNAT model.
1723 @node Source Representation
1724 @section Source Representation
1728 Ada source programs are represented in standard text files, using
1729 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1730 7-bit ASCII set, plus additional characters used for
1731 representing foreign languages (@pxref{Foreign Language Representation}
1732 for support of non-USA character sets). The format effector characters
1733 are represented using their standard ASCII encodings, as follows:
1738 Vertical tab, @code{16#0B#}
1742 Horizontal tab, @code{16#09#}
1746 Carriage return, @code{16#0D#}
1750 Line feed, @code{16#0A#}
1754 Form feed, @code{16#0C#}
1758 Source files are in standard text file format. In addition, GNAT will
1759 recognize a wide variety of stream formats, in which the end of
1760 physical lines is marked by any of the following sequences:
1761 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1762 in accommodating files that are imported from other operating systems.
1764 @cindex End of source file
1765 @cindex Source file, end
1767 The end of a source file is normally represented by the physical end of
1768 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1769 recognized as signalling the end of the source file. Again, this is
1770 provided for compatibility with other operating systems where this
1771 code is used to represent the end of file.
1773 Each file contains a single Ada compilation unit, including any pragmas
1774 associated with the unit. For example, this means you must place a
1775 package declaration (a package @dfn{spec}) and the corresponding body in
1776 separate files. An Ada @dfn{compilation} (which is a sequence of
1777 compilation units) is represented using a sequence of files. Similarly,
1778 you will place each subunit or child unit in a separate file.
1780 @node Foreign Language Representation
1781 @section Foreign Language Representation
1784 GNAT supports the standard character sets defined in Ada as well as
1785 several other non-standard character sets for use in localized versions
1786 of the compiler (@pxref{Character Set Control}).
1789 * Other 8-Bit Codes::
1790 * Wide Character Encodings::
1798 The basic character set is Latin-1. This character set is defined by ISO
1799 standard 8859, part 1. The lower half (character codes @code{16#00#}
1800 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1801 is used to represent additional characters. These include extended letters
1802 used by European languages, such as French accents, the vowels with umlauts
1803 used in German, and the extra letter A-ring used in Swedish.
1805 @findex Ada.Characters.Latin_1
1806 For a complete list of Latin-1 codes and their encodings, see the source
1807 file of library unit @code{Ada.Characters.Latin_1} in file
1808 @file{a-chlat1.ads}.
1809 You may use any of these extended characters freely in character or
1810 string literals. In addition, the extended characters that represent
1811 letters can be used in identifiers.
1813 @node Other 8-Bit Codes
1814 @subsection Other 8-Bit Codes
1817 GNAT also supports several other 8-bit coding schemes:
1820 @item ISO 8859-2 (Latin-2)
1823 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1826 @item ISO 8859-3 (Latin-3)
1829 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1832 @item ISO 8859-4 (Latin-4)
1835 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1838 @item ISO 8859-5 (Cyrillic)
1841 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1842 lowercase equivalence.
1844 @item ISO 8859-15 (Latin-9)
1847 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1848 lowercase equivalence
1850 @item IBM PC (code page 437)
1851 @cindex code page 437
1852 This code page is the normal default for PCs in the U.S. It corresponds
1853 to the original IBM PC character set. This set has some, but not all, of
1854 the extended Latin-1 letters, but these letters do not have the same
1855 encoding as Latin-1. In this mode, these letters are allowed in
1856 identifiers with uppercase and lowercase equivalence.
1858 @item IBM PC (code page 850)
1859 @cindex code page 850
1860 This code page is a modification of 437 extended to include all the
1861 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1862 mode, all these letters are allowed in identifiers with uppercase and
1863 lowercase equivalence.
1865 @item Full Upper 8-bit
1866 Any character in the range 80-FF allowed in identifiers, and all are
1867 considered distinct. In other words, there are no uppercase and lowercase
1868 equivalences in this range. This is useful in conjunction with
1869 certain encoding schemes used for some foreign character sets (e.g.,
1870 the typical method of representing Chinese characters on the PC).
1873 No upper-half characters in the range 80-FF are allowed in identifiers.
1874 This gives Ada 83 compatibility for identifier names.
1878 For precise data on the encodings permitted, and the uppercase and lowercase
1879 equivalences that are recognized, see the file @file{csets.adb} in
1880 the GNAT compiler sources. You will need to obtain a full source release
1881 of GNAT to obtain this file.
1883 @node Wide Character Encodings
1884 @subsection Wide Character Encodings
1887 GNAT allows wide character codes to appear in character and string
1888 literals, and also optionally in identifiers, by means of the following
1889 possible encoding schemes:
1894 In this encoding, a wide character is represented by the following five
1902 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1903 characters (using uppercase letters) of the wide character code. For
1904 example, ESC A345 is used to represent the wide character with code
1906 This scheme is compatible with use of the full Wide_Character set.
1908 @item Upper-Half Coding
1909 @cindex Upper-Half Coding
1910 The wide character with encoding @code{16#abcd#} where the upper bit is on
1911 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1912 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1913 character, but is not required to be in the upper half. This method can
1914 be also used for shift-JIS or EUC, where the internal coding matches the
1917 @item Shift JIS Coding
1918 @cindex Shift JIS Coding
1919 A wide character is represented by a two-character sequence,
1921 @code{16#cd#}, with the restrictions described for upper-half encoding as
1922 described above. The internal character code is the corresponding JIS
1923 character according to the standard algorithm for Shift-JIS
1924 conversion. Only characters defined in the JIS code set table can be
1925 used with this encoding method.
1929 A wide character is represented by a two-character sequence
1931 @code{16#cd#}, with both characters being in the upper half. The internal
1932 character code is the corresponding JIS character according to the EUC
1933 encoding algorithm. Only characters defined in the JIS code set table
1934 can be used with this encoding method.
1937 A wide character is represented using
1938 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1939 10646-1/Am.2. Depending on the character value, the representation
1940 is a one, two, or three byte sequence:
1945 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1946 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1947 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1952 where the @var{xxx} bits correspond to the left-padded bits of the
1953 16-bit character value. Note that all lower half ASCII characters
1954 are represented as ASCII bytes and all upper half characters and
1955 other wide characters are represented as sequences of upper-half
1956 (The full UTF-8 scheme allows for encoding 31-bit characters as
1957 6-byte sequences, but in this implementation, all UTF-8 sequences
1958 of four or more bytes length will be treated as illegal).
1959 @item Brackets Coding
1960 In this encoding, a wide character is represented by the following eight
1968 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1969 characters (using uppercase letters) of the wide character code. For
1970 example, [``A345''] is used to represent the wide character with code
1971 @code{16#A345#}. It is also possible (though not required) to use the
1972 Brackets coding for upper half characters. For example, the code
1973 @code{16#A3#} can be represented as @code{[``A3'']}.
1975 This scheme is compatible with use of the full Wide_Character set,
1976 and is also the method used for wide character encoding in the standard
1977 ACVC (Ada Compiler Validation Capability) test suite distributions.
1982 Note: Some of these coding schemes do not permit the full use of the
1983 Ada character set. For example, neither Shift JIS, nor EUC allow the
1984 use of the upper half of the Latin-1 set.
1986 @node File Naming Rules
1987 @section File Naming Rules
1990 The default file name is determined by the name of the unit that the
1991 file contains. The name is formed by taking the full expanded name of
1992 the unit and replacing the separating dots with hyphens and using
1993 ^lowercase^uppercase^ for all letters.
1995 An exception arises if the file name generated by the above rules starts
1996 with one of the characters
1998 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2001 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2003 and the second character is a
2004 minus. In this case, the character ^tilde^dollar sign^ is used in place
2005 of the minus. The reason for this special rule is to avoid clashes with
2006 the standard names for child units of the packages System, Ada,
2007 Interfaces, and GNAT, which use the prefixes
2009 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2012 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2016 The file extension is @file{.ads} for a spec and
2017 @file{.adb} for a body. The following list shows some
2018 examples of these rules.
2025 @item arith_functions.ads
2026 Arith_Functions (package spec)
2027 @item arith_functions.adb
2028 Arith_Functions (package body)
2030 Func.Spec (child package spec)
2032 Func.Spec (child package body)
2034 Sub (subunit of Main)
2035 @item ^a~bad.adb^A$BAD.ADB^
2036 A.Bad (child package body)
2040 Following these rules can result in excessively long
2041 file names if corresponding
2042 unit names are long (for example, if child units or subunits are
2043 heavily nested). An option is available to shorten such long file names
2044 (called file name ``krunching''). This may be particularly useful when
2045 programs being developed with GNAT are to be used on operating systems
2046 with limited file name lengths. @xref{Using gnatkr}.
2048 Of course, no file shortening algorithm can guarantee uniqueness over
2049 all possible unit names; if file name krunching is used, it is your
2050 responsibility to ensure no name clashes occur. Alternatively you
2051 can specify the exact file names that you want used, as described
2052 in the next section. Finally, if your Ada programs are migrating from a
2053 compiler with a different naming convention, you can use the gnatchop
2054 utility to produce source files that follow the GNAT naming conventions.
2055 (For details @pxref{Renaming Files Using gnatchop}.)
2057 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2058 systems, case is not significant. So for example on @code{Windows XP}
2059 if the canonical name is @code{main-sub.adb}, you can use the file name
2060 @code{Main-Sub.adb} instead. However, case is significant for other
2061 operating systems, so for example, if you want to use other than
2062 canonically cased file names on a Unix system, you need to follow
2063 the procedures described in the next section.
2065 @node Using Other File Names
2066 @section Using Other File Names
2070 In the previous section, we have described the default rules used by
2071 GNAT to determine the file name in which a given unit resides. It is
2072 often convenient to follow these default rules, and if you follow them,
2073 the compiler knows without being explicitly told where to find all
2076 However, in some cases, particularly when a program is imported from
2077 another Ada compiler environment, it may be more convenient for the
2078 programmer to specify which file names contain which units. GNAT allows
2079 arbitrary file names to be used by means of the Source_File_Name pragma.
2080 The form of this pragma is as shown in the following examples:
2081 @cindex Source_File_Name pragma
2083 @smallexample @c ada
2085 pragma Source_File_Name (My_Utilities.Stacks,
2086 Spec_File_Name => "myutilst_a.ada");
2087 pragma Source_File_name (My_Utilities.Stacks,
2088 Body_File_Name => "myutilst.ada");
2093 As shown in this example, the first argument for the pragma is the unit
2094 name (in this example a child unit). The second argument has the form
2095 of a named association. The identifier
2096 indicates whether the file name is for a spec or a body;
2097 the file name itself is given by a string literal.
2099 The source file name pragma is a configuration pragma, which means that
2100 normally it will be placed in the @file{gnat.adc}
2101 file used to hold configuration
2102 pragmas that apply to a complete compilation environment.
2103 For more details on how the @file{gnat.adc} file is created and used
2104 see @ref{Handling of Configuration Pragmas}.
2105 @cindex @file{gnat.adc}
2108 GNAT allows completely arbitrary file names to be specified using the
2109 source file name pragma. However, if the file name specified has an
2110 extension other than @file{.ads} or @file{.adb} it is necessary to use
2111 a special syntax when compiling the file. The name in this case must be
2112 preceded by the special sequence @option{-x} followed by a space and the name
2113 of the language, here @code{ada}, as in:
2116 $ gcc -c -x ada peculiar_file_name.sim
2121 @command{gnatmake} handles non-standard file names in the usual manner (the
2122 non-standard file name for the main program is simply used as the
2123 argument to gnatmake). Note that if the extension is also non-standard,
2124 then it must be included in the @command{gnatmake} command, it may not
2127 @node Alternative File Naming Schemes
2128 @section Alternative File Naming Schemes
2129 @cindex File naming schemes, alternative
2132 In the previous section, we described the use of the @code{Source_File_Name}
2133 pragma to allow arbitrary names to be assigned to individual source files.
2134 However, this approach requires one pragma for each file, and especially in
2135 large systems can result in very long @file{gnat.adc} files, and also create
2136 a maintenance problem.
2138 GNAT also provides a facility for specifying systematic file naming schemes
2139 other than the standard default naming scheme previously described. An
2140 alternative scheme for naming is specified by the use of
2141 @code{Source_File_Name} pragmas having the following format:
2142 @cindex Source_File_Name pragma
2144 @smallexample @c ada
2145 pragma Source_File_Name (
2146 Spec_File_Name => FILE_NAME_PATTERN
2147 @r{[},Casing => CASING_SPEC@r{]}
2148 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2150 pragma Source_File_Name (
2151 Body_File_Name => FILE_NAME_PATTERN
2152 @r{[},Casing => CASING_SPEC@r{]}
2153 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2155 pragma Source_File_Name (
2156 Subunit_File_Name => FILE_NAME_PATTERN
2157 @r{[},Casing => CASING_SPEC@r{]}
2158 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2160 FILE_NAME_PATTERN ::= STRING_LITERAL
2161 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2165 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2166 It contains a single asterisk character, and the unit name is substituted
2167 systematically for this asterisk. The optional parameter
2168 @code{Casing} indicates
2169 whether the unit name is to be all upper-case letters, all lower-case letters,
2170 or mixed-case. If no
2171 @code{Casing} parameter is used, then the default is all
2172 ^lower-case^upper-case^.
2174 The optional @code{Dot_Replacement} string is used to replace any periods
2175 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2176 argument is used then separating dots appear unchanged in the resulting
2178 Although the above syntax indicates that the
2179 @code{Casing} argument must appear
2180 before the @code{Dot_Replacement} argument, but it
2181 is also permissible to write these arguments in the opposite order.
2183 As indicated, it is possible to specify different naming schemes for
2184 bodies, specs, and subunits. Quite often the rule for subunits is the
2185 same as the rule for bodies, in which case, there is no need to give
2186 a separate @code{Subunit_File_Name} rule, and in this case the
2187 @code{Body_File_name} rule is used for subunits as well.
2189 The separate rule for subunits can also be used to implement the rather
2190 unusual case of a compilation environment (e.g.@: a single directory) which
2191 contains a subunit and a child unit with the same unit name. Although
2192 both units cannot appear in the same partition, the Ada Reference Manual
2193 allows (but does not require) the possibility of the two units coexisting
2194 in the same environment.
2196 The file name translation works in the following steps:
2201 If there is a specific @code{Source_File_Name} pragma for the given unit,
2202 then this is always used, and any general pattern rules are ignored.
2205 If there is a pattern type @code{Source_File_Name} pragma that applies to
2206 the unit, then the resulting file name will be used if the file exists. If
2207 more than one pattern matches, the latest one will be tried first, and the
2208 first attempt resulting in a reference to a file that exists will be used.
2211 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2212 for which the corresponding file exists, then the standard GNAT default
2213 naming rules are used.
2218 As an example of the use of this mechanism, consider a commonly used scheme
2219 in which file names are all lower case, with separating periods copied
2220 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2221 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2224 @smallexample @c ada
2225 pragma Source_File_Name
2226 (Spec_File_Name => "*.1.ada");
2227 pragma Source_File_Name
2228 (Body_File_Name => "*.2.ada");
2232 The default GNAT scheme is actually implemented by providing the following
2233 default pragmas internally:
2235 @smallexample @c ada
2236 pragma Source_File_Name
2237 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2238 pragma Source_File_Name
2239 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2243 Our final example implements a scheme typically used with one of the
2244 Ada 83 compilers, where the separator character for subunits was ``__''
2245 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2246 by adding @file{.ADA}, and subunits by
2247 adding @file{.SEP}. All file names were
2248 upper case. Child units were not present of course since this was an
2249 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2250 the same double underscore separator for child units.
2252 @smallexample @c ada
2253 pragma Source_File_Name
2254 (Spec_File_Name => "*_.ADA",
2255 Dot_Replacement => "__",
2256 Casing = Uppercase);
2257 pragma Source_File_Name
2258 (Body_File_Name => "*.ADA",
2259 Dot_Replacement => "__",
2260 Casing = Uppercase);
2261 pragma Source_File_Name
2262 (Subunit_File_Name => "*.SEP",
2263 Dot_Replacement => "__",
2264 Casing = Uppercase);
2267 @node Generating Object Files
2268 @section Generating Object Files
2271 An Ada program consists of a set of source files, and the first step in
2272 compiling the program is to generate the corresponding object files.
2273 These are generated by compiling a subset of these source files.
2274 The files you need to compile are the following:
2278 If a package spec has no body, compile the package spec to produce the
2279 object file for the package.
2282 If a package has both a spec and a body, compile the body to produce the
2283 object file for the package. The source file for the package spec need
2284 not be compiled in this case because there is only one object file, which
2285 contains the code for both the spec and body of the package.
2288 For a subprogram, compile the subprogram body to produce the object file
2289 for the subprogram. The spec, if one is present, is as usual in a
2290 separate file, and need not be compiled.
2294 In the case of subunits, only compile the parent unit. A single object
2295 file is generated for the entire subunit tree, which includes all the
2299 Compile child units independently of their parent units
2300 (though, of course, the spec of all the ancestor unit must be present in order
2301 to compile a child unit).
2305 Compile generic units in the same manner as any other units. The object
2306 files in this case are small dummy files that contain at most the
2307 flag used for elaboration checking. This is because GNAT always handles generic
2308 instantiation by means of macro expansion. However, it is still necessary to
2309 compile generic units, for dependency checking and elaboration purposes.
2313 The preceding rules describe the set of files that must be compiled to
2314 generate the object files for a program. Each object file has the same
2315 name as the corresponding source file, except that the extension is
2318 You may wish to compile other files for the purpose of checking their
2319 syntactic and semantic correctness. For example, in the case where a
2320 package has a separate spec and body, you would not normally compile the
2321 spec. However, it is convenient in practice to compile the spec to make
2322 sure it is error-free before compiling clients of this spec, because such
2323 compilations will fail if there is an error in the spec.
2325 GNAT provides an option for compiling such files purely for the
2326 purposes of checking correctness; such compilations are not required as
2327 part of the process of building a program. To compile a file in this
2328 checking mode, use the @option{-gnatc} switch.
2330 @node Source Dependencies
2331 @section Source Dependencies
2334 A given object file clearly depends on the source file which is compiled
2335 to produce it. Here we are using @dfn{depends} in the sense of a typical
2336 @code{make} utility; in other words, an object file depends on a source
2337 file if changes to the source file require the object file to be
2339 In addition to this basic dependency, a given object may depend on
2340 additional source files as follows:
2344 If a file being compiled @code{with}'s a unit @var{X}, the object file
2345 depends on the file containing the spec of unit @var{X}. This includes
2346 files that are @code{with}'ed implicitly either because they are parents
2347 of @code{with}'ed child units or they are run-time units required by the
2348 language constructs used in a particular unit.
2351 If a file being compiled instantiates a library level generic unit, the
2352 object file depends on both the spec and body files for this generic
2356 If a file being compiled instantiates a generic unit defined within a
2357 package, the object file depends on the body file for the package as
2358 well as the spec file.
2362 @cindex @option{-gnatn} switch
2363 If a file being compiled contains a call to a subprogram for which
2364 pragma @code{Inline} applies and inlining is activated with the
2365 @option{-gnatn} switch, the object file depends on the file containing the
2366 body of this subprogram as well as on the file containing the spec. Note
2367 that for inlining to actually occur as a result of the use of this switch,
2368 it is necessary to compile in optimizing mode.
2370 @cindex @option{-gnatN} switch
2371 The use of @option{-gnatN} activates inlining optimization
2372 that is performed by the front end of the compiler. This inlining does
2373 not require that the code generation be optimized. Like @option{-gnatn},
2374 the use of this switch generates additional dependencies.
2376 When using a gcc-based back end (in practice this means using any version
2377 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2378 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2379 Historically front end inlining was more extensive than the gcc back end
2380 inlining, but that is no longer the case.
2383 If an object file @file{O} depends on the proper body of a subunit through
2384 inlining or instantiation, it depends on the parent unit of the subunit.
2385 This means that any modification of the parent unit or one of its subunits
2386 affects the compilation of @file{O}.
2389 The object file for a parent unit depends on all its subunit body files.
2392 The previous two rules meant that for purposes of computing dependencies and
2393 recompilation, a body and all its subunits are treated as an indivisible whole.
2396 These rules are applied transitively: if unit @code{A} @code{with}'s
2397 unit @code{B}, whose elaboration calls an inlined procedure in package
2398 @code{C}, the object file for unit @code{A} will depend on the body of
2399 @code{C}, in file @file{c.adb}.
2401 The set of dependent files described by these rules includes all the
2402 files on which the unit is semantically dependent, as dictated by the
2403 Ada language standard. However, it is a superset of what the
2404 standard describes, because it includes generic, inline, and subunit
2407 An object file must be recreated by recompiling the corresponding source
2408 file if any of the source files on which it depends are modified. For
2409 example, if the @code{make} utility is used to control compilation,
2410 the rule for an Ada object file must mention all the source files on
2411 which the object file depends, according to the above definition.
2412 The determination of the necessary
2413 recompilations is done automatically when one uses @command{gnatmake}.
2416 @node The Ada Library Information Files
2417 @section The Ada Library Information Files
2418 @cindex Ada Library Information files
2419 @cindex @file{ALI} files
2422 Each compilation actually generates two output files. The first of these
2423 is the normal object file that has a @file{.o} extension. The second is a
2424 text file containing full dependency information. It has the same
2425 name as the source file, but an @file{.ali} extension.
2426 This file is known as the Ada Library Information (@file{ALI}) file.
2427 The following information is contained in the @file{ALI} file.
2431 Version information (indicates which version of GNAT was used to compile
2432 the unit(s) in question)
2435 Main program information (including priority and time slice settings,
2436 as well as the wide character encoding used during compilation).
2439 List of arguments used in the @command{gcc} command for the compilation
2442 Attributes of the unit, including configuration pragmas used, an indication
2443 of whether the compilation was successful, exception model used etc.
2446 A list of relevant restrictions applying to the unit (used for consistency)
2450 Categorization information (e.g.@: use of pragma @code{Pure}).
2453 Information on all @code{with}'ed units, including presence of
2454 @code{Elaborate} or @code{Elaborate_All} pragmas.
2457 Information from any @code{Linker_Options} pragmas used in the unit
2460 Information on the use of @code{Body_Version} or @code{Version}
2461 attributes in the unit.
2464 Dependency information. This is a list of files, together with
2465 time stamp and checksum information. These are files on which
2466 the unit depends in the sense that recompilation is required
2467 if any of these units are modified.
2470 Cross-reference data. Contains information on all entities referenced
2471 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2472 provide cross-reference information.
2477 For a full detailed description of the format of the @file{ALI} file,
2478 see the source of the body of unit @code{Lib.Writ}, contained in file
2479 @file{lib-writ.adb} in the GNAT compiler sources.
2481 @node Binding an Ada Program
2482 @section Binding an Ada Program
2485 When using languages such as C and C++, once the source files have been
2486 compiled the only remaining step in building an executable program
2487 is linking the object modules together. This means that it is possible to
2488 link an inconsistent version of a program, in which two units have
2489 included different versions of the same header.
2491 The rules of Ada do not permit such an inconsistent program to be built.
2492 For example, if two clients have different versions of the same package,
2493 it is illegal to build a program containing these two clients.
2494 These rules are enforced by the GNAT binder, which also determines an
2495 elaboration order consistent with the Ada rules.
2497 The GNAT binder is run after all the object files for a program have
2498 been created. It is given the name of the main program unit, and from
2499 this it determines the set of units required by the program, by reading the
2500 corresponding ALI files. It generates error messages if the program is
2501 inconsistent or if no valid order of elaboration exists.
2503 If no errors are detected, the binder produces a main program, in Ada by
2504 default, that contains calls to the elaboration procedures of those
2505 compilation unit that require them, followed by
2506 a call to the main program. This Ada program is compiled to generate the
2507 object file for the main program. The name of
2508 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2509 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2512 Finally, the linker is used to build the resulting executable program,
2513 using the object from the main program from the bind step as well as the
2514 object files for the Ada units of the program.
2516 @node Mixed Language Programming
2517 @section Mixed Language Programming
2518 @cindex Mixed Language Programming
2521 This section describes how to develop a mixed-language program,
2522 specifically one that comprises units in both Ada and C.
2525 * Interfacing to C::
2526 * Calling Conventions::
2529 @node Interfacing to C
2530 @subsection Interfacing to C
2532 Interfacing Ada with a foreign language such as C involves using
2533 compiler directives to import and/or export entity definitions in each
2534 language---using @code{extern} statements in C, for instance, and the
2535 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2536 A full treatment of these topics is provided in Appendix B, section 1
2537 of the Ada Reference Manual.
2539 There are two ways to build a program using GNAT that contains some Ada
2540 sources and some foreign language sources, depending on whether or not
2541 the main subprogram is written in Ada. Here is a source example with
2542 the main subprogram in Ada:
2548 void print_num (int num)
2550 printf ("num is %d.\n", num);
2556 /* num_from_Ada is declared in my_main.adb */
2557 extern int num_from_Ada;
2561 return num_from_Ada;
2565 @smallexample @c ada
2567 procedure My_Main is
2569 -- Declare then export an Integer entity called num_from_Ada
2570 My_Num : Integer := 10;
2571 pragma Export (C, My_Num, "num_from_Ada");
2573 -- Declare an Ada function spec for Get_Num, then use
2574 -- C function get_num for the implementation.
2575 function Get_Num return Integer;
2576 pragma Import (C, Get_Num, "get_num");
2578 -- Declare an Ada procedure spec for Print_Num, then use
2579 -- C function print_num for the implementation.
2580 procedure Print_Num (Num : Integer);
2581 pragma Import (C, Print_Num, "print_num");
2584 Print_Num (Get_Num);
2590 To build this example, first compile the foreign language files to
2591 generate object files:
2593 ^gcc -c file1.c^gcc -c FILE1.C^
2594 ^gcc -c file2.c^gcc -c FILE2.C^
2598 Then, compile the Ada units to produce a set of object files and ALI
2601 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2605 Run the Ada binder on the Ada main program:
2607 gnatbind my_main.ali
2611 Link the Ada main program, the Ada objects and the other language
2614 gnatlink my_main.ali file1.o file2.o
2618 The last three steps can be grouped in a single command:
2620 gnatmake my_main.adb -largs file1.o file2.o
2623 @cindex Binder output file
2625 If the main program is in a language other than Ada, then you may have
2626 more than one entry point into the Ada subsystem. You must use a special
2627 binder option to generate callable routines that initialize and
2628 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2629 Calls to the initialization and finalization routines must be inserted
2630 in the main program, or some other appropriate point in the code. The
2631 call to initialize the Ada units must occur before the first Ada
2632 subprogram is called, and the call to finalize the Ada units must occur
2633 after the last Ada subprogram returns. The binder will place the
2634 initialization and finalization subprograms into the
2635 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2636 sources. To illustrate, we have the following example:
2640 extern void adainit (void);
2641 extern void adafinal (void);
2642 extern int add (int, int);
2643 extern int sub (int, int);
2645 int main (int argc, char *argv[])
2651 /* Should print "21 + 7 = 28" */
2652 printf ("%d + %d = %d\n", a, b, add (a, b));
2653 /* Should print "21 - 7 = 14" */
2654 printf ("%d - %d = %d\n", a, b, sub (a, b));
2660 @smallexample @c ada
2663 function Add (A, B : Integer) return Integer;
2664 pragma Export (C, Add, "add");
2668 package body Unit1 is
2669 function Add (A, B : Integer) return Integer is
2677 function Sub (A, B : Integer) return Integer;
2678 pragma Export (C, Sub, "sub");
2682 package body Unit2 is
2683 function Sub (A, B : Integer) return Integer is
2692 The build procedure for this application is similar to the last
2693 example's. First, compile the foreign language files to generate object
2696 ^gcc -c main.c^gcc -c main.c^
2700 Next, compile the Ada units to produce a set of object files and ALI
2703 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2704 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2708 Run the Ada binder on every generated ALI file. Make sure to use the
2709 @option{-n} option to specify a foreign main program:
2711 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2715 Link the Ada main program, the Ada objects and the foreign language
2716 objects. You need only list the last ALI file here:
2718 gnatlink unit2.ali main.o -o exec_file
2721 This procedure yields a binary executable called @file{exec_file}.
2725 Depending on the circumstances (for example when your non-Ada main object
2726 does not provide symbol @code{main}), you may also need to instruct the
2727 GNAT linker not to include the standard startup objects by passing the
2728 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2730 @node Calling Conventions
2731 @subsection Calling Conventions
2732 @cindex Foreign Languages
2733 @cindex Calling Conventions
2734 GNAT follows standard calling sequence conventions and will thus interface
2735 to any other language that also follows these conventions. The following
2736 Convention identifiers are recognized by GNAT:
2739 @cindex Interfacing to Ada
2740 @cindex Other Ada compilers
2741 @cindex Convention Ada
2743 This indicates that the standard Ada calling sequence will be
2744 used and all Ada data items may be passed without any limitations in the
2745 case where GNAT is used to generate both the caller and callee. It is also
2746 possible to mix GNAT generated code and code generated by another Ada
2747 compiler. In this case, the data types should be restricted to simple
2748 cases, including primitive types. Whether complex data types can be passed
2749 depends on the situation. Probably it is safe to pass simple arrays, such
2750 as arrays of integers or floats. Records may or may not work, depending
2751 on whether both compilers lay them out identically. Complex structures
2752 involving variant records, access parameters, tasks, or protected types,
2753 are unlikely to be able to be passed.
2755 Note that in the case of GNAT running
2756 on a platform that supports HP Ada 83, a higher degree of compatibility
2757 can be guaranteed, and in particular records are layed out in an identical
2758 manner in the two compilers. Note also that if output from two different
2759 compilers is mixed, the program is responsible for dealing with elaboration
2760 issues. Probably the safest approach is to write the main program in the
2761 version of Ada other than GNAT, so that it takes care of its own elaboration
2762 requirements, and then call the GNAT-generated adainit procedure to ensure
2763 elaboration of the GNAT components. Consult the documentation of the other
2764 Ada compiler for further details on elaboration.
2766 However, it is not possible to mix the tasking run time of GNAT and
2767 HP Ada 83, All the tasking operations must either be entirely within
2768 GNAT compiled sections of the program, or entirely within HP Ada 83
2769 compiled sections of the program.
2771 @cindex Interfacing to Assembly
2772 @cindex Convention Assembler
2774 Specifies assembler as the convention. In practice this has the
2775 same effect as convention Ada (but is not equivalent in the sense of being
2776 considered the same convention).
2778 @cindex Convention Asm
2781 Equivalent to Assembler.
2783 @cindex Interfacing to COBOL
2784 @cindex Convention COBOL
2787 Data will be passed according to the conventions described
2788 in section B.4 of the Ada Reference Manual.
2791 @cindex Interfacing to C
2792 @cindex Convention C
2794 Data will be passed according to the conventions described
2795 in section B.3 of the Ada Reference Manual.
2797 A note on interfacing to a C ``varargs'' function:
2798 @findex C varargs function
2799 @cindex Interfacing to C varargs function
2800 @cindex varargs function interfaces
2804 In C, @code{varargs} allows a function to take a variable number of
2805 arguments. There is no direct equivalent in this to Ada. One
2806 approach that can be used is to create a C wrapper for each
2807 different profile and then interface to this C wrapper. For
2808 example, to print an @code{int} value using @code{printf},
2809 create a C function @code{printfi} that takes two arguments, a
2810 pointer to a string and an int, and calls @code{printf}.
2811 Then in the Ada program, use pragma @code{Import} to
2812 interface to @code{printfi}.
2815 It may work on some platforms to directly interface to
2816 a @code{varargs} function by providing a specific Ada profile
2817 for a particular call. However, this does not work on
2818 all platforms, since there is no guarantee that the
2819 calling sequence for a two argument normal C function
2820 is the same as for calling a @code{varargs} C function with
2821 the same two arguments.
2824 @cindex Convention Default
2829 @cindex Convention External
2836 @cindex Interfacing to C++
2837 @cindex Convention C++
2838 @item C_Plus_Plus (or CPP)
2839 This stands for C++. For most purposes this is identical to C.
2840 See the separate description of the specialized GNAT pragmas relating to
2841 C++ interfacing for further details.
2845 @cindex Interfacing to Fortran
2846 @cindex Convention Fortran
2848 Data will be passed according to the conventions described
2849 in section B.5 of the Ada Reference Manual.
2852 This applies to an intrinsic operation, as defined in the Ada
2853 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2854 this means that the body of the subprogram is provided by the compiler itself,
2855 usually by means of an efficient code sequence, and that the user does not
2856 supply an explicit body for it. In an application program, the pragma may
2857 be applied to the following sets of names:
2861 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2862 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2863 two formal parameters. The
2864 first one must be a signed integer type or a modular type with a binary
2865 modulus, and the second parameter must be of type Natural.
2866 The return type must be the same as the type of the first argument. The size
2867 of this type can only be 8, 16, 32, or 64.
2870 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2871 The corresponding operator declaration must have parameters and result type
2872 that have the same root numeric type (for example, all three are long_float
2873 types). This simplifies the definition of operations that use type checking
2874 to perform dimensional checks:
2876 @smallexample @c ada
2877 type Distance is new Long_Float;
2878 type Time is new Long_Float;
2879 type Velocity is new Long_Float;
2880 function "/" (D : Distance; T : Time)
2882 pragma Import (Intrinsic, "/");
2886 This common idiom is often programmed with a generic definition and an
2887 explicit body. The pragma makes it simpler to introduce such declarations.
2888 It incurs no overhead in compilation time or code size, because it is
2889 implemented as a single machine instruction.
2892 General subprogram entities, to bind an Ada subprogram declaration to
2893 a compiler builtin by name with back-ends where such interfaces are
2894 available. A typical example is the set of ``__builtin'' functions
2895 exposed by the GCC back-end, as in the following example:
2897 @smallexample @c ada
2898 function builtin_sqrt (F : Float) return Float;
2899 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2902 Most of the GCC builtins are accessible this way, and as for other
2903 import conventions (e.g. C), it is the user's responsibility to ensure
2904 that the Ada subprogram profile matches the underlying builtin
2912 @cindex Convention Stdcall
2914 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2915 and specifies that the @code{Stdcall} calling sequence will be used,
2916 as defined by the NT API. Nevertheless, to ease building
2917 cross-platform bindings this convention will be handled as a @code{C} calling
2918 convention on non-Windows platforms.
2921 @cindex Convention DLL
2923 This is equivalent to @code{Stdcall}.
2926 @cindex Convention Win32
2928 This is equivalent to @code{Stdcall}.
2932 @cindex Convention Stubbed
2934 This is a special convention that indicates that the compiler
2935 should provide a stub body that raises @code{Program_Error}.
2939 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2940 that can be used to parametrize conventions and allow additional synonyms
2941 to be specified. For example if you have legacy code in which the convention
2942 identifier Fortran77 was used for Fortran, you can use the configuration
2945 @smallexample @c ada
2946 pragma Convention_Identifier (Fortran77, Fortran);
2950 And from now on the identifier Fortran77 may be used as a convention
2951 identifier (for example in an @code{Import} pragma) with the same
2955 @node Building Mixed Ada & C++ Programs
2956 @section Building Mixed Ada and C++ Programs
2959 A programmer inexperienced with mixed-language development may find that
2960 building an application containing both Ada and C++ code can be a
2961 challenge. This section gives a few
2962 hints that should make this task easier. The first section addresses
2963 the differences between interfacing with C and interfacing with C++.
2965 looks into the delicate problem of linking the complete application from
2966 its Ada and C++ parts. The last section gives some hints on how the GNAT
2967 run-time library can be adapted in order to allow inter-language dispatching
2968 with a new C++ compiler.
2971 * Interfacing to C++::
2972 * Linking a Mixed C++ & Ada Program::
2973 * A Simple Example::
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, and currently, GNAT does
2990 not provide any help to solve the demangling problem. This problem can be
2991 addressed in two ways:
2994 by modifying the C++ code in order to force a C convention using
2995 the @code{extern "C"} syntax.
2998 by figuring out the mangled name and use it as the Link_Name argument of
3003 Interfacing at the class level can be achieved by using the GNAT specific
3004 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3005 gnat_rm, GNAT Reference Manual}, for additional information.
3007 @node Linking a Mixed C++ & Ada Program
3008 @subsection Linking a Mixed C++ & Ada Program
3011 Usually the linker of the C++ development system must be used to link
3012 mixed applications because most C++ systems will resolve elaboration
3013 issues (such as calling constructors on global class instances)
3014 transparently during the link phase. GNAT has been adapted to ease the
3015 use of a foreign linker for the last phase. Three cases can be
3020 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3021 The C++ linker can simply be called by using the C++ specific driver
3022 called @code{c++}. Note that this setup is not very common because it
3023 may involve recompiling the whole GCC tree from sources, which makes it
3024 harder to upgrade the compilation system for one language without
3025 destabilizing the other.
3030 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3034 Using GNAT and G++ from two different GCC installations: If both
3035 compilers are on the @env{PATH}, the previous method may be used. It is
3036 important to note that environment variables such as
3037 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3038 @env{GCC_ROOT} will affect both compilers
3039 at the same time and may make one of the two compilers operate
3040 improperly if set during invocation of the wrong compiler. It is also
3041 very important that the linker uses the proper @file{libgcc.a} GCC
3042 library -- that is, the one from the C++ compiler installation. The
3043 implicit link command as suggested in the @command{gnatmake} command
3044 from the former example can be replaced by an explicit link command with
3045 the full-verbosity option in order to verify which library is used:
3048 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3050 If there is a problem due to interfering environment variables, it can
3051 be worked around by using an intermediate script. The following example
3052 shows the proper script to use when GNAT has not been installed at its
3053 default location and g++ has been installed at its default location:
3061 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3065 Using a non-GNU C++ compiler: The commands previously described can be
3066 used to insure that the C++ linker is used. Nonetheless, you need to add
3067 a few more parameters to the link command line, depending on the exception
3070 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3071 to the libgcc libraries are required:
3076 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3077 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3080 Where CC is the name of the non-GNU C++ compiler.
3082 If the @code{zero cost} exception mechanism is used, and the platform
3083 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3084 paths to more objects are required:
3089 CC `gcc -print-file-name=crtbegin.o` $* \
3090 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3091 `gcc -print-file-name=crtend.o`
3092 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3095 If the @code{zero cost} exception mechanism is used, and the platform
3096 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3097 Tru64 or AIX), the simple approach described above will not work and
3098 a pre-linking phase using GNAT will be necessary.
3102 @node A Simple Example
3103 @subsection A Simple Example
3105 The following example, provided as part of the GNAT examples, shows how
3106 to achieve procedural interfacing between Ada and C++ in both
3107 directions. The C++ class A has two methods. The first method is exported
3108 to Ada by the means of an extern C wrapper function. The second method
3109 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3110 a limited record with a layout comparable to the C++ class. The Ada
3111 subprogram, in turn, calls the C++ method. So, starting from the C++
3112 main program, the process passes back and forth between the two
3116 Here are the compilation commands:
3118 $ gnatmake -c simple_cpp_interface
3121 $ gnatbind -n simple_cpp_interface
3122 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3123 -lstdc++ ex7.o cpp_main.o
3127 Here are the corresponding sources:
3135 void adainit (void);
3136 void adafinal (void);
3137 void method1 (A *t);
3159 class A : public Origin @{
3161 void method1 (void);
3162 void method2 (int v);
3172 extern "C" @{ void ada_method2 (A *t, int v);@}
3174 void A::method1 (void)
3177 printf ("in A::method1, a_value = %d \n",a_value);
3181 void A::method2 (int v)
3183 ada_method2 (this, v);
3184 printf ("in A::method2, a_value = %d \n",a_value);
3191 printf ("in A::A, a_value = %d \n",a_value);
3195 @smallexample @c ada
3197 package body Simple_Cpp_Interface is
3199 procedure Ada_Method2 (This : in out A; V : Integer) is
3205 end Simple_Cpp_Interface;
3208 package Simple_Cpp_Interface is
3211 Vptr : System.Address;
3215 pragma Convention (C, A);
3217 procedure Method1 (This : in out A);
3218 pragma Import (C, Method1);
3220 procedure Ada_Method2 (This : in out A; V : Integer);
3221 pragma Export (C, Ada_Method2);
3223 end Simple_Cpp_Interface;
3226 @node Interfacing with C++ at the Class Level
3227 @subsection Interfacing with C++ at the Class Level
3229 In this section we demonstrate the GNAT features for interfacing with
3230 C++ by means of an example making use of Ada 2005 abstract interface
3231 types. This example consists of a classification of animals; classes
3232 have been used to model our main classification of animals, and
3233 interfaces provide support for the management of secondary
3234 classifications. We first demonstrate a case in which the types and
3235 constructors are defined on the C++ side and imported from the Ada
3236 side, and latter the reverse case.
3238 The root of our derivation will be the @code{Animal} class, with a
3239 single private attribute (the @code{Age} of the animal) and two public
3240 primitives to set and get the value of this attribute.
3245 @b{virtual} void Set_Age (int New_Age);
3246 @b{virtual} int Age ();
3252 Abstract interface types are defined in C++ by means of classes with pure
3253 virtual functions and no data members. In our example we will use two
3254 interfaces that provide support for the common management of @code{Carnivore}
3255 and @code{Domestic} animals:
3258 @b{class} Carnivore @{
3260 @b{virtual} int Number_Of_Teeth () = 0;
3263 @b{class} Domestic @{
3265 @b{virtual void} Set_Owner (char* Name) = 0;
3269 Using these declarations, we can now say that a @code{Dog} is an animal that is
3270 both Carnivore and Domestic, that is:
3273 @b{class} Dog : Animal, Carnivore, Domestic @{
3275 @b{virtual} int Number_Of_Teeth ();
3276 @b{virtual} void Set_Owner (char* Name);
3278 Dog(); // Constructor
3285 In the following examples we will assume that the previous declarations are
3286 located in a file named @code{animals.h}. The following package demonstrates
3287 how to import these C++ declarations from the Ada side:
3289 @smallexample @c ada
3290 with Interfaces.C.Strings; use Interfaces.C.Strings;
3292 type Carnivore is interface;
3293 pragma Convention (C_Plus_Plus, Carnivore);
3294 function Number_Of_Teeth (X : Carnivore)
3295 return Natural is abstract;
3297 type Domestic is interface;
3298 pragma Convention (C_Plus_Plus, Set_Owner);
3300 (X : in out Domestic;
3301 Name : Chars_Ptr) is abstract;
3303 type Animal is tagged record
3306 pragma Import (C_Plus_Plus, Animal);
3308 procedure Set_Age (X : in out Animal; Age : Integer);
3309 pragma Import (C_Plus_Plus, Set_Age);
3311 function Age (X : Animal) return Integer;
3312 pragma Import (C_Plus_Plus, Age);
3314 type Dog is new Animal and Carnivore and Domestic with record
3315 Tooth_Count : Natural;
3316 Owner : String (1 .. 30);
3318 pragma Import (C_Plus_Plus, Dog);
3320 function Number_Of_Teeth (A : Dog) return Integer;
3321 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3323 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3324 pragma Import (C_Plus_Plus, Set_Owner);
3326 function New_Dog return Dog'Class;
3327 pragma CPP_Constructor (New_Dog);
3328 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3332 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3333 interfacing with these C++ classes is easy. The only requirement is that all
3334 the primitives and components must be declared exactly in the same order in
3337 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3338 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3339 the arguments to the called primitives will be the same as for C++. For the
3340 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3341 to indicate that they have been defined on the C++ side; this is required
3342 because the dispatch table associated with these tagged types will be built
3343 in the C++ side and therefore will not contain the predefined Ada primitives
3344 which Ada would otherwise expect.
3346 As the reader can see there is no need to indicate the C++ mangled names
3347 associated with each subprogram because it is assumed that all the calls to
3348 these primitives will be dispatching calls. The only exception is the
3349 constructor, which must be registered with the compiler by means of
3350 @code{pragma CPP_Constructor} and needs to provide its associated C++
3351 mangled name because the Ada compiler generates direct calls to it.
3353 With the above packages we can now declare objects of type Dog on the Ada side
3354 and dispatch calls to the corresponding subprograms on the C++ side. We can
3355 also extend the tagged type Dog with further fields and primitives, and
3356 override some of its C++ primitives on the Ada side. For example, here we have
3357 a type derivation defined on the Ada side that inherits all the dispatching
3358 primitives of the ancestor from the C++ side.
3361 @b{with} Animals; @b{use} Animals;
3362 @b{package} Vaccinated_Animals @b{is}
3363 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3364 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3365 @b{end} Vaccinated_Animals;
3368 It is important to note that, because of the ABI compatibility, the programmer
3369 does not need to add any further information to indicate either the object
3370 layout or the dispatch table entry associated with each dispatching operation.
3372 Now let us define all the types and constructors on the Ada side and export
3373 them to C++, using the same hierarchy of our previous example:
3375 @smallexample @c ada
3376 with Interfaces.C.Strings;
3377 use Interfaces.C.Strings;
3379 type Carnivore is interface;
3380 pragma Convention (C_Plus_Plus, Carnivore);
3381 function Number_Of_Teeth (X : Carnivore)
3382 return Natural is abstract;
3384 type Domestic is interface;
3385 pragma Convention (C_Plus_Plus, Set_Owner);
3387 (X : in out Domestic;
3388 Name : Chars_Ptr) is abstract;
3390 type Animal is tagged record
3393 pragma Convention (C_Plus_Plus, Animal);
3395 procedure Set_Age (X : in out Animal; Age : Integer);
3396 pragma Export (C_Plus_Plus, Set_Age);
3398 function Age (X : Animal) return Integer;
3399 pragma Export (C_Plus_Plus, Age);
3401 type Dog is new Animal and Carnivore and Domestic with record
3402 Tooth_Count : Natural;
3403 Owner : String (1 .. 30);
3405 pragma Convention (C_Plus_Plus, Dog);
3407 function Number_Of_Teeth (A : Dog) return Integer;
3408 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3410 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3411 pragma Export (C_Plus_Plus, Set_Owner);
3413 function New_Dog return Dog'Class;
3414 pragma Export (C_Plus_Plus, New_Dog);
3418 Compared with our previous example the only difference is the use of
3419 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3420 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3421 nothing else to be done; as explained above, the only requirement is that all
3422 the primitives and components are declared in exactly the same order.
3424 For completeness, let us see a brief C++ main program that uses the
3425 declarations available in @code{animals.h} (presented in our first example) to
3426 import and use the declarations from the Ada side, properly initializing and
3427 finalizing the Ada run-time system along the way:
3430 @b{#include} "animals.h"
3431 @b{#include} <iostream>
3432 @b{using namespace} std;
3434 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3435 void Check_Domestic (Domestic *obj) @{@dots{}@}
3436 void Check_Animal (Animal *obj) @{@dots{}@}
3437 void Check_Dog (Dog *obj) @{@dots{}@}
3440 void adainit (void);
3441 void adafinal (void);
3447 Dog *obj = new_dog(); // Ada constructor
3448 Check_Carnivore (obj); // Check secondary DT
3449 Check_Domestic (obj); // Check secondary DT
3450 Check_Animal (obj); // Check primary DT
3451 Check_Dog (obj); // Check primary DT
3456 adainit (); test(); adafinal ();
3461 @node Comparison between GNAT and C/C++ Compilation Models
3462 @section Comparison between GNAT and C/C++ Compilation Models
3465 The GNAT model of compilation is close to the C and C++ models. You can
3466 think of Ada specs as corresponding to header files in C. As in C, you
3467 don't need to compile specs; they are compiled when they are used. The
3468 Ada @code{with} is similar in effect to the @code{#include} of a C
3471 One notable difference is that, in Ada, you may compile specs separately
3472 to check them for semantic and syntactic accuracy. This is not always
3473 possible with C headers because they are fragments of programs that have
3474 less specific syntactic or semantic rules.
3476 The other major difference is the requirement for running the binder,
3477 which performs two important functions. First, it checks for
3478 consistency. In C or C++, the only defense against assembling
3479 inconsistent programs lies outside the compiler, in a makefile, for
3480 example. The binder satisfies the Ada requirement that it be impossible
3481 to construct an inconsistent program when the compiler is used in normal
3484 @cindex Elaboration order control
3485 The other important function of the binder is to deal with elaboration
3486 issues. There are also elaboration issues in C++ that are handled
3487 automatically. This automatic handling has the advantage of being
3488 simpler to use, but the C++ programmer has no control over elaboration.
3489 Where @code{gnatbind} might complain there was no valid order of
3490 elaboration, a C++ compiler would simply construct a program that
3491 malfunctioned at run time.
3494 @node Comparison between GNAT and Conventional Ada Library Models
3495 @section Comparison between GNAT and Conventional Ada Library Models
3498 This section is intended for Ada programmers who have
3499 used an Ada compiler implementing the traditional Ada library
3500 model, as described in the Ada Reference Manual.
3502 @cindex GNAT library
3503 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3504 source files themselves acts as the library. Compiling Ada programs does
3505 not generate any centralized information, but rather an object file and
3506 a ALI file, which are of interest only to the binder and linker.
3507 In a traditional system, the compiler reads information not only from
3508 the source file being compiled, but also from the centralized library.
3509 This means that the effect of a compilation depends on what has been
3510 previously compiled. In particular:
3514 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3515 to the version of the unit most recently compiled into the library.
3518 Inlining is effective only if the necessary body has already been
3519 compiled into the library.
3522 Compiling a unit may obsolete other units in the library.
3526 In GNAT, compiling one unit never affects the compilation of any other
3527 units because the compiler reads only source files. Only changes to source
3528 files can affect the results of a compilation. In particular:
3532 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3533 to the source version of the unit that is currently accessible to the
3538 Inlining requires the appropriate source files for the package or
3539 subprogram bodies to be available to the compiler. Inlining is always
3540 effective, independent of the order in which units are complied.
3543 Compiling a unit never affects any other compilations. The editing of
3544 sources may cause previous compilations to be out of date if they
3545 depended on the source file being modified.
3549 The most important result of these differences is that order of compilation
3550 is never significant in GNAT. There is no situation in which one is
3551 required to do one compilation before another. What shows up as order of
3552 compilation requirements in the traditional Ada library becomes, in
3553 GNAT, simple source dependencies; in other words, there is only a set
3554 of rules saying what source files must be present when a file is
3558 @node Placement of temporary files
3559 @section Placement of temporary files
3560 @cindex Temporary files (user control over placement)
3563 GNAT creates temporary files in the directory designated by the environment
3564 variable @env{TMPDIR}.
3565 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3566 for detailed information on how environment variables are resolved.
3567 For most users the easiest way to make use of this feature is to simply
3568 define @env{TMPDIR} as a job level logical name).
3569 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3570 for compiler temporary files, then you can include something like the
3571 following command in your @file{LOGIN.COM} file:
3574 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3578 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3579 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3580 designated by @env{TEMP}.
3581 If none of these environment variables are defined then GNAT uses the
3582 directory designated by the logical name @code{SYS$SCRATCH:}
3583 (by default the user's home directory). If all else fails
3584 GNAT uses the current directory for temporary files.
3587 @c *************************
3588 @node Compiling Using gcc
3589 @chapter Compiling Using @command{gcc}
3592 This chapter discusses how to compile Ada programs using the @command{gcc}
3593 command. It also describes the set of switches
3594 that can be used to control the behavior of the compiler.
3596 * Compiling Programs::
3597 * Switches for gcc::
3598 * Search Paths and the Run-Time Library (RTL)::
3599 * Order of Compilation Issues::
3603 @node Compiling Programs
3604 @section Compiling Programs
3607 The first step in creating an executable program is to compile the units
3608 of the program using the @command{gcc} command. You must compile the
3613 the body file (@file{.adb}) for a library level subprogram or generic
3617 the spec file (@file{.ads}) for a library level package or generic
3618 package that has no body
3621 the body file (@file{.adb}) for a library level package
3622 or generic package that has a body
3627 You need @emph{not} compile the following files
3632 the spec of a library unit which has a body
3639 because they are compiled as part of compiling related units. GNAT
3641 when the corresponding body is compiled, and subunits when the parent is
3644 @cindex cannot generate code
3645 If you attempt to compile any of these files, you will get one of the
3646 following error messages (where @var{fff} is the name of the file you compiled):
3649 cannot generate code for file @var{fff} (package spec)
3650 to check package spec, use -gnatc
3652 cannot generate code for file @var{fff} (missing subunits)
3653 to check parent unit, use -gnatc
3655 cannot generate code for file @var{fff} (subprogram spec)
3656 to check subprogram spec, use -gnatc
3658 cannot generate code for file @var{fff} (subunit)
3659 to check subunit, use -gnatc
3663 As indicated by the above error messages, if you want to submit
3664 one of these files to the compiler to check for correct semantics
3665 without generating code, then use the @option{-gnatc} switch.
3667 The basic command for compiling a file containing an Ada unit is
3670 $ gcc -c @ovar{switches} @file{file name}
3674 where @var{file name} is the name of the Ada file (usually
3676 @file{.ads} for a spec or @file{.adb} for a body).
3679 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3681 The result of a successful compilation is an object file, which has the
3682 same name as the source file but an extension of @file{.o} and an Ada
3683 Library Information (ALI) file, which also has the same name as the
3684 source file, but with @file{.ali} as the extension. GNAT creates these
3685 two output files in the current directory, but you may specify a source
3686 file in any directory using an absolute or relative path specification
3687 containing the directory information.
3690 @command{gcc} is actually a driver program that looks at the extensions of
3691 the file arguments and loads the appropriate compiler. For example, the
3692 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3693 These programs are in directories known to the driver program (in some
3694 configurations via environment variables you set), but need not be in
3695 your path. The @command{gcc} driver also calls the assembler and any other
3696 utilities needed to complete the generation of the required object
3699 It is possible to supply several file names on the same @command{gcc}
3700 command. This causes @command{gcc} to call the appropriate compiler for
3701 each file. For example, the following command lists three separate
3702 files to be compiled:
3705 $ gcc -c x.adb y.adb z.c
3709 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3710 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3711 The compiler generates three object files @file{x.o}, @file{y.o} and
3712 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3713 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3716 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3719 @node Switches for gcc
3720 @section Switches for @command{gcc}
3723 The @command{gcc} command accepts switches that control the
3724 compilation process. These switches are fully described in this section.
3725 First we briefly list all the switches, in alphabetical order, then we
3726 describe the switches in more detail in functionally grouped sections.
3728 More switches exist for GCC than those documented here, especially
3729 for specific targets. However, their use is not recommended as
3730 they may change code generation in ways that are incompatible with
3731 the Ada run-time library, or can cause inconsistencies between
3735 * Output and Error Message Control::
3736 * Warning Message Control::
3737 * Debugging and Assertion Control::
3738 * Validity Checking::
3741 * Using gcc for Syntax Checking::
3742 * Using gcc for Semantic Checking::
3743 * Compiling Different Versions of Ada::
3744 * Character Set Control::
3745 * File Naming Control::
3746 * Subprogram Inlining Control::
3747 * Auxiliary Output Control::
3748 * Debugging Control::
3749 * Exception Handling Control::
3750 * Units to Sources Mapping Files::
3751 * Integrated Preprocessing::
3752 * Code Generation Control::
3761 @cindex @option{-b} (@command{gcc})
3762 @item -b @var{target}
3763 Compile your program to run on @var{target}, which is the name of a
3764 system configuration. You must have a GNAT cross-compiler built if
3765 @var{target} is not the same as your host system.
3768 @cindex @option{-B} (@command{gcc})
3769 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3770 from @var{dir} instead of the default location. Only use this switch
3771 when multiple versions of the GNAT compiler are available.
3772 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3773 GNU Compiler Collection (GCC)}, for further details. You would normally
3774 use the @option{-b} or @option{-V} switch instead.
3777 @cindex @option{-c} (@command{gcc})
3778 Compile. Always use this switch when compiling Ada programs.
3780 Note: for some other languages when using @command{gcc}, notably in
3781 the case of C and C++, it is possible to use
3782 use @command{gcc} without a @option{-c} switch to
3783 compile and link in one step. In the case of GNAT, you
3784 cannot use this approach, because the binder must be run
3785 and @command{gcc} cannot be used to run the GNAT binder.
3789 @cindex @option{-fno-inline} (@command{gcc})
3790 Suppresses all back-end inlining, even if other optimization or inlining
3792 This includes suppression of inlining that results
3793 from the use of the pragma @code{Inline_Always}.
3794 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3795 are ignored, and @option{-gnatn} and @option{-gnatN} have no
3796 effect if this switch is present.
3798 @item -fno-inline-functions
3799 @cindex @option{-fno-inline-functions} (@command{gcc})
3800 Suppresses automatic inlining of small subprograms, which is enabled
3801 if @option{-O3} is used.
3803 @item -fno-inline-functions-called-once
3804 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
3805 Suppresses inlining of subprograms local to the unit and called once
3806 from within it, which is enabled if @option{-O1} is used.
3808 @item -fno-strict-aliasing
3809 @cindex @option{-fno-strict-aliasing} (@command{gcc})
3810 Causes the compiler to avoid assumptions regarding non-aliasing
3811 of objects of different types. See
3812 @ref{Optimization and Strict Aliasing} for details.
3815 @cindex @option{-fstack-check} (@command{gcc})
3816 Activates stack checking.
3817 See @ref{Stack Overflow Checking} for details.
3820 @cindex @option{-fstack-usage} (@command{gcc})
3821 Makes the compiler output stack usage information for the program, on a
3822 per-function basis. See @ref{Static Stack Usage Analysis} for details.
3824 @item -fcallgraph-info@r{[}=su@r{]}
3825 @cindex @option{-fcallgraph-info} (@command{gcc})
3826 Makes the compiler output callgraph information for the program, on a
3827 per-file basis. The information is generated in the VCG format. It can
3828 be decorated with stack-usage per-node information.
3831 @cindex @option{^-g^/DEBUG^} (@command{gcc})
3832 Generate debugging information. This information is stored in the object
3833 file and copied from there to the final executable file by the linker,
3834 where it can be read by the debugger. You must use the
3835 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3838 @cindex @option{-gnat83} (@command{gcc})
3839 Enforce Ada 83 restrictions.
3842 @cindex @option{-gnat95} (@command{gcc})
3843 Enforce Ada 95 restrictions.
3846 @cindex @option{-gnat05} (@command{gcc})
3847 Allow full Ada 2005 features.
3850 @cindex @option{-gnata} (@command{gcc})
3851 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3852 activated. Note that these pragmas can also be controlled using the
3853 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
3854 It also activates pragmas @code{Check}, @code{Precondition}, and
3855 @code{Postcondition}. Note that these pragmas can also be controlled
3856 using the configuration pragma @code{Check_Policy}.
3859 @cindex @option{-gnatA} (@command{gcc})
3860 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
3864 @cindex @option{-gnatb} (@command{gcc})
3865 Generate brief messages to @file{stderr} even if verbose mode set.
3868 @cindex @option{-gnatB} (@command{gcc})
3869 Assume no invalid (bad) values except for 'Valid attribute use.
3872 @cindex @option{-gnatc} (@command{gcc})
3873 Check syntax and semantics only (no code generation attempted).
3876 @cindex @option{-gnatd} (@command{gcc})
3877 Specify debug options for the compiler. The string of characters after
3878 the @option{-gnatd} specify the specific debug options. The possible
3879 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3880 compiler source file @file{debug.adb} for details of the implemented
3881 debug options. Certain debug options are relevant to applications
3882 programmers, and these are documented at appropriate points in this
3886 @cindex @option{-gnatD[nn]} (@command{gcc})
3887 Create expanded source files for source level debugging. This switch
3888 also suppress generation of cross-reference information
3889 (see @option{-gnatx}).
3891 @item -gnatec=@var{path}
3892 @cindex @option{-gnatec} (@command{gcc})
3893 Specify a configuration pragma file
3895 (the equal sign is optional)
3897 (@pxref{The Configuration Pragmas Files}).
3899 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
3900 @cindex @option{-gnateD} (@command{gcc})
3901 Defines a symbol, associated with @var{value}, for preprocessing.
3902 (@pxref{Integrated Preprocessing}).
3905 @cindex @option{-gnatef} (@command{gcc})
3906 Display full source path name in brief error messages.
3909 @cindex @option{-gnateG} (@command{gcc})
3910 Save result of preprocessing in a text file.
3912 @item -gnatem=@var{path}
3913 @cindex @option{-gnatem} (@command{gcc})
3914 Specify a mapping file
3916 (the equal sign is optional)
3918 (@pxref{Units to Sources Mapping Files}).
3920 @item -gnatep=@var{file}
3921 @cindex @option{-gnatep} (@command{gcc})
3922 Specify a preprocessing data file
3924 (the equal sign is optional)
3926 (@pxref{Integrated Preprocessing}).
3929 @cindex @option{-gnatE} (@command{gcc})
3930 Full dynamic elaboration checks.
3933 @cindex @option{-gnatf} (@command{gcc})
3934 Full errors. Multiple errors per line, all undefined references, do not
3935 attempt to suppress cascaded errors.
3938 @cindex @option{-gnatF} (@command{gcc})
3939 Externals names are folded to all uppercase.
3941 @item ^-gnatg^/GNAT_INTERNAL^
3942 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
3943 Internal GNAT implementation mode. This should not be used for
3944 applications programs, it is intended only for use by the compiler
3945 and its run-time library. For documentation, see the GNAT sources.
3946 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
3947 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
3948 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
3949 so that all standard warnings and all standard style options are turned on.
3950 All warnings and style error messages are treated as errors.
3953 @cindex @option{-gnatG[nn]} (@command{gcc})
3954 List generated expanded code in source form.
3956 @item ^-gnath^/HELP^
3957 @cindex @option{^-gnath^/HELP^} (@command{gcc})
3958 Output usage information. The output is written to @file{stdout}.
3960 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3961 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
3962 Identifier character set
3964 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3966 For details of the possible selections for @var{c},
3967 see @ref{Character Set Control}.
3969 @item ^-gnatI^/IGNORE_REP_CLAUSES^
3970 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
3971 Ignore representation clauses. When this switch is used, all
3972 representation clauses are treated as comments. This is useful
3973 when initially porting code where you want to ignore rep clause
3974 problems, and also for compiling foreign code (particularly
3978 @cindex @option{-gnatjnn} (@command{gcc})
3979 Reformat error messages to fit on nn character lines
3981 @item -gnatk=@var{n}
3982 @cindex @option{-gnatk} (@command{gcc})
3983 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3986 @cindex @option{-gnatl} (@command{gcc})
3987 Output full source listing with embedded error messages.
3990 @cindex @option{-gnatL} (@command{gcc})
3991 Used in conjunction with -gnatG or -gnatD to intersperse original
3992 source lines (as comment lines with line numbers) in the expanded
3995 @item -gnatm=@var{n}
3996 @cindex @option{-gnatm} (@command{gcc})
3997 Limit number of detected error or warning messages to @var{n}
3998 where @var{n} is in the range 1..999_999. The default setting if
3999 no switch is given is 9999. Compilation is terminated if this
4000 limit is exceeded. The equal sign here is optional.
4003 @cindex @option{-gnatn} (@command{gcc})
4004 Activate inlining for subprograms for which
4005 pragma @code{inline} is specified. This inlining is performed
4006 by the GCC back-end.
4009 @cindex @option{-gnatN} (@command{gcc})
4010 Activate front end inlining for subprograms for which
4011 pragma @code{Inline} is specified. This inlining is performed
4012 by the front end and will be visible in the
4013 @option{-gnatG} output.
4015 When using a gcc-based back end (in practice this means using any version
4016 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4017 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4018 Historically front end inlining was more extensive than the gcc back end
4019 inlining, but that is no longer the case.
4022 @cindex @option{-gnato} (@command{gcc})
4023 Enable numeric overflow checking (which is not normally enabled by
4024 default). Note that division by zero is a separate check that is not
4025 controlled by this switch (division by zero checking is on by default).
4028 @cindex @option{-gnatp} (@command{gcc})
4029 Suppress all checks. See @ref{Run-Time Checks} for details.
4032 @cindex @option{-gnatP} (@command{gcc})
4033 Enable polling. This is required on some systems (notably Windows NT) to
4034 obtain asynchronous abort and asynchronous transfer of control capability.
4035 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4039 @cindex @option{-gnatq} (@command{gcc})
4040 Don't quit. Try semantics, even if parse errors.
4043 @cindex @option{-gnatQ} (@command{gcc})
4044 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4047 @cindex @option{-gnatr} (@command{gcc})
4048 Treat pragma Restrictions as Restriction_Warnings.
4050 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4051 @cindex @option{-gnatR} (@command{gcc})
4052 Output representation information for declared types and objects.
4055 @cindex @option{-gnats} (@command{gcc})
4059 @cindex @option{-gnatS} (@command{gcc})
4060 Print package Standard.
4063 @cindex @option{-gnatt} (@command{gcc})
4064 Generate tree output file.
4066 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4067 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4068 All compiler tables start at @var{nnn} times usual starting size.
4071 @cindex @option{-gnatu} (@command{gcc})
4072 List units for this compilation.
4075 @cindex @option{-gnatU} (@command{gcc})
4076 Tag all error messages with the unique string ``error:''
4079 @cindex @option{-gnatv} (@command{gcc})
4080 Verbose mode. Full error output with source lines to @file{stdout}.
4083 @cindex @option{-gnatV} (@command{gcc})
4084 Control level of validity checking. See separate section describing
4087 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4088 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4090 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4091 the exact warnings that
4092 are enabled or disabled (@pxref{Warning Message Control}).
4094 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4095 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4096 Wide character encoding method
4098 (@var{e}=n/h/u/s/e/8).
4101 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4105 @cindex @option{-gnatx} (@command{gcc})
4106 Suppress generation of cross-reference information.
4108 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4109 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4110 Enable built-in style checks (@pxref{Style Checking}).
4112 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4113 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4114 Distribution stub generation and compilation
4116 (@var{m}=r/c for receiver/caller stubs).
4119 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4120 to be generated and compiled).
4123 @item ^-I^/SEARCH=^@var{dir}
4124 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4126 Direct GNAT to search the @var{dir} directory for source files needed by
4127 the current compilation
4128 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4130 @item ^-I-^/NOCURRENT_DIRECTORY^
4131 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4133 Except for the source file named in the command line, do not look for source
4134 files in the directory containing the source file named in the command line
4135 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4139 @cindex @option{-mbig-switch} (@command{gcc})
4140 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4141 This standard gcc switch causes the compiler to use larger offsets in its
4142 jump table representation for @code{case} statements.
4143 This may result in less efficient code, but is sometimes necessary
4144 (for example on HP-UX targets)
4145 @cindex HP-UX and @option{-mbig-switch} option
4146 in order to compile large and/or nested @code{case} statements.
4149 @cindex @option{-o} (@command{gcc})
4150 This switch is used in @command{gcc} to redirect the generated object file
4151 and its associated ALI file. Beware of this switch with GNAT, because it may
4152 cause the object file and ALI file to have different names which in turn
4153 may confuse the binder and the linker.
4157 @cindex @option{-nostdinc} (@command{gcc})
4158 Inhibit the search of the default location for the GNAT Run Time
4159 Library (RTL) source files.
4162 @cindex @option{-nostdlib} (@command{gcc})
4163 Inhibit the search of the default location for the GNAT Run Time
4164 Library (RTL) ALI files.
4168 @cindex @option{-O} (@command{gcc})
4169 @var{n} controls the optimization level.
4173 No optimization, the default setting if no @option{-O} appears
4176 Normal optimization, the default if you specify @option{-O} without
4177 an operand. A good compromise between code quality and compilation
4181 Extensive optimization, may improve execution time, possibly at the cost of
4182 substantially increased compilation time.
4185 Same as @option{-O2}, and also includes inline expansion for small subprograms
4189 Optimize space usage
4193 See also @ref{Optimization Levels}.
4198 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4199 Equivalent to @option{/OPTIMIZE=NONE}.
4200 This is the default behavior in the absence of an @option{/OPTIMIZE}
4203 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4204 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4205 Selects the level of optimization for your program. The supported
4206 keywords are as follows:
4209 Perform most optimizations, including those that
4211 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4212 without keyword options.
4215 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4218 Perform some optimizations, but omit ones that are costly.
4221 Same as @code{SOME}.
4224 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4225 automatic inlining of small subprograms within a unit
4228 Try to unroll loops. This keyword may be specified together with
4229 any keyword above other than @code{NONE}. Loop unrolling
4230 usually, but not always, improves the performance of programs.
4233 Optimize space usage
4237 See also @ref{Optimization Levels}.
4241 @item -pass-exit-codes
4242 @cindex @option{-pass-exit-codes} (@command{gcc})
4243 Catch exit codes from the compiler and use the most meaningful as
4247 @item --RTS=@var{rts-path}
4248 @cindex @option{--RTS} (@command{gcc})
4249 Specifies the default location of the runtime library. Same meaning as the
4250 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4253 @cindex @option{^-S^/ASM^} (@command{gcc})
4254 ^Used in place of @option{-c} to^Used to^
4255 cause the assembler source file to be
4256 generated, using @file{^.s^.S^} as the extension,
4257 instead of the object file.
4258 This may be useful if you need to examine the generated assembly code.
4260 @item ^-fverbose-asm^/VERBOSE_ASM^
4261 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4262 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4263 to cause the generated assembly code file to be annotated with variable
4264 names, making it significantly easier to follow.
4267 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4268 Show commands generated by the @command{gcc} driver. Normally used only for
4269 debugging purposes or if you need to be sure what version of the
4270 compiler you are executing.
4274 @cindex @option{-V} (@command{gcc})
4275 Execute @var{ver} version of the compiler. This is the @command{gcc}
4276 version, not the GNAT version.
4279 @item ^-w^/NO_BACK_END_WARNINGS^
4280 @cindex @option{-w} (@command{gcc})
4281 Turn off warnings generated by the back end of the compiler. Use of
4282 this switch also causes the default for front end warnings to be set
4283 to suppress (as though @option{-gnatws} had appeared at the start of
4289 @c Combining qualifiers does not work on VMS
4290 You may combine a sequence of GNAT switches into a single switch. For
4291 example, the combined switch
4293 @cindex Combining GNAT switches
4299 is equivalent to specifying the following sequence of switches:
4302 -gnato -gnatf -gnati3
4307 The following restrictions apply to the combination of switches
4312 The switch @option{-gnatc} if combined with other switches must come
4313 first in the string.
4316 The switch @option{-gnats} if combined with other switches must come
4317 first in the string.
4321 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4322 may not be combined with any other switches.
4326 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4327 switch), then all further characters in the switch are interpreted
4328 as style modifiers (see description of @option{-gnaty}).
4331 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4332 switch), then all further characters in the switch are interpreted
4333 as debug flags (see description of @option{-gnatd}).
4336 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4337 switch), then all further characters in the switch are interpreted
4338 as warning mode modifiers (see description of @option{-gnatw}).
4341 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4342 switch), then all further characters in the switch are interpreted
4343 as validity checking options (see description of @option{-gnatV}).
4347 @node Output and Error Message Control
4348 @subsection Output and Error Message Control
4352 The standard default format for error messages is called ``brief format''.
4353 Brief format messages are written to @file{stderr} (the standard error
4354 file) and have the following form:
4357 e.adb:3:04: Incorrect spelling of keyword "function"
4358 e.adb:4:20: ";" should be "is"
4362 The first integer after the file name is the line number in the file,
4363 and the second integer is the column number within the line.
4365 @code{GPS} can parse the error messages
4366 and point to the referenced character.
4368 The following switches provide control over the error message
4374 @cindex @option{-gnatv} (@command{gcc})
4377 The v stands for verbose.
4379 The effect of this setting is to write long-format error
4380 messages to @file{stdout} (the standard output file.
4381 The same program compiled with the
4382 @option{-gnatv} switch would generate:
4386 3. funcion X (Q : Integer)
4388 >>> Incorrect spelling of keyword "function"
4391 >>> ";" should be "is"
4396 The vertical bar indicates the location of the error, and the @samp{>>>}
4397 prefix can be used to search for error messages. When this switch is
4398 used the only source lines output are those with errors.
4401 @cindex @option{-gnatl} (@command{gcc})
4403 The @code{l} stands for list.
4405 This switch causes a full listing of
4406 the file to be generated. In the case where a body is
4407 compiled, the corresponding spec is also listed, along
4408 with any subunits. Typical output from compiling a package
4409 body @file{p.adb} might look like:
4411 @smallexample @c ada
4415 1. package body p is
4417 3. procedure a is separate;
4428 2. pragma Elaborate_Body
4452 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4453 standard output is redirected, a brief summary is written to
4454 @file{stderr} (standard error) giving the number of error messages and
4455 warning messages generated.
4457 @item -^gnatl^OUTPUT_FILE^=file
4458 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4459 This has the same effect as @option{-gnatl} except that the output is
4460 written to a file instead of to standard output. If the given name
4461 @file{fname} does not start with a period, then it is the full name
4462 of the file to be written. If @file{fname} is an extension, it is
4463 appended to the name of the file being compiled. For example, if
4464 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4465 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4468 @cindex @option{-gnatU} (@command{gcc})
4469 This switch forces all error messages to be preceded by the unique
4470 string ``error:''. This means that error messages take a few more
4471 characters in space, but allows easy searching for and identification
4475 @cindex @option{-gnatb} (@command{gcc})
4477 The @code{b} stands for brief.
4479 This switch causes GNAT to generate the
4480 brief format error messages to @file{stderr} (the standard error
4481 file) as well as the verbose
4482 format message or full listing (which as usual is written to
4483 @file{stdout} (the standard output file).
4485 @item -gnatm=@var{n}
4486 @cindex @option{-gnatm} (@command{gcc})
4488 The @code{m} stands for maximum.
4490 @var{n} is a decimal integer in the
4491 range of 1 to 999 and limits the number of error messages to be
4492 generated. For example, using @option{-gnatm2} might yield
4495 e.adb:3:04: Incorrect spelling of keyword "function"
4496 e.adb:5:35: missing ".."
4497 fatal error: maximum errors reached
4498 compilation abandoned
4502 Note that the equal sign is optional, so the switches
4503 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4506 @cindex @option{-gnatf} (@command{gcc})
4507 @cindex Error messages, suppressing
4509 The @code{f} stands for full.
4511 Normally, the compiler suppresses error messages that are likely to be
4512 redundant. This switch causes all error
4513 messages to be generated. In particular, in the case of
4514 references to undefined variables. If a given variable is referenced
4515 several times, the normal format of messages is
4517 e.adb:7:07: "V" is undefined (more references follow)
4521 where the parenthetical comment warns that there are additional
4522 references to the variable @code{V}. Compiling the same program with the
4523 @option{-gnatf} switch yields
4526 e.adb:7:07: "V" is undefined
4527 e.adb:8:07: "V" is undefined
4528 e.adb:8:12: "V" is undefined
4529 e.adb:8:16: "V" is undefined
4530 e.adb:9:07: "V" is undefined
4531 e.adb:9:12: "V" is undefined
4535 The @option{-gnatf} switch also generates additional information for
4536 some error messages. Some examples are:
4540 Full details on entities not available in high integrity mode
4542 Details on possibly non-portable unchecked conversion
4544 List possible interpretations for ambiguous calls
4546 Additional details on incorrect parameters
4550 @cindex @option{-gnatjnn} (@command{gcc})
4551 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4552 with continuation lines are treated as though the continuation lines were
4553 separate messages (and so a warning with two continuation lines counts as
4554 three warnings, and is listed as three separate messages).
4556 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4557 messages are output in a different manner. A message and all its continuation
4558 lines are treated as a unit, and count as only one warning or message in the
4559 statistics totals. Furthermore, the message is reformatted so that no line
4560 is longer than nn characters.
4563 @cindex @option{-gnatq} (@command{gcc})
4565 The @code{q} stands for quit (really ``don't quit'').
4567 In normal operation mode, the compiler first parses the program and
4568 determines if there are any syntax errors. If there are, appropriate
4569 error messages are generated and compilation is immediately terminated.
4571 GNAT to continue with semantic analysis even if syntax errors have been
4572 found. This may enable the detection of more errors in a single run. On
4573 the other hand, the semantic analyzer is more likely to encounter some
4574 internal fatal error when given a syntactically invalid tree.
4577 @cindex @option{-gnatQ} (@command{gcc})
4578 In normal operation mode, the @file{ALI} file is not generated if any
4579 illegalities are detected in the program. The use of @option{-gnatQ} forces
4580 generation of the @file{ALI} file. This file is marked as being in
4581 error, so it cannot be used for binding purposes, but it does contain
4582 reasonably complete cross-reference information, and thus may be useful
4583 for use by tools (e.g., semantic browsing tools or integrated development
4584 environments) that are driven from the @file{ALI} file. This switch
4585 implies @option{-gnatq}, since the semantic phase must be run to get a
4586 meaningful ALI file.
4588 In addition, if @option{-gnatt} is also specified, then the tree file is
4589 generated even if there are illegalities. It may be useful in this case
4590 to also specify @option{-gnatq} to ensure that full semantic processing
4591 occurs. The resulting tree file can be processed by ASIS, for the purpose
4592 of providing partial information about illegal units, but if the error
4593 causes the tree to be badly malformed, then ASIS may crash during the
4596 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4597 being in error, @command{gnatmake} will attempt to recompile the source when it
4598 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4600 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4601 since ALI files are never generated if @option{-gnats} is set.
4605 @node Warning Message Control
4606 @subsection Warning Message Control
4607 @cindex Warning messages
4609 In addition to error messages, which correspond to illegalities as defined
4610 in the Ada Reference Manual, the compiler detects two kinds of warning
4613 First, the compiler considers some constructs suspicious and generates a
4614 warning message to alert you to a possible error. Second, if the
4615 compiler detects a situation that is sure to raise an exception at
4616 run time, it generates a warning message. The following shows an example
4617 of warning messages:
4619 e.adb:4:24: warning: creation of object may raise Storage_Error
4620 e.adb:10:17: warning: static value out of range
4621 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4625 GNAT considers a large number of situations as appropriate
4626 for the generation of warning messages. As always, warnings are not
4627 definite indications of errors. For example, if you do an out-of-range
4628 assignment with the deliberate intention of raising a
4629 @code{Constraint_Error} exception, then the warning that may be
4630 issued does not indicate an error. Some of the situations for which GNAT
4631 issues warnings (at least some of the time) are given in the following
4632 list. This list is not complete, and new warnings are often added to
4633 subsequent versions of GNAT. The list is intended to give a general idea
4634 of the kinds of warnings that are generated.
4638 Possible infinitely recursive calls
4641 Out-of-range values being assigned
4644 Possible order of elaboration problems
4647 Assertions (pragma Assert) that are sure to fail
4653 Address clauses with possibly unaligned values, or where an attempt is
4654 made to overlay a smaller variable with a larger one.
4657 Fixed-point type declarations with a null range
4660 Direct_IO or Sequential_IO instantiated with a type that has access values
4663 Variables that are never assigned a value
4666 Variables that are referenced before being initialized
4669 Task entries with no corresponding @code{accept} statement
4672 Duplicate accepts for the same task entry in a @code{select}
4675 Objects that take too much storage
4678 Unchecked conversion between types of differing sizes
4681 Missing @code{return} statement along some execution path in a function
4684 Incorrect (unrecognized) pragmas
4687 Incorrect external names
4690 Allocation from empty storage pool
4693 Potentially blocking operation in protected type
4696 Suspicious parenthesization of expressions
4699 Mismatching bounds in an aggregate
4702 Attempt to return local value by reference
4705 Premature instantiation of a generic body
4708 Attempt to pack aliased components
4711 Out of bounds array subscripts
4714 Wrong length on string assignment
4717 Violations of style rules if style checking is enabled
4720 Unused @code{with} clauses
4723 @code{Bit_Order} usage that does not have any effect
4726 @code{Standard.Duration} used to resolve universal fixed expression
4729 Dereference of possibly null value
4732 Declaration that is likely to cause storage error
4735 Internal GNAT unit @code{with}'ed by application unit
4738 Values known to be out of range at compile time
4741 Unreferenced labels and variables
4744 Address overlays that could clobber memory
4747 Unexpected initialization when address clause present
4750 Bad alignment for address clause
4753 Useless type conversions
4756 Redundant assignment statements and other redundant constructs
4759 Useless exception handlers
4762 Accidental hiding of name by child unit
4765 Access before elaboration detected at compile time
4768 A range in a @code{for} loop that is known to be null or might be null
4773 The following section lists compiler switches that are available
4774 to control the handling of warning messages. It is also possible
4775 to exercise much finer control over what warnings are issued and
4776 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
4777 gnat_rm, GNAT Reference manual}.
4782 @emph{Activate all optional errors.}
4783 @cindex @option{-gnatwa} (@command{gcc})
4784 This switch activates most optional warning messages, see remaining list
4785 in this section for details on optional warning messages that can be
4786 individually controlled. The warnings that are not turned on by this
4788 @option{-gnatwd} (implicit dereferencing),
4789 @option{-gnatwh} (hiding),
4790 @option{-gnatwl} (elaboration warnings),
4791 @option{-gnatw.o} (warn on values set by out parameters ignored)
4792 and @option{-gnatwt} (tracking of deleted conditional code).
4793 All other optional warnings are turned on.
4796 @emph{Suppress all optional errors.}
4797 @cindex @option{-gnatwA} (@command{gcc})
4798 This switch suppresses all optional warning messages, see remaining list
4799 in this section for details on optional warning messages that can be
4800 individually controlled.
4803 @emph{Activate warnings on failing assertions.}
4804 @cindex @option{-gnatw.a} (@command{gcc})
4805 @cindex Assert failures
4806 This switch activates warnings for assertions where the compiler can tell at
4807 compile time that the assertion will fail. Note that this warning is given
4808 even if assertions are disabled. The default is that such warnings are
4812 @emph{Suppress warnings on failing assertions.}
4813 @cindex @option{-gnatw.A} (@command{gcc})
4814 @cindex Assert failures
4815 This switch suppresses warnings for assertions where the compiler can tell at
4816 compile time that the assertion will fail.
4819 @emph{Activate warnings on bad fixed values.}
4820 @cindex @option{-gnatwb} (@command{gcc})
4821 @cindex Bad fixed values
4822 @cindex Fixed-point Small value
4824 This switch activates warnings for static fixed-point expressions whose
4825 value is not an exact multiple of Small. Such values are implementation
4826 dependent, since an implementation is free to choose either of the multiples
4827 that surround the value. GNAT always chooses the closer one, but this is not
4828 required behavior, and it is better to specify a value that is an exact
4829 multiple, ensuring predictable execution. The default is that such warnings
4833 @emph{Suppress warnings on bad fixed values.}
4834 @cindex @option{-gnatwB} (@command{gcc})
4835 This switch suppresses warnings for static fixed-point expressions whose
4836 value is not an exact multiple of Small.
4839 @emph{Activate warnings on biased representation.}
4840 @cindex @option{-gnatw.b} (@command{gcc})
4841 @cindex Biased representation
4842 This switch activates warnings when a size clause, value size clause, component
4843 clause, or component size clause forces the use of biased representation for an
4844 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
4845 to represent 10/11). The default is that such warnings are generated.
4848 @emph{Suppress warnings on biased representation.}
4849 @cindex @option{-gnatwB} (@command{gcc})
4850 This switch suppresses warnings for representation clauses that force the use
4851 of biased representation.
4854 @emph{Activate warnings on conditionals.}
4855 @cindex @option{-gnatwc} (@command{gcc})
4856 @cindex Conditionals, constant
4857 This switch activates warnings for conditional expressions used in
4858 tests that are known to be True or False at compile time. The default
4859 is that such warnings are not generated.
4860 Note that this warning does
4861 not get issued for the use of boolean variables or constants whose
4862 values are known at compile time, since this is a standard technique
4863 for conditional compilation in Ada, and this would generate too many
4864 false positive warnings.
4866 This warning option also activates a special test for comparisons using
4867 the operators ``>='' and`` <=''.
4868 If the compiler can tell that only the equality condition is possible,
4869 then it will warn that the ``>'' or ``<'' part of the test
4870 is useless and that the operator could be replaced by ``=''.
4871 An example would be comparing a @code{Natural} variable <= 0.
4873 This warning option also generates warnings if
4874 one or both tests is optimized away in a membership test for integer
4875 values if the result can be determined at compile time. Range tests on
4876 enumeration types are not included, since it is common for such tests
4877 to include an end point.
4879 This warning can also be turned on using @option{-gnatwa}.
4882 @emph{Suppress warnings on conditionals.}
4883 @cindex @option{-gnatwC} (@command{gcc})
4884 This switch suppresses warnings for conditional expressions used in
4885 tests that are known to be True or False at compile time.
4888 @emph{Activate warnings on missing component clauses.}
4889 @cindex @option{-gnatw.c} (@command{gcc})
4890 @cindex Component clause, missing
4891 This switch activates warnings for record components where a record
4892 representation clause is present and has component clauses for the
4893 majority, but not all, of the components. A warning is given for each
4894 component for which no component clause is present.
4896 This warning can also be turned on using @option{-gnatwa}.
4899 @emph{Suppress warnings on missing component clauses.}
4900 @cindex @option{-gnatwC} (@command{gcc})
4901 This switch suppresses warnings for record components that are
4902 missing a component clause in the situation described above.
4905 @emph{Activate warnings on implicit dereferencing.}
4906 @cindex @option{-gnatwd} (@command{gcc})
4907 If this switch is set, then the use of a prefix of an access type
4908 in an indexed component, slice, or selected component without an
4909 explicit @code{.all} will generate a warning. With this warning
4910 enabled, access checks occur only at points where an explicit
4911 @code{.all} appears in the source code (assuming no warnings are
4912 generated as a result of this switch). The default is that such
4913 warnings are not generated.
4914 Note that @option{-gnatwa} does not affect the setting of
4915 this warning option.
4918 @emph{Suppress warnings on implicit dereferencing.}
4919 @cindex @option{-gnatwD} (@command{gcc})
4920 @cindex Implicit dereferencing
4921 @cindex Dereferencing, implicit
4922 This switch suppresses warnings for implicit dereferences in
4923 indexed components, slices, and selected components.
4926 @emph{Treat warnings as errors.}
4927 @cindex @option{-gnatwe} (@command{gcc})
4928 @cindex Warnings, treat as error
4929 This switch causes warning messages to be treated as errors.
4930 The warning string still appears, but the warning messages are counted
4931 as errors, and prevent the generation of an object file.
4934 @emph{Activate every optional warning}
4935 @cindex @option{-gnatw.e} (@command{gcc})
4936 @cindex Warnings, activate every optional warning
4937 This switch activates all optional warnings, including those which
4938 are not activated by @code{-gnatwa}.
4941 @emph{Activate warnings on unreferenced formals.}
4942 @cindex @option{-gnatwf} (@command{gcc})
4943 @cindex Formals, unreferenced
4944 This switch causes a warning to be generated if a formal parameter
4945 is not referenced in the body of the subprogram. This warning can
4946 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
4947 default is that these warnings are not generated.
4950 @emph{Suppress warnings on unreferenced formals.}
4951 @cindex @option{-gnatwF} (@command{gcc})
4952 This switch suppresses warnings for unreferenced formal
4953 parameters. Note that the
4954 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4955 effect of warning on unreferenced entities other than subprogram
4959 @emph{Activate warnings on unrecognized pragmas.}
4960 @cindex @option{-gnatwg} (@command{gcc})
4961 @cindex Pragmas, unrecognized
4962 This switch causes a warning to be generated if an unrecognized
4963 pragma is encountered. Apart from issuing this warning, the
4964 pragma is ignored and has no effect. This warning can
4965 also be turned on using @option{-gnatwa}. The default
4966 is that such warnings are issued (satisfying the Ada Reference
4967 Manual requirement that such warnings appear).
4970 @emph{Suppress warnings on unrecognized pragmas.}
4971 @cindex @option{-gnatwG} (@command{gcc})
4972 This switch suppresses warnings for unrecognized pragmas.
4975 @emph{Activate warnings on hiding.}
4976 @cindex @option{-gnatwh} (@command{gcc})
4977 @cindex Hiding of Declarations
4978 This switch activates warnings on hiding declarations.
4979 A declaration is considered hiding
4980 if it is for a non-overloadable entity, and it declares an entity with the
4981 same name as some other entity that is directly or use-visible. The default
4982 is that such warnings are not generated.
4983 Note that @option{-gnatwa} does not affect the setting of this warning option.
4986 @emph{Suppress warnings on hiding.}
4987 @cindex @option{-gnatwH} (@command{gcc})
4988 This switch suppresses warnings on hiding declarations.
4991 @emph{Activate warnings on implementation units.}
4992 @cindex @option{-gnatwi} (@command{gcc})
4993 This switch activates warnings for a @code{with} of an internal GNAT
4994 implementation unit, defined as any unit from the @code{Ada},
4995 @code{Interfaces}, @code{GNAT},
4996 ^^@code{DEC},^ or @code{System}
4997 hierarchies that is not
4998 documented in either the Ada Reference Manual or the GNAT
4999 Programmer's Reference Manual. Such units are intended only
5000 for internal implementation purposes and should not be @code{with}'ed
5001 by user programs. The default is that such warnings are generated
5002 This warning can also be turned on using @option{-gnatwa}.
5005 @emph{Disable warnings on implementation units.}
5006 @cindex @option{-gnatwI} (@command{gcc})
5007 This switch disables warnings for a @code{with} of an internal GNAT
5008 implementation unit.
5011 @emph{Activate warnings on obsolescent features (Annex J).}
5012 @cindex @option{-gnatwj} (@command{gcc})
5013 @cindex Features, obsolescent
5014 @cindex Obsolescent features
5015 If this warning option is activated, then warnings are generated for
5016 calls to subprograms marked with @code{pragma Obsolescent} and
5017 for use of features in Annex J of the Ada Reference Manual. In the
5018 case of Annex J, not all features are flagged. In particular use
5019 of the renamed packages (like @code{Text_IO}) and use of package
5020 @code{ASCII} are not flagged, since these are very common and
5021 would generate many annoying positive warnings. The default is that
5022 such warnings are not generated. This warning is also turned on by
5023 the use of @option{-gnatwa}.
5025 In addition to the above cases, warnings are also generated for
5026 GNAT features that have been provided in past versions but which
5027 have been superseded (typically by features in the new Ada standard).
5028 For example, @code{pragma Ravenscar} will be flagged since its
5029 function is replaced by @code{pragma Profile(Ravenscar)}.
5031 Note that this warning option functions differently from the
5032 restriction @code{No_Obsolescent_Features} in two respects.
5033 First, the restriction applies only to annex J features.
5034 Second, the restriction does flag uses of package @code{ASCII}.
5037 @emph{Suppress warnings on obsolescent features (Annex J).}
5038 @cindex @option{-gnatwJ} (@command{gcc})
5039 This switch disables warnings on use of obsolescent features.
5042 @emph{Activate warnings on variables that could be constants.}
5043 @cindex @option{-gnatwk} (@command{gcc})
5044 This switch activates warnings for variables that are initialized but
5045 never modified, and then could be declared constants. The default is that
5046 such warnings are not given.
5047 This warning can also be turned on using @option{-gnatwa}.
5050 @emph{Suppress warnings on variables that could be constants.}
5051 @cindex @option{-gnatwK} (@command{gcc})
5052 This switch disables warnings on variables that could be declared constants.
5055 @emph{Activate warnings for elaboration pragmas.}
5056 @cindex @option{-gnatwl} (@command{gcc})
5057 @cindex Elaboration, warnings
5058 This switch activates warnings on missing
5059 @code{Elaborate_All} and @code{Elaborate} pragmas.
5060 See the section in this guide on elaboration checking for details on
5061 when such pragmas should be used. In dynamic elaboration mode, this switch
5062 generations warnings about the need to add elaboration pragmas. Note however,
5063 that if you blindly follow these warnings, and add @code{Elaborate_All}
5064 warnings wherever they are recommended, you basically end up with the
5065 equivalent of the static elaboration model, which may not be what you want for
5066 legacy code for which the static model does not work.
5068 For the static model, the messages generated are labeled "info:" (for
5069 information messages). They are not warnings to add elaboration pragmas,
5070 merely informational messages showing what implicit elaboration pragmas
5071 have been added, for use in analyzing elaboration circularity problems.
5073 Warnings are also generated if you
5074 are using the static mode of elaboration, and a @code{pragma Elaborate}
5075 is encountered. The default is that such warnings
5077 This warning is not automatically turned on by the use of @option{-gnatwa}.
5080 @emph{Suppress warnings for elaboration pragmas.}
5081 @cindex @option{-gnatwL} (@command{gcc})
5082 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5083 See the section in this guide on elaboration checking for details on
5084 when such pragmas should be used.
5087 @emph{Activate warnings on modified but unreferenced variables.}
5088 @cindex @option{-gnatwm} (@command{gcc})
5089 This switch activates warnings for variables that are assigned (using
5090 an initialization value or with one or more assignment statements) but
5091 whose value is never read. The warning is suppressed for volatile
5092 variables and also for variables that are renamings of other variables
5093 or for which an address clause is given.
5094 This warning can also be turned on using @option{-gnatwa}.
5095 The default is that these warnings are not given.
5098 @emph{Disable warnings on modified but unreferenced variables.}
5099 @cindex @option{-gnatwM} (@command{gcc})
5100 This switch disables warnings for variables that are assigned or
5101 initialized, but never read.
5104 @emph{Set normal warnings mode.}
5105 @cindex @option{-gnatwn} (@command{gcc})
5106 This switch sets normal warning mode, in which enabled warnings are
5107 issued and treated as warnings rather than errors. This is the default
5108 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5109 an explicit @option{-gnatws} or
5110 @option{-gnatwe}. It also cancels the effect of the
5111 implicit @option{-gnatwe} that is activated by the
5112 use of @option{-gnatg}.
5115 @emph{Activate warnings on address clause overlays.}
5116 @cindex @option{-gnatwo} (@command{gcc})
5117 @cindex Address Clauses, warnings
5118 This switch activates warnings for possibly unintended initialization
5119 effects of defining address clauses that cause one variable to overlap
5120 another. The default is that such warnings are generated.
5121 This warning can also be turned on using @option{-gnatwa}.
5124 @emph{Suppress warnings on address clause overlays.}
5125 @cindex @option{-gnatwO} (@command{gcc})
5126 This switch suppresses warnings on possibly unintended initialization
5127 effects of defining address clauses that cause one variable to overlap
5131 @emph{Activate warnings on modified but unreferenced out parameters.}
5132 @cindex @option{-gnatw.o} (@command{gcc})
5133 This switch activates warnings for variables that are modified by using
5134 them as actuals for a call to a procedure with an out mode formal, where
5135 the resulting assigned value is never read. It is applicable in the case
5136 where there is more than one out mode formal. If there is only one out
5137 mode formal, the warning is issued by default (controlled by -gnatwu).
5138 The warning is suppressed for volatile
5139 variables and also for variables that are renamings of other variables
5140 or for which an address clause is given.
5141 The default is that these warnings are not given. Note that this warning
5142 is not included in -gnatwa, it must be activated explicitly.
5145 @emph{Disable warnings on modified but unreferenced out parameters.}
5146 @cindex @option{-gnatw.O} (@command{gcc})
5147 This switch suppresses warnings for variables that are modified by using
5148 them as actuals for a call to a procedure with an out mode formal, where
5149 the resulting assigned value is never read.
5152 @emph{Activate warnings on ineffective pragma Inlines.}
5153 @cindex @option{-gnatwp} (@command{gcc})
5154 @cindex Inlining, warnings
5155 This switch activates warnings for failure of front end inlining
5156 (activated by @option{-gnatN}) to inline a particular call. There are
5157 many reasons for not being able to inline a call, including most
5158 commonly that the call is too complex to inline. The default is
5159 that such warnings are not given.
5160 This warning can also be turned on using @option{-gnatwa}.
5161 Warnings on ineffective inlining by the gcc back-end can be activated
5162 separately, using the gcc switch -Winline.
5165 @emph{Suppress warnings on ineffective pragma Inlines.}
5166 @cindex @option{-gnatwP} (@command{gcc})
5167 This switch suppresses warnings on ineffective pragma Inlines. If the
5168 inlining mechanism cannot inline a call, it will simply ignore the
5172 @emph{Activate warnings on parameter ordering.}
5173 @cindex @option{-gnatw.p} (@command{gcc})
5174 @cindex Parameter order, warnings
5175 This switch activates warnings for cases of suspicious parameter
5176 ordering when the list of arguments are all simple identifiers that
5177 match the names of the formals, but are in a different order. The
5178 warning is suppressed if any use of named parameter notation is used,
5179 so this is the appropriate way to suppress a false positive (and
5180 serves to emphasize that the "misordering" is deliberate). The
5182 that such warnings are not given.
5183 This warning can also be turned on using @option{-gnatwa}.
5186 @emph{Suppress warnings on parameter ordering.}
5187 @cindex @option{-gnatw.P} (@command{gcc})
5188 This switch suppresses warnings on cases of suspicious parameter
5192 @emph{Activate warnings on questionable missing parentheses.}
5193 @cindex @option{-gnatwq} (@command{gcc})
5194 @cindex Parentheses, warnings
5195 This switch activates warnings for cases where parentheses are not used and
5196 the result is potential ambiguity from a readers point of view. For example
5197 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5198 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5199 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5200 follow the rule of always parenthesizing to make the association clear, and
5201 this warning switch warns if such parentheses are not present. The default
5202 is that these warnings are given.
5203 This warning can also be turned on using @option{-gnatwa}.
5206 @emph{Suppress warnings on questionable missing parentheses.}
5207 @cindex @option{-gnatwQ} (@command{gcc})
5208 This switch suppresses warnings for cases where the association is not
5209 clear and the use of parentheses is preferred.
5212 @emph{Activate warnings on redundant constructs.}
5213 @cindex @option{-gnatwr} (@command{gcc})
5214 This switch activates warnings for redundant constructs. The following
5215 is the current list of constructs regarded as redundant:
5219 Assignment of an item to itself.
5221 Type conversion that converts an expression to its own type.
5223 Use of the attribute @code{Base} where @code{typ'Base} is the same
5226 Use of pragma @code{Pack} when all components are placed by a record
5227 representation clause.
5229 Exception handler containing only a reraise statement (raise with no
5230 operand) which has no effect.
5232 Use of the operator abs on an operand that is known at compile time
5235 Comparison of boolean expressions to an explicit True value.
5238 This warning can also be turned on using @option{-gnatwa}.
5239 The default is that warnings for redundant constructs are not given.
5242 @emph{Suppress warnings on redundant constructs.}
5243 @cindex @option{-gnatwR} (@command{gcc})
5244 This switch suppresses warnings for redundant constructs.
5247 @emph{Suppress all warnings.}
5248 @cindex @option{-gnatws} (@command{gcc})
5249 This switch completely suppresses the
5250 output of all warning messages from the GNAT front end.
5251 Note that it does not suppress warnings from the @command{gcc} back end.
5252 To suppress these back end warnings as well, use the switch @option{-w}
5253 in addition to @option{-gnatws}.
5256 @emph{Activate warnings for tracking of deleted conditional code.}
5257 @cindex @option{-gnatwt} (@command{gcc})
5258 @cindex Deactivated code, warnings
5259 @cindex Deleted code, warnings
5260 This switch activates warnings for tracking of code in conditionals (IF and
5261 CASE statements) that is detected to be dead code which cannot be executed, and
5262 which is removed by the front end. This warning is off by default, and is not
5263 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5264 useful for detecting deactivated code in certified applications.
5267 @emph{Suppress warnings for tracking of deleted conditional code.}
5268 @cindex @option{-gnatwT} (@command{gcc})
5269 This switch suppresses warnings for tracking of deleted conditional code.
5272 @emph{Activate warnings on unused entities.}
5273 @cindex @option{-gnatwu} (@command{gcc})
5274 This switch activates warnings to be generated for entities that
5275 are declared but not referenced, and for units that are @code{with}'ed
5277 referenced. In the case of packages, a warning is also generated if
5278 no entities in the package are referenced. This means that if the package
5279 is referenced but the only references are in @code{use}
5280 clauses or @code{renames}
5281 declarations, a warning is still generated. A warning is also generated
5282 for a generic package that is @code{with}'ed but never instantiated.
5283 In the case where a package or subprogram body is compiled, and there
5284 is a @code{with} on the corresponding spec
5285 that is only referenced in the body,
5286 a warning is also generated, noting that the
5287 @code{with} can be moved to the body. The default is that
5288 such warnings are not generated.
5289 This switch also activates warnings on unreferenced formals
5290 (it includes the effect of @option{-gnatwf}).
5291 This warning can also be turned on using @option{-gnatwa}.
5294 @emph{Suppress warnings on unused entities.}
5295 @cindex @option{-gnatwU} (@command{gcc})
5296 This switch suppresses warnings for unused entities and packages.
5297 It also turns off warnings on unreferenced formals (and thus includes
5298 the effect of @option{-gnatwF}).
5301 @emph{Activate warnings on unassigned variables.}
5302 @cindex @option{-gnatwv} (@command{gcc})
5303 @cindex Unassigned variable warnings
5304 This switch activates warnings for access to variables which
5305 may not be properly initialized. The default is that
5306 such warnings are generated.
5307 This warning can also be turned on using @option{-gnatwa}.
5310 @emph{Suppress warnings on unassigned variables.}
5311 @cindex @option{-gnatwV} (@command{gcc})
5312 This switch suppresses warnings for access to variables which
5313 may not be properly initialized.
5314 For variables of a composite type, the warning can also be suppressed in
5315 Ada 2005 by using a default initialization with a box. For example, if
5316 Table is an array of records whose components are only partially uninitialized,
5317 then the following code:
5319 @smallexample @c ada
5320 Tab : Table := (others => <>);
5323 will suppress warnings on subsequent statements that access components
5327 @emph{Activate warnings on wrong low bound assumption.}
5328 @cindex @option{-gnatww} (@command{gcc})
5329 @cindex String indexing warnings
5330 This switch activates warnings for indexing an unconstrained string parameter
5331 with a literal or S'Length. This is a case where the code is assuming that the
5332 low bound is one, which is in general not true (for example when a slice is
5333 passed). The default is that such warnings are generated.
5334 This warning can also be turned on using @option{-gnatwa}.
5337 @emph{Suppress warnings on wrong low bound assumption.}
5338 @cindex @option{-gnatwW} (@command{gcc})
5339 This switch suppresses warnings for indexing an unconstrained string parameter
5340 with a literal or S'Length. Note that this warning can also be suppressed
5341 in a particular case by adding an
5342 assertion that the lower bound is 1,
5343 as shown in the following example.
5345 @smallexample @c ada
5346 procedure K (S : String) is
5347 pragma Assert (S'First = 1);
5352 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5353 @cindex @option{-gnatw.w} (@command{gcc})
5354 @cindex Warnings Off control
5355 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5356 where either the pragma is entirely useless (because it suppresses no
5357 warnings), or it could be replaced by @code{pragma Unreferenced} or
5358 @code{pragma Unmodified}.The default is that these warnings are not given.
5359 Note that this warning is not included in -gnatwa, it must be
5360 activated explicitly.
5363 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5364 @cindex @option{-gnatw.W} (@command{gcc})
5365 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5368 @emph{Activate warnings on Export/Import pragmas.}
5369 @cindex @option{-gnatwx} (@command{gcc})
5370 @cindex Export/Import pragma warnings
5371 This switch activates warnings on Export/Import pragmas when
5372 the compiler detects a possible conflict between the Ada and
5373 foreign language calling sequences. For example, the use of
5374 default parameters in a convention C procedure is dubious
5375 because the C compiler cannot supply the proper default, so
5376 a warning is issued. The default is that such warnings are
5378 This warning can also be turned on using @option{-gnatwa}.
5381 @emph{Suppress warnings on Export/Import pragmas.}
5382 @cindex @option{-gnatwX} (@command{gcc})
5383 This switch suppresses warnings on Export/Import pragmas.
5384 The sense of this is that you are telling the compiler that
5385 you know what you are doing in writing the pragma, and it
5386 should not complain at you.
5389 @emph{Activate warnings for No_Exception_Propagation mode.}
5390 @cindex @option{-gnatwm} (@command{gcc})
5391 This switch activates warnings for exception usage when pragma Restrictions
5392 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5393 explicit exception raises which are not covered by a local handler, and for
5394 exception handlers which do not cover a local raise. The default is that these
5395 warnings are not given.
5398 @emph{Disable warnings for No_Exception_Propagation mode.}
5399 This switch disables warnings for exception usage when pragma Restrictions
5400 (No_Exception_Propagation) is in effect.
5403 @emph{Activate warnings for Ada 2005 compatibility issues.}
5404 @cindex @option{-gnatwy} (@command{gcc})
5405 @cindex Ada 2005 compatibility issues warnings
5406 For the most part Ada 2005 is upwards compatible with Ada 95,
5407 but there are some exceptions (for example the fact that
5408 @code{interface} is now a reserved word in Ada 2005). This
5409 switch activates several warnings to help in identifying
5410 and correcting such incompatibilities. The default is that
5411 these warnings are generated. Note that at one point Ada 2005
5412 was called Ada 0Y, hence the choice of character.
5413 This warning can also be turned on using @option{-gnatwa}.
5416 @emph{Disable warnings for Ada 2005 compatibility issues.}
5417 @cindex @option{-gnatwY} (@command{gcc})
5418 @cindex Ada 2005 compatibility issues warnings
5419 This switch suppresses several warnings intended to help in identifying
5420 incompatibilities between Ada 95 and Ada 2005.
5423 @emph{Activate warnings on unchecked conversions.}
5424 @cindex @option{-gnatwz} (@command{gcc})
5425 @cindex Unchecked_Conversion warnings
5426 This switch activates warnings for unchecked conversions
5427 where the types are known at compile time to have different
5429 is that such warnings are generated. Warnings are also
5430 generated for subprogram pointers with different conventions,
5431 and, on VMS only, for data pointers with different conventions.
5432 This warning can also be turned on using @option{-gnatwa}.
5435 @emph{Suppress warnings on unchecked conversions.}
5436 @cindex @option{-gnatwZ} (@command{gcc})
5437 This switch suppresses warnings for unchecked conversions
5438 where the types are known at compile time to have different
5439 sizes or conventions.
5441 @item ^-Wunused^WARNINGS=UNUSED^
5442 @cindex @option{-Wunused}
5443 The warnings controlled by the @option{-gnatw} switch are generated by
5444 the front end of the compiler. The @option{GCC} back end can provide
5445 additional warnings and they are controlled by the @option{-W} switch.
5446 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5447 warnings for entities that are declared but not referenced.
5449 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5450 @cindex @option{-Wuninitialized}
5451 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5452 the back end warning for uninitialized variables. This switch must be
5453 used in conjunction with an optimization level greater than zero.
5455 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5456 @cindex @option{-Wall}
5457 This switch enables all the above warnings from the @option{GCC} back end.
5458 The code generator detects a number of warning situations that are missed
5459 by the @option{GNAT} front end, and this switch can be used to activate them.
5460 The use of this switch also sets the default front end warning mode to
5461 @option{-gnatwa}, that is, most front end warnings activated as well.
5463 @item ^-w^/NO_BACK_END_WARNINGS^
5465 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5466 The use of this switch also sets the default front end warning mode to
5467 @option{-gnatws}, that is, front end warnings suppressed as well.
5473 A string of warning parameters can be used in the same parameter. For example:
5480 will turn on all optional warnings except for elaboration pragma warnings,
5481 and also specify that warnings should be treated as errors.
5483 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5508 @node Debugging and Assertion Control
5509 @subsection Debugging and Assertion Control
5513 @cindex @option{-gnata} (@command{gcc})
5519 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5520 are ignored. This switch, where @samp{a} stands for assert, causes
5521 @code{Assert} and @code{Debug} pragmas to be activated.
5523 The pragmas have the form:
5527 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5528 @var{static-string-expression}@r{]})
5529 @b{pragma} Debug (@var{procedure call})
5534 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5535 If the result is @code{True}, the pragma has no effect (other than
5536 possible side effects from evaluating the expression). If the result is
5537 @code{False}, the exception @code{Assert_Failure} declared in the package
5538 @code{System.Assertions} is
5539 raised (passing @var{static-string-expression}, if present, as the
5540 message associated with the exception). If no string expression is
5541 given the default is a string giving the file name and line number
5544 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5545 @code{pragma Debug} may appear within a declaration sequence, allowing
5546 debugging procedures to be called between declarations.
5549 @item /DEBUG@r{[}=debug-level@r{]}
5551 Specifies how much debugging information is to be included in
5552 the resulting object file where 'debug-level' is one of the following:
5555 Include both debugger symbol records and traceback
5557 This is the default setting.
5559 Include both debugger symbol records and traceback in
5562 Excludes both debugger symbol records and traceback
5563 the object file. Same as /NODEBUG.
5565 Includes only debugger symbol records in the object
5566 file. Note that this doesn't include traceback information.
5571 @node Validity Checking
5572 @subsection Validity Checking
5573 @findex Validity Checking
5576 The Ada Reference Manual has specific requirements for checking
5577 for invalid values. In particular, RM 13.9.1 requires that the
5578 evaluation of invalid values (for example from unchecked conversions),
5579 not result in erroneous execution. In GNAT, the result of such an
5580 evaluation in normal default mode is to either use the value
5581 unmodified, or to raise Constraint_Error in those cases where use
5582 of the unmodified value would cause erroneous execution. The cases
5583 where unmodified values might lead to erroneous execution are case
5584 statements (where a wild jump might result from an invalid value),
5585 and subscripts on the left hand side (where memory corruption could
5586 occur as a result of an invalid value).
5588 The @option{-gnatB} switch tells the compiler to assume that all
5589 values are valid (that is, within their declared subtype range)
5590 except in the context of a use of the Valid attribute. This means
5591 the compiler can generate more efficient code, since the range
5592 of values is better known at compile time.
5594 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5597 The @code{x} argument is a string of letters that
5598 indicate validity checks that are performed or not performed in addition
5599 to the default checks described above.
5602 The options allowed for this qualifier
5603 indicate validity checks that are performed or not performed in addition
5604 to the default checks described above.
5610 @emph{All validity checks.}
5611 @cindex @option{-gnatVa} (@command{gcc})
5612 All validity checks are turned on.
5614 That is, @option{-gnatVa} is
5615 equivalent to @option{gnatVcdfimorst}.
5619 @emph{Validity checks for copies.}
5620 @cindex @option{-gnatVc} (@command{gcc})
5621 The right hand side of assignments, and the initializing values of
5622 object declarations are validity checked.
5625 @emph{Default (RM) validity checks.}
5626 @cindex @option{-gnatVd} (@command{gcc})
5627 Some validity checks are done by default following normal Ada semantics
5629 A check is done in case statements that the expression is within the range
5630 of the subtype. If it is not, Constraint_Error is raised.
5631 For assignments to array components, a check is done that the expression used
5632 as index is within the range. If it is not, Constraint_Error is raised.
5633 Both these validity checks may be turned off using switch @option{-gnatVD}.
5634 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5635 switch @option{-gnatVd} will leave the checks turned on.
5636 Switch @option{-gnatVD} should be used only if you are sure that all such
5637 expressions have valid values. If you use this switch and invalid values
5638 are present, then the program is erroneous, and wild jumps or memory
5639 overwriting may occur.
5642 @emph{Validity checks for elementary components.}
5643 @cindex @option{-gnatVe} (@command{gcc})
5644 In the absence of this switch, assignments to record or array components are
5645 not validity checked, even if validity checks for assignments generally
5646 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5647 require valid data, but assignment of individual components does. So for
5648 example, there is a difference between copying the elements of an array with a
5649 slice assignment, compared to assigning element by element in a loop. This
5650 switch allows you to turn off validity checking for components, even when they
5651 are assigned component by component.
5654 @emph{Validity checks for floating-point values.}
5655 @cindex @option{-gnatVf} (@command{gcc})
5656 In the absence of this switch, validity checking occurs only for discrete
5657 values. If @option{-gnatVf} is specified, then validity checking also applies
5658 for floating-point values, and NaNs and infinities are considered invalid,
5659 as well as out of range values for constrained types. Note that this means
5660 that standard IEEE infinity mode is not allowed. The exact contexts
5661 in which floating-point values are checked depends on the setting of other
5662 options. For example,
5663 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5664 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5665 (the order does not matter) specifies that floating-point parameters of mode
5666 @code{in} should be validity checked.
5669 @emph{Validity checks for @code{in} mode parameters}
5670 @cindex @option{-gnatVi} (@command{gcc})
5671 Arguments for parameters of mode @code{in} are validity checked in function
5672 and procedure calls at the point of call.
5675 @emph{Validity checks for @code{in out} mode parameters.}
5676 @cindex @option{-gnatVm} (@command{gcc})
5677 Arguments for parameters of mode @code{in out} are validity checked in
5678 procedure calls at the point of call. The @code{'m'} here stands for
5679 modify, since this concerns parameters that can be modified by the call.
5680 Note that there is no specific option to test @code{out} parameters,
5681 but any reference within the subprogram will be tested in the usual
5682 manner, and if an invalid value is copied back, any reference to it
5683 will be subject to validity checking.
5686 @emph{No validity checks.}
5687 @cindex @option{-gnatVn} (@command{gcc})
5688 This switch turns off all validity checking, including the default checking
5689 for case statements and left hand side subscripts. Note that the use of
5690 the switch @option{-gnatp} suppresses all run-time checks, including
5691 validity checks, and thus implies @option{-gnatVn}. When this switch
5692 is used, it cancels any other @option{-gnatV} previously issued.
5695 @emph{Validity checks for operator and attribute operands.}
5696 @cindex @option{-gnatVo} (@command{gcc})
5697 Arguments for predefined operators and attributes are validity checked.
5698 This includes all operators in package @code{Standard},
5699 the shift operators defined as intrinsic in package @code{Interfaces}
5700 and operands for attributes such as @code{Pos}. Checks are also made
5701 on individual component values for composite comparisons, and on the
5702 expressions in type conversions and qualified expressions. Checks are
5703 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5706 @emph{Validity checks for parameters.}
5707 @cindex @option{-gnatVp} (@command{gcc})
5708 This controls the treatment of parameters within a subprogram (as opposed
5709 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5710 of parameters on a call. If either of these call options is used, then
5711 normally an assumption is made within a subprogram that the input arguments
5712 have been validity checking at the point of call, and do not need checking
5713 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5714 is not made, and parameters are not assumed to be valid, so their validity
5715 will be checked (or rechecked) within the subprogram.
5718 @emph{Validity checks for function returns.}
5719 @cindex @option{-gnatVr} (@command{gcc})
5720 The expression in @code{return} statements in functions is validity
5724 @emph{Validity checks for subscripts.}
5725 @cindex @option{-gnatVs} (@command{gcc})
5726 All subscripts expressions are checked for validity, whether they appear
5727 on the right side or left side (in default mode only left side subscripts
5728 are validity checked).
5731 @emph{Validity checks for tests.}
5732 @cindex @option{-gnatVt} (@command{gcc})
5733 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5734 statements are checked, as well as guard expressions in entry calls.
5739 The @option{-gnatV} switch may be followed by
5740 ^a string of letters^a list of options^
5741 to turn on a series of validity checking options.
5743 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5744 specifies that in addition to the default validity checking, copies and
5745 function return expressions are to be validity checked.
5746 In order to make it easier
5747 to specify the desired combination of effects,
5749 the upper case letters @code{CDFIMORST} may
5750 be used to turn off the corresponding lower case option.
5753 the prefix @code{NO} on an option turns off the corresponding validity
5756 @item @code{NOCOPIES}
5757 @item @code{NODEFAULT}
5758 @item @code{NOFLOATS}
5759 @item @code{NOIN_PARAMS}
5760 @item @code{NOMOD_PARAMS}
5761 @item @code{NOOPERANDS}
5762 @item @code{NORETURNS}
5763 @item @code{NOSUBSCRIPTS}
5764 @item @code{NOTESTS}
5768 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5769 turns on all validity checking options except for
5770 checking of @code{@b{in out}} procedure arguments.
5772 The specification of additional validity checking generates extra code (and
5773 in the case of @option{-gnatVa} the code expansion can be substantial).
5774 However, these additional checks can be very useful in detecting
5775 uninitialized variables, incorrect use of unchecked conversion, and other
5776 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5777 is useful in conjunction with the extra validity checking, since this
5778 ensures that wherever possible uninitialized variables have invalid values.
5780 See also the pragma @code{Validity_Checks} which allows modification of
5781 the validity checking mode at the program source level, and also allows for
5782 temporary disabling of validity checks.
5784 @node Style Checking
5785 @subsection Style Checking
5786 @findex Style checking
5789 The @option{-gnaty^x^(option,option,@dots{})^} switch
5790 @cindex @option{-gnaty} (@command{gcc})
5791 causes the compiler to
5792 enforce specified style rules. A limited set of style rules has been used
5793 in writing the GNAT sources themselves. This switch allows user programs
5794 to activate all or some of these checks. If the source program fails a
5795 specified style check, an appropriate warning message is given, preceded by
5796 the character sequence ``(style)''.
5798 @code{(option,option,@dots{})} is a sequence of keywords
5801 The string @var{x} is a sequence of letters or digits
5803 indicating the particular style
5804 checks to be performed. The following checks are defined:
5809 @emph{Specify indentation level.}
5810 If a digit from 1-9 appears
5811 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5812 then proper indentation is checked, with the digit indicating the
5813 indentation level required. A value of zero turns off this style check.
5814 The general style of required indentation is as specified by
5815 the examples in the Ada Reference Manual. Full line comments must be
5816 aligned with the @code{--} starting on a column that is a multiple of
5817 the alignment level, or they may be aligned the same way as the following
5818 non-blank line (this is useful when full line comments appear in the middle
5822 @emph{Check attribute casing.}
5823 Attribute names, including the case of keywords such as @code{digits}
5824 used as attributes names, must be written in mixed case, that is, the
5825 initial letter and any letter following an underscore must be uppercase.
5826 All other letters must be lowercase.
5828 @item ^A^ARRAY_INDEXES^
5829 @emph{Use of array index numbers in array attributes.}
5830 When using the array attributes First, Last, Range,
5831 or Length, the index number must be omitted for one-dimensional arrays
5832 and is required for multi-dimensional arrays.
5835 @emph{Blanks not allowed at statement end.}
5836 Trailing blanks are not allowed at the end of statements. The purpose of this
5837 rule, together with h (no horizontal tabs), is to enforce a canonical format
5838 for the use of blanks to separate source tokens.
5841 @emph{Check comments.}
5842 Comments must meet the following set of rules:
5847 The ``@code{--}'' that starts the column must either start in column one,
5848 or else at least one blank must precede this sequence.
5851 Comments that follow other tokens on a line must have at least one blank
5852 following the ``@code{--}'' at the start of the comment.
5855 Full line comments must have two blanks following the ``@code{--}'' that
5856 starts the comment, with the following exceptions.
5859 A line consisting only of the ``@code{--}'' characters, possibly preceded
5860 by blanks is permitted.
5863 A comment starting with ``@code{--x}'' where @code{x} is a special character
5865 This allows proper processing of the output generated by specialized tools
5866 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5868 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5869 special character is defined as being in one of the ASCII ranges
5870 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
5871 Note that this usage is not permitted
5872 in GNAT implementation units (i.e., when @option{-gnatg} is used).
5875 A line consisting entirely of minus signs, possibly preceded by blanks, is
5876 permitted. This allows the construction of box comments where lines of minus
5877 signs are used to form the top and bottom of the box.
5880 A comment that starts and ends with ``@code{--}'' is permitted as long as at
5881 least one blank follows the initial ``@code{--}''. Together with the preceding
5882 rule, this allows the construction of box comments, as shown in the following
5885 ---------------------------
5886 -- This is a box comment --
5887 -- with two text lines. --
5888 ---------------------------
5892 @item ^d^DOS_LINE_ENDINGS^
5893 @emph{Check no DOS line terminators present.}
5894 All lines must be terminated by a single ASCII.LF
5895 character (in particular the DOS line terminator sequence CR/LF is not
5899 @emph{Check end/exit labels.}
5900 Optional labels on @code{end} statements ending subprograms and on
5901 @code{exit} statements exiting named loops, are required to be present.
5904 @emph{No form feeds or vertical tabs.}
5905 Neither form feeds nor vertical tab characters are permitted
5909 @emph{GNAT style mode}
5910 The set of style check switches is set to match that used by the GNAT sources.
5911 This may be useful when developing code that is eventually intended to be
5912 incorporated into GNAT. For further details, see GNAT sources.
5915 @emph{No horizontal tabs.}
5916 Horizontal tab characters are not permitted in the source text.
5917 Together with the b (no blanks at end of line) check, this
5918 enforces a canonical form for the use of blanks to separate
5922 @emph{Check if-then layout.}
5923 The keyword @code{then} must appear either on the same
5924 line as corresponding @code{if}, or on a line on its own, lined
5925 up under the @code{if} with at least one non-blank line in between
5926 containing all or part of the condition to be tested.
5929 @emph{check mode IN keywords}
5930 Mode @code{in} (the default mode) is not
5931 allowed to be given explicitly. @code{in out} is fine,
5932 but not @code{in} on its own.
5935 @emph{Check keyword casing.}
5936 All keywords must be in lower case (with the exception of keywords
5937 such as @code{digits} used as attribute names to which this check
5941 @emph{Check layout.}
5942 Layout of statement and declaration constructs must follow the
5943 recommendations in the Ada Reference Manual, as indicated by the
5944 form of the syntax rules. For example an @code{else} keyword must
5945 be lined up with the corresponding @code{if} keyword.
5947 There are two respects in which the style rule enforced by this check
5948 option are more liberal than those in the Ada Reference Manual. First
5949 in the case of record declarations, it is permissible to put the
5950 @code{record} keyword on the same line as the @code{type} keyword, and
5951 then the @code{end} in @code{end record} must line up under @code{type}.
5952 This is also permitted when the type declaration is split on two lines.
5953 For example, any of the following three layouts is acceptable:
5955 @smallexample @c ada
5978 Second, in the case of a block statement, a permitted alternative
5979 is to put the block label on the same line as the @code{declare} or
5980 @code{begin} keyword, and then line the @code{end} keyword up under
5981 the block label. For example both the following are permitted:
5983 @smallexample @c ada
6001 The same alternative format is allowed for loops. For example, both of
6002 the following are permitted:
6004 @smallexample @c ada
6006 Clear : while J < 10 loop
6017 @item ^Lnnn^MAX_NESTING=nnn^
6018 @emph{Set maximum nesting level}
6019 The maximum level of nesting of constructs (including subprograms, loops,
6020 blocks, packages, and conditionals) may not exceed the given value
6021 @option{nnn}. A value of zero disconnects this style check.
6023 @item ^m^LINE_LENGTH^
6024 @emph{Check maximum line length.}
6025 The length of source lines must not exceed 79 characters, including
6026 any trailing blanks. The value of 79 allows convenient display on an
6027 80 character wide device or window, allowing for possible special
6028 treatment of 80 character lines. Note that this count is of
6029 characters in the source text. This means that a tab character counts
6030 as one character in this count but a wide character sequence counts as
6031 a single character (however many bytes are needed in the encoding).
6033 @item ^Mnnn^MAX_LENGTH=nnn^
6034 @emph{Set maximum line length.}
6035 The length of lines must not exceed the
6036 given value @option{nnn}. The maximum value that can be specified is 32767.
6038 @item ^n^STANDARD_CASING^
6039 @emph{Check casing of entities in Standard.}
6040 Any identifier from Standard must be cased
6041 to match the presentation in the Ada Reference Manual (for example,
6042 @code{Integer} and @code{ASCII.NUL}).
6045 @emph{Turn off all style checks}
6046 All style check options are turned off.
6048 @item ^o^ORDERED_SUBPROGRAMS^
6049 @emph{Check order of subprogram bodies.}
6050 All subprogram bodies in a given scope
6051 (e.g.@: a package body) must be in alphabetical order. The ordering
6052 rule uses normal Ada rules for comparing strings, ignoring casing
6053 of letters, except that if there is a trailing numeric suffix, then
6054 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6057 @item ^O^OVERRIDING_INDICATORS^
6058 @emph{Check that overriding subprograms are explicitly marked as such.}
6059 The declaration of a primitive operation of a type extension that overrides
6060 an inherited operation must carry an overriding indicator.
6063 @emph{Check pragma casing.}
6064 Pragma names must be written in mixed case, that is, the
6065 initial letter and any letter following an underscore must be uppercase.
6066 All other letters must be lowercase.
6068 @item ^r^REFERENCES^
6069 @emph{Check references.}
6070 All identifier references must be cased in the same way as the
6071 corresponding declaration. No specific casing style is imposed on
6072 identifiers. The only requirement is for consistency of references
6075 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6076 @emph{Check no statements after THEN/ELSE.}
6077 No statements are allowed
6078 on the same line as a THEN or ELSE keyword following the
6079 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6080 and a special exception allows a pragma to appear after ELSE.
6083 @emph{Check separate specs.}
6084 Separate declarations (``specs'') are required for subprograms (a
6085 body is not allowed to serve as its own declaration). The only
6086 exception is that parameterless library level procedures are
6087 not required to have a separate declaration. This exception covers
6088 the most frequent form of main program procedures.
6091 @emph{Check token spacing.}
6092 The following token spacing rules are enforced:
6097 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6100 The token @code{=>} must be surrounded by spaces.
6103 The token @code{<>} must be preceded by a space or a left parenthesis.
6106 Binary operators other than @code{**} must be surrounded by spaces.
6107 There is no restriction on the layout of the @code{**} binary operator.
6110 Colon must be surrounded by spaces.
6113 Colon-equal (assignment, initialization) must be surrounded by spaces.
6116 Comma must be the first non-blank character on the line, or be
6117 immediately preceded by a non-blank character, and must be followed
6121 If the token preceding a left parenthesis ends with a letter or digit, then
6122 a space must separate the two tokens.
6125 A right parenthesis must either be the first non-blank character on
6126 a line, or it must be preceded by a non-blank character.
6129 A semicolon must not be preceded by a space, and must not be followed by
6130 a non-blank character.
6133 A unary plus or minus may not be followed by a space.
6136 A vertical bar must be surrounded by spaces.
6139 @item ^u^UNNECESSARY_BLANK_LINES^
6140 @emph{Check unnecessary blank lines.}
6141 Unnecessary blank lines are not allowed. A blank line is considered
6142 unnecessary if it appears at the end of the file, or if more than
6143 one blank line occurs in sequence.
6145 @item ^x^XTRA_PARENS^
6146 @emph{Check extra parentheses.}
6147 Unnecessary extra level of parentheses (C-style) are not allowed
6148 around conditions in @code{if} statements, @code{while} statements and
6149 @code{exit} statements.
6151 @item ^y^ALL_BUILTIN^
6152 @emph{Set all standard style check options}
6153 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6154 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6155 @option{-gnatyS}, @option{-gnatyLnnn},
6156 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6160 @emph{Remove style check options}
6161 This causes any subsequent options in the string to act as canceling the
6162 corresponding style check option. To cancel maximum nesting level control,
6163 use @option{L} parameter witout any integer value after that, because any
6164 digit following @option{-} in the parameter string of the @option{-gnaty}
6165 option will be threated as canceling indentation check. The same is true
6166 for @option{M} parameter. @option{y} and @option{N} parameters are not
6167 allowed after @option{-}.
6170 This causes any subsequent options in the string to enable the corresponding
6171 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6177 @emph{Removing style check options}
6178 If the name of a style check is preceded by @option{NO} then the corresponding
6179 style check is turned off. For example @option{NOCOMMENTS} turns off style
6180 checking for comments.
6185 In the above rules, appearing in column one is always permitted, that is,
6186 counts as meeting either a requirement for a required preceding space,
6187 or as meeting a requirement for no preceding space.
6189 Appearing at the end of a line is also always permitted, that is, counts
6190 as meeting either a requirement for a following space, or as meeting
6191 a requirement for no following space.
6194 If any of these style rules is violated, a message is generated giving
6195 details on the violation. The initial characters of such messages are
6196 always ``@code{(style)}''. Note that these messages are treated as warning
6197 messages, so they normally do not prevent the generation of an object
6198 file. The @option{-gnatwe} switch can be used to treat warning messages,
6199 including style messages, as fatal errors.
6203 @option{-gnaty} on its own (that is not
6204 followed by any letters or digits), then the effect is equivalent
6205 to the use of @option{-gnatyy}, as described above, that is all
6206 built-in standard style check options are enabled.
6210 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6211 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6212 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6224 clears any previously set style checks.
6226 @node Run-Time Checks
6227 @subsection Run-Time Checks
6228 @cindex Division by zero
6229 @cindex Access before elaboration
6230 @cindex Checks, division by zero
6231 @cindex Checks, access before elaboration
6232 @cindex Checks, stack overflow checking
6235 By default, the following checks are suppressed: integer overflow
6236 checks, stack overflow checks, and checks for access before
6237 elaboration on subprogram calls. All other checks, including range
6238 checks and array bounds checks, are turned on by default. The
6239 following @command{gcc} switches refine this default behavior.
6244 @cindex @option{-gnatp} (@command{gcc})
6245 @cindex Suppressing checks
6246 @cindex Checks, suppressing
6248 Suppress all run-time checks as though @code{pragma Suppress (All_checks)}
6249 had been present in the source. Validity checks are also suppressed (in
6250 other words @option{-gnatp} also implies @option{-gnatVn}.
6251 Use this switch to improve the performance
6252 of the code at the expense of safety in the presence of invalid data or
6255 Note that when checks are suppressed, the compiler is allowed, but not
6256 required, to omit the checking code. If the run-time cost of the
6257 checking code is zero or near-zero, the compiler will generate it even
6258 if checks are suppressed. In particular, if the compiler can prove
6259 that a certain check will necessarily fail, it will generate code to
6260 do an unconditional ``raise'', even if checks are suppressed. The
6261 compiler warns in this case.
6263 Of course, run-time checks are omitted whenever the compiler can prove
6264 that they will not fail, whether or not checks are suppressed.
6266 Note that if you suppress a check that would have failed, program
6267 execution is erroneous, which means the behavior is totally
6268 unpredictable. The program might crash, or print wrong answers, or
6269 do anything else. It might even do exactly what you wanted it to do
6270 (and then it might start failing mysteriously next week or next
6271 year). The compiler will generate code based on the assumption that
6272 the condition being checked is true, which can result in disaster if
6273 that assumption is wrong.
6276 @cindex @option{-gnato} (@command{gcc})
6277 @cindex Overflow checks
6278 @cindex Check, overflow
6279 Enables overflow checking for integer operations.
6280 This causes GNAT to generate slower and larger executable
6281 programs by adding code to check for overflow (resulting in raising
6282 @code{Constraint_Error} as required by standard Ada
6283 semantics). These overflow checks correspond to situations in which
6284 the true value of the result of an operation may be outside the base
6285 range of the result type. The following example shows the distinction:
6287 @smallexample @c ada
6288 X1 : Integer := "Integer'Last";
6289 X2 : Integer range 1 .. 5 := "5";
6290 X3 : Integer := "Integer'Last";
6291 X4 : Integer range 1 .. 5 := "5";
6292 F : Float := "2.0E+20";
6301 Note that if explicit values are assigned at compile time, the
6302 compiler may be able to detect overflow at compile time, in which case
6303 no actual run-time checking code is required, and Constraint_Error
6304 will be raised unconditionally, with or without
6305 @option{-gnato}. That's why the assigned values in the above fragment
6306 are in quotes, the meaning is "assign a value not known to the
6307 compiler that happens to be equal to ...". The remaining discussion
6308 assumes that the compiler cannot detect the values at compile time.
6310 Here the first addition results in a value that is outside the base range
6311 of Integer, and hence requires an overflow check for detection of the
6312 constraint error. Thus the first assignment to @code{X1} raises a
6313 @code{Constraint_Error} exception only if @option{-gnato} is set.
6315 The second increment operation results in a violation of the explicit
6316 range constraint; such range checks are performed by default, and are
6317 unaffected by @option{-gnato}.
6319 The two conversions of @code{F} both result in values that are outside
6320 the base range of type @code{Integer} and thus will raise
6321 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6322 The fact that the result of the second conversion is assigned to
6323 variable @code{X4} with a restricted range is irrelevant, since the problem
6324 is in the conversion, not the assignment.
6326 Basically the rule is that in the default mode (@option{-gnato} not
6327 used), the generated code assures that all integer variables stay
6328 within their declared ranges, or within the base range if there is
6329 no declared range. This prevents any serious problems like indexes
6330 out of range for array operations.
6332 What is not checked in default mode is an overflow that results in
6333 an in-range, but incorrect value. In the above example, the assignments
6334 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6335 range of the target variable, but the result is wrong in the sense that
6336 it is too large to be represented correctly. Typically the assignment
6337 to @code{X1} will result in wrap around to the largest negative number.
6338 The conversions of @code{F} will result in some @code{Integer} value
6339 and if that integer value is out of the @code{X4} range then the
6340 subsequent assignment would generate an exception.
6342 @findex Machine_Overflows
6343 Note that the @option{-gnato} switch does not affect the code generated
6344 for any floating-point operations; it applies only to integer
6346 For floating-point, GNAT has the @code{Machine_Overflows}
6347 attribute set to @code{False} and the normal mode of operation is to
6348 generate IEEE NaN and infinite values on overflow or invalid operations
6349 (such as dividing 0.0 by 0.0).
6351 The reason that we distinguish overflow checking from other kinds of
6352 range constraint checking is that a failure of an overflow check, unlike
6353 for example the failure of a range check, can result in an incorrect
6354 value, but cannot cause random memory destruction (like an out of range
6355 subscript), or a wild jump (from an out of range case value). Overflow
6356 checking is also quite expensive in time and space, since in general it
6357 requires the use of double length arithmetic.
6359 Note again that @option{-gnato} is off by default, so overflow checking is
6360 not performed in default mode. This means that out of the box, with the
6361 default settings, GNAT does not do all the checks expected from the
6362 language description in the Ada Reference Manual. If you want all constraint
6363 checks to be performed, as described in this Manual, then you must
6364 explicitly use the -gnato switch either on the @command{gnatmake} or
6365 @command{gcc} command.
6368 @cindex @option{-gnatE} (@command{gcc})
6369 @cindex Elaboration checks
6370 @cindex Check, elaboration
6371 Enables dynamic checks for access-before-elaboration
6372 on subprogram calls and generic instantiations.
6373 Note that @option{-gnatE} is not necessary for safety, because in the
6374 default mode, GNAT ensures statically that the checks would not fail.
6375 For full details of the effect and use of this switch,
6376 @xref{Compiling Using gcc}.
6379 @cindex @option{-fstack-check} (@command{gcc})
6380 @cindex Stack Overflow Checking
6381 @cindex Checks, stack overflow checking
6382 Activates stack overflow checking. For full details of the effect and use of
6383 this switch see @ref{Stack Overflow Checking}.
6388 The setting of these switches only controls the default setting of the
6389 checks. You may modify them using either @code{Suppress} (to remove
6390 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6393 @node Using gcc for Syntax Checking
6394 @subsection Using @command{gcc} for Syntax Checking
6397 @cindex @option{-gnats} (@command{gcc})
6401 The @code{s} stands for ``syntax''.
6404 Run GNAT in syntax checking only mode. For
6405 example, the command
6408 $ gcc -c -gnats x.adb
6412 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6413 series of files in a single command
6415 , and can use wild cards to specify such a group of files.
6416 Note that you must specify the @option{-c} (compile
6417 only) flag in addition to the @option{-gnats} flag.
6420 You may use other switches in conjunction with @option{-gnats}. In
6421 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6422 format of any generated error messages.
6424 When the source file is empty or contains only empty lines and/or comments,
6425 the output is a warning:
6428 $ gcc -c -gnats -x ada toto.txt
6429 toto.txt:1:01: warning: empty file, contains no compilation units
6433 Otherwise, the output is simply the error messages, if any. No object file or
6434 ALI file is generated by a syntax-only compilation. Also, no units other
6435 than the one specified are accessed. For example, if a unit @code{X}
6436 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6437 check only mode does not access the source file containing unit
6440 @cindex Multiple units, syntax checking
6441 Normally, GNAT allows only a single unit in a source file. However, this
6442 restriction does not apply in syntax-check-only mode, and it is possible
6443 to check a file containing multiple compilation units concatenated
6444 together. This is primarily used by the @code{gnatchop} utility
6445 (@pxref{Renaming Files Using gnatchop}).
6448 @node Using gcc for Semantic Checking
6449 @subsection Using @command{gcc} for Semantic Checking
6452 @cindex @option{-gnatc} (@command{gcc})
6456 The @code{c} stands for ``check''.
6458 Causes the compiler to operate in semantic check mode,
6459 with full checking for all illegalities specified in the
6460 Ada Reference Manual, but without generation of any object code
6461 (no object file is generated).
6463 Because dependent files must be accessed, you must follow the GNAT
6464 semantic restrictions on file structuring to operate in this mode:
6468 The needed source files must be accessible
6469 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6472 Each file must contain only one compilation unit.
6475 The file name and unit name must match (@pxref{File Naming Rules}).
6478 The output consists of error messages as appropriate. No object file is
6479 generated. An @file{ALI} file is generated for use in the context of
6480 cross-reference tools, but this file is marked as not being suitable
6481 for binding (since no object file is generated).
6482 The checking corresponds exactly to the notion of
6483 legality in the Ada Reference Manual.
6485 Any unit can be compiled in semantics-checking-only mode, including
6486 units that would not normally be compiled (subunits,
6487 and specifications where a separate body is present).
6490 @node Compiling Different Versions of Ada
6491 @subsection Compiling Different Versions of Ada
6494 The switches described in this section allow you to explicitly specify
6495 the version of the Ada language that your programs are written in.
6496 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6497 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6498 indicate Ada 83 compatibility mode.
6501 @cindex Compatibility with Ada 83
6503 @item -gnat83 (Ada 83 Compatibility Mode)
6504 @cindex @option{-gnat83} (@command{gcc})
6505 @cindex ACVC, Ada 83 tests
6509 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6510 specifies that the program is to be compiled in Ada 83 mode. With
6511 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6512 semantics where this can be done easily.
6513 It is not possible to guarantee this switch does a perfect
6514 job; some subtle tests, such as are
6515 found in earlier ACVC tests (and that have been removed from the ACATS suite
6516 for Ada 95), might not compile correctly.
6517 Nevertheless, this switch may be useful in some circumstances, for example
6518 where, due to contractual reasons, existing code needs to be maintained
6519 using only Ada 83 features.
6521 With few exceptions (most notably the need to use @code{<>} on
6522 @cindex Generic formal parameters
6523 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6524 reserved words, and the use of packages
6525 with optional bodies), it is not necessary to specify the
6526 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6527 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6528 a correct Ada 83 program is usually also a correct program
6529 in these later versions of the language standard.
6530 For further information, please refer to @ref{Compatibility and Porting Guide}.
6532 @item -gnat95 (Ada 95 mode)
6533 @cindex @option{-gnat95} (@command{gcc})
6537 This switch directs the compiler to implement the Ada 95 version of the
6539 Since Ada 95 is almost completely upwards
6540 compatible with Ada 83, Ada 83 programs may generally be compiled using
6541 this switch (see the description of the @option{-gnat83} switch for further
6542 information about Ada 83 mode).
6543 If an Ada 2005 program is compiled in Ada 95 mode,
6544 uses of the new Ada 2005 features will cause error
6545 messages or warnings.
6547 This switch also can be used to cancel the effect of a previous
6548 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6550 @item -gnat05 (Ada 2005 mode)
6551 @cindex @option{-gnat05} (@command{gcc})
6552 @cindex Ada 2005 mode
6555 This switch directs the compiler to implement the Ada 2005 version of the
6557 Since Ada 2005 is almost completely upwards
6558 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6559 may generally be compiled using this switch (see the description of the
6560 @option{-gnat83} and @option{-gnat95} switches for further
6563 For information about the approved ``Ada Issues'' that have been incorporated
6564 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6565 Included with GNAT releases is a file @file{features-ada0y} that describes
6566 the set of implemented Ada 2005 features.
6570 @node Character Set Control
6571 @subsection Character Set Control
6573 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6574 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6577 Normally GNAT recognizes the Latin-1 character set in source program
6578 identifiers, as described in the Ada Reference Manual.
6580 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6581 single character ^^or word^ indicating the character set, as follows:
6585 ISO 8859-1 (Latin-1) identifiers
6588 ISO 8859-2 (Latin-2) letters allowed in identifiers
6591 ISO 8859-3 (Latin-3) letters allowed in identifiers
6594 ISO 8859-4 (Latin-4) letters allowed in identifiers
6597 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6600 ISO 8859-15 (Latin-9) letters allowed in identifiers
6603 IBM PC letters (code page 437) allowed in identifiers
6606 IBM PC letters (code page 850) allowed in identifiers
6608 @item ^f^FULL_UPPER^
6609 Full upper-half codes allowed in identifiers
6612 No upper-half codes allowed in identifiers
6615 Wide-character codes (that is, codes greater than 255)
6616 allowed in identifiers
6619 @xref{Foreign Language Representation}, for full details on the
6620 implementation of these character sets.
6622 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6623 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6624 Specify the method of encoding for wide characters.
6625 @var{e} is one of the following:
6630 Hex encoding (brackets coding also recognized)
6633 Upper half encoding (brackets encoding also recognized)
6636 Shift/JIS encoding (brackets encoding also recognized)
6639 EUC encoding (brackets encoding also recognized)
6642 UTF-8 encoding (brackets encoding also recognized)
6645 Brackets encoding only (default value)
6647 For full details on these encoding
6648 methods see @ref{Wide Character Encodings}.
6649 Note that brackets coding is always accepted, even if one of the other
6650 options is specified, so for example @option{-gnatW8} specifies that both
6651 brackets and UTF-8 encodings will be recognized. The units that are
6652 with'ed directly or indirectly will be scanned using the specified
6653 representation scheme, and so if one of the non-brackets scheme is
6654 used, it must be used consistently throughout the program. However,
6655 since brackets encoding is always recognized, it may be conveniently
6656 used in standard libraries, allowing these libraries to be used with
6657 any of the available coding schemes.
6660 If no @option{-gnatW?} parameter is present, then the default
6661 representation is normally Brackets encoding only. However, if the
6662 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6663 byte order mark or BOM for UTF-8), then these three characters are
6664 skipped and the default representation for the file is set to UTF-8.
6666 Note that the wide character representation that is specified (explicitly
6667 or by default) for the main program also acts as the default encoding used
6668 for Wide_Text_IO files if not specifically overridden by a WCEM form
6672 @node File Naming Control
6673 @subsection File Naming Control
6676 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6677 @cindex @option{-gnatk} (@command{gcc})
6678 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6679 1-999, indicates the maximum allowable length of a file name (not
6680 including the @file{.ads} or @file{.adb} extension). The default is not
6681 to enable file name krunching.
6683 For the source file naming rules, @xref{File Naming Rules}.
6686 @node Subprogram Inlining Control
6687 @subsection Subprogram Inlining Control
6692 @cindex @option{-gnatn} (@command{gcc})
6694 The @code{n} here is intended to suggest the first syllable of the
6697 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6698 inlining to actually occur, optimization must be enabled. To enable
6699 inlining of subprograms specified by pragma @code{Inline},
6700 you must also specify this switch.
6701 In the absence of this switch, GNAT does not attempt
6702 inlining and does not need to access the bodies of
6703 subprograms for which @code{pragma Inline} is specified if they are not
6704 in the current unit.
6706 If you specify this switch the compiler will access these bodies,
6707 creating an extra source dependency for the resulting object file, and
6708 where possible, the call will be inlined.
6709 For further details on when inlining is possible
6710 see @ref{Inlining of Subprograms}.
6713 @cindex @option{-gnatN} (@command{gcc})
6714 This switch activates front-end inlining which also
6715 generates additional dependencies.
6717 When using a gcc-based back end (in practice this means using any version
6718 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
6719 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
6720 Historically front end inlining was more extensive than the gcc back end
6721 inlining, but that is no longer the case.
6724 @node Auxiliary Output Control
6725 @subsection Auxiliary Output Control
6729 @cindex @option{-gnatt} (@command{gcc})
6730 @cindex Writing internal trees
6731 @cindex Internal trees, writing to file
6732 Causes GNAT to write the internal tree for a unit to a file (with the
6733 extension @file{.adt}.
6734 This not normally required, but is used by separate analysis tools.
6736 these tools do the necessary compilations automatically, so you should
6737 not have to specify this switch in normal operation.
6740 @cindex @option{-gnatu} (@command{gcc})
6741 Print a list of units required by this compilation on @file{stdout}.
6742 The listing includes all units on which the unit being compiled depends
6743 either directly or indirectly.
6746 @item -pass-exit-codes
6747 @cindex @option{-pass-exit-codes} (@command{gcc})
6748 If this switch is not used, the exit code returned by @command{gcc} when
6749 compiling multiple files indicates whether all source files have
6750 been successfully used to generate object files or not.
6752 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
6753 exit status and allows an integrated development environment to better
6754 react to a compilation failure. Those exit status are:
6758 There was an error in at least one source file.
6760 At least one source file did not generate an object file.
6762 The compiler died unexpectedly (internal error for example).
6764 An object file has been generated for every source file.
6769 @node Debugging Control
6770 @subsection Debugging Control
6774 @cindex Debugging options
6777 @cindex @option{-gnatd} (@command{gcc})
6778 Activate internal debugging switches. @var{x} is a letter or digit, or
6779 string of letters or digits, which specifies the type of debugging
6780 outputs desired. Normally these are used only for internal development
6781 or system debugging purposes. You can find full documentation for these
6782 switches in the body of the @code{Debug} unit in the compiler source
6783 file @file{debug.adb}.
6787 @cindex @option{-gnatG} (@command{gcc})
6788 This switch causes the compiler to generate auxiliary output containing
6789 a pseudo-source listing of the generated expanded code. Like most Ada
6790 compilers, GNAT works by first transforming the high level Ada code into
6791 lower level constructs. For example, tasking operations are transformed
6792 into calls to the tasking run-time routines. A unique capability of GNAT
6793 is to list this expanded code in a form very close to normal Ada source.
6794 This is very useful in understanding the implications of various Ada
6795 usage on the efficiency of the generated code. There are many cases in
6796 Ada (e.g.@: the use of controlled types), where simple Ada statements can
6797 generate a lot of run-time code. By using @option{-gnatG} you can identify
6798 these cases, and consider whether it may be desirable to modify the coding
6799 approach to improve efficiency.
6801 The optional parameter @code{nn} if present after -gnatG specifies an
6802 alternative maximum line length that overrides the normal default of 72.
6803 This value is in the range 40-999999, values less than 40 being silently
6806 The format of the output is very similar to standard Ada source, and is
6807 easily understood by an Ada programmer. The following special syntactic
6808 additions correspond to low level features used in the generated code that
6809 do not have any exact analogies in pure Ada source form. The following
6810 is a partial list of these special constructions. See the spec
6811 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6813 If the switch @option{-gnatL} is used in conjunction with
6814 @cindex @option{-gnatL} (@command{gcc})
6815 @option{-gnatG}, then the original source lines are interspersed
6816 in the expanded source (as comment lines with the original line number).
6819 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
6820 Shows the storage pool being used for an allocator.
6822 @item at end @var{procedure-name};
6823 Shows the finalization (cleanup) procedure for a scope.
6825 @item (if @var{expr} then @var{expr} else @var{expr})
6826 Conditional expression equivalent to the @code{x?y:z} construction in C.
6828 @item @var{target}^^^(@var{source})
6829 A conversion with floating-point truncation instead of rounding.
6831 @item @var{target}?(@var{source})
6832 A conversion that bypasses normal Ada semantic checking. In particular
6833 enumeration types and fixed-point types are treated simply as integers.
6835 @item @var{target}?^^^(@var{source})
6836 Combines the above two cases.
6838 @item @var{x} #/ @var{y}
6839 @itemx @var{x} #mod @var{y}
6840 @itemx @var{x} #* @var{y}
6841 @itemx @var{x} #rem @var{y}
6842 A division or multiplication of fixed-point values which are treated as
6843 integers without any kind of scaling.
6845 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
6846 Shows the storage pool associated with a @code{free} statement.
6848 @item [subtype or type declaration]
6849 Used to list an equivalent declaration for an internally generated
6850 type that is referenced elsewhere in the listing.
6852 @item freeze @var{type-name} @ovar{actions}
6853 Shows the point at which @var{type-name} is frozen, with possible
6854 associated actions to be performed at the freeze point.
6856 @item reference @var{itype}
6857 Reference (and hence definition) to internal type @var{itype}.
6859 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6860 Intrinsic function call.
6862 @item @var{label-name} : label
6863 Declaration of label @var{labelname}.
6865 @item #$ @var{subprogram-name}
6866 An implicit call to a run-time support routine
6867 (to meet the requirement of H.3.1(9) in a
6870 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
6871 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6872 @var{expr}, but handled more efficiently).
6874 @item [constraint_error]
6875 Raise the @code{Constraint_Error} exception.
6877 @item @var{expression}'reference
6878 A pointer to the result of evaluating @var{expression}.
6880 @item @var{target-type}!(@var{source-expression})
6881 An unchecked conversion of @var{source-expression} to @var{target-type}.
6883 @item [@var{numerator}/@var{denominator}]
6884 Used to represent internal real literals (that) have no exact
6885 representation in base 2-16 (for example, the result of compile time
6886 evaluation of the expression 1.0/27.0).
6890 @cindex @option{-gnatD} (@command{gcc})
6891 When used in conjunction with @option{-gnatG}, this switch causes
6892 the expanded source, as described above for
6893 @option{-gnatG} to be written to files with names
6894 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6895 instead of to the standard output file. For
6896 example, if the source file name is @file{hello.adb}, then a file
6897 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6898 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
6899 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6900 you to do source level debugging using the generated code which is
6901 sometimes useful for complex code, for example to find out exactly
6902 which part of a complex construction raised an exception. This switch
6903 also suppress generation of cross-reference information (see
6904 @option{-gnatx}) since otherwise the cross-reference information
6905 would refer to the @file{^.dg^.DG^} file, which would cause
6906 confusion since this is not the original source file.
6908 Note that @option{-gnatD} actually implies @option{-gnatG}
6909 automatically, so it is not necessary to give both options.
6910 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6912 If the switch @option{-gnatL} is used in conjunction with
6913 @cindex @option{-gnatL} (@command{gcc})
6914 @option{-gnatDG}, then the original source lines are interspersed
6915 in the expanded source (as comment lines with the original line number).
6917 The optional parameter @code{nn} if present after -gnatD specifies an
6918 alternative maximum line length that overrides the normal default of 72.
6919 This value is in the range 40-999999, values less than 40 being silently
6923 @cindex @option{-gnatr} (@command{gcc})
6924 @cindex pragma Restrictions
6925 This switch causes pragma Restrictions to be treated as Restriction_Warnings
6926 so that violation of restrictions causes warnings rather than illegalities.
6927 This is useful during the development process when new restrictions are added
6928 or investigated. The switch also causes pragma Profile to be treated as
6929 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
6930 restriction warnings rather than restrictions.
6933 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
6934 @cindex @option{-gnatR} (@command{gcc})
6935 This switch controls output from the compiler of a listing showing
6936 representation information for declared types and objects. For
6937 @option{-gnatR0}, no information is output (equivalent to omitting
6938 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6939 so @option{-gnatR} with no parameter has the same effect), size and alignment
6940 information is listed for declared array and record types. For
6941 @option{-gnatR2}, size and alignment information is listed for all
6942 declared types and objects. Finally @option{-gnatR3} includes symbolic
6943 expressions for values that are computed at run time for
6944 variant records. These symbolic expressions have a mostly obvious
6945 format with #n being used to represent the value of the n'th
6946 discriminant. See source files @file{repinfo.ads/adb} in the
6947 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6948 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
6949 the output is to a file with the name @file{^file.rep^file_REP^} where
6950 file is the name of the corresponding source file.
6953 @item /REPRESENTATION_INFO
6954 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
6955 This qualifier controls output from the compiler of a listing showing
6956 representation information for declared types and objects. For
6957 @option{/REPRESENTATION_INFO=NONE}, no information is output
6958 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6959 @option{/REPRESENTATION_INFO} without option is equivalent to
6960 @option{/REPRESENTATION_INFO=ARRAYS}.
6961 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6962 information is listed for declared array and record types. For
6963 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6964 is listed for all expression information for values that are computed
6965 at run time for variant records. These symbolic expressions have a mostly
6966 obvious format with #n being used to represent the value of the n'th
6967 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6968 @code{GNAT} sources for full details on the format of
6969 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6970 If _FILE is added at the end of an option
6971 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6972 then the output is to a file with the name @file{file_REP} where
6973 file is the name of the corresponding source file.
6975 Note that it is possible for record components to have zero size. In
6976 this case, the component clause uses an obvious extension of permitted
6977 Ada syntax, for example @code{at 0 range 0 .. -1}.
6979 Representation information requires that code be generated (since it is the
6980 code generator that lays out complex data structures). If an attempt is made
6981 to output representation information when no code is generated, for example
6982 when a subunit is compiled on its own, then no information can be generated
6983 and the compiler outputs a message to this effect.
6986 @cindex @option{-gnatS} (@command{gcc})
6987 The use of the switch @option{-gnatS} for an
6988 Ada compilation will cause the compiler to output a
6989 representation of package Standard in a form very
6990 close to standard Ada. It is not quite possible to
6991 do this entirely in standard Ada (since new
6992 numeric base types cannot be created in standard
6993 Ada), but the output is easily
6994 readable to any Ada programmer, and is useful to
6995 determine the characteristics of target dependent
6996 types in package Standard.
6999 @cindex @option{-gnatx} (@command{gcc})
7000 Normally the compiler generates full cross-referencing information in
7001 the @file{ALI} file. This information is used by a number of tools,
7002 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7003 suppresses this information. This saves some space and may slightly
7004 speed up compilation, but means that these tools cannot be used.
7007 @node Exception Handling Control
7008 @subsection Exception Handling Control
7011 GNAT uses two methods for handling exceptions at run-time. The
7012 @code{setjmp/longjmp} method saves the context when entering
7013 a frame with an exception handler. Then when an exception is
7014 raised, the context can be restored immediately, without the
7015 need for tracing stack frames. This method provides very fast
7016 exception propagation, but introduces significant overhead for
7017 the use of exception handlers, even if no exception is raised.
7019 The other approach is called ``zero cost'' exception handling.
7020 With this method, the compiler builds static tables to describe
7021 the exception ranges. No dynamic code is required when entering
7022 a frame containing an exception handler. When an exception is
7023 raised, the tables are used to control a back trace of the
7024 subprogram invocation stack to locate the required exception
7025 handler. This method has considerably poorer performance for
7026 the propagation of exceptions, but there is no overhead for
7027 exception handlers if no exception is raised. Note that in this
7028 mode and in the context of mixed Ada and C/C++ programming,
7029 to propagate an exception through a C/C++ code, the C/C++ code
7030 must be compiled with the @option{-funwind-tables} GCC's
7033 The following switches may be used to control which of the
7034 two exception handling methods is used.
7040 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7041 This switch causes the setjmp/longjmp run-time (when available) to be used
7042 for exception handling. If the default
7043 mechanism for the target is zero cost exceptions, then
7044 this switch can be used to modify this default, and must be
7045 used for all units in the partition.
7046 This option is rarely used. One case in which it may be
7047 advantageous is if you have an application where exception
7048 raising is common and the overall performance of the
7049 application is improved by favoring exception propagation.
7052 @cindex @option{--RTS=zcx} (@command{gnatmake})
7053 @cindex Zero Cost Exceptions
7054 This switch causes the zero cost approach to be used
7055 for exception handling. If this is the default mechanism for the
7056 target (see below), then this switch is unneeded. If the default
7057 mechanism for the target is setjmp/longjmp exceptions, then
7058 this switch can be used to modify this default, and must be
7059 used for all units in the partition.
7060 This option can only be used if the zero cost approach
7061 is available for the target in use, otherwise it will generate an error.
7065 The same option @option{--RTS} must be used both for @command{gcc}
7066 and @command{gnatbind}. Passing this option to @command{gnatmake}
7067 (@pxref{Switches for gnatmake}) will ensure the required consistency
7068 through the compilation and binding steps.
7070 @node Units to Sources Mapping Files
7071 @subsection Units to Sources Mapping Files
7075 @item -gnatem^^=^@var{path}
7076 @cindex @option{-gnatem} (@command{gcc})
7077 A mapping file is a way to communicate to the compiler two mappings:
7078 from unit names to file names (without any directory information) and from
7079 file names to path names (with full directory information). These mappings
7080 are used by the compiler to short-circuit the path search.
7082 The use of mapping files is not required for correct operation of the
7083 compiler, but mapping files can improve efficiency, particularly when
7084 sources are read over a slow network connection. In normal operation,
7085 you need not be concerned with the format or use of mapping files,
7086 and the @option{-gnatem} switch is not a switch that you would use
7087 explicitly. it is intended only for use by automatic tools such as
7088 @command{gnatmake} running under the project file facility. The
7089 description here of the format of mapping files is provided
7090 for completeness and for possible use by other tools.
7092 A mapping file is a sequence of sets of three lines. In each set,
7093 the first line is the unit name, in lower case, with ``@code{%s}''
7095 specs and ``@code{%b}'' appended for bodies; the second line is the
7096 file name; and the third line is the path name.
7102 /gnat/project1/sources/main.2.ada
7105 When the switch @option{-gnatem} is specified, the compiler will create
7106 in memory the two mappings from the specified file. If there is any problem
7107 (nonexistent file, truncated file or duplicate entries), no mapping will
7110 Several @option{-gnatem} switches may be specified; however, only the last
7111 one on the command line will be taken into account.
7113 When using a project file, @command{gnatmake} create a temporary mapping file
7114 and communicates it to the compiler using this switch.
7118 @node Integrated Preprocessing
7119 @subsection Integrated Preprocessing
7122 GNAT sources may be preprocessed immediately before compilation.
7123 In this case, the actual
7124 text of the source is not the text of the source file, but is derived from it
7125 through a process called preprocessing. Integrated preprocessing is specified
7126 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7127 indicates, through a text file, the preprocessing data to be used.
7128 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7131 Note that when integrated preprocessing is used, the output from the
7132 preprocessor is not written to any external file. Instead it is passed
7133 internally to the compiler. If you need to preserve the result of
7134 preprocessing in a file, then you should use @command{gnatprep}
7135 to perform the desired preprocessing in stand-alone mode.
7138 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7139 used when Integrated Preprocessing is used. The reason is that preprocessing
7140 with another Preprocessing Data file without changing the sources will
7141 not trigger recompilation without this switch.
7144 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7145 always trigger recompilation for sources that are preprocessed,
7146 because @command{gnatmake} cannot compute the checksum of the source after
7150 The actual preprocessing function is described in details in section
7151 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7152 preprocessing is triggered and parameterized.
7156 @item -gnatep=@var{file}
7157 @cindex @option{-gnatep} (@command{gcc})
7158 This switch indicates to the compiler the file name (without directory
7159 information) of the preprocessor data file to use. The preprocessor data file
7160 should be found in the source directories.
7163 A preprocessing data file is a text file with significant lines indicating
7164 how should be preprocessed either a specific source or all sources not
7165 mentioned in other lines. A significant line is a nonempty, non-comment line.
7166 Comments are similar to Ada comments.
7169 Each significant line starts with either a literal string or the character '*'.
7170 A literal string is the file name (without directory information) of the source
7171 to preprocess. A character '*' indicates the preprocessing for all the sources
7172 that are not specified explicitly on other lines (order of the lines is not
7173 significant). It is an error to have two lines with the same file name or two
7174 lines starting with the character '*'.
7177 After the file name or the character '*', another optional literal string
7178 indicating the file name of the definition file to be used for preprocessing
7179 (@pxref{Form of Definitions File}). The definition files are found by the
7180 compiler in one of the source directories. In some cases, when compiling
7181 a source in a directory other than the current directory, if the definition
7182 file is in the current directory, it may be necessary to add the current
7183 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7184 the compiler would not find the definition file.
7187 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7188 be found. Those ^switches^switches^ are:
7193 Causes both preprocessor lines and the lines deleted by
7194 preprocessing to be replaced by blank lines, preserving the line number.
7195 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7196 it cancels the effect of @option{-c}.
7199 Causes both preprocessor lines and the lines deleted
7200 by preprocessing to be retained as comments marked
7201 with the special string ``@code{--! }''.
7203 @item -Dsymbol=value
7204 Define or redefine a symbol, associated with value. A symbol is an Ada
7205 identifier, or an Ada reserved word, with the exception of @code{if},
7206 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7207 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7208 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7209 same name defined in a definition file.
7212 Causes a sorted list of symbol names and values to be
7213 listed on the standard output file.
7216 Causes undefined symbols to be treated as having the value @code{FALSE}
7218 of a preprocessor test. In the absence of this option, an undefined symbol in
7219 a @code{#if} or @code{#elsif} test will be treated as an error.
7224 Examples of valid lines in a preprocessor data file:
7227 "toto.adb" "prep.def" -u
7228 -- preprocess "toto.adb", using definition file "prep.def",
7229 -- undefined symbol are False.
7232 -- preprocess all other sources without a definition file;
7233 -- suppressed lined are commented; symbol VERSION has the value V101.
7235 "titi.adb" "prep2.def" -s
7236 -- preprocess "titi.adb", using definition file "prep2.def";
7237 -- list all symbols with their values.
7240 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7241 @cindex @option{-gnateD} (@command{gcc})
7242 Define or redefine a preprocessing symbol, associated with value. If no value
7243 is given on the command line, then the value of the symbol is @code{True}.
7244 A symbol is an identifier, following normal Ada (case-insensitive)
7245 rules for its syntax, and value is any sequence (including an empty sequence)
7246 of characters from the set (letters, digits, period, underline).
7247 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7248 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7251 A symbol declared with this ^switch^switch^ on the command line replaces a
7252 symbol with the same name either in a definition file or specified with a
7253 ^switch^switch^ -D in the preprocessor data file.
7256 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7259 When integrated preprocessing is performed and the preprocessor modifies
7260 the source text, write the result of this preprocessing into a file
7261 <source>^.prep^_prep^.
7265 @node Code Generation Control
7266 @subsection Code Generation Control
7270 The GCC technology provides a wide range of target dependent
7271 @option{-m} switches for controlling
7272 details of code generation with respect to different versions of
7273 architectures. This includes variations in instruction sets (e.g.@:
7274 different members of the power pc family), and different requirements
7275 for optimal arrangement of instructions (e.g.@: different members of
7276 the x86 family). The list of available @option{-m} switches may be
7277 found in the GCC documentation.
7279 Use of these @option{-m} switches may in some cases result in improved
7282 The GNAT Pro technology is tested and qualified without any
7283 @option{-m} switches,
7284 so generally the most reliable approach is to avoid the use of these
7285 switches. However, we generally expect most of these switches to work
7286 successfully with GNAT Pro, and many customers have reported successful
7287 use of these options.
7289 Our general advice is to avoid the use of @option{-m} switches unless
7290 special needs lead to requirements in this area. In particular,
7291 there is no point in using @option{-m} switches to improve performance
7292 unless you actually see a performance improvement.
7296 @subsection Return Codes
7297 @cindex Return Codes
7298 @cindex @option{/RETURN_CODES=VMS}
7301 On VMS, GNAT compiled programs return POSIX-style codes by default,
7302 e.g.@: @option{/RETURN_CODES=POSIX}.
7304 To enable VMS style return codes, use GNAT BIND and LINK with the option
7305 @option{/RETURN_CODES=VMS}. For example:
7308 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7309 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7313 Programs built with /RETURN_CODES=VMS are suitable to be called in
7314 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7315 are suitable for spawning with appropriate GNAT RTL routines.
7319 @node Search Paths and the Run-Time Library (RTL)
7320 @section Search Paths and the Run-Time Library (RTL)
7323 With the GNAT source-based library system, the compiler must be able to
7324 find source files for units that are needed by the unit being compiled.
7325 Search paths are used to guide this process.
7327 The compiler compiles one source file whose name must be given
7328 explicitly on the command line. In other words, no searching is done
7329 for this file. To find all other source files that are needed (the most
7330 common being the specs of units), the compiler examines the following
7331 directories, in the following order:
7335 The directory containing the source file of the main unit being compiled
7336 (the file name on the command line).
7339 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7340 @command{gcc} command line, in the order given.
7343 @findex ADA_PRJ_INCLUDE_FILE
7344 Each of the directories listed in the text file whose name is given
7345 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7348 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7349 driver when project files are used. It should not normally be set
7353 @findex ADA_INCLUDE_PATH
7354 Each of the directories listed in the value of the
7355 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7357 Construct this value
7358 exactly as the @env{PATH} environment variable: a list of directory
7359 names separated by colons (semicolons when working with the NT version).
7362 Normally, define this value as a logical name containing a comma separated
7363 list of directory names.
7365 This variable can also be defined by means of an environment string
7366 (an argument to the HP C exec* set of functions).
7370 DEFINE ANOTHER_PATH FOO:[BAG]
7371 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7374 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7375 first, followed by the standard Ada
7376 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7377 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7378 (Text_IO, Sequential_IO, etc)
7379 instead of the standard Ada packages. Thus, in order to get the standard Ada
7380 packages by default, ADA_INCLUDE_PATH must be redefined.
7384 The content of the @file{ada_source_path} file which is part of the GNAT
7385 installation tree and is used to store standard libraries such as the
7386 GNAT Run Time Library (RTL) source files.
7388 @ref{Installing a library}
7393 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7394 inhibits the use of the directory
7395 containing the source file named in the command line. You can still
7396 have this directory on your search path, but in this case it must be
7397 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7399 Specifying the switch @option{-nostdinc}
7400 inhibits the search of the default location for the GNAT Run Time
7401 Library (RTL) source files.
7403 The compiler outputs its object files and ALI files in the current
7406 Caution: The object file can be redirected with the @option{-o} switch;
7407 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7408 so the @file{ALI} file will not go to the right place. Therefore, you should
7409 avoid using the @option{-o} switch.
7413 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7414 children make up the GNAT RTL, together with the simple @code{System.IO}
7415 package used in the @code{"Hello World"} example. The sources for these units
7416 are needed by the compiler and are kept together in one directory. Not
7417 all of the bodies are needed, but all of the sources are kept together
7418 anyway. In a normal installation, you need not specify these directory
7419 names when compiling or binding. Either the environment variables or
7420 the built-in defaults cause these files to be found.
7422 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7423 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7424 consisting of child units of @code{GNAT}. This is a collection of generally
7425 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7426 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7428 Besides simplifying access to the RTL, a major use of search paths is
7429 in compiling sources from multiple directories. This can make
7430 development environments much more flexible.
7432 @node Order of Compilation Issues
7433 @section Order of Compilation Issues
7436 If, in our earlier example, there was a spec for the @code{hello}
7437 procedure, it would be contained in the file @file{hello.ads}; yet this
7438 file would not have to be explicitly compiled. This is the result of the
7439 model we chose to implement library management. Some of the consequences
7440 of this model are as follows:
7444 There is no point in compiling specs (except for package
7445 specs with no bodies) because these are compiled as needed by clients. If
7446 you attempt a useless compilation, you will receive an error message.
7447 It is also useless to compile subunits because they are compiled as needed
7451 There are no order of compilation requirements: performing a
7452 compilation never obsoletes anything. The only way you can obsolete
7453 something and require recompilations is to modify one of the
7454 source files on which it depends.
7457 There is no library as such, apart from the ALI files
7458 (@pxref{The Ada Library Information Files}, for information on the format
7459 of these files). For now we find it convenient to create separate ALI files,
7460 but eventually the information therein may be incorporated into the object
7464 When you compile a unit, the source files for the specs of all units
7465 that it @code{with}'s, all its subunits, and the bodies of any generics it
7466 instantiates must be available (reachable by the search-paths mechanism
7467 described above), or you will receive a fatal error message.
7474 The following are some typical Ada compilation command line examples:
7477 @item $ gcc -c xyz.adb
7478 Compile body in file @file{xyz.adb} with all default options.
7481 @item $ gcc -c -O2 -gnata xyz-def.adb
7484 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7487 Compile the child unit package in file @file{xyz-def.adb} with extensive
7488 optimizations, and pragma @code{Assert}/@code{Debug} statements
7491 @item $ gcc -c -gnatc abc-def.adb
7492 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7496 @node Binding Using gnatbind
7497 @chapter Binding Using @code{gnatbind}
7501 * Running gnatbind::
7502 * Switches for gnatbind::
7503 * Command-Line Access::
7504 * Search Paths for gnatbind::
7505 * Examples of gnatbind Usage::
7509 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7510 to bind compiled GNAT objects.
7512 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7513 driver (see @ref{The GNAT Driver and Project Files}).
7515 The @code{gnatbind} program performs four separate functions:
7519 Checks that a program is consistent, in accordance with the rules in
7520 Chapter 10 of the Ada Reference Manual. In particular, error
7521 messages are generated if a program uses inconsistent versions of a
7525 Checks that an acceptable order of elaboration exists for the program
7526 and issues an error message if it cannot find an order of elaboration
7527 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7530 Generates a main program incorporating the given elaboration order.
7531 This program is a small Ada package (body and spec) that
7532 must be subsequently compiled
7533 using the GNAT compiler. The necessary compilation step is usually
7534 performed automatically by @command{gnatlink}. The two most important
7535 functions of this program
7536 are to call the elaboration routines of units in an appropriate order
7537 and to call the main program.
7540 Determines the set of object files required by the given main program.
7541 This information is output in the forms of comments in the generated program,
7542 to be read by the @command{gnatlink} utility used to link the Ada application.
7545 @node Running gnatbind
7546 @section Running @code{gnatbind}
7549 The form of the @code{gnatbind} command is
7552 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7556 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7557 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7558 package in two files whose names are
7559 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7560 For example, if given the
7561 parameter @file{hello.ali}, for a main program contained in file
7562 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7563 and @file{b~hello.adb}.
7565 When doing consistency checking, the binder takes into consideration
7566 any source files it can locate. For example, if the binder determines
7567 that the given main program requires the package @code{Pack}, whose
7569 file is @file{pack.ali} and whose corresponding source spec file is
7570 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7571 (using the same search path conventions as previously described for the
7572 @command{gcc} command). If it can locate this source file, it checks that
7574 or source checksums of the source and its references to in @file{ALI} files
7575 match. In other words, any @file{ALI} files that mentions this spec must have
7576 resulted from compiling this version of the source file (or in the case
7577 where the source checksums match, a version close enough that the
7578 difference does not matter).
7580 @cindex Source files, use by binder
7581 The effect of this consistency checking, which includes source files, is
7582 that the binder ensures that the program is consistent with the latest
7583 version of the source files that can be located at bind time. Editing a
7584 source file without compiling files that depend on the source file cause
7585 error messages to be generated by the binder.
7587 For example, suppose you have a main program @file{hello.adb} and a
7588 package @code{P}, from file @file{p.ads} and you perform the following
7593 Enter @code{gcc -c hello.adb} to compile the main program.
7596 Enter @code{gcc -c p.ads} to compile package @code{P}.
7599 Edit file @file{p.ads}.
7602 Enter @code{gnatbind hello}.
7606 At this point, the file @file{p.ali} contains an out-of-date time stamp
7607 because the file @file{p.ads} has been edited. The attempt at binding
7608 fails, and the binder generates the following error messages:
7611 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7612 error: "p.ads" has been modified and must be recompiled
7616 Now both files must be recompiled as indicated, and then the bind can
7617 succeed, generating a main program. You need not normally be concerned
7618 with the contents of this file, but for reference purposes a sample
7619 binder output file is given in @ref{Example of Binder Output File}.
7621 In most normal usage, the default mode of @command{gnatbind} which is to
7622 generate the main package in Ada, as described in the previous section.
7623 In particular, this means that any Ada programmer can read and understand
7624 the generated main program. It can also be debugged just like any other
7625 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7626 @command{gnatbind} and @command{gnatlink}.
7628 However for some purposes it may be convenient to generate the main
7629 program in C rather than Ada. This may for example be helpful when you
7630 are generating a mixed language program with the main program in C. The
7631 GNAT compiler itself is an example.
7632 The use of the @option{^-C^/BIND_FILE=C^} switch
7633 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7634 be generated in C (and compiled using the gnu C compiler).
7636 @node Switches for gnatbind
7637 @section Switches for @command{gnatbind}
7640 The following switches are available with @code{gnatbind}; details will
7641 be presented in subsequent sections.
7644 * Consistency-Checking Modes::
7645 * Binder Error Message Control::
7646 * Elaboration Control::
7648 * Binding with Non-Ada Main Programs::
7649 * Binding Programs with No Main Subprogram::
7656 @cindex @option{--version} @command{gnatbind}
7657 Display Copyright and version, then exit disregarding all other options.
7660 @cindex @option{--help} @command{gnatbind}
7661 If @option{--version} was not used, display usage, then exit disregarding
7665 @cindex @option{-a} @command{gnatbind}
7666 Indicates that, if supported by the platform, the adainit procedure should
7667 be treated as an initialisation routine by the linker (a constructor). This
7668 is intended to be used by the Project Manager to automatically initialize
7669 shared Stand-Alone Libraries.
7671 @item ^-aO^/OBJECT_SEARCH^
7672 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7673 Specify directory to be searched for ALI files.
7675 @item ^-aI^/SOURCE_SEARCH^
7676 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7677 Specify directory to be searched for source file.
7679 @item ^-A^/BIND_FILE=ADA^
7680 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7681 Generate binder program in Ada (default)
7683 @item ^-b^/REPORT_ERRORS=BRIEF^
7684 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7685 Generate brief messages to @file{stderr} even if verbose mode set.
7687 @item ^-c^/NOOUTPUT^
7688 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7689 Check only, no generation of binder output file.
7691 @item ^-C^/BIND_FILE=C^
7692 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7693 Generate binder program in C
7695 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7696 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7697 This switch can be used to change the default task stack size value
7698 to a specified size @var{nn}, which is expressed in bytes by default, or
7699 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7701 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7702 in effect, to completing all task specs with
7703 @smallexample @c ada
7704 pragma Storage_Size (nn);
7706 When they do not already have such a pragma.
7708 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7709 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7710 This switch can be used to change the default secondary stack size value
7711 to a specified size @var{nn}, which is expressed in bytes by default, or
7712 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7715 The secondary stack is used to deal with functions that return a variable
7716 sized result, for example a function returning an unconstrained
7717 String. There are two ways in which this secondary stack is allocated.
7719 For most targets, the secondary stack is growing on demand and is allocated
7720 as a chain of blocks in the heap. The -D option is not very
7721 relevant. It only give some control over the size of the allocated
7722 blocks (whose size is the minimum of the default secondary stack size value,
7723 and the actual size needed for the current allocation request).
7725 For certain targets, notably VxWorks 653,
7726 the secondary stack is allocated by carving off a fixed ratio chunk of the
7727 primary task stack. The -D option is used to define the
7728 size of the environment task's secondary stack.
7730 @item ^-e^/ELABORATION_DEPENDENCIES^
7731 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
7732 Output complete list of elaboration-order dependencies.
7734 @item ^-E^/STORE_TRACEBACKS^
7735 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
7736 Store tracebacks in exception occurrences when the target supports it.
7737 This is the default with the zero cost exception mechanism.
7739 @c The following may get moved to an appendix
7740 This option is currently supported on the following targets:
7741 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
7743 See also the packages @code{GNAT.Traceback} and
7744 @code{GNAT.Traceback.Symbolic} for more information.
7746 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
7747 @command{gcc} option.
7750 @item ^-F^/FORCE_ELABS_FLAGS^
7751 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
7752 Force the checks of elaboration flags. @command{gnatbind} does not normally
7753 generate checks of elaboration flags for the main executable, except when
7754 a Stand-Alone Library is used. However, there are cases when this cannot be
7755 detected by gnatbind. An example is importing an interface of a Stand-Alone
7756 Library through a pragma Import and only specifying through a linker switch
7757 this Stand-Alone Library. This switch is used to guarantee that elaboration
7758 flag checks are generated.
7761 @cindex @option{^-h^/HELP^} (@command{gnatbind})
7762 Output usage (help) information
7765 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7766 Specify directory to be searched for source and ALI files.
7768 @item ^-I-^/NOCURRENT_DIRECTORY^
7769 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
7770 Do not look for sources in the current directory where @code{gnatbind} was
7771 invoked, and do not look for ALI files in the directory containing the
7772 ALI file named in the @code{gnatbind} command line.
7774 @item ^-l^/ORDER_OF_ELABORATION^
7775 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7776 Output chosen elaboration order.
7778 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
7779 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7780 Bind the units for library building. In this case the adainit and
7781 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
7782 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
7783 ^@var{xxx}final^@var{XXX}FINAL^.
7784 Implies ^-n^/NOCOMPILE^.
7786 (@xref{GNAT and Libraries}, for more details.)
7789 On OpenVMS, these init and final procedures are exported in uppercase
7790 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7791 the init procedure will be "TOTOINIT" and the exported name of the final
7792 procedure will be "TOTOFINAL".
7795 @item ^-Mxyz^/RENAME_MAIN=xyz^
7796 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7797 Rename generated main program from main to xyz. This option is
7798 supported on cross environments only.
7800 @item ^-m^/ERROR_LIMIT=^@var{n}
7801 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7802 Limit number of detected errors to @var{n}, where @var{n} is
7803 in the range 1..999_999. The default value if no switch is
7804 given is 9999. Binding is terminated if the limit is exceeded.
7806 Furthermore, under Windows, the sources pointed to by the libraries path
7807 set in the registry are not searched for.
7811 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7815 @cindex @option{-nostdinc} (@command{gnatbind})
7816 Do not look for sources in the system default directory.
7819 @cindex @option{-nostdlib} (@command{gnatbind})
7820 Do not look for library files in the system default directory.
7822 @item --RTS=@var{rts-path}
7823 @cindex @option{--RTS} (@code{gnatbind})
7824 Specifies the default location of the runtime library. Same meaning as the
7825 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
7827 @item ^-o ^/OUTPUT=^@var{file}
7828 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7829 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7830 Note that if this option is used, then linking must be done manually,
7831 gnatlink cannot be used.
7833 @item ^-O^/OBJECT_LIST^
7834 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7837 @item ^-p^/PESSIMISTIC_ELABORATION^
7838 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7839 Pessimistic (worst-case) elaboration order
7842 @cindex @option{^-R^-R^} (@command{gnatbind})
7843 Output closure source list.
7845 @item ^-s^/READ_SOURCES=ALL^
7846 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7847 Require all source files to be present.
7849 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7850 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7851 Specifies the value to be used when detecting uninitialized scalar
7852 objects with pragma Initialize_Scalars.
7853 The @var{xxx} ^string specified with the switch^option^ may be either
7855 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7856 @item ``@option{^lo^LOW^}'' for the lowest possible value
7857 @item ``@option{^hi^HIGH^}'' for the highest possible value
7858 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
7859 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
7862 In addition, you can specify @option{-Sev} to indicate that the value is
7863 to be set at run time. In this case, the program will look for an environment
7864 @cindex GNAT_INIT_SCALARS
7865 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
7866 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
7867 If no environment variable is found, or if it does not have a valid value,
7868 then the default is @option{in} (invalid values).
7872 @cindex @option{-static} (@code{gnatbind})
7873 Link against a static GNAT run time.
7876 @cindex @option{-shared} (@code{gnatbind})
7877 Link against a shared GNAT run time when available.
7880 @item ^-t^/NOTIME_STAMP_CHECK^
7881 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7882 Tolerate time stamp and other consistency errors
7884 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7885 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7886 Set the time slice value to @var{n} milliseconds. If the system supports
7887 the specification of a specific time slice value, then the indicated value
7888 is used. If the system does not support specific time slice values, but
7889 does support some general notion of round-robin scheduling, then any
7890 nonzero value will activate round-robin scheduling.
7892 A value of zero is treated specially. It turns off time
7893 slicing, and in addition, indicates to the tasking run time that the
7894 semantics should match as closely as possible the Annex D
7895 requirements of the Ada RM, and in particular sets the default
7896 scheduling policy to @code{FIFO_Within_Priorities}.
7898 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
7899 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
7900 Enable dynamic stack usage, with @var{n} results stored and displayed
7901 at program termination. A result is generated when a task
7902 terminates. Results that can't be stored are displayed on the fly, at
7903 task termination. This option is currently not supported on Itanium
7904 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
7906 @item ^-v^/REPORT_ERRORS=VERBOSE^
7907 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7908 Verbose mode. Write error messages, header, summary output to
7913 @cindex @option{-w} (@code{gnatbind})
7914 Warning mode (@var{x}=s/e for suppress/treat as error)
7918 @item /WARNINGS=NORMAL
7919 @cindex @option{/WARNINGS} (@code{gnatbind})
7920 Normal warnings mode. Warnings are issued but ignored
7922 @item /WARNINGS=SUPPRESS
7923 @cindex @option{/WARNINGS} (@code{gnatbind})
7924 All warning messages are suppressed
7926 @item /WARNINGS=ERROR
7927 @cindex @option{/WARNINGS} (@code{gnatbind})
7928 Warning messages are treated as fatal errors
7931 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7932 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7933 Override default wide character encoding for standard Text_IO files.
7935 @item ^-x^/READ_SOURCES=NONE^
7936 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7937 Exclude source files (check object consistency only).
7940 @item /READ_SOURCES=AVAILABLE
7941 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7942 Default mode, in which sources are checked for consistency only if
7946 @item ^-y^/ENABLE_LEAP_SECONDS^
7947 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
7948 Enable leap seconds support in @code{Ada.Calendar} and its children.
7950 @item ^-z^/ZERO_MAIN^
7951 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7957 You may obtain this listing of switches by running @code{gnatbind} with
7961 @node Consistency-Checking Modes
7962 @subsection Consistency-Checking Modes
7965 As described earlier, by default @code{gnatbind} checks
7966 that object files are consistent with one another and are consistent
7967 with any source files it can locate. The following switches control binder
7972 @item ^-s^/READ_SOURCES=ALL^
7973 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
7974 Require source files to be present. In this mode, the binder must be
7975 able to locate all source files that are referenced, in order to check
7976 their consistency. In normal mode, if a source file cannot be located it
7977 is simply ignored. If you specify this switch, a missing source
7980 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
7981 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
7982 Override default wide character encoding for standard Text_IO files.
7983 Normally the default wide character encoding method used for standard
7984 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
7985 the main source input (see description of switch
7986 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
7987 use of this switch for the binder (which has the same set of
7988 possible arguments) overrides this default as specified.
7990 @item ^-x^/READ_SOURCES=NONE^
7991 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
7992 Exclude source files. In this mode, the binder only checks that ALI
7993 files are consistent with one another. Source files are not accessed.
7994 The binder runs faster in this mode, and there is still a guarantee that
7995 the resulting program is self-consistent.
7996 If a source file has been edited since it was last compiled, and you
7997 specify this switch, the binder will not detect that the object
7998 file is out of date with respect to the source file. Note that this is the
7999 mode that is automatically used by @command{gnatmake} because in this
8000 case the checking against sources has already been performed by
8001 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8004 @item /READ_SOURCES=AVAILABLE
8005 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8006 This is the default mode in which source files are checked if they are
8007 available, and ignored if they are not available.
8011 @node Binder Error Message Control
8012 @subsection Binder Error Message Control
8015 The following switches provide control over the generation of error
8016 messages from the binder:
8020 @item ^-v^/REPORT_ERRORS=VERBOSE^
8021 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8022 Verbose mode. In the normal mode, brief error messages are generated to
8023 @file{stderr}. If this switch is present, a header is written
8024 to @file{stdout} and any error messages are directed to @file{stdout}.
8025 All that is written to @file{stderr} is a brief summary message.
8027 @item ^-b^/REPORT_ERRORS=BRIEF^
8028 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8029 Generate brief error messages to @file{stderr} even if verbose mode is
8030 specified. This is relevant only when used with the
8031 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8035 @cindex @option{-m} (@code{gnatbind})
8036 Limits the number of error messages to @var{n}, a decimal integer in the
8037 range 1-999. The binder terminates immediately if this limit is reached.
8040 @cindex @option{-M} (@code{gnatbind})
8041 Renames the generated main program from @code{main} to @code{xxx}.
8042 This is useful in the case of some cross-building environments, where
8043 the actual main program is separate from the one generated
8047 @item ^-ws^/WARNINGS=SUPPRESS^
8048 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8050 Suppress all warning messages.
8052 @item ^-we^/WARNINGS=ERROR^
8053 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8054 Treat any warning messages as fatal errors.
8057 @item /WARNINGS=NORMAL
8058 Standard mode with warnings generated, but warnings do not get treated
8062 @item ^-t^/NOTIME_STAMP_CHECK^
8063 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8064 @cindex Time stamp checks, in binder
8065 @cindex Binder consistency checks
8066 @cindex Consistency checks, in binder
8067 The binder performs a number of consistency checks including:
8071 Check that time stamps of a given source unit are consistent
8073 Check that checksums of a given source unit are consistent
8075 Check that consistent versions of @code{GNAT} were used for compilation
8077 Check consistency of configuration pragmas as required
8081 Normally failure of such checks, in accordance with the consistency
8082 requirements of the Ada Reference Manual, causes error messages to be
8083 generated which abort the binder and prevent the output of a binder
8084 file and subsequent link to obtain an executable.
8086 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8087 into warnings, so that
8088 binding and linking can continue to completion even in the presence of such
8089 errors. The result may be a failed link (due to missing symbols), or a
8090 non-functional executable which has undefined semantics.
8091 @emph{This means that
8092 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8096 @node Elaboration Control
8097 @subsection Elaboration Control
8100 The following switches provide additional control over the elaboration
8101 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8104 @item ^-p^/PESSIMISTIC_ELABORATION^
8105 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8106 Normally the binder attempts to choose an elaboration order that is
8107 likely to minimize the likelihood of an elaboration order error resulting
8108 in raising a @code{Program_Error} exception. This switch reverses the
8109 action of the binder, and requests that it deliberately choose an order
8110 that is likely to maximize the likelihood of an elaboration error.
8111 This is useful in ensuring portability and avoiding dependence on
8112 accidental fortuitous elaboration ordering.
8114 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8116 elaboration checking is used (@option{-gnatE} switch used for compilation).
8117 This is because in the default static elaboration mode, all necessary
8118 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8119 These implicit pragmas are still respected by the binder in
8120 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8121 safe elaboration order is assured.
8124 @node Output Control
8125 @subsection Output Control
8128 The following switches allow additional control over the output
8129 generated by the binder.
8134 @item ^-A^/BIND_FILE=ADA^
8135 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8136 Generate binder program in Ada (default). The binder program is named
8137 @file{b~@var{mainprog}.adb} by default. This can be changed with
8138 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8140 @item ^-c^/NOOUTPUT^
8141 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8142 Check only. Do not generate the binder output file. In this mode the
8143 binder performs all error checks but does not generate an output file.
8145 @item ^-C^/BIND_FILE=C^
8146 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8147 Generate binder program in C. The binder program is named
8148 @file{b_@var{mainprog}.c}.
8149 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8152 @item ^-e^/ELABORATION_DEPENDENCIES^
8153 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8154 Output complete list of elaboration-order dependencies, showing the
8155 reason for each dependency. This output can be rather extensive but may
8156 be useful in diagnosing problems with elaboration order. The output is
8157 written to @file{stdout}.
8160 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8161 Output usage information. The output is written to @file{stdout}.
8163 @item ^-K^/LINKER_OPTION_LIST^
8164 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8165 Output linker options to @file{stdout}. Includes library search paths,
8166 contents of pragmas Ident and Linker_Options, and libraries added
8169 @item ^-l^/ORDER_OF_ELABORATION^
8170 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8171 Output chosen elaboration order. The output is written to @file{stdout}.
8173 @item ^-O^/OBJECT_LIST^
8174 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8175 Output full names of all the object files that must be linked to provide
8176 the Ada component of the program. The output is written to @file{stdout}.
8177 This list includes the files explicitly supplied and referenced by the user
8178 as well as implicitly referenced run-time unit files. The latter are
8179 omitted if the corresponding units reside in shared libraries. The
8180 directory names for the run-time units depend on the system configuration.
8182 @item ^-o ^/OUTPUT=^@var{file}
8183 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8184 Set name of output file to @var{file} instead of the normal
8185 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8186 binder generated body filename. In C mode you would normally give
8187 @var{file} an extension of @file{.c} because it will be a C source program.
8188 Note that if this option is used, then linking must be done manually.
8189 It is not possible to use gnatlink in this case, since it cannot locate
8192 @item ^-r^/RESTRICTION_LIST^
8193 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8194 Generate list of @code{pragma Restrictions} that could be applied to
8195 the current unit. This is useful for code audit purposes, and also may
8196 be used to improve code generation in some cases.
8200 @node Binding with Non-Ada Main Programs
8201 @subsection Binding with Non-Ada Main Programs
8204 In our description so far we have assumed that the main
8205 program is in Ada, and that the task of the binder is to generate a
8206 corresponding function @code{main} that invokes this Ada main
8207 program. GNAT also supports the building of executable programs where
8208 the main program is not in Ada, but some of the called routines are
8209 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8210 The following switch is used in this situation:
8214 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8215 No main program. The main program is not in Ada.
8219 In this case, most of the functions of the binder are still required,
8220 but instead of generating a main program, the binder generates a file
8221 containing the following callable routines:
8226 You must call this routine to initialize the Ada part of the program by
8227 calling the necessary elaboration routines. A call to @code{adainit} is
8228 required before the first call to an Ada subprogram.
8230 Note that it is assumed that the basic execution environment must be setup
8231 to be appropriate for Ada execution at the point where the first Ada
8232 subprogram is called. In particular, if the Ada code will do any
8233 floating-point operations, then the FPU must be setup in an appropriate
8234 manner. For the case of the x86, for example, full precision mode is
8235 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8236 that the FPU is in the right state.
8240 You must call this routine to perform any library-level finalization
8241 required by the Ada subprograms. A call to @code{adafinal} is required
8242 after the last call to an Ada subprogram, and before the program
8247 If the @option{^-n^/NOMAIN^} switch
8248 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8249 @cindex Binder, multiple input files
8250 is given, more than one ALI file may appear on
8251 the command line for @code{gnatbind}. The normal @dfn{closure}
8252 calculation is performed for each of the specified units. Calculating
8253 the closure means finding out the set of units involved by tracing
8254 @code{with} references. The reason it is necessary to be able to
8255 specify more than one ALI file is that a given program may invoke two or
8256 more quite separate groups of Ada units.
8258 The binder takes the name of its output file from the last specified ALI
8259 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8260 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8261 The output is an Ada unit in source form that can
8262 be compiled with GNAT unless the -C switch is used in which case the
8263 output is a C source file, which must be compiled using the C compiler.
8264 This compilation occurs automatically as part of the @command{gnatlink}
8267 Currently the GNAT run time requires a FPU using 80 bits mode
8268 precision. Under targets where this is not the default it is required to
8269 call GNAT.Float_Control.Reset before using floating point numbers (this
8270 include float computation, float input and output) in the Ada code. A
8271 side effect is that this could be the wrong mode for the foreign code
8272 where floating point computation could be broken after this call.
8274 @node Binding Programs with No Main Subprogram
8275 @subsection Binding Programs with No Main Subprogram
8278 It is possible to have an Ada program which does not have a main
8279 subprogram. This program will call the elaboration routines of all the
8280 packages, then the finalization routines.
8282 The following switch is used to bind programs organized in this manner:
8285 @item ^-z^/ZERO_MAIN^
8286 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8287 Normally the binder checks that the unit name given on the command line
8288 corresponds to a suitable main subprogram. When this switch is used,
8289 a list of ALI files can be given, and the execution of the program
8290 consists of elaboration of these units in an appropriate order. Note
8291 that the default wide character encoding method for standard Text_IO
8292 files is always set to Brackets if this switch is set (you can use
8294 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8297 @node Command-Line Access
8298 @section Command-Line Access
8301 The package @code{Ada.Command_Line} provides access to the command-line
8302 arguments and program name. In order for this interface to operate
8303 correctly, the two variables
8315 are declared in one of the GNAT library routines. These variables must
8316 be set from the actual @code{argc} and @code{argv} values passed to the
8317 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8318 generates the C main program to automatically set these variables.
8319 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8320 set these variables. If they are not set, the procedures in
8321 @code{Ada.Command_Line} will not be available, and any attempt to use
8322 them will raise @code{Constraint_Error}. If command line access is
8323 required, your main program must set @code{gnat_argc} and
8324 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8327 @node Search Paths for gnatbind
8328 @section Search Paths for @code{gnatbind}
8331 The binder takes the name of an ALI file as its argument and needs to
8332 locate source files as well as other ALI files to verify object consistency.
8334 For source files, it follows exactly the same search rules as @command{gcc}
8335 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8336 directories searched are:
8340 The directory containing the ALI file named in the command line, unless
8341 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8344 All directories specified by @option{^-I^/SEARCH^}
8345 switches on the @code{gnatbind}
8346 command line, in the order given.
8349 @findex ADA_PRJ_OBJECTS_FILE
8350 Each of the directories listed in the text file whose name is given
8351 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8354 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8355 driver when project files are used. It should not normally be set
8359 @findex ADA_OBJECTS_PATH
8360 Each of the directories listed in the value of the
8361 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8363 Construct this value
8364 exactly as the @env{PATH} environment variable: a list of directory
8365 names separated by colons (semicolons when working with the NT version
8369 Normally, define this value as a logical name containing a comma separated
8370 list of directory names.
8372 This variable can also be defined by means of an environment string
8373 (an argument to the HP C exec* set of functions).
8377 DEFINE ANOTHER_PATH FOO:[BAG]
8378 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8381 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8382 first, followed by the standard Ada
8383 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8384 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8385 (Text_IO, Sequential_IO, etc)
8386 instead of the standard Ada packages. Thus, in order to get the standard Ada
8387 packages by default, ADA_OBJECTS_PATH must be redefined.
8391 The content of the @file{ada_object_path} file which is part of the GNAT
8392 installation tree and is used to store standard libraries such as the
8393 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8396 @ref{Installing a library}
8401 In the binder the switch @option{^-I^/SEARCH^}
8402 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8403 is used to specify both source and
8404 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8405 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8406 instead if you want to specify
8407 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8408 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8409 if you want to specify library paths
8410 only. This means that for the binder
8411 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8412 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8413 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8414 The binder generates the bind file (a C language source file) in the
8415 current working directory.
8421 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8422 children make up the GNAT Run-Time Library, together with the package
8423 GNAT and its children, which contain a set of useful additional
8424 library functions provided by GNAT. The sources for these units are
8425 needed by the compiler and are kept together in one directory. The ALI
8426 files and object files generated by compiling the RTL are needed by the
8427 binder and the linker and are kept together in one directory, typically
8428 different from the directory containing the sources. In a normal
8429 installation, you need not specify these directory names when compiling
8430 or binding. Either the environment variables or the built-in defaults
8431 cause these files to be found.
8433 Besides simplifying access to the RTL, a major use of search paths is
8434 in compiling sources from multiple directories. This can make
8435 development environments much more flexible.
8437 @node Examples of gnatbind Usage
8438 @section Examples of @code{gnatbind} Usage
8441 This section contains a number of examples of using the GNAT binding
8442 utility @code{gnatbind}.
8445 @item gnatbind hello
8446 The main program @code{Hello} (source program in @file{hello.adb}) is
8447 bound using the standard switch settings. The generated main program is
8448 @file{b~hello.adb}. This is the normal, default use of the binder.
8451 @item gnatbind hello -o mainprog.adb
8454 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8456 The main program @code{Hello} (source program in @file{hello.adb}) is
8457 bound using the standard switch settings. The generated main program is
8458 @file{mainprog.adb} with the associated spec in
8459 @file{mainprog.ads}. Note that you must specify the body here not the
8460 spec, in the case where the output is in Ada. Note that if this option
8461 is used, then linking must be done manually, since gnatlink will not
8462 be able to find the generated file.
8465 @item gnatbind main -C -o mainprog.c -x
8468 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8470 The main program @code{Main} (source program in
8471 @file{main.adb}) is bound, excluding source files from the
8472 consistency checking, generating
8473 the file @file{mainprog.c}.
8476 @item gnatbind -x main_program -C -o mainprog.c
8477 This command is exactly the same as the previous example. Switches may
8478 appear anywhere in the command line, and single letter switches may be
8479 combined into a single switch.
8483 @item gnatbind -n math dbase -C -o ada-control.c
8486 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8488 The main program is in a language other than Ada, but calls to
8489 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8490 to @code{gnatbind} generates the file @file{ada-control.c} containing
8491 the @code{adainit} and @code{adafinal} routines to be called before and
8492 after accessing the Ada units.
8495 @c ------------------------------------
8496 @node Linking Using gnatlink
8497 @chapter Linking Using @command{gnatlink}
8498 @c ------------------------------------
8502 This chapter discusses @command{gnatlink}, a tool that links
8503 an Ada program and builds an executable file. This utility
8504 invokes the system linker ^(via the @command{gcc} command)^^
8505 with a correct list of object files and library references.
8506 @command{gnatlink} automatically determines the list of files and
8507 references for the Ada part of a program. It uses the binder file
8508 generated by the @command{gnatbind} to determine this list.
8510 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8511 driver (see @ref{The GNAT Driver and Project Files}).
8514 * Running gnatlink::
8515 * Switches for gnatlink::
8518 @node Running gnatlink
8519 @section Running @command{gnatlink}
8522 The form of the @command{gnatlink} command is
8525 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8526 @ovar{non-Ada objects} @ovar{linker options}
8530 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8532 or linker options) may be in any order, provided that no non-Ada object may
8533 be mistaken for a main @file{ALI} file.
8534 Any file name @file{F} without the @file{.ali}
8535 extension will be taken as the main @file{ALI} file if a file exists
8536 whose name is the concatenation of @file{F} and @file{.ali}.
8539 @file{@var{mainprog}.ali} references the ALI file of the main program.
8540 The @file{.ali} extension of this file can be omitted. From this
8541 reference, @command{gnatlink} locates the corresponding binder file
8542 @file{b~@var{mainprog}.adb} and, using the information in this file along
8543 with the list of non-Ada objects and linker options, constructs a
8544 linker command file to create the executable.
8546 The arguments other than the @command{gnatlink} switches and the main
8547 @file{ALI} file are passed to the linker uninterpreted.
8548 They typically include the names of
8549 object files for units written in other languages than Ada and any library
8550 references required to resolve references in any of these foreign language
8551 units, or in @code{Import} pragmas in any Ada units.
8553 @var{linker options} is an optional list of linker specific
8555 The default linker called by gnatlink is @command{gcc} which in
8556 turn calls the appropriate system linker.
8557 Standard options for the linker such as @option{-lmy_lib} or
8558 @option{-Ldir} can be added as is.
8559 For options that are not recognized by
8560 @command{gcc} as linker options, use the @command{gcc} switches
8561 @option{-Xlinker} or @option{-Wl,}.
8562 Refer to the GCC documentation for
8563 details. Here is an example showing how to generate a linker map:
8566 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8569 Using @var{linker options} it is possible to set the program stack and
8572 See @ref{Setting Stack Size from gnatlink} and
8573 @ref{Setting Heap Size from gnatlink}.
8576 @command{gnatlink} determines the list of objects required by the Ada
8577 program and prepends them to the list of objects passed to the linker.
8578 @command{gnatlink} also gathers any arguments set by the use of
8579 @code{pragma Linker_Options} and adds them to the list of arguments
8580 presented to the linker.
8583 @command{gnatlink} accepts the following types of extra files on the command
8584 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8585 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8586 handled according to their extension.
8589 @node Switches for gnatlink
8590 @section Switches for @command{gnatlink}
8593 The following switches are available with the @command{gnatlink} utility:
8599 @cindex @option{--version} @command{gnatlink}
8600 Display Copyright and version, then exit disregarding all other options.
8603 @cindex @option{--help} @command{gnatlink}
8604 If @option{--version} was not used, display usage, then exit disregarding
8607 @item ^-A^/BIND_FILE=ADA^
8608 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8609 The binder has generated code in Ada. This is the default.
8611 @item ^-C^/BIND_FILE=C^
8612 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8613 If instead of generating a file in Ada, the binder has generated one in
8614 C, then the linker needs to know about it. Use this switch to signal
8615 to @command{gnatlink} that the binder has generated C code rather than
8618 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8619 @cindex Command line length
8620 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8621 On some targets, the command line length is limited, and @command{gnatlink}
8622 will generate a separate file for the linker if the list of object files
8624 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8625 to be generated even if
8626 the limit is not exceeded. This is useful in some cases to deal with
8627 special situations where the command line length is exceeded.
8630 @cindex Debugging information, including
8631 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8632 The option to include debugging information causes the Ada bind file (in
8633 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8634 @option{^-g^/DEBUG^}.
8635 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8636 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8637 Without @option{^-g^/DEBUG^}, the binder removes these files by
8638 default. The same procedure apply if a C bind file was generated using
8639 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8640 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8642 @item ^-n^/NOCOMPILE^
8643 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8644 Do not compile the file generated by the binder. This may be used when
8645 a link is rerun with different options, but there is no need to recompile
8649 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8650 Causes additional information to be output, including a full list of the
8651 included object files. This switch option is most useful when you want
8652 to see what set of object files are being used in the link step.
8654 @item ^-v -v^/VERBOSE/VERBOSE^
8655 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8656 Very verbose mode. Requests that the compiler operate in verbose mode when
8657 it compiles the binder file, and that the system linker run in verbose mode.
8659 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8660 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8661 @var{exec-name} specifies an alternate name for the generated
8662 executable program. If this switch is omitted, the executable has the same
8663 name as the main unit. For example, @code{gnatlink try.ali} creates
8664 an executable called @file{^try^TRY.EXE^}.
8667 @item -b @var{target}
8668 @cindex @option{-b} (@command{gnatlink})
8669 Compile your program to run on @var{target}, which is the name of a
8670 system configuration. You must have a GNAT cross-compiler built if
8671 @var{target} is not the same as your host system.
8674 @cindex @option{-B} (@command{gnatlink})
8675 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8676 from @var{dir} instead of the default location. Only use this switch
8677 when multiple versions of the GNAT compiler are available.
8678 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8679 for further details. You would normally use the @option{-b} or
8680 @option{-V} switch instead.
8682 @item --GCC=@var{compiler_name}
8683 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8684 Program used for compiling the binder file. The default is
8685 @command{gcc}. You need to use quotes around @var{compiler_name} if
8686 @code{compiler_name} contains spaces or other separator characters.
8687 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8688 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8689 inserted after your command name. Thus in the above example the compiler
8690 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8691 A limitation of this syntax is that the name and path name of the executable
8692 itself must not include any embedded spaces. If the compiler executable is
8693 different from the default one (gcc or <prefix>-gcc), then the back-end
8694 switches in the ALI file are not used to compile the binder generated source.
8695 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8696 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8697 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8698 is taken into account. However, all the additional switches are also taken
8700 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8701 @option{--GCC="bar -x -y -z -t"}.
8703 @item --LINK=@var{name}
8704 @cindex @option{--LINK=} (@command{gnatlink})
8705 @var{name} is the name of the linker to be invoked. This is especially
8706 useful in mixed language programs since languages such as C++ require
8707 their own linker to be used. When this switch is omitted, the default
8708 name for the linker is @command{gcc}. When this switch is used, the
8709 specified linker is called instead of @command{gcc} with exactly the same
8710 parameters that would have been passed to @command{gcc} so if the desired
8711 linker requires different parameters it is necessary to use a wrapper
8712 script that massages the parameters before invoking the real linker. It
8713 may be useful to control the exact invocation by using the verbose
8719 @item /DEBUG=TRACEBACK
8720 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
8721 This qualifier causes sufficient information to be included in the
8722 executable file to allow a traceback, but does not include the full
8723 symbol information needed by the debugger.
8725 @item /IDENTIFICATION="<string>"
8726 @code{"<string>"} specifies the string to be stored in the image file
8727 identification field in the image header.
8728 It overrides any pragma @code{Ident} specified string.
8730 @item /NOINHIBIT-EXEC
8731 Generate the executable file even if there are linker warnings.
8733 @item /NOSTART_FILES
8734 Don't link in the object file containing the ``main'' transfer address.
8735 Used when linking with a foreign language main program compiled with an
8739 Prefer linking with object libraries over sharable images, even without
8745 @node The GNAT Make Program gnatmake
8746 @chapter The GNAT Make Program @command{gnatmake}
8750 * Running gnatmake::
8751 * Switches for gnatmake::
8752 * Mode Switches for gnatmake::
8753 * Notes on the Command Line::
8754 * How gnatmake Works::
8755 * Examples of gnatmake Usage::
8758 A typical development cycle when working on an Ada program consists of
8759 the following steps:
8763 Edit some sources to fix bugs.
8769 Compile all sources affected.
8779 The third step can be tricky, because not only do the modified files
8780 @cindex Dependency rules
8781 have to be compiled, but any files depending on these files must also be
8782 recompiled. The dependency rules in Ada can be quite complex, especially
8783 in the presence of overloading, @code{use} clauses, generics and inlined
8786 @command{gnatmake} automatically takes care of the third and fourth steps
8787 of this process. It determines which sources need to be compiled,
8788 compiles them, and binds and links the resulting object files.
8790 Unlike some other Ada make programs, the dependencies are always
8791 accurately recomputed from the new sources. The source based approach of
8792 the GNAT compilation model makes this possible. This means that if
8793 changes to the source program cause corresponding changes in
8794 dependencies, they will always be tracked exactly correctly by
8797 @node Running gnatmake
8798 @section Running @command{gnatmake}
8801 The usual form of the @command{gnatmake} command is
8804 $ gnatmake @ovar{switches} @var{file_name}
8805 @ovar{file_names} @ovar{mode_switches}
8809 The only required argument is one @var{file_name}, which specifies
8810 a compilation unit that is a main program. Several @var{file_names} can be
8811 specified: this will result in several executables being built.
8812 If @code{switches} are present, they can be placed before the first
8813 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8814 If @var{mode_switches} are present, they must always be placed after
8815 the last @var{file_name} and all @code{switches}.
8817 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
8818 extension may be omitted from the @var{file_name} arguments. However, if
8819 you are using non-standard extensions, then it is required that the
8820 extension be given. A relative or absolute directory path can be
8821 specified in a @var{file_name}, in which case, the input source file will
8822 be searched for in the specified directory only. Otherwise, the input
8823 source file will first be searched in the directory where
8824 @command{gnatmake} was invoked and if it is not found, it will be search on
8825 the source path of the compiler as described in
8826 @ref{Search Paths and the Run-Time Library (RTL)}.
8828 All @command{gnatmake} output (except when you specify
8829 @option{^-M^/DEPENDENCIES_LIST^}) is to
8830 @file{stderr}. The output produced by the
8831 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8834 @node Switches for gnatmake
8835 @section Switches for @command{gnatmake}
8838 You may specify any of the following switches to @command{gnatmake}:
8844 @cindex @option{--version} @command{gnatmake}
8845 Display Copyright and version, then exit disregarding all other options.
8848 @cindex @option{--help} @command{gnatmake}
8849 If @option{--version} was not used, display usage, then exit disregarding
8853 @item --GCC=@var{compiler_name}
8854 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
8855 Program used for compiling. The default is `@command{gcc}'. You need to use
8856 quotes around @var{compiler_name} if @code{compiler_name} contains
8857 spaces or other separator characters. As an example @option{--GCC="foo -x
8858 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
8859 compiler. A limitation of this syntax is that the name and path name of
8860 the executable itself must not include any embedded spaces. Note that
8861 switch @option{-c} is always inserted after your command name. Thus in the
8862 above example the compiler command that will be used by @command{gnatmake}
8863 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
8864 used, only the last @var{compiler_name} is taken into account. However,
8865 all the additional switches are also taken into account. Thus,
8866 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8867 @option{--GCC="bar -x -y -z -t"}.
8869 @item --GNATBIND=@var{binder_name}
8870 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
8871 Program used for binding. The default is `@code{gnatbind}'. You need to
8872 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8873 or other separator characters. As an example @option{--GNATBIND="bar -x
8874 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
8875 binder. Binder switches that are normally appended by @command{gnatmake}
8876 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8877 A limitation of this syntax is that the name and path name of the executable
8878 itself must not include any embedded spaces.
8880 @item --GNATLINK=@var{linker_name}
8881 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
8882 Program used for linking. The default is `@command{gnatlink}'. You need to
8883 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8884 or other separator characters. As an example @option{--GNATLINK="lan -x
8885 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
8886 linker. Linker switches that are normally appended by @command{gnatmake} to
8887 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
8888 A limitation of this syntax is that the name and path name of the executable
8889 itself must not include any embedded spaces.
8893 @item ^-a^/ALL_FILES^
8894 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
8895 Consider all files in the make process, even the GNAT internal system
8896 files (for example, the predefined Ada library files), as well as any
8897 locked files. Locked files are files whose ALI file is write-protected.
8899 @command{gnatmake} does not check these files,
8900 because the assumption is that the GNAT internal files are properly up
8901 to date, and also that any write protected ALI files have been properly
8902 installed. Note that if there is an installation problem, such that one
8903 of these files is not up to date, it will be properly caught by the
8905 You may have to specify this switch if you are working on GNAT
8906 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8907 in conjunction with @option{^-f^/FORCE_COMPILE^}
8908 if you need to recompile an entire application,
8909 including run-time files, using special configuration pragmas,
8910 such as a @code{Normalize_Scalars} pragma.
8913 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8916 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8919 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8922 @item ^-b^/ACTIONS=BIND^
8923 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
8924 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8925 compilation and binding, but no link.
8926 Can be combined with @option{^-l^/ACTIONS=LINK^}
8927 to do binding and linking. When not combined with
8928 @option{^-c^/ACTIONS=COMPILE^}
8929 all the units in the closure of the main program must have been previously
8930 compiled and must be up to date. The root unit specified by @var{file_name}
8931 may be given without extension, with the source extension or, if no GNAT
8932 Project File is specified, with the ALI file extension.
8934 @item ^-c^/ACTIONS=COMPILE^
8935 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
8936 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8937 is also specified. Do not perform linking, except if both
8938 @option{^-b^/ACTIONS=BIND^} and
8939 @option{^-l^/ACTIONS=LINK^} are also specified.
8940 If the root unit specified by @var{file_name} is not a main unit, this is the
8941 default. Otherwise @command{gnatmake} will attempt binding and linking
8942 unless all objects are up to date and the executable is more recent than
8946 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
8947 Use a temporary mapping file. A mapping file is a way to communicate to the
8948 compiler two mappings: from unit names to file names (without any directory
8949 information) and from file names to path names (with full directory
8950 information). These mappings are used by the compiler to short-circuit the path
8951 search. When @command{gnatmake} is invoked with this switch, it will create
8952 a temporary mapping file, initially populated by the project manager,
8953 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8954 Each invocation of the compiler will add the newly accessed sources to the
8955 mapping file. This will improve the source search during the next invocation
8958 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8959 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
8960 Use a specific mapping file. The file, specified as a path name (absolute or
8961 relative) by this switch, should already exist, otherwise the switch is
8962 ineffective. The specified mapping file will be communicated to the compiler.
8963 This switch is not compatible with a project file
8964 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8965 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8967 @item ^-d^/DISPLAY_PROGRESS^
8968 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
8969 Display progress for each source, up to date or not, as a single line
8972 completed x out of y (zz%)
8975 If the file needs to be compiled this is displayed after the invocation of
8976 the compiler. These lines are displayed even in quiet output mode.
8978 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
8979 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
8980 Put all object files and ALI file in directory @var{dir}.
8981 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
8982 and ALI files go in the current working directory.
8984 This switch cannot be used when using a project file.
8988 @cindex @option{-eL} (@command{gnatmake})
8989 Follow all symbolic links when processing project files.
8992 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
8993 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
8994 Output the commands for the compiler, the binder and the linker
8995 on ^standard output^SYS$OUTPUT^,
8996 instead of ^standard error^SYS$ERROR^.
8998 @item ^-f^/FORCE_COMPILE^
8999 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9000 Force recompilations. Recompile all sources, even though some object
9001 files may be up to date, but don't recompile predefined or GNAT internal
9002 files or locked files (files with a write-protected ALI file),
9003 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9005 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9006 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9007 When using project files, if some errors or warnings are detected during
9008 parsing and verbose mode is not in effect (no use of switch
9009 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9010 file, rather than its simple file name.
9013 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9014 Enable debugging. This switch is simply passed to the compiler and to the
9017 @item ^-i^/IN_PLACE^
9018 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9019 In normal mode, @command{gnatmake} compiles all object files and ALI files
9020 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9021 then instead object files and ALI files that already exist are overwritten
9022 in place. This means that once a large project is organized into separate
9023 directories in the desired manner, then @command{gnatmake} will automatically
9024 maintain and update this organization. If no ALI files are found on the
9025 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9026 the new object and ALI files are created in the
9027 directory containing the source being compiled. If another organization
9028 is desired, where objects and sources are kept in different directories,
9029 a useful technique is to create dummy ALI files in the desired directories.
9030 When detecting such a dummy file, @command{gnatmake} will be forced to
9031 recompile the corresponding source file, and it will be put the resulting
9032 object and ALI files in the directory where it found the dummy file.
9034 @item ^-j^/PROCESSES=^@var{n}
9035 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9036 @cindex Parallel make
9037 Use @var{n} processes to carry out the (re)compilations. On a
9038 multiprocessor machine compilations will occur in parallel. In the
9039 event of compilation errors, messages from various compilations might
9040 get interspersed (but @command{gnatmake} will give you the full ordered
9041 list of failing compiles at the end). If this is problematic, rerun
9042 the make process with n set to 1 to get a clean list of messages.
9044 @item ^-k^/CONTINUE_ON_ERROR^
9045 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9046 Keep going. Continue as much as possible after a compilation error. To
9047 ease the programmer's task in case of compilation errors, the list of
9048 sources for which the compile fails is given when @command{gnatmake}
9051 If @command{gnatmake} is invoked with several @file{file_names} and with this
9052 switch, if there are compilation errors when building an executable,
9053 @command{gnatmake} will not attempt to build the following executables.
9055 @item ^-l^/ACTIONS=LINK^
9056 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9057 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9058 and linking. Linking will not be performed if combined with
9059 @option{^-c^/ACTIONS=COMPILE^}
9060 but not with @option{^-b^/ACTIONS=BIND^}.
9061 When not combined with @option{^-b^/ACTIONS=BIND^}
9062 all the units in the closure of the main program must have been previously
9063 compiled and must be up to date, and the main program needs to have been bound.
9064 The root unit specified by @var{file_name}
9065 may be given without extension, with the source extension or, if no GNAT
9066 Project File is specified, with the ALI file extension.
9068 @item ^-m^/MINIMAL_RECOMPILATION^
9069 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9070 Specify that the minimum necessary amount of recompilations
9071 be performed. In this mode @command{gnatmake} ignores time
9072 stamp differences when the only
9073 modifications to a source file consist in adding/removing comments,
9074 empty lines, spaces or tabs. This means that if you have changed the
9075 comments in a source file or have simply reformatted it, using this
9076 switch will tell @command{gnatmake} not to recompile files that depend on it
9077 (provided other sources on which these files depend have undergone no
9078 semantic modifications). Note that the debugging information may be
9079 out of date with respect to the sources if the @option{-m} switch causes
9080 a compilation to be switched, so the use of this switch represents a
9081 trade-off between compilation time and accurate debugging information.
9083 @item ^-M^/DEPENDENCIES_LIST^
9084 @cindex Dependencies, producing list
9085 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9086 Check if all objects are up to date. If they are, output the object
9087 dependences to @file{stdout} in a form that can be directly exploited in
9088 a @file{Makefile}. By default, each source file is prefixed with its
9089 (relative or absolute) directory name. This name is whatever you
9090 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9091 and @option{^-I^/SEARCH^} switches. If you use
9092 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9093 @option{^-q^/QUIET^}
9094 (see below), only the source file names,
9095 without relative paths, are output. If you just specify the
9096 @option{^-M^/DEPENDENCIES_LIST^}
9097 switch, dependencies of the GNAT internal system files are omitted. This
9098 is typically what you want. If you also specify
9099 the @option{^-a^/ALL_FILES^} switch,
9100 dependencies of the GNAT internal files are also listed. Note that
9101 dependencies of the objects in external Ada libraries (see switch
9102 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9105 @item ^-n^/DO_OBJECT_CHECK^
9106 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9107 Don't compile, bind, or link. Checks if all objects are up to date.
9108 If they are not, the full name of the first file that needs to be
9109 recompiled is printed.
9110 Repeated use of this option, followed by compiling the indicated source
9111 file, will eventually result in recompiling all required units.
9113 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9114 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9115 Output executable name. The name of the final executable program will be
9116 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9117 name for the executable will be the name of the input file in appropriate form
9118 for an executable file on the host system.
9120 This switch cannot be used when invoking @command{gnatmake} with several
9123 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9124 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9125 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9126 automatically missing object directories, library directories and exec
9129 @item ^-P^/PROJECT_FILE=^@var{project}
9130 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9131 Use project file @var{project}. Only one such switch can be used.
9132 @xref{gnatmake and Project Files}.
9135 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9136 Quiet. When this flag is not set, the commands carried out by
9137 @command{gnatmake} are displayed.
9139 @item ^-s^/SWITCH_CHECK/^
9140 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9141 Recompile if compiler switches have changed since last compilation.
9142 All compiler switches but -I and -o are taken into account in the
9144 orders between different ``first letter'' switches are ignored, but
9145 orders between same switches are taken into account. For example,
9146 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9147 is equivalent to @option{-O -g}.
9149 This switch is recommended when Integrated Preprocessing is used.
9152 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9153 Unique. Recompile at most the main files. It implies -c. Combined with
9154 -f, it is equivalent to calling the compiler directly. Note that using
9155 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9156 (@pxref{Project Files and Main Subprograms}).
9158 @item ^-U^/ALL_PROJECTS^
9159 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9160 When used without a project file or with one or several mains on the command
9161 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9162 on the command line, all sources of all project files are checked and compiled
9163 if not up to date, and libraries are rebuilt, if necessary.
9166 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9167 Verbose. Display the reason for all recompilations @command{gnatmake}
9168 decides are necessary, with the highest verbosity level.
9170 @item ^-vl^/LOW_VERBOSITY^
9171 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9172 Verbosity level Low. Display fewer lines than in verbosity Medium.
9174 @item ^-vm^/MEDIUM_VERBOSITY^
9175 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9176 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9178 @item ^-vh^/HIGH_VERBOSITY^
9179 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9180 Verbosity level High. Equivalent to ^-v^/REASONS^.
9182 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9183 Indicate the verbosity of the parsing of GNAT project files.
9184 @xref{Switches Related to Project Files}.
9186 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9187 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9188 Indicate that sources that are not part of any Project File may be compiled.
9189 Normally, when using Project Files, only sources that are part of a Project
9190 File may be compile. When this switch is used, a source outside of all Project
9191 Files may be compiled. The ALI file and the object file will be put in the
9192 object directory of the main Project. The compilation switches used will only
9193 be those specified on the command line. Even when
9194 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9195 command line need to be sources of a project file.
9197 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9198 Indicate that external variable @var{name} has the value @var{value}.
9199 The Project Manager will use this value for occurrences of
9200 @code{external(name)} when parsing the project file.
9201 @xref{Switches Related to Project Files}.
9204 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9205 No main subprogram. Bind and link the program even if the unit name
9206 given on the command line is a package name. The resulting executable
9207 will execute the elaboration routines of the package and its closure,
9208 then the finalization routines.
9213 @item @command{gcc} @asis{switches}
9215 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9216 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9219 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9220 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9221 automatically treated as a compiler switch, and passed on to all
9222 compilations that are carried out.
9227 Source and library search path switches:
9231 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9232 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9233 When looking for source files also look in directory @var{dir}.
9234 The order in which source files search is undertaken is
9235 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9237 @item ^-aL^/SKIP_MISSING=^@var{dir}
9238 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9239 Consider @var{dir} as being an externally provided Ada library.
9240 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9241 files have been located in directory @var{dir}. This allows you to have
9242 missing bodies for the units in @var{dir} and to ignore out of date bodies
9243 for the same units. You still need to specify
9244 the location of the specs for these units by using the switches
9245 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9246 or @option{^-I^/SEARCH=^@var{dir}}.
9247 Note: this switch is provided for compatibility with previous versions
9248 of @command{gnatmake}. The easier method of causing standard libraries
9249 to be excluded from consideration is to write-protect the corresponding
9252 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9253 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9254 When searching for library and object files, look in directory
9255 @var{dir}. The order in which library files are searched is described in
9256 @ref{Search Paths for gnatbind}.
9258 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9259 @cindex Search paths, for @command{gnatmake}
9260 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9261 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9262 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9264 @item ^-I^/SEARCH=^@var{dir}
9265 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9266 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9267 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9269 @item ^-I-^/NOCURRENT_DIRECTORY^
9270 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9271 @cindex Source files, suppressing search
9272 Do not look for source files in the directory containing the source
9273 file named in the command line.
9274 Do not look for ALI or object files in the directory
9275 where @command{gnatmake} was invoked.
9277 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9278 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9279 @cindex Linker libraries
9280 Add directory @var{dir} to the list of directories in which the linker
9281 will search for libraries. This is equivalent to
9282 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9284 Furthermore, under Windows, the sources pointed to by the libraries path
9285 set in the registry are not searched for.
9289 @cindex @option{-nostdinc} (@command{gnatmake})
9290 Do not look for source files in the system default directory.
9293 @cindex @option{-nostdlib} (@command{gnatmake})
9294 Do not look for library files in the system default directory.
9296 @item --RTS=@var{rts-path}
9297 @cindex @option{--RTS} (@command{gnatmake})
9298 Specifies the default location of the runtime library. GNAT looks for the
9300 in the following directories, and stops as soon as a valid runtime is found
9301 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9302 @file{ada_object_path} present):
9305 @item <current directory>/$rts_path
9307 @item <default-search-dir>/$rts_path
9309 @item <default-search-dir>/rts-$rts_path
9313 The selected path is handled like a normal RTS path.
9317 @node Mode Switches for gnatmake
9318 @section Mode Switches for @command{gnatmake}
9321 The mode switches (referred to as @code{mode_switches}) allow the
9322 inclusion of switches that are to be passed to the compiler itself, the
9323 binder or the linker. The effect of a mode switch is to cause all
9324 subsequent switches up to the end of the switch list, or up to the next
9325 mode switch, to be interpreted as switches to be passed on to the
9326 designated component of GNAT.
9330 @item -cargs @var{switches}
9331 @cindex @option{-cargs} (@command{gnatmake})
9332 Compiler switches. Here @var{switches} is a list of switches
9333 that are valid switches for @command{gcc}. They will be passed on to
9334 all compile steps performed by @command{gnatmake}.
9336 @item -bargs @var{switches}
9337 @cindex @option{-bargs} (@command{gnatmake})
9338 Binder switches. Here @var{switches} is a list of switches
9339 that are valid switches for @code{gnatbind}. They will be passed on to
9340 all bind steps performed by @command{gnatmake}.
9342 @item -largs @var{switches}
9343 @cindex @option{-largs} (@command{gnatmake})
9344 Linker switches. Here @var{switches} is a list of switches
9345 that are valid switches for @command{gnatlink}. They will be passed on to
9346 all link steps performed by @command{gnatmake}.
9348 @item -margs @var{switches}
9349 @cindex @option{-margs} (@command{gnatmake})
9350 Make switches. The switches are directly interpreted by @command{gnatmake},
9351 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9355 @node Notes on the Command Line
9356 @section Notes on the Command Line
9359 This section contains some additional useful notes on the operation
9360 of the @command{gnatmake} command.
9364 @cindex Recompilation, by @command{gnatmake}
9365 If @command{gnatmake} finds no ALI files, it recompiles the main program
9366 and all other units required by the main program.
9367 This means that @command{gnatmake}
9368 can be used for the initial compile, as well as during subsequent steps of
9369 the development cycle.
9372 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9373 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9374 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9378 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9379 is used to specify both source and
9380 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9381 instead if you just want to specify
9382 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9383 if you want to specify library paths
9387 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9388 This may conveniently be used to exclude standard libraries from
9389 consideration and in particular it means that the use of the
9390 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9391 unless @option{^-a^/ALL_FILES^} is also specified.
9394 @command{gnatmake} has been designed to make the use of Ada libraries
9395 particularly convenient. Assume you have an Ada library organized
9396 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9397 of your Ada compilation units,
9398 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9399 specs of these units, but no bodies. Then to compile a unit
9400 stored in @code{main.adb}, which uses this Ada library you would just type
9404 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9407 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9408 /SKIP_MISSING=@i{[OBJ_DIR]} main
9413 Using @command{gnatmake} along with the
9414 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9415 switch provides a mechanism for avoiding unnecessary recompilations. Using
9417 you can update the comments/format of your
9418 source files without having to recompile everything. Note, however, that
9419 adding or deleting lines in a source files may render its debugging
9420 info obsolete. If the file in question is a spec, the impact is rather
9421 limited, as that debugging info will only be useful during the
9422 elaboration phase of your program. For bodies the impact can be more
9423 significant. In all events, your debugger will warn you if a source file
9424 is more recent than the corresponding object, and alert you to the fact
9425 that the debugging information may be out of date.
9428 @node How gnatmake Works
9429 @section How @command{gnatmake} Works
9432 Generally @command{gnatmake} automatically performs all necessary
9433 recompilations and you don't need to worry about how it works. However,
9434 it may be useful to have some basic understanding of the @command{gnatmake}
9435 approach and in particular to understand how it uses the results of
9436 previous compilations without incorrectly depending on them.
9438 First a definition: an object file is considered @dfn{up to date} if the
9439 corresponding ALI file exists and if all the source files listed in the
9440 dependency section of this ALI file have time stamps matching those in
9441 the ALI file. This means that neither the source file itself nor any
9442 files that it depends on have been modified, and hence there is no need
9443 to recompile this file.
9445 @command{gnatmake} works by first checking if the specified main unit is up
9446 to date. If so, no compilations are required for the main unit. If not,
9447 @command{gnatmake} compiles the main program to build a new ALI file that
9448 reflects the latest sources. Then the ALI file of the main unit is
9449 examined to find all the source files on which the main program depends,
9450 and @command{gnatmake} recursively applies the above procedure on all these
9453 This process ensures that @command{gnatmake} only trusts the dependencies
9454 in an existing ALI file if they are known to be correct. Otherwise it
9455 always recompiles to determine a new, guaranteed accurate set of
9456 dependencies. As a result the program is compiled ``upside down'' from what may
9457 be more familiar as the required order of compilation in some other Ada
9458 systems. In particular, clients are compiled before the units on which
9459 they depend. The ability of GNAT to compile in any order is critical in
9460 allowing an order of compilation to be chosen that guarantees that
9461 @command{gnatmake} will recompute a correct set of new dependencies if
9464 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9465 imported by several of the executables, it will be recompiled at most once.
9467 Note: when using non-standard naming conventions
9468 (@pxref{Using Other File Names}), changing through a configuration pragmas
9469 file the version of a source and invoking @command{gnatmake} to recompile may
9470 have no effect, if the previous version of the source is still accessible
9471 by @command{gnatmake}. It may be necessary to use the switch
9472 ^-f^/FORCE_COMPILE^.
9474 @node Examples of gnatmake Usage
9475 @section Examples of @command{gnatmake} Usage
9478 @item gnatmake hello.adb
9479 Compile all files necessary to bind and link the main program
9480 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9481 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9483 @item gnatmake main1 main2 main3
9484 Compile all files necessary to bind and link the main programs
9485 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9486 (containing unit @code{Main2}) and @file{main3.adb}
9487 (containing unit @code{Main3}) and bind and link the resulting object files
9488 to generate three executable files @file{^main1^MAIN1.EXE^},
9489 @file{^main2^MAIN2.EXE^}
9490 and @file{^main3^MAIN3.EXE^}.
9493 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9497 @item gnatmake Main_Unit /QUIET
9498 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9499 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9501 Compile all files necessary to bind and link the main program unit
9502 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9503 be done with optimization level 2 and the order of elaboration will be
9504 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9505 displaying commands it is executing.
9508 @c *************************
9509 @node Improving Performance
9510 @chapter Improving Performance
9511 @cindex Improving performance
9514 This chapter presents several topics related to program performance.
9515 It first describes some of the tradeoffs that need to be considered
9516 and some of the techniques for making your program run faster.
9517 It then documents the @command{gnatelim} tool and unused subprogram/data
9518 elimination feature, which can reduce the size of program executables.
9520 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9521 driver (see @ref{The GNAT Driver and Project Files}).
9525 * Performance Considerations::
9526 * Text_IO Suggestions::
9527 * Reducing Size of Ada Executables with gnatelim::
9528 * Reducing Size of Executables with unused subprogram/data elimination::
9532 @c *****************************
9533 @node Performance Considerations
9534 @section Performance Considerations
9537 The GNAT system provides a number of options that allow a trade-off
9542 performance of the generated code
9545 speed of compilation
9548 minimization of dependences and recompilation
9551 the degree of run-time checking.
9555 The defaults (if no options are selected) aim at improving the speed
9556 of compilation and minimizing dependences, at the expense of performance
9557 of the generated code:
9564 no inlining of subprogram calls
9567 all run-time checks enabled except overflow and elaboration checks
9571 These options are suitable for most program development purposes. This
9572 chapter describes how you can modify these choices, and also provides
9573 some guidelines on debugging optimized code.
9576 * Controlling Run-Time Checks::
9577 * Use of Restrictions::
9578 * Optimization Levels::
9579 * Debugging Optimized Code::
9580 * Inlining of Subprograms::
9581 * Other Optimization Switches::
9582 * Optimization and Strict Aliasing::
9585 * Coverage Analysis::
9589 @node Controlling Run-Time Checks
9590 @subsection Controlling Run-Time Checks
9593 By default, GNAT generates all run-time checks, except integer overflow
9594 checks, stack overflow checks, and checks for access before elaboration on
9595 subprogram calls. The latter are not required in default mode, because all
9596 necessary checking is done at compile time.
9597 @cindex @option{-gnatp} (@command{gcc})
9598 @cindex @option{-gnato} (@command{gcc})
9599 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9600 be modified. @xref{Run-Time Checks}.
9602 Our experience is that the default is suitable for most development
9605 We treat integer overflow specially because these
9606 are quite expensive and in our experience are not as important as other
9607 run-time checks in the development process. Note that division by zero
9608 is not considered an overflow check, and divide by zero checks are
9609 generated where required by default.
9611 Elaboration checks are off by default, and also not needed by default, since
9612 GNAT uses a static elaboration analysis approach that avoids the need for
9613 run-time checking. This manual contains a full chapter discussing the issue
9614 of elaboration checks, and if the default is not satisfactory for your use,
9615 you should read this chapter.
9617 For validity checks, the minimal checks required by the Ada Reference
9618 Manual (for case statements and assignments to array elements) are on
9619 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9620 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9621 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9622 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9623 are also suppressed entirely if @option{-gnatp} is used.
9625 @cindex Overflow checks
9626 @cindex Checks, overflow
9629 @cindex pragma Suppress
9630 @cindex pragma Unsuppress
9631 Note that the setting of the switches controls the default setting of
9632 the checks. They may be modified using either @code{pragma Suppress} (to
9633 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9634 checks) in the program source.
9636 @node Use of Restrictions
9637 @subsection Use of Restrictions
9640 The use of pragma Restrictions allows you to control which features are
9641 permitted in your program. Apart from the obvious point that if you avoid
9642 relatively expensive features like finalization (enforceable by the use
9643 of pragma Restrictions (No_Finalization), the use of this pragma does not
9644 affect the generated code in most cases.
9646 One notable exception to this rule is that the possibility of task abort
9647 results in some distributed overhead, particularly if finalization or
9648 exception handlers are used. The reason is that certain sections of code
9649 have to be marked as non-abortable.
9651 If you use neither the @code{abort} statement, nor asynchronous transfer
9652 of control (@code{select @dots{} then abort}), then this distributed overhead
9653 is removed, which may have a general positive effect in improving
9654 overall performance. Especially code involving frequent use of tasking
9655 constructs and controlled types will show much improved performance.
9656 The relevant restrictions pragmas are
9658 @smallexample @c ada
9659 pragma Restrictions (No_Abort_Statements);
9660 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9664 It is recommended that these restriction pragmas be used if possible. Note
9665 that this also means that you can write code without worrying about the
9666 possibility of an immediate abort at any point.
9668 @node Optimization Levels
9669 @subsection Optimization Levels
9670 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9673 Without any optimization ^option,^qualifier,^
9674 the compiler's goal is to reduce the cost of
9675 compilation and to make debugging produce the expected results.
9676 Statements are independent: if you stop the program with a breakpoint between
9677 statements, you can then assign a new value to any variable or change
9678 the program counter to any other statement in the subprogram and get exactly
9679 the results you would expect from the source code.
9681 Turning on optimization makes the compiler attempt to improve the
9682 performance and/or code size at the expense of compilation time and
9683 possibly the ability to debug the program.
9686 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9687 the last such option is the one that is effective.
9690 The default is optimization off. This results in the fastest compile
9691 times, but GNAT makes absolutely no attempt to optimize, and the
9692 generated programs are considerably larger and slower than when
9693 optimization is enabled. You can use the
9695 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9696 @option{-O2}, @option{-O3}, and @option{-Os})
9699 @code{OPTIMIZE} qualifier
9701 to @command{gcc} to control the optimization level:
9704 @item ^-O0^/OPTIMIZE=NONE^
9705 No optimization (the default);
9706 generates unoptimized code but has
9707 the fastest compilation time.
9709 Note that many other compilers do fairly extensive optimization
9710 even if ``no optimization'' is specified. With gcc, it is
9711 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9712 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9713 really does mean no optimization at all. This difference between
9714 gcc and other compilers should be kept in mind when doing
9715 performance comparisons.
9717 @item ^-O1^/OPTIMIZE=SOME^
9718 Moderate optimization;
9719 optimizes reasonably well but does not
9720 degrade compilation time significantly.
9722 @item ^-O2^/OPTIMIZE=ALL^
9724 @itemx /OPTIMIZE=DEVELOPMENT
9727 generates highly optimized code and has
9728 the slowest compilation time.
9730 @item ^-O3^/OPTIMIZE=INLINING^
9731 Full optimization as in @option{-O2},
9732 and also attempts automatic inlining of small
9733 subprograms within a unit (@pxref{Inlining of Subprograms}).
9735 @item ^-Os^/OPTIMIZE=SPACE^
9736 Optimize space usage of resulting program.
9740 Higher optimization levels perform more global transformations on the
9741 program and apply more expensive analysis algorithms in order to generate
9742 faster and more compact code. The price in compilation time, and the
9743 resulting improvement in execution time,
9744 both depend on the particular application and the hardware environment.
9745 You should experiment to find the best level for your application.
9747 Since the precise set of optimizations done at each level will vary from
9748 release to release (and sometime from target to target), it is best to think
9749 of the optimization settings in general terms.
9750 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
9751 the GNU Compiler Collection (GCC)}, for details about
9752 ^the @option{-O} settings and a number of @option{-f} options that^how to^
9753 individually enable or disable specific optimizations.
9755 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
9756 been tested extensively at all optimization levels. There are some bugs
9757 which appear only with optimization turned on, but there have also been
9758 bugs which show up only in @emph{unoptimized} code. Selecting a lower
9759 level of optimization does not improve the reliability of the code
9760 generator, which in practice is highly reliable at all optimization
9763 Note regarding the use of @option{-O3}: The use of this optimization level
9764 is generally discouraged with GNAT, since it often results in larger
9765 executables which run more slowly. See further discussion of this point
9766 in @ref{Inlining of Subprograms}.
9768 @node Debugging Optimized Code
9769 @subsection Debugging Optimized Code
9770 @cindex Debugging optimized code
9771 @cindex Optimization and debugging
9774 Although it is possible to do a reasonable amount of debugging at
9776 nonzero optimization levels,
9777 the higher the level the more likely that
9780 @option{/OPTIMIZE} settings other than @code{NONE},
9781 such settings will make it more likely that
9783 source-level constructs will have been eliminated by optimization.
9784 For example, if a loop is strength-reduced, the loop
9785 control variable may be completely eliminated and thus cannot be
9786 displayed in the debugger.
9787 This can only happen at @option{-O2} or @option{-O3}.
9788 Explicit temporary variables that you code might be eliminated at
9789 ^level^setting^ @option{-O1} or higher.
9791 The use of the @option{^-g^/DEBUG^} switch,
9792 @cindex @option{^-g^/DEBUG^} (@command{gcc})
9793 which is needed for source-level debugging,
9794 affects the size of the program executable on disk,
9795 and indeed the debugging information can be quite large.
9796 However, it has no effect on the generated code (and thus does not
9797 degrade performance)
9799 Since the compiler generates debugging tables for a compilation unit before
9800 it performs optimizations, the optimizing transformations may invalidate some
9801 of the debugging data. You therefore need to anticipate certain
9802 anomalous situations that may arise while debugging optimized code.
9803 These are the most common cases:
9807 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
9809 the PC bouncing back and forth in the code. This may result from any of
9810 the following optimizations:
9814 @i{Common subexpression elimination:} using a single instance of code for a
9815 quantity that the source computes several times. As a result you
9816 may not be able to stop on what looks like a statement.
9819 @i{Invariant code motion:} moving an expression that does not change within a
9820 loop, to the beginning of the loop.
9823 @i{Instruction scheduling:} moving instructions so as to
9824 overlap loads and stores (typically) with other code, or in
9825 general to move computations of values closer to their uses. Often
9826 this causes you to pass an assignment statement without the assignment
9827 happening and then later bounce back to the statement when the
9828 value is actually needed. Placing a breakpoint on a line of code
9829 and then stepping over it may, therefore, not always cause all the
9830 expected side-effects.
9834 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
9835 two identical pieces of code are merged and the program counter suddenly
9836 jumps to a statement that is not supposed to be executed, simply because
9837 it (and the code following) translates to the same thing as the code
9838 that @emph{was} supposed to be executed. This effect is typically seen in
9839 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9840 a @code{break} in a C @code{^switch^switch^} statement.
9843 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9844 There are various reasons for this effect:
9848 In a subprogram prologue, a parameter may not yet have been moved to its
9852 A variable may be dead, and its register re-used. This is
9853 probably the most common cause.
9856 As mentioned above, the assignment of a value to a variable may
9860 A variable may be eliminated entirely by value propagation or
9861 other means. In this case, GCC may incorrectly generate debugging
9862 information for the variable
9866 In general, when an unexpected value appears for a local variable or parameter
9867 you should first ascertain if that value was actually computed by
9868 your program, as opposed to being incorrectly reported by the debugger.
9870 array elements in an object designated by an access value
9871 are generally less of a problem, once you have ascertained that the access
9873 Typically, this means checking variables in the preceding code and in the
9874 calling subprogram to verify that the value observed is explainable from other
9875 values (one must apply the procedure recursively to those
9876 other values); or re-running the code and stopping a little earlier
9877 (perhaps before the call) and stepping to better see how the variable obtained
9878 the value in question; or continuing to step @emph{from} the point of the
9879 strange value to see if code motion had simply moved the variable's
9884 In light of such anomalies, a recommended technique is to use @option{-O0}
9885 early in the software development cycle, when extensive debugging capabilities
9886 are most needed, and then move to @option{-O1} and later @option{-O2} as
9887 the debugger becomes less critical.
9888 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9889 a release management issue.
9891 Note that if you use @option{-g} you can then use the @command{strip} program
9892 on the resulting executable,
9893 which removes both debugging information and global symbols.
9896 @node Inlining of Subprograms
9897 @subsection Inlining of Subprograms
9900 A call to a subprogram in the current unit is inlined if all the
9901 following conditions are met:
9905 The optimization level is at least @option{-O1}.
9908 The called subprogram is suitable for inlining: It must be small enough
9909 and not contain something that @command{gcc} cannot support in inlined
9913 @cindex pragma Inline
9915 Either @code{pragma Inline} applies to the subprogram, or it is local
9916 to the unit and called once from within it, or it is small and automatic
9917 inlining (optimization level @option{-O3}) is specified.
9921 Calls to subprograms in @code{with}'ed units are normally not inlined.
9922 To achieve actual inlining (that is, replacement of the call by the code
9923 in the body of the subprogram), the following conditions must all be true.
9927 The optimization level is at least @option{-O1}.
9930 The called subprogram is suitable for inlining: It must be small enough
9931 and not contain something that @command{gcc} cannot support in inlined
9935 The call appears in a body (not in a package spec).
9938 There is a @code{pragma Inline} for the subprogram.
9941 @cindex @option{-gnatn} (@command{gcc})
9942 The @option{^-gnatn^/INLINE^} switch
9943 is used in the @command{gcc} command line
9946 Even if all these conditions are met, it may not be possible for
9947 the compiler to inline the call, due to the length of the body,
9948 or features in the body that make it impossible for the compiler
9951 Note that specifying the @option{-gnatn} switch causes additional
9952 compilation dependencies. Consider the following:
9954 @smallexample @c ada
9974 With the default behavior (no @option{-gnatn} switch specified), the
9975 compilation of the @code{Main} procedure depends only on its own source,
9976 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
9977 means that editing the body of @code{R} does not require recompiling
9980 On the other hand, the call @code{R.Q} is not inlined under these
9981 circumstances. If the @option{-gnatn} switch is present when @code{Main}
9982 is compiled, the call will be inlined if the body of @code{Q} is small
9983 enough, but now @code{Main} depends on the body of @code{R} in
9984 @file{r.adb} as well as on the spec. This means that if this body is edited,
9985 the main program must be recompiled. Note that this extra dependency
9986 occurs whether or not the call is in fact inlined by @command{gcc}.
9988 The use of front end inlining with @option{-gnatN} generates similar
9989 additional dependencies.
9991 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
9992 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
9993 can be used to prevent
9994 all inlining. This switch overrides all other conditions and ensures
9995 that no inlining occurs. The extra dependences resulting from
9996 @option{-gnatn} will still be active, even if
9997 this switch is used to suppress the resulting inlining actions.
9999 @cindex @option{-fno-inline-functions} (@command{gcc})
10000 Note: The @option{-fno-inline-functions} switch can be used to prevent
10001 automatic inlining of small subprograms if @option{-O3} is used.
10003 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10004 Note: The @option{-fno-inline-functions-called-once} switch
10005 can be used to prevent inlining of subprograms local to the unit
10006 and called once from within it if @option{-O1} is used.
10008 Note regarding the use of @option{-O3}: There is no difference in inlining
10009 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10010 pragma @code{Inline} assuming the use of @option{-gnatn}
10011 or @option{-gnatN} (the switches that activate inlining). If you have used
10012 pragma @code{Inline} in appropriate cases, then it is usually much better
10013 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10014 in this case only has the effect of inlining subprograms you did not
10015 think should be inlined. We often find that the use of @option{-O3} slows
10016 down code by performing excessive inlining, leading to increased instruction
10017 cache pressure from the increased code size. So the bottom line here is
10018 that you should not automatically assume that @option{-O3} is better than
10019 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10020 it actually improves performance.
10022 @node Other Optimization Switches
10023 @subsection Other Optimization Switches
10024 @cindex Optimization Switches
10026 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10027 @command{gcc} optimization switches are potentially usable. These switches
10028 have not been extensively tested with GNAT but can generally be expected
10029 to work. Examples of switches in this category are
10030 @option{-funroll-loops} and
10031 the various target-specific @option{-m} options (in particular, it has been
10032 observed that @option{-march=pentium4} can significantly improve performance
10033 on appropriate machines). For full details of these switches, see
10034 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10035 the GNU Compiler Collection (GCC)}.
10037 @node Optimization and Strict Aliasing
10038 @subsection Optimization and Strict Aliasing
10040 @cindex Strict Aliasing
10041 @cindex No_Strict_Aliasing
10044 The strong typing capabilities of Ada allow an optimizer to generate
10045 efficient code in situations where other languages would be forced to
10046 make worst case assumptions preventing such optimizations. Consider
10047 the following example:
10049 @smallexample @c ada
10052 type Int1 is new Integer;
10053 type Int2 is new Integer;
10054 type Int1A is access Int1;
10055 type Int2A is access Int2;
10062 for J in Data'Range loop
10063 if Data (J) = Int1V.all then
10064 Int2V.all := Int2V.all + 1;
10073 In this example, since the variable @code{Int1V} can only access objects
10074 of type @code{Int1}, and @code{Int2V} can only access objects of type
10075 @code{Int2}, there is no possibility that the assignment to
10076 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10077 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10078 for all iterations of the loop and avoid the extra memory reference
10079 required to dereference it each time through the loop.
10081 This kind of optimization, called strict aliasing analysis, is
10082 triggered by specifying an optimization level of @option{-O2} or
10083 higher and allows @code{GNAT} to generate more efficient code
10084 when access values are involved.
10086 However, although this optimization is always correct in terms of
10087 the formal semantics of the Ada Reference Manual, difficulties can
10088 arise if features like @code{Unchecked_Conversion} are used to break
10089 the typing system. Consider the following complete program example:
10091 @smallexample @c ada
10094 type int1 is new integer;
10095 type int2 is new integer;
10096 type a1 is access int1;
10097 type a2 is access int2;
10102 function to_a2 (Input : a1) return a2;
10105 with Unchecked_Conversion;
10107 function to_a2 (Input : a1) return a2 is
10109 new Unchecked_Conversion (a1, a2);
10111 return to_a2u (Input);
10117 with Text_IO; use Text_IO;
10119 v1 : a1 := new int1;
10120 v2 : a2 := to_a2 (v1);
10124 put_line (int1'image (v1.all));
10130 This program prints out 0 in @option{-O0} or @option{-O1}
10131 mode, but it prints out 1 in @option{-O2} mode. That's
10132 because in strict aliasing mode, the compiler can and
10133 does assume that the assignment to @code{v2.all} could not
10134 affect the value of @code{v1.all}, since different types
10137 This behavior is not a case of non-conformance with the standard, since
10138 the Ada RM specifies that an unchecked conversion where the resulting
10139 bit pattern is not a correct value of the target type can result in an
10140 abnormal value and attempting to reference an abnormal value makes the
10141 execution of a program erroneous. That's the case here since the result
10142 does not point to an object of type @code{int2}. This means that the
10143 effect is entirely unpredictable.
10145 However, although that explanation may satisfy a language
10146 lawyer, in practice an applications programmer expects an
10147 unchecked conversion involving pointers to create true
10148 aliases and the behavior of printing 1 seems plain wrong.
10149 In this case, the strict aliasing optimization is unwelcome.
10151 Indeed the compiler recognizes this possibility, and the
10152 unchecked conversion generates a warning:
10155 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10156 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10157 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10161 Unfortunately the problem is recognized when compiling the body of
10162 package @code{p2}, but the actual "bad" code is generated while
10163 compiling the body of @code{m} and this latter compilation does not see
10164 the suspicious @code{Unchecked_Conversion}.
10166 As implied by the warning message, there are approaches you can use to
10167 avoid the unwanted strict aliasing optimization in a case like this.
10169 One possibility is to simply avoid the use of @option{-O2}, but
10170 that is a bit drastic, since it throws away a number of useful
10171 optimizations that do not involve strict aliasing assumptions.
10173 A less drastic approach is to compile the program using the
10174 option @option{-fno-strict-aliasing}. Actually it is only the
10175 unit containing the dereferencing of the suspicious pointer
10176 that needs to be compiled. So in this case, if we compile
10177 unit @code{m} with this switch, then we get the expected
10178 value of zero printed. Analyzing which units might need
10179 the switch can be painful, so a more reasonable approach
10180 is to compile the entire program with options @option{-O2}
10181 and @option{-fno-strict-aliasing}. If the performance is
10182 satisfactory with this combination of options, then the
10183 advantage is that the entire issue of possible "wrong"
10184 optimization due to strict aliasing is avoided.
10186 To avoid the use of compiler switches, the configuration
10187 pragma @code{No_Strict_Aliasing} with no parameters may be
10188 used to specify that for all access types, the strict
10189 aliasing optimization should be suppressed.
10191 However, these approaches are still overkill, in that they causes
10192 all manipulations of all access values to be deoptimized. A more
10193 refined approach is to concentrate attention on the specific
10194 access type identified as problematic.
10196 First, if a careful analysis of uses of the pointer shows
10197 that there are no possible problematic references, then
10198 the warning can be suppressed by bracketing the
10199 instantiation of @code{Unchecked_Conversion} to turn
10202 @smallexample @c ada
10203 pragma Warnings (Off);
10205 new Unchecked_Conversion (a1, a2);
10206 pragma Warnings (On);
10210 Of course that approach is not appropriate for this particular
10211 example, since indeed there is a problematic reference. In this
10212 case we can take one of two other approaches.
10214 The first possibility is to move the instantiation of unchecked
10215 conversion to the unit in which the type is declared. In
10216 this example, we would move the instantiation of
10217 @code{Unchecked_Conversion} from the body of package
10218 @code{p2} to the spec of package @code{p1}. Now the
10219 warning disappears. That's because any use of the
10220 access type knows there is a suspicious unchecked
10221 conversion, and the strict aliasing optimization
10222 is automatically suppressed for the type.
10224 If it is not practical to move the unchecked conversion to the same unit
10225 in which the destination access type is declared (perhaps because the
10226 source type is not visible in that unit), you may use pragma
10227 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10228 same declarative sequence as the declaration of the access type:
10230 @smallexample @c ada
10231 type a2 is access int2;
10232 pragma No_Strict_Aliasing (a2);
10236 Here again, the compiler now knows that the strict aliasing optimization
10237 should be suppressed for any reference to type @code{a2} and the
10238 expected behavior is obtained.
10240 Finally, note that although the compiler can generate warnings for
10241 simple cases of unchecked conversions, there are tricker and more
10242 indirect ways of creating type incorrect aliases which the compiler
10243 cannot detect. Examples are the use of address overlays and unchecked
10244 conversions involving composite types containing access types as
10245 components. In such cases, no warnings are generated, but there can
10246 still be aliasing problems. One safe coding practice is to forbid the
10247 use of address clauses for type overlaying, and to allow unchecked
10248 conversion only for primitive types. This is not really a significant
10249 restriction since any possible desired effect can be achieved by
10250 unchecked conversion of access values.
10253 @node Coverage Analysis
10254 @subsection Coverage Analysis
10257 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10258 the user to determine the distribution of execution time across a program,
10259 @pxref{Profiling} for details of usage.
10263 @node Text_IO Suggestions
10264 @section @code{Text_IO} Suggestions
10265 @cindex @code{Text_IO} and performance
10268 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10269 the requirement of maintaining page and line counts. If performance
10270 is critical, a recommendation is to use @code{Stream_IO} instead of
10271 @code{Text_IO} for volume output, since this package has less overhead.
10273 If @code{Text_IO} must be used, note that by default output to the standard
10274 output and standard error files is unbuffered (this provides better
10275 behavior when output statements are used for debugging, or if the
10276 progress of a program is observed by tracking the output, e.g. by
10277 using the Unix @command{tail -f} command to watch redirected output.
10279 If you are generating large volumes of output with @code{Text_IO} and
10280 performance is an important factor, use a designated file instead
10281 of the standard output file, or change the standard output file to
10282 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10286 @node Reducing Size of Ada Executables with gnatelim
10287 @section Reducing Size of Ada Executables with @code{gnatelim}
10291 This section describes @command{gnatelim}, a tool which detects unused
10292 subprograms and helps the compiler to create a smaller executable for your
10297 * Running gnatelim::
10298 * Correcting the List of Eliminate Pragmas::
10299 * Making Your Executables Smaller::
10300 * Summary of the gnatelim Usage Cycle::
10303 @node About gnatelim
10304 @subsection About @code{gnatelim}
10307 When a program shares a set of Ada
10308 packages with other programs, it may happen that this program uses
10309 only a fraction of the subprograms defined in these packages. The code
10310 created for these unused subprograms increases the size of the executable.
10312 @code{gnatelim} tracks unused subprograms in an Ada program and
10313 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10314 subprograms that are declared but never called. By placing the list of
10315 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10316 recompiling your program, you may decrease the size of its executable,
10317 because the compiler will not generate the code for 'eliminated' subprograms.
10318 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10319 information about this pragma.
10321 @code{gnatelim} needs as its input data the name of the main subprogram
10322 and a bind file for a main subprogram.
10324 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10325 the main subprogram. @code{gnatelim} can work with both Ada and C
10326 bind files; when both are present, it uses the Ada bind file.
10327 The following commands will build the program and create the bind file:
10330 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10331 $ gnatbind main_prog
10334 Note that @code{gnatelim} needs neither object nor ALI files.
10336 @node Running gnatelim
10337 @subsection Running @code{gnatelim}
10340 @code{gnatelim} has the following command-line interface:
10343 $ gnatelim @ovar{options} name
10347 @code{name} should be a name of a source file that contains the main subprogram
10348 of a program (partition).
10350 @code{gnatelim} has the following switches:
10355 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10356 Quiet mode: by default @code{gnatelim} outputs to the standard error
10357 stream the number of program units left to be processed. This option turns
10360 @item ^-v^/VERBOSE^
10361 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10362 Verbose mode: @code{gnatelim} version information is printed as Ada
10363 comments to the standard output stream. Also, in addition to the number of
10364 program units left @code{gnatelim} will output the name of the current unit
10368 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10369 Also look for subprograms from the GNAT run time that can be eliminated. Note
10370 that when @file{gnat.adc} is produced using this switch, the entire program
10371 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10373 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10374 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10375 When looking for source files also look in directory @var{dir}. Specifying
10376 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10377 sources in the current directory.
10379 @item ^-b^/BIND_FILE=^@var{bind_file}
10380 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10381 Specifies @var{bind_file} as the bind file to process. If not set, the name
10382 of the bind file is computed from the full expanded Ada name
10383 of a main subprogram.
10385 @item ^-C^/CONFIG_FILE=^@var{config_file}
10386 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10387 Specifies a file @var{config_file} that contains configuration pragmas. The
10388 file must be specified with full path.
10390 @item ^--GCC^/COMPILER^=@var{compiler_name}
10391 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10392 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10393 available on the path.
10395 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10396 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10397 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10398 available on the path.
10402 @code{gnatelim} sends its output to the standard output stream, and all the
10403 tracing and debug information is sent to the standard error stream.
10404 In order to produce a proper GNAT configuration file
10405 @file{gnat.adc}, redirection must be used:
10409 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10412 $ gnatelim main_prog.adb > gnat.adc
10421 $ gnatelim main_prog.adb >> gnat.adc
10425 in order to append the @code{gnatelim} output to the existing contents of
10429 @node Correcting the List of Eliminate Pragmas
10430 @subsection Correcting the List of Eliminate Pragmas
10433 In some rare cases @code{gnatelim} may try to eliminate
10434 subprograms that are actually called in the program. In this case, the
10435 compiler will generate an error message of the form:
10438 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10442 You will need to manually remove the wrong @code{Eliminate} pragmas from
10443 the @file{gnat.adc} file. You should recompile your program
10444 from scratch after that, because you need a consistent @file{gnat.adc} file
10445 during the entire compilation.
10447 @node Making Your Executables Smaller
10448 @subsection Making Your Executables Smaller
10451 In order to get a smaller executable for your program you now have to
10452 recompile the program completely with the new @file{gnat.adc} file
10453 created by @code{gnatelim} in your current directory:
10456 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10460 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10461 recompile everything
10462 with the set of pragmas @code{Eliminate} that you have obtained with
10463 @command{gnatelim}).
10465 Be aware that the set of @code{Eliminate} pragmas is specific to each
10466 program. It is not recommended to merge sets of @code{Eliminate}
10467 pragmas created for different programs in one @file{gnat.adc} file.
10469 @node Summary of the gnatelim Usage Cycle
10470 @subsection Summary of the gnatelim Usage Cycle
10473 Here is a quick summary of the steps to be taken in order to reduce
10474 the size of your executables with @code{gnatelim}. You may use
10475 other GNAT options to control the optimization level,
10476 to produce the debugging information, to set search path, etc.
10480 Produce a bind file
10483 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10484 $ gnatbind main_prog
10488 Generate a list of @code{Eliminate} pragmas
10491 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10494 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10499 Recompile the application
10502 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10507 @node Reducing Size of Executables with unused subprogram/data elimination
10508 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10509 @findex unused subprogram/data elimination
10512 This section describes how you can eliminate unused subprograms and data from
10513 your executable just by setting options at compilation time.
10516 * About unused subprogram/data elimination::
10517 * Compilation options::
10518 * Example of unused subprogram/data elimination::
10521 @node About unused subprogram/data elimination
10522 @subsection About unused subprogram/data elimination
10525 By default, an executable contains all code and data of its composing objects
10526 (directly linked or coming from statically linked libraries), even data or code
10527 never used by this executable.
10529 This feature will allow you to eliminate such unused code from your
10530 executable, making it smaller (in disk and in memory).
10532 This functionality is available on all Linux platforms except for the IA-64
10533 architecture and on all cross platforms using the ELF binary file format.
10534 In both cases GNU binutils version 2.16 or later are required to enable it.
10536 @node Compilation options
10537 @subsection Compilation options
10540 The operation of eliminating the unused code and data from the final executable
10541 is directly performed by the linker.
10543 In order to do this, it has to work with objects compiled with the
10545 @option{-ffunction-sections} @option{-fdata-sections}.
10546 @cindex @option{-ffunction-sections} (@command{gcc})
10547 @cindex @option{-fdata-sections} (@command{gcc})
10548 These options are usable with C and Ada files.
10549 They will place respectively each
10550 function or data in a separate section in the resulting object file.
10552 Once the objects and static libraries are created with these options, the
10553 linker can perform the dead code elimination. You can do this by setting
10554 the @option{-Wl,--gc-sections} option to gcc command or in the
10555 @option{-largs} section of @command{gnatmake}. This will perform a
10556 garbage collection of code and data never referenced.
10558 If the linker performs a partial link (@option{-r} ld linker option), then you
10559 will need to provide one or several entry point using the
10560 @option{-e} / @option{--entry} ld option.
10562 Note that objects compiled without the @option{-ffunction-sections} and
10563 @option{-fdata-sections} options can still be linked with the executable.
10564 However, no dead code elimination will be performed on those objects (they will
10567 The GNAT static library is now compiled with -ffunction-sections and
10568 -fdata-sections on some platforms. This allows you to eliminate the unused code
10569 and data of the GNAT library from your executable.
10571 @node Example of unused subprogram/data elimination
10572 @subsection Example of unused subprogram/data elimination
10575 Here is a simple example:
10577 @smallexample @c ada
10586 Used_Data : Integer;
10587 Unused_Data : Integer;
10589 procedure Used (Data : Integer);
10590 procedure Unused (Data : Integer);
10593 package body Aux is
10594 procedure Used (Data : Integer) is
10599 procedure Unused (Data : Integer) is
10601 Unused_Data := Data;
10607 @code{Unused} and @code{Unused_Data} are never referenced in this code
10608 excerpt, and hence they may be safely removed from the final executable.
10613 $ nm test | grep used
10614 020015f0 T aux__unused
10615 02005d88 B aux__unused_data
10616 020015cc T aux__used
10617 02005d84 B aux__used_data
10619 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10620 -largs -Wl,--gc-sections
10622 $ nm test | grep used
10623 02005350 T aux__used
10624 0201ffe0 B aux__used_data
10628 It can be observed that the procedure @code{Unused} and the object
10629 @code{Unused_Data} are removed by the linker when using the
10630 appropriate options.
10632 @c ********************************
10633 @node Renaming Files Using gnatchop
10634 @chapter Renaming Files Using @code{gnatchop}
10638 This chapter discusses how to handle files with multiple units by using
10639 the @code{gnatchop} utility. This utility is also useful in renaming
10640 files to meet the standard GNAT default file naming conventions.
10643 * Handling Files with Multiple Units::
10644 * Operating gnatchop in Compilation Mode::
10645 * Command Line for gnatchop::
10646 * Switches for gnatchop::
10647 * Examples of gnatchop Usage::
10650 @node Handling Files with Multiple Units
10651 @section Handling Files with Multiple Units
10654 The basic compilation model of GNAT requires that a file submitted to the
10655 compiler have only one unit and there be a strict correspondence
10656 between the file name and the unit name.
10658 The @code{gnatchop} utility allows both of these rules to be relaxed,
10659 allowing GNAT to process files which contain multiple compilation units
10660 and files with arbitrary file names. @code{gnatchop}
10661 reads the specified file and generates one or more output files,
10662 containing one unit per file. The unit and the file name correspond,
10663 as required by GNAT.
10665 If you want to permanently restructure a set of ``foreign'' files so that
10666 they match the GNAT rules, and do the remaining development using the
10667 GNAT structure, you can simply use @command{gnatchop} once, generate the
10668 new set of files and work with them from that point on.
10670 Alternatively, if you want to keep your files in the ``foreign'' format,
10671 perhaps to maintain compatibility with some other Ada compilation
10672 system, you can set up a procedure where you use @command{gnatchop} each
10673 time you compile, regarding the source files that it writes as temporary
10674 files that you throw away.
10676 @node Operating gnatchop in Compilation Mode
10677 @section Operating gnatchop in Compilation Mode
10680 The basic function of @code{gnatchop} is to take a file with multiple units
10681 and split it into separate files. The boundary between files is reasonably
10682 clear, except for the issue of comments and pragmas. In default mode, the
10683 rule is that any pragmas between units belong to the previous unit, except
10684 that configuration pragmas always belong to the following unit. Any comments
10685 belong to the following unit. These rules
10686 almost always result in the right choice of
10687 the split point without needing to mark it explicitly and most users will
10688 find this default to be what they want. In this default mode it is incorrect to
10689 submit a file containing only configuration pragmas, or one that ends in
10690 configuration pragmas, to @code{gnatchop}.
10692 However, using a special option to activate ``compilation mode'',
10694 can perform another function, which is to provide exactly the semantics
10695 required by the RM for handling of configuration pragmas in a compilation.
10696 In the absence of configuration pragmas (at the main file level), this
10697 option has no effect, but it causes such configuration pragmas to be handled
10698 in a quite different manner.
10700 First, in compilation mode, if @code{gnatchop} is given a file that consists of
10701 only configuration pragmas, then this file is appended to the
10702 @file{gnat.adc} file in the current directory. This behavior provides
10703 the required behavior described in the RM for the actions to be taken
10704 on submitting such a file to the compiler, namely that these pragmas
10705 should apply to all subsequent compilations in the same compilation
10706 environment. Using GNAT, the current directory, possibly containing a
10707 @file{gnat.adc} file is the representation
10708 of a compilation environment. For more information on the
10709 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
10711 Second, in compilation mode, if @code{gnatchop}
10712 is given a file that starts with
10713 configuration pragmas, and contains one or more units, then these
10714 configuration pragmas are prepended to each of the chopped files. This
10715 behavior provides the required behavior described in the RM for the
10716 actions to be taken on compiling such a file, namely that the pragmas
10717 apply to all units in the compilation, but not to subsequently compiled
10720 Finally, if configuration pragmas appear between units, they are appended
10721 to the previous unit. This results in the previous unit being illegal,
10722 since the compiler does not accept configuration pragmas that follow
10723 a unit. This provides the required RM behavior that forbids configuration
10724 pragmas other than those preceding the first compilation unit of a
10727 For most purposes, @code{gnatchop} will be used in default mode. The
10728 compilation mode described above is used only if you need exactly
10729 accurate behavior with respect to compilations, and you have files
10730 that contain multiple units and configuration pragmas. In this
10731 circumstance the use of @code{gnatchop} with the compilation mode
10732 switch provides the required behavior, and is for example the mode
10733 in which GNAT processes the ACVC tests.
10735 @node Command Line for gnatchop
10736 @section Command Line for @code{gnatchop}
10739 The @code{gnatchop} command has the form:
10742 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
10747 The only required argument is the file name of the file to be chopped.
10748 There are no restrictions on the form of this file name. The file itself
10749 contains one or more Ada units, in normal GNAT format, concatenated
10750 together. As shown, more than one file may be presented to be chopped.
10752 When run in default mode, @code{gnatchop} generates one output file in
10753 the current directory for each unit in each of the files.
10755 @var{directory}, if specified, gives the name of the directory to which
10756 the output files will be written. If it is not specified, all files are
10757 written to the current directory.
10759 For example, given a
10760 file called @file{hellofiles} containing
10762 @smallexample @c ada
10767 with Text_IO; use Text_IO;
10770 Put_Line ("Hello");
10780 $ gnatchop ^hellofiles^HELLOFILES.^
10784 generates two files in the current directory, one called
10785 @file{hello.ads} containing the single line that is the procedure spec,
10786 and the other called @file{hello.adb} containing the remaining text. The
10787 original file is not affected. The generated files can be compiled in
10791 When gnatchop is invoked on a file that is empty or that contains only empty
10792 lines and/or comments, gnatchop will not fail, but will not produce any
10795 For example, given a
10796 file called @file{toto.txt} containing
10798 @smallexample @c ada
10810 $ gnatchop ^toto.txt^TOT.TXT^
10814 will not produce any new file and will result in the following warnings:
10817 toto.txt:1:01: warning: empty file, contains no compilation units
10818 no compilation units found
10819 no source files written
10822 @node Switches for gnatchop
10823 @section Switches for @code{gnatchop}
10826 @command{gnatchop} recognizes the following switches:
10832 @cindex @option{--version} @command{gnatchop}
10833 Display Copyright and version, then exit disregarding all other options.
10836 @cindex @option{--help} @command{gnatchop}
10837 If @option{--version} was not used, display usage, then exit disregarding
10840 @item ^-c^/COMPILATION^
10841 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
10842 Causes @code{gnatchop} to operate in compilation mode, in which
10843 configuration pragmas are handled according to strict RM rules. See
10844 previous section for a full description of this mode.
10847 @item -gnat@var{xxx}
10848 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
10849 used to parse the given file. Not all @var{xxx} options make sense,
10850 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
10851 process a source file that uses Latin-2 coding for identifiers.
10855 Causes @code{gnatchop} to generate a brief help summary to the standard
10856 output file showing usage information.
10858 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
10859 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
10860 Limit generated file names to the specified number @code{mm}
10862 This is useful if the
10863 resulting set of files is required to be interoperable with systems
10864 which limit the length of file names.
10866 If no value is given, or
10867 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
10868 a default of 39, suitable for OpenVMS Alpha
10869 Systems, is assumed
10872 No space is allowed between the @option{-k} and the numeric value. The numeric
10873 value may be omitted in which case a default of @option{-k8},
10875 with DOS-like file systems, is used. If no @option{-k} switch
10877 there is no limit on the length of file names.
10880 @item ^-p^/PRESERVE^
10881 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
10882 Causes the file ^modification^creation^ time stamp of the input file to be
10883 preserved and used for the time stamp of the output file(s). This may be
10884 useful for preserving coherency of time stamps in an environment where
10885 @code{gnatchop} is used as part of a standard build process.
10888 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
10889 Causes output of informational messages indicating the set of generated
10890 files to be suppressed. Warnings and error messages are unaffected.
10892 @item ^-r^/REFERENCE^
10893 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
10894 @findex Source_Reference
10895 Generate @code{Source_Reference} pragmas. Use this switch if the output
10896 files are regarded as temporary and development is to be done in terms
10897 of the original unchopped file. This switch causes
10898 @code{Source_Reference} pragmas to be inserted into each of the
10899 generated files to refers back to the original file name and line number.
10900 The result is that all error messages refer back to the original
10902 In addition, the debugging information placed into the object file (when
10903 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
10905 also refers back to this original file so that tools like profilers and
10906 debuggers will give information in terms of the original unchopped file.
10908 If the original file to be chopped itself contains
10909 a @code{Source_Reference}
10910 pragma referencing a third file, then gnatchop respects
10911 this pragma, and the generated @code{Source_Reference} pragmas
10912 in the chopped file refer to the original file, with appropriate
10913 line numbers. This is particularly useful when @code{gnatchop}
10914 is used in conjunction with @code{gnatprep} to compile files that
10915 contain preprocessing statements and multiple units.
10917 @item ^-v^/VERBOSE^
10918 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
10919 Causes @code{gnatchop} to operate in verbose mode. The version
10920 number and copyright notice are output, as well as exact copies of
10921 the gnat1 commands spawned to obtain the chop control information.
10923 @item ^-w^/OVERWRITE^
10924 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
10925 Overwrite existing file names. Normally @code{gnatchop} regards it as a
10926 fatal error if there is already a file with the same name as a
10927 file it would otherwise output, in other words if the files to be
10928 chopped contain duplicated units. This switch bypasses this
10929 check, and causes all but the last instance of such duplicated
10930 units to be skipped.
10933 @item --GCC=@var{xxxx}
10934 @cindex @option{--GCC=} (@code{gnatchop})
10935 Specify the path of the GNAT parser to be used. When this switch is used,
10936 no attempt is made to add the prefix to the GNAT parser executable.
10940 @node Examples of gnatchop Usage
10941 @section Examples of @code{gnatchop} Usage
10945 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
10948 @item gnatchop -w hello_s.ada prerelease/files
10951 Chops the source file @file{hello_s.ada}. The output files will be
10952 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
10954 files with matching names in that directory (no files in the current
10955 directory are modified).
10957 @item gnatchop ^archive^ARCHIVE.^
10958 Chops the source file @file{^archive^ARCHIVE.^}
10959 into the current directory. One
10960 useful application of @code{gnatchop} is in sending sets of sources
10961 around, for example in email messages. The required sources are simply
10962 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
10964 @command{gnatchop} is used at the other end to reconstitute the original
10967 @item gnatchop file1 file2 file3 direc
10968 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
10969 the resulting files in the directory @file{direc}. Note that if any units
10970 occur more than once anywhere within this set of files, an error message
10971 is generated, and no files are written. To override this check, use the
10972 @option{^-w^/OVERWRITE^} switch,
10973 in which case the last occurrence in the last file will
10974 be the one that is output, and earlier duplicate occurrences for a given
10975 unit will be skipped.
10978 @node Configuration Pragmas
10979 @chapter Configuration Pragmas
10980 @cindex Configuration pragmas
10981 @cindex Pragmas, configuration
10984 Configuration pragmas include those pragmas described as
10985 such in the Ada Reference Manual, as well as
10986 implementation-dependent pragmas that are configuration pragmas.
10987 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
10988 for details on these additional GNAT-specific configuration pragmas.
10989 Most notably, the pragma @code{Source_File_Name}, which allows
10990 specifying non-default names for source files, is a configuration
10991 pragma. The following is a complete list of configuration pragmas
10992 recognized by GNAT:
11004 Compile_Time_Warning
11006 Component_Alignment
11013 External_Name_Casing
11016 Float_Representation
11029 Priority_Specific_Dispatching
11032 Propagate_Exceptions
11035 Restricted_Run_Time
11037 Restrictions_Warnings
11040 Source_File_Name_Project
11043 Suppress_Exception_Locations
11044 Task_Dispatching_Policy
11050 Wide_Character_Encoding
11055 * Handling of Configuration Pragmas::
11056 * The Configuration Pragmas Files::
11059 @node Handling of Configuration Pragmas
11060 @section Handling of Configuration Pragmas
11062 Configuration pragmas may either appear at the start of a compilation
11063 unit, in which case they apply only to that unit, or they may apply to
11064 all compilations performed in a given compilation environment.
11066 GNAT also provides the @code{gnatchop} utility to provide an automatic
11067 way to handle configuration pragmas following the semantics for
11068 compilations (that is, files with multiple units), described in the RM.
11069 See @ref{Operating gnatchop in Compilation Mode} for details.
11070 However, for most purposes, it will be more convenient to edit the
11071 @file{gnat.adc} file that contains configuration pragmas directly,
11072 as described in the following section.
11074 @node The Configuration Pragmas Files
11075 @section The Configuration Pragmas Files
11076 @cindex @file{gnat.adc}
11079 In GNAT a compilation environment is defined by the current
11080 directory at the time that a compile command is given. This current
11081 directory is searched for a file whose name is @file{gnat.adc}. If
11082 this file is present, it is expected to contain one or more
11083 configuration pragmas that will be applied to the current compilation.
11084 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11087 Configuration pragmas may be entered into the @file{gnat.adc} file
11088 either by running @code{gnatchop} on a source file that consists only of
11089 configuration pragmas, or more conveniently by
11090 direct editing of the @file{gnat.adc} file, which is a standard format
11093 In addition to @file{gnat.adc}, additional files containing configuration
11094 pragmas may be applied to the current compilation using the switch
11095 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11096 contains only configuration pragmas. These configuration pragmas are
11097 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11098 is present and switch @option{-gnatA} is not used).
11100 It is allowed to specify several switches @option{-gnatec}, all of which
11101 will be taken into account.
11103 If you are using project file, a separate mechanism is provided using
11104 project attributes, see @ref{Specifying Configuration Pragmas} for more
11108 Of special interest to GNAT OpenVMS Alpha is the following
11109 configuration pragma:
11111 @smallexample @c ada
11113 pragma Extend_System (Aux_DEC);
11118 In the presence of this pragma, GNAT adds to the definition of the
11119 predefined package SYSTEM all the additional types and subprograms that are
11120 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11123 @node Handling Arbitrary File Naming Conventions Using gnatname
11124 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11125 @cindex Arbitrary File Naming Conventions
11128 * Arbitrary File Naming Conventions::
11129 * Running gnatname::
11130 * Switches for gnatname::
11131 * Examples of gnatname Usage::
11134 @node Arbitrary File Naming Conventions
11135 @section Arbitrary File Naming Conventions
11138 The GNAT compiler must be able to know the source file name of a compilation
11139 unit. When using the standard GNAT default file naming conventions
11140 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11141 does not need additional information.
11144 When the source file names do not follow the standard GNAT default file naming
11145 conventions, the GNAT compiler must be given additional information through
11146 a configuration pragmas file (@pxref{Configuration Pragmas})
11148 When the non-standard file naming conventions are well-defined,
11149 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11150 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11151 if the file naming conventions are irregular or arbitrary, a number
11152 of pragma @code{Source_File_Name} for individual compilation units
11154 To help maintain the correspondence between compilation unit names and
11155 source file names within the compiler,
11156 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11159 @node Running gnatname
11160 @section Running @code{gnatname}
11163 The usual form of the @code{gnatname} command is
11166 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11167 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11171 All of the arguments are optional. If invoked without any argument,
11172 @code{gnatname} will display its usage.
11175 When used with at least one naming pattern, @code{gnatname} will attempt to
11176 find all the compilation units in files that follow at least one of the
11177 naming patterns. To find these compilation units,
11178 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11182 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11183 Each Naming Pattern is enclosed between double quotes.
11184 A Naming Pattern is a regular expression similar to the wildcard patterns
11185 used in file names by the Unix shells or the DOS prompt.
11188 @code{gnatname} may be called with several sections of directories/patterns.
11189 Sections are separated by switch @code{--and}. In each section, there must be
11190 at least one pattern. If no directory is specified in a section, the current
11191 directory (or the project directory is @code{-P} is used) is implied.
11192 The options other that the directory switches and the patterns apply globally
11193 even if they are in different sections.
11196 Examples of Naming Patterns are
11205 For a more complete description of the syntax of Naming Patterns,
11206 see the second kind of regular expressions described in @file{g-regexp.ads}
11207 (the ``Glob'' regular expressions).
11210 When invoked with no switch @code{-P}, @code{gnatname} will create a
11211 configuration pragmas file @file{gnat.adc} in the current working directory,
11212 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11215 @node Switches for gnatname
11216 @section Switches for @code{gnatname}
11219 Switches for @code{gnatname} must precede any specified Naming Pattern.
11222 You may specify any of the following switches to @code{gnatname}:
11228 @cindex @option{--version} @command{gnatname}
11229 Display Copyright and version, then exit disregarding all other options.
11232 @cindex @option{--help} @command{gnatname}
11233 If @option{--version} was not used, display usage, then exit disregarding
11237 Start another section of directories/patterns.
11239 @item ^-c^/CONFIG_FILE=^@file{file}
11240 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11241 Create a configuration pragmas file @file{file} (instead of the default
11244 There may be zero, one or more space between @option{-c} and
11247 @file{file} may include directory information. @file{file} must be
11248 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11249 When a switch @option{^-c^/CONFIG_FILE^} is
11250 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11252 @item ^-d^/SOURCE_DIRS=^@file{dir}
11253 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11254 Look for source files in directory @file{dir}. There may be zero, one or more
11255 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11256 When a switch @option{^-d^/SOURCE_DIRS^}
11257 is specified, the current working directory will not be searched for source
11258 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11259 or @option{^-D^/DIR_FILES^} switch.
11260 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11261 If @file{dir} is a relative path, it is relative to the directory of
11262 the configuration pragmas file specified with switch
11263 @option{^-c^/CONFIG_FILE^},
11264 or to the directory of the project file specified with switch
11265 @option{^-P^/PROJECT_FILE^} or,
11266 if neither switch @option{^-c^/CONFIG_FILE^}
11267 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11268 current working directory. The directory
11269 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11271 @item ^-D^/DIRS_FILE=^@file{file}
11272 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11273 Look for source files in all directories listed in text file @file{file}.
11274 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11276 @file{file} must be an existing, readable text file.
11277 Each nonempty line in @file{file} must be a directory.
11278 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11279 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11282 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11283 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11284 Foreign patterns. Using this switch, it is possible to add sources of languages
11285 other than Ada to the list of sources of a project file.
11286 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11289 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11292 will look for Ada units in all files with the @file{.ada} extension,
11293 and will add to the list of file for project @file{prj.gpr} the C files
11294 with extension @file{.^c^C^}.
11297 @cindex @option{^-h^/HELP^} (@code{gnatname})
11298 Output usage (help) information. The output is written to @file{stdout}.
11300 @item ^-P^/PROJECT_FILE=^@file{proj}
11301 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11302 Create or update project file @file{proj}. There may be zero, one or more space
11303 between @option{-P} and @file{proj}. @file{proj} may include directory
11304 information. @file{proj} must be writable.
11305 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11306 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11307 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11309 @item ^-v^/VERBOSE^
11310 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11311 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11312 This includes name of the file written, the name of the directories to search
11313 and, for each file in those directories whose name matches at least one of
11314 the Naming Patterns, an indication of whether the file contains a unit,
11315 and if so the name of the unit.
11317 @item ^-v -v^/VERBOSE /VERBOSE^
11318 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11319 Very Verbose mode. In addition to the output produced in verbose mode,
11320 for each file in the searched directories whose name matches none of
11321 the Naming Patterns, an indication is given that there is no match.
11323 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11324 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11325 Excluded patterns. Using this switch, it is possible to exclude some files
11326 that would match the name patterns. For example,
11328 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11331 will look for Ada units in all files with the @file{.ada} extension,
11332 except those whose names end with @file{_nt.ada}.
11336 @node Examples of gnatname Usage
11337 @section Examples of @code{gnatname} Usage
11341 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11347 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11352 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11353 and be writable. In addition, the directory
11354 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11355 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11358 Note the optional spaces after @option{-c} and @option{-d}.
11363 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11364 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11367 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11368 /EXCLUDED_PATTERN=*_nt_body.ada
11369 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11370 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11374 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11375 even in conjunction with one or several switches
11376 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11377 are used in this example.
11379 @c *****************************************
11380 @c * G N A T P r o j e c t M a n a g e r *
11381 @c *****************************************
11382 @node GNAT Project Manager
11383 @chapter GNAT Project Manager
11387 * Examples of Project Files::
11388 * Project File Syntax::
11389 * Objects and Sources in Project Files::
11390 * Importing Projects::
11391 * Project Extension::
11392 * Project Hierarchy Extension::
11393 * External References in Project Files::
11394 * Packages in Project Files::
11395 * Variables from Imported Projects::
11397 * Library Projects::
11398 * Stand-alone Library Projects::
11399 * Switches Related to Project Files::
11400 * Tools Supporting Project Files::
11401 * An Extended Example::
11402 * Project File Complete Syntax::
11405 @c ****************
11406 @c * Introduction *
11407 @c ****************
11410 @section Introduction
11413 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11414 you to manage complex builds involving a number of source files, directories,
11415 and compilation options for different system configurations. In particular,
11416 project files allow you to specify:
11419 The directory or set of directories containing the source files, and/or the
11420 names of the specific source files themselves
11422 The directory in which the compiler's output
11423 (@file{ALI} files, object files, tree files) is to be placed
11425 The directory in which the executable programs is to be placed
11427 ^Switch^Switch^ settings for any of the project-enabled tools
11428 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11429 @code{gnatfind}); you can apply these settings either globally or to individual
11432 The source files containing the main subprogram(s) to be built
11434 The source programming language(s) (currently Ada and/or C)
11436 Source file naming conventions; you can specify these either globally or for
11437 individual compilation units
11444 @node Project Files
11445 @subsection Project Files
11448 Project files are written in a syntax close to that of Ada, using familiar
11449 notions such as packages, context clauses, declarations, default values,
11450 assignments, and inheritance. Finally, project files can be built
11451 hierarchically from other project files, simplifying complex system
11452 integration and project reuse.
11454 A @dfn{project} is a specific set of values for various compilation properties.
11455 The settings for a given project are described by means of
11456 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11457 Property values in project files are either strings or lists of strings.
11458 Properties that are not explicitly set receive default values. A project
11459 file may interrogate the values of @dfn{external variables} (user-defined
11460 command-line switches or environment variables), and it may specify property
11461 settings conditionally, based on the value of such variables.
11463 In simple cases, a project's source files depend only on other source files
11464 in the same project, or on the predefined libraries. (@emph{Dependence} is
11466 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11467 the Project Manager also allows more sophisticated arrangements,
11468 where the source files in one project depend on source files in other
11472 One project can @emph{import} other projects containing needed source files.
11474 You can organize GNAT projects in a hierarchy: a @emph{child} project
11475 can extend a @emph{parent} project, inheriting the parent's source files and
11476 optionally overriding any of them with alternative versions
11480 More generally, the Project Manager lets you structure large development
11481 efforts into hierarchical subsystems, where build decisions are delegated
11482 to the subsystem level, and thus different compilation environments
11483 (^switch^switch^ settings) used for different subsystems.
11485 The Project Manager is invoked through the
11486 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11487 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11489 There may be zero, one or more spaces between @option{-P} and
11490 @option{@emph{projectfile}}.
11492 If you want to define (on the command line) an external variable that is
11493 queried by the project file, you must use the
11494 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11495 The Project Manager parses and interprets the project file, and drives the
11496 invoked tool based on the project settings.
11498 The Project Manager supports a wide range of development strategies,
11499 for systems of all sizes. Here are some typical practices that are
11503 Using a common set of source files, but generating object files in different
11504 directories via different ^switch^switch^ settings
11506 Using a mostly-shared set of source files, but with different versions of
11511 The destination of an executable can be controlled inside a project file
11512 using the @option{^-o^-o^}
11514 In the absence of such a ^switch^switch^ either inside
11515 the project file or on the command line, any executable files generated by
11516 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11517 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11518 in the object directory of the project.
11520 You can use project files to achieve some of the effects of a source
11521 versioning system (for example, defining separate projects for
11522 the different sets of sources that comprise different releases) but the
11523 Project Manager is independent of any source configuration management tools
11524 that might be used by the developers.
11526 The next section introduces the main features of GNAT's project facility
11527 through a sequence of examples; subsequent sections will present the syntax
11528 and semantics in more detail. A more formal description of the project
11529 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11532 @c *****************************
11533 @c * Examples of Project Files *
11534 @c *****************************
11536 @node Examples of Project Files
11537 @section Examples of Project Files
11539 This section illustrates some of the typical uses of project files and
11540 explains their basic structure and behavior.
11543 * Common Sources with Different ^Switches^Switches^ and Directories::
11544 * Using External Variables::
11545 * Importing Other Projects::
11546 * Extending a Project::
11549 @node Common Sources with Different ^Switches^Switches^ and Directories
11550 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11554 * Specifying the Object Directory::
11555 * Specifying the Exec Directory::
11556 * Project File Packages::
11557 * Specifying ^Switch^Switch^ Settings::
11558 * Main Subprograms::
11559 * Executable File Names::
11560 * Source File Naming Conventions::
11561 * Source Language(s)::
11565 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11566 @file{proc.adb} are in the @file{/common} directory. The file
11567 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11568 package @code{Pack}. We want to compile these source files under two sets
11569 of ^switches^switches^:
11572 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11573 and the @option{^-gnata^-gnata^},
11574 @option{^-gnato^-gnato^},
11575 and @option{^-gnatE^-gnatE^} switches to the
11576 compiler; the compiler's output is to appear in @file{/common/debug}
11578 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11579 to the compiler; the compiler's output is to appear in @file{/common/release}
11583 The GNAT project files shown below, respectively @file{debug.gpr} and
11584 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11597 ^/common/debug^[COMMON.DEBUG]^
11602 ^/common/release^[COMMON.RELEASE]^
11607 Here are the corresponding project files:
11609 @smallexample @c projectfile
11612 for Object_Dir use "debug";
11613 for Main use ("proc");
11616 for ^Default_Switches^Default_Switches^ ("Ada")
11618 for Executable ("proc.adb") use "proc1";
11623 package Compiler is
11624 for ^Default_Switches^Default_Switches^ ("Ada")
11625 use ("-fstack-check",
11628 "^-gnatE^-gnatE^");
11634 @smallexample @c projectfile
11637 for Object_Dir use "release";
11638 for Exec_Dir use ".";
11639 for Main use ("proc");
11641 package Compiler is
11642 for ^Default_Switches^Default_Switches^ ("Ada")
11650 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11651 insensitive), and analogously the project defined by @file{release.gpr} is
11652 @code{"Release"}. For consistency the file should have the same name as the
11653 project, and the project file's extension should be @code{"gpr"}. These
11654 conventions are not required, but a warning is issued if they are not followed.
11656 If the current directory is @file{^/temp^[TEMP]^}, then the command
11658 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11662 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11663 as well as the @code{^proc1^PROC1.EXE^} executable,
11664 using the ^switch^switch^ settings defined in the project file.
11666 Likewise, the command
11668 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11672 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11673 and the @code{^proc^PROC.EXE^}
11674 executable in @file{^/common^[COMMON]^},
11675 using the ^switch^switch^ settings from the project file.
11678 @unnumberedsubsubsec Source Files
11681 If a project file does not explicitly specify a set of source directories or
11682 a set of source files, then by default the project's source files are the
11683 Ada source files in the project file directory. Thus @file{pack.ads},
11684 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11686 @node Specifying the Object Directory
11687 @unnumberedsubsubsec Specifying the Object Directory
11690 Several project properties are modeled by Ada-style @emph{attributes};
11691 a property is defined by supplying the equivalent of an Ada attribute
11692 definition clause in the project file.
11693 A project's object directory is another such a property; the corresponding
11694 attribute is @code{Object_Dir}, and its value is also a string expression,
11695 specified either as absolute or relative. In the later case,
11696 it is relative to the project file directory. Thus the compiler's
11697 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
11698 (for the @code{Debug} project)
11699 and to @file{^/common/release^[COMMON.RELEASE]^}
11700 (for the @code{Release} project).
11701 If @code{Object_Dir} is not specified, then the default is the project file
11704 @node Specifying the Exec Directory
11705 @unnumberedsubsubsec Specifying the Exec Directory
11708 A project's exec directory is another property; the corresponding
11709 attribute is @code{Exec_Dir}, and its value is also a string expression,
11710 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
11711 then the default is the object directory (which may also be the project file
11712 directory if attribute @code{Object_Dir} is not specified). Thus the executable
11713 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
11714 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
11715 and in @file{^/common^[COMMON]^} for the @code{Release} project.
11717 @node Project File Packages
11718 @unnumberedsubsubsec Project File Packages
11721 A GNAT tool that is integrated with the Project Manager is modeled by a
11722 corresponding package in the project file. In the example above,
11723 The @code{Debug} project defines the packages @code{Builder}
11724 (for @command{gnatmake}) and @code{Compiler};
11725 the @code{Release} project defines only the @code{Compiler} package.
11727 The Ada-like package syntax is not to be taken literally. Although packages in
11728 project files bear a surface resemblance to packages in Ada source code, the
11729 notation is simply a way to convey a grouping of properties for a named
11730 entity. Indeed, the package names permitted in project files are restricted
11731 to a predefined set, corresponding to the project-aware tools, and the contents
11732 of packages are limited to a small set of constructs.
11733 The packages in the example above contain attribute definitions.
11735 @node Specifying ^Switch^Switch^ Settings
11736 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
11739 ^Switch^Switch^ settings for a project-aware tool can be specified through
11740 attributes in the package that corresponds to the tool.
11741 The example above illustrates one of the relevant attributes,
11742 @code{^Default_Switches^Default_Switches^}, which is defined in packages
11743 in both project files.
11744 Unlike simple attributes like @code{Source_Dirs},
11745 @code{^Default_Switches^Default_Switches^} is
11746 known as an @emph{associative array}. When you define this attribute, you must
11747 supply an ``index'' (a literal string), and the effect of the attribute
11748 definition is to set the value of the array at the specified index.
11749 For the @code{^Default_Switches^Default_Switches^} attribute,
11750 the index is a programming language (in our case, Ada),
11751 and the value specified (after @code{use}) must be a list
11752 of string expressions.
11754 The attributes permitted in project files are restricted to a predefined set.
11755 Some may appear at project level, others in packages.
11756 For any attribute that is an associative array, the index must always be a
11757 literal string, but the restrictions on this string (e.g., a file name or a
11758 language name) depend on the individual attribute.
11759 Also depending on the attribute, its specified value will need to be either a
11760 string or a string list.
11762 In the @code{Debug} project, we set the switches for two tools,
11763 @command{gnatmake} and the compiler, and thus we include the two corresponding
11764 packages; each package defines the @code{^Default_Switches^Default_Switches^}
11765 attribute with index @code{"Ada"}.
11766 Note that the package corresponding to
11767 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
11768 similar, but only includes the @code{Compiler} package.
11770 In project @code{Debug} above, the ^switches^switches^ starting with
11771 @option{-gnat} that are specified in package @code{Compiler}
11772 could have been placed in package @code{Builder}, since @command{gnatmake}
11773 transmits all such ^switches^switches^ to the compiler.
11775 @node Main Subprograms
11776 @unnumberedsubsubsec Main Subprograms
11779 One of the specifiable properties of a project is a list of files that contain
11780 main subprograms. This property is captured in the @code{Main} attribute,
11781 whose value is a list of strings. If a project defines the @code{Main}
11782 attribute, it is not necessary to identify the main subprogram(s) when
11783 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
11785 @node Executable File Names
11786 @unnumberedsubsubsec Executable File Names
11789 By default, the executable file name corresponding to a main source is
11790 deduced from the main source file name. Through the attributes
11791 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
11792 it is possible to change this default.
11793 In project @code{Debug} above, the executable file name
11794 for main source @file{^proc.adb^PROC.ADB^} is
11795 @file{^proc1^PROC1.EXE^}.
11796 Attribute @code{Executable_Suffix}, when specified, may change the suffix
11797 of the executable files, when no attribute @code{Executable} applies:
11798 its value replace the platform-specific executable suffix.
11799 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
11800 specify a non-default executable file name when several mains are built at once
11801 in a single @command{gnatmake} command.
11803 @node Source File Naming Conventions
11804 @unnumberedsubsubsec Source File Naming Conventions
11807 Since the project files above do not specify any source file naming
11808 conventions, the GNAT defaults are used. The mechanism for defining source
11809 file naming conventions -- a package named @code{Naming} --
11810 is described below (@pxref{Naming Schemes}).
11812 @node Source Language(s)
11813 @unnumberedsubsubsec Source Language(s)
11816 Since the project files do not specify a @code{Languages} attribute, by
11817 default the GNAT tools assume that the language of the project file is Ada.
11818 More generally, a project can comprise source files
11819 in Ada, C, and/or other languages.
11821 @node Using External Variables
11822 @subsection Using External Variables
11825 Instead of supplying different project files for debug and release, we can
11826 define a single project file that queries an external variable (set either
11827 on the command line or via an ^environment variable^logical name^) in order to
11828 conditionally define the appropriate settings. Again, assume that the
11829 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
11830 located in directory @file{^/common^[COMMON]^}. The following project file,
11831 @file{build.gpr}, queries the external variable named @code{STYLE} and
11832 defines an object directory and ^switch^switch^ settings based on whether
11833 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
11834 the default is @code{"deb"}.
11836 @smallexample @c projectfile
11839 for Main use ("proc");
11841 type Style_Type is ("deb", "rel");
11842 Style : Style_Type := external ("STYLE", "deb");
11846 for Object_Dir use "debug";
11849 for Object_Dir use "release";
11850 for Exec_Dir use ".";
11859 for ^Default_Switches^Default_Switches^ ("Ada")
11861 for Executable ("proc") use "proc1";
11870 package Compiler is
11874 for ^Default_Switches^Default_Switches^ ("Ada")
11875 use ("^-gnata^-gnata^",
11877 "^-gnatE^-gnatE^");
11880 for ^Default_Switches^Default_Switches^ ("Ada")
11891 @code{Style_Type} is an example of a @emph{string type}, which is the project
11892 file analog of an Ada enumeration type but whose components are string literals
11893 rather than identifiers. @code{Style} is declared as a variable of this type.
11895 The form @code{external("STYLE", "deb")} is known as an
11896 @emph{external reference}; its first argument is the name of an
11897 @emph{external variable}, and the second argument is a default value to be
11898 used if the external variable doesn't exist. You can define an external
11899 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
11900 or you can use ^an environment variable^a logical name^
11901 as an external variable.
11903 Each @code{case} construct is expanded by the Project Manager based on the
11904 value of @code{Style}. Thus the command
11907 gnatmake -P/common/build.gpr -XSTYLE=deb
11913 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
11918 is equivalent to the @command{gnatmake} invocation using the project file
11919 @file{debug.gpr} in the earlier example. So is the command
11921 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
11925 since @code{"deb"} is the default for @code{STYLE}.
11931 gnatmake -P/common/build.gpr -XSTYLE=rel
11937 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
11942 is equivalent to the @command{gnatmake} invocation using the project file
11943 @file{release.gpr} in the earlier example.
11945 @node Importing Other Projects
11946 @subsection Importing Other Projects
11947 @cindex @code{ADA_PROJECT_PATH}
11950 A compilation unit in a source file in one project may depend on compilation
11951 units in source files in other projects. To compile this unit under
11952 control of a project file, the
11953 dependent project must @emph{import} the projects containing the needed source
11955 This effect is obtained using syntax similar to an Ada @code{with} clause,
11956 but where @code{with}ed entities are strings that denote project files.
11958 As an example, suppose that the two projects @code{GUI_Proj} and
11959 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
11960 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
11961 and @file{^/comm^[COMM]^}, respectively.
11962 Suppose that the source files for @code{GUI_Proj} are
11963 @file{gui.ads} and @file{gui.adb}, and that the source files for
11964 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
11965 files is located in its respective project file directory. Schematically:
11984 We want to develop an application in directory @file{^/app^[APP]^} that
11985 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
11986 the corresponding project files (e.g.@: the ^switch^switch^ settings
11987 and object directory).
11988 Skeletal code for a main procedure might be something like the following:
11990 @smallexample @c ada
11993 procedure App_Main is
12002 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12005 @smallexample @c projectfile
12007 with "/gui/gui_proj", "/comm/comm_proj";
12008 project App_Proj is
12009 for Main use ("app_main");
12015 Building an executable is achieved through the command:
12017 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12020 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12021 in the directory where @file{app_proj.gpr} resides.
12023 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12024 (as illustrated above) the @code{with} clause can omit the extension.
12026 Our example specified an absolute path for each imported project file.
12027 Alternatively, the directory name of an imported object can be omitted
12031 The imported project file is in the same directory as the importing project
12034 You have defined ^an environment variable^a logical name^
12035 that includes the directory containing
12036 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
12037 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12038 directory names separated by colons (semicolons on Windows).
12042 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12043 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12046 @smallexample @c projectfile
12048 with "gui_proj", "comm_proj";
12049 project App_Proj is
12050 for Main use ("app_main");
12056 Importing other projects can create ambiguities.
12057 For example, the same unit might be present in different imported projects, or
12058 it might be present in both the importing project and in an imported project.
12059 Both of these conditions are errors. Note that in the current version of
12060 the Project Manager, it is illegal to have an ambiguous unit even if the
12061 unit is never referenced by the importing project. This restriction may be
12062 relaxed in a future release.
12064 @node Extending a Project
12065 @subsection Extending a Project
12068 In large software systems it is common to have multiple
12069 implementations of a common interface; in Ada terms, multiple versions of a
12070 package body for the same spec. For example, one implementation
12071 might be safe for use in tasking programs, while another might only be used
12072 in sequential applications. This can be modeled in GNAT using the concept
12073 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12074 another project (the ``parent'') then by default all source files of the
12075 parent project are inherited by the child, but the child project can
12076 override any of the parent's source files with new versions, and can also
12077 add new files. This facility is the project analog of a type extension in
12078 Object-Oriented Programming. Project hierarchies are permitted (a child
12079 project may be the parent of yet another project), and a project that
12080 inherits one project can also import other projects.
12082 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12083 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12084 @file{pack.adb}, and @file{proc.adb}:
12097 Note that the project file can simply be empty (that is, no attribute or
12098 package is defined):
12100 @smallexample @c projectfile
12102 project Seq_Proj is
12108 implying that its source files are all the Ada source files in the project
12111 Suppose we want to supply an alternate version of @file{pack.adb}, in
12112 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12113 @file{pack.ads} and @file{proc.adb}. We can define a project
12114 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12118 ^/tasking^[TASKING]^
12124 project Tasking_Proj extends "/seq/seq_proj" is
12130 The version of @file{pack.adb} used in a build depends on which project file
12133 Note that we could have obtained the desired behavior using project import
12134 rather than project inheritance; a @code{base} project would contain the
12135 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12136 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12137 would import @code{base} and add a different version of @file{pack.adb}. The
12138 choice depends on whether other sources in the original project need to be
12139 overridden. If they do, then project extension is necessary, otherwise,
12140 importing is sufficient.
12143 In a project file that extends another project file, it is possible to
12144 indicate that an inherited source is not part of the sources of the extending
12145 project. This is necessary sometimes when a package spec has been overloaded
12146 and no longer requires a body: in this case, it is necessary to indicate that
12147 the inherited body is not part of the sources of the project, otherwise there
12148 will be a compilation error when compiling the spec.
12150 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12151 Its value is a string list: a list of file names. It is also possible to use
12152 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12153 the file name of a text file containing a list of file names, one per line.
12155 @smallexample @c @projectfile
12156 project B extends "a" is
12157 for Source_Files use ("pkg.ads");
12158 -- New spec of Pkg does not need a completion
12159 for Excluded_Source_Files use ("pkg.adb");
12163 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12164 is still needed: if it is possible to build using @command{gnatmake} when such
12165 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12166 it is possible to remove the source completely from a system that includes
12169 @c ***********************
12170 @c * Project File Syntax *
12171 @c ***********************
12173 @node Project File Syntax
12174 @section Project File Syntax
12178 * Qualified Projects::
12184 * Associative Array Attributes::
12185 * case Constructions::
12189 This section describes the structure of project files.
12191 A project may be an @emph{independent project}, entirely defined by a single
12192 project file. Any Ada source file in an independent project depends only
12193 on the predefined library and other Ada source files in the same project.
12196 A project may also @dfn{depend on} other projects, in either or both of
12197 the following ways:
12199 @item It may import any number of projects
12200 @item It may extend at most one other project
12204 The dependence relation is a directed acyclic graph (the subgraph reflecting
12205 the ``extends'' relation is a tree).
12207 A project's @dfn{immediate sources} are the source files directly defined by
12208 that project, either implicitly by residing in the project file's directory,
12209 or explicitly through any of the source-related attributes described below.
12210 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12211 of @var{proj} together with the immediate sources (unless overridden) of any
12212 project on which @var{proj} depends (either directly or indirectly).
12215 @subsection Basic Syntax
12218 As seen in the earlier examples, project files have an Ada-like syntax.
12219 The minimal project file is:
12220 @smallexample @c projectfile
12229 The identifier @code{Empty} is the name of the project.
12230 This project name must be present after the reserved
12231 word @code{end} at the end of the project file, followed by a semi-colon.
12233 Any name in a project file, such as the project name or a variable name,
12234 has the same syntax as an Ada identifier.
12236 The reserved words of project files are the Ada 95 reserved words plus
12237 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12238 reserved words currently used in project file syntax are:
12274 Comments in project files have the same syntax as in Ada, two consecutive
12275 hyphens through the end of the line.
12277 @node Qualified Projects
12278 @subsection Qualified Projects
12281 Before the reserved @code{project}, there may be one or two "qualifiers", that
12282 is identifiers or other reserved words, to qualify the project.
12284 The current list of qualifiers is:
12288 @code{abstract}: qualify a project with no sources. An abstract project must
12289 have a declaration specifying that there are no sources in the project, and,
12290 if it extends another project, the project it extends must also be a qualified
12294 @code{standard}: a standard project is a non library project with sources.
12297 @code{aggregate}: for future extension
12300 @code{aggregate library}: for future extension
12303 @code{library}: a library project must declare both attributes
12304 @code{Library_Name} and @code{Library_Dir}.
12307 @code{configuration}: a configuration project cannot be in a project tree.
12311 @subsection Packages
12314 A project file may contain @emph{packages}. The name of a package must be one
12315 of the identifiers from the following list. A package
12316 with a given name may only appear once in a project file. Package names are
12317 case insensitive. The following package names are legal:
12333 @code{Cross_Reference}
12337 @code{Pretty_Printer}
12347 @code{Language_Processing}
12351 In its simplest form, a package may be empty:
12353 @smallexample @c projectfile
12363 A package may contain @emph{attribute declarations},
12364 @emph{variable declarations} and @emph{case constructions}, as will be
12367 When there is ambiguity between a project name and a package name,
12368 the name always designates the project. To avoid possible confusion, it is
12369 always a good idea to avoid naming a project with one of the
12370 names allowed for packages or any name that starts with @code{gnat}.
12373 @subsection Expressions
12376 An @emph{expression} is either a @emph{string expression} or a
12377 @emph{string list expression}.
12379 A @emph{string expression} is either a @emph{simple string expression} or a
12380 @emph{compound string expression}.
12382 A @emph{simple string expression} is one of the following:
12384 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12385 @item A string-valued variable reference (@pxref{Variables})
12386 @item A string-valued attribute reference (@pxref{Attributes})
12387 @item An external reference (@pxref{External References in Project Files})
12391 A @emph{compound string expression} is a concatenation of string expressions,
12392 using the operator @code{"&"}
12394 Path & "/" & File_Name & ".ads"
12398 A @emph{string list expression} is either a
12399 @emph{simple string list expression} or a
12400 @emph{compound string list expression}.
12402 A @emph{simple string list expression} is one of the following:
12404 @item A parenthesized list of zero or more string expressions,
12405 separated by commas
12407 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12410 @item A string list-valued variable reference
12411 @item A string list-valued attribute reference
12415 A @emph{compound string list expression} is the concatenation (using
12416 @code{"&"}) of a simple string list expression and an expression. Note that
12417 each term in a compound string list expression, except the first, may be
12418 either a string expression or a string list expression.
12420 @smallexample @c projectfile
12422 File_Name_List := () & File_Name; -- One string in this list
12423 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12425 Big_List := File_Name_List & Extended_File_Name_List;
12426 -- Concatenation of two string lists: three strings
12427 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12428 -- Illegal: must start with a string list
12433 @subsection String Types
12436 A @emph{string type declaration} introduces a discrete set of string literals.
12437 If a string variable is declared to have this type, its value
12438 is restricted to the given set of literals.
12440 Here is an example of a string type declaration:
12442 @smallexample @c projectfile
12443 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12447 Variables of a string type are called @emph{typed variables}; all other
12448 variables are called @emph{untyped variables}. Typed variables are
12449 particularly useful in @code{case} constructions, to support conditional
12450 attribute declarations.
12451 (@pxref{case Constructions}).
12453 The string literals in the list are case sensitive and must all be different.
12454 They may include any graphic characters allowed in Ada, including spaces.
12456 A string type may only be declared at the project level, not inside a package.
12458 A string type may be referenced by its name if it has been declared in the same
12459 project file, or by an expanded name whose prefix is the name of the project
12460 in which it is declared.
12463 @subsection Variables
12466 A variable may be declared at the project file level, or within a package.
12467 Here are some examples of variable declarations:
12469 @smallexample @c projectfile
12471 This_OS : OS := external ("OS"); -- a typed variable declaration
12472 That_OS := "GNU/Linux"; -- an untyped variable declaration
12477 The syntax of a @emph{typed variable declaration} is identical to the Ada
12478 syntax for an object declaration. By contrast, the syntax of an untyped
12479 variable declaration is identical to an Ada assignment statement. In fact,
12480 variable declarations in project files have some of the characteristics of
12481 an assignment, in that successive declarations for the same variable are
12482 allowed. Untyped variable declarations do establish the expected kind of the
12483 variable (string or string list), and successive declarations for it must
12484 respect the initial kind.
12487 A string variable declaration (typed or untyped) declares a variable
12488 whose value is a string. This variable may be used as a string expression.
12489 @smallexample @c projectfile
12490 File_Name := "readme.txt";
12491 Saved_File_Name := File_Name & ".saved";
12495 A string list variable declaration declares a variable whose value is a list
12496 of strings. The list may contain any number (zero or more) of strings.
12498 @smallexample @c projectfile
12500 List_With_One_Element := ("^-gnaty^-gnaty^");
12501 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12502 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12503 "pack2.ada", "util_.ada", "util.ada");
12507 The same typed variable may not be declared more than once at project level,
12508 and it may not be declared more than once in any package; it is in effect
12511 The same untyped variable may be declared several times. Declarations are
12512 elaborated in the order in which they appear, so the new value replaces
12513 the old one, and any subsequent reference to the variable uses the new value.
12514 However, as noted above, if a variable has been declared as a string, all
12516 declarations must give it a string value. Similarly, if a variable has
12517 been declared as a string list, all subsequent declarations
12518 must give it a string list value.
12520 A @emph{variable reference} may take several forms:
12523 @item The simple variable name, for a variable in the current package (if any)
12524 or in the current project
12525 @item An expanded name, whose prefix is a context name.
12529 A @emph{context} may be one of the following:
12532 @item The name of an existing package in the current project
12533 @item The name of an imported project of the current project
12534 @item The name of an ancestor project (i.e., a project extended by the current
12535 project, either directly or indirectly)
12536 @item An expanded name whose prefix is an imported/parent project name, and
12537 whose selector is a package name in that project.
12541 A variable reference may be used in an expression.
12544 @subsection Attributes
12547 A project (and its packages) may have @emph{attributes} that define
12548 the project's properties. Some attributes have values that are strings;
12549 others have values that are string lists.
12551 There are two categories of attributes: @emph{simple attributes}
12552 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12554 Legal project attribute names, and attribute names for each legal package are
12555 listed below. Attributes names are case-insensitive.
12557 The following attributes are defined on projects (all are simple attributes):
12559 @multitable @columnfractions .4 .3
12560 @item @emph{Attribute Name}
12562 @item @code{Source_Files}
12564 @item @code{Source_Dirs}
12566 @item @code{Source_List_File}
12568 @item @code{Object_Dir}
12570 @item @code{Exec_Dir}
12572 @item @code{Excluded_Source_Dirs}
12574 @item @code{Excluded_Source_Files}
12576 @item @code{Excluded_Source_List_File}
12578 @item @code{Languages}
12582 @item @code{Library_Dir}
12584 @item @code{Library_Name}
12586 @item @code{Library_Kind}
12588 @item @code{Library_Version}
12590 @item @code{Library_Interface}
12592 @item @code{Library_Auto_Init}
12594 @item @code{Library_Options}
12596 @item @code{Library_Src_Dir}
12598 @item @code{Library_ALI_Dir}
12600 @item @code{Library_GCC}
12602 @item @code{Library_Symbol_File}
12604 @item @code{Library_Symbol_Policy}
12606 @item @code{Library_Reference_Symbol_File}
12608 @item @code{Externally_Built}
12613 The following attributes are defined for package @code{Naming}
12614 (@pxref{Naming Schemes}):
12616 @multitable @columnfractions .4 .2 .2 .2
12617 @item Attribute Name @tab Category @tab Index @tab Value
12618 @item @code{Spec_Suffix}
12619 @tab associative array
12622 @item @code{Body_Suffix}
12623 @tab associative array
12626 @item @code{Separate_Suffix}
12627 @tab simple attribute
12630 @item @code{Casing}
12631 @tab simple attribute
12634 @item @code{Dot_Replacement}
12635 @tab simple attribute
12639 @tab associative array
12643 @tab associative array
12646 @item @code{Specification_Exceptions}
12647 @tab associative array
12650 @item @code{Implementation_Exceptions}
12651 @tab associative array
12657 The following attributes are defined for packages @code{Builder},
12658 @code{Compiler}, @code{Binder},
12659 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12660 (@pxref{^Switches^Switches^ and Project Files}).
12662 @multitable @columnfractions .4 .2 .2 .2
12663 @item Attribute Name @tab Category @tab Index @tab Value
12664 @item @code{^Default_Switches^Default_Switches^}
12665 @tab associative array
12668 @item @code{^Switches^Switches^}
12669 @tab associative array
12675 In addition, package @code{Compiler} has a single string attribute
12676 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12677 string attribute @code{Global_Configuration_Pragmas}.
12680 Each simple attribute has a default value: the empty string (for string-valued
12681 attributes) and the empty list (for string list-valued attributes).
12683 An attribute declaration defines a new value for an attribute.
12685 Examples of simple attribute declarations:
12687 @smallexample @c projectfile
12688 for Object_Dir use "objects";
12689 for Source_Dirs use ("units", "test/drivers");
12693 The syntax of a @dfn{simple attribute declaration} is similar to that of an
12694 attribute definition clause in Ada.
12696 Attributes references may be appear in expressions.
12697 The general form for such a reference is @code{<entity>'<attribute>}:
12698 Associative array attributes are functions. Associative
12699 array attribute references must have an argument that is a string literal.
12703 @smallexample @c projectfile
12705 Naming'Dot_Replacement
12706 Imported_Project'Source_Dirs
12707 Imported_Project.Naming'Casing
12708 Builder'^Default_Switches^Default_Switches^("Ada")
12712 The prefix of an attribute may be:
12714 @item @code{project} for an attribute of the current project
12715 @item The name of an existing package of the current project
12716 @item The name of an imported project
12717 @item The name of a parent project that is extended by the current project
12718 @item An expanded name whose prefix is imported/parent project name,
12719 and whose selector is a package name
12724 @smallexample @c projectfile
12727 for Source_Dirs use project'Source_Dirs & "units";
12728 for Source_Dirs use project'Source_Dirs & "test/drivers"
12734 In the first attribute declaration, initially the attribute @code{Source_Dirs}
12735 has the default value: an empty string list. After this declaration,
12736 @code{Source_Dirs} is a string list of one element: @code{"units"}.
12737 After the second attribute declaration @code{Source_Dirs} is a string list of
12738 two elements: @code{"units"} and @code{"test/drivers"}.
12740 Note: this example is for illustration only. In practice,
12741 the project file would contain only one attribute declaration:
12743 @smallexample @c projectfile
12744 for Source_Dirs use ("units", "test/drivers");
12747 @node Associative Array Attributes
12748 @subsection Associative Array Attributes
12751 Some attributes are defined as @emph{associative arrays}. An associative
12752 array may be regarded as a function that takes a string as a parameter
12753 and delivers a string or string list value as its result.
12755 Here are some examples of single associative array attribute associations:
12757 @smallexample @c projectfile
12758 for Body ("main") use "Main.ada";
12759 for ^Switches^Switches^ ("main.ada")
12761 "^-gnatv^-gnatv^");
12762 for ^Switches^Switches^ ("main.ada")
12763 use Builder'^Switches^Switches^ ("main.ada")
12768 Like untyped variables and simple attributes, associative array attributes
12769 may be declared several times. Each declaration supplies a new value for the
12770 attribute, and replaces the previous setting.
12773 An associative array attribute may be declared as a full associative array
12774 declaration, with the value of the same attribute in an imported or extended
12777 @smallexample @c projectfile
12779 for Default_Switches use Default.Builder'Default_Switches;
12784 In this example, @code{Default} must be either a project imported by the
12785 current project, or the project that the current project extends. If the
12786 attribute is in a package (in this case, in package @code{Builder}), the same
12787 package needs to be specified.
12790 A full associative array declaration replaces any other declaration for the
12791 attribute, including other full associative array declaration. Single
12792 associative array associations may be declare after a full associative
12793 declaration, modifying the value for a single association of the attribute.
12795 @node case Constructions
12796 @subsection @code{case} Constructions
12799 A @code{case} construction is used in a project file to effect conditional
12801 Here is a typical example:
12803 @smallexample @c projectfile
12806 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
12808 OS : OS_Type := external ("OS", "GNU/Linux");
12812 package Compiler is
12814 when "GNU/Linux" | "Unix" =>
12815 for ^Default_Switches^Default_Switches^ ("Ada")
12816 use ("^-gnath^-gnath^");
12818 for ^Default_Switches^Default_Switches^ ("Ada")
12819 use ("^-gnatP^-gnatP^");
12828 The syntax of a @code{case} construction is based on the Ada case statement
12829 (although there is no @code{null} construction for empty alternatives).
12831 The case expression must be a typed string variable.
12832 Each alternative comprises the reserved word @code{when}, either a list of
12833 literal strings separated by the @code{"|"} character or the reserved word
12834 @code{others}, and the @code{"=>"} token.
12835 Each literal string must belong to the string type that is the type of the
12837 An @code{others} alternative, if present, must occur last.
12839 After each @code{=>}, there are zero or more constructions. The only
12840 constructions allowed in a case construction are other case constructions,
12841 attribute declarations and variable declarations. String type declarations and
12842 package declarations are not allowed. Variable declarations are restricted to
12843 variables that have already been declared before the case construction.
12845 The value of the case variable is often given by an external reference
12846 (@pxref{External References in Project Files}).
12848 @c ****************************************
12849 @c * Objects and Sources in Project Files *
12850 @c ****************************************
12852 @node Objects and Sources in Project Files
12853 @section Objects and Sources in Project Files
12856 * Object Directory::
12858 * Source Directories::
12859 * Source File Names::
12863 Each project has exactly one object directory and one or more source
12864 directories. The source directories must contain at least one source file,
12865 unless the project file explicitly specifies that no source files are present
12866 (@pxref{Source File Names}).
12868 @node Object Directory
12869 @subsection Object Directory
12872 The object directory for a project is the directory containing the compiler's
12873 output (such as @file{ALI} files and object files) for the project's immediate
12876 The object directory is given by the value of the attribute @code{Object_Dir}
12877 in the project file.
12879 @smallexample @c projectfile
12880 for Object_Dir use "objects";
12884 The attribute @code{Object_Dir} has a string value, the path name of the object
12885 directory. The path name may be absolute or relative to the directory of the
12886 project file. This directory must already exist, and be readable and writable.
12888 By default, when the attribute @code{Object_Dir} is not given an explicit value
12889 or when its value is the empty string, the object directory is the same as the
12890 directory containing the project file.
12892 @node Exec Directory
12893 @subsection Exec Directory
12896 The exec directory for a project is the directory containing the executables
12897 for the project's main subprograms.
12899 The exec directory is given by the value of the attribute @code{Exec_Dir}
12900 in the project file.
12902 @smallexample @c projectfile
12903 for Exec_Dir use "executables";
12907 The attribute @code{Exec_Dir} has a string value, the path name of the exec
12908 directory. The path name may be absolute or relative to the directory of the
12909 project file. This directory must already exist, and be writable.
12911 By default, when the attribute @code{Exec_Dir} is not given an explicit value
12912 or when its value is the empty string, the exec directory is the same as the
12913 object directory of the project file.
12915 @node Source Directories
12916 @subsection Source Directories
12919 The source directories of a project are specified by the project file
12920 attribute @code{Source_Dirs}.
12922 This attribute's value is a string list. If the attribute is not given an
12923 explicit value, then there is only one source directory, the one where the
12924 project file resides.
12926 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
12929 @smallexample @c projectfile
12930 for Source_Dirs use ();
12934 indicates that the project contains no source files.
12936 Otherwise, each string in the string list designates one or more
12937 source directories.
12939 @smallexample @c projectfile
12940 for Source_Dirs use ("sources", "test/drivers");
12944 If a string in the list ends with @code{"/**"}, then the directory whose path
12945 name precedes the two asterisks, as well as all its subdirectories
12946 (recursively), are source directories.
12948 @smallexample @c projectfile
12949 for Source_Dirs use ("/system/sources/**");
12953 Here the directory @code{/system/sources} and all of its subdirectories
12954 (recursively) are source directories.
12956 To specify that the source directories are the directory of the project file
12957 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
12958 @smallexample @c projectfile
12959 for Source_Dirs use ("./**");
12963 Each of the source directories must exist and be readable.
12965 @node Source File Names
12966 @subsection Source File Names
12969 In a project that contains source files, their names may be specified by the
12970 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
12971 (a string). Source file names never include any directory information.
12973 If the attribute @code{Source_Files} is given an explicit value, then each
12974 element of the list is a source file name.
12976 @smallexample @c projectfile
12977 for Source_Files use ("main.adb");
12978 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
12982 If the attribute @code{Source_Files} is not given an explicit value,
12983 but the attribute @code{Source_List_File} is given a string value,
12984 then the source file names are contained in the text file whose path name
12985 (absolute or relative to the directory of the project file) is the
12986 value of the attribute @code{Source_List_File}.
12988 Each line in the file that is not empty or is not a comment
12989 contains a source file name.
12991 @smallexample @c projectfile
12992 for Source_List_File use "source_list.txt";
12996 By default, if neither the attribute @code{Source_Files} nor the attribute
12997 @code{Source_List_File} is given an explicit value, then each file in the
12998 source directories that conforms to the project's naming scheme
12999 (@pxref{Naming Schemes}) is an immediate source of the project.
13001 A warning is issued if both attributes @code{Source_Files} and
13002 @code{Source_List_File} are given explicit values. In this case, the attribute
13003 @code{Source_Files} prevails.
13005 Each source file name must be the name of one existing source file
13006 in one of the source directories.
13008 A @code{Source_Files} attribute whose value is an empty list
13009 indicates that there are no source files in the project.
13011 If the order of the source directories is known statically, that is if
13012 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13013 be several files with the same source file name. In this case, only the file
13014 in the first directory is considered as an immediate source of the project
13015 file. If the order of the source directories is not known statically, it is
13016 an error to have several files with the same source file name.
13018 Projects can be specified to have no Ada source
13019 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
13020 list, or the @code{"Ada"} may be absent from @code{Languages}:
13022 @smallexample @c projectfile
13023 for Source_Dirs use ();
13024 for Source_Files use ();
13025 for Languages use ("C", "C++");
13029 Otherwise, a project must contain at least one immediate source.
13031 Projects with no source files are useful as template packages
13032 (@pxref{Packages in Project Files}) for other projects; in particular to
13033 define a package @code{Naming} (@pxref{Naming Schemes}).
13035 @c ****************************
13036 @c * Importing Projects *
13037 @c ****************************
13039 @node Importing Projects
13040 @section Importing Projects
13041 @cindex @code{ADA_PROJECT_PATH}
13044 An immediate source of a project P may depend on source files that
13045 are neither immediate sources of P nor in the predefined library.
13046 To get this effect, P must @emph{import} the projects that contain the needed
13049 @smallexample @c projectfile
13051 with "project1", "utilities.gpr";
13052 with "/namings/apex.gpr";
13059 As can be seen in this example, the syntax for importing projects is similar
13060 to the syntax for importing compilation units in Ada. However, project files
13061 use literal strings instead of names, and the @code{with} clause identifies
13062 project files rather than packages.
13064 Each literal string is the file name or path name (absolute or relative) of a
13065 project file. If a string corresponds to a file name, with no path or a
13066 relative path, then its location is determined by the @emph{project path}. The
13067 latter can be queried using @code{gnatls -v}. It contains:
13071 In first position, the directory containing the current project file.
13073 In last position, the default project directory. This default project directory
13074 is part of the GNAT installation and is the standard place to install project
13075 files giving access to standard support libraries.
13077 @ref{Installing a library}
13081 In between, all the directories referenced in the
13082 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13086 If a relative pathname is used, as in
13088 @smallexample @c projectfile
13093 then the full path for the project is constructed by concatenating this
13094 relative path to those in the project path, in order, until a matching file is
13095 found. Any symbolic link will be fully resolved in the directory of the
13096 importing project file before the imported project file is examined.
13098 If the @code{with}'ed project file name does not have an extension,
13099 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13100 then the file name as specified in the @code{with} clause (no extension) will
13101 be used. In the above example, if a file @code{project1.gpr} is found, then it
13102 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13103 then it will be used; if neither file exists, this is an error.
13105 A warning is issued if the name of the project file does not match the
13106 name of the project; this check is case insensitive.
13108 Any source file that is an immediate source of the imported project can be
13109 used by the immediate sources of the importing project, transitively. Thus
13110 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13111 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13112 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13113 because if and when @code{B} ceases to import @code{C}, some sources in
13114 @code{A} will no longer compile.
13116 A side effect of this capability is that normally cyclic dependencies are not
13117 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13118 is not allowed to import @code{A}. However, there are cases when cyclic
13119 dependencies would be beneficial. For these cases, another form of import
13120 between projects exists, the @code{limited with}: a project @code{A} that
13121 imports a project @code{B} with a straight @code{with} may also be imported,
13122 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13123 to @code{A} include at least one @code{limited with}.
13125 @smallexample @c 0projectfile
13131 limited with "../a/a.gpr";
13139 limited with "../a/a.gpr";
13145 In the above legal example, there are two project cycles:
13148 @item A -> C -> D -> A
13152 In each of these cycle there is one @code{limited with}: import of @code{A}
13153 from @code{B} and import of @code{A} from @code{D}.
13155 The difference between straight @code{with} and @code{limited with} is that
13156 the name of a project imported with a @code{limited with} cannot be used in the
13157 project that imports it. In particular, its packages cannot be renamed and
13158 its variables cannot be referred to.
13160 An exception to the above rules for @code{limited with} is that for the main
13161 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13162 @code{limited with} is equivalent to a straight @code{with}. For example,
13163 in the example above, projects @code{B} and @code{D} could not be main
13164 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13165 each have a @code{limited with} that is the only one in a cycle of importing
13168 @c *********************
13169 @c * Project Extension *
13170 @c *********************
13172 @node Project Extension
13173 @section Project Extension
13176 During development of a large system, it is sometimes necessary to use
13177 modified versions of some of the source files, without changing the original
13178 sources. This can be achieved through the @emph{project extension} facility.
13180 @smallexample @c projectfile
13181 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13185 A project extension declaration introduces an extending project
13186 (the @emph{child}) and a project being extended (the @emph{parent}).
13188 By default, a child project inherits all the sources of its parent.
13189 However, inherited sources can be overridden: a unit in a parent is hidden
13190 by a unit of the same name in the child.
13192 Inherited sources are considered to be sources (but not immediate sources)
13193 of the child project; see @ref{Project File Syntax}.
13195 An inherited source file retains any switches specified in the parent project.
13197 For example if the project @code{Utilities} contains the spec and the
13198 body of an Ada package @code{Util_IO}, then the project
13199 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13200 The original body of @code{Util_IO} will not be considered in program builds.
13201 However, the package spec will still be found in the project
13204 A child project can have only one parent, except when it is qualified as
13205 abstract. But it may import any number of other projects.
13207 A project is not allowed to import directly or indirectly at the same time a
13208 child project and any of its ancestors.
13210 @c *******************************
13211 @c * Project Hierarchy Extension *
13212 @c *******************************
13214 @node Project Hierarchy Extension
13215 @section Project Hierarchy Extension
13218 When extending a large system spanning multiple projects, it is often
13219 inconvenient to extend every project in the hierarchy that is impacted by a
13220 small change introduced. In such cases, it is possible to create a virtual
13221 extension of entire hierarchy using @code{extends all} relationship.
13223 When the project is extended using @code{extends all} inheritance, all projects
13224 that are imported by it, both directly and indirectly, are considered virtually
13225 extended. That is, the Project Manager creates "virtual projects"
13226 that extend every project in the hierarchy; all these virtual projects have
13227 no sources of their own and have as object directory the object directory of
13228 the root of "extending all" project.
13230 It is possible to explicitly extend one or more projects in the hierarchy
13231 in order to modify the sources. These extending projects must be imported by
13232 the "extending all" project, which will replace the corresponding virtual
13233 projects with the explicit ones.
13235 When building such a project hierarchy extension, the Project Manager will
13236 ensure that both modified sources and sources in virtual extending projects
13237 that depend on them, are recompiled.
13239 By means of example, consider the following hierarchy of projects.
13243 project A, containing package P1
13245 project B importing A and containing package P2 which depends on P1
13247 project C importing B and containing package P3 which depends on P2
13251 We want to modify packages P1 and P3.
13253 This project hierarchy will need to be extended as follows:
13257 Create project A1 that extends A, placing modified P1 there:
13259 @smallexample @c 0projectfile
13260 project A1 extends "(@dots{})/A" is
13265 Create project C1 that "extends all" C and imports A1, placing modified
13268 @smallexample @c 0projectfile
13269 with "(@dots{})/A1";
13270 project C1 extends all "(@dots{})/C" is
13275 When you build project C1, your entire modified project space will be
13276 recompiled, including the virtual project B1 that has been impacted by the
13277 "extending all" inheritance of project C.
13279 Note that if a Library Project in the hierarchy is virtually extended,
13280 the virtual project that extends the Library Project is not a Library Project.
13282 @c ****************************************
13283 @c * External References in Project Files *
13284 @c ****************************************
13286 @node External References in Project Files
13287 @section External References in Project Files
13290 A project file may contain references to external variables; such references
13291 are called @emph{external references}.
13293 An external variable is either defined as part of the environment (an
13294 environment variable in Unix, for example) or else specified on the command
13295 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13296 If both, then the command line value is used.
13298 The value of an external reference is obtained by means of the built-in
13299 function @code{external}, which returns a string value.
13300 This function has two forms:
13302 @item @code{external (external_variable_name)}
13303 @item @code{external (external_variable_name, default_value)}
13307 Each parameter must be a string literal. For example:
13309 @smallexample @c projectfile
13311 external ("OS", "GNU/Linux")
13315 In the form with one parameter, the function returns the value of
13316 the external variable given as parameter. If this name is not present in the
13317 environment, the function returns an empty string.
13319 In the form with two string parameters, the second argument is
13320 the value returned when the variable given as the first argument is not
13321 present in the environment. In the example above, if @code{"OS"} is not
13322 the name of ^an environment variable^a logical name^ and is not passed on
13323 the command line, then the returned value is @code{"GNU/Linux"}.
13325 An external reference may be part of a string expression or of a string
13326 list expression, and can therefore appear in a variable declaration or
13327 an attribute declaration.
13329 @smallexample @c projectfile
13331 type Mode_Type is ("Debug", "Release");
13332 Mode : Mode_Type := external ("MODE");
13339 @c *****************************
13340 @c * Packages in Project Files *
13341 @c *****************************
13343 @node Packages in Project Files
13344 @section Packages in Project Files
13347 A @emph{package} defines the settings for project-aware tools within a
13349 For each such tool one can declare a package; the names for these
13350 packages are preset (@pxref{Packages}).
13351 A package may contain variable declarations, attribute declarations, and case
13354 @smallexample @c projectfile
13357 package Builder is -- used by gnatmake
13358 for ^Default_Switches^Default_Switches^ ("Ada")
13367 The syntax of package declarations mimics that of package in Ada.
13369 Most of the packages have an attribute
13370 @code{^Default_Switches^Default_Switches^}.
13371 This attribute is an associative array, and its value is a string list.
13372 The index of the associative array is the name of a programming language (case
13373 insensitive). This attribute indicates the ^switch^switch^
13374 or ^switches^switches^ to be used
13375 with the corresponding tool.
13377 Some packages also have another attribute, @code{^Switches^Switches^},
13378 an associative array whose value is a string list.
13379 The index is the name of a source file.
13380 This attribute indicates the ^switch^switch^
13381 or ^switches^switches^ to be used by the corresponding
13382 tool when dealing with this specific file.
13384 Further information on these ^switch^switch^-related attributes is found in
13385 @ref{^Switches^Switches^ and Project Files}.
13387 A package may be declared as a @emph{renaming} of another package; e.g., from
13388 the project file for an imported project.
13390 @smallexample @c projectfile
13392 with "/global/apex.gpr";
13394 package Naming renames Apex.Naming;
13401 Packages that are renamed in other project files often come from project files
13402 that have no sources: they are just used as templates. Any modification in the
13403 template will be reflected automatically in all the project files that rename
13404 a package from the template.
13406 In addition to the tool-oriented packages, you can also declare a package
13407 named @code{Naming} to establish specialized source file naming conventions
13408 (@pxref{Naming Schemes}).
13410 @c ************************************
13411 @c * Variables from Imported Projects *
13412 @c ************************************
13414 @node Variables from Imported Projects
13415 @section Variables from Imported Projects
13418 An attribute or variable defined in an imported or parent project can
13419 be used in expressions in the importing / extending project.
13420 Such an attribute or variable is denoted by an expanded name whose prefix
13421 is either the name of the project or the expanded name of a package within
13424 @smallexample @c projectfile
13427 project Main extends "base" is
13428 Var1 := Imported.Var;
13429 Var2 := Base.Var & ".new";
13434 for ^Default_Switches^Default_Switches^ ("Ada")
13435 use Imported.Builder'Ada_^Switches^Switches^ &
13436 "^-gnatg^-gnatg^" &
13442 package Compiler is
13443 for ^Default_Switches^Default_Switches^ ("Ada")
13444 use Base.Compiler'Ada_^Switches^Switches^;
13455 The value of @code{Var1} is a copy of the variable @code{Var} defined
13456 in the project file @file{"imported.gpr"}
13458 the value of @code{Var2} is a copy of the value of variable @code{Var}
13459 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13461 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13462 @code{Builder} is a string list that includes in its value a copy of the value
13463 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13464 in project file @file{imported.gpr} plus two new elements:
13465 @option{"^-gnatg^-gnatg^"}
13466 and @option{"^-v^-v^"};
13468 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13469 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13470 defined in the @code{Compiler} package in project file @file{base.gpr},
13471 the project being extended.
13474 @c ******************
13475 @c * Naming Schemes *
13476 @c ******************
13478 @node Naming Schemes
13479 @section Naming Schemes
13482 Sometimes an Ada software system is ported from a foreign compilation
13483 environment to GNAT, and the file names do not use the default GNAT
13484 conventions. Instead of changing all the file names (which for a variety
13485 of reasons might not be possible), you can define the relevant file
13486 naming scheme in the @code{Naming} package in your project file.
13489 Note that the use of pragmas described in
13490 @ref{Alternative File Naming Schemes} by mean of a configuration
13491 pragmas file is not supported when using project files. You must use
13492 the features described in this paragraph. You can however use specify
13493 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13496 For example, the following
13497 package models the Apex file naming rules:
13499 @smallexample @c projectfile
13502 for Casing use "lowercase";
13503 for Dot_Replacement use ".";
13504 for Spec_Suffix ("Ada") use ".1.ada";
13505 for Body_Suffix ("Ada") use ".2.ada";
13512 For example, the following package models the HP Ada file naming rules:
13514 @smallexample @c projectfile
13517 for Casing use "lowercase";
13518 for Dot_Replacement use "__";
13519 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13520 for Body_Suffix ("Ada") use ".^ada^ada^";
13526 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13527 names in lower case)
13531 You can define the following attributes in package @code{Naming}:
13535 @item @code{Casing}
13536 This must be a string with one of the three values @code{"lowercase"},
13537 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13540 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13542 @item @code{Dot_Replacement}
13543 This must be a string whose value satisfies the following conditions:
13546 @item It must not be empty
13547 @item It cannot start or end with an alphanumeric character
13548 @item It cannot be a single underscore
13549 @item It cannot start with an underscore followed by an alphanumeric
13550 @item It cannot contain a dot @code{'.'} except if the entire string
13555 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13557 @item @code{Spec_Suffix}
13558 This is an associative array (indexed by the programming language name, case
13559 insensitive) whose value is a string that must satisfy the following
13563 @item It must not be empty
13564 @item It must include at least one dot
13567 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13568 @code{"^.ads^.ADS^"}.
13570 @item @code{Body_Suffix}
13571 This is an associative array (indexed by the programming language name, case
13572 insensitive) whose value is a string that must satisfy the following
13576 @item It must not be empty
13577 @item It must include at least one dot
13578 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13581 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13582 same string, then a file name that ends with the longest of these two suffixes
13583 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13584 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13586 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13587 @code{"^.adb^.ADB^"}.
13589 @item @code{Separate_Suffix}
13590 This must be a string whose value satisfies the same conditions as
13591 @code{Body_Suffix}. The same "longest suffix" rules apply.
13594 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13595 value as @code{Body_Suffix ("Ada")}.
13599 You can use the associative array attribute @code{Spec} to define
13600 the source file name for an individual Ada compilation unit's spec. The array
13601 index must be a string literal that identifies the Ada unit (case insensitive).
13602 The value of this attribute must be a string that identifies the file that
13603 contains this unit's spec (case sensitive or insensitive depending on the
13606 @smallexample @c projectfile
13607 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13612 You can use the associative array attribute @code{Body} to
13613 define the source file name for an individual Ada compilation unit's body
13614 (possibly a subunit). The array index must be a string literal that identifies
13615 the Ada unit (case insensitive). The value of this attribute must be a string
13616 that identifies the file that contains this unit's body or subunit (case
13617 sensitive or insensitive depending on the operating system).
13619 @smallexample @c projectfile
13620 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13624 @c ********************
13625 @c * Library Projects *
13626 @c ********************
13628 @node Library Projects
13629 @section Library Projects
13632 @emph{Library projects} are projects whose object code is placed in a library.
13633 (Note that this facility is not yet supported on all platforms)
13635 To create a library project, you need to define in its project file
13636 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13637 Additionally, you may define other library-related attributes such as
13638 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13639 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13641 The @code{Library_Name} attribute has a string value. There is no restriction
13642 on the name of a library. It is the responsibility of the developer to
13643 choose a name that will be accepted by the platform. It is recommended to
13644 choose names that could be Ada identifiers; such names are almost guaranteed
13645 to be acceptable on all platforms.
13647 The @code{Library_Dir} attribute has a string value that designates the path
13648 (absolute or relative) of the directory where the library will reside.
13649 It must designate an existing directory, and this directory must be writable,
13650 different from the project's object directory and from any source directory
13651 in the project tree.
13653 If both @code{Library_Name} and @code{Library_Dir} are specified and
13654 are legal, then the project file defines a library project. The optional
13655 library-related attributes are checked only for such project files.
13657 The @code{Library_Kind} attribute has a string value that must be one of the
13658 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13659 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13660 attribute is not specified, the library is a static library, that is
13661 an archive of object files that can be potentially linked into a
13662 static executable. Otherwise, the library may be dynamic or
13663 relocatable, that is a library that is loaded only at the start of execution.
13665 If you need to build both a static and a dynamic library, you should use two
13666 different object directories, since in some cases some extra code needs to
13667 be generated for the latter. For such cases, it is recommended to either use
13668 two different project files, or a single one which uses external variables
13669 to indicate what kind of library should be build.
13671 The @code{Library_ALI_Dir} attribute may be specified to indicate the
13672 directory where the ALI files of the library will be copied. When it is
13673 not specified, the ALI files are copied to the directory specified in
13674 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
13675 must be writable and different from the project's object directory and from
13676 any source directory in the project tree.
13678 The @code{Library_Version} attribute has a string value whose interpretation
13679 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
13680 used only for dynamic/relocatable libraries as the internal name of the
13681 library (the @code{"soname"}). If the library file name (built from the
13682 @code{Library_Name}) is different from the @code{Library_Version}, then the
13683 library file will be a symbolic link to the actual file whose name will be
13684 @code{Library_Version}.
13688 @smallexample @c projectfile
13694 for Library_Dir use "lib_dir";
13695 for Library_Name use "dummy";
13696 for Library_Kind use "relocatable";
13697 for Library_Version use "libdummy.so." & Version;
13704 Directory @file{lib_dir} will contain the internal library file whose name
13705 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
13706 @file{libdummy.so.1}.
13708 When @command{gnatmake} detects that a project file
13709 is a library project file, it will check all immediate sources of the project
13710 and rebuild the library if any of the sources have been recompiled.
13712 Standard project files can import library project files. In such cases,
13713 the libraries will only be rebuilt if some of its sources are recompiled
13714 because they are in the closure of some other source in an importing project.
13715 Sources of the library project files that are not in such a closure will
13716 not be checked, unless the full library is checked, because one of its sources
13717 needs to be recompiled.
13719 For instance, assume the project file @code{A} imports the library project file
13720 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
13721 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
13722 @file{l2.ads}, @file{l2.adb}.
13724 If @file{l1.adb} has been modified, then the library associated with @code{L}
13725 will be rebuilt when compiling all the immediate sources of @code{A} only
13726 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
13729 To be sure that all the sources in the library associated with @code{L} are
13730 up to date, and that all the sources of project @code{A} are also up to date,
13731 the following two commands needs to be used:
13738 When a library is built or rebuilt, an attempt is made first to delete all
13739 files in the library directory.
13740 All @file{ALI} files will also be copied from the object directory to the
13741 library directory. To build executables, @command{gnatmake} will use the
13742 library rather than the individual object files.
13745 It is also possible to create library project files for third-party libraries
13746 that are precompiled and cannot be compiled locally thanks to the
13747 @code{externally_built} attribute. (See @ref{Installing a library}).
13750 @c *******************************
13751 @c * Stand-alone Library Projects *
13752 @c *******************************
13754 @node Stand-alone Library Projects
13755 @section Stand-alone Library Projects
13758 A Stand-alone Library is a library that contains the necessary code to
13759 elaborate the Ada units that are included in the library. A Stand-alone
13760 Library is suitable to be used in an executable when the main is not
13761 in Ada. However, Stand-alone Libraries may also be used with an Ada main
13764 A Stand-alone Library Project is a Library Project where the library is
13765 a Stand-alone Library.
13767 To be a Stand-alone Library Project, in addition to the two attributes
13768 that make a project a Library Project (@code{Library_Name} and
13769 @code{Library_Dir}, see @ref{Library Projects}), the attribute
13770 @code{Library_Interface} must be defined.
13772 @smallexample @c projectfile
13774 for Library_Dir use "lib_dir";
13775 for Library_Name use "dummy";
13776 for Library_Interface use ("int1", "int1.child");
13780 Attribute @code{Library_Interface} has a nonempty string list value,
13781 each string in the list designating a unit contained in an immediate source
13782 of the project file.
13784 When a Stand-alone Library is built, first the binder is invoked to build
13785 a package whose name depends on the library name
13786 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
13787 This binder-generated package includes initialization and
13788 finalization procedures whose
13789 names depend on the library name (dummyinit and dummyfinal in the example
13790 above). The object corresponding to this package is included in the library.
13792 A dynamic or relocatable Stand-alone Library is automatically initialized
13793 if automatic initialization of Stand-alone Libraries is supported on the
13794 platform and if attribute @code{Library_Auto_Init} is not specified or
13795 is specified with the value "true". A static Stand-alone Library is never
13796 automatically initialized.
13798 Single string attribute @code{Library_Auto_Init} may be specified with only
13799 two possible values: "false" or "true" (case-insensitive). Specifying
13800 "false" for attribute @code{Library_Auto_Init} will prevent automatic
13801 initialization of dynamic or relocatable libraries.
13803 When a non-automatically initialized Stand-alone Library is used
13804 in an executable, its initialization procedure must be called before
13805 any service of the library is used.
13806 When the main subprogram is in Ada, it may mean that the initialization
13807 procedure has to be called during elaboration of another package.
13809 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
13810 (those that are listed in attribute @code{Library_Interface}) are copied to
13811 the Library Directory. As a consequence, only the Interface Units may be
13812 imported from Ada units outside of the library. If other units are imported,
13813 the binding phase will fail.
13815 When a Stand-Alone Library is bound, the switches that are specified in
13816 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
13817 used in the call to @command{gnatbind}.
13819 The string list attribute @code{Library_Options} may be used to specified
13820 additional switches to the call to @command{gcc} to link the library.
13822 The attribute @code{Library_Src_Dir}, may be specified for a
13823 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
13824 single string value. Its value must be the path (absolute or relative to the
13825 project directory) of an existing directory. This directory cannot be the
13826 object directory or one of the source directories, but it can be the same as
13827 the library directory. The sources of the Interface
13828 Units of the library, necessary to an Ada client of the library, will be
13829 copied to the designated directory, called Interface Copy directory.
13830 These sources includes the specs of the Interface Units, but they may also
13831 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
13832 are used, or when there is a generic units in the spec. Before the sources
13833 are copied to the Interface Copy directory, an attempt is made to delete all
13834 files in the Interface Copy directory.
13836 @c *************************************
13837 @c * Switches Related to Project Files *
13838 @c *************************************
13839 @node Switches Related to Project Files
13840 @section Switches Related to Project Files
13843 The following switches are used by GNAT tools that support project files:
13847 @item ^-P^/PROJECT_FILE=^@var{project}
13848 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
13849 Indicates the name of a project file. This project file will be parsed with
13850 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
13851 if any, and using the external references indicated
13852 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
13854 There may zero, one or more spaces between @option{-P} and @var{project}.
13858 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
13861 Since the Project Manager parses the project file only after all the switches
13862 on the command line are checked, the order of the switches
13863 @option{^-P^/PROJECT_FILE^},
13864 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
13865 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
13867 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
13868 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
13869 Indicates that external variable @var{name} has the value @var{value}.
13870 The Project Manager will use this value for occurrences of
13871 @code{external(name)} when parsing the project file.
13875 If @var{name} or @var{value} includes a space, then @var{name=value} should be
13876 put between quotes.
13884 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
13885 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
13886 @var{name}, only the last one is used.
13889 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
13890 takes precedence over the value of the same name in the environment.
13892 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
13893 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
13894 Indicates the verbosity of the parsing of GNAT project files.
13897 @option{-vP0} means Default;
13898 @option{-vP1} means Medium;
13899 @option{-vP2} means High.
13903 There are three possible options for this qualifier: DEFAULT, MEDIUM and
13908 The default is ^Default^DEFAULT^: no output for syntactically correct
13911 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
13912 only the last one is used.
13914 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
13915 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
13916 Add directory <dir> at the beginning of the project search path, in order,
13917 after the current working directory.
13921 @cindex @option{-eL} (any project-aware tool)
13922 Follow all symbolic links when processing project files.
13925 @item ^--subdirs^/SUBDIRS^=<subdir>
13926 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
13927 This switch is recognized by gnatmake and gnatclean. It indicate that the real
13928 directories (except the source directories) are the subdirectories <subdir>
13929 of the directories specified in the project files. This applies in particular
13930 to object directories, library directories and exec directories. If the
13931 subdirectories do not exist, they are created automatically.
13935 @c **********************************
13936 @c * Tools Supporting Project Files *
13937 @c **********************************
13939 @node Tools Supporting Project Files
13940 @section Tools Supporting Project Files
13943 * gnatmake and Project Files::
13944 * The GNAT Driver and Project Files::
13947 @node gnatmake and Project Files
13948 @subsection gnatmake and Project Files
13951 This section covers several topics related to @command{gnatmake} and
13952 project files: defining ^switches^switches^ for @command{gnatmake}
13953 and for the tools that it invokes; specifying configuration pragmas;
13954 the use of the @code{Main} attribute; building and rebuilding library project
13958 * ^Switches^Switches^ and Project Files::
13959 * Specifying Configuration Pragmas::
13960 * Project Files and Main Subprograms::
13961 * Library Project Files::
13964 @node ^Switches^Switches^ and Project Files
13965 @subsubsection ^Switches^Switches^ and Project Files
13968 It is not currently possible to specify VMS style qualifiers in the project
13969 files; only Unix style ^switches^switches^ may be specified.
13973 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
13974 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
13975 attribute, a @code{^Switches^Switches^} attribute, or both;
13976 as their names imply, these ^switch^switch^-related
13977 attributes affect the ^switches^switches^ that are used for each of these GNAT
13979 @command{gnatmake} is invoked. As will be explained below, these
13980 component-specific ^switches^switches^ precede
13981 the ^switches^switches^ provided on the @command{gnatmake} command line.
13983 The @code{^Default_Switches^Default_Switches^} attribute is an associative
13984 array indexed by language name (case insensitive) whose value is a string list.
13987 @smallexample @c projectfile
13989 package Compiler is
13990 for ^Default_Switches^Default_Switches^ ("Ada")
13991 use ("^-gnaty^-gnaty^",
13998 The @code{^Switches^Switches^} attribute is also an associative array,
13999 indexed by a file name (which may or may not be case sensitive, depending
14000 on the operating system) whose value is a string list. For example:
14002 @smallexample @c projectfile
14005 for ^Switches^Switches^ ("main1.adb")
14007 for ^Switches^Switches^ ("main2.adb")
14014 For the @code{Builder} package, the file names must designate source files
14015 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14016 file names must designate @file{ALI} or source files for main subprograms.
14017 In each case just the file name without an explicit extension is acceptable.
14019 For each tool used in a program build (@command{gnatmake}, the compiler, the
14020 binder, and the linker), the corresponding package @dfn{contributes} a set of
14021 ^switches^switches^ for each file on which the tool is invoked, based on the
14022 ^switch^switch^-related attributes defined in the package.
14023 In particular, the ^switches^switches^
14024 that each of these packages contributes for a given file @var{f} comprise:
14028 the value of attribute @code{^Switches^Switches^ (@var{f})},
14029 if it is specified in the package for the given file,
14031 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14032 if it is specified in the package.
14036 If neither of these attributes is defined in the package, then the package does
14037 not contribute any ^switches^switches^ for the given file.
14039 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14040 two sets, in the following order: those contributed for the file
14041 by the @code{Builder} package;
14042 and the switches passed on the command line.
14044 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14045 the ^switches^switches^ passed to the tool comprise three sets,
14046 in the following order:
14050 the applicable ^switches^switches^ contributed for the file
14051 by the @code{Builder} package in the project file supplied on the command line;
14054 those contributed for the file by the package (in the relevant project file --
14055 see below) corresponding to the tool; and
14058 the applicable switches passed on the command line.
14062 The term @emph{applicable ^switches^switches^} reflects the fact that
14063 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14064 tools, depending on the individual ^switch^switch^.
14066 @command{gnatmake} may invoke the compiler on source files from different
14067 projects. The Project Manager will use the appropriate project file to
14068 determine the @code{Compiler} package for each source file being compiled.
14069 Likewise for the @code{Binder} and @code{Linker} packages.
14071 As an example, consider the following package in a project file:
14073 @smallexample @c projectfile
14076 package Compiler is
14077 for ^Default_Switches^Default_Switches^ ("Ada")
14079 for ^Switches^Switches^ ("a.adb")
14081 for ^Switches^Switches^ ("b.adb")
14083 "^-gnaty^-gnaty^");
14090 If @command{gnatmake} is invoked with this project file, and it needs to
14091 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14092 @file{a.adb} will be compiled with the ^switch^switch^
14093 @option{^-O1^-O1^},
14094 @file{b.adb} with ^switches^switches^
14096 and @option{^-gnaty^-gnaty^},
14097 and @file{c.adb} with @option{^-g^-g^}.
14099 The following example illustrates the ordering of the ^switches^switches^
14100 contributed by different packages:
14102 @smallexample @c projectfile
14106 for ^Switches^Switches^ ("main.adb")
14114 package Compiler is
14115 for ^Switches^Switches^ ("main.adb")
14123 If you issue the command:
14126 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14130 then the compiler will be invoked on @file{main.adb} with the following
14131 sequence of ^switches^switches^
14134 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14137 with the last @option{^-O^-O^}
14138 ^switch^switch^ having precedence over the earlier ones;
14139 several other ^switches^switches^
14140 (such as @option{^-c^-c^}) are added implicitly.
14142 The ^switches^switches^
14144 and @option{^-O1^-O1^} are contributed by package
14145 @code{Builder}, @option{^-O2^-O2^} is contributed
14146 by the package @code{Compiler}
14147 and @option{^-O0^-O0^} comes from the command line.
14149 The @option{^-g^-g^}
14150 ^switch^switch^ will also be passed in the invocation of
14151 @command{Gnatlink.}
14153 A final example illustrates switch contributions from packages in different
14156 @smallexample @c projectfile
14159 for Source_Files use ("pack.ads", "pack.adb");
14160 package Compiler is
14161 for ^Default_Switches^Default_Switches^ ("Ada")
14162 use ("^-gnata^-gnata^");
14170 for Source_Files use ("foo_main.adb", "bar_main.adb");
14172 for ^Switches^Switches^ ("foo_main.adb")
14180 -- Ada source file:
14182 procedure Foo_Main is
14190 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14194 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14195 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14196 @option{^-gnato^-gnato^} (passed on the command line).
14197 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14198 are @option{^-g^-g^} from @code{Proj4.Builder},
14199 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14200 and @option{^-gnato^-gnato^} from the command line.
14203 When using @command{gnatmake} with project files, some ^switches^switches^ or
14204 arguments may be expressed as relative paths. As the working directory where
14205 compilation occurs may change, these relative paths are converted to absolute
14206 paths. For the ^switches^switches^ found in a project file, the relative paths
14207 are relative to the project file directory, for the switches on the command
14208 line, they are relative to the directory where @command{gnatmake} is invoked.
14209 The ^switches^switches^ for which this occurs are:
14215 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14217 ^-o^-o^, object files specified in package @code{Linker} or after
14218 -largs on the command line). The exception to this rule is the ^switch^switch^
14219 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14221 @node Specifying Configuration Pragmas
14222 @subsubsection Specifying Configuration Pragmas
14224 When using @command{gnatmake} with project files, if there exists a file
14225 @file{gnat.adc} that contains configuration pragmas, this file will be
14228 Configuration pragmas can be defined by means of the following attributes in
14229 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14230 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14232 Both these attributes are single string attributes. Their values is the path
14233 name of a file containing configuration pragmas. If a path name is relative,
14234 then it is relative to the project directory of the project file where the
14235 attribute is defined.
14237 When compiling a source, the configuration pragmas used are, in order,
14238 those listed in the file designated by attribute
14239 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14240 project file, if it is specified, and those listed in the file designated by
14241 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14242 the project file of the source, if it exists.
14244 @node Project Files and Main Subprograms
14245 @subsubsection Project Files and Main Subprograms
14248 When using a project file, you can invoke @command{gnatmake}
14249 with one or several main subprograms, by specifying their source files on the
14253 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14257 Each of these needs to be a source file of the same project, except
14258 when the switch ^-u^/UNIQUE^ is used.
14261 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14262 same project, one of the project in the tree rooted at the project specified
14263 on the command line. The package @code{Builder} of this common project, the
14264 "main project" is the one that is considered by @command{gnatmake}.
14267 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14268 imported directly or indirectly by the project specified on the command line.
14269 Note that if such a source file is not part of the project specified on the
14270 command line, the ^switches^switches^ found in package @code{Builder} of the
14271 project specified on the command line, if any, that are transmitted
14272 to the compiler will still be used, not those found in the project file of
14276 When using a project file, you can also invoke @command{gnatmake} without
14277 explicitly specifying any main, and the effect depends on whether you have
14278 defined the @code{Main} attribute. This attribute has a string list value,
14279 where each element in the list is the name of a source file (the file
14280 extension is optional) that contains a unit that can be a main subprogram.
14282 If the @code{Main} attribute is defined in a project file as a non-empty
14283 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14284 line, then invoking @command{gnatmake} with this project file but without any
14285 main on the command line is equivalent to invoking @command{gnatmake} with all
14286 the file names in the @code{Main} attribute on the command line.
14289 @smallexample @c projectfile
14292 for Main use ("main1", "main2", "main3");
14298 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14300 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14302 When the project attribute @code{Main} is not specified, or is specified
14303 as an empty string list, or when the switch @option{-u} is used on the command
14304 line, then invoking @command{gnatmake} with no main on the command line will
14305 result in all immediate sources of the project file being checked, and
14306 potentially recompiled. Depending on the presence of the switch @option{-u},
14307 sources from other project files on which the immediate sources of the main
14308 project file depend are also checked and potentially recompiled. In other
14309 words, the @option{-u} switch is applied to all of the immediate sources of the
14312 When no main is specified on the command line and attribute @code{Main} exists
14313 and includes several mains, or when several mains are specified on the
14314 command line, the default ^switches^switches^ in package @code{Builder} will
14315 be used for all mains, even if there are specific ^switches^switches^
14316 specified for one or several mains.
14318 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14319 the specific ^switches^switches^ for each main, if they are specified.
14321 @node Library Project Files
14322 @subsubsection Library Project Files
14325 When @command{gnatmake} is invoked with a main project file that is a library
14326 project file, it is not allowed to specify one or more mains on the command
14330 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14331 ^-l^/ACTION=LINK^ have special meanings.
14334 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14335 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14338 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14339 to @command{gnatmake} that the binder generated file should be compiled
14340 (in the case of a stand-alone library) and that the library should be built.
14344 @node The GNAT Driver and Project Files
14345 @subsection The GNAT Driver and Project Files
14348 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14349 can benefit from project files:
14350 @command{^gnatbind^gnatbind^},
14351 @command{^gnatcheck^gnatcheck^}),
14352 @command{^gnatclean^gnatclean^}),
14353 @command{^gnatelim^gnatelim^},
14354 @command{^gnatfind^gnatfind^},
14355 @command{^gnatlink^gnatlink^},
14356 @command{^gnatls^gnatls^},
14357 @command{^gnatmetric^gnatmetric^},
14358 @command{^gnatpp^gnatpp^},
14359 @command{^gnatstub^gnatstub^},
14360 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14361 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14362 They must be invoked through the @command{gnat} driver.
14364 The @command{gnat} driver is a wrapper that accepts a number of commands and
14365 calls the corresponding tool. It was designed initially for VMS platforms (to
14366 convert VMS qualifiers to Unix-style switches), but it is now available on all
14369 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14370 (case insensitive):
14374 BIND to invoke @command{^gnatbind^gnatbind^}
14376 CHOP to invoke @command{^gnatchop^gnatchop^}
14378 CLEAN to invoke @command{^gnatclean^gnatclean^}
14380 COMP or COMPILE to invoke the compiler
14382 ELIM to invoke @command{^gnatelim^gnatelim^}
14384 FIND to invoke @command{^gnatfind^gnatfind^}
14386 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14388 LINK to invoke @command{^gnatlink^gnatlink^}
14390 LS or LIST to invoke @command{^gnatls^gnatls^}
14392 MAKE to invoke @command{^gnatmake^gnatmake^}
14394 NAME to invoke @command{^gnatname^gnatname^}
14396 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14398 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14400 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14402 STUB to invoke @command{^gnatstub^gnatstub^}
14404 XREF to invoke @command{^gnatxref^gnatxref^}
14408 (note that the compiler is invoked using the command
14409 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14412 On non-VMS platforms, between @command{gnat} and the command, two
14413 special switches may be used:
14417 @command{-v} to display the invocation of the tool.
14419 @command{-dn} to prevent the @command{gnat} driver from removing
14420 the temporary files it has created. These temporary files are
14421 configuration files and temporary file list files.
14425 The command may be followed by switches and arguments for the invoked
14429 gnat bind -C main.ali
14435 Switches may also be put in text files, one switch per line, and the text
14436 files may be specified with their path name preceded by '@@'.
14439 gnat bind @@args.txt main.ali
14443 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14444 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14445 (@option{^-P^/PROJECT_FILE^},
14446 @option{^-X^/EXTERNAL_REFERENCE^} and
14447 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14448 the switches of the invoking tool.
14451 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14452 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14453 the immediate sources of the specified project file.
14456 When GNAT METRIC is used with a project file, but with no source
14457 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14458 with all the immediate sources of the specified project file and with
14459 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14463 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14464 a project file, no source is specified on the command line and
14465 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14466 the underlying tool (^gnatpp^gnatpp^ or
14467 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14468 not only for the immediate sources of the main project.
14470 (-U stands for Universal or Union of the project files of the project tree)
14474 For each of the following commands, there is optionally a corresponding
14475 package in the main project.
14479 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14482 package @code{Check} for command CHECK (invoking
14483 @code{^gnatcheck^gnatcheck^})
14486 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14489 package @code{Cross_Reference} for command XREF (invoking
14490 @code{^gnatxref^gnatxref^})
14493 package @code{Eliminate} for command ELIM (invoking
14494 @code{^gnatelim^gnatelim^})
14497 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14500 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14503 package @code{Gnatstub} for command STUB
14504 (invoking @code{^gnatstub^gnatstub^})
14507 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14510 package @code{Metrics} for command METRIC
14511 (invoking @code{^gnatmetric^gnatmetric^})
14514 package @code{Pretty_Printer} for command PP or PRETTY
14515 (invoking @code{^gnatpp^gnatpp^})
14520 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14521 a simple variable with a string list value. It contains ^switches^switches^
14522 for the invocation of @code{^gnatls^gnatls^}.
14524 @smallexample @c projectfile
14528 for ^Switches^Switches^
14537 All other packages have two attribute @code{^Switches^Switches^} and
14538 @code{^Default_Switches^Default_Switches^}.
14541 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14542 source file name, that has a string list value: the ^switches^switches^ to be
14543 used when the tool corresponding to the package is invoked for the specific
14547 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14548 indexed by the programming language that has a string list value.
14549 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14550 ^switches^switches^ for the invocation of the tool corresponding
14551 to the package, except if a specific @code{^Switches^Switches^} attribute
14552 is specified for the source file.
14554 @smallexample @c projectfile
14558 for Source_Dirs use ("./**");
14561 for ^Switches^Switches^ use
14568 package Compiler is
14569 for ^Default_Switches^Default_Switches^ ("Ada")
14570 use ("^-gnatv^-gnatv^",
14571 "^-gnatwa^-gnatwa^");
14577 for ^Default_Switches^Default_Switches^ ("Ada")
14585 for ^Default_Switches^Default_Switches^ ("Ada")
14587 for ^Switches^Switches^ ("main.adb")
14596 for ^Default_Switches^Default_Switches^ ("Ada")
14603 package Cross_Reference is
14604 for ^Default_Switches^Default_Switches^ ("Ada")
14609 end Cross_Reference;
14615 With the above project file, commands such as
14618 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14619 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14620 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14621 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14622 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14626 will set up the environment properly and invoke the tool with the switches
14627 found in the package corresponding to the tool:
14628 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14629 except @code{^Switches^Switches^ ("main.adb")}
14630 for @code{^gnatlink^gnatlink^}.
14631 It is also possible to invoke some of the tools,
14632 @code{^gnatcheck^gnatcheck^}),
14633 @code{^gnatmetric^gnatmetric^}),
14634 and @code{^gnatpp^gnatpp^})
14635 on a set of project units thanks to the combination of the switches
14636 @option{-P}, @option{-U} and possibly the main unit when one is interested
14637 in its closure. For instance,
14641 will compute the metrics for all the immediate units of project
14644 gnat metric -Pproj -U
14646 will compute the metrics for all the units of the closure of projects
14647 rooted at @code{proj}.
14649 gnat metric -Pproj -U main_unit
14651 will compute the metrics for the closure of units rooted at
14652 @code{main_unit}. This last possibility relies implicitly
14653 on @command{gnatbind}'s option @option{-R}.
14655 @c **********************
14656 @node An Extended Example
14657 @section An Extended Example
14660 Suppose that we have two programs, @var{prog1} and @var{prog2},
14661 whose sources are in corresponding directories. We would like
14662 to build them with a single @command{gnatmake} command, and we want to place
14663 their object files into @file{build} subdirectories of the source directories.
14664 Furthermore, we want to have to have two separate subdirectories
14665 in @file{build} -- @file{release} and @file{debug} -- which will contain
14666 the object files compiled with different set of compilation flags.
14668 In other words, we have the following structure:
14685 Here are the project files that we must place in a directory @file{main}
14686 to maintain this structure:
14690 @item We create a @code{Common} project with a package @code{Compiler} that
14691 specifies the compilation ^switches^switches^:
14696 @b{project} Common @b{is}
14698 @b{for} Source_Dirs @b{use} (); -- No source files
14702 @b{type} Build_Type @b{is} ("release", "debug");
14703 Build : Build_Type := External ("BUILD", "debug");
14706 @b{package} Compiler @b{is}
14707 @b{case} Build @b{is}
14708 @b{when} "release" =>
14709 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14710 @b{use} ("^-O2^-O2^");
14711 @b{when} "debug" =>
14712 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
14713 @b{use} ("^-g^-g^");
14721 @item We create separate projects for the two programs:
14728 @b{project} Prog1 @b{is}
14730 @b{for} Source_Dirs @b{use} ("prog1");
14731 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
14733 @b{package} Compiler @b{renames} Common.Compiler;
14744 @b{project} Prog2 @b{is}
14746 @b{for} Source_Dirs @b{use} ("prog2");
14747 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
14749 @b{package} Compiler @b{renames} Common.Compiler;
14755 @item We create a wrapping project @code{Main}:
14764 @b{project} Main @b{is}
14766 @b{package} Compiler @b{renames} Common.Compiler;
14772 @item Finally we need to create a dummy procedure that @code{with}s (either
14773 explicitly or implicitly) all the sources of our two programs.
14778 Now we can build the programs using the command
14781 gnatmake ^-P^/PROJECT_FILE=^main dummy
14785 for the Debug mode, or
14789 gnatmake -Pmain -XBUILD=release
14795 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
14800 for the Release mode.
14802 @c ********************************
14803 @c * Project File Complete Syntax *
14804 @c ********************************
14806 @node Project File Complete Syntax
14807 @section Project File Complete Syntax
14811 context_clause project_declaration
14817 @b{with} path_name @{ , path_name @} ;
14822 project_declaration ::=
14823 simple_project_declaration | project_extension
14825 simple_project_declaration ::=
14826 @b{project} <project_>simple_name @b{is}
14827 @{declarative_item@}
14828 @b{end} <project_>simple_name;
14830 project_extension ::=
14831 @b{project} <project_>simple_name @b{extends} path_name @b{is}
14832 @{declarative_item@}
14833 @b{end} <project_>simple_name;
14835 declarative_item ::=
14836 package_declaration |
14837 typed_string_declaration |
14838 other_declarative_item
14840 package_declaration ::=
14841 package_spec | package_renaming
14844 @b{package} package_identifier @b{is}
14845 @{simple_declarative_item@}
14846 @b{end} package_identifier ;
14848 package_identifier ::=
14849 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
14850 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
14851 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
14853 package_renaming ::==
14854 @b{package} package_identifier @b{renames}
14855 <project_>simple_name.package_identifier ;
14857 typed_string_declaration ::=
14858 @b{type} <typed_string_>_simple_name @b{is}
14859 ( string_literal @{, string_literal@} );
14861 other_declarative_item ::=
14862 attribute_declaration |
14863 typed_variable_declaration |
14864 variable_declaration |
14867 attribute_declaration ::=
14868 full_associative_array_declaration |
14869 @b{for} attribute_designator @b{use} expression ;
14871 full_associative_array_declaration ::=
14872 @b{for} <associative_array_attribute_>simple_name @b{use}
14873 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
14875 attribute_designator ::=
14876 <simple_attribute_>simple_name |
14877 <associative_array_attribute_>simple_name ( string_literal )
14879 typed_variable_declaration ::=
14880 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
14882 variable_declaration ::=
14883 <variable_>simple_name := expression;
14893 attribute_reference
14899 ( <string_>expression @{ , <string_>expression @} )
14902 @b{external} ( string_literal [, string_literal] )
14904 attribute_reference ::=
14905 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
14907 attribute_prefix ::=
14909 <project_>simple_name | package_identifier |
14910 <project_>simple_name . package_identifier
14912 case_construction ::=
14913 @b{case} <typed_variable_>name @b{is}
14918 @b{when} discrete_choice_list =>
14919 @{case_construction | attribute_declaration@}
14921 discrete_choice_list ::=
14922 string_literal @{| string_literal@} |
14926 simple_name @{. simple_name@}
14929 identifier (same as Ada)
14933 @node The Cross-Referencing Tools gnatxref and gnatfind
14934 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
14939 The compiler generates cross-referencing information (unless
14940 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
14941 This information indicates where in the source each entity is declared and
14942 referenced. Note that entities in package Standard are not included, but
14943 entities in all other predefined units are included in the output.
14945 Before using any of these two tools, you need to compile successfully your
14946 application, so that GNAT gets a chance to generate the cross-referencing
14949 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
14950 information to provide the user with the capability to easily locate the
14951 declaration and references to an entity. These tools are quite similar,
14952 the difference being that @code{gnatfind} is intended for locating
14953 definitions and/or references to a specified entity or entities, whereas
14954 @code{gnatxref} is oriented to generating a full report of all
14957 To use these tools, you must not compile your application using the
14958 @option{-gnatx} switch on the @command{gnatmake} command line
14959 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
14960 information will not be generated.
14962 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
14963 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
14966 * gnatxref Switches::
14967 * gnatfind Switches::
14968 * Project Files for gnatxref and gnatfind::
14969 * Regular Expressions in gnatfind and gnatxref::
14970 * Examples of gnatxref Usage::
14971 * Examples of gnatfind Usage::
14974 @node gnatxref Switches
14975 @section @code{gnatxref} Switches
14978 The command invocation for @code{gnatxref} is:
14980 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
14989 identifies the source files for which a report is to be generated. The
14990 ``with''ed units will be processed too. You must provide at least one file.
14992 These file names are considered to be regular expressions, so for instance
14993 specifying @file{source*.adb} is the same as giving every file in the current
14994 directory whose name starts with @file{source} and whose extension is
14997 You shouldn't specify any directory name, just base names. @command{gnatxref}
14998 and @command{gnatfind} will be able to locate these files by themselves using
14999 the source path. If you specify directories, no result is produced.
15004 The switches can be:
15008 @cindex @option{--version} @command{gnatxref}
15009 Display Copyright and version, then exit disregarding all other options.
15012 @cindex @option{--help} @command{gnatxref}
15013 If @option{--version} was not used, display usage, then exit disregarding
15016 @item ^-a^/ALL_FILES^
15017 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15018 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15019 the read-only files found in the library search path. Otherwise, these files
15020 will be ignored. This option can be used to protect Gnat sources or your own
15021 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15022 much faster, and their output much smaller. Read-only here refers to access
15023 or permissions status in the file system for the current user.
15026 @cindex @option{-aIDIR} (@command{gnatxref})
15027 When looking for source files also look in directory DIR. The order in which
15028 source file search is undertaken is the same as for @command{gnatmake}.
15031 @cindex @option{-aODIR} (@command{gnatxref})
15032 When searching for library and object files, look in directory
15033 DIR. The order in which library files are searched is the same as for
15034 @command{gnatmake}.
15037 @cindex @option{-nostdinc} (@command{gnatxref})
15038 Do not look for sources in the system default directory.
15041 @cindex @option{-nostdlib} (@command{gnatxref})
15042 Do not look for library files in the system default directory.
15044 @item --RTS=@var{rts-path}
15045 @cindex @option{--RTS} (@command{gnatxref})
15046 Specifies the default location of the runtime library. Same meaning as the
15047 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15049 @item ^-d^/DERIVED_TYPES^
15050 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15051 If this switch is set @code{gnatxref} will output the parent type
15052 reference for each matching derived types.
15054 @item ^-f^/FULL_PATHNAME^
15055 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15056 If this switch is set, the output file names will be preceded by their
15057 directory (if the file was found in the search path). If this switch is
15058 not set, the directory will not be printed.
15060 @item ^-g^/IGNORE_LOCALS^
15061 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15062 If this switch is set, information is output only for library-level
15063 entities, ignoring local entities. The use of this switch may accelerate
15064 @code{gnatfind} and @code{gnatxref}.
15067 @cindex @option{-IDIR} (@command{gnatxref})
15068 Equivalent to @samp{-aODIR -aIDIR}.
15071 @cindex @option{-pFILE} (@command{gnatxref})
15072 Specify a project file to use @xref{Project Files}.
15073 If you need to use the @file{.gpr}
15074 project files, you should use gnatxref through the GNAT driver
15075 (@command{gnat xref -Pproject}).
15077 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15078 project file in the current directory.
15080 If a project file is either specified or found by the tools, then the content
15081 of the source directory and object directory lines are added as if they
15082 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15083 and @samp{^-aO^OBJECT_SEARCH^}.
15085 Output only unused symbols. This may be really useful if you give your
15086 main compilation unit on the command line, as @code{gnatxref} will then
15087 display every unused entity and 'with'ed package.
15091 Instead of producing the default output, @code{gnatxref} will generate a
15092 @file{tags} file that can be used by vi. For examples how to use this
15093 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15094 to the standard output, thus you will have to redirect it to a file.
15100 All these switches may be in any order on the command line, and may even
15101 appear after the file names. They need not be separated by spaces, thus
15102 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15103 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15105 @node gnatfind Switches
15106 @section @code{gnatfind} Switches
15109 The command line for @code{gnatfind} is:
15112 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15113 @r{[}@var{file1} @var{file2} @dots{}]
15121 An entity will be output only if it matches the regular expression found
15122 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15124 Omitting the pattern is equivalent to specifying @samp{*}, which
15125 will match any entity. Note that if you do not provide a pattern, you
15126 have to provide both a sourcefile and a line.
15128 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15129 for matching purposes. At the current time there is no support for
15130 8-bit codes other than Latin-1, or for wide characters in identifiers.
15133 @code{gnatfind} will look for references, bodies or declarations
15134 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15135 and column @var{column}. See @ref{Examples of gnatfind Usage}
15136 for syntax examples.
15139 is a decimal integer identifying the line number containing
15140 the reference to the entity (or entities) to be located.
15143 is a decimal integer identifying the exact location on the
15144 line of the first character of the identifier for the
15145 entity reference. Columns are numbered from 1.
15147 @item file1 file2 @dots{}
15148 The search will be restricted to these source files. If none are given, then
15149 the search will be done for every library file in the search path.
15150 These file must appear only after the pattern or sourcefile.
15152 These file names are considered to be regular expressions, so for instance
15153 specifying @file{source*.adb} is the same as giving every file in the current
15154 directory whose name starts with @file{source} and whose extension is
15157 The location of the spec of the entity will always be displayed, even if it
15158 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15159 occurrences of the entity in the separate units of the ones given on the
15160 command line will also be displayed.
15162 Note that if you specify at least one file in this part, @code{gnatfind} may
15163 sometimes not be able to find the body of the subprograms.
15168 At least one of 'sourcefile' or 'pattern' has to be present on
15171 The following switches are available:
15175 @cindex @option{--version} @command{gnatfind}
15176 Display Copyright and version, then exit disregarding all other options.
15179 @cindex @option{--help} @command{gnatfind}
15180 If @option{--version} was not used, display usage, then exit disregarding
15183 @item ^-a^/ALL_FILES^
15184 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15185 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15186 the read-only files found in the library search path. Otherwise, these files
15187 will be ignored. This option can be used to protect Gnat sources or your own
15188 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15189 much faster, and their output much smaller. Read-only here refers to access
15190 or permission status in the file system for the current user.
15193 @cindex @option{-aIDIR} (@command{gnatfind})
15194 When looking for source files also look in directory DIR. The order in which
15195 source file search is undertaken is the same as for @command{gnatmake}.
15198 @cindex @option{-aODIR} (@command{gnatfind})
15199 When searching for library and object files, look in directory
15200 DIR. The order in which library files are searched is the same as for
15201 @command{gnatmake}.
15204 @cindex @option{-nostdinc} (@command{gnatfind})
15205 Do not look for sources in the system default directory.
15208 @cindex @option{-nostdlib} (@command{gnatfind})
15209 Do not look for library files in the system default directory.
15211 @item --RTS=@var{rts-path}
15212 @cindex @option{--RTS} (@command{gnatfind})
15213 Specifies the default location of the runtime library. Same meaning as the
15214 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15216 @item ^-d^/DERIVED_TYPE_INFORMATION^
15217 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15218 If this switch is set, then @code{gnatfind} will output the parent type
15219 reference for each matching derived types.
15221 @item ^-e^/EXPRESSIONS^
15222 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15223 By default, @code{gnatfind} accept the simple regular expression set for
15224 @samp{pattern}. If this switch is set, then the pattern will be
15225 considered as full Unix-style regular expression.
15227 @item ^-f^/FULL_PATHNAME^
15228 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15229 If this switch is set, the output file names will be preceded by their
15230 directory (if the file was found in the search path). If this switch is
15231 not set, the directory will not be printed.
15233 @item ^-g^/IGNORE_LOCALS^
15234 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15235 If this switch is set, information is output only for library-level
15236 entities, ignoring local entities. The use of this switch may accelerate
15237 @code{gnatfind} and @code{gnatxref}.
15240 @cindex @option{-IDIR} (@command{gnatfind})
15241 Equivalent to @samp{-aODIR -aIDIR}.
15244 @cindex @option{-pFILE} (@command{gnatfind})
15245 Specify a project file (@pxref{Project Files}) to use.
15246 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15247 project file in the current directory.
15249 If a project file is either specified or found by the tools, then the content
15250 of the source directory and object directory lines are added as if they
15251 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15252 @samp{^-aO^/OBJECT_SEARCH^}.
15254 @item ^-r^/REFERENCES^
15255 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15256 By default, @code{gnatfind} will output only the information about the
15257 declaration, body or type completion of the entities. If this switch is
15258 set, the @code{gnatfind} will locate every reference to the entities in
15259 the files specified on the command line (or in every file in the search
15260 path if no file is given on the command line).
15262 @item ^-s^/PRINT_LINES^
15263 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15264 If this switch is set, then @code{gnatfind} will output the content
15265 of the Ada source file lines were the entity was found.
15267 @item ^-t^/TYPE_HIERARCHY^
15268 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15269 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15270 the specified type. It act like -d option but recursively from parent
15271 type to parent type. When this switch is set it is not possible to
15272 specify more than one file.
15277 All these switches may be in any order on the command line, and may even
15278 appear after the file names. They need not be separated by spaces, thus
15279 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15280 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15282 As stated previously, gnatfind will search in every directory in the
15283 search path. You can force it to look only in the current directory if
15284 you specify @code{*} at the end of the command line.
15286 @node Project Files for gnatxref and gnatfind
15287 @section Project Files for @command{gnatxref} and @command{gnatfind}
15290 Project files allow a programmer to specify how to compile its
15291 application, where to find sources, etc. These files are used
15293 primarily by GPS, but they can also be used
15296 @code{gnatxref} and @code{gnatfind}.
15298 A project file name must end with @file{.gpr}. If a single one is
15299 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15300 extract the information from it. If multiple project files are found, none of
15301 them is read, and you have to use the @samp{-p} switch to specify the one
15304 The following lines can be included, even though most of them have default
15305 values which can be used in most cases.
15306 The lines can be entered in any order in the file.
15307 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15308 each line. If you have multiple instances, only the last one is taken into
15313 [default: @code{"^./^[]^"}]
15314 specifies a directory where to look for source files. Multiple @code{src_dir}
15315 lines can be specified and they will be searched in the order they
15319 [default: @code{"^./^[]^"}]
15320 specifies a directory where to look for object and library files. Multiple
15321 @code{obj_dir} lines can be specified, and they will be searched in the order
15324 @item comp_opt=SWITCHES
15325 [default: @code{""}]
15326 creates a variable which can be referred to subsequently by using
15327 the @code{$@{comp_opt@}} notation. This is intended to store the default
15328 switches given to @command{gnatmake} and @command{gcc}.
15330 @item bind_opt=SWITCHES
15331 [default: @code{""}]
15332 creates a variable which can be referred to subsequently by using
15333 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15334 switches given to @command{gnatbind}.
15336 @item link_opt=SWITCHES
15337 [default: @code{""}]
15338 creates a variable which can be referred to subsequently by using
15339 the @samp{$@{link_opt@}} notation. This is intended to store the default
15340 switches given to @command{gnatlink}.
15342 @item main=EXECUTABLE
15343 [default: @code{""}]
15344 specifies the name of the executable for the application. This variable can
15345 be referred to in the following lines by using the @samp{$@{main@}} notation.
15348 @item comp_cmd=COMMAND
15349 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15352 @item comp_cmd=COMMAND
15353 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15355 specifies the command used to compile a single file in the application.
15358 @item make_cmd=COMMAND
15359 [default: @code{"GNAT MAKE $@{main@}
15360 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15361 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15362 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15365 @item make_cmd=COMMAND
15366 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15367 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15368 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15370 specifies the command used to recompile the whole application.
15372 @item run_cmd=COMMAND
15373 [default: @code{"$@{main@}"}]
15374 specifies the command used to run the application.
15376 @item debug_cmd=COMMAND
15377 [default: @code{"gdb $@{main@}"}]
15378 specifies the command used to debug the application
15383 @command{gnatxref} and @command{gnatfind} only take into account the
15384 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15386 @node Regular Expressions in gnatfind and gnatxref
15387 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15390 As specified in the section about @command{gnatfind}, the pattern can be a
15391 regular expression. Actually, there are to set of regular expressions
15392 which are recognized by the program:
15395 @item globbing patterns
15396 These are the most usual regular expression. They are the same that you
15397 generally used in a Unix shell command line, or in a DOS session.
15399 Here is a more formal grammar:
15406 term ::= elmt -- matches elmt
15407 term ::= elmt elmt -- concatenation (elmt then elmt)
15408 term ::= * -- any string of 0 or more characters
15409 term ::= ? -- matches any character
15410 term ::= [char @{char@}] -- matches any character listed
15411 term ::= [char - char] -- matches any character in range
15415 @item full regular expression
15416 The second set of regular expressions is much more powerful. This is the
15417 type of regular expressions recognized by utilities such a @file{grep}.
15419 The following is the form of a regular expression, expressed in Ada
15420 reference manual style BNF is as follows
15427 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15429 term ::= item @{item@} -- concatenation (item then item)
15431 item ::= elmt -- match elmt
15432 item ::= elmt * -- zero or more elmt's
15433 item ::= elmt + -- one or more elmt's
15434 item ::= elmt ? -- matches elmt or nothing
15437 elmt ::= nschar -- matches given character
15438 elmt ::= [nschar @{nschar@}] -- matches any character listed
15439 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15440 elmt ::= [char - char] -- matches chars in given range
15441 elmt ::= \ char -- matches given character
15442 elmt ::= . -- matches any single character
15443 elmt ::= ( regexp ) -- parens used for grouping
15445 char ::= any character, including special characters
15446 nschar ::= any character except ()[].*+?^^^
15450 Following are a few examples:
15454 will match any of the two strings @samp{abcde} and @samp{fghi},
15457 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15458 @samp{abcccd}, and so on,
15461 will match any string which has only lowercase characters in it (and at
15462 least one character.
15467 @node Examples of gnatxref Usage
15468 @section Examples of @code{gnatxref} Usage
15470 @subsection General Usage
15473 For the following examples, we will consider the following units:
15475 @smallexample @c ada
15481 3: procedure Foo (B : in Integer);
15488 1: package body Main is
15489 2: procedure Foo (B : in Integer) is
15500 2: procedure Print (B : Integer);
15509 The first thing to do is to recompile your application (for instance, in
15510 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15511 the cross-referencing information.
15512 You can then issue any of the following commands:
15514 @item gnatxref main.adb
15515 @code{gnatxref} generates cross-reference information for main.adb
15516 and every unit 'with'ed by main.adb.
15518 The output would be:
15526 Decl: main.ads 3:20
15527 Body: main.adb 2:20
15528 Ref: main.adb 4:13 5:13 6:19
15531 Ref: main.adb 6:8 7:8
15541 Decl: main.ads 3:15
15542 Body: main.adb 2:15
15545 Body: main.adb 1:14
15548 Ref: main.adb 6:12 7:12
15552 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15553 its body is in main.adb, line 1, column 14 and is not referenced any where.
15555 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15556 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15558 @item gnatxref package1.adb package2.ads
15559 @code{gnatxref} will generates cross-reference information for
15560 package1.adb, package2.ads and any other package 'with'ed by any
15566 @subsection Using gnatxref with vi
15568 @code{gnatxref} can generate a tags file output, which can be used
15569 directly from @command{vi}. Note that the standard version of @command{vi}
15570 will not work properly with overloaded symbols. Consider using another
15571 free implementation of @command{vi}, such as @command{vim}.
15574 $ gnatxref -v gnatfind.adb > tags
15578 will generate the tags file for @code{gnatfind} itself (if the sources
15579 are in the search path!).
15581 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15582 (replacing @var{entity} by whatever you are looking for), and vi will
15583 display a new file with the corresponding declaration of entity.
15586 @node Examples of gnatfind Usage
15587 @section Examples of @code{gnatfind} Usage
15591 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15592 Find declarations for all entities xyz referenced at least once in
15593 main.adb. The references are search in every library file in the search
15596 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15599 The output will look like:
15601 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15602 ^directory/^[directory]^main.adb:24:10: xyz <= body
15603 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15607 that is to say, one of the entities xyz found in main.adb is declared at
15608 line 12 of main.ads (and its body is in main.adb), and another one is
15609 declared at line 45 of foo.ads
15611 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15612 This is the same command as the previous one, instead @code{gnatfind} will
15613 display the content of the Ada source file lines.
15615 The output will look like:
15618 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15620 ^directory/^[directory]^main.adb:24:10: xyz <= body
15622 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15627 This can make it easier to find exactly the location your are looking
15630 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15631 Find references to all entities containing an x that are
15632 referenced on line 123 of main.ads.
15633 The references will be searched only in main.ads and foo.adb.
15635 @item gnatfind main.ads:123
15636 Find declarations and bodies for all entities that are referenced on
15637 line 123 of main.ads.
15639 This is the same as @code{gnatfind "*":main.adb:123}.
15641 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15642 Find the declaration for the entity referenced at column 45 in
15643 line 123 of file main.adb in directory mydir. Note that it
15644 is usual to omit the identifier name when the column is given,
15645 since the column position identifies a unique reference.
15647 The column has to be the beginning of the identifier, and should not
15648 point to any character in the middle of the identifier.
15652 @c *********************************
15653 @node The GNAT Pretty-Printer gnatpp
15654 @chapter The GNAT Pretty-Printer @command{gnatpp}
15656 @cindex Pretty-Printer
15659 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15660 for source reformatting / pretty-printing.
15661 It takes an Ada source file as input and generates a reformatted
15663 You can specify various style directives via switches; e.g.,
15664 identifier case conventions, rules of indentation, and comment layout.
15666 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
15667 tree for the input source and thus requires the input to be syntactically and
15668 semantically legal.
15669 If this condition is not met, @command{gnatpp} will terminate with an
15670 error message; no output file will be generated.
15672 If the source files presented to @command{gnatpp} contain
15673 preprocessing directives, then the output file will
15674 correspond to the generated source after all
15675 preprocessing is carried out. There is no way
15676 using @command{gnatpp} to obtain pretty printed files that
15677 include the preprocessing directives.
15679 If the compilation unit
15680 contained in the input source depends semantically upon units located
15681 outside the current directory, you have to provide the source search path
15682 when invoking @command{gnatpp}, if these units are contained in files with
15683 names that do not follow the GNAT file naming rules, you have to provide
15684 the configuration file describing the corresponding naming scheme;
15685 see the description of the @command{gnatpp}
15686 switches below. Another possibility is to use a project file and to
15687 call @command{gnatpp} through the @command{gnat} driver
15689 The @command{gnatpp} command has the form
15692 $ gnatpp @ovar{switches} @var{filename}
15699 @var{switches} is an optional sequence of switches defining such properties as
15700 the formatting rules, the source search path, and the destination for the
15704 @var{filename} is the name (including the extension) of the source file to
15705 reformat; ``wildcards'' or several file names on the same gnatpp command are
15706 allowed. The file name may contain path information; it does not have to
15707 follow the GNAT file naming rules
15711 * Switches for gnatpp::
15712 * Formatting Rules::
15715 @node Switches for gnatpp
15716 @section Switches for @command{gnatpp}
15719 The following subsections describe the various switches accepted by
15720 @command{gnatpp}, organized by category.
15723 You specify a switch by supplying a name and generally also a value.
15724 In many cases the values for a switch with a given name are incompatible with
15726 (for example the switch that controls the casing of a reserved word may have
15727 exactly one value: upper case, lower case, or
15728 mixed case) and thus exactly one such switch can be in effect for an
15729 invocation of @command{gnatpp}.
15730 If more than one is supplied, the last one is used.
15731 However, some values for the same switch are mutually compatible.
15732 You may supply several such switches to @command{gnatpp}, but then
15733 each must be specified in full, with both the name and the value.
15734 Abbreviated forms (the name appearing once, followed by each value) are
15736 For example, to set
15737 the alignment of the assignment delimiter both in declarations and in
15738 assignment statements, you must write @option{-A2A3}
15739 (or @option{-A2 -A3}), but not @option{-A23}.
15743 In many cases the set of options for a given qualifier are incompatible with
15744 each other (for example the qualifier that controls the casing of a reserved
15745 word may have exactly one option, which specifies either upper case, lower
15746 case, or mixed case), and thus exactly one such option can be in effect for
15747 an invocation of @command{gnatpp}.
15748 If more than one is supplied, the last one is used.
15749 However, some qualifiers have options that are mutually compatible,
15750 and then you may then supply several such options when invoking
15754 In most cases, it is obvious whether or not the
15755 ^values for a switch with a given name^options for a given qualifier^
15756 are compatible with each other.
15757 When the semantics might not be evident, the summaries below explicitly
15758 indicate the effect.
15761 * Alignment Control::
15763 * Construct Layout Control::
15764 * General Text Layout Control::
15765 * Other Formatting Options::
15766 * Setting the Source Search Path::
15767 * Output File Control::
15768 * Other gnatpp Switches::
15771 @node Alignment Control
15772 @subsection Alignment Control
15773 @cindex Alignment control in @command{gnatpp}
15776 Programs can be easier to read if certain constructs are vertically aligned.
15777 By default all alignments are set ON.
15778 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
15779 OFF, and then use one or more of the other
15780 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
15781 to activate alignment for specific constructs.
15784 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
15788 Set all alignments to ON
15791 @item ^-A0^/ALIGN=OFF^
15792 Set all alignments to OFF
15794 @item ^-A1^/ALIGN=COLONS^
15795 Align @code{:} in declarations
15797 @item ^-A2^/ALIGN=DECLARATIONS^
15798 Align @code{:=} in initializations in declarations
15800 @item ^-A3^/ALIGN=STATEMENTS^
15801 Align @code{:=} in assignment statements
15803 @item ^-A4^/ALIGN=ARROWS^
15804 Align @code{=>} in associations
15806 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
15807 Align @code{at} keywords in the component clauses in record
15808 representation clauses
15812 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
15815 @node Casing Control
15816 @subsection Casing Control
15817 @cindex Casing control in @command{gnatpp}
15820 @command{gnatpp} allows you to specify the casing for reserved words,
15821 pragma names, attribute designators and identifiers.
15822 For identifiers you may define a
15823 general rule for name casing but also override this rule
15824 via a set of dictionary files.
15826 Three types of casing are supported: lower case, upper case, and mixed case.
15827 Lower and upper case are self-explanatory (but since some letters in
15828 Latin1 and other GNAT-supported character sets
15829 exist only in lower-case form, an upper case conversion will have no
15831 ``Mixed case'' means that the first letter, and also each letter immediately
15832 following an underscore, are converted to their uppercase forms;
15833 all the other letters are converted to their lowercase forms.
15836 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
15837 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
15838 Attribute designators are lower case
15840 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
15841 Attribute designators are upper case
15843 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
15844 Attribute designators are mixed case (this is the default)
15846 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
15847 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
15848 Keywords (technically, these are known in Ada as @emph{reserved words}) are
15849 lower case (this is the default)
15851 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
15852 Keywords are upper case
15854 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
15855 @item ^-nD^/NAME_CASING=AS_DECLARED^
15856 Name casing for defining occurrences are as they appear in the source file
15857 (this is the default)
15859 @item ^-nU^/NAME_CASING=UPPER_CASE^
15860 Names are in upper case
15862 @item ^-nL^/NAME_CASING=LOWER_CASE^
15863 Names are in lower case
15865 @item ^-nM^/NAME_CASING=MIXED_CASE^
15866 Names are in mixed case
15868 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
15869 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
15870 Pragma names are lower case
15872 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
15873 Pragma names are upper case
15875 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
15876 Pragma names are mixed case (this is the default)
15878 @item ^-D@var{file}^/DICTIONARY=@var{file}^
15879 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
15880 Use @var{file} as a @emph{dictionary file} that defines
15881 the casing for a set of specified names,
15882 thereby overriding the effect on these names by
15883 any explicit or implicit
15884 ^-n^/NAME_CASING^ switch.
15885 To supply more than one dictionary file,
15886 use ^several @option{-D} switches^a list of files as options^.
15889 @option{gnatpp} implicitly uses a @emph{default dictionary file}
15890 to define the casing for the Ada predefined names and
15891 the names declared in the GNAT libraries.
15893 @item ^-D-^/SPECIFIC_CASING^
15894 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
15895 Do not use the default dictionary file;
15896 instead, use the casing
15897 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
15902 The structure of a dictionary file, and details on the conventions
15903 used in the default dictionary file, are defined in @ref{Name Casing}.
15905 The @option{^-D-^/SPECIFIC_CASING^} and
15906 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
15909 @node Construct Layout Control
15910 @subsection Construct Layout Control
15911 @cindex Layout control in @command{gnatpp}
15914 This group of @command{gnatpp} switches controls the layout of comments and
15915 complex syntactic constructs. See @ref{Formatting Comments} for details
15919 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
15920 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
15921 All the comments remain unchanged
15923 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
15924 GNAT-style comment line indentation (this is the default).
15926 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
15927 Reference-manual comment line indentation.
15929 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
15930 GNAT-style comment beginning
15932 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
15933 Reformat comment blocks
15935 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
15936 Keep unchanged special form comments
15938 Reformat comment blocks
15940 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
15941 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
15942 GNAT-style layout (this is the default)
15944 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
15947 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
15950 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
15952 All the VT characters are removed from the comment text. All the HT characters
15953 are expanded with the sequences of space characters to get to the next tab
15956 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
15957 @item ^--no-separate-is^/NO_SEPARATE_IS^
15958 Do not place the keyword @code{is} on a separate line in a subprogram body in
15959 case if the spec occupies more then one line.
15961 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
15962 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
15963 Place the keyword @code{loop} in FOR and WHILE loop statements and the
15964 keyword @code{then} in IF statements on a separate line.
15966 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
15967 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
15968 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
15969 keyword @code{then} in IF statements on a separate line. This option is
15970 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
15972 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
15973 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
15974 Start each USE clause in a context clause from a separate line.
15976 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
15977 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
15978 Use a separate line for a loop or block statement name, but do not use an extra
15979 indentation level for the statement itself.
15985 The @option{-c1} and @option{-c2} switches are incompatible.
15986 The @option{-c3} and @option{-c4} switches are compatible with each other and
15987 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
15988 the other comment formatting switches.
15990 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
15995 For the @option{/COMMENTS_LAYOUT} qualifier:
15998 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16000 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16001 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16005 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16006 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16009 @node General Text Layout Control
16010 @subsection General Text Layout Control
16013 These switches allow control over line length and indentation.
16016 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16017 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16018 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16020 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16021 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16022 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16024 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16025 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16026 Indentation level for continuation lines (relative to the line being
16027 continued), @var{nnn} from 1@dots{}9.
16029 value is one less then the (normal) indentation level, unless the
16030 indentation is set to 1 (in which case the default value for continuation
16031 line indentation is also 1)
16034 @node Other Formatting Options
16035 @subsection Other Formatting Options
16038 These switches control the inclusion of missing end/exit labels, and
16039 the indentation level in @b{case} statements.
16042 @item ^-e^/NO_MISSED_LABELS^
16043 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16044 Do not insert missing end/exit labels. An end label is the name of
16045 a construct that may optionally be repeated at the end of the
16046 construct's declaration;
16047 e.g., the names of packages, subprograms, and tasks.
16048 An exit label is the name of a loop that may appear as target
16049 of an exit statement within the loop.
16050 By default, @command{gnatpp} inserts these end/exit labels when
16051 they are absent from the original source. This option suppresses such
16052 insertion, so that the formatted source reflects the original.
16054 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16055 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16056 Insert a Form Feed character after a pragma Page.
16058 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16059 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16060 Do not use an additional indentation level for @b{case} alternatives
16061 and variants if there are @var{nnn} or more (the default
16063 If @var{nnn} is 0, an additional indentation level is
16064 used for @b{case} alternatives and variants regardless of their number.
16067 @node Setting the Source Search Path
16068 @subsection Setting the Source Search Path
16071 To define the search path for the input source file, @command{gnatpp}
16072 uses the same switches as the GNAT compiler, with the same effects.
16075 @item ^-I^/SEARCH=^@var{dir}
16076 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16077 The same as the corresponding gcc switch
16079 @item ^-I-^/NOCURRENT_DIRECTORY^
16080 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16081 The same as the corresponding gcc switch
16083 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16084 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16085 The same as the corresponding gcc switch
16087 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16088 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16089 The same as the corresponding gcc switch
16093 @node Output File Control
16094 @subsection Output File Control
16097 By default the output is sent to the file whose name is obtained by appending
16098 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16099 (if the file with this name already exists, it is unconditionally overwritten).
16100 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16101 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16103 The output may be redirected by the following switches:
16106 @item ^-pipe^/STANDARD_OUTPUT^
16107 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16108 Send the output to @code{Standard_Output}
16110 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16111 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16112 Write the output into @var{output_file}.
16113 If @var{output_file} already exists, @command{gnatpp} terminates without
16114 reading or processing the input file.
16116 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16117 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16118 Write the output into @var{output_file}, overwriting the existing file
16119 (if one is present).
16121 @item ^-r^/REPLACE^
16122 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16123 Replace the input source file with the reformatted output, and copy the
16124 original input source into the file whose name is obtained by appending the
16125 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16126 If a file with this name already exists, @command{gnatpp} terminates without
16127 reading or processing the input file.
16129 @item ^-rf^/OVERRIDING_REPLACE^
16130 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16131 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16132 already exists, it is overwritten.
16134 @item ^-rnb^/REPLACE_NO_BACKUP^
16135 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16136 Replace the input source file with the reformatted output without
16137 creating any backup copy of the input source.
16139 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16140 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16141 Specifies the format of the reformatted output file. The @var{xxx}
16142 ^string specified with the switch^option^ may be either
16144 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16145 @item ``@option{^crlf^CRLF^}''
16146 the same as @option{^crlf^CRLF^}
16147 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16148 @item ``@option{^lf^LF^}''
16149 the same as @option{^unix^UNIX^}
16152 @item ^-W^/RESULT_ENCODING=^@var{e}
16153 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16154 Specify the wide character encoding method used to write the code in the
16156 @var{e} is one of the following:
16164 Upper half encoding
16166 @item ^s^SHIFT_JIS^
16176 Brackets encoding (default value)
16182 Options @option{^-pipe^/STANDARD_OUTPUT^},
16183 @option{^-o^/OUTPUT^} and
16184 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16185 contains only one file to reformat.
16187 @option{^--eol^/END_OF_LINE^}
16189 @option{^-W^/RESULT_ENCODING^}
16190 cannot be used together
16191 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16193 @node Other gnatpp Switches
16194 @subsection Other @code{gnatpp} Switches
16197 The additional @command{gnatpp} switches are defined in this subsection.
16200 @item ^-files @var{filename}^/FILES=@var{output_file}^
16201 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16202 Take the argument source files from the specified file. This file should be an
16203 ordinary textual file containing file names separated by spaces or
16204 line breaks. You can use this switch more then once in the same call to
16205 @command{gnatpp}. You also can combine this switch with explicit list of
16208 @item ^-v^/VERBOSE^
16209 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16211 @command{gnatpp} generates version information and then
16212 a trace of the actions it takes to produce or obtain the ASIS tree.
16214 @item ^-w^/WARNINGS^
16215 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16217 @command{gnatpp} generates a warning whenever it cannot provide
16218 a required layout in the result source.
16221 @node Formatting Rules
16222 @section Formatting Rules
16225 The following subsections show how @command{gnatpp} treats ``white space'',
16226 comments, program layout, and name casing.
16227 They provide the detailed descriptions of the switches shown above.
16230 * White Space and Empty Lines::
16231 * Formatting Comments::
16232 * Construct Layout::
16236 @node White Space and Empty Lines
16237 @subsection White Space and Empty Lines
16240 @command{gnatpp} does not have an option to control space characters.
16241 It will add or remove spaces according to the style illustrated by the
16242 examples in the @cite{Ada Reference Manual}.
16244 The only format effectors
16245 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16246 that will appear in the output file are platform-specific line breaks,
16247 and also format effectors within (but not at the end of) comments.
16248 In particular, each horizontal tab character that is not inside
16249 a comment will be treated as a space and thus will appear in the
16250 output file as zero or more spaces depending on
16251 the reformatting of the line in which it appears.
16252 The only exception is a Form Feed character, which is inserted after a
16253 pragma @code{Page} when @option{-ff} is set.
16255 The output file will contain no lines with trailing ``white space'' (spaces,
16258 Empty lines in the original source are preserved
16259 only if they separate declarations or statements.
16260 In such contexts, a
16261 sequence of two or more empty lines is replaced by exactly one empty line.
16262 Note that a blank line will be removed if it separates two ``comment blocks''
16263 (a comment block is a sequence of whole-line comments).
16264 In order to preserve a visual separation between comment blocks, use an
16265 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16266 Likewise, if for some reason you wish to have a sequence of empty lines,
16267 use a sequence of empty comments instead.
16269 @node Formatting Comments
16270 @subsection Formatting Comments
16273 Comments in Ada code are of two kinds:
16276 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16277 ``white space'') on a line
16280 an @emph{end-of-line comment}, which follows some other Ada lexical element
16285 The indentation of a whole-line comment is that of either
16286 the preceding or following line in
16287 the formatted source, depending on switch settings as will be described below.
16289 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16290 between the end of the preceding Ada lexical element and the beginning
16291 of the comment as appear in the original source,
16292 unless either the comment has to be split to
16293 satisfy the line length limitation, or else the next line contains a
16294 whole line comment that is considered a continuation of this end-of-line
16295 comment (because it starts at the same position).
16297 cases, the start of the end-of-line comment is moved right to the nearest
16298 multiple of the indentation level.
16299 This may result in a ``line overflow'' (the right-shifted comment extending
16300 beyond the maximum line length), in which case the comment is split as
16303 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16304 (GNAT-style comment line indentation)
16305 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16306 (reference-manual comment line indentation).
16307 With reference-manual style, a whole-line comment is indented as if it
16308 were a declaration or statement at the same place
16309 (i.e., according to the indentation of the preceding line(s)).
16310 With GNAT style, a whole-line comment that is immediately followed by an
16311 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16312 word @b{begin}, is indented based on the construct that follows it.
16315 @smallexample @c ada
16327 Reference-manual indentation produces:
16329 @smallexample @c ada
16341 while GNAT-style indentation produces:
16343 @smallexample @c ada
16355 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16356 (GNAT style comment beginning) has the following
16361 For each whole-line comment that does not end with two hyphens,
16362 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16363 to ensure that there are at least two spaces between these hyphens and the
16364 first non-blank character of the comment.
16368 For an end-of-line comment, if in the original source the next line is a
16369 whole-line comment that starts at the same position
16370 as the end-of-line comment,
16371 then the whole-line comment (and all whole-line comments
16372 that follow it and that start at the same position)
16373 will start at this position in the output file.
16376 That is, if in the original source we have:
16378 @smallexample @c ada
16381 A := B + C; -- B must be in the range Low1..High1
16382 -- C must be in the range Low2..High2
16383 --B+C will be in the range Low1+Low2..High1+High2
16389 Then in the formatted source we get
16391 @smallexample @c ada
16394 A := B + C; -- B must be in the range Low1..High1
16395 -- C must be in the range Low2..High2
16396 -- B+C will be in the range Low1+Low2..High1+High2
16402 A comment that exceeds the line length limit will be split.
16404 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16405 the line belongs to a reformattable block, splitting the line generates a
16406 @command{gnatpp} warning.
16407 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16408 comments may be reformatted in typical
16409 word processor style (that is, moving words between lines and putting as
16410 many words in a line as possible).
16413 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16414 that has a special format (that is, a character that is neither a letter nor digit
16415 not white space nor line break immediately following the leading @code{--} of
16416 the comment) should be without any change moved from the argument source
16417 into reformatted source. This switch allows to preserve comments that are used
16418 as a special marks in the code (e.g.@: SPARK annotation).
16420 @node Construct Layout
16421 @subsection Construct Layout
16424 In several cases the suggested layout in the Ada Reference Manual includes
16425 an extra level of indentation that many programmers prefer to avoid. The
16426 affected cases include:
16430 @item Record type declaration (RM 3.8)
16432 @item Record representation clause (RM 13.5.1)
16434 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16436 @item Block statement in case if a block has a statement identifier (RM 5.6)
16440 In compact mode (when GNAT style layout or compact layout is set),
16441 the pretty printer uses one level of indentation instead
16442 of two. This is achieved in the record definition and record representation
16443 clause cases by putting the @code{record} keyword on the same line as the
16444 start of the declaration or representation clause, and in the block and loop
16445 case by putting the block or loop header on the same line as the statement
16449 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16450 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16451 layout on the one hand, and uncompact layout
16452 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16453 can be illustrated by the following examples:
16457 @multitable @columnfractions .5 .5
16458 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16461 @smallexample @c ada
16468 @smallexample @c ada
16477 @smallexample @c ada
16479 a at 0 range 0 .. 31;
16480 b at 4 range 0 .. 31;
16484 @smallexample @c ada
16487 a at 0 range 0 .. 31;
16488 b at 4 range 0 .. 31;
16493 @smallexample @c ada
16501 @smallexample @c ada
16511 @smallexample @c ada
16512 Clear : for J in 1 .. 10 loop
16517 @smallexample @c ada
16519 for J in 1 .. 10 loop
16530 GNAT style, compact layout Uncompact layout
16532 type q is record type q is
16533 a : integer; record
16534 b : integer; a : integer;
16535 end record; b : integer;
16538 for q use record for q use
16539 a at 0 range 0 .. 31; record
16540 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16541 end record; b at 4 range 0 .. 31;
16544 Block : declare Block :
16545 A : Integer := 3; declare
16546 begin A : Integer := 3;
16548 end Block; Proc (A, A);
16551 Clear : for J in 1 .. 10 loop Clear :
16552 A (J) := 0; for J in 1 .. 10 loop
16553 end loop Clear; A (J) := 0;
16560 A further difference between GNAT style layout and compact layout is that
16561 GNAT style layout inserts empty lines as separation for
16562 compound statements, return statements and bodies.
16564 Note that the layout specified by
16565 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16566 for named block and loop statements overrides the layout defined by these
16567 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16568 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16569 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16572 @subsection Name Casing
16575 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16576 the same casing as the corresponding defining identifier.
16578 You control the casing for defining occurrences via the
16579 @option{^-n^/NAME_CASING^} switch.
16581 With @option{-nD} (``as declared'', which is the default),
16584 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16586 defining occurrences appear exactly as in the source file
16587 where they are declared.
16588 The other ^values for this switch^options for this qualifier^ ---
16589 @option{^-nU^UPPER_CASE^},
16590 @option{^-nL^LOWER_CASE^},
16591 @option{^-nM^MIXED_CASE^} ---
16593 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16594 If @command{gnatpp} changes the casing of a defining
16595 occurrence, it analogously changes the casing of all the
16596 usage occurrences of this name.
16598 If the defining occurrence of a name is not in the source compilation unit
16599 currently being processed by @command{gnatpp}, the casing of each reference to
16600 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16601 switch (subject to the dictionary file mechanism described below).
16602 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16604 casing for the defining occurrence of the name.
16606 Some names may need to be spelled with casing conventions that are not
16607 covered by the upper-, lower-, and mixed-case transformations.
16608 You can arrange correct casing by placing such names in a
16609 @emph{dictionary file},
16610 and then supplying a @option{^-D^/DICTIONARY^} switch.
16611 The casing of names from dictionary files overrides
16612 any @option{^-n^/NAME_CASING^} switch.
16614 To handle the casing of Ada predefined names and the names from GNAT libraries,
16615 @command{gnatpp} assumes a default dictionary file.
16616 The name of each predefined entity is spelled with the same casing as is used
16617 for the entity in the @cite{Ada Reference Manual}.
16618 The name of each entity in the GNAT libraries is spelled with the same casing
16619 as is used in the declaration of that entity.
16621 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16622 default dictionary file.
16623 Instead, the casing for predefined and GNAT-defined names will be established
16624 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16625 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16626 will appear as just shown,
16627 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16628 To ensure that even such names are rendered in uppercase,
16629 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16630 (or else, less conveniently, place these names in upper case in a dictionary
16633 A dictionary file is
16634 a plain text file; each line in this file can be either a blank line
16635 (containing only space characters and ASCII.HT characters), an Ada comment
16636 line, or the specification of exactly one @emph{casing schema}.
16638 A casing schema is a string that has the following syntax:
16642 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16644 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16649 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16650 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16652 The casing schema string can be followed by white space and/or an Ada-style
16653 comment; any amount of white space is allowed before the string.
16655 If a dictionary file is passed as
16657 the value of a @option{-D@var{file}} switch
16660 an option to the @option{/DICTIONARY} qualifier
16663 simple name and every identifier, @command{gnatpp} checks if the dictionary
16664 defines the casing for the name or for some of its parts (the term ``subword''
16665 is used below to denote the part of a name which is delimited by ``_'' or by
16666 the beginning or end of the word and which does not contain any ``_'' inside):
16670 if the whole name is in the dictionary, @command{gnatpp} uses for this name
16671 the casing defined by the dictionary; no subwords are checked for this word
16674 for every subword @command{gnatpp} checks if the dictionary contains the
16675 corresponding string of the form @code{*@var{simple_identifier}*},
16676 and if it does, the casing of this @var{simple_identifier} is used
16680 if the whole name does not contain any ``_'' inside, and if for this name
16681 the dictionary contains two entries - one of the form @var{identifier},
16682 and another - of the form *@var{simple_identifier}*, then the first one
16683 is applied to define the casing of this name
16686 if more than one dictionary file is passed as @command{gnatpp} switches, each
16687 dictionary adds new casing exceptions and overrides all the existing casing
16688 exceptions set by the previous dictionaries
16691 when @command{gnatpp} checks if the word or subword is in the dictionary,
16692 this check is not case sensitive
16696 For example, suppose we have the following source to reformat:
16698 @smallexample @c ada
16701 name1 : integer := 1;
16702 name4_name3_name2 : integer := 2;
16703 name2_name3_name4 : Boolean;
16706 name2_name3_name4 := name4_name3_name2 > name1;
16712 And suppose we have two dictionaries:
16729 If @command{gnatpp} is called with the following switches:
16733 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
16736 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
16741 then we will get the following name casing in the @command{gnatpp} output:
16743 @smallexample @c ada
16746 NAME1 : Integer := 1;
16747 Name4_NAME3_Name2 : Integer := 2;
16748 Name2_NAME3_Name4 : Boolean;
16751 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
16756 @c *********************************
16757 @node The GNAT Metric Tool gnatmetric
16758 @chapter The GNAT Metric Tool @command{gnatmetric}
16760 @cindex Metric tool
16763 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
16764 for computing various program metrics.
16765 It takes an Ada source file as input and generates a file containing the
16766 metrics data as output. Various switches control which
16767 metrics are computed and output.
16769 @command{gnatmetric} generates and uses the ASIS
16770 tree for the input source and thus requires the input to be syntactically and
16771 semantically legal.
16772 If this condition is not met, @command{gnatmetric} will generate
16773 an error message; no metric information for this file will be
16774 computed and reported.
16776 If the compilation unit contained in the input source depends semantically
16777 upon units in files located outside the current directory, you have to provide
16778 the source search path when invoking @command{gnatmetric}.
16779 If it depends semantically upon units that are contained
16780 in files with names that do not follow the GNAT file naming rules, you have to
16781 provide the configuration file describing the corresponding naming scheme (see
16782 the description of the @command{gnatmetric} switches below.)
16783 Alternatively, you may use a project file and invoke @command{gnatmetric}
16784 through the @command{gnat} driver.
16786 The @command{gnatmetric} command has the form
16789 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
16796 @var{switches} specify the metrics to compute and define the destination for
16800 Each @var{filename} is the name (including the extension) of a source
16801 file to process. ``Wildcards'' are allowed, and
16802 the file name may contain path information.
16803 If no @var{filename} is supplied, then the @var{switches} list must contain
16805 @option{-files} switch (@pxref{Other gnatmetric Switches}).
16806 Including both a @option{-files} switch and one or more
16807 @var{filename} arguments is permitted.
16810 @samp{-cargs @var{gcc_switches}} is a list of switches for
16811 @command{gcc}. They will be passed on to all compiler invocations made by
16812 @command{gnatmetric} to generate the ASIS trees. Here you can provide
16813 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
16814 and use the @option{-gnatec} switch to set the configuration file.
16818 * Switches for gnatmetric::
16821 @node Switches for gnatmetric
16822 @section Switches for @command{gnatmetric}
16825 The following subsections describe the various switches accepted by
16826 @command{gnatmetric}, organized by category.
16829 * Output Files Control::
16830 * Disable Metrics For Local Units::
16831 * Specifying a set of metrics to compute::
16832 * Other gnatmetric Switches::
16833 * Generate project-wide metrics::
16836 @node Output Files Control
16837 @subsection Output File Control
16838 @cindex Output file control in @command{gnatmetric}
16841 @command{gnatmetric} has two output formats. It can generate a
16842 textual (human-readable) form, and also XML. By default only textual
16843 output is generated.
16845 When generating the output in textual form, @command{gnatmetric} creates
16846 for each Ada source file a corresponding text file
16847 containing the computed metrics, except for the case when the set of metrics
16848 specified by gnatmetric parameters consists only of metrics that are computed
16849 for the whole set of analyzed sources, but not for each Ada source.
16850 By default, this file is placed in the same directory as where the source
16851 file is located, and its name is obtained
16852 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
16855 All the output information generated in XML format is placed in a single
16856 file. By default this file is placed in the current directory and has the
16857 name ^@file{metrix.xml}^@file{METRIX$XML}^.
16859 Some of the computed metrics are summed over the units passed to
16860 @command{gnatmetric}; for example, the total number of lines of code.
16861 By default this information is sent to @file{stdout}, but a file
16862 can be specified with the @option{-og} switch.
16864 The following switches control the @command{gnatmetric} output:
16867 @cindex @option{^-x^/XML^} (@command{gnatmetric})
16869 Generate the XML output
16871 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
16872 @item ^-nt^/NO_TEXT^
16873 Do not generate the output in text form (implies @option{^-x^/XML^})
16875 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
16876 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
16877 Put textual files with detailed metrics into @var{output_dir}
16879 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
16880 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
16881 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
16882 in the name of the output file.
16884 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
16885 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
16886 Put global metrics into @var{file_name}
16888 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
16889 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
16890 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
16892 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
16893 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
16894 Use ``short'' source file names in the output. (The @command{gnatmetric}
16895 output includes the name(s) of the Ada source file(s) from which the metrics
16896 are computed. By default each name includes the absolute path. The
16897 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
16898 to exclude all directory information from the file names that are output.)
16902 @node Disable Metrics For Local Units
16903 @subsection Disable Metrics For Local Units
16904 @cindex Disable Metrics For Local Units in @command{gnatmetric}
16907 @command{gnatmetric} relies on the GNAT compilation model @minus{}
16909 unit per one source file. It computes line metrics for the whole source
16910 file, and it also computes syntax
16911 and complexity metrics for the file's outermost unit.
16913 By default, @command{gnatmetric} will also compute all metrics for certain
16914 kinds of locally declared program units:
16918 subprogram (and generic subprogram) bodies;
16921 package (and generic package) specs and bodies;
16924 task object and type specifications and bodies;
16927 protected object and type specifications and bodies.
16931 These kinds of entities will be referred to as
16932 @emph{eligible local program units}, or simply @emph{eligible local units},
16933 @cindex Eligible local unit (for @command{gnatmetric})
16934 in the discussion below.
16936 Note that a subprogram declaration, generic instantiation,
16937 or renaming declaration only receives metrics
16938 computation when it appear as the outermost entity
16941 Suppression of metrics computation for eligible local units can be
16942 obtained via the following switch:
16945 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
16946 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
16947 Do not compute detailed metrics for eligible local program units
16951 @node Specifying a set of metrics to compute
16952 @subsection Specifying a set of metrics to compute
16955 By default all the metrics are computed and reported. The switches
16956 described in this subsection allow you to control, on an individual
16957 basis, whether metrics are computed and
16958 reported. If at least one positive metric
16959 switch is specified (that is, a switch that defines that a given
16960 metric or set of metrics is to be computed), then only
16961 explicitly specified metrics are reported.
16964 * Line Metrics Control::
16965 * Syntax Metrics Control::
16966 * Complexity Metrics Control::
16967 * Object-Oriented Metrics Control::
16970 @node Line Metrics Control
16971 @subsubsection Line Metrics Control
16972 @cindex Line metrics control in @command{gnatmetric}
16975 For any (legal) source file, and for each of its
16976 eligible local program units, @command{gnatmetric} computes the following
16981 the total number of lines;
16984 the total number of code lines (i.e., non-blank lines that are not comments)
16987 the number of comment lines
16990 the number of code lines containing end-of-line comments;
16993 the comment percentage: the ratio between the number of lines that contain
16994 comments and the number of all non-blank lines, expressed as a percentage;
16997 the number of empty lines and lines containing only space characters and/or
16998 format effectors (blank lines)
17001 the average number of code lines in subprogram bodies, task bodies, entry
17002 bodies and statement sequences in package bodies (this metric is only computed
17003 across the whole set of the analyzed units)
17008 @command{gnatmetric} sums the values of the line metrics for all the
17009 files being processed and then generates the cumulative results. The tool
17010 also computes for all the files being processed the average number of code
17013 You can use the following switches to select the specific line metrics
17014 to be computed and reported.
17017 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17020 @cindex @option{--no-lines@var{x}}
17023 @item ^--lines-all^/LINE_COUNT_METRICS=ALL_ON^
17024 Report all the line metrics
17026 @item ^--no-lines-all^/LINE_COUNT_METRICS=ALL_OFF^
17027 Do not report any of line metrics
17029 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES_ON^
17030 Report the number of all lines
17032 @item ^--no-lines^/LINE_COUNT_METRICS=ALL_LINES_OFF^
17033 Do not report the number of all lines
17035 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES_ON^
17036 Report the number of code lines
17038 @item ^--no-lines-code^/LINE_COUNT_METRICS=CODE_LINES_OFF^
17039 Do not report the number of code lines
17041 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_ON^
17042 Report the number of comment lines
17044 @item ^--no-lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES_OFF^
17045 Do not report the number of comment lines
17047 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_ON^
17048 Report the number of code lines containing
17049 end-of-line comments
17051 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES_OFF^
17052 Do not report the number of code lines containing
17053 end-of-line comments
17055 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_ON^
17056 Report the comment percentage in the program text
17058 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE_OFF^
17059 Do not report the comment percentage in the program text
17061 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_ON^
17062 Report the number of blank lines
17064 @item ^--no-lines-blank^/LINE_COUNT_METRICS=BLANK_LINES_OFF^
17065 Do not report the number of blank lines
17067 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_ON^
17068 Report the average number of code lines in subprogram bodies, task bodies,
17069 entry bodies and statement sequences in package bodies. The metric is computed
17070 and reported for the whole set of processed Ada sources only.
17072 @item ^--no-lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES_OFF^
17073 Do not report the average number of code lines in subprogram bodies,
17074 task bodies, entry bodies and statement sequences in package bodies.
17078 @node Syntax Metrics Control
17079 @subsubsection Syntax Metrics Control
17080 @cindex Syntax metrics control in @command{gnatmetric}
17083 @command{gnatmetric} computes various syntactic metrics for the
17084 outermost unit and for each eligible local unit:
17087 @item LSLOC (``Logical Source Lines Of Code'')
17088 The total number of declarations and the total number of statements
17090 @item Maximal static nesting level of inner program units
17092 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17093 package, a task unit, a protected unit, a
17094 protected entry, a generic unit, or an explicitly declared subprogram other
17095 than an enumeration literal.''
17097 @item Maximal nesting level of composite syntactic constructs
17098 This corresponds to the notion of the
17099 maximum nesting level in the GNAT built-in style checks
17100 (@pxref{Style Checking})
17104 For the outermost unit in the file, @command{gnatmetric} additionally computes
17105 the following metrics:
17108 @item Public subprograms
17109 This metric is computed for package specs. It is the
17110 number of subprograms and generic subprograms declared in the visible
17111 part (including the visible part of nested packages, protected objects, and
17114 @item All subprograms
17115 This metric is computed for bodies and subunits. The
17116 metric is equal to a total number of subprogram bodies in the compilation
17118 Neither generic instantiations nor renamings-as-a-body nor body stubs
17119 are counted. Any subprogram body is counted, independently of its nesting
17120 level and enclosing constructs. Generic bodies and bodies of protected
17121 subprograms are counted in the same way as ``usual'' subprogram bodies.
17124 This metric is computed for package specs and
17125 generic package declarations. It is the total number of types
17126 that can be referenced from outside this compilation unit, plus the
17127 number of types from all the visible parts of all the visible generic
17128 packages. Generic formal types are not counted. Only types, not subtypes,
17132 Along with the total number of public types, the following
17133 types are counted and reported separately:
17140 Root tagged types (abstract, non-abstract, private, non-private). Type
17141 extensions are @emph{not} counted
17144 Private types (including private extensions)
17155 This metric is computed for any compilation unit. It is equal to the total
17156 number of the declarations of different types given in the compilation unit.
17157 The private and the corresponding full type declaration are counted as one
17158 type declaration. Incomplete type declarations and generic formal types
17160 No distinction is made among different kinds of types (abstract,
17161 private etc.); the total number of types is computed and reported.
17166 By default, all the syntax metrics are computed and reported. You can use the
17167 following switches to select specific syntax metrics.
17171 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17174 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17177 @item ^--syntax-all^/SYNTAX_METRICS=ALL_ON^
17178 Report all the syntax metrics
17180 @item ^--no-syntax-all^/ALL_OFF^
17181 Do not report any of syntax metrics
17183 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS_ON^
17184 Report the total number of declarations
17186 @item ^--no-declarations^/SYNTAX_METRICS=DECLARATIONS_OFF^
17187 Do not report the total number of declarations
17189 @item ^--statements^/SYNTAX_METRICS=STATEMENTS_ON^
17190 Report the total number of statements
17192 @item ^--no-statements^/SYNTAX_METRICS=STATEMENTS_OFF^
17193 Do not report the total number of statements
17195 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_ON^
17196 Report the number of public subprograms in a compilation unit
17198 @item ^--no-public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS_OFF^
17199 Do not report the number of public subprograms in a compilation unit
17201 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_ON^
17202 Report the number of all the subprograms in a compilation unit
17204 @item ^--no-all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS_OFF^
17205 Do not report the number of all the subprograms in a compilation unit
17207 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES_ON^
17208 Report the number of public types in a compilation unit
17210 @item ^--no-public-types^/SYNTAX_METRICS=PUBLIC_TYPES_OFF^
17211 Do not report the number of public types in a compilation unit
17213 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES_ON^
17214 Report the number of all the types in a compilation unit
17216 @item ^--no-all-types^/SYNTAX_METRICS=ALL_TYPES_OFF^
17217 Do not report the number of all the types in a compilation unit
17219 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_ON^
17220 Report the maximal program unit nesting level
17222 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17223 Do not report the maximal program unit nesting level
17225 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_ON^
17226 Report the maximal construct nesting level
17228 @item ^--no-construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING_OFF^
17229 Do not report the maximal construct nesting level
17233 @node Complexity Metrics Control
17234 @subsubsection Complexity Metrics Control
17235 @cindex Complexity metrics control in @command{gnatmetric}
17238 For a program unit that is an executable body (a subprogram body (including
17239 generic bodies), task body, entry body or a package body containing
17240 its own statement sequence) @command{gnatmetric} computes the following
17241 complexity metrics:
17245 McCabe cyclomatic complexity;
17248 McCabe essential complexity;
17251 maximal loop nesting level
17256 The McCabe complexity metrics are defined
17257 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17259 According to McCabe, both control statements and short-circuit control forms
17260 should be taken into account when computing cyclomatic complexity. For each
17261 body, we compute three metric values:
17265 the complexity introduced by control
17266 statements only, without taking into account short-circuit forms,
17269 the complexity introduced by short-circuit control forms only, and
17273 cyclomatic complexity, which is the sum of these two values.
17277 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17278 the code in the exception handlers and in all the nested program units.
17280 By default, all the complexity metrics are computed and reported.
17281 For more fine-grained control you can use
17282 the following switches:
17285 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17288 @cindex @option{--no-complexity@var{x}}
17291 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL_ON^
17292 Report all the complexity metrics
17294 @item ^--no-complexity-all^/COMPLEXITY_METRICS=ALL_OFF^
17295 Do not report any of complexity metrics
17297 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_ON^
17298 Report the McCabe Cyclomatic Complexity
17300 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC_OFF^
17301 Do not report the McCabe Cyclomatic Complexity
17303 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_ON^
17304 Report the Essential Complexity
17306 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL_OFF^
17307 Do not report the Essential Complexity
17309 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17310 Report maximal loop nesting level
17312 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_OFF^
17313 Do not report maximal loop nesting level
17315 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_ON^
17316 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17317 task bodies, entry bodies and statement sequences in package bodies.
17318 The metric is computed and reported for whole set of processed Ada sources
17321 @item ^--no-complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY_OFF^
17322 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17323 bodies, task bodies, entry bodies and statement sequences in package bodies
17325 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17326 @item ^-ne^/NO_EXITS_AS_GOTOS^
17327 Do not consider @code{exit} statements as @code{goto}s when
17328 computing Essential Complexity
17333 @node Object-Oriented Metrics Control
17334 @subsubsection Object-Oriented Metrics Control
17335 @cindex Object-Oriented metrics control in @command{gnatmetric}
17338 @cindex Coupling metrics (in in @command{gnatmetric})
17339 Coupling metrics are object-oriented metrics that measure the
17340 dependencies between a given class (or a group of classes) and the
17341 ``external world'' (that is, the other classes in the program). In this
17342 subsection the term ``class'' is used in its
17343 traditional object-oriented programming sense
17344 (an instantiable module that contains data and/or method members).
17345 A @emph{category} (of classes)
17346 is a group of closely related classes that are reused and/or
17349 A class @code{K}'s @emph{efferent coupling} is the number of classes
17350 that @code{K} depends upon.
17351 A category's efferent coupling is the number of classes outside the
17352 category that the classes inside the category depend upon.
17354 A class @code{K}'s @emph{afferent coupling} is the number of classes
17355 that depend upon @code{K}.
17356 A category's afferent coupling is the number of classes outside the
17357 category that depend on classes belonging to the category.
17359 Ada's implementation of the object-oriented paradigm does not use the
17360 traditional class notion, so the definition of the coupling
17361 metrics for Ada maps the class and class category notions
17362 onto Ada constructs.
17364 For the coupling metrics, several kinds of modules -- a library package,
17365 a library generic package, and a library generic package instantiation --
17366 that define a tagged type or an interface type are
17367 considered to be a class. A category consists of a library package (or
17368 a library generic package) that defines a tagged or an interface type,
17369 together with all its descendant (generic) packages that define tagged
17370 or interface types. For any package counted as a class,
17371 its body (if any) is considered
17372 together with its spec when counting the dependencies. For dependencies
17373 between classes, the Ada semantic dependencies are considered.
17374 For coupling metrics, only dependencies on units that are considered as
17375 classes, are considered.
17377 When computing coupling metrics, @command{gnatmetric} counts only
17378 dependencies between units that are arguments of the gnatmetric call.
17379 Coupling metrics are program-wide (or project-wide) metrics, so to
17380 get a valid result, you should call @command{gnatmetric} for
17381 the whole set of sources that make up your program. It can be done
17382 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17383 option (see See @ref{The GNAT Driver and Project Files} for details.
17385 By default, all the coupling metrics are disabled. You can use the following
17386 switches to specify the coupling metrics to be computed and reported:
17391 @cindex @option{--package@var{x}} (@command{gnatmetric})
17392 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17393 @cindex @option{--category@var{x}} (@command{gnatmetric})
17394 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17398 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17401 @item ^--coupling-all^/COUPLING_METRICS=ALL_ON^
17402 Report all the coupling metrics
17404 @item ^--no-coupling-all^/COUPLING_METRICS=ALL_OFF^
17405 Do not report any of metrics
17407 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_ON^
17408 Report package efferent coupling
17410 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT_OFF^
17411 Do not report package efferent coupling
17413 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_ON^
17414 Report package afferent coupling
17416 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT_OFF^
17417 Do not report package afferent coupling
17419 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_ON^
17420 Report category efferent coupling
17422 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT_OFF^
17423 Do not report category efferent coupling
17425 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_ON^
17426 Report category afferent coupling
17428 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT_OFF^
17429 Do not report category afferent coupling
17433 @node Other gnatmetric Switches
17434 @subsection Other @code{gnatmetric} Switches
17437 Additional @command{gnatmetric} switches are as follows:
17440 @item ^-files @var{filename}^/FILES=@var{filename}^
17441 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17442 Take the argument source files from the specified file. This file should be an
17443 ordinary text file containing file names separated by spaces or
17444 line breaks. You can use this switch more then once in the same call to
17445 @command{gnatmetric}. You also can combine this switch with
17446 an explicit list of files.
17448 @item ^-v^/VERBOSE^
17449 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17451 @command{gnatmetric} generates version information and then
17452 a trace of sources being processed.
17454 @item ^-dv^/DEBUG_OUTPUT^
17455 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17457 @command{gnatmetric} generates various messages useful to understand what
17458 happens during the metrics computation
17461 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17465 @node Generate project-wide metrics
17466 @subsection Generate project-wide metrics
17468 In order to compute metrics on all units of a given project, you can use
17469 the @command{gnat} driver along with the @option{-P} option:
17475 If the project @code{proj} depends upon other projects, you can compute
17476 the metrics on the project closure using the @option{-U} option:
17478 gnat metric -Pproj -U
17482 Finally, if not all the units are relevant to a particular main
17483 program in the project closure, you can generate metrics for the set
17484 of units needed to create a given main program (unit closure) using
17485 the @option{-U} option followed by the name of the main unit:
17487 gnat metric -Pproj -U main
17491 @c ***********************************
17492 @node File Name Krunching Using gnatkr
17493 @chapter File Name Krunching Using @code{gnatkr}
17497 This chapter discusses the method used by the compiler to shorten
17498 the default file names chosen for Ada units so that they do not
17499 exceed the maximum length permitted. It also describes the
17500 @code{gnatkr} utility that can be used to determine the result of
17501 applying this shortening.
17505 * Krunching Method::
17506 * Examples of gnatkr Usage::
17510 @section About @code{gnatkr}
17513 The default file naming rule in GNAT
17514 is that the file name must be derived from
17515 the unit name. The exact default rule is as follows:
17518 Take the unit name and replace all dots by hyphens.
17520 If such a replacement occurs in the
17521 second character position of a name, and the first character is
17522 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17523 then replace the dot by the character
17524 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17525 instead of a minus.
17527 The reason for this exception is to avoid clashes
17528 with the standard names for children of System, Ada, Interfaces,
17529 and GNAT, which use the prefixes
17530 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17533 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17534 switch of the compiler activates a ``krunching''
17535 circuit that limits file names to nn characters (where nn is a decimal
17536 integer). For example, using OpenVMS,
17537 where the maximum file name length is
17538 39, the value of nn is usually set to 39, but if you want to generate
17539 a set of files that would be usable if ported to a system with some
17540 different maximum file length, then a different value can be specified.
17541 The default value of 39 for OpenVMS need not be specified.
17543 The @code{gnatkr} utility can be used to determine the krunched name for
17544 a given file, when krunched to a specified maximum length.
17547 @section Using @code{gnatkr}
17550 The @code{gnatkr} command has the form
17554 $ gnatkr @var{name} @ovar{length}
17560 $ gnatkr @var{name} /COUNT=nn
17565 @var{name} is the uncrunched file name, derived from the name of the unit
17566 in the standard manner described in the previous section (i.e., in particular
17567 all dots are replaced by hyphens). The file name may or may not have an
17568 extension (defined as a suffix of the form period followed by arbitrary
17569 characters other than period). If an extension is present then it will
17570 be preserved in the output. For example, when krunching @file{hellofile.ads}
17571 to eight characters, the result will be hellofil.ads.
17573 Note: for compatibility with previous versions of @code{gnatkr} dots may
17574 appear in the name instead of hyphens, but the last dot will always be
17575 taken as the start of an extension. So if @code{gnatkr} is given an argument
17576 such as @file{Hello.World.adb} it will be treated exactly as if the first
17577 period had been a hyphen, and for example krunching to eight characters
17578 gives the result @file{hellworl.adb}.
17580 Note that the result is always all lower case (except on OpenVMS where it is
17581 all upper case). Characters of the other case are folded as required.
17583 @var{length} represents the length of the krunched name. The default
17584 when no argument is given is ^8^39^ characters. A length of zero stands for
17585 unlimited, in other words do not chop except for system files where the
17586 implied crunching length is always eight characters.
17589 The output is the krunched name. The output has an extension only if the
17590 original argument was a file name with an extension.
17592 @node Krunching Method
17593 @section Krunching Method
17596 The initial file name is determined by the name of the unit that the file
17597 contains. The name is formed by taking the full expanded name of the
17598 unit and replacing the separating dots with hyphens and
17599 using ^lowercase^uppercase^
17600 for all letters, except that a hyphen in the second character position is
17601 replaced by a ^tilde^dollar sign^ if the first character is
17602 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17603 The extension is @code{.ads} for a
17604 spec and @code{.adb} for a body.
17605 Krunching does not affect the extension, but the file name is shortened to
17606 the specified length by following these rules:
17610 The name is divided into segments separated by hyphens, tildes or
17611 underscores and all hyphens, tildes, and underscores are
17612 eliminated. If this leaves the name short enough, we are done.
17615 If the name is too long, the longest segment is located (left-most
17616 if there are two of equal length), and shortened by dropping
17617 its last character. This is repeated until the name is short enough.
17619 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17620 to fit the name into 8 characters as required by some operating systems.
17623 our-strings-wide_fixed 22
17624 our strings wide fixed 19
17625 our string wide fixed 18
17626 our strin wide fixed 17
17627 our stri wide fixed 16
17628 our stri wide fixe 15
17629 our str wide fixe 14
17630 our str wid fixe 13
17636 Final file name: oustwifi.adb
17640 The file names for all predefined units are always krunched to eight
17641 characters. The krunching of these predefined units uses the following
17642 special prefix replacements:
17646 replaced by @file{^a^A^-}
17649 replaced by @file{^g^G^-}
17652 replaced by @file{^i^I^-}
17655 replaced by @file{^s^S^-}
17658 These system files have a hyphen in the second character position. That
17659 is why normal user files replace such a character with a
17660 ^tilde^dollar sign^, to
17661 avoid confusion with system file names.
17663 As an example of this special rule, consider
17664 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
17667 ada-strings-wide_fixed 22
17668 a- strings wide fixed 18
17669 a- string wide fixed 17
17670 a- strin wide fixed 16
17671 a- stri wide fixed 15
17672 a- stri wide fixe 14
17673 a- str wide fixe 13
17679 Final file name: a-stwifi.adb
17683 Of course no file shortening algorithm can guarantee uniqueness over all
17684 possible unit names, and if file name krunching is used then it is your
17685 responsibility to ensure that no name clashes occur. The utility
17686 program @code{gnatkr} is supplied for conveniently determining the
17687 krunched name of a file.
17689 @node Examples of gnatkr Usage
17690 @section Examples of @code{gnatkr} Usage
17697 $ gnatkr very_long_unit_name.ads --> velounna.ads
17698 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
17699 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
17700 $ gnatkr grandparent-parent-child --> grparchi
17702 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
17703 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
17706 @node Preprocessing Using gnatprep
17707 @chapter Preprocessing Using @code{gnatprep}
17711 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
17713 Although designed for use with GNAT, @code{gnatprep} does not depend on any
17714 special GNAT features.
17715 For further discussion of conditional compilation in general, see
17716 @ref{Conditional Compilation}.
17719 * Preprocessing Symbols::
17721 * Switches for gnatprep::
17722 * Form of Definitions File::
17723 * Form of Input Text for gnatprep::
17726 @node Preprocessing Symbols
17727 @section Preprocessing Symbols
17730 Preprocessing symbols are defined in definition files and referred to in
17731 sources to be preprocessed. A Preprocessing symbol is an identifier, following
17732 normal Ada (case-insensitive) rules for its syntax, with the restriction that
17733 all characters need to be in the ASCII set (no accented letters).
17735 @node Using gnatprep
17736 @section Using @code{gnatprep}
17739 To call @code{gnatprep} use
17742 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
17749 is an optional sequence of switches as described in the next section.
17752 is the full name of the input file, which is an Ada source
17753 file containing preprocessor directives.
17756 is the full name of the output file, which is an Ada source
17757 in standard Ada form. When used with GNAT, this file name will
17758 normally have an ads or adb suffix.
17761 is the full name of a text file containing definitions of
17762 preprocessing symbols to be referenced by the preprocessor. This argument is
17763 optional, and can be replaced by the use of the @option{-D} switch.
17767 @node Switches for gnatprep
17768 @section Switches for @code{gnatprep}
17773 @item ^-b^/BLANK_LINES^
17774 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
17775 Causes both preprocessor lines and the lines deleted by
17776 preprocessing to be replaced by blank lines in the output source file,
17777 preserving line numbers in the output file.
17779 @item ^-c^/COMMENTS^
17780 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
17781 Causes both preprocessor lines and the lines deleted
17782 by preprocessing to be retained in the output source as comments marked
17783 with the special string @code{"--! "}. This option will result in line numbers
17784 being preserved in the output file.
17786 @item ^-C^/REPLACE_IN_COMMENTS^
17787 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
17788 Causes comments to be scanned. Normally comments are ignored by gnatprep.
17789 If this option is specified, then comments are scanned and any $symbol
17790 substitutions performed as in program text. This is particularly useful
17791 when structured comments are used (e.g., when writing programs in the
17792 SPARK dialect of Ada). Note that this switch is not available when
17793 doing integrated preprocessing (it would be useless in this context
17794 since comments are ignored by the compiler in any case).
17796 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
17797 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
17798 Defines a new preprocessing symbol, associated with value. If no value is given
17799 on the command line, then symbol is considered to be @code{True}. This switch
17800 can be used in place of a definition file.
17804 @cindex @option{/REMOVE} (@command{gnatprep})
17805 This is the default setting which causes lines deleted by preprocessing
17806 to be entirely removed from the output file.
17809 @item ^-r^/REFERENCE^
17810 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
17811 Causes a @code{Source_Reference} pragma to be generated that
17812 references the original input file, so that error messages will use
17813 the file name of this original file. The use of this switch implies
17814 that preprocessor lines are not to be removed from the file, so its
17815 use will force @option{^-b^/BLANK_LINES^} mode if
17816 @option{^-c^/COMMENTS^}
17817 has not been specified explicitly.
17819 Note that if the file to be preprocessed contains multiple units, then
17820 it will be necessary to @code{gnatchop} the output file from
17821 @code{gnatprep}. If a @code{Source_Reference} pragma is present
17822 in the preprocessed file, it will be respected by
17823 @code{gnatchop ^-r^/REFERENCE^}
17824 so that the final chopped files will correctly refer to the original
17825 input source file for @code{gnatprep}.
17827 @item ^-s^/SYMBOLS^
17828 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
17829 Causes a sorted list of symbol names and values to be
17830 listed on the standard output file.
17832 @item ^-u^/UNDEFINED^
17833 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
17834 Causes undefined symbols to be treated as having the value FALSE in the context
17835 of a preprocessor test. In the absence of this option, an undefined symbol in
17836 a @code{#if} or @code{#elsif} test will be treated as an error.
17842 Note: if neither @option{-b} nor @option{-c} is present,
17843 then preprocessor lines and
17844 deleted lines are completely removed from the output, unless -r is
17845 specified, in which case -b is assumed.
17848 @node Form of Definitions File
17849 @section Form of Definitions File
17852 The definitions file contains lines of the form
17859 where symbol is a preprocessing symbol, and value is one of the following:
17863 Empty, corresponding to a null substitution
17865 A string literal using normal Ada syntax
17867 Any sequence of characters from the set
17868 (letters, digits, period, underline).
17872 Comment lines may also appear in the definitions file, starting with
17873 the usual @code{--},
17874 and comments may be added to the definitions lines.
17876 @node Form of Input Text for gnatprep
17877 @section Form of Input Text for @code{gnatprep}
17880 The input text may contain preprocessor conditional inclusion lines,
17881 as well as general symbol substitution sequences.
17883 The preprocessor conditional inclusion commands have the form
17888 #if @i{expression} @r{[}then@r{]}
17890 #elsif @i{expression} @r{[}then@r{]}
17892 #elsif @i{expression} @r{[}then@r{]}
17903 In this example, @i{expression} is defined by the following grammar:
17905 @i{expression} ::= <symbol>
17906 @i{expression} ::= <symbol> = "<value>"
17907 @i{expression} ::= <symbol> = <symbol>
17908 @i{expression} ::= <symbol> 'Defined
17909 @i{expression} ::= not @i{expression}
17910 @i{expression} ::= @i{expression} and @i{expression}
17911 @i{expression} ::= @i{expression} or @i{expression}
17912 @i{expression} ::= @i{expression} and then @i{expression}
17913 @i{expression} ::= @i{expression} or else @i{expression}
17914 @i{expression} ::= ( @i{expression} )
17917 The following restriction exists: it is not allowed to have "and" or "or"
17918 following "not" in the same expression without parentheses. For example, this
17925 This should be one of the following:
17933 For the first test (@i{expression} ::= <symbol>) the symbol must have
17934 either the value true or false, that is to say the right-hand of the
17935 symbol definition must be one of the (case-insensitive) literals
17936 @code{True} or @code{False}. If the value is true, then the
17937 corresponding lines are included, and if the value is false, they are
17940 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
17941 the symbol has been defined in the definition file or by a @option{-D}
17942 switch on the command line. Otherwise, the test is false.
17944 The equality tests are case insensitive, as are all the preprocessor lines.
17946 If the symbol referenced is not defined in the symbol definitions file,
17947 then the effect depends on whether or not switch @option{-u}
17948 is specified. If so, then the symbol is treated as if it had the value
17949 false and the test fails. If this switch is not specified, then
17950 it is an error to reference an undefined symbol. It is also an error to
17951 reference a symbol that is defined with a value other than @code{True}
17954 The use of the @code{not} operator inverts the sense of this logical test.
17955 The @code{not} operator cannot be combined with the @code{or} or @code{and}
17956 operators, without parentheses. For example, "if not X or Y then" is not
17957 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
17959 The @code{then} keyword is optional as shown
17961 The @code{#} must be the first non-blank character on a line, but
17962 otherwise the format is free form. Spaces or tabs may appear between
17963 the @code{#} and the keyword. The keywords and the symbols are case
17964 insensitive as in normal Ada code. Comments may be used on a
17965 preprocessor line, but other than that, no other tokens may appear on a
17966 preprocessor line. Any number of @code{elsif} clauses can be present,
17967 including none at all. The @code{else} is optional, as in Ada.
17969 The @code{#} marking the start of a preprocessor line must be the first
17970 non-blank character on the line, i.e., it must be preceded only by
17971 spaces or horizontal tabs.
17973 Symbol substitution outside of preprocessor lines is obtained by using
17981 anywhere within a source line, except in a comment or within a
17982 string literal. The identifier
17983 following the @code{$} must match one of the symbols defined in the symbol
17984 definition file, and the result is to substitute the value of the
17985 symbol in place of @code{$symbol} in the output file.
17987 Note that although the substitution of strings within a string literal
17988 is not possible, it is possible to have a symbol whose defined value is
17989 a string literal. So instead of setting XYZ to @code{hello} and writing:
17992 Header : String := "$XYZ";
17996 you should set XYZ to @code{"hello"} and write:
17999 Header : String := $XYZ;
18003 and then the substitution will occur as desired.
18006 @node The GNAT Run-Time Library Builder gnatlbr
18007 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18009 @cindex Library builder
18012 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18013 supplied configuration pragmas.
18016 * Running gnatlbr::
18017 * Switches for gnatlbr::
18018 * Examples of gnatlbr Usage::
18021 @node Running gnatlbr
18022 @section Running @code{gnatlbr}
18025 The @code{gnatlbr} command has the form
18028 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18031 @node Switches for gnatlbr
18032 @section Switches for @code{gnatlbr}
18035 @code{gnatlbr} recognizes the following switches:
18039 @item /CREATE=directory
18040 @cindex @code{/CREATE} (@code{gnatlbr})
18041 Create the new run-time library in the specified directory.
18043 @item /SET=directory
18044 @cindex @code{/SET} (@code{gnatlbr})
18045 Make the library in the specified directory the current run-time library.
18047 @item /DELETE=directory
18048 @cindex @code{/DELETE} (@code{gnatlbr})
18049 Delete the run-time library in the specified directory.
18052 @cindex @code{/CONFIG} (@code{gnatlbr})
18053 With /CREATE: Use the configuration pragmas in the specified file when
18054 building the library.
18056 With /SET: Use the configuration pragmas in the specified file when
18061 @node Examples of gnatlbr Usage
18062 @section Example of @code{gnatlbr} Usage
18065 Contents of VAXFLOAT.ADC:
18066 pragma Float_Representation (VAX_Float);
18068 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18070 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18075 @node The GNAT Library Browser gnatls
18076 @chapter The GNAT Library Browser @code{gnatls}
18078 @cindex Library browser
18081 @code{gnatls} is a tool that outputs information about compiled
18082 units. It gives the relationship between objects, unit names and source
18083 files. It can also be used to check the source dependencies of a unit
18084 as well as various characteristics.
18086 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18087 driver (see @ref{The GNAT Driver and Project Files}).
18091 * Switches for gnatls::
18092 * Examples of gnatls Usage::
18095 @node Running gnatls
18096 @section Running @code{gnatls}
18099 The @code{gnatls} command has the form
18102 $ gnatls switches @var{object_or_ali_file}
18106 The main argument is the list of object or @file{ali} files
18107 (@pxref{The Ada Library Information Files})
18108 for which information is requested.
18110 In normal mode, without additional option, @code{gnatls} produces a
18111 four-column listing. Each line represents information for a specific
18112 object. The first column gives the full path of the object, the second
18113 column gives the name of the principal unit in this object, the third
18114 column gives the status of the source and the fourth column gives the
18115 full path of the source representing this unit.
18116 Here is a simple example of use:
18120 ^./^[]^demo1.o demo1 DIF demo1.adb
18121 ^./^[]^demo2.o demo2 OK demo2.adb
18122 ^./^[]^hello.o h1 OK hello.adb
18123 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18124 ^./^[]^instr.o instr OK instr.adb
18125 ^./^[]^tef.o tef DIF tef.adb
18126 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18127 ^./^[]^tgef.o tgef DIF tgef.adb
18131 The first line can be interpreted as follows: the main unit which is
18133 object file @file{demo1.o} is demo1, whose main source is in
18134 @file{demo1.adb}. Furthermore, the version of the source used for the
18135 compilation of demo1 has been modified (DIF). Each source file has a status
18136 qualifier which can be:
18139 @item OK (unchanged)
18140 The version of the source file used for the compilation of the
18141 specified unit corresponds exactly to the actual source file.
18143 @item MOK (slightly modified)
18144 The version of the source file used for the compilation of the
18145 specified unit differs from the actual source file but not enough to
18146 require recompilation. If you use gnatmake with the qualifier
18147 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18148 MOK will not be recompiled.
18150 @item DIF (modified)
18151 No version of the source found on the path corresponds to the source
18152 used to build this object.
18154 @item ??? (file not found)
18155 No source file was found for this unit.
18157 @item HID (hidden, unchanged version not first on PATH)
18158 The version of the source that corresponds exactly to the source used
18159 for compilation has been found on the path but it is hidden by another
18160 version of the same source that has been modified.
18164 @node Switches for gnatls
18165 @section Switches for @code{gnatls}
18168 @code{gnatls} recognizes the following switches:
18172 @cindex @option{--version} @command{gnatls}
18173 Display Copyright and version, then exit disregarding all other options.
18176 @cindex @option{--help} @command{gnatls}
18177 If @option{--version} was not used, display usage, then exit disregarding
18180 @item ^-a^/ALL_UNITS^
18181 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18182 Consider all units, including those of the predefined Ada library.
18183 Especially useful with @option{^-d^/DEPENDENCIES^}.
18185 @item ^-d^/DEPENDENCIES^
18186 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18187 List sources from which specified units depend on.
18189 @item ^-h^/OUTPUT=OPTIONS^
18190 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18191 Output the list of options.
18193 @item ^-o^/OUTPUT=OBJECTS^
18194 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18195 Only output information about object files.
18197 @item ^-s^/OUTPUT=SOURCES^
18198 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18199 Only output information about source files.
18201 @item ^-u^/OUTPUT=UNITS^
18202 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18203 Only output information about compilation units.
18205 @item ^-files^/FILES^=@var{file}
18206 @cindex @option{^-files^/FILES^} (@code{gnatls})
18207 Take as arguments the files listed in text file @var{file}.
18208 Text file @var{file} may contain empty lines that are ignored.
18209 Each nonempty line should contain the name of an existing file.
18210 Several such switches may be specified simultaneously.
18212 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18213 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18214 @itemx ^-I^/SEARCH=^@var{dir}
18215 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18217 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18218 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18219 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18220 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18221 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18222 flags (@pxref{Switches for gnatmake}).
18224 @item --RTS=@var{rts-path}
18225 @cindex @option{--RTS} (@code{gnatls})
18226 Specifies the default location of the runtime library. Same meaning as the
18227 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18229 @item ^-v^/OUTPUT=VERBOSE^
18230 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18231 Verbose mode. Output the complete source, object and project paths. Do not use
18232 the default column layout but instead use long format giving as much as
18233 information possible on each requested units, including special
18234 characteristics such as:
18237 @item Preelaborable
18238 The unit is preelaborable in the Ada sense.
18241 No elaboration code has been produced by the compiler for this unit.
18244 The unit is pure in the Ada sense.
18246 @item Elaborate_Body
18247 The unit contains a pragma Elaborate_Body.
18250 The unit contains a pragma Remote_Types.
18252 @item Shared_Passive
18253 The unit contains a pragma Shared_Passive.
18256 This unit is part of the predefined environment and cannot be modified
18259 @item Remote_Call_Interface
18260 The unit contains a pragma Remote_Call_Interface.
18266 @node Examples of gnatls Usage
18267 @section Example of @code{gnatls} Usage
18271 Example of using the verbose switch. Note how the source and
18272 object paths are affected by the -I switch.
18275 $ gnatls -v -I.. demo1.o
18277 GNATLS 5.03w (20041123-34)
18278 Copyright 1997-2004 Free Software Foundation, Inc.
18280 Source Search Path:
18281 <Current_Directory>
18283 /home/comar/local/adainclude/
18285 Object Search Path:
18286 <Current_Directory>
18288 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18290 Project Search Path:
18291 <Current_Directory>
18292 /home/comar/local/lib/gnat/
18297 Kind => subprogram body
18298 Flags => No_Elab_Code
18299 Source => demo1.adb modified
18303 The following is an example of use of the dependency list.
18304 Note the use of the -s switch
18305 which gives a straight list of source files. This can be useful for
18306 building specialized scripts.
18309 $ gnatls -d demo2.o
18310 ./demo2.o demo2 OK demo2.adb
18316 $ gnatls -d -s -a demo1.o
18318 /home/comar/local/adainclude/ada.ads
18319 /home/comar/local/adainclude/a-finali.ads
18320 /home/comar/local/adainclude/a-filico.ads
18321 /home/comar/local/adainclude/a-stream.ads
18322 /home/comar/local/adainclude/a-tags.ads
18325 /home/comar/local/adainclude/gnat.ads
18326 /home/comar/local/adainclude/g-io.ads
18328 /home/comar/local/adainclude/system.ads
18329 /home/comar/local/adainclude/s-exctab.ads
18330 /home/comar/local/adainclude/s-finimp.ads
18331 /home/comar/local/adainclude/s-finroo.ads
18332 /home/comar/local/adainclude/s-secsta.ads
18333 /home/comar/local/adainclude/s-stalib.ads
18334 /home/comar/local/adainclude/s-stoele.ads
18335 /home/comar/local/adainclude/s-stratt.ads
18336 /home/comar/local/adainclude/s-tasoli.ads
18337 /home/comar/local/adainclude/s-unstyp.ads
18338 /home/comar/local/adainclude/unchconv.ads
18344 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18346 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18347 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18348 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18349 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18350 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18354 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18355 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18357 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18358 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18359 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18360 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
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18371 @node Cleaning Up Using gnatclean
18372 @chapter Cleaning Up Using @code{gnatclean}
18374 @cindex Cleaning tool
18377 @code{gnatclean} is a tool that allows the deletion of files produced by the
18378 compiler, binder and linker, including ALI files, object files, tree files,
18379 expanded source files, library files, interface copy source files, binder
18380 generated files and executable files.
18383 * Running gnatclean::
18384 * Switches for gnatclean::
18385 @c * Examples of gnatclean Usage::
18388 @node Running gnatclean
18389 @section Running @code{gnatclean}
18392 The @code{gnatclean} command has the form:
18395 $ gnatclean switches @var{names}
18399 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18400 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18401 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18404 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18405 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18406 the linker. In informative-only mode, specified by switch
18407 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18408 normal mode is listed, but no file is actually deleted.
18410 @node Switches for gnatclean
18411 @section Switches for @code{gnatclean}
18414 @code{gnatclean} recognizes the following switches:
18418 @cindex @option{--version} @command{gnatclean}
18419 Display Copyright and version, then exit disregarding all other options.
18422 @cindex @option{--help} @command{gnatclean}
18423 If @option{--version} was not used, display usage, then exit disregarding
18426 @item ^-c^/COMPILER_FILES_ONLY^
18427 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18428 Only attempt to delete the files produced by the compiler, not those produced
18429 by the binder or the linker. The files that are not to be deleted are library
18430 files, interface copy files, binder generated files and executable files.
18432 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18433 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18434 Indicate that ALI and object files should normally be found in directory
18437 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18438 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18439 When using project files, if some errors or warnings are detected during
18440 parsing and verbose mode is not in effect (no use of switch
18441 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18442 file, rather than its simple file name.
18445 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18446 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18448 @item ^-n^/NODELETE^
18449 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18450 Informative-only mode. Do not delete any files. Output the list of the files
18451 that would have been deleted if this switch was not specified.
18453 @item ^-P^/PROJECT_FILE=^@var{project}
18454 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18455 Use project file @var{project}. Only one such switch can be used.
18456 When cleaning a project file, the files produced by the compilation of the
18457 immediate sources or inherited sources of the project files are to be
18458 deleted. This is not depending on the presence or not of executable names
18459 on the command line.
18462 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18463 Quiet output. If there are no errors, do not output anything, except in
18464 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18465 (switch ^-n^/NODELETE^).
18467 @item ^-r^/RECURSIVE^
18468 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18469 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18470 clean all imported and extended project files, recursively. If this switch
18471 is not specified, only the files related to the main project file are to be
18472 deleted. This switch has no effect if no project file is specified.
18474 @item ^-v^/VERBOSE^
18475 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18478 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18479 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18480 Indicates the verbosity of the parsing of GNAT project files.
18481 @xref{Switches Related to Project Files}.
18483 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18484 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18485 Indicates that external variable @var{name} has the value @var{value}.
18486 The Project Manager will use this value for occurrences of
18487 @code{external(name)} when parsing the project file.
18488 @xref{Switches Related to Project Files}.
18490 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18491 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18492 When searching for ALI and object files, look in directory
18495 @item ^-I^/SEARCH=^@var{dir}
18496 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18497 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18499 @item ^-I-^/NOCURRENT_DIRECTORY^
18500 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18501 @cindex Source files, suppressing search
18502 Do not look for ALI or object files in the directory
18503 where @code{gnatclean} was invoked.
18507 @c @node Examples of gnatclean Usage
18508 @c @section Examples of @code{gnatclean} Usage
18511 @node GNAT and Libraries
18512 @chapter GNAT and Libraries
18513 @cindex Library, building, installing, using
18516 This chapter describes how to build and use libraries with GNAT, and also shows
18517 how to recompile the GNAT run-time library. You should be familiar with the
18518 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18522 * Introduction to Libraries in GNAT::
18523 * General Ada Libraries::
18524 * Stand-alone Ada Libraries::
18525 * Rebuilding the GNAT Run-Time Library::
18528 @node Introduction to Libraries in GNAT
18529 @section Introduction to Libraries in GNAT
18532 A library is, conceptually, a collection of objects which does not have its
18533 own main thread of execution, but rather provides certain services to the
18534 applications that use it. A library can be either statically linked with the
18535 application, in which case its code is directly included in the application,
18536 or, on platforms that support it, be dynamically linked, in which case
18537 its code is shared by all applications making use of this library.
18539 GNAT supports both types of libraries.
18540 In the static case, the compiled code can be provided in different ways. The
18541 simplest approach is to provide directly the set of objects resulting from
18542 compilation of the library source files. Alternatively, you can group the
18543 objects into an archive using whatever commands are provided by the operating
18544 system. For the latter case, the objects are grouped into a shared library.
18546 In the GNAT environment, a library has three types of components:
18552 @xref{The Ada Library Information Files}.
18554 Object files, an archive or a shared library.
18558 A GNAT library may expose all its source files, which is useful for
18559 documentation purposes. Alternatively, it may expose only the units needed by
18560 an external user to make use of the library. That is to say, the specs
18561 reflecting the library services along with all the units needed to compile
18562 those specs, which can include generic bodies or any body implementing an
18563 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18564 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18566 All compilation units comprising an application, including those in a library,
18567 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18568 computes the elaboration order from the @file{ALI} files and this is why they
18569 constitute a mandatory part of GNAT libraries. Except in the case of
18570 @emph{stand-alone libraries}, where a specific library elaboration routine is
18571 produced independently of the application(s) using the library.
18573 @node General Ada Libraries
18574 @section General Ada Libraries
18577 * Building a library::
18578 * Installing a library::
18579 * Using a library::
18582 @node Building a library
18583 @subsection Building a library
18586 The easiest way to build a library is to use the Project Manager,
18587 which supports a special type of project called a @emph{Library Project}
18588 (@pxref{Library Projects}).
18590 A project is considered a library project, when two project-level attributes
18591 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18592 control different aspects of library configuration, additional optional
18593 project-level attributes can be specified:
18596 This attribute controls whether the library is to be static or dynamic
18598 @item Library_Version
18599 This attribute specifies the library version; this value is used
18600 during dynamic linking of shared libraries to determine if the currently
18601 installed versions of the binaries are compatible.
18603 @item Library_Options
18605 These attributes specify additional low-level options to be used during
18606 library generation, and redefine the actual application used to generate
18611 The GNAT Project Manager takes full care of the library maintenance task,
18612 including recompilation of the source files for which objects do not exist
18613 or are not up to date, assembly of the library archive, and installation of
18614 the library (i.e., copying associated source, object and @file{ALI} files
18615 to the specified location).
18617 Here is a simple library project file:
18618 @smallexample @c ada
18620 for Source_Dirs use ("src1", "src2");
18621 for Object_Dir use "obj";
18622 for Library_Name use "mylib";
18623 for Library_Dir use "lib";
18624 for Library_Kind use "dynamic";
18629 and the compilation command to build and install the library:
18631 @smallexample @c ada
18632 $ gnatmake -Pmy_lib
18636 It is not entirely trivial to perform manually all the steps required to
18637 produce a library. We recommend that you use the GNAT Project Manager
18638 for this task. In special cases where this is not desired, the necessary
18639 steps are discussed below.
18641 There are various possibilities for compiling the units that make up the
18642 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18643 with a conventional script. For simple libraries, it is also possible to create
18644 a dummy main program which depends upon all the packages that comprise the
18645 interface of the library. This dummy main program can then be given to
18646 @command{gnatmake}, which will ensure that all necessary objects are built.
18648 After this task is accomplished, you should follow the standard procedure
18649 of the underlying operating system to produce the static or shared library.
18651 Here is an example of such a dummy program:
18652 @smallexample @c ada
18654 with My_Lib.Service1;
18655 with My_Lib.Service2;
18656 with My_Lib.Service3;
18657 procedure My_Lib_Dummy is
18665 Here are the generic commands that will build an archive or a shared library.
18668 # compiling the library
18669 $ gnatmake -c my_lib_dummy.adb
18671 # we don't need the dummy object itself
18672 $ rm my_lib_dummy.o my_lib_dummy.ali
18674 # create an archive with the remaining objects
18675 $ ar rc libmy_lib.a *.o
18676 # some systems may require "ranlib" to be run as well
18678 # or create a shared library
18679 $ gcc -shared -o libmy_lib.so *.o
18680 # some systems may require the code to have been compiled with -fPIC
18682 # remove the object files that are now in the library
18685 # Make the ALI files read-only so that gnatmake will not try to
18686 # regenerate the objects that are in the library
18691 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
18692 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
18693 be accessed by the directive @option{-l@var{xxx}} at link time.
18695 @node Installing a library
18696 @subsection Installing a library
18697 @cindex @code{ADA_PROJECT_PATH}
18700 If you use project files, library installation is part of the library build
18701 process. Thus no further action is needed in order to make use of the
18702 libraries that are built as part of the general application build. A usable
18703 version of the library is installed in the directory specified by the
18704 @code{Library_Dir} attribute of the library project file.
18706 You may want to install a library in a context different from where the library
18707 is built. This situation arises with third party suppliers, who may want
18708 to distribute a library in binary form where the user is not expected to be
18709 able to recompile the library. The simplest option in this case is to provide
18710 a project file slightly different from the one used to build the library, by
18711 using the @code{externally_built} attribute. For instance, the project
18712 file used to build the library in the previous section can be changed into the
18713 following one when the library is installed:
18715 @smallexample @c projectfile
18717 for Source_Dirs use ("src1", "src2");
18718 for Library_Name use "mylib";
18719 for Library_Dir use "lib";
18720 for Library_Kind use "dynamic";
18721 for Externally_Built use "true";
18726 This project file assumes that the directories @file{src1},
18727 @file{src2}, and @file{lib} exist in
18728 the directory containing the project file. The @code{externally_built}
18729 attribute makes it clear to the GNAT builder that it should not attempt to
18730 recompile any of the units from this library. It allows the library provider to
18731 restrict the source set to the minimum necessary for clients to make use of the
18732 library as described in the first section of this chapter. It is the
18733 responsibility of the library provider to install the necessary sources, ALI
18734 files and libraries in the directories mentioned in the project file. For
18735 convenience, the user's library project file should be installed in a location
18736 that will be searched automatically by the GNAT
18737 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
18738 environment variable (@pxref{Importing Projects}), and also the default GNAT
18739 library location that can be queried with @command{gnatls -v} and is usually of
18740 the form $gnat_install_root/lib/gnat.
18742 When project files are not an option, it is also possible, but not recommended,
18743 to install the library so that the sources needed to use the library are on the
18744 Ada source path and the ALI files & libraries be on the Ada Object path (see
18745 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
18746 administrator can place general-purpose libraries in the default compiler
18747 paths, by specifying the libraries' location in the configuration files
18748 @file{ada_source_path} and @file{ada_object_path}. These configuration files
18749 must be located in the GNAT installation tree at the same place as the gcc spec
18750 file. The location of the gcc spec file can be determined as follows:
18756 The configuration files mentioned above have a simple format: each line
18757 must contain one unique directory name.
18758 Those names are added to the corresponding path
18759 in their order of appearance in the file. The names can be either absolute
18760 or relative; in the latter case, they are relative to where theses files
18763 The files @file{ada_source_path} and @file{ada_object_path} might not be
18765 GNAT installation, in which case, GNAT will look for its run-time library in
18766 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
18767 objects and @file{ALI} files). When the files exist, the compiler does not
18768 look in @file{adainclude} and @file{adalib}, and thus the
18769 @file{ada_source_path} file
18770 must contain the location for the GNAT run-time sources (which can simply
18771 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
18772 contain the location for the GNAT run-time objects (which can simply
18775 You can also specify a new default path to the run-time library at compilation
18776 time with the switch @option{--RTS=rts-path}. You can thus choose / change
18777 the run-time library you want your program to be compiled with. This switch is
18778 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
18779 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
18781 It is possible to install a library before or after the standard GNAT
18782 library, by reordering the lines in the configuration files. In general, a
18783 library must be installed before the GNAT library if it redefines
18786 @node Using a library
18787 @subsection Using a library
18789 @noindent Once again, the project facility greatly simplifies the use of
18790 libraries. In this context, using a library is just a matter of adding a
18791 @code{with} clause in the user project. For instance, to make use of the
18792 library @code{My_Lib} shown in examples in earlier sections, you can
18795 @smallexample @c projectfile
18802 Even if you have a third-party, non-Ada library, you can still use GNAT's
18803 Project Manager facility to provide a wrapper for it. For example, the
18804 following project, when @code{with}ed by your main project, will link with the
18805 third-party library @file{liba.a}:
18807 @smallexample @c projectfile
18810 for Externally_Built use "true";
18811 for Source_Files use ();
18812 for Library_Dir use "lib";
18813 for Library_Name use "a";
18814 for Library_Kind use "static";
18818 This is an alternative to the use of @code{pragma Linker_Options}. It is
18819 especially interesting in the context of systems with several interdependent
18820 static libraries where finding a proper linker order is not easy and best be
18821 left to the tools having visibility over project dependence information.
18824 In order to use an Ada library manually, you need to make sure that this
18825 library is on both your source and object path
18826 (see @ref{Search Paths and the Run-Time Library (RTL)}
18827 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
18828 in an archive or a shared library, you need to specify the desired
18829 library at link time.
18831 For example, you can use the library @file{mylib} installed in
18832 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
18835 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
18840 This can be expressed more simply:
18845 when the following conditions are met:
18848 @file{/dir/my_lib_src} has been added by the user to the environment
18849 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
18850 @file{ada_source_path}
18852 @file{/dir/my_lib_obj} has been added by the user to the environment
18853 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
18854 @file{ada_object_path}
18856 a pragma @code{Linker_Options} has been added to one of the sources.
18859 @smallexample @c ada
18860 pragma Linker_Options ("-lmy_lib");
18864 @node Stand-alone Ada Libraries
18865 @section Stand-alone Ada Libraries
18866 @cindex Stand-alone library, building, using
18869 * Introduction to Stand-alone Libraries::
18870 * Building a Stand-alone Library::
18871 * Creating a Stand-alone Library to be used in a non-Ada context::
18872 * Restrictions in Stand-alone Libraries::
18875 @node Introduction to Stand-alone Libraries
18876 @subsection Introduction to Stand-alone Libraries
18879 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
18881 elaborate the Ada units that are included in the library. In contrast with
18882 an ordinary library, which consists of all sources, objects and @file{ALI}
18884 library, a SAL may specify a restricted subset of compilation units
18885 to serve as a library interface. In this case, the fully
18886 self-sufficient set of files will normally consist of an objects
18887 archive, the sources of interface units' specs, and the @file{ALI}
18888 files of interface units.
18889 If an interface spec contains a generic unit or an inlined subprogram,
18891 source must also be provided; if the units that must be provided in the source
18892 form depend on other units, the source and @file{ALI} files of those must
18895 The main purpose of a SAL is to minimize the recompilation overhead of client
18896 applications when a new version of the library is installed. Specifically,
18897 if the interface sources have not changed, client applications do not need to
18898 be recompiled. If, furthermore, a SAL is provided in the shared form and its
18899 version, controlled by @code{Library_Version} attribute, is not changed,
18900 then the clients do not need to be relinked.
18902 SALs also allow the library providers to minimize the amount of library source
18903 text exposed to the clients. Such ``information hiding'' might be useful or
18904 necessary for various reasons.
18906 Stand-alone libraries are also well suited to be used in an executable whose
18907 main routine is not written in Ada.
18909 @node Building a Stand-alone Library
18910 @subsection Building a Stand-alone Library
18913 GNAT's Project facility provides a simple way of building and installing
18914 stand-alone libraries; see @ref{Stand-alone Library Projects}.
18915 To be a Stand-alone Library Project, in addition to the two attributes
18916 that make a project a Library Project (@code{Library_Name} and
18917 @code{Library_Dir}; see @ref{Library Projects}), the attribute
18918 @code{Library_Interface} must be defined. For example:
18920 @smallexample @c projectfile
18922 for Library_Dir use "lib_dir";
18923 for Library_Name use "dummy";
18924 for Library_Interface use ("int1", "int1.child");
18929 Attribute @code{Library_Interface} has a non-empty string list value,
18930 each string in the list designating a unit contained in an immediate source
18931 of the project file.
18933 When a Stand-alone Library is built, first the binder is invoked to build
18934 a package whose name depends on the library name
18935 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
18936 This binder-generated package includes initialization and
18937 finalization procedures whose
18938 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
18940 above). The object corresponding to this package is included in the library.
18942 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
18943 calling of these procedures if a static SAL is built, or if a shared SAL
18945 with the project-level attribute @code{Library_Auto_Init} set to
18948 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
18949 (those that are listed in attribute @code{Library_Interface}) are copied to
18950 the Library Directory. As a consequence, only the Interface Units may be
18951 imported from Ada units outside of the library. If other units are imported,
18952 the binding phase will fail.
18954 The attribute @code{Library_Src_Dir} may be specified for a
18955 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
18956 single string value. Its value must be the path (absolute or relative to the
18957 project directory) of an existing directory. This directory cannot be the
18958 object directory or one of the source directories, but it can be the same as
18959 the library directory. The sources of the Interface
18960 Units of the library that are needed by an Ada client of the library will be
18961 copied to the designated directory, called the Interface Copy directory.
18962 These sources include the specs of the Interface Units, but they may also
18963 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
18964 are used, or when there is a generic unit in the spec. Before the sources
18965 are copied to the Interface Copy directory, an attempt is made to delete all
18966 files in the Interface Copy directory.
18968 Building stand-alone libraries by hand is somewhat tedious, but for those
18969 occasions when it is necessary here are the steps that you need to perform:
18972 Compile all library sources.
18975 Invoke the binder with the switch @option{-n} (No Ada main program),
18976 with all the @file{ALI} files of the interfaces, and
18977 with the switch @option{-L} to give specific names to the @code{init}
18978 and @code{final} procedures. For example:
18980 gnatbind -n int1.ali int2.ali -Lsal1
18984 Compile the binder generated file:
18990 Link the dynamic library with all the necessary object files,
18991 indicating to the linker the names of the @code{init} (and possibly
18992 @code{final}) procedures for automatic initialization (and finalization).
18993 The built library should be placed in a directory different from
18994 the object directory.
18997 Copy the @code{ALI} files of the interface to the library directory,
18998 add in this copy an indication that it is an interface to a SAL
18999 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19000 with letter ``P'') and make the modified copy of the @file{ALI} file
19005 Using SALs is not different from using other libraries
19006 (see @ref{Using a library}).
19008 @node Creating a Stand-alone Library to be used in a non-Ada context
19009 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19012 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19015 The only extra step required is to ensure that library interface subprograms
19016 are compatible with the main program, by means of @code{pragma Export}
19017 or @code{pragma Convention}.
19019 Here is an example of simple library interface for use with C main program:
19021 @smallexample @c ada
19022 package Interface is
19024 procedure Do_Something;
19025 pragma Export (C, Do_Something, "do_something");
19027 procedure Do_Something_Else;
19028 pragma Export (C, Do_Something_Else, "do_something_else");
19034 On the foreign language side, you must provide a ``foreign'' view of the
19035 library interface; remember that it should contain elaboration routines in
19036 addition to interface subprograms.
19038 The example below shows the content of @code{mylib_interface.h} (note
19039 that there is no rule for the naming of this file, any name can be used)
19041 /* the library elaboration procedure */
19042 extern void mylibinit (void);
19044 /* the library finalization procedure */
19045 extern void mylibfinal (void);
19047 /* the interface exported by the library */
19048 extern void do_something (void);
19049 extern void do_something_else (void);
19053 Libraries built as explained above can be used from any program, provided
19054 that the elaboration procedures (named @code{mylibinit} in the previous
19055 example) are called before the library services are used. Any number of
19056 libraries can be used simultaneously, as long as the elaboration
19057 procedure of each library is called.
19059 Below is an example of a C program that uses the @code{mylib} library.
19062 #include "mylib_interface.h"
19067 /* First, elaborate the library before using it */
19070 /* Main program, using the library exported entities */
19072 do_something_else ();
19074 /* Library finalization at the end of the program */
19081 Note that invoking any library finalization procedure generated by
19082 @code{gnatbind} shuts down the Ada run-time environment.
19084 finalization of all Ada libraries must be performed at the end of the program.
19085 No call to these libraries or to the Ada run-time library should be made
19086 after the finalization phase.
19088 @node Restrictions in Stand-alone Libraries
19089 @subsection Restrictions in Stand-alone Libraries
19092 The pragmas listed below should be used with caution inside libraries,
19093 as they can create incompatibilities with other Ada libraries:
19095 @item pragma @code{Locking_Policy}
19096 @item pragma @code{Queuing_Policy}
19097 @item pragma @code{Task_Dispatching_Policy}
19098 @item pragma @code{Unreserve_All_Interrupts}
19102 When using a library that contains such pragmas, the user must make sure
19103 that all libraries use the same pragmas with the same values. Otherwise,
19104 @code{Program_Error} will
19105 be raised during the elaboration of the conflicting
19106 libraries. The usage of these pragmas and its consequences for the user
19107 should therefore be well documented.
19109 Similarly, the traceback in the exception occurrence mechanism should be
19110 enabled or disabled in a consistent manner across all libraries.
19111 Otherwise, Program_Error will be raised during the elaboration of the
19112 conflicting libraries.
19114 If the @code{Version} or @code{Body_Version}
19115 attributes are used inside a library, then you need to
19116 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19117 libraries, so that version identifiers can be properly computed.
19118 In practice these attributes are rarely used, so this is unlikely
19119 to be a consideration.
19121 @node Rebuilding the GNAT Run-Time Library
19122 @section Rebuilding the GNAT Run-Time Library
19123 @cindex GNAT Run-Time Library, rebuilding
19124 @cindex Building the GNAT Run-Time Library
19125 @cindex Rebuilding the GNAT Run-Time Library
19126 @cindex Run-Time Library, rebuilding
19129 It may be useful to recompile the GNAT library in various contexts, the
19130 most important one being the use of partition-wide configuration pragmas
19131 such as @code{Normalize_Scalars}. A special Makefile called
19132 @code{Makefile.adalib} is provided to that effect and can be found in
19133 the directory containing the GNAT library. The location of this
19134 directory depends on the way the GNAT environment has been installed and can
19135 be determined by means of the command:
19142 The last entry in the object search path usually contains the
19143 gnat library. This Makefile contains its own documentation and in
19144 particular the set of instructions needed to rebuild a new library and
19147 @node Using the GNU make Utility
19148 @chapter Using the GNU @code{make} Utility
19152 This chapter offers some examples of makefiles that solve specific
19153 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19154 make, make, GNU @code{make}}), nor does it try to replace the
19155 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19157 All the examples in this section are specific to the GNU version of
19158 make. Although @command{make} is a standard utility, and the basic language
19159 is the same, these examples use some advanced features found only in
19163 * Using gnatmake in a Makefile::
19164 * Automatically Creating a List of Directories::
19165 * Generating the Command Line Switches::
19166 * Overcoming Command Line Length Limits::
19169 @node Using gnatmake in a Makefile
19170 @section Using gnatmake in a Makefile
19175 Complex project organizations can be handled in a very powerful way by
19176 using GNU make combined with gnatmake. For instance, here is a Makefile
19177 which allows you to build each subsystem of a big project into a separate
19178 shared library. Such a makefile allows you to significantly reduce the link
19179 time of very big applications while maintaining full coherence at
19180 each step of the build process.
19182 The list of dependencies are handled automatically by
19183 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19184 the appropriate directories.
19186 Note that you should also read the example on how to automatically
19187 create the list of directories
19188 (@pxref{Automatically Creating a List of Directories})
19189 which might help you in case your project has a lot of subdirectories.
19194 @font@heightrm=cmr8
19197 ## This Makefile is intended to be used with the following directory
19199 ## - The sources are split into a series of csc (computer software components)
19200 ## Each of these csc is put in its own directory.
19201 ## Their name are referenced by the directory names.
19202 ## They will be compiled into shared library (although this would also work
19203 ## with static libraries
19204 ## - The main program (and possibly other packages that do not belong to any
19205 ## csc is put in the top level directory (where the Makefile is).
19206 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19207 ## \_ second_csc (sources) __ lib (will contain the library)
19209 ## Although this Makefile is build for shared library, it is easy to modify
19210 ## to build partial link objects instead (modify the lines with -shared and
19213 ## With this makefile, you can change any file in the system or add any new
19214 ## file, and everything will be recompiled correctly (only the relevant shared
19215 ## objects will be recompiled, and the main program will be re-linked).
19217 # The list of computer software component for your project. This might be
19218 # generated automatically.
19221 # Name of the main program (no extension)
19224 # If we need to build objects with -fPIC, uncomment the following line
19227 # The following variable should give the directory containing libgnat.so
19228 # You can get this directory through 'gnatls -v'. This is usually the last
19229 # directory in the Object_Path.
19232 # The directories for the libraries
19233 # (This macro expands the list of CSC to the list of shared libraries, you
19234 # could simply use the expanded form:
19235 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19236 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19238 $@{MAIN@}: objects $@{LIB_DIR@}
19239 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19240 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19243 # recompile the sources
19244 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19246 # Note: In a future version of GNAT, the following commands will be simplified
19247 # by a new tool, gnatmlib
19249 mkdir -p $@{dir $@@ @}
19250 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19251 cd $@{dir $@@ @} && cp -f ../*.ali .
19253 # The dependencies for the modules
19254 # Note that we have to force the expansion of *.o, since in some cases
19255 # make won't be able to do it itself.
19256 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19257 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19258 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19260 # Make sure all of the shared libraries are in the path before starting the
19263 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19266 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19267 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19268 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19269 $@{RM@} *.o *.ali $@{MAIN@}
19272 @node Automatically Creating a List of Directories
19273 @section Automatically Creating a List of Directories
19276 In most makefiles, you will have to specify a list of directories, and
19277 store it in a variable. For small projects, it is often easier to
19278 specify each of them by hand, since you then have full control over what
19279 is the proper order for these directories, which ones should be
19282 However, in larger projects, which might involve hundreds of
19283 subdirectories, it might be more convenient to generate this list
19286 The example below presents two methods. The first one, although less
19287 general, gives you more control over the list. It involves wildcard
19288 characters, that are automatically expanded by @command{make}. Its
19289 shortcoming is that you need to explicitly specify some of the
19290 organization of your project, such as for instance the directory tree
19291 depth, whether some directories are found in a separate tree, @enddots{}
19293 The second method is the most general one. It requires an external
19294 program, called @command{find}, which is standard on all Unix systems. All
19295 the directories found under a given root directory will be added to the
19301 @font@heightrm=cmr8
19304 # The examples below are based on the following directory hierarchy:
19305 # All the directories can contain any number of files
19306 # ROOT_DIRECTORY -> a -> aa -> aaa
19309 # -> b -> ba -> baa
19312 # This Makefile creates a variable called DIRS, that can be reused any time
19313 # you need this list (see the other examples in this section)
19315 # The root of your project's directory hierarchy
19319 # First method: specify explicitly the list of directories
19320 # This allows you to specify any subset of all the directories you need.
19323 DIRS := a/aa/ a/ab/ b/ba/
19326 # Second method: use wildcards
19327 # Note that the argument(s) to wildcard below should end with a '/'.
19328 # Since wildcards also return file names, we have to filter them out
19329 # to avoid duplicate directory names.
19330 # We thus use make's @code{dir} and @code{sort} functions.
19331 # It sets DIRs to the following value (note that the directories aaa and baa
19332 # are not given, unless you change the arguments to wildcard).
19333 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19336 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19337 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19340 # Third method: use an external program
19341 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19342 # This is the most complete command: it sets DIRs to the following value:
19343 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19346 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19350 @node Generating the Command Line Switches
19351 @section Generating the Command Line Switches
19354 Once you have created the list of directories as explained in the
19355 previous section (@pxref{Automatically Creating a List of Directories}),
19356 you can easily generate the command line arguments to pass to gnatmake.
19358 For the sake of completeness, this example assumes that the source path
19359 is not the same as the object path, and that you have two separate lists
19363 # see "Automatically creating a list of directories" to create
19368 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19369 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19372 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19375 @node Overcoming Command Line Length Limits
19376 @section Overcoming Command Line Length Limits
19379 One problem that might be encountered on big projects is that many
19380 operating systems limit the length of the command line. It is thus hard to give
19381 gnatmake the list of source and object directories.
19383 This example shows how you can set up environment variables, which will
19384 make @command{gnatmake} behave exactly as if the directories had been
19385 specified on the command line, but have a much higher length limit (or
19386 even none on most systems).
19388 It assumes that you have created a list of directories in your Makefile,
19389 using one of the methods presented in
19390 @ref{Automatically Creating a List of Directories}.
19391 For the sake of completeness, we assume that the object
19392 path (where the ALI files are found) is different from the sources patch.
19394 Note a small trick in the Makefile below: for efficiency reasons, we
19395 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19396 expanded immediately by @code{make}. This way we overcome the standard
19397 make behavior which is to expand the variables only when they are
19400 On Windows, if you are using the standard Windows command shell, you must
19401 replace colons with semicolons in the assignments to these variables.
19406 @font@heightrm=cmr8
19409 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19410 # This is the same thing as putting the -I arguments on the command line.
19411 # (the equivalent of using -aI on the command line would be to define
19412 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19413 # You can of course have different values for these variables.
19415 # Note also that we need to keep the previous values of these variables, since
19416 # they might have been set before running 'make' to specify where the GNAT
19417 # library is installed.
19419 # see "Automatically creating a list of directories" to create these
19425 space:=$@{empty@} $@{empty@}
19426 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19427 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19428 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19429 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19430 export ADA_INCLUDE_PATH
19431 export ADA_OBJECT_PATH
19438 @node Memory Management Issues
19439 @chapter Memory Management Issues
19442 This chapter describes some useful memory pools provided in the GNAT library
19443 and in particular the GNAT Debug Pool facility, which can be used to detect
19444 incorrect uses of access values (including ``dangling references'').
19446 It also describes the @command{gnatmem} tool, which can be used to track down
19451 * Some Useful Memory Pools::
19452 * The GNAT Debug Pool Facility::
19454 * The gnatmem Tool::
19458 @node Some Useful Memory Pools
19459 @section Some Useful Memory Pools
19460 @findex Memory Pool
19461 @cindex storage, pool
19464 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19465 storage pool. Allocations use the standard system call @code{malloc} while
19466 deallocations use the standard system call @code{free}. No reclamation is
19467 performed when the pool goes out of scope. For performance reasons, the
19468 standard default Ada allocators/deallocators do not use any explicit storage
19469 pools but if they did, they could use this storage pool without any change in
19470 behavior. That is why this storage pool is used when the user
19471 manages to make the default implicit allocator explicit as in this example:
19472 @smallexample @c ada
19473 type T1 is access Something;
19474 -- no Storage pool is defined for T2
19475 type T2 is access Something_Else;
19476 for T2'Storage_Pool use T1'Storage_Pool;
19477 -- the above is equivalent to
19478 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19482 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19483 pool. The allocation strategy is similar to @code{Pool_Local}'s
19484 except that the all
19485 storage allocated with this pool is reclaimed when the pool object goes out of
19486 scope. This pool provides a explicit mechanism similar to the implicit one
19487 provided by several Ada 83 compilers for allocations performed through a local
19488 access type and whose purpose was to reclaim memory when exiting the
19489 scope of a given local access. As an example, the following program does not
19490 leak memory even though it does not perform explicit deallocation:
19492 @smallexample @c ada
19493 with System.Pool_Local;
19494 procedure Pooloc1 is
19495 procedure Internal is
19496 type A is access Integer;
19497 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19498 for A'Storage_Pool use X;
19501 for I in 1 .. 50 loop
19506 for I in 1 .. 100 loop
19513 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19514 @code{Storage_Size} is specified for an access type.
19515 The whole storage for the pool is
19516 allocated at once, usually on the stack at the point where the access type is
19517 elaborated. It is automatically reclaimed when exiting the scope where the
19518 access type is defined. This package is not intended to be used directly by the
19519 user and it is implicitly used for each such declaration:
19521 @smallexample @c ada
19522 type T1 is access Something;
19523 for T1'Storage_Size use 10_000;
19526 @node The GNAT Debug Pool Facility
19527 @section The GNAT Debug Pool Facility
19529 @cindex storage, pool, memory corruption
19532 The use of unchecked deallocation and unchecked conversion can easily
19533 lead to incorrect memory references. The problems generated by such
19534 references are usually difficult to tackle because the symptoms can be
19535 very remote from the origin of the problem. In such cases, it is
19536 very helpful to detect the problem as early as possible. This is the
19537 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19539 In order to use the GNAT specific debugging pool, the user must
19540 associate a debug pool object with each of the access types that may be
19541 related to suspected memory problems. See Ada Reference Manual 13.11.
19542 @smallexample @c ada
19543 type Ptr is access Some_Type;
19544 Pool : GNAT.Debug_Pools.Debug_Pool;
19545 for Ptr'Storage_Pool use Pool;
19549 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19550 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19551 allow the user to redefine allocation and deallocation strategies. They
19552 also provide a checkpoint for each dereference, through the use of
19553 the primitive operation @code{Dereference} which is implicitly called at
19554 each dereference of an access value.
19556 Once an access type has been associated with a debug pool, operations on
19557 values of the type may raise four distinct exceptions,
19558 which correspond to four potential kinds of memory corruption:
19561 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19563 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19565 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19567 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19571 For types associated with a Debug_Pool, dynamic allocation is performed using
19572 the standard GNAT allocation routine. References to all allocated chunks of
19573 memory are kept in an internal dictionary. Several deallocation strategies are
19574 provided, whereupon the user can choose to release the memory to the system,
19575 keep it allocated for further invalid access checks, or fill it with an easily
19576 recognizable pattern for debug sessions. The memory pattern is the old IBM
19577 hexadecimal convention: @code{16#DEADBEEF#}.
19579 See the documentation in the file g-debpoo.ads for more information on the
19580 various strategies.
19582 Upon each dereference, a check is made that the access value denotes a
19583 properly allocated memory location. Here is a complete example of use of
19584 @code{Debug_Pools}, that includes typical instances of memory corruption:
19585 @smallexample @c ada
19589 with Gnat.Io; use Gnat.Io;
19590 with Unchecked_Deallocation;
19591 with Unchecked_Conversion;
19592 with GNAT.Debug_Pools;
19593 with System.Storage_Elements;
19594 with Ada.Exceptions; use Ada.Exceptions;
19595 procedure Debug_Pool_Test is
19597 type T is access Integer;
19598 type U is access all T;
19600 P : GNAT.Debug_Pools.Debug_Pool;
19601 for T'Storage_Pool use P;
19603 procedure Free is new Unchecked_Deallocation (Integer, T);
19604 function UC is new Unchecked_Conversion (U, T);
19607 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19617 Put_Line (Integer'Image(B.all));
19619 when E : others => Put_Line ("raised: " & Exception_Name (E));
19624 when E : others => Put_Line ("raised: " & Exception_Name (E));
19628 Put_Line (Integer'Image(B.all));
19630 when E : others => Put_Line ("raised: " & Exception_Name (E));
19635 when E : others => Put_Line ("raised: " & Exception_Name (E));
19638 end Debug_Pool_Test;
19642 The debug pool mechanism provides the following precise diagnostics on the
19643 execution of this erroneous program:
19646 Total allocated bytes : 0
19647 Total deallocated bytes : 0
19648 Current Water Mark: 0
19652 Total allocated bytes : 8
19653 Total deallocated bytes : 0
19654 Current Water Mark: 8
19657 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
19658 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
19659 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
19660 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
19662 Total allocated bytes : 8
19663 Total deallocated bytes : 4
19664 Current Water Mark: 4
19669 @node The gnatmem Tool
19670 @section The @command{gnatmem} Tool
19674 The @code{gnatmem} utility monitors dynamic allocation and
19675 deallocation activity in a program, and displays information about
19676 incorrect deallocations and possible sources of memory leaks.
19677 It provides three type of information:
19680 General information concerning memory management, such as the total
19681 number of allocations and deallocations, the amount of allocated
19682 memory and the high water mark, i.e.@: the largest amount of allocated
19683 memory in the course of program execution.
19686 Backtraces for all incorrect deallocations, that is to say deallocations
19687 which do not correspond to a valid allocation.
19690 Information on each allocation that is potentially the origin of a memory
19695 * Running gnatmem::
19696 * Switches for gnatmem::
19697 * Example of gnatmem Usage::
19700 @node Running gnatmem
19701 @subsection Running @code{gnatmem}
19704 @code{gnatmem} makes use of the output created by the special version of
19705 allocation and deallocation routines that record call information. This
19706 allows to obtain accurate dynamic memory usage history at a minimal cost to
19707 the execution speed. Note however, that @code{gnatmem} is not supported on
19708 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
19709 Solaris and Windows NT/2000/XP (x86).
19712 The @code{gnatmem} command has the form
19715 $ gnatmem @ovar{switches} user_program
19719 The program must have been linked with the instrumented version of the
19720 allocation and deallocation routines. This is done by linking with the
19721 @file{libgmem.a} library. For correct symbolic backtrace information,
19722 the user program should be compiled with debugging options
19723 (see @ref{Switches for gcc}). For example to build @file{my_program}:
19726 $ gnatmake -g my_program -largs -lgmem
19730 As library @file{libgmem.a} contains an alternate body for package
19731 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
19732 when an executable is linked with library @file{libgmem.a}. It is then not
19733 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
19736 When @file{my_program} is executed, the file @file{gmem.out} is produced.
19737 This file contains information about all allocations and deallocations
19738 performed by the program. It is produced by the instrumented allocations and
19739 deallocations routines and will be used by @code{gnatmem}.
19741 In order to produce symbolic backtrace information for allocations and
19742 deallocations performed by the GNAT run-time library, you need to use a
19743 version of that library that has been compiled with the @option{-g} switch
19744 (see @ref{Rebuilding the GNAT Run-Time Library}).
19746 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
19747 examine. If the location of @file{gmem.out} file was not explicitly supplied by
19748 @option{-i} switch, gnatmem will assume that this file can be found in the
19749 current directory. For example, after you have executed @file{my_program},
19750 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
19753 $ gnatmem my_program
19757 This will produce the output with the following format:
19759 *************** debut cc
19761 $ gnatmem my_program
19765 Total number of allocations : 45
19766 Total number of deallocations : 6
19767 Final Water Mark (non freed mem) : 11.29 Kilobytes
19768 High Water Mark : 11.40 Kilobytes
19773 Allocation Root # 2
19774 -------------------
19775 Number of non freed allocations : 11
19776 Final Water Mark (non freed mem) : 1.16 Kilobytes
19777 High Water Mark : 1.27 Kilobytes
19779 my_program.adb:23 my_program.alloc
19785 The first block of output gives general information. In this case, the
19786 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
19787 Unchecked_Deallocation routine occurred.
19790 Subsequent paragraphs display information on all allocation roots.
19791 An allocation root is a specific point in the execution of the program
19792 that generates some dynamic allocation, such as a ``@code{@b{new}}''
19793 construct. This root is represented by an execution backtrace (or subprogram
19794 call stack). By default the backtrace depth for allocations roots is 1, so
19795 that a root corresponds exactly to a source location. The backtrace can
19796 be made deeper, to make the root more specific.
19798 @node Switches for gnatmem
19799 @subsection Switches for @code{gnatmem}
19802 @code{gnatmem} recognizes the following switches:
19807 @cindex @option{-q} (@code{gnatmem})
19808 Quiet. Gives the minimum output needed to identify the origin of the
19809 memory leaks. Omits statistical information.
19812 @cindex @var{N} (@code{gnatmem})
19813 N is an integer literal (usually between 1 and 10) which controls the
19814 depth of the backtraces defining allocation root. The default value for
19815 N is 1. The deeper the backtrace, the more precise the localization of
19816 the root. Note that the total number of roots can depend on this
19817 parameter. This parameter must be specified @emph{before} the name of the
19818 executable to be analyzed, to avoid ambiguity.
19821 @cindex @option{-b} (@code{gnatmem})
19822 This switch has the same effect as just depth parameter.
19824 @item -i @var{file}
19825 @cindex @option{-i} (@code{gnatmem})
19826 Do the @code{gnatmem} processing starting from @file{file}, rather than
19827 @file{gmem.out} in the current directory.
19830 @cindex @option{-m} (@code{gnatmem})
19831 This switch causes @code{gnatmem} to mask the allocation roots that have less
19832 than n leaks. The default value is 1. Specifying the value of 0 will allow to
19833 examine even the roots that didn't result in leaks.
19836 @cindex @option{-s} (@code{gnatmem})
19837 This switch causes @code{gnatmem} to sort the allocation roots according to the
19838 specified order of sort criteria, each identified by a single letter. The
19839 currently supported criteria are @code{n, h, w} standing respectively for
19840 number of unfreed allocations, high watermark, and final watermark
19841 corresponding to a specific root. The default order is @code{nwh}.
19845 @node Example of gnatmem Usage
19846 @subsection Example of @code{gnatmem} Usage
19849 The following example shows the use of @code{gnatmem}
19850 on a simple memory-leaking program.
19851 Suppose that we have the following Ada program:
19853 @smallexample @c ada
19856 with Unchecked_Deallocation;
19857 procedure Test_Gm is
19859 type T is array (1..1000) of Integer;
19860 type Ptr is access T;
19861 procedure Free is new Unchecked_Deallocation (T, Ptr);
19864 procedure My_Alloc is
19869 procedure My_DeAlloc is
19877 for I in 1 .. 5 loop
19878 for J in I .. 5 loop
19889 The program needs to be compiled with debugging option and linked with
19890 @code{gmem} library:
19893 $ gnatmake -g test_gm -largs -lgmem
19897 Then we execute the program as usual:
19904 Then @code{gnatmem} is invoked simply with
19910 which produces the following output (result may vary on different platforms):
19915 Total number of allocations : 18
19916 Total number of deallocations : 5
19917 Final Water Mark (non freed mem) : 53.00 Kilobytes
19918 High Water Mark : 56.90 Kilobytes
19920 Allocation Root # 1
19921 -------------------
19922 Number of non freed allocations : 11
19923 Final Water Mark (non freed mem) : 42.97 Kilobytes
19924 High Water Mark : 46.88 Kilobytes
19926 test_gm.adb:11 test_gm.my_alloc
19928 Allocation Root # 2
19929 -------------------
19930 Number of non freed allocations : 1
19931 Final Water Mark (non freed mem) : 10.02 Kilobytes
19932 High Water Mark : 10.02 Kilobytes
19934 s-secsta.adb:81 system.secondary_stack.ss_init
19936 Allocation Root # 3
19937 -------------------
19938 Number of non freed allocations : 1
19939 Final Water Mark (non freed mem) : 12 Bytes
19940 High Water Mark : 12 Bytes
19942 s-secsta.adb:181 system.secondary_stack.ss_init
19946 Note that the GNAT run time contains itself a certain number of
19947 allocations that have no corresponding deallocation,
19948 as shown here for root #2 and root
19949 #3. This is a normal behavior when the number of non-freed allocations
19950 is one, it allocates dynamic data structures that the run time needs for
19951 the complete lifetime of the program. Note also that there is only one
19952 allocation root in the user program with a single line back trace:
19953 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
19954 program shows that 'My_Alloc' is called at 2 different points in the
19955 source (line 21 and line 24). If those two allocation roots need to be
19956 distinguished, the backtrace depth parameter can be used:
19959 $ gnatmem 3 test_gm
19963 which will give the following output:
19968 Total number of allocations : 18
19969 Total number of deallocations : 5
19970 Final Water Mark (non freed mem) : 53.00 Kilobytes
19971 High Water Mark : 56.90 Kilobytes
19973 Allocation Root # 1
19974 -------------------
19975 Number of non freed allocations : 10
19976 Final Water Mark (non freed mem) : 39.06 Kilobytes
19977 High Water Mark : 42.97 Kilobytes
19979 test_gm.adb:11 test_gm.my_alloc
19980 test_gm.adb:24 test_gm
19981 b_test_gm.c:52 main
19983 Allocation Root # 2
19984 -------------------
19985 Number of non freed allocations : 1
19986 Final Water Mark (non freed mem) : 10.02 Kilobytes
19987 High Water Mark : 10.02 Kilobytes
19989 s-secsta.adb:81 system.secondary_stack.ss_init
19990 s-secsta.adb:283 <system__secondary_stack___elabb>
19991 b_test_gm.c:33 adainit
19993 Allocation Root # 3
19994 -------------------
19995 Number of non freed allocations : 1
19996 Final Water Mark (non freed mem) : 3.91 Kilobytes
19997 High Water Mark : 3.91 Kilobytes
19999 test_gm.adb:11 test_gm.my_alloc
20000 test_gm.adb:21 test_gm
20001 b_test_gm.c:52 main
20003 Allocation Root # 4
20004 -------------------
20005 Number of non freed allocations : 1
20006 Final Water Mark (non freed mem) : 12 Bytes
20007 High Water Mark : 12 Bytes
20009 s-secsta.adb:181 system.secondary_stack.ss_init
20010 s-secsta.adb:283 <system__secondary_stack___elabb>
20011 b_test_gm.c:33 adainit
20015 The allocation root #1 of the first example has been split in 2 roots #1
20016 and #3 thanks to the more precise associated backtrace.
20020 @node Stack Related Facilities
20021 @chapter Stack Related Facilities
20024 This chapter describes some useful tools associated with stack
20025 checking and analysis. In
20026 particular, it deals with dynamic and static stack usage measurements.
20029 * Stack Overflow Checking::
20030 * Static Stack Usage Analysis::
20031 * Dynamic Stack Usage Analysis::
20034 @node Stack Overflow Checking
20035 @section Stack Overflow Checking
20036 @cindex Stack Overflow Checking
20037 @cindex -fstack-check
20040 For most operating systems, @command{gcc} does not perform stack overflow
20041 checking by default. This means that if the main environment task or
20042 some other task exceeds the available stack space, then unpredictable
20043 behavior will occur. Most native systems offer some level of protection by
20044 adding a guard page at the end of each task stack. This mechanism is usually
20045 not enough for dealing properly with stack overflow situations because
20046 a large local variable could ``jump'' above the guard page.
20047 Furthermore, when the
20048 guard page is hit, there may not be any space left on the stack for executing
20049 the exception propagation code. Enabling stack checking avoids
20052 To activate stack checking, compile all units with the gcc option
20053 @option{-fstack-check}. For example:
20056 gcc -c -fstack-check package1.adb
20060 Units compiled with this option will generate extra instructions to check
20061 that any use of the stack (for procedure calls or for declaring local
20062 variables in declare blocks) does not exceed the available stack space.
20063 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20065 For declared tasks, the stack size is controlled by the size
20066 given in an applicable @code{Storage_Size} pragma or by the value specified
20067 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20068 the default size as defined in the GNAT runtime otherwise.
20070 For the environment task, the stack size depends on
20071 system defaults and is unknown to the compiler. Stack checking
20072 may still work correctly if a fixed
20073 size stack is allocated, but this cannot be guaranteed.
20075 To ensure that a clean exception is signalled for stack
20076 overflow, set the environment variable
20077 @env{GNAT_STACK_LIMIT} to indicate the maximum
20078 stack area that can be used, as in:
20079 @cindex GNAT_STACK_LIMIT
20082 SET GNAT_STACK_LIMIT 1600
20086 The limit is given in kilobytes, so the above declaration would
20087 set the stack limit of the environment task to 1.6 megabytes.
20088 Note that the only purpose of this usage is to limit the amount
20089 of stack used by the environment task. If it is necessary to
20090 increase the amount of stack for the environment task, then this
20091 is an operating systems issue, and must be addressed with the
20092 appropriate operating systems commands.
20095 To have a fixed size stack in the environment task, the stack must be put
20096 in the P0 address space and its size specified. Use these switches to
20100 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20104 The quotes are required to keep case. The number after @samp{STACK=} is the
20105 size of the environmental task stack in pagelets (512 bytes). In this example
20106 the stack size is about 2 megabytes.
20109 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20110 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20111 more details about the @option{/p0image} qualifier and the @option{stack}
20115 @node Static Stack Usage Analysis
20116 @section Static Stack Usage Analysis
20117 @cindex Static Stack Usage Analysis
20118 @cindex -fstack-usage
20121 A unit compiled with @option{-fstack-usage} will generate an extra file
20123 the maximum amount of stack used, on a per-function basis.
20124 The file has the same
20125 basename as the target object file with a @file{.su} extension.
20126 Each line of this file is made up of three fields:
20130 The name of the function.
20134 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20137 The second field corresponds to the size of the known part of the function
20140 The qualifier @code{static} means that the function frame size
20142 It usually means that all local variables have a static size.
20143 In this case, the second field is a reliable measure of the function stack
20146 The qualifier @code{dynamic} means that the function frame size is not static.
20147 It happens mainly when some local variables have a dynamic size. When this
20148 qualifier appears alone, the second field is not a reliable measure
20149 of the function stack analysis. When it is qualified with @code{bounded}, it
20150 means that the second field is a reliable maximum of the function stack
20153 @node Dynamic Stack Usage Analysis
20154 @section Dynamic Stack Usage Analysis
20157 It is possible to measure the maximum amount of stack used by a task, by
20158 adding a switch to @command{gnatbind}, as:
20161 $ gnatbind -u0 file
20165 With this option, at each task termination, its stack usage is output on
20167 It is not always convenient to output the stack usage when the program
20168 is still running. Hence, it is possible to delay this output until program
20169 termination. for a given number of tasks specified as the argument of the
20170 @option{-u} option. For instance:
20173 $ gnatbind -u100 file
20177 will buffer the stack usage information of the first 100 tasks to terminate and
20178 output this info at program termination. Results are displayed in four
20182 Index | Task Name | Stack Size | Actual Use [min - max]
20189 is a number associated with each task.
20192 is the name of the task analyzed.
20195 is the maximum size for the stack.
20198 is the measure done by the stack analyzer. In order to prevent overflow,
20199 the stack is not entirely analyzed, and it's not possible to know exactly how
20200 much has actually been used. The real amount of stack used is between the min
20206 The environment task stack, e.g., the stack that contains the main unit, is
20207 only processed when the environment variable GNAT_STACK_LIMIT is set.
20210 @c *********************************
20212 @c *********************************
20213 @node Verifying Properties Using gnatcheck
20214 @chapter Verifying Properties Using @command{gnatcheck}
20216 @cindex @command{gnatcheck}
20219 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20220 of Ada source files according to a given set of semantic rules.
20223 In order to check compliance with a given rule, @command{gnatcheck} has to
20224 semantically analyze the Ada sources.
20225 Therefore, checks can only be performed on
20226 legal Ada units. Moreover, when a unit depends semantically upon units located
20227 outside the current directory, the source search path has to be provided when
20228 calling @command{gnatcheck}, either through a specified project file or
20229 through @command{gnatcheck} switches as described below.
20231 A number of rules are predefined in @command{gnatcheck} and are described
20232 later in this chapter.
20233 You can also add new rules, by modifying the @command{gnatcheck} code and
20234 rebuilding the tool. In order to add a simple rule making some local checks,
20235 a small amount of straightforward ASIS-based programming is usually needed.
20237 Project support for @command{gnatcheck} is provided by the GNAT
20238 driver (see @ref{The GNAT Driver and Project Files}).
20240 Invoking @command{gnatcheck} on the command line has the form:
20243 $ gnatcheck @ovar{switches} @{@var{filename}@}
20244 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20245 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20252 @var{switches} specify the general tool options
20255 Each @var{filename} is the name (including the extension) of a source
20256 file to process. ``Wildcards'' are allowed, and
20257 the file name may contain path information.
20260 Each @var{arg_list_filename} is the name (including the extension) of a text
20261 file containing the names of the source files to process, separated by spaces
20265 @var{gcc_switches} is a list of switches for
20266 @command{gcc}. They will be passed on to all compiler invocations made by
20267 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20268 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20269 and use the @option{-gnatec} switch to set the configuration file.
20272 @var{rule_options} is a list of options for controlling a set of
20273 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20277 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20280 * Format of the Report File::
20281 * General gnatcheck Switches::
20282 * gnatcheck Rule Options::
20283 * Adding the Results of Compiler Checks to gnatcheck Output::
20284 * Project-Wide Checks::
20285 * Predefined Rules::
20288 @node Format of the Report File
20289 @section Format of the Report File
20290 @cindex Report file (for @code{gnatcheck})
20293 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20295 It also creates, in the current
20296 directory, a text file named @file{^gnatcheck.out^GNATCHECK.OUT^} that
20297 contains the complete report of the last gnatcheck run. This report contains:
20299 @item a list of the Ada source files being checked,
20300 @item a list of enabled and disabled rules,
20301 @item a list of the diagnostic messages, ordered in three different ways
20302 and collected in three separate
20303 sections. Section 1 contains the raw list of diagnostic messages. It
20304 corresponds to the output going to @file{stdout}. Section 2 contains
20305 messages ordered by rules.
20306 Section 3 contains messages ordered by source files.
20309 @node General gnatcheck Switches
20310 @section General @command{gnatcheck} Switches
20313 The following switches control the general @command{gnatcheck} behavior
20317 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20319 Process all units including those with read-only ALI files such as
20320 those from GNAT Run-Time library.
20324 @cindex @option{-d} (@command{gnatcheck})
20329 @cindex @option{-dd} (@command{gnatcheck})
20331 Progress indicator mode (for use in GPS)
20334 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20336 List the predefined and user-defined rules. For more details see
20337 @ref{Predefined Rules}.
20339 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20341 Use full source locations references in the report file. For a construct from
20342 a generic instantiation a full source location is a chain from the location
20343 of this construct in the generic unit to the place where this unit is
20346 @cindex @option{^-m^/DIAGNOSIS_LIMIT^} (@command{gnatcheck})
20347 @item ^-m@i{nnn}^/DIAGNOSIS_LIMIT=@i{nnn}^
20348 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20349 the default value is 500. Zero means that there is no limitation on
20350 the number of diagnostic messages to be printed into Stdout.
20352 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20354 Quiet mode. All the diagnoses about rule violations are placed in the
20355 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20357 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20359 Short format of the report file (no version information, no list of applied
20360 rules, no list of checked sources is included)
20362 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20363 @item ^-s1^/COMPILER_STYLE^
20364 Include the compiler-style section in the report file
20366 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20367 @item ^-s2^/BY_RULES^
20368 Include the section containing diagnoses ordered by rules in the report file
20370 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20371 @item ^-s3^/BY_FILES_BY_RULES^
20372 Include the section containing diagnoses ordered by files and then by rules
20375 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20376 @item ^-v^/VERBOSE^
20377 Verbose mode; @command{gnatcheck} generates version information and then
20378 a trace of sources being processed.
20383 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20384 @option{^-s2^/BY_RULES^} or
20385 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20386 then the @command{gnatcheck} report file will only contain sections
20387 explicitly denoted by these options.
20389 @node gnatcheck Rule Options
20390 @section @command{gnatcheck} Rule Options
20393 The following options control the processing performed by
20394 @command{gnatcheck}.
20397 @cindex @option{+ALL} (@command{gnatcheck})
20399 Turn all the rule checks ON.
20401 @cindex @option{-ALL} (@command{gnatcheck})
20403 Turn all the rule checks OFF.
20405 @cindex @option{+R} (@command{gnatcheck})
20406 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20407 Turn on the check for a specified rule with the specified parameter, if any.
20408 @var{rule_id} must be the identifier of one of the currently implemented rules
20409 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20410 are not case-sensitive. The @var{param} item must
20411 be a string representing a valid parameter(s) for the specified rule.
20412 If it contains any space characters then this string must be enclosed in
20415 @cindex @option{-R} (@command{gnatcheck})
20416 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20417 Turn off the check for a specified rule with the specified parameter, if any.
20419 @cindex @option{-from} (@command{gnatcheck})
20420 @item -from=@var{rule_option_filename}
20421 Read the rule options from the text file @var{rule_option_filename}, referred as
20422 ``rule file'' below.
20427 The default behavior is that all the rule checks are disabled.
20429 A rule file is a text file containing a set of rule options.
20430 @cindex Rule file (for @code{gnatcheck})
20431 The file may contain empty lines and Ada-style comments (comment
20432 lines and end-of-line comments). The rule file has free format; that is,
20433 you do not have to start a new rule option on a new line.
20435 A rule file may contain other @option{-from=@var{rule_option_filename}}
20436 options, each such option being replaced with the content of the
20437 corresponding rule file during the rule files processing. In case a
20438 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20439 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20440 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20441 the processing of rule files is interrupted and a part of their content
20445 @node Adding the Results of Compiler Checks to gnatcheck Output
20446 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20449 The @command{gnatcheck} tool can include in the generated diagnostic messages
20451 the report file the results of the checks performed by the compiler. Though
20452 disabled by default, this effect may be obtained by using @option{+R} with
20453 the following rule identifiers and parameters:
20457 To record restrictions violations (that are performed by the compiler if the
20458 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20460 @code{Restrictions} with the same parameters as pragma
20461 @code{Restrictions} or @code{Restriction_Warnings}.
20464 To record compiler style checks(@pxref{Style Checking}), use the rule named
20465 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20466 which enables all the standard style checks that corresponds to @option{-gnatyy}
20467 GNAT style check option, or a string that has exactly the same
20468 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20469 @code{Style_Checks} (for further information about this pragma,
20470 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}).
20473 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20474 named @code{Warnings} with a parameter that is a valid
20475 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20476 (for further information about this pragma, @pxref{Pragma Warnings,,,
20477 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20478 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20479 all the specific warnings, but not suppresses the warning mode,
20480 and 'e' parameter, corresponding to @option{-gnatwe} that means
20481 "treat warnings as errors", does not have any effect.
20485 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20486 option with the corresponding restriction name as a parameter. @code{-R} is
20487 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20488 warnings and style checks, use the corresponding warning and style options.
20490 @node Project-Wide Checks
20491 @section Project-Wide Checks
20492 @cindex Project-wide checks (for @command{gnatcheck})
20495 In order to perform checks on all units of a given project, you can use
20496 the GNAT driver along with the @option{-P} option:
20498 gnat check -Pproj -rules -from=my_rules
20502 If the project @code{proj} depends upon other projects, you can perform
20503 checks on the project closure using the @option{-U} option:
20505 gnat check -Pproj -U -rules -from=my_rules
20509 Finally, if not all the units are relevant to a particular main
20510 program in the project closure, you can perform checks for the set
20511 of units needed to create a given main program (unit closure) using
20512 the @option{-U} option followed by the name of the main unit:
20514 gnat check -Pproj -U main -rules -from=my_rules
20518 @node Predefined Rules
20519 @section Predefined Rules
20520 @cindex Predefined rules (for @command{gnatcheck})
20523 @c (Jan 2007) Since the global rules are still under development and are not
20524 @c documented, there is no point in explaining the difference between
20525 @c global and local rules
20527 A rule in @command{gnatcheck} is either local or global.
20528 A @emph{local rule} is a rule that applies to a well-defined section
20529 of a program and that can be checked by analyzing only this section.
20530 A @emph{global rule} requires analysis of some global properties of the
20531 whole program (mostly related to the program call graph).
20532 As of @value{NOW}, the implementation of global rules should be
20533 considered to be at a preliminary stage. You can use the
20534 @option{+GLOBAL} option to enable all the global rules, and the
20535 @option{-GLOBAL} rule option to disable all the global rules.
20537 All the global rules in the list below are
20538 so indicated by marking them ``GLOBAL''.
20539 This +GLOBAL and -GLOBAL options are not
20540 included in the list of gnatcheck options above, because at the moment they
20541 are considered as a temporary debug options.
20543 @command{gnatcheck} performs rule checks for generic
20544 instances only for global rules. This limitation may be relaxed in a later
20549 The following subsections document the rules implemented in
20550 @command{gnatcheck}.
20551 The subsection title is the same as the rule identifier, which may be
20552 used as a parameter of the @option{+R} or @option{-R} options.
20556 * Abstract_Type_Declarations::
20557 * Anonymous_Arrays::
20558 * Anonymous_Subtypes::
20560 * Boolean_Relational_Operators::
20562 * Ceiling_Violations::
20564 * Controlled_Type_Declarations::
20565 * Declarations_In_Blocks::
20566 * Default_Parameters::
20567 * Discriminated_Records::
20568 * Enumeration_Ranges_In_CASE_Statements::
20569 * Exceptions_As_Control_Flow::
20570 * EXIT_Statements_With_No_Loop_Name::
20571 * Expanded_Loop_Exit_Names::
20572 * Explicit_Full_Discrete_Ranges::
20573 * Float_Equality_Checks::
20574 * Forbidden_Pragmas::
20575 * Function_Style_Procedures::
20576 * Generics_In_Subprograms::
20577 * GOTO_Statements::
20578 * Implicit_IN_Mode_Parameters::
20579 * Implicit_SMALL_For_Fixed_Point_Types::
20580 * Improperly_Located_Instantiations::
20581 * Improper_Returns::
20582 * Library_Level_Subprograms::
20585 * Improperly_Called_Protected_Entries::
20588 * Misnamed_Identifiers::
20589 * Multiple_Entries_In_Protected_Definitions::
20591 * Non_Qualified_Aggregates::
20592 * Non_Short_Circuit_Operators::
20593 * Non_SPARK_Attributes::
20594 * Non_Tagged_Derived_Types::
20595 * Non_Visible_Exceptions::
20596 * Numeric_Literals::
20597 * OTHERS_In_Aggregates::
20598 * OTHERS_In_CASE_Statements::
20599 * OTHERS_In_Exception_Handlers::
20600 * Outer_Loop_Exits::
20601 * Overloaded_Operators::
20602 * Overly_Nested_Control_Structures::
20603 * Parameters_Out_Of_Order::
20604 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20605 * Positional_Actuals_For_Defaulted_Parameters::
20606 * Positional_Components::
20607 * Positional_Generic_Parameters::
20608 * Positional_Parameters::
20609 * Predefined_Numeric_Types::
20610 * Raising_External_Exceptions::
20611 * Raising_Predefined_Exceptions::
20612 * Separate_Numeric_Error_Handlers::
20615 * Side_Effect_Functions::
20618 * Unassigned_OUT_Parameters::
20619 * Uncommented_BEGIN_In_Package_Bodies::
20620 * Unconstrained_Array_Returns::
20621 * Universal_Ranges::
20622 * Unnamed_Blocks_And_Loops::
20624 * Unused_Subprograms::
20626 * USE_PACKAGE_Clauses::
20627 * Volatile_Objects_Without_Address_Clauses::
20631 @node Abstract_Type_Declarations
20632 @subsection @code{Abstract_Type_Declarations}
20633 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
20636 Flag all declarations of abstract types. For an abstract private
20637 type, both the private and full type declarations are flagged.
20639 This rule has no parameters.
20642 @node Anonymous_Arrays
20643 @subsection @code{Anonymous_Arrays}
20644 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
20647 Flag all anonymous array type definitions (by Ada semantics these can only
20648 occur in object declarations).
20650 This rule has no parameters.
20652 @node Anonymous_Subtypes
20653 @subsection @code{Anonymous_Subtypes}
20654 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
20657 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
20658 any instance of a subtype indication with a constraint, other than one
20659 that occurs immediately within a subtype declaration. Any use of a range
20660 other than as a constraint used immediately within a subtype declaration
20661 is considered as an anonymous subtype.
20663 An effect of this rule is that @code{for} loops such as the following are
20664 flagged (since @code{1..N} is formally a ``range''):
20666 @smallexample @c ada
20667 for I in 1 .. N loop
20673 Declaring an explicit subtype solves the problem:
20675 @smallexample @c ada
20676 subtype S is Integer range 1..N;
20684 This rule has no parameters.
20687 @subsection @code{Blocks}
20688 @cindex @code{Blocks} rule (for @command{gnatcheck})
20691 Flag each block statement.
20693 This rule has no parameters.
20695 @node Boolean_Relational_Operators
20696 @subsection @code{Boolean_Relational_Operators}
20697 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
20700 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
20701 ``>='', ``='' and ``/='') for the predefined Boolean type.
20702 (This rule is useful in enforcing the SPARK language restrictions.)
20704 Calls to predefined relational operators of any type derived from
20705 @code{Standard.Boolean} are not detected. Calls to user-defined functions
20706 with these designators, and uses of operators that are renamings
20707 of the predefined relational operators for @code{Standard.Boolean},
20708 are likewise not detected.
20710 This rule has no parameters.
20713 @node Ceiling_Violations
20714 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
20715 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
20718 Flag invocations of a protected operation by a task whose priority exceeds
20719 the protected object's ceiling.
20721 As of @value{NOW}, this rule has the following limitations:
20726 We consider only pragmas Priority and Interrupt_Priority as means to define
20727 a task/protected operation priority. We do not consider the effect of using
20728 Ada.Dynamic_Priorities.Set_Priority procedure;
20731 We consider only base task priorities, and no priority inheritance. That is,
20732 we do not make a difference between calls issued during task activation and
20733 execution of the sequence of statements from task body;
20736 Any situation when the priority of protected operation caller is set by a
20737 dynamic expression (that is, the corresponding Priority or
20738 Interrupt_Priority pragma has a non-static expression as an argument) we
20739 treat as a priority inconsistency (and, therefore, detect this situation).
20743 At the moment the notion of the main subprogram is not implemented in
20744 gnatcheck, so any pragma Priority in a library level subprogram body (in case
20745 if this subprogram can be a main subprogram of a partition) changes the
20746 priority of an environment task. So if we have more then one such pragma in
20747 the set of processed sources, the pragma that is processed last, defines the
20748 priority of an environment task.
20750 This rule has no parameters.
20753 @node Controlled_Type_Declarations
20754 @subsection @code{Controlled_Type_Declarations}
20755 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
20758 Flag all declarations of controlled types. A declaration of a private type
20759 is flagged if its full declaration declares a controlled type. A declaration
20760 of a derived type is flagged if its ancestor type is controlled. Subtype
20761 declarations are not checked. A declaration of a type that itself is not a
20762 descendant of a type declared in @code{Ada.Finalization} but has a controlled
20763 component is not checked.
20765 This rule has no parameters.
20769 @node Declarations_In_Blocks
20770 @subsection @code{Declarations_In_Blocks}
20771 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
20774 Flag all block statements containing local declarations. A @code{declare}
20775 block with an empty @i{declarative_part} or with a @i{declarative part}
20776 containing only pragmas and/or @code{use} clauses is not flagged.
20778 This rule has no parameters.
20781 @node Default_Parameters
20782 @subsection @code{Default_Parameters}
20783 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
20786 Flag all default expressions for subprogram parameters. Parameter
20787 declarations of formal and generic subprograms are also checked.
20789 This rule has no parameters.
20792 @node Discriminated_Records
20793 @subsection @code{Discriminated_Records}
20794 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
20797 Flag all declarations of record types with discriminants. Only the
20798 declarations of record and record extension types are checked. Incomplete,
20799 formal, private, derived and private extension type declarations are not
20800 checked. Task and protected type declarations also are not checked.
20802 This rule has no parameters.
20805 @node Enumeration_Ranges_In_CASE_Statements
20806 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
20807 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
20810 Flag each use of a range of enumeration literals as a choice in a
20811 @code{case} statement.
20812 All forms for specifying a range (explicit ranges
20813 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
20814 An enumeration range is
20815 flagged even if contains exactly one enumeration value or no values at all. A
20816 type derived from an enumeration type is considered as an enumeration type.
20818 This rule helps prevent maintenance problems arising from adding an
20819 enumeration value to a type and having it implicitly handled by an existing
20820 @code{case} statement with an enumeration range that includes the new literal.
20822 This rule has no parameters.
20825 @node Exceptions_As_Control_Flow
20826 @subsection @code{Exceptions_As_Control_Flow}
20827 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
20830 Flag each place where an exception is explicitly raised and handled in the
20831 same subprogram body. A @code{raise} statement in an exception handler,
20832 package body, task body or entry body is not flagged.
20834 The rule has no parameters.
20836 @node EXIT_Statements_With_No_Loop_Name
20837 @subsection @code{EXIT_Statements_With_No_Loop_Name}
20838 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
20841 Flag each @code{exit} statement that does not specify the name of the loop
20844 The rule has no parameters.
20847 @node Expanded_Loop_Exit_Names
20848 @subsection @code{Expanded_Loop_Exit_Names}
20849 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
20852 Flag all expanded loop names in @code{exit} statements.
20854 This rule has no parameters.
20856 @node Explicit_Full_Discrete_Ranges
20857 @subsection @code{Explicit_Full_Discrete_Ranges}
20858 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
20861 Flag each discrete range that has the form @code{A'First .. A'Last}.
20863 This rule has no parameters.
20865 @node Float_Equality_Checks
20866 @subsection @code{Float_Equality_Checks}
20867 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
20870 Flag all calls to the predefined equality operations for floating-point types.
20871 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
20872 User-defined equality operations are not flagged, nor are ``@code{=}''
20873 and ``@code{/=}'' operations for fixed-point types.
20875 This rule has no parameters.
20878 @node Forbidden_Pragmas
20879 @subsection @code{Forbidden_Pragmas}
20880 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
20883 Flag each use of the specified pragmas. The pragmas to be detected
20884 are named in the rule's parameters.
20886 This rule has the following parameters:
20889 @item For the @option{+R} option
20892 @item @emph{Pragma_Name}
20893 Adds the specified pragma to the set of pragmas to be
20894 checked and sets the checks for all the specified pragmas
20895 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
20896 does not correspond to any pragma name defined in the Ada
20897 standard or to the name of a GNAT-specific pragma defined
20898 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20899 Manual}, it is treated as the name of unknown pragma.
20902 All the GNAT-specific pragmas are detected; this sets
20903 the checks for all the specified pragmas ON.
20906 All pragmas are detected; this sets the rule ON.
20909 @item For the @option{-R} option
20911 @item @emph{Pragma_Name}
20912 Removes the specified pragma from the set of pragmas to be
20913 checked without affecting checks for
20914 other pragmas. @emph{Pragma_Name} is treated as a name
20915 of a pragma. If it does not correspond to any pragma
20916 defined in the Ada standard or to any name defined in
20917 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
20918 this option is treated as turning OFF detection of all unknown pragmas.
20921 Turn OFF detection of all GNAT-specific pragmas
20924 Clear the list of the pragmas to be detected and
20930 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
20931 the syntax of an Ada identifier and therefore can not be considered
20932 as a pragma name, a diagnostic message is generated and the corresponding
20933 parameter is ignored.
20935 When more then one parameter is given in the same rule option, the parameters
20936 must be separated by a comma.
20938 If more then one option for this rule is specified for the @command{gnatcheck}
20939 call, a new option overrides the previous one(s).
20941 The @option{+R} option with no parameters turns the rule ON with the set of
20942 pragmas to be detected defined by the previous rule options.
20943 (By default this set is empty, so if the only option specified for the rule is
20944 @option{+RForbidden_Pragmas} (with
20945 no parameter), then the rule is enabled, but it does not detect anything).
20946 The @option{-R} option with no parameter turns the rule OFF, but it does not
20947 affect the set of pragmas to be detected.
20952 @node Function_Style_Procedures
20953 @subsection @code{Function_Style_Procedures}
20954 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
20957 Flag each procedure that can be rewritten as a function. A procedure can be
20958 converted into a function if it has exactly one parameter of mode @code{out}
20959 and no parameters of mode @code{in out}. Procedure declarations,
20960 formal procedure declarations, and generic procedure declarations are always
20962 bodies and body stubs are flagged only if they do not have corresponding
20963 separate declarations. Procedure renamings and procedure instantiations are
20966 If a procedure can be rewritten as a function, but its @code{out} parameter is
20967 of a limited type, it is not flagged.
20969 Protected procedures are not flagged. Null procedures also are not flagged.
20971 This rule has no parameters.
20974 @node Generics_In_Subprograms
20975 @subsection @code{Generics_In_Subprograms}
20976 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
20979 Flag each declaration of a generic unit in a subprogram. Generic
20980 declarations in the bodies of generic subprograms are also flagged.
20981 A generic unit nested in another generic unit is not flagged.
20982 If a generic unit is
20983 declared in a local package that is declared in a subprogram body, the
20984 generic unit is flagged.
20986 This rule has no parameters.
20989 @node GOTO_Statements
20990 @subsection @code{GOTO_Statements}
20991 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
20994 Flag each occurrence of a @code{goto} statement.
20996 This rule has no parameters.
20999 @node Implicit_IN_Mode_Parameters
21000 @subsection @code{Implicit_IN_Mode_Parameters}
21001 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21004 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21005 Note that @code{access} parameters, although they technically behave
21006 like @code{in} parameters, are not flagged.
21008 This rule has no parameters.
21011 @node Implicit_SMALL_For_Fixed_Point_Types
21012 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21013 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21016 Flag each fixed point type declaration that lacks an explicit
21017 representation clause to define its @code{'Small} value.
21018 Since @code{'Small} can be defined only for ordinary fixed point types,
21019 decimal fixed point type declarations are not checked.
21021 This rule has no parameters.
21024 @node Improperly_Located_Instantiations
21025 @subsection @code{Improperly_Located_Instantiations}
21026 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21029 Flag all generic instantiations in library-level package specs
21030 (including library generic packages) and in all subprogram bodies.
21032 Instantiations in task and entry bodies are not flagged. Instantiations in the
21033 bodies of protected subprograms are flagged.
21035 This rule has no parameters.
21039 @node Improper_Returns
21040 @subsection @code{Improper_Returns}
21041 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21044 Flag each explicit @code{return} statement in procedures, and
21045 multiple @code{return} statements in functions.
21046 Diagnostic messages are generated for all @code{return} statements
21047 in a procedure (thus each procedure must be written so that it
21048 returns implicitly at the end of its statement part),
21049 and for all @code{return} statements in a function after the first one.
21050 This rule supports the stylistic convention that each subprogram
21051 should have no more than one point of normal return.
21053 This rule has no parameters.
21056 @node Library_Level_Subprograms
21057 @subsection @code{Library_Level_Subprograms}
21058 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21061 Flag all library-level subprograms (including generic subprogram instantiations).
21063 This rule has no parameters.
21066 @node Local_Packages
21067 @subsection @code{Local_Packages}
21068 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21071 Flag all local packages declared in package and generic package
21073 Local packages in bodies are not flagged.
21075 This rule has no parameters.
21078 @node Improperly_Called_Protected_Entries
21079 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21080 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21083 Flag each protected entry that can be called from more than one task.
21085 This rule has no parameters.
21089 @subsection @code{Metrics}
21090 @cindex @code{Metrics} rule (for @command{gnatcheck})
21093 There is a set of checks based on computing a metric value and comparing the
21094 result with the specified upper (or lower, depending on a specific metric)
21095 value specified for a given metric. A construct is flagged if a given metric
21096 is applicable (can be computed) for it and the computed value is greater
21097 then (lover then) the specified upper (lower) bound.
21099 The name of any metric-based rule consists of the prefix @code{Metrics_}
21100 followed by the name of the corresponding metric (see the table below).
21101 For @option{+R} option, each metric-based rule has a numeric parameter
21102 specifying the bound (integer or real, depending on a metric), @option{-R}
21103 option for metric rules does not have a parameter.
21105 The following table shows the metric names for that the corresponding
21106 metrics-based checks are supported by gnatcheck, including the
21107 constraint that must be satisfied by the bound that is specified for the check
21108 and what bound - upper (U) or lower (L) - should be specified.
21110 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21112 @headitem Check Name @tab Description @tab Bounds Value
21115 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21117 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21118 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21119 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21120 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21124 The meaning and the computed values for all these metrics are exactly
21125 the same as for the corresponding metrics in @command{gnatmetric}.
21127 @emph{Example:} the rule
21129 +RMetrics_Cyclomatic_Complexity : 7
21132 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21134 To turn OFF the check for cyclomatic complexity metric, use the following option:
21136 -RMetrics_Cyclomatic_Complexity
21139 @node Misnamed_Identifiers
21140 @subsection @code{Misnamed_Identifiers}
21141 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21144 Flag the declaration of each identifier that does not have a suffix
21145 corresponding to the kind of entity being declared.
21146 The following declarations are checked:
21153 constant declarations (but not number declarations)
21156 package renaming declarations (but not generic package renaming
21161 This rule may have parameters. When used without parameters, the rule enforces
21162 the following checks:
21166 type-defining names end with @code{_T}, unless the type is an access type,
21167 in which case the suffix must be @code{_A}
21169 constant names end with @code{_C}
21171 names defining package renamings end with @code{_R}
21175 For a private or incomplete type declaration the following checks are
21176 made for the defining name suffix:
21180 For an incomplete type declaration: if the corresponding full type
21181 declaration is available, the defining identifier from the full type
21182 declaration is checked, but the defining identifier from the incomplete type
21183 declaration is not; otherwise the defining identifier from the incomplete
21184 type declaration is checked against the suffix specified for type
21188 For a private type declaration (including private extensions), the defining
21189 identifier from the private type declaration is checked against the type
21190 suffix (even if the corresponding full declaration is an access type
21191 declaration), and the defining identifier from the corresponding full type
21192 declaration is not checked.
21196 For a deferred constant, the defining name in the corresponding full constant
21197 declaration is not checked.
21199 Defining names of formal types are not checked.
21201 The rule may have the following parameters:
21205 For the @option{+R} option:
21208 Sets the default listed above for all the names to be checked.
21210 @item Type_Suffix=@emph{string}
21211 Specifies the suffix for a type name.
21213 @item Access_Suffix=@emph{string}
21214 Specifies the suffix for an access type name. If
21215 this parameter is set, it overrides for access
21216 types the suffix set by the @code{Type_Suffix} parameter.
21218 @item Constant_Suffix=@emph{string}
21219 Specifies the suffix for a constant name.
21221 @item Renaming_Suffix=@emph{string}
21222 Specifies the suffix for a package renaming name.
21226 For the @option{-R} option:
21229 Remove all the suffixes specified for the
21230 identifier suffix checks, whether by default or
21231 as specified by other rule parameters. All the
21232 checks for this rule are disabled as a result.
21235 Removes the suffix specified for types. This
21236 disables checks for types but does not disable
21237 any other checks for this rule (including the
21238 check for access type names if @code{Access_Suffix} is
21241 @item Access_Suffix
21242 Removes the suffix specified for access types.
21243 This disables checks for access type names but
21244 does not disable any other checks for this rule.
21245 If @code{Type_Suffix} is set, access type names are
21246 checked as ordinary type names.
21248 @item Constant_Suffix
21249 Removes the suffix specified for constants. This
21250 disables checks for constant names but does not
21251 disable any other checks for this rule.
21253 @item Renaming_Suffix
21254 Removes the suffix specified for package
21255 renamings. This disables checks for package
21256 renamings but does not disable any other checks
21262 If more than one parameter is used, parameters must be separated by commas.
21264 If more than one option is specified for the @command{gnatcheck} invocation,
21265 a new option overrides the previous one(s).
21267 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21269 name suffixes specified by previous options used for this rule.
21271 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21272 all the checks but keeps
21273 all the suffixes specified by previous options used for this rule.
21275 The @emph{string} value must be a valid suffix for an Ada identifier (after
21276 trimming all the leading and trailing space characters, if any).
21277 Parameters are not case sensitive, except the @emph{string} part.
21279 If any error is detected in a rule parameter, the parameter is ignored.
21280 In such a case the options that are set for the rule are not
21285 @node Multiple_Entries_In_Protected_Definitions
21286 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21287 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21290 Flag each protected definition (i.e., each protected object/type declaration)
21291 that defines more than one entry.
21292 Diagnostic messages are generated for all the entry declarations
21293 except the first one. An entry family is counted as one entry. Entries from
21294 the private part of the protected definition are also checked.
21296 This rule has no parameters.
21299 @subsection @code{Name_Clashes}
21300 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21303 Check that certain names are not used as defining identifiers. To activate
21304 this rule, you need to supply a reference to the dictionary file(s) as a rule
21305 parameter(s) (more then one dictionary file can be specified). If no
21306 dictionary file is set, this rule will not cause anything to be flagged.
21307 Only defining occurrences, not references, are checked.
21308 The check is not case-sensitive.
21310 This rule is enabled by default, but without setting any corresponding
21311 dictionary file(s); thus the default effect is to do no checks.
21313 A dictionary file is a plain text file. The maximum line length for this file
21314 is 1024 characters. If the line is longer then this limit, extra characters
21317 Each line can be either an empty line, a comment line, or a line containing
21318 a list of identifiers separated by space or HT characters.
21319 A comment is an Ada-style comment (from @code{--} to end-of-line).
21320 Identifiers must follow the Ada syntax for identifiers.
21321 A line containing one or more identifiers may end with a comment.
21323 @node Non_Qualified_Aggregates
21324 @subsection @code{Non_Qualified_Aggregates}
21325 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21328 Flag each non-qualified aggregate.
21329 A non-qualified aggregate is an
21330 aggregate that is not the expression of a qualified expression. A
21331 string literal is not considered an aggregate, but an array
21332 aggregate of a string type is considered as a normal aggregate.
21333 Aggregates of anonymous array types are not flagged.
21335 This rule has no parameters.
21338 @node Non_Short_Circuit_Operators
21339 @subsection @code{Non_Short_Circuit_Operators}
21340 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21343 Flag all calls to predefined @code{and} and @code{or} operators for
21344 any boolean type. Calls to
21345 user-defined @code{and} and @code{or} and to operators defined by renaming
21346 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21347 operators for modular types or boolean array types are not flagged.
21349 This rule has no parameters.
21353 @node Non_SPARK_Attributes
21354 @subsection @code{Non_SPARK_Attributes}
21355 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21358 The SPARK language defines the following subset of Ada 95 attribute
21359 designators as those that can be used in SPARK programs. The use of
21360 any other attribute is flagged.
21363 @item @code{'Adjacent}
21366 @item @code{'Ceiling}
21367 @item @code{'Component_Size}
21368 @item @code{'Compose}
21369 @item @code{'Copy_Sign}
21370 @item @code{'Delta}
21371 @item @code{'Denorm}
21372 @item @code{'Digits}
21373 @item @code{'Exponent}
21374 @item @code{'First}
21375 @item @code{'Floor}
21377 @item @code{'Fraction}
21379 @item @code{'Leading_Part}
21380 @item @code{'Length}
21381 @item @code{'Machine}
21382 @item @code{'Machine_Emax}
21383 @item @code{'Machine_Emin}
21384 @item @code{'Machine_Mantissa}
21385 @item @code{'Machine_Overflows}
21386 @item @code{'Machine_Radix}
21387 @item @code{'Machine_Rounds}
21390 @item @code{'Model}
21391 @item @code{'Model_Emin}
21392 @item @code{'Model_Epsilon}
21393 @item @code{'Model_Mantissa}
21394 @item @code{'Model_Small}
21395 @item @code{'Modulus}
21398 @item @code{'Range}
21399 @item @code{'Remainder}
21400 @item @code{'Rounding}
21401 @item @code{'Safe_First}
21402 @item @code{'Safe_Last}
21403 @item @code{'Scaling}
21404 @item @code{'Signed_Zeros}
21406 @item @code{'Small}
21408 @item @code{'Truncation}
21409 @item @code{'Unbiased_Rounding}
21411 @item @code{'Valid}
21415 This rule has no parameters.
21418 @node Non_Tagged_Derived_Types
21419 @subsection @code{Non_Tagged_Derived_Types}
21420 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21423 Flag all derived type declarations that do not have a record extension part.
21425 This rule has no parameters.
21429 @node Non_Visible_Exceptions
21430 @subsection @code{Non_Visible_Exceptions}
21431 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21434 Flag constructs leading to the possibility of propagating an exception
21435 out of the scope in which the exception is declared.
21436 Two cases are detected:
21440 An exception declaration in a subprogram body, task body or block
21441 statement is flagged if the body or statement does not contain a handler for
21442 that exception or a handler with an @code{others} choice.
21445 A @code{raise} statement in an exception handler of a subprogram body,
21446 task body or block statement is flagged if it (re)raises a locally
21447 declared exception. This may occur under the following circumstances:
21450 it explicitly raises a locally declared exception, or
21452 it does not specify an exception name (i.e., it is simply @code{raise;})
21453 and the enclosing handler contains a locally declared exception in its
21459 Renamings of local exceptions are not flagged.
21461 This rule has no parameters.
21464 @node Numeric_Literals
21465 @subsection @code{Numeric_Literals}
21466 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21469 Flag each use of a numeric literal in an index expression, and in any
21470 circumstance except for the following:
21474 a literal occurring in the initialization expression for a constant
21475 declaration or a named number declaration, or
21478 an integer literal that is less than or equal to a value
21479 specified by the @option{N} rule parameter.
21483 This rule may have the following parameters for the @option{+R} option:
21487 @emph{N} is an integer literal used as the maximal value that is not flagged
21488 (i.e., integer literals not exceeding this value are allowed)
21491 All integer literals are flagged
21495 If no parameters are set, the maximum unflagged value is 1.
21497 The last specified check limit (or the fact that there is no limit at
21498 all) is used when multiple @option{+R} options appear.
21500 The @option{-R} option for this rule has no parameters.
21501 It disables the rule but retains the last specified maximum unflagged value.
21502 If the @option{+R} option subsequently appears, this value is used as the
21503 threshold for the check.
21506 @node OTHERS_In_Aggregates
21507 @subsection @code{OTHERS_In_Aggregates}
21508 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21511 Flag each use of an @code{others} choice in extension aggregates.
21512 In record and array aggregates, an @code{others} choice is flagged unless
21513 it is used to refer to all components, or to all but one component.
21515 If, in case of a named array aggregate, there are two associations, one
21516 with an @code{others} choice and another with a discrete range, the
21517 @code{others} choice is flagged even if the discrete range specifies
21518 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21520 This rule has no parameters.
21522 @node OTHERS_In_CASE_Statements
21523 @subsection @code{OTHERS_In_CASE_Statements}
21524 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21527 Flag any use of an @code{others} choice in a @code{case} statement.
21529 This rule has no parameters.
21531 @node OTHERS_In_Exception_Handlers
21532 @subsection @code{OTHERS_In_Exception_Handlers}
21533 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21536 Flag any use of an @code{others} choice in an exception handler.
21538 This rule has no parameters.
21541 @node Outer_Loop_Exits
21542 @subsection @code{Outer_Loop_Exits}
21543 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21546 Flag each @code{exit} statement containing a loop name that is not the name
21547 of the immediately enclosing @code{loop} statement.
21549 This rule has no parameters.
21552 @node Overloaded_Operators
21553 @subsection @code{Overloaded_Operators}
21554 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21557 Flag each function declaration that overloads an operator symbol.
21558 A function body is checked only if the body does not have a
21559 separate spec. Formal functions are also checked. For a
21560 renaming declaration, only renaming-as-declaration is checked
21562 This rule has no parameters.
21565 @node Overly_Nested_Control_Structures
21566 @subsection @code{Overly_Nested_Control_Structures}
21567 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21570 Flag each control structure whose nesting level exceeds the value provided
21571 in the rule parameter.
21573 The control structures checked are the following:
21576 @item @code{if} statement
21577 @item @code{case} statement
21578 @item @code{loop} statement
21579 @item Selective accept statement
21580 @item Timed entry call statement
21581 @item Conditional entry call
21582 @item Asynchronous select statement
21586 The rule has the following parameter for the @option{+R} option:
21590 Positive integer specifying the maximal control structure nesting
21591 level that is not flagged
21595 If the parameter for the @option{+R} option is not specified or
21596 if it is not a positive integer, @option{+R} option is ignored.
21598 If more then one option is specified for the gnatcheck call, the later option and
21599 new parameter override the previous one(s).
21602 @node Parameters_Out_Of_Order
21603 @subsection @code{Parameters_Out_Of_Order}
21604 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
21607 Flag each subprogram and entry declaration whose formal parameters are not
21608 ordered according to the following scheme:
21612 @item @code{in} and @code{access} parameters first,
21613 then @code{in out} parameters,
21614 and then @code{out} parameters;
21616 @item for @code{in} mode, parameters with default initialization expressions
21621 Only the first violation of the described order is flagged.
21623 The following constructs are checked:
21626 @item subprogram declarations (including null procedures);
21627 @item generic subprogram declarations;
21628 @item formal subprogram declarations;
21629 @item entry declarations;
21630 @item subprogram bodies and subprogram body stubs that do not
21631 have separate specifications
21635 Subprogram renamings are not checked.
21637 This rule has no parameters.
21640 @node Positional_Actuals_For_Defaulted_Generic_Parameters
21641 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
21642 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
21645 Flag each generic actual parameter corresponding to a generic formal
21646 parameter with a default initialization, if positional notation is used.
21648 This rule has no parameters.
21650 @node Positional_Actuals_For_Defaulted_Parameters
21651 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
21652 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
21655 Flag each actual parameter to a subprogram or entry call where the
21656 corresponding formal parameter has a default expression, if positional
21659 This rule has no parameters.
21661 @node Positional_Components
21662 @subsection @code{Positional_Components}
21663 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
21666 Flag each array, record and extension aggregate that includes positional
21669 This rule has no parameters.
21672 @node Positional_Generic_Parameters
21673 @subsection @code{Positional_Generic_Parameters}
21674 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
21677 Flag each instantiation using positional parameter notation.
21679 This rule has no parameters.
21682 @node Positional_Parameters
21683 @subsection @code{Positional_Parameters}
21684 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
21687 Flag each subprogram or entry call using positional parameter notation,
21688 except for the following:
21692 Invocations of prefix or infix operators are not flagged
21694 If the called subprogram or entry has only one formal parameter,
21695 the call is not flagged;
21697 If a subprogram call uses the @emph{Object.Operation} notation, then
21700 the first parameter (that is, @emph{Object}) is not flagged;
21702 if the called subprogram has only two parameters, the second parameter
21703 of the call is not flagged;
21708 This rule has no parameters.
21713 @node Predefined_Numeric_Types
21714 @subsection @code{Predefined_Numeric_Types}
21715 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
21718 Flag each explicit use of the name of any numeric type or subtype defined
21719 in package @code{Standard}.
21721 The rationale for this rule is to detect when the
21722 program may depend on platform-specific characteristics of the implementation
21723 of the predefined numeric types. Note that this rule is over-pessimistic;
21724 for example, a program that uses @code{String} indexing
21725 likely needs a variable of type @code{Integer}.
21726 Another example is the flagging of predefined numeric types with explicit
21729 @smallexample @c ada
21730 subtype My_Integer is Integer range Left .. Right;
21731 Vy_Var : My_Integer;
21735 This rule detects only numeric types and subtypes defined in
21736 @code{Standard}. The use of numeric types and subtypes defined in other
21737 predefined packages (such as @code{System.Any_Priority} or
21738 @code{Ada.Text_IO.Count}) is not flagged
21740 This rule has no parameters.
21744 @node Raising_External_Exceptions
21745 @subsection @code{Raising_External_Exceptions}
21746 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
21749 Flag any @code{raise} statement, in a program unit declared in a library
21750 package or in a generic library package, for an exception that is
21751 neither a predefined exception nor an exception that is also declared (or
21752 renamed) in the visible part of the package.
21754 This rule has no parameters.
21758 @node Raising_Predefined_Exceptions
21759 @subsection @code{Raising_Predefined_Exceptions}
21760 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
21763 Flag each @code{raise} statement that raises a predefined exception
21764 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
21765 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
21767 This rule has no parameters.
21769 @node Separate_Numeric_Error_Handlers
21770 @subsection @code{Separate_Numeric_Error_Handlers}
21771 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
21774 Flags each exception handler that contains a choice for
21775 the predefined @code{Constraint_Error} exception, but does not contain
21776 the choice for the predefined @code{Numeric_Error} exception, or
21777 that contains the choice for @code{Numeric_Error}, but does not contain the
21778 choice for @code{Constraint_Error}.
21780 This rule has no parameters.
21784 @subsection @code{Recursion} (under construction, GLOBAL)
21785 @cindex @code{Recursion} rule (for @command{gnatcheck})
21788 Flag recursive subprograms (cycles in the call graph). Declarations, and not
21789 calls, of recursive subprograms are detected.
21791 This rule has no parameters.
21795 @node Side_Effect_Functions
21796 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
21797 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
21800 Flag functions with side effects.
21802 We define a side effect as changing any data object that is not local for the
21803 body of this function.
21805 At the moment, we do NOT consider a side effect any input-output operations
21806 (changing a state or a content of any file).
21808 We do not consider protected functions for this rule (???)
21810 There are the following sources of side effect:
21813 @item Explicit (or direct) side-effect:
21817 direct assignment to a non-local variable;
21820 direct call to an entity that is known to change some data object that is
21821 not local for the body of this function (Note, that if F1 calls F2 and F2
21822 does have a side effect, this does not automatically mean that F1 also
21823 have a side effect, because it may be the case that F2 is declared in
21824 F1's body and it changes some data object that is global for F2, but
21828 @item Indirect side-effect:
21831 Subprogram calls implicitly issued by:
21834 computing initialization expressions from type declarations as a part
21835 of object elaboration or allocator evaluation;
21837 computing implicit parameters of subprogram or entry calls or generic
21842 activation of a task that change some non-local data object (directly or
21846 elaboration code of a package that is a result of a package instantiation;
21849 controlled objects;
21852 @item Situations when we can suspect a side-effect, but the full static check
21853 is either impossible or too hard:
21856 assignment to access variables or to the objects pointed by access
21860 call to a subprogram pointed by access-to-subprogram value
21868 This rule has no parameters.
21872 @subsection @code{Slices}
21873 @cindex @code{Slices} rule (for @command{gnatcheck})
21876 Flag all uses of array slicing
21878 This rule has no parameters.
21881 @node Unassigned_OUT_Parameters
21882 @subsection @code{Unassigned_OUT_Parameters}
21883 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
21886 Flags procedures' @code{out} parameters that are not assigned, and
21887 identifies the contexts in which the assignments are missing.
21889 An @code{out} parameter is flagged in the statements in the procedure
21890 body's handled sequence of statements (before the procedure body's
21891 @code{exception} part, if any) if this sequence of statements contains
21892 no assignments to the parameter.
21894 An @code{out} parameter is flagged in an exception handler in the exception
21895 part of the procedure body's handled sequence of statements if the handler
21896 contains no assignment to the parameter.
21898 Bodies of generic procedures are also considered.
21900 The following are treated as assignments to an @code{out} parameter:
21904 an assignment statement, with the parameter or some component as the target;
21907 passing the parameter (or one of its components) as an @code{out} or
21908 @code{in out} parameter.
21912 This rule does not have any parameters.
21916 @node Uncommented_BEGIN_In_Package_Bodies
21917 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
21918 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
21921 Flags each package body with declarations and a statement part that does not
21922 include a trailing comment on the line containing the @code{begin} keyword;
21923 this trailing comment needs to specify the package name and nothing else.
21924 The @code{begin} is not flagged if the package body does not
21925 contain any declarations.
21927 If the @code{begin} keyword is placed on the
21928 same line as the last declaration or the first statement, it is flagged
21929 independently of whether the line contains a trailing comment. The
21930 diagnostic message is attached to the line containing the first statement.
21932 This rule has no parameters.
21935 @node Unconstrained_Array_Returns
21936 @subsection @code{Unconstrained_Array_Returns}
21937 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
21940 Flag each function returning an unconstrained array. Function declarations,
21941 function bodies (and body stubs) having no separate specifications,
21942 and generic function instantiations are checked.
21943 Generic function declarations, function calls and function renamings are
21946 This rule has no parameters.
21948 @node Universal_Ranges
21949 @subsection @code{Universal_Ranges}
21950 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
21953 Flag discrete ranges that are a part of an index constraint, constrained
21954 array definition, or @code{for}-loop parameter specification, and whose bounds
21955 are both of type @i{universal_integer}. Ranges that have at least one
21956 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
21957 or an expression of non-universal type) are not flagged.
21959 This rule has no parameters.
21962 @node Unnamed_Blocks_And_Loops
21963 @subsection @code{Unnamed_Blocks_And_Loops}
21964 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
21967 Flag each unnamed block statement and loop statement.
21969 The rule has no parameters.
21974 @node Unused_Subprograms
21975 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
21976 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
21979 Flag all unused subprograms.
21981 This rule has no parameters.
21987 @node USE_PACKAGE_Clauses
21988 @subsection @code{USE_PACKAGE_Clauses}
21989 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
21992 Flag all @code{use} clauses for packages; @code{use type} clauses are
21995 This rule has no parameters.
21999 @node Volatile_Objects_Without_Address_Clauses
22000 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22001 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22004 Flag each volatile object that does not have an address clause.
22006 The following check is made: if the pragma @code{Volatile} is applied to a
22007 data object or to its type, then an address clause must
22008 be supplied for this object.
22010 This rule does not check the components of data objects,
22011 array components that are volatile as a result of the pragma
22012 @code{Volatile_Components}, or objects that are volatile because
22013 they are atomic as a result of pragmas @code{Atomic} or
22014 @code{Atomic_Components}.
22016 Only variable declarations, and not constant declarations, are checked.
22018 This rule has no parameters.
22021 @c *********************************
22022 @node Creating Sample Bodies Using gnatstub
22023 @chapter Creating Sample Bodies Using @command{gnatstub}
22027 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22028 for library unit declarations.
22030 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22031 driver (see @ref{The GNAT Driver and Project Files}).
22033 To create a body stub, @command{gnatstub} has to compile the library
22034 unit declaration. Therefore, bodies can be created only for legal
22035 library units. Moreover, if a library unit depends semantically upon
22036 units located outside the current directory, you have to provide
22037 the source search path when calling @command{gnatstub}, see the description
22038 of @command{gnatstub} switches below.
22041 * Running gnatstub::
22042 * Switches for gnatstub::
22045 @node Running gnatstub
22046 @section Running @command{gnatstub}
22049 @command{gnatstub} has the command-line interface of the form
22052 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22059 is the name of the source file that contains a library unit declaration
22060 for which a body must be created. The file name may contain the path
22062 The file name does not have to follow the GNAT file name conventions. If the
22064 does not follow GNAT file naming conventions, the name of the body file must
22066 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22067 If the file name follows the GNAT file naming
22068 conventions and the name of the body file is not provided,
22071 of the body file from the argument file name by replacing the @file{.ads}
22073 with the @file{.adb} suffix.
22076 indicates the directory in which the body stub is to be placed (the default
22081 is an optional sequence of switches as described in the next section
22084 @node Switches for gnatstub
22085 @section Switches for @command{gnatstub}
22091 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22092 If the destination directory already contains a file with the name of the
22094 for the argument spec file, replace it with the generated body stub.
22096 @item ^-hs^/HEADER=SPEC^
22097 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22098 Put the comment header (i.e., all the comments preceding the
22099 compilation unit) from the source of the library unit declaration
22100 into the body stub.
22102 @item ^-hg^/HEADER=GENERAL^
22103 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22104 Put a sample comment header into the body stub.
22106 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22107 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22108 Use the content of the file as the comment header for a generated body stub.
22112 @cindex @option{-IDIR} (@command{gnatstub})
22114 @cindex @option{-I-} (@command{gnatstub})
22117 @item /NOCURRENT_DIRECTORY
22118 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22120 ^These switches have ^This switch has^ the same meaning as in calls to
22122 ^They define ^It defines ^ the source search path in the call to
22123 @command{gcc} issued
22124 by @command{gnatstub} to compile an argument source file.
22126 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22127 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22128 This switch has the same meaning as in calls to @command{gcc}.
22129 It defines the additional configuration file to be passed to the call to
22130 @command{gcc} issued
22131 by @command{gnatstub} to compile an argument source file.
22133 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22134 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22135 (@var{n} is a non-negative integer). Set the maximum line length in the
22136 body stub to @var{n}; the default is 79. The maximum value that can be
22137 specified is 32767. Note that in the special case of configuration
22138 pragma files, the maximum is always 32767 regardless of whether or
22139 not this switch appears.
22141 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22142 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22143 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22144 the generated body sample to @var{n}.
22145 The default indentation is 3.
22147 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22148 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22149 Order local bodies alphabetically. (By default local bodies are ordered
22150 in the same way as the corresponding local specs in the argument spec file.)
22152 @item ^-i^/INDENTATION=^@var{n}
22153 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22154 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22156 @item ^-k^/TREE_FILE=SAVE^
22157 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22158 Do not remove the tree file (i.e., the snapshot of the compiler internal
22159 structures used by @command{gnatstub}) after creating the body stub.
22161 @item ^-l^/LINE_LENGTH=^@var{n}
22162 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22163 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22165 @item ^-o^/BODY=^@var{body-name}
22166 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22167 Body file name. This should be set if the argument file name does not
22169 the GNAT file naming
22170 conventions. If this switch is omitted the default name for the body will be
22172 from the argument file name according to the GNAT file naming conventions.
22175 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22176 Quiet mode: do not generate a confirmation when a body is
22177 successfully created, and do not generate a message when a body is not
22181 @item ^-r^/TREE_FILE=REUSE^
22182 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22183 Reuse the tree file (if it exists) instead of creating it. Instead of
22184 creating the tree file for the library unit declaration, @command{gnatstub}
22185 tries to find it in the current directory and use it for creating
22186 a body. If the tree file is not found, no body is created. This option
22187 also implies @option{^-k^/SAVE^}, whether or not
22188 the latter is set explicitly.
22190 @item ^-t^/TREE_FILE=OVERWRITE^
22191 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22192 Overwrite the existing tree file. If the current directory already
22193 contains the file which, according to the GNAT file naming rules should
22194 be considered as a tree file for the argument source file,
22196 will refuse to create the tree file needed to create a sample body
22197 unless this option is set.
22199 @item ^-v^/VERBOSE^
22200 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22201 Verbose mode: generate version information.
22205 @node Other Utility Programs
22206 @chapter Other Utility Programs
22209 This chapter discusses some other utility programs available in the Ada
22213 * Using Other Utility Programs with GNAT::
22214 * The External Symbol Naming Scheme of GNAT::
22215 * Converting Ada Files to html with gnathtml::
22216 * Installing gnathtml::
22223 @node Using Other Utility Programs with GNAT
22224 @section Using Other Utility Programs with GNAT
22227 The object files generated by GNAT are in standard system format and in
22228 particular the debugging information uses this format. This means
22229 programs generated by GNAT can be used with existing utilities that
22230 depend on these formats.
22233 In general, any utility program that works with C will also often work with
22234 Ada programs generated by GNAT. This includes software utilities such as
22235 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22239 @node The External Symbol Naming Scheme of GNAT
22240 @section The External Symbol Naming Scheme of GNAT
22243 In order to interpret the output from GNAT, when using tools that are
22244 originally intended for use with other languages, it is useful to
22245 understand the conventions used to generate link names from the Ada
22248 All link names are in all lowercase letters. With the exception of library
22249 procedure names, the mechanism used is simply to use the full expanded
22250 Ada name with dots replaced by double underscores. For example, suppose
22251 we have the following package spec:
22253 @smallexample @c ada
22264 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22265 the corresponding link name is @code{qrs__mn}.
22267 Of course if a @code{pragma Export} is used this may be overridden:
22269 @smallexample @c ada
22274 pragma Export (Var1, C, External_Name => "var1_name");
22276 pragma Export (Var2, C, Link_Name => "var2_link_name");
22283 In this case, the link name for @var{Var1} is whatever link name the
22284 C compiler would assign for the C function @var{var1_name}. This typically
22285 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22286 system conventions, but other possibilities exist. The link name for
22287 @var{Var2} is @var{var2_link_name}, and this is not operating system
22291 One exception occurs for library level procedures. A potential ambiguity
22292 arises between the required name @code{_main} for the C main program,
22293 and the name we would otherwise assign to an Ada library level procedure
22294 called @code{Main} (which might well not be the main program).
22296 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22297 names. So if we have a library level procedure such as
22299 @smallexample @c ada
22302 procedure Hello (S : String);
22308 the external name of this procedure will be @var{_ada_hello}.
22311 @node Converting Ada Files to html with gnathtml
22312 @section Converting Ada Files to HTML with @code{gnathtml}
22315 This @code{Perl} script allows Ada source files to be browsed using
22316 standard Web browsers. For installation procedure, see the section
22317 @xref{Installing gnathtml}.
22319 Ada reserved keywords are highlighted in a bold font and Ada comments in
22320 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22321 switch to suppress the generation of cross-referencing information, user
22322 defined variables and types will appear in a different color; you will
22323 be able to click on any identifier and go to its declaration.
22325 The command line is as follow:
22327 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
22331 You can pass it as many Ada files as you want. @code{gnathtml} will generate
22332 an html file for every ada file, and a global file called @file{index.htm}.
22333 This file is an index of every identifier defined in the files.
22335 The available ^switches^options^ are the following ones:
22339 @cindex @option{-83} (@code{gnathtml})
22340 Only the Ada 83 subset of keywords will be highlighted.
22342 @item -cc @var{color}
22343 @cindex @option{-cc} (@code{gnathtml})
22344 This option allows you to change the color used for comments. The default
22345 value is green. The color argument can be any name accepted by html.
22348 @cindex @option{-d} (@code{gnathtml})
22349 If the Ada files depend on some other files (for instance through
22350 @code{with} clauses, the latter files will also be converted to html.
22351 Only the files in the user project will be converted to html, not the files
22352 in the run-time library itself.
22355 @cindex @option{-D} (@code{gnathtml})
22356 This command is the same as @option{-d} above, but @command{gnathtml} will
22357 also look for files in the run-time library, and generate html files for them.
22359 @item -ext @var{extension}
22360 @cindex @option{-ext} (@code{gnathtml})
22361 This option allows you to change the extension of the generated HTML files.
22362 If you do not specify an extension, it will default to @file{htm}.
22365 @cindex @option{-f} (@code{gnathtml})
22366 By default, gnathtml will generate html links only for global entities
22367 ('with'ed units, global variables and types,@dots{}). If you specify
22368 @option{-f} on the command line, then links will be generated for local
22371 @item -l @var{number}
22372 @cindex @option{-l} (@code{gnathtml})
22373 If this ^switch^option^ is provided and @var{number} is not 0, then
22374 @code{gnathtml} will number the html files every @var{number} line.
22377 @cindex @option{-I} (@code{gnathtml})
22378 Specify a directory to search for library files (@file{.ALI} files) and
22379 source files. You can provide several -I switches on the command line,
22380 and the directories will be parsed in the order of the command line.
22383 @cindex @option{-o} (@code{gnathtml})
22384 Specify the output directory for html files. By default, gnathtml will
22385 saved the generated html files in a subdirectory named @file{html/}.
22387 @item -p @var{file}
22388 @cindex @option{-p} (@code{gnathtml})
22389 If you are using Emacs and the most recent Emacs Ada mode, which provides
22390 a full Integrated Development Environment for compiling, checking,
22391 running and debugging applications, you may use @file{.gpr} files
22392 to give the directories where Emacs can find sources and object files.
22394 Using this ^switch^option^, you can tell gnathtml to use these files.
22395 This allows you to get an html version of your application, even if it
22396 is spread over multiple directories.
22398 @item -sc @var{color}
22399 @cindex @option{-sc} (@code{gnathtml})
22400 This ^switch^option^ allows you to change the color used for symbol
22402 The default value is red. The color argument can be any name accepted by html.
22404 @item -t @var{file}
22405 @cindex @option{-t} (@code{gnathtml})
22406 This ^switch^option^ provides the name of a file. This file contains a list of
22407 file names to be converted, and the effect is exactly as though they had
22408 appeared explicitly on the command line. This
22409 is the recommended way to work around the command line length limit on some
22414 @node Installing gnathtml
22415 @section Installing @code{gnathtml}
22418 @code{Perl} needs to be installed on your machine to run this script.
22419 @code{Perl} is freely available for almost every architecture and
22420 Operating System via the Internet.
22422 On Unix systems, you may want to modify the first line of the script
22423 @code{gnathtml}, to explicitly tell the Operating system where Perl
22424 is. The syntax of this line is:
22426 #!full_path_name_to_perl
22430 Alternatively, you may run the script using the following command line:
22433 $ perl gnathtml.pl @ovar{switches} @var{files}
22442 The GNAT distribution provides an Ada 95 template for the HP Language
22443 Sensitive Editor (LSE), a component of DECset. In order to
22444 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
22451 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
22452 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
22453 the collection phase with the /DEBUG qualifier.
22456 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
22457 $ DEFINE LIB$DEBUG PCA$COLLECTOR
22458 $ RUN/DEBUG <PROGRAM_NAME>
22464 @c ******************************
22465 @node Code Coverage and Profiling
22466 @chapter Code Coverage and Profiling
22467 @cindex Code Coverage
22471 This chapter describes how to use @code{gcov} - coverage testing tool - and
22472 @code{gprof} - profiler tool - on your Ada programs.
22475 * Code Coverage of Ada Programs using gcov::
22476 * Profiling an Ada Program using gprof::
22479 @node Code Coverage of Ada Programs using gcov
22480 @section Code Coverage of Ada Programs using gcov
22482 @cindex -fprofile-arcs
22483 @cindex -ftest-coverage
22485 @cindex Code Coverage
22488 @code{gcov} is a test coverage program: it analyzes the execution of a given
22489 program on selected tests, to help you determine the portions of the program
22490 that are still untested.
22492 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
22493 User's Guide. You can refer to this documentation for a more complete
22496 This chapter provides a quick startup guide, and
22497 details some Gnat-specific features.
22500 * Quick startup guide::
22504 @node Quick startup guide
22505 @subsection Quick startup guide
22507 In order to perform coverage analysis of a program using @code{gcov}, 3
22512 Code instrumentation during the compilation process
22514 Execution of the instrumented program
22516 Execution of the @code{gcov} tool to generate the result.
22519 The code instrumentation needed by gcov is created at the object level:
22520 The source code is not modified in any way, because the instrumentation code is
22521 inserted by gcc during the compilation process. To compile your code with code
22522 coverage activated, you need to recompile your whole project using the
22524 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
22525 @code{-fprofile-arcs}.
22528 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
22529 -largs -fprofile-arcs
22532 This compilation process will create @file{.gcno} files together with
22533 the usual object files.
22535 Once the program is compiled with coverage instrumentation, you can
22536 run it as many times as needed - on portions of a test suite for
22537 example. The first execution will produce @file{.gcda} files at the
22538 same location as the @file{.gcno} files. The following executions
22539 will update those files, so that a cumulative result of the covered
22540 portions of the program is generated.
22542 Finally, you need to call the @code{gcov} tool. The different options of
22543 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
22545 This will create annotated source files with a @file{.gcov} extension:
22546 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
22548 @node Gnat specifics
22549 @subsection Gnat specifics
22551 Because Ada semantics, portions of the source code may be shared among
22552 several object files. This is the case for example when generics are
22553 involved, when inlining is active or when declarations generate initialisation
22554 calls. In order to take
22555 into account this shared code, you need to call @code{gcov} on all
22556 source files of the tested program at once.
22558 The list of source files might exceed the system's maximum command line
22559 length. In order to bypass this limitation, a new mechanism has been
22560 implemented in @code{gcov}: you can now list all your project's files into a
22561 text file, and provide this file to gcov as a parameter, preceded by a @@
22562 (e.g. @samp{gcov @@mysrclist.txt}).
22564 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
22565 not supported as there can be unresolved symbols during the final link.
22567 @node Profiling an Ada Program using gprof
22568 @section Profiling an Ada Program using gprof
22574 This section is not meant to be an exhaustive documentation of @code{gprof}.
22575 Full documentation for it can be found in the GNU Profiler User's Guide
22576 documentation that is part of this GNAT distribution.
22578 Profiling a program helps determine the parts of a program that are executed
22579 most often, and are therefore the most time-consuming.
22581 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
22582 better handle Ada programs and multitasking.
22583 It is currently supported on the following platforms
22588 solaris sparc/sparc64/x86
22594 In order to profile a program using @code{gprof}, 3 steps are needed:
22598 Code instrumentation, requiring a full recompilation of the project with the
22601 Execution of the program under the analysis conditions, i.e. with the desired
22604 Analysis of the results using the @code{gprof} tool.
22608 The following sections detail the different steps, and indicate how
22609 to interpret the results:
22611 * Compilation for profiling::
22612 * Program execution::
22614 * Interpretation of profiling results::
22617 @node Compilation for profiling
22618 @subsection Compilation for profiling
22622 In order to profile a program the first step is to tell the compiler
22623 to generate the necessary profiling information. The compiler switch to be used
22624 is @code{-pg}, which must be added to other compilation switches. This
22625 switch needs to be specified both during compilation and link stages, and can
22626 be specified once when using gnatmake:
22629 gnatmake -f -pg -P my_project
22633 Note that only the objects that were compiled with the @samp{-pg} switch will be
22634 profiled; if you need to profile your whole project, use the
22635 @samp{-f} gnatmake switch to force full recompilation.
22637 @node Program execution
22638 @subsection Program execution
22641 Once the program has been compiled for profiling, you can run it as usual.
22643 The only constraint imposed by profiling is that the program must terminate
22644 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
22647 Once the program completes execution, a data file called @file{gmon.out} is
22648 generated in the directory where the program was launched from. If this file
22649 already exists, it will be overwritten.
22651 @node Running gprof
22652 @subsection Running gprof
22655 The @code{gprof} tool is called as follow:
22658 gprof my_prog gmon.out
22669 The complete form of the gprof command line is the following:
22672 gprof [^switches^options^] [executable [data-file]]
22676 @code{gprof} supports numerous ^switch^options^. The order of these
22677 ^switch^options^ does not matter. The full list of options can be found in
22678 the GNU Profiler User's Guide documentation that comes with this documentation.
22680 The following is the subset of those switches that is most relevant:
22684 @item --demangle[=@var{style}]
22685 @itemx --no-demangle
22686 @cindex @option{--demangle} (@code{gprof})
22687 These options control whether symbol names should be demangled when
22688 printing output. The default is to demangle C++ symbols. The
22689 @code{--no-demangle} option may be used to turn off demangling. Different
22690 compilers have different mangling styles. The optional demangling style
22691 argument can be used to choose an appropriate demangling style for your
22692 compiler, in particular Ada symbols generated by GNAT can be demangled using
22693 @code{--demangle=gnat}.
22695 @item -e @var{function_name}
22696 @cindex @option{-e} (@code{gprof})
22697 The @samp{-e @var{function}} option tells @code{gprof} not to print
22698 information about the function @var{function_name} (and its
22699 children@dots{}) in the call graph. The function will still be listed
22700 as a child of any functions that call it, but its index number will be
22701 shown as @samp{[not printed]}. More than one @samp{-e} option may be
22702 given; only one @var{function_name} may be indicated with each @samp{-e}
22705 @item -E @var{function_name}
22706 @cindex @option{-E} (@code{gprof})
22707 The @code{-E @var{function}} option works like the @code{-e} option, but
22708 execution time spent in the function (and children who were not called from
22709 anywhere else), will not be used to compute the percentages-of-time for
22710 the call graph. More than one @samp{-E} option may be given; only one
22711 @var{function_name} may be indicated with each @samp{-E} option.
22713 @item -f @var{function_name}
22714 @cindex @option{-f} (@code{gprof})
22715 The @samp{-f @var{function}} option causes @code{gprof} to limit the
22716 call graph to the function @var{function_name} and its children (and
22717 their children@dots{}). More than one @samp{-f} option may be given;
22718 only one @var{function_name} may be indicated with each @samp{-f}
22721 @item -F @var{function_name}
22722 @cindex @option{-F} (@code{gprof})
22723 The @samp{-F @var{function}} option works like the @code{-f} option, but
22724 only time spent in the function and its children (and their
22725 children@dots{}) will be used to determine total-time and
22726 percentages-of-time for the call graph. More than one @samp{-F} option
22727 may be given; only one @var{function_name} may be indicated with each
22728 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
22732 @node Interpretation of profiling results
22733 @subsection Interpretation of profiling results
22737 The results of the profiling analysis are represented by two arrays: the
22738 'flat profile' and the 'call graph'. Full documentation of those outputs
22739 can be found in the GNU Profiler User's Guide.
22741 The flat profile shows the time spent in each function of the program, and how
22742 many time it has been called. This allows you to locate easily the most
22743 time-consuming functions.
22745 The call graph shows, for each subprogram, the subprograms that call it,
22746 and the subprograms that it calls. It also provides an estimate of the time
22747 spent in each of those callers/called subprograms.
22750 @c ******************************
22751 @node Running and Debugging Ada Programs
22752 @chapter Running and Debugging Ada Programs
22756 This chapter discusses how to debug Ada programs.
22758 It applies to GNAT on the Alpha OpenVMS platform;
22759 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
22760 since HP has implemented Ada support in the OpenVMS debugger on I64.
22763 An incorrect Ada program may be handled in three ways by the GNAT compiler:
22767 The illegality may be a violation of the static semantics of Ada. In
22768 that case GNAT diagnoses the constructs in the program that are illegal.
22769 It is then a straightforward matter for the user to modify those parts of
22773 The illegality may be a violation of the dynamic semantics of Ada. In
22774 that case the program compiles and executes, but may generate incorrect
22775 results, or may terminate abnormally with some exception.
22778 When presented with a program that contains convoluted errors, GNAT
22779 itself may terminate abnormally without providing full diagnostics on
22780 the incorrect user program.
22784 * The GNAT Debugger GDB::
22786 * Introduction to GDB Commands::
22787 * Using Ada Expressions::
22788 * Calling User-Defined Subprograms::
22789 * Using the Next Command in a Function::
22792 * Debugging Generic Units::
22793 * GNAT Abnormal Termination or Failure to Terminate::
22794 * Naming Conventions for GNAT Source Files::
22795 * Getting Internal Debugging Information::
22796 * Stack Traceback::
22802 @node The GNAT Debugger GDB
22803 @section The GNAT Debugger GDB
22806 @code{GDB} is a general purpose, platform-independent debugger that
22807 can be used to debug mixed-language programs compiled with @command{gcc},
22808 and in particular is capable of debugging Ada programs compiled with
22809 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
22810 complex Ada data structures.
22812 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
22814 located in the GNU:[DOCS] directory,
22816 for full details on the usage of @code{GDB}, including a section on
22817 its usage on programs. This manual should be consulted for full
22818 details. The section that follows is a brief introduction to the
22819 philosophy and use of @code{GDB}.
22821 When GNAT programs are compiled, the compiler optionally writes debugging
22822 information into the generated object file, including information on
22823 line numbers, and on declared types and variables. This information is
22824 separate from the generated code. It makes the object files considerably
22825 larger, but it does not add to the size of the actual executable that
22826 will be loaded into memory, and has no impact on run-time performance. The
22827 generation of debug information is triggered by the use of the
22828 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
22829 used to carry out the compilations. It is important to emphasize that
22830 the use of these options does not change the generated code.
22832 The debugging information is written in standard system formats that
22833 are used by many tools, including debuggers and profilers. The format
22834 of the information is typically designed to describe C types and
22835 semantics, but GNAT implements a translation scheme which allows full
22836 details about Ada types and variables to be encoded into these
22837 standard C formats. Details of this encoding scheme may be found in
22838 the file exp_dbug.ads in the GNAT source distribution. However, the
22839 details of this encoding are, in general, of no interest to a user,
22840 since @code{GDB} automatically performs the necessary decoding.
22842 When a program is bound and linked, the debugging information is
22843 collected from the object files, and stored in the executable image of
22844 the program. Again, this process significantly increases the size of
22845 the generated executable file, but it does not increase the size of
22846 the executable program itself. Furthermore, if this program is run in
22847 the normal manner, it runs exactly as if the debug information were
22848 not present, and takes no more actual memory.
22850 However, if the program is run under control of @code{GDB}, the
22851 debugger is activated. The image of the program is loaded, at which
22852 point it is ready to run. If a run command is given, then the program
22853 will run exactly as it would have if @code{GDB} were not present. This
22854 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
22855 entirely non-intrusive until a breakpoint is encountered. If no
22856 breakpoint is ever hit, the program will run exactly as it would if no
22857 debugger were present. When a breakpoint is hit, @code{GDB} accesses
22858 the debugging information and can respond to user commands to inspect
22859 variables, and more generally to report on the state of execution.
22863 @section Running GDB
22866 This section describes how to initiate the debugger.
22867 @c The above sentence is really just filler, but it was otherwise
22868 @c clumsy to get the first paragraph nonindented given the conditional
22869 @c nature of the description
22872 The debugger can be launched from a @code{GPS} menu or
22873 directly from the command line. The description below covers the latter use.
22874 All the commands shown can be used in the @code{GPS} debug console window,
22875 but there are usually more GUI-based ways to achieve the same effect.
22878 The command to run @code{GDB} is
22881 $ ^gdb program^GDB PROGRAM^
22885 where @code{^program^PROGRAM^} is the name of the executable file. This
22886 activates the debugger and results in a prompt for debugger commands.
22887 The simplest command is simply @code{run}, which causes the program to run
22888 exactly as if the debugger were not present. The following section
22889 describes some of the additional commands that can be given to @code{GDB}.
22891 @c *******************************
22892 @node Introduction to GDB Commands
22893 @section Introduction to GDB Commands
22896 @code{GDB} contains a large repertoire of commands. @xref{Top,,
22897 Debugging with GDB, gdb, Debugging with GDB},
22899 located in the GNU:[DOCS] directory,
22901 for extensive documentation on the use
22902 of these commands, together with examples of their use. Furthermore,
22903 the command @command{help} invoked from within GDB activates a simple help
22904 facility which summarizes the available commands and their options.
22905 In this section we summarize a few of the most commonly
22906 used commands to give an idea of what @code{GDB} is about. You should create
22907 a simple program with debugging information and experiment with the use of
22908 these @code{GDB} commands on the program as you read through the
22912 @item set args @var{arguments}
22913 The @var{arguments} list above is a list of arguments to be passed to
22914 the program on a subsequent run command, just as though the arguments
22915 had been entered on a normal invocation of the program. The @code{set args}
22916 command is not needed if the program does not require arguments.
22919 The @code{run} command causes execution of the program to start from
22920 the beginning. If the program is already running, that is to say if
22921 you are currently positioned at a breakpoint, then a prompt will ask
22922 for confirmation that you want to abandon the current execution and
22925 @item breakpoint @var{location}
22926 The breakpoint command sets a breakpoint, that is to say a point at which
22927 execution will halt and @code{GDB} will await further
22928 commands. @var{location} is
22929 either a line number within a file, given in the format @code{file:linenumber},
22930 or it is the name of a subprogram. If you request that a breakpoint be set on
22931 a subprogram that is overloaded, a prompt will ask you to specify on which of
22932 those subprograms you want to breakpoint. You can also
22933 specify that all of them should be breakpointed. If the program is run
22934 and execution encounters the breakpoint, then the program
22935 stops and @code{GDB} signals that the breakpoint was encountered by
22936 printing the line of code before which the program is halted.
22938 @item breakpoint exception @var{name}
22939 A special form of the breakpoint command which breakpoints whenever
22940 exception @var{name} is raised.
22941 If @var{name} is omitted,
22942 then a breakpoint will occur when any exception is raised.
22944 @item print @var{expression}
22945 This will print the value of the given expression. Most simple
22946 Ada expression formats are properly handled by @code{GDB}, so the expression
22947 can contain function calls, variables, operators, and attribute references.
22950 Continues execution following a breakpoint, until the next breakpoint or the
22951 termination of the program.
22954 Executes a single line after a breakpoint. If the next statement
22955 is a subprogram call, execution continues into (the first statement of)
22956 the called subprogram.
22959 Executes a single line. If this line is a subprogram call, executes and
22960 returns from the call.
22963 Lists a few lines around the current source location. In practice, it
22964 is usually more convenient to have a separate edit window open with the
22965 relevant source file displayed. Successive applications of this command
22966 print subsequent lines. The command can be given an argument which is a
22967 line number, in which case it displays a few lines around the specified one.
22970 Displays a backtrace of the call chain. This command is typically
22971 used after a breakpoint has occurred, to examine the sequence of calls that
22972 leads to the current breakpoint. The display includes one line for each
22973 activation record (frame) corresponding to an active subprogram.
22976 At a breakpoint, @code{GDB} can display the values of variables local
22977 to the current frame. The command @code{up} can be used to
22978 examine the contents of other active frames, by moving the focus up
22979 the stack, that is to say from callee to caller, one frame at a time.
22982 Moves the focus of @code{GDB} down from the frame currently being
22983 examined to the frame of its callee (the reverse of the previous command),
22985 @item frame @var{n}
22986 Inspect the frame with the given number. The value 0 denotes the frame
22987 of the current breakpoint, that is to say the top of the call stack.
22992 The above list is a very short introduction to the commands that
22993 @code{GDB} provides. Important additional capabilities, including conditional
22994 breakpoints, the ability to execute command sequences on a breakpoint,
22995 the ability to debug at the machine instruction level and many other
22996 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
22997 Debugging with GDB}. Note that most commands can be abbreviated
22998 (for example, c for continue, bt for backtrace).
23000 @node Using Ada Expressions
23001 @section Using Ada Expressions
23002 @cindex Ada expressions
23005 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23006 extensions. The philosophy behind the design of this subset is
23010 That @code{GDB} should provide basic literals and access to operations for
23011 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23012 leaving more sophisticated computations to subprograms written into the
23013 program (which therefore may be called from @code{GDB}).
23016 That type safety and strict adherence to Ada language restrictions
23017 are not particularly important to the @code{GDB} user.
23020 That brevity is important to the @code{GDB} user.
23024 Thus, for brevity, the debugger acts as if there were
23025 implicit @code{with} and @code{use} clauses in effect for all user-written
23026 packages, thus making it unnecessary to fully qualify most names with
23027 their packages, regardless of context. Where this causes ambiguity,
23028 @code{GDB} asks the user's intent.
23030 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23031 GDB, gdb, Debugging with GDB}.
23033 @node Calling User-Defined Subprograms
23034 @section Calling User-Defined Subprograms
23037 An important capability of @code{GDB} is the ability to call user-defined
23038 subprograms while debugging. This is achieved simply by entering
23039 a subprogram call statement in the form:
23042 call subprogram-name (parameters)
23046 The keyword @code{call} can be omitted in the normal case where the
23047 @code{subprogram-name} does not coincide with any of the predefined
23048 @code{GDB} commands.
23050 The effect is to invoke the given subprogram, passing it the
23051 list of parameters that is supplied. The parameters can be expressions and
23052 can include variables from the program being debugged. The
23053 subprogram must be defined
23054 at the library level within your program, and @code{GDB} will call the
23055 subprogram within the environment of your program execution (which
23056 means that the subprogram is free to access or even modify variables
23057 within your program).
23059 The most important use of this facility is in allowing the inclusion of
23060 debugging routines that are tailored to particular data structures
23061 in your program. Such debugging routines can be written to provide a suitably
23062 high-level description of an abstract type, rather than a low-level dump
23063 of its physical layout. After all, the standard
23064 @code{GDB print} command only knows the physical layout of your
23065 types, not their abstract meaning. Debugging routines can provide information
23066 at the desired semantic level and are thus enormously useful.
23068 For example, when debugging GNAT itself, it is crucial to have access to
23069 the contents of the tree nodes used to represent the program internally.
23070 But tree nodes are represented simply by an integer value (which in turn
23071 is an index into a table of nodes).
23072 Using the @code{print} command on a tree node would simply print this integer
23073 value, which is not very useful. But the PN routine (defined in file
23074 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23075 a useful high level representation of the tree node, which includes the
23076 syntactic category of the node, its position in the source, the integers
23077 that denote descendant nodes and parent node, as well as varied
23078 semantic information. To study this example in more detail, you might want to
23079 look at the body of the PN procedure in the stated file.
23081 @node Using the Next Command in a Function
23082 @section Using the Next Command in a Function
23085 When you use the @code{next} command in a function, the current source
23086 location will advance to the next statement as usual. A special case
23087 arises in the case of a @code{return} statement.
23089 Part of the code for a return statement is the ``epilog'' of the function.
23090 This is the code that returns to the caller. There is only one copy of
23091 this epilog code, and it is typically associated with the last return
23092 statement in the function if there is more than one return. In some
23093 implementations, this epilog is associated with the first statement
23096 The result is that if you use the @code{next} command from a return
23097 statement that is not the last return statement of the function you
23098 may see a strange apparent jump to the last return statement or to
23099 the start of the function. You should simply ignore this odd jump.
23100 The value returned is always that from the first return statement
23101 that was stepped through.
23103 @node Ada Exceptions
23104 @section Breaking on Ada Exceptions
23108 You can set breakpoints that trip when your program raises
23109 selected exceptions.
23112 @item break exception
23113 Set a breakpoint that trips whenever (any task in the) program raises
23116 @item break exception @var{name}
23117 Set a breakpoint that trips whenever (any task in the) program raises
23118 the exception @var{name}.
23120 @item break exception unhandled
23121 Set a breakpoint that trips whenever (any task in the) program raises an
23122 exception for which there is no handler.
23124 @item info exceptions
23125 @itemx info exceptions @var{regexp}
23126 The @code{info exceptions} command permits the user to examine all defined
23127 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23128 argument, prints out only those exceptions whose name matches @var{regexp}.
23136 @code{GDB} allows the following task-related commands:
23140 This command shows a list of current Ada tasks, as in the following example:
23147 ID TID P-ID Thread Pri State Name
23148 1 8088000 0 807e000 15 Child Activation Wait main_task
23149 2 80a4000 1 80ae000 15 Accept/Select Wait b
23150 3 809a800 1 80a4800 15 Child Activation Wait a
23151 * 4 80ae800 3 80b8000 15 Running c
23155 In this listing, the asterisk before the first task indicates it to be the
23156 currently running task. The first column lists the task ID that is used
23157 to refer to tasks in the following commands.
23159 @item break @var{linespec} task @var{taskid}
23160 @itemx break @var{linespec} task @var{taskid} if @dots{}
23161 @cindex Breakpoints and tasks
23162 These commands are like the @code{break @dots{} thread @dots{}}.
23163 @var{linespec} specifies source lines.
23165 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23166 to specify that you only want @code{GDB} to stop the program when a
23167 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23168 numeric task identifiers assigned by @code{GDB}, shown in the first
23169 column of the @samp{info tasks} display.
23171 If you do not specify @samp{task @var{taskid}} when you set a
23172 breakpoint, the breakpoint applies to @emph{all} tasks of your
23175 You can use the @code{task} qualifier on conditional breakpoints as
23176 well; in this case, place @samp{task @var{taskid}} before the
23177 breakpoint condition (before the @code{if}).
23179 @item task @var{taskno}
23180 @cindex Task switching
23182 This command allows to switch to the task referred by @var{taskno}. In
23183 particular, This allows to browse the backtrace of the specified
23184 task. It is advised to switch back to the original task before
23185 continuing execution otherwise the scheduling of the program may be
23190 For more detailed information on the tasking support,
23191 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23193 @node Debugging Generic Units
23194 @section Debugging Generic Units
23195 @cindex Debugging Generic Units
23199 GNAT always uses code expansion for generic instantiation. This means that
23200 each time an instantiation occurs, a complete copy of the original code is
23201 made, with appropriate substitutions of formals by actuals.
23203 It is not possible to refer to the original generic entities in
23204 @code{GDB}, but it is always possible to debug a particular instance of
23205 a generic, by using the appropriate expanded names. For example, if we have
23207 @smallexample @c ada
23212 generic package k is
23213 procedure kp (v1 : in out integer);
23217 procedure kp (v1 : in out integer) is
23223 package k1 is new k;
23224 package k2 is new k;
23226 var : integer := 1;
23239 Then to break on a call to procedure kp in the k2 instance, simply
23243 (gdb) break g.k2.kp
23247 When the breakpoint occurs, you can step through the code of the
23248 instance in the normal manner and examine the values of local variables, as for
23251 @node GNAT Abnormal Termination or Failure to Terminate
23252 @section GNAT Abnormal Termination or Failure to Terminate
23253 @cindex GNAT Abnormal Termination or Failure to Terminate
23256 When presented with programs that contain serious errors in syntax
23258 GNAT may on rare occasions experience problems in operation, such
23260 segmentation fault or illegal memory access, raising an internal
23261 exception, terminating abnormally, or failing to terminate at all.
23262 In such cases, you can activate
23263 various features of GNAT that can help you pinpoint the construct in your
23264 program that is the likely source of the problem.
23266 The following strategies are presented in increasing order of
23267 difficulty, corresponding to your experience in using GNAT and your
23268 familiarity with compiler internals.
23272 Run @command{gcc} with the @option{-gnatf}. This first
23273 switch causes all errors on a given line to be reported. In its absence,
23274 only the first error on a line is displayed.
23276 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23277 are encountered, rather than after compilation is terminated. If GNAT
23278 terminates prematurely or goes into an infinite loop, the last error
23279 message displayed may help to pinpoint the culprit.
23282 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23283 mode, @command{gcc} produces ongoing information about the progress of the
23284 compilation and provides the name of each procedure as code is
23285 generated. This switch allows you to find which Ada procedure was being
23286 compiled when it encountered a code generation problem.
23289 @cindex @option{-gnatdc} switch
23290 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23291 switch that does for the front-end what @option{^-v^VERBOSE^} does
23292 for the back end. The system prints the name of each unit,
23293 either a compilation unit or nested unit, as it is being analyzed.
23295 Finally, you can start
23296 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23297 front-end of GNAT, and can be run independently (normally it is just
23298 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23299 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23300 @code{where} command is the first line of attack; the variable
23301 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23302 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23303 which the execution stopped, and @code{input_file name} indicates the name of
23307 @node Naming Conventions for GNAT Source Files
23308 @section Naming Conventions for GNAT Source Files
23311 In order to examine the workings of the GNAT system, the following
23312 brief description of its organization may be helpful:
23316 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23319 All files prefixed with @file{^par^PAR^} are components of the parser. The
23320 numbers correspond to chapters of the Ada Reference Manual. For example,
23321 parsing of select statements can be found in @file{par-ch9.adb}.
23324 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23325 numbers correspond to chapters of the Ada standard. For example, all
23326 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23327 addition, some features of the language require sufficient special processing
23328 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
23329 dynamic dispatching, etc.
23332 All files prefixed with @file{^exp^EXP^} perform normalization and
23333 expansion of the intermediate representation (abstract syntax tree, or AST).
23334 these files use the same numbering scheme as the parser and semantics files.
23335 For example, the construction of record initialization procedures is done in
23336 @file{exp_ch3.adb}.
23339 The files prefixed with @file{^bind^BIND^} implement the binder, which
23340 verifies the consistency of the compilation, determines an order of
23341 elaboration, and generates the bind file.
23344 The files @file{atree.ads} and @file{atree.adb} detail the low-level
23345 data structures used by the front-end.
23348 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
23349 the abstract syntax tree as produced by the parser.
23352 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
23353 all entities, computed during semantic analysis.
23356 Library management issues are dealt with in files with prefix
23362 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
23363 defined in Annex A.
23368 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
23369 defined in Annex B.
23373 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
23374 both language-defined children and GNAT run-time routines.
23378 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
23379 general-purpose packages, fully documented in their specs. All
23380 the other @file{.c} files are modifications of common @command{gcc} files.
23383 @node Getting Internal Debugging Information
23384 @section Getting Internal Debugging Information
23387 Most compilers have internal debugging switches and modes. GNAT
23388 does also, except GNAT internal debugging switches and modes are not
23389 secret. A summary and full description of all the compiler and binder
23390 debug flags are in the file @file{debug.adb}. You must obtain the
23391 sources of the compiler to see the full detailed effects of these flags.
23393 The switches that print the source of the program (reconstructed from
23394 the internal tree) are of general interest for user programs, as are the
23396 the full internal tree, and the entity table (the symbol table
23397 information). The reconstructed source provides a readable version of the
23398 program after the front-end has completed analysis and expansion,
23399 and is useful when studying the performance of specific constructs.
23400 For example, constraint checks are indicated, complex aggregates
23401 are replaced with loops and assignments, and tasking primitives
23402 are replaced with run-time calls.
23404 @node Stack Traceback
23405 @section Stack Traceback
23407 @cindex stack traceback
23408 @cindex stack unwinding
23411 Traceback is a mechanism to display the sequence of subprogram calls that
23412 leads to a specified execution point in a program. Often (but not always)
23413 the execution point is an instruction at which an exception has been raised.
23414 This mechanism is also known as @i{stack unwinding} because it obtains
23415 its information by scanning the run-time stack and recovering the activation
23416 records of all active subprograms. Stack unwinding is one of the most
23417 important tools for program debugging.
23419 The first entry stored in traceback corresponds to the deepest calling level,
23420 that is to say the subprogram currently executing the instruction
23421 from which we want to obtain the traceback.
23423 Note that there is no runtime performance penalty when stack traceback
23424 is enabled, and no exception is raised during program execution.
23427 * Non-Symbolic Traceback::
23428 * Symbolic Traceback::
23431 @node Non-Symbolic Traceback
23432 @subsection Non-Symbolic Traceback
23433 @cindex traceback, non-symbolic
23436 Note: this feature is not supported on all platforms. See
23437 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
23441 * Tracebacks From an Unhandled Exception::
23442 * Tracebacks From Exception Occurrences (non-symbolic)::
23443 * Tracebacks From Anywhere in a Program (non-symbolic)::
23446 @node Tracebacks From an Unhandled Exception
23447 @subsubsection Tracebacks From an Unhandled Exception
23450 A runtime non-symbolic traceback is a list of addresses of call instructions.
23451 To enable this feature you must use the @option{-E}
23452 @code{gnatbind}'s option. With this option a stack traceback is stored as part
23453 of exception information. You can retrieve this information using the
23454 @code{addr2line} tool.
23456 Here is a simple example:
23458 @smallexample @c ada
23464 raise Constraint_Error;
23479 $ gnatmake stb -bargs -E
23482 Execution terminated by unhandled exception
23483 Exception name: CONSTRAINT_ERROR
23485 Call stack traceback locations:
23486 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23490 As we see the traceback lists a sequence of addresses for the unhandled
23491 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
23492 guess that this exception come from procedure P1. To translate these
23493 addresses into the source lines where the calls appear, the
23494 @code{addr2line} tool, described below, is invaluable. The use of this tool
23495 requires the program to be compiled with debug information.
23498 $ gnatmake -g stb -bargs -E
23501 Execution terminated by unhandled exception
23502 Exception name: CONSTRAINT_ERROR
23504 Call stack traceback locations:
23505 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
23507 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
23508 0x4011f1 0x77e892a4
23510 00401373 at d:/stb/stb.adb:5
23511 0040138B at d:/stb/stb.adb:10
23512 0040139C at d:/stb/stb.adb:14
23513 00401335 at d:/stb/b~stb.adb:104
23514 004011C4 at /build/@dots{}/crt1.c:200
23515 004011F1 at /build/@dots{}/crt1.c:222
23516 77E892A4 in ?? at ??:0
23520 The @code{addr2line} tool has several other useful options:
23524 to get the function name corresponding to any location
23526 @item --demangle=gnat
23527 to use the gnat decoding mode for the function names. Note that
23528 for binutils version 2.9.x the option is simply @option{--demangle}.
23532 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
23533 0x40139c 0x401335 0x4011c4 0x4011f1
23535 00401373 in stb.p1 at d:/stb/stb.adb:5
23536 0040138B in stb.p2 at d:/stb/stb.adb:10
23537 0040139C in stb at d:/stb/stb.adb:14
23538 00401335 in main at d:/stb/b~stb.adb:104
23539 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
23540 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
23544 From this traceback we can see that the exception was raised in
23545 @file{stb.adb} at line 5, which was reached from a procedure call in
23546 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
23547 which contains the call to the main program.
23548 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
23549 and the output will vary from platform to platform.
23551 It is also possible to use @code{GDB} with these traceback addresses to debug
23552 the program. For example, we can break at a given code location, as reported
23553 in the stack traceback:
23559 Furthermore, this feature is not implemented inside Windows DLL. Only
23560 the non-symbolic traceback is reported in this case.
23563 (gdb) break *0x401373
23564 Breakpoint 1 at 0x401373: file stb.adb, line 5.
23568 It is important to note that the stack traceback addresses
23569 do not change when debug information is included. This is particularly useful
23570 because it makes it possible to release software without debug information (to
23571 minimize object size), get a field report that includes a stack traceback
23572 whenever an internal bug occurs, and then be able to retrieve the sequence
23573 of calls with the same program compiled with debug information.
23575 @node Tracebacks From Exception Occurrences (non-symbolic)
23576 @subsubsection Tracebacks From Exception Occurrences
23579 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
23580 The stack traceback is attached to the exception information string, and can
23581 be retrieved in an exception handler within the Ada program, by means of the
23582 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
23584 @smallexample @c ada
23586 with Ada.Exceptions;
23591 use Ada.Exceptions;
23599 Text_IO.Put_Line (Exception_Information (E));
23613 This program will output:
23618 Exception name: CONSTRAINT_ERROR
23619 Message: stb.adb:12
23620 Call stack traceback locations:
23621 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
23624 @node Tracebacks From Anywhere in a Program (non-symbolic)
23625 @subsubsection Tracebacks From Anywhere in a Program
23628 It is also possible to retrieve a stack traceback from anywhere in a
23629 program. For this you need to
23630 use the @code{GNAT.Traceback} API. This package includes a procedure called
23631 @code{Call_Chain} that computes a complete stack traceback, as well as useful
23632 display procedures described below. It is not necessary to use the
23633 @option{-E gnatbind} option in this case, because the stack traceback mechanism
23634 is invoked explicitly.
23637 In the following example we compute a traceback at a specific location in
23638 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
23639 convert addresses to strings:
23641 @smallexample @c ada
23643 with GNAT.Traceback;
23644 with GNAT.Debug_Utilities;
23650 use GNAT.Traceback;
23653 TB : Tracebacks_Array (1 .. 10);
23654 -- We are asking for a maximum of 10 stack frames.
23656 -- Len will receive the actual number of stack frames returned.
23658 Call_Chain (TB, Len);
23660 Text_IO.Put ("In STB.P1 : ");
23662 for K in 1 .. Len loop
23663 Text_IO.Put (Debug_Utilities.Image (TB (K)));
23684 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
23685 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
23689 You can then get further information by invoking the @code{addr2line}
23690 tool as described earlier (note that the hexadecimal addresses
23691 need to be specified in C format, with a leading ``0x'').
23693 @node Symbolic Traceback
23694 @subsection Symbolic Traceback
23695 @cindex traceback, symbolic
23698 A symbolic traceback is a stack traceback in which procedure names are
23699 associated with each code location.
23702 Note that this feature is not supported on all platforms. See
23703 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
23704 list of currently supported platforms.
23707 Note that the symbolic traceback requires that the program be compiled
23708 with debug information. If it is not compiled with debug information
23709 only the non-symbolic information will be valid.
23712 * Tracebacks From Exception Occurrences (symbolic)::
23713 * Tracebacks From Anywhere in a Program (symbolic)::
23716 @node Tracebacks From Exception Occurrences (symbolic)
23717 @subsubsection Tracebacks From Exception Occurrences
23719 @smallexample @c ada
23721 with GNAT.Traceback.Symbolic;
23727 raise Constraint_Error;
23744 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
23749 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
23752 0040149F in stb.p1 at stb.adb:8
23753 004014B7 in stb.p2 at stb.adb:13
23754 004014CF in stb.p3 at stb.adb:18
23755 004015DD in ada.stb at stb.adb:22
23756 00401461 in main at b~stb.adb:168
23757 004011C4 in __mingw_CRTStartup at crt1.c:200
23758 004011F1 in mainCRTStartup at crt1.c:222
23759 77E892A4 in ?? at ??:0
23763 In the above example the ``.\'' syntax in the @command{gnatmake} command
23764 is currently required by @command{addr2line} for files that are in
23765 the current working directory.
23766 Moreover, the exact sequence of linker options may vary from platform
23768 The above @option{-largs} section is for Windows platforms. By contrast,
23769 under Unix there is no need for the @option{-largs} section.
23770 Differences across platforms are due to details of linker implementation.
23772 @node Tracebacks From Anywhere in a Program (symbolic)
23773 @subsubsection Tracebacks From Anywhere in a Program
23776 It is possible to get a symbolic stack traceback
23777 from anywhere in a program, just as for non-symbolic tracebacks.
23778 The first step is to obtain a non-symbolic
23779 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
23780 information. Here is an example:
23782 @smallexample @c ada
23784 with GNAT.Traceback;
23785 with GNAT.Traceback.Symbolic;
23790 use GNAT.Traceback;
23791 use GNAT.Traceback.Symbolic;
23794 TB : Tracebacks_Array (1 .. 10);
23795 -- We are asking for a maximum of 10 stack frames.
23797 -- Len will receive the actual number of stack frames returned.
23799 Call_Chain (TB, Len);
23800 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
23813 @c ******************************
23815 @node Compatibility with HP Ada
23816 @chapter Compatibility with HP Ada
23817 @cindex Compatibility
23822 @cindex Compatibility between GNAT and HP Ada
23823 This chapter compares HP Ada (formerly known as ``DEC Ada'')
23824 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
23825 GNAT is highly compatible
23826 with HP Ada, and it should generally be straightforward to port code
23827 from the HP Ada environment to GNAT. However, there are a few language
23828 and implementation differences of which the user must be aware. These
23829 differences are discussed in this chapter. In
23830 addition, the operating environment and command structure for the
23831 compiler are different, and these differences are also discussed.
23833 For further details on these and other compatibility issues,
23834 see Appendix E of the HP publication
23835 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
23837 Except where otherwise indicated, the description of GNAT for OpenVMS
23838 applies to both the Alpha and I64 platforms.
23840 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
23841 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
23843 The discussion in this chapter addresses specifically the implementation
23844 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
23845 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
23846 GNAT always follows the Alpha implementation.
23848 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
23849 attributes are recognized, although only a subset of them can sensibly
23850 be implemented. The description of pragmas in
23851 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
23852 indicates whether or not they are applicable to non-VMS systems.
23855 * Ada Language Compatibility::
23856 * Differences in the Definition of Package System::
23857 * Language-Related Features::
23858 * The Package STANDARD::
23859 * The Package SYSTEM::
23860 * Tasking and Task-Related Features::
23861 * Pragmas and Pragma-Related Features::
23862 * Library of Predefined Units::
23864 * Main Program Definition::
23865 * Implementation-Defined Attributes::
23866 * Compiler and Run-Time Interfacing::
23867 * Program Compilation and Library Management::
23869 * Implementation Limits::
23870 * Tools and Utilities::
23873 @node Ada Language Compatibility
23874 @section Ada Language Compatibility
23877 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
23878 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
23879 with Ada 83, and therefore Ada 83 programs will compile
23880 and run under GNAT with
23881 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
23882 provides details on specific incompatibilities.
23884 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
23885 as well as the pragma @code{ADA_83}, to force the compiler to
23886 operate in Ada 83 mode. This mode does not guarantee complete
23887 conformance to Ada 83, but in practice is sufficient to
23888 eliminate most sources of incompatibilities.
23889 In particular, it eliminates the recognition of the
23890 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
23891 in Ada 83 programs is legal, and handles the cases of packages
23892 with optional bodies, and generics that instantiate unconstrained
23893 types without the use of @code{(<>)}.
23895 @node Differences in the Definition of Package System
23896 @section Differences in the Definition of Package @code{System}
23899 An Ada compiler is allowed to add
23900 implementation-dependent declarations to package @code{System}.
23902 GNAT does not take advantage of this permission, and the version of
23903 @code{System} provided by GNAT exactly matches that defined in the Ada
23906 However, HP Ada adds an extensive set of declarations to package
23908 as fully documented in the HP Ada manuals. To minimize changes required
23909 for programs that make use of these extensions, GNAT provides the pragma
23910 @code{Extend_System} for extending the definition of package System. By using:
23911 @cindex pragma @code{Extend_System}
23912 @cindex @code{Extend_System} pragma
23914 @smallexample @c ada
23917 pragma Extend_System (Aux_DEC);
23923 the set of definitions in @code{System} is extended to include those in
23924 package @code{System.Aux_DEC}.
23925 @cindex @code{System.Aux_DEC} package
23926 @cindex @code{Aux_DEC} package (child of @code{System})
23927 These definitions are incorporated directly into package @code{System},
23928 as though they had been declared there. For a
23929 list of the declarations added, see the spec of this package,
23930 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
23931 @cindex @file{s-auxdec.ads} file
23932 The pragma @code{Extend_System} is a configuration pragma, which means that
23933 it can be placed in the file @file{gnat.adc}, so that it will automatically
23934 apply to all subsequent compilations. See @ref{Configuration Pragmas},
23935 for further details.
23937 An alternative approach that avoids the use of the non-standard
23938 @code{Extend_System} pragma is to add a context clause to the unit that
23939 references these facilities:
23941 @smallexample @c ada
23943 with System.Aux_DEC;
23944 use System.Aux_DEC;
23949 The effect is not quite semantically identical to incorporating
23950 the declarations directly into package @code{System},
23951 but most programs will not notice a difference
23952 unless they use prefix notation (e.g.@: @code{System.Integer_8})
23953 to reference the entities directly in package @code{System}.
23954 For units containing such references,
23955 the prefixes must either be removed, or the pragma @code{Extend_System}
23958 @node Language-Related Features
23959 @section Language-Related Features
23962 The following sections highlight differences in types,
23963 representations of types, operations, alignment, and
23967 * Integer Types and Representations::
23968 * Floating-Point Types and Representations::
23969 * Pragmas Float_Representation and Long_Float::
23970 * Fixed-Point Types and Representations::
23971 * Record and Array Component Alignment::
23972 * Address Clauses::
23973 * Other Representation Clauses::
23976 @node Integer Types and Representations
23977 @subsection Integer Types and Representations
23980 The set of predefined integer types is identical in HP Ada and GNAT.
23981 Furthermore the representation of these integer types is also identical,
23982 including the capability of size clauses forcing biased representation.
23985 HP Ada for OpenVMS Alpha systems has defined the
23986 following additional integer types in package @code{System}:
24003 @code{LARGEST_INTEGER}
24007 In GNAT, the first four of these types may be obtained from the
24008 standard Ada package @code{Interfaces}.
24009 Alternatively, by use of the pragma @code{Extend_System}, identical
24010 declarations can be referenced directly in package @code{System}.
24011 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24013 @node Floating-Point Types and Representations
24014 @subsection Floating-Point Types and Representations
24015 @cindex Floating-Point types
24018 The set of predefined floating-point types is identical in HP Ada and GNAT.
24019 Furthermore the representation of these floating-point
24020 types is also identical. One important difference is that the default
24021 representation for HP Ada is @code{VAX_Float}, but the default representation
24024 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24025 pragma @code{Float_Representation} as described in the HP Ada
24027 For example, the declarations:
24029 @smallexample @c ada
24031 type F_Float is digits 6;
24032 pragma Float_Representation (VAX_Float, F_Float);
24037 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24039 This set of declarations actually appears in @code{System.Aux_DEC},
24041 the full set of additional floating-point declarations provided in
24042 the HP Ada version of package @code{System}.
24043 This and similar declarations may be accessed in a user program
24044 by using pragma @code{Extend_System}. The use of this
24045 pragma, and the related pragma @code{Long_Float} is described in further
24046 detail in the following section.
24048 @node Pragmas Float_Representation and Long_Float
24049 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24052 HP Ada provides the pragma @code{Float_Representation}, which
24053 acts as a program library switch to allow control over
24054 the internal representation chosen for the predefined
24055 floating-point types declared in the package @code{Standard}.
24056 The format of this pragma is as follows:
24058 @smallexample @c ada
24060 pragma Float_Representation(VAX_Float | IEEE_Float);
24065 This pragma controls the representation of floating-point
24070 @code{VAX_Float} specifies that floating-point
24071 types are represented by default with the VAX system hardware types
24072 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24073 Note that the @code{H-floating}
24074 type was available only on VAX systems, and is not available
24075 in either HP Ada or GNAT.
24078 @code{IEEE_Float} specifies that floating-point
24079 types are represented by default with the IEEE single and
24080 double floating-point types.
24084 GNAT provides an identical implementation of the pragma
24085 @code{Float_Representation}, except that it functions as a
24086 configuration pragma. Note that the
24087 notion of configuration pragma corresponds closely to the
24088 HP Ada notion of a program library switch.
24090 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24092 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24093 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24094 advisable to change the format of numbers passed to standard library
24095 routines, and if necessary explicit type conversions may be needed.
24097 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24098 efficient, and (given that it conforms to an international standard)
24099 potentially more portable.
24100 The situation in which @code{VAX_Float} may be useful is in interfacing
24101 to existing code and data that expect the use of @code{VAX_Float}.
24102 In such a situation use the predefined @code{VAX_Float}
24103 types in package @code{System}, as extended by
24104 @code{Extend_System}. For example, use @code{System.F_Float}
24105 to specify the 32-bit @code{F-Float} format.
24108 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24109 to allow control over the internal representation chosen
24110 for the predefined type @code{Long_Float} and for floating-point
24111 type declarations with digits specified in the range 7 .. 15.
24112 The format of this pragma is as follows:
24114 @smallexample @c ada
24116 pragma Long_Float (D_FLOAT | G_FLOAT);
24120 @node Fixed-Point Types and Representations
24121 @subsection Fixed-Point Types and Representations
24124 On HP Ada for OpenVMS Alpha systems, rounding is
24125 away from zero for both positive and negative numbers.
24126 Therefore, @code{+0.5} rounds to @code{1},
24127 and @code{-0.5} rounds to @code{-1}.
24129 On GNAT the results of operations
24130 on fixed-point types are in accordance with the Ada
24131 rules. In particular, results of operations on decimal
24132 fixed-point types are truncated.
24134 @node Record and Array Component Alignment
24135 @subsection Record and Array Component Alignment
24138 On HP Ada for OpenVMS Alpha, all non-composite components
24139 are aligned on natural boundaries. For example, 1-byte
24140 components are aligned on byte boundaries, 2-byte
24141 components on 2-byte boundaries, 4-byte components on 4-byte
24142 byte boundaries, and so on. The OpenVMS Alpha hardware
24143 runs more efficiently with naturally aligned data.
24145 On GNAT, alignment rules are compatible
24146 with HP Ada for OpenVMS Alpha.
24148 @node Address Clauses
24149 @subsection Address Clauses
24152 In HP Ada and GNAT, address clauses are supported for
24153 objects and imported subprograms.
24154 The predefined type @code{System.Address} is a private type
24155 in both compilers on Alpha OpenVMS, with the same representation
24156 (it is simply a machine pointer). Addition, subtraction, and comparison
24157 operations are available in the standard Ada package
24158 @code{System.Storage_Elements}, or in package @code{System}
24159 if it is extended to include @code{System.Aux_DEC} using a
24160 pragma @code{Extend_System} as previously described.
24162 Note that code that @code{with}'s both this extended package @code{System}
24163 and the package @code{System.Storage_Elements} should not @code{use}
24164 both packages, or ambiguities will result. In general it is better
24165 not to mix these two sets of facilities. The Ada package was
24166 designed specifically to provide the kind of features that HP Ada
24167 adds directly to package @code{System}.
24169 The type @code{System.Address} is a 64-bit integer type in GNAT for
24170 I64 OpenVMS. For more information,
24171 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24173 GNAT is compatible with HP Ada in its handling of address
24174 clauses, except for some limitations in
24175 the form of address clauses for composite objects with
24176 initialization. Such address clauses are easily replaced
24177 by the use of an explicitly-defined constant as described
24178 in the Ada Reference Manual (13.1(22)). For example, the sequence
24181 @smallexample @c ada
24183 X, Y : Integer := Init_Func;
24184 Q : String (X .. Y) := "abc";
24186 for Q'Address use Compute_Address;
24191 will be rejected by GNAT, since the address cannot be computed at the time
24192 that @code{Q} is declared. To achieve the intended effect, write instead:
24194 @smallexample @c ada
24197 X, Y : Integer := Init_Func;
24198 Q_Address : constant Address := Compute_Address;
24199 Q : String (X .. Y) := "abc";
24201 for Q'Address use Q_Address;
24207 which will be accepted by GNAT (and other Ada compilers), and is also
24208 compatible with Ada 83. A fuller description of the restrictions
24209 on address specifications is found in @ref{Top, GNAT Reference Manual,
24210 About This Guide, gnat_rm, GNAT Reference Manual}.
24212 @node Other Representation Clauses
24213 @subsection Other Representation Clauses
24216 GNAT implements in a compatible manner all the representation
24217 clauses supported by HP Ada. In addition, GNAT
24218 implements the representation clause forms that were introduced in Ada 95,
24219 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24221 @node The Package STANDARD
24222 @section The Package @code{STANDARD}
24225 The package @code{STANDARD}, as implemented by HP Ada, is fully
24226 described in the @cite{Ada Reference Manual} and in the
24227 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24228 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24230 In addition, HP Ada supports the Latin-1 character set in
24231 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24232 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24233 the type @code{WIDE_CHARACTER}.
24235 The floating-point types supported by GNAT are those
24236 supported by HP Ada, but the defaults are different, and are controlled by
24237 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24239 @node The Package SYSTEM
24240 @section The Package @code{SYSTEM}
24243 HP Ada provides a specific version of the package
24244 @code{SYSTEM} for each platform on which the language is implemented.
24245 For the complete spec of the package @code{SYSTEM}, see
24246 Appendix F of the @cite{HP Ada Language Reference Manual}.
24248 On HP Ada, the package @code{SYSTEM} includes the following conversion
24251 @item @code{TO_ADDRESS(INTEGER)}
24253 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24255 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24257 @item @code{TO_INTEGER(ADDRESS)}
24259 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24261 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24262 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24266 By default, GNAT supplies a version of @code{SYSTEM} that matches
24267 the definition given in the @cite{Ada Reference Manual}.
24269 is a subset of the HP system definitions, which is as
24270 close as possible to the original definitions. The only difference
24271 is that the definition of @code{SYSTEM_NAME} is different:
24273 @smallexample @c ada
24275 type Name is (SYSTEM_NAME_GNAT);
24276 System_Name : constant Name := SYSTEM_NAME_GNAT;
24281 Also, GNAT adds the Ada declarations for
24282 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24284 However, the use of the following pragma causes GNAT
24285 to extend the definition of package @code{SYSTEM} so that it
24286 encompasses the full set of HP-specific extensions,
24287 including the functions listed above:
24289 @smallexample @c ada
24291 pragma Extend_System (Aux_DEC);
24296 The pragma @code{Extend_System} is a configuration pragma that
24297 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24298 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24300 HP Ada does not allow the recompilation of the package
24301 @code{SYSTEM}. Instead HP Ada provides several pragmas
24302 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24303 to modify values in the package @code{SYSTEM}.
24304 On OpenVMS Alpha systems, the pragma
24305 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24306 its single argument.
24308 GNAT does permit the recompilation of package @code{SYSTEM} using
24309 the special switch @option{-gnatg}, and this switch can be used if
24310 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24311 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24312 or @code{MEMORY_SIZE} by any other means.
24314 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24315 enumeration literal @code{SYSTEM_NAME_GNAT}.
24317 The definitions provided by the use of
24319 @smallexample @c ada
24320 pragma Extend_System (AUX_Dec);
24324 are virtually identical to those provided by the HP Ada 83 package
24325 @code{SYSTEM}. One important difference is that the name of the
24327 function for type @code{UNSIGNED_LONGWORD} is changed to
24328 @code{TO_ADDRESS_LONG}.
24329 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
24330 discussion of why this change was necessary.
24333 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
24335 an extension to Ada 83 not strictly compatible with the reference manual.
24336 GNAT, in order to be exactly compatible with the standard,
24337 does not provide this capability. In HP Ada 83, the
24338 point of this definition is to deal with a call like:
24340 @smallexample @c ada
24341 TO_ADDRESS (16#12777#);
24345 Normally, according to Ada 83 semantics, one would expect this to be
24346 ambiguous, since it matches both the @code{INTEGER} and
24347 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
24348 However, in HP Ada 83, there is no ambiguity, since the
24349 definition using @i{universal_integer} takes precedence.
24351 In GNAT, since the version with @i{universal_integer} cannot be supplied,
24353 not possible to be 100% compatible. Since there are many programs using
24354 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
24356 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
24357 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
24359 @smallexample @c ada
24360 function To_Address (X : Integer) return Address;
24361 pragma Pure_Function (To_Address);
24363 function To_Address_Long (X : Unsigned_Longword) return Address;
24364 pragma Pure_Function (To_Address_Long);
24368 This means that programs using @code{TO_ADDRESS} for
24369 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
24371 @node Tasking and Task-Related Features
24372 @section Tasking and Task-Related Features
24375 This section compares the treatment of tasking in GNAT
24376 and in HP Ada for OpenVMS Alpha.
24377 The GNAT description applies to both Alpha and I64 OpenVMS.
24378 For detailed information on tasking in
24379 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
24380 relevant run-time reference manual.
24383 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
24384 * Assigning Task IDs::
24385 * Task IDs and Delays::
24386 * Task-Related Pragmas::
24387 * Scheduling and Task Priority::
24389 * External Interrupts::
24392 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24393 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
24396 On OpenVMS Alpha systems, each Ada task (except a passive
24397 task) is implemented as a single stream of execution
24398 that is created and managed by the kernel. On these
24399 systems, HP Ada tasking support is based on DECthreads,
24400 an implementation of the POSIX standard for threads.
24402 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
24403 code that calls DECthreads routines can be used together.
24404 The interaction between Ada tasks and DECthreads routines
24405 can have some benefits. For example when on OpenVMS Alpha,
24406 HP Ada can call C code that is already threaded.
24408 GNAT uses the facilities of DECthreads,
24409 and Ada tasks are mapped to threads.
24411 @node Assigning Task IDs
24412 @subsection Assigning Task IDs
24415 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
24416 the environment task that executes the main program. On
24417 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
24418 that have been created but are not yet activated.
24420 On OpenVMS Alpha systems, task IDs are assigned at
24421 activation. On GNAT systems, task IDs are also assigned at
24422 task creation but do not have the same form or values as
24423 task ID values in HP Ada. There is no null task, and the
24424 environment task does not have a specific task ID value.
24426 @node Task IDs and Delays
24427 @subsection Task IDs and Delays
24430 On OpenVMS Alpha systems, tasking delays are implemented
24431 using Timer System Services. The Task ID is used for the
24432 identification of the timer request (the @code{REQIDT} parameter).
24433 If Timers are used in the application take care not to use
24434 @code{0} for the identification, because cancelling such a timer
24435 will cancel all timers and may lead to unpredictable results.
24437 @node Task-Related Pragmas
24438 @subsection Task-Related Pragmas
24441 Ada supplies the pragma @code{TASK_STORAGE}, which allows
24442 specification of the size of the guard area for a task
24443 stack. (The guard area forms an area of memory that has no
24444 read or write access and thus helps in the detection of
24445 stack overflow.) On OpenVMS Alpha systems, if the pragma
24446 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
24447 area is created. In the absence of a pragma @code{TASK_STORAGE},
24448 a default guard area is created.
24450 GNAT supplies the following task-related pragmas:
24453 @item @code{TASK_INFO}
24455 This pragma appears within a task definition and
24456 applies to the task in which it appears. The argument
24457 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
24459 @item @code{TASK_STORAGE}
24461 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
24462 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
24463 @code{SUPPRESS}, and @code{VOLATILE}.
24465 @node Scheduling and Task Priority
24466 @subsection Scheduling and Task Priority
24469 HP Ada implements the Ada language requirement that
24470 when two tasks are eligible for execution and they have
24471 different priorities, the lower priority task does not
24472 execute while the higher priority task is waiting. The HP
24473 Ada Run-Time Library keeps a task running until either the
24474 task is suspended or a higher priority task becomes ready.
24476 On OpenVMS Alpha systems, the default strategy is round-
24477 robin with preemption. Tasks of equal priority take turns
24478 at the processor. A task is run for a certain period of
24479 time and then placed at the tail of the ready queue for
24480 its priority level.
24482 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
24483 which can be used to enable or disable round-robin
24484 scheduling of tasks with the same priority.
24485 See the relevant HP Ada run-time reference manual for
24486 information on using the pragmas to control HP Ada task
24489 GNAT follows the scheduling rules of Annex D (Real-Time
24490 Annex) of the @cite{Ada Reference Manual}. In general, this
24491 scheduling strategy is fully compatible with HP Ada
24492 although it provides some additional constraints (as
24493 fully documented in Annex D).
24494 GNAT implements time slicing control in a manner compatible with
24495 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
24496 are identical to the HP Ada 83 pragma of the same name.
24497 Note that it is not possible to mix GNAT tasking and
24498 HP Ada 83 tasking in the same program, since the two run-time
24499 libraries are not compatible.
24501 @node The Task Stack
24502 @subsection The Task Stack
24505 In HP Ada, a task stack is allocated each time a
24506 non-passive task is activated. As soon as the task is
24507 terminated, the storage for the task stack is deallocated.
24508 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
24509 a default stack size is used. Also, regardless of the size
24510 specified, some additional space is allocated for task
24511 management purposes. On OpenVMS Alpha systems, at least
24512 one page is allocated.
24514 GNAT handles task stacks in a similar manner. In accordance with
24515 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
24516 an alternative method for controlling the task stack size.
24517 The specification of the attribute @code{T'STORAGE_SIZE} is also
24518 supported in a manner compatible with HP Ada.
24520 @node External Interrupts
24521 @subsection External Interrupts
24524 On HP Ada, external interrupts can be associated with task entries.
24525 GNAT is compatible with HP Ada in its handling of external interrupts.
24527 @node Pragmas and Pragma-Related Features
24528 @section Pragmas and Pragma-Related Features
24531 Both HP Ada and GNAT supply all language-defined pragmas
24532 as specified by the Ada 83 standard. GNAT also supplies all
24533 language-defined pragmas introduced by Ada 95 and Ada 2005.
24534 In addition, GNAT implements the implementation-defined pragmas
24538 @item @code{AST_ENTRY}
24540 @item @code{COMMON_OBJECT}
24542 @item @code{COMPONENT_ALIGNMENT}
24544 @item @code{EXPORT_EXCEPTION}
24546 @item @code{EXPORT_FUNCTION}
24548 @item @code{EXPORT_OBJECT}
24550 @item @code{EXPORT_PROCEDURE}
24552 @item @code{EXPORT_VALUED_PROCEDURE}
24554 @item @code{FLOAT_REPRESENTATION}
24558 @item @code{IMPORT_EXCEPTION}
24560 @item @code{IMPORT_FUNCTION}
24562 @item @code{IMPORT_OBJECT}
24564 @item @code{IMPORT_PROCEDURE}
24566 @item @code{IMPORT_VALUED_PROCEDURE}
24568 @item @code{INLINE_GENERIC}
24570 @item @code{INTERFACE_NAME}
24572 @item @code{LONG_FLOAT}
24574 @item @code{MAIN_STORAGE}
24576 @item @code{PASSIVE}
24578 @item @code{PSECT_OBJECT}
24580 @item @code{SHARE_GENERIC}
24582 @item @code{SUPPRESS_ALL}
24584 @item @code{TASK_STORAGE}
24586 @item @code{TIME_SLICE}
24592 These pragmas are all fully implemented, with the exception of @code{TITLE},
24593 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
24594 recognized, but which have no
24595 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
24596 use of Ada protected objects. In GNAT, all generics are inlined.
24598 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
24599 a separate subprogram specification which must appear before the
24602 GNAT also supplies a number of implementation-defined pragmas as follows:
24604 @item @code{ABORT_DEFER}
24606 @item @code{ADA_83}
24608 @item @code{ADA_95}
24610 @item @code{ADA_05}
24612 @item @code{ANNOTATE}
24614 @item @code{ASSERT}
24616 @item @code{C_PASS_BY_COPY}
24618 @item @code{CPP_CLASS}
24620 @item @code{CPP_CONSTRUCTOR}
24622 @item @code{CPP_DESTRUCTOR}
24626 @item @code{EXTEND_SYSTEM}
24628 @item @code{LINKER_ALIAS}
24630 @item @code{LINKER_SECTION}
24632 @item @code{MACHINE_ATTRIBUTE}
24634 @item @code{NO_RETURN}
24636 @item @code{PURE_FUNCTION}
24638 @item @code{SOURCE_FILE_NAME}
24640 @item @code{SOURCE_REFERENCE}
24642 @item @code{TASK_INFO}
24644 @item @code{UNCHECKED_UNION}
24646 @item @code{UNIMPLEMENTED_UNIT}
24648 @item @code{UNIVERSAL_DATA}
24650 @item @code{UNSUPPRESS}
24652 @item @code{WARNINGS}
24654 @item @code{WEAK_EXTERNAL}
24658 For full details on these GNAT implementation-defined pragmas,
24659 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
24663 * Restrictions on the Pragma INLINE::
24664 * Restrictions on the Pragma INTERFACE::
24665 * Restrictions on the Pragma SYSTEM_NAME::
24668 @node Restrictions on the Pragma INLINE
24669 @subsection Restrictions on Pragma @code{INLINE}
24672 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
24674 @item Parameters cannot have a task type.
24676 @item Function results cannot be task types, unconstrained
24677 array types, or unconstrained types with discriminants.
24679 @item Bodies cannot declare the following:
24681 @item Subprogram body or stub (imported subprogram is allowed)
24685 @item Generic declarations
24687 @item Instantiations
24691 @item Access types (types derived from access types allowed)
24693 @item Array or record types
24695 @item Dependent tasks
24697 @item Direct recursive calls of subprogram or containing
24698 subprogram, directly or via a renaming
24704 In GNAT, the only restriction on pragma @code{INLINE} is that the
24705 body must occur before the call if both are in the same
24706 unit, and the size must be appropriately small. There are
24707 no other specific restrictions which cause subprograms to
24708 be incapable of being inlined.
24710 @node Restrictions on the Pragma INTERFACE
24711 @subsection Restrictions on Pragma @code{INTERFACE}
24714 The following restrictions on pragma @code{INTERFACE}
24715 are enforced by both HP Ada and GNAT:
24717 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
24718 Default is the default on OpenVMS Alpha systems.
24720 @item Parameter passing: Language specifies default
24721 mechanisms but can be overridden with an @code{EXPORT} pragma.
24724 @item Ada: Use internal Ada rules.
24726 @item Bliss, C: Parameters must be mode @code{in}; cannot be
24727 record or task type. Result cannot be a string, an
24728 array, or a record.
24730 @item Fortran: Parameters cannot have a task type. Result cannot
24731 be a string, an array, or a record.
24736 GNAT is entirely upwards compatible with HP Ada, and in addition allows
24737 record parameters for all languages.
24739 @node Restrictions on the Pragma SYSTEM_NAME
24740 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
24743 For HP Ada for OpenVMS Alpha, the enumeration literal
24744 for the type @code{NAME} is @code{OPENVMS_AXP}.
24745 In GNAT, the enumeration
24746 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
24748 @node Library of Predefined Units
24749 @section Library of Predefined Units
24752 A library of predefined units is provided as part of the
24753 HP Ada and GNAT implementations. HP Ada does not provide
24754 the package @code{MACHINE_CODE} but instead recommends importing
24757 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
24758 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
24760 The HP Ada Predefined Library units are modified to remove post-Ada 83
24761 incompatibilities and to make them interoperable with GNAT
24762 (@pxref{Changes to DECLIB}, for details).
24763 The units are located in the @file{DECLIB} directory.
24765 The GNAT RTL is contained in
24766 the @file{ADALIB} directory, and
24767 the default search path is set up to find @code{DECLIB} units in preference
24768 to @code{ADALIB} units with the same name (@code{TEXT_IO},
24769 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
24772 * Changes to DECLIB::
24775 @node Changes to DECLIB
24776 @subsection Changes to @code{DECLIB}
24779 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
24780 compatibility are minor and include the following:
24783 @item Adjusting the location of pragmas and record representation
24784 clauses to obey Ada 95 (and thus Ada 2005) rules
24786 @item Adding the proper notation to generic formal parameters
24787 that take unconstrained types in instantiation
24789 @item Adding pragma @code{ELABORATE_BODY} to package specs
24790 that have package bodies not otherwise allowed
24792 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
24793 ``@code{PROTECTD}''.
24794 Currently these are found only in the @code{STARLET} package spec.
24796 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
24797 where the address size is constrained to 32 bits.
24801 None of the above changes is visible to users.
24807 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
24810 @item Command Language Interpreter (CLI interface)
24812 @item DECtalk Run-Time Library (DTK interface)
24814 @item Librarian utility routines (LBR interface)
24816 @item General Purpose Run-Time Library (LIB interface)
24818 @item Math Run-Time Library (MTH interface)
24820 @item National Character Set Run-Time Library (NCS interface)
24822 @item Compiled Code Support Run-Time Library (OTS interface)
24824 @item Parallel Processing Run-Time Library (PPL interface)
24826 @item Screen Management Run-Time Library (SMG interface)
24828 @item Sort Run-Time Library (SOR interface)
24830 @item String Run-Time Library (STR interface)
24832 @item STARLET System Library
24835 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
24837 @item X Windows Toolkit (XT interface)
24839 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
24843 GNAT provides implementations of these HP bindings in the @code{DECLIB}
24844 directory, on both the Alpha and I64 OpenVMS platforms.
24846 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
24848 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
24849 A pragma @code{Linker_Options} has been added to packages @code{Xm},
24850 @code{Xt}, and @code{X_Lib}
24851 causing the default X/Motif sharable image libraries to be linked in. This
24852 is done via options files named @file{xm.opt}, @file{xt.opt}, and
24853 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
24855 It may be necessary to edit these options files to update or correct the
24856 library names if, for example, the newer X/Motif bindings from
24857 @file{ADA$EXAMPLES}
24858 had been (previous to installing GNAT) copied and renamed to supersede the
24859 default @file{ADA$PREDEFINED} versions.
24862 * Shared Libraries and Options Files::
24863 * Interfaces to C::
24866 @node Shared Libraries and Options Files
24867 @subsection Shared Libraries and Options Files
24870 When using the HP Ada
24871 predefined X and Motif bindings, the linking with their sharable images is
24872 done automatically by @command{GNAT LINK}.
24873 When using other X and Motif bindings, you need
24874 to add the corresponding sharable images to the command line for
24875 @code{GNAT LINK}. When linking with shared libraries, or with
24876 @file{.OPT} files, you must
24877 also add them to the command line for @command{GNAT LINK}.
24879 A shared library to be used with GNAT is built in the same way as other
24880 libraries under VMS. The VMS Link command can be used in standard fashion.
24882 @node Interfaces to C
24883 @subsection Interfaces to C
24887 provides the following Ada types and operations:
24890 @item C types package (@code{C_TYPES})
24892 @item C strings (@code{C_TYPES.NULL_TERMINATED})
24894 @item Other_types (@code{SHORT_INT})
24898 Interfacing to C with GNAT, you can use the above approach
24899 described for HP Ada or the facilities of Annex B of
24900 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
24901 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
24902 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
24904 The @option{-gnatF} qualifier forces default and explicit
24905 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
24906 to be uppercased for compatibility with the default behavior
24907 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
24909 @node Main Program Definition
24910 @section Main Program Definition
24913 The following section discusses differences in the
24914 definition of main programs on HP Ada and GNAT.
24915 On HP Ada, main programs are defined to meet the
24916 following conditions:
24918 @item Procedure with no formal parameters (returns @code{0} upon
24921 @item Procedure with no formal parameters (returns @code{42} when
24922 an unhandled exception is raised)
24924 @item Function with no formal parameters whose returned value
24925 is of a discrete type
24927 @item Procedure with one @code{out} formal of a discrete type for
24928 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
24933 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
24934 a main function or main procedure returns a discrete
24935 value whose size is less than 64 bits (32 on VAX systems),
24936 the value is zero- or sign-extended as appropriate.
24937 On GNAT, main programs are defined as follows:
24939 @item Must be a non-generic, parameterless subprogram that
24940 is either a procedure or function returning an Ada
24941 @code{STANDARD.INTEGER} (the predefined type)
24943 @item Cannot be a generic subprogram or an instantiation of a
24947 @node Implementation-Defined Attributes
24948 @section Implementation-Defined Attributes
24951 GNAT provides all HP Ada implementation-defined
24954 @node Compiler and Run-Time Interfacing
24955 @section Compiler and Run-Time Interfacing
24958 HP Ada provides the following qualifiers to pass options to the linker
24961 @item @option{/WAIT} and @option{/SUBMIT}
24963 @item @option{/COMMAND}
24965 @item @option{/@r{[}NO@r{]}MAP}
24967 @item @option{/OUTPUT=@var{file-spec}}
24969 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
24973 To pass options to the linker, GNAT provides the following
24977 @item @option{/EXECUTABLE=@var{exec-name}}
24979 @item @option{/VERBOSE}
24981 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
24985 For more information on these switches, see
24986 @ref{Switches for gnatlink}.
24987 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
24988 to control optimization. HP Ada also supplies the
24991 @item @code{OPTIMIZE}
24993 @item @code{INLINE}
24995 @item @code{INLINE_GENERIC}
24997 @item @code{SUPPRESS_ALL}
24999 @item @code{PASSIVE}
25003 In GNAT, optimization is controlled strictly by command
25004 line parameters, as described in the corresponding section of this guide.
25005 The HP pragmas for control of optimization are
25006 recognized but ignored.
25008 Note that in GNAT, the default is optimization off, whereas in HP Ada
25009 the default is that optimization is turned on.
25011 @node Program Compilation and Library Management
25012 @section Program Compilation and Library Management
25015 HP Ada and GNAT provide a comparable set of commands to
25016 build programs. HP Ada also provides a program library,
25017 which is a concept that does not exist on GNAT. Instead,
25018 GNAT provides directories of sources that are compiled as
25021 The following table summarizes
25022 the HP Ada commands and provides
25023 equivalent GNAT commands. In this table, some GNAT
25024 equivalents reflect the fact that GNAT does not use the
25025 concept of a program library. Instead, it uses a model
25026 in which collections of source and object files are used
25027 in a manner consistent with other languages like C and
25028 Fortran. Therefore, standard system file commands are used
25029 to manipulate these elements. Those GNAT commands are marked with
25031 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25034 @multitable @columnfractions .35 .65
25036 @item @emph{HP Ada Command}
25037 @tab @emph{GNAT Equivalent / Description}
25039 @item @command{ADA}
25040 @tab @command{GNAT COMPILE}@*
25041 Invokes the compiler to compile one or more Ada source files.
25043 @item @command{ACS ATTACH}@*
25044 @tab [No equivalent]@*
25045 Switches control of terminal from current process running the program
25048 @item @command{ACS CHECK}
25049 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25050 Forms the execution closure of one
25051 or more compiled units and checks completeness and currency.
25053 @item @command{ACS COMPILE}
25054 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25055 Forms the execution closure of one or
25056 more specified units, checks completeness and currency,
25057 identifies units that have revised source files, compiles same,
25058 and recompiles units that are or will become obsolete.
25059 Also completes incomplete generic instantiations.
25061 @item @command{ACS COPY FOREIGN}
25063 Copies a foreign object file into the program library as a
25066 @item @command{ACS COPY UNIT}
25068 Copies a compiled unit from one program library to another.
25070 @item @command{ACS CREATE LIBRARY}
25071 @tab Create /directory (*)@*
25072 Creates a program library.
25074 @item @command{ACS CREATE SUBLIBRARY}
25075 @tab Create /directory (*)@*
25076 Creates a program sublibrary.
25078 @item @command{ACS DELETE LIBRARY}
25080 Deletes a program library and its contents.
25082 @item @command{ACS DELETE SUBLIBRARY}
25084 Deletes a program sublibrary and its contents.
25086 @item @command{ACS DELETE UNIT}
25087 @tab Delete file (*)@*
25088 On OpenVMS systems, deletes one or more compiled units from
25089 the current program library.
25091 @item @command{ACS DIRECTORY}
25092 @tab Directory (*)@*
25093 On OpenVMS systems, lists units contained in the current
25096 @item @command{ACS ENTER FOREIGN}
25098 Allows the import of a foreign body as an Ada library
25099 spec and enters a reference to a pointer.
25101 @item @command{ACS ENTER UNIT}
25103 Enters a reference (pointer) from the current program library to
25104 a unit compiled into another program library.
25106 @item @command{ACS EXIT}
25107 @tab [No equivalent]@*
25108 Exits from the program library manager.
25110 @item @command{ACS EXPORT}
25112 Creates an object file that contains system-specific object code
25113 for one or more units. With GNAT, object files can simply be copied
25114 into the desired directory.
25116 @item @command{ACS EXTRACT SOURCE}
25118 Allows access to the copied source file for each Ada compilation unit
25120 @item @command{ACS HELP}
25121 @tab @command{HELP GNAT}@*
25122 Provides online help.
25124 @item @command{ACS LINK}
25125 @tab @command{GNAT LINK}@*
25126 Links an object file containing Ada units into an executable file.
25128 @item @command{ACS LOAD}
25130 Loads (partially compiles) Ada units into the program library.
25131 Allows loading a program from a collection of files into a library
25132 without knowing the relationship among units.
25134 @item @command{ACS MERGE}
25136 Merges into the current program library, one or more units from
25137 another library where they were modified.
25139 @item @command{ACS RECOMPILE}
25140 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25141 Recompiles from external or copied source files any obsolete
25142 unit in the closure. Also, completes any incomplete generic
25145 @item @command{ACS REENTER}
25146 @tab @command{GNAT MAKE}@*
25147 Reenters current references to units compiled after last entered
25148 with the @command{ACS ENTER UNIT} command.
25150 @item @command{ACS SET LIBRARY}
25151 @tab Set default (*)@*
25152 Defines a program library to be the compilation context as well
25153 as the target library for compiler output and commands in general.
25155 @item @command{ACS SET PRAGMA}
25156 @tab Edit @file{gnat.adc} (*)@*
25157 Redefines specified values of the library characteristics
25158 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25159 and @code{Float_Representation}.
25161 @item @command{ACS SET SOURCE}
25162 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25163 Defines the source file search list for the @command{ACS COMPILE} command.
25165 @item @command{ACS SHOW LIBRARY}
25166 @tab Directory (*)@*
25167 Lists information about one or more program libraries.
25169 @item @command{ACS SHOW PROGRAM}
25170 @tab [No equivalent]@*
25171 Lists information about the execution closure of one or
25172 more units in the program library.
25174 @item @command{ACS SHOW SOURCE}
25175 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25176 Shows the source file search used when compiling units.
25178 @item @command{ACS SHOW VERSION}
25179 @tab Compile with @option{VERBOSE} option
25180 Displays the version number of the compiler and program library
25183 @item @command{ACS SPAWN}
25184 @tab [No equivalent]@*
25185 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25188 @item @command{ACS VERIFY}
25189 @tab [No equivalent]@*
25190 Performs a series of consistency checks on a program library to
25191 determine whether the library structure and library files are in
25198 @section Input-Output
25201 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25202 Management Services (RMS) to perform operations on
25206 HP Ada and GNAT predefine an identical set of input-
25207 output packages. To make the use of the
25208 generic @code{TEXT_IO} operations more convenient, HP Ada
25209 provides predefined library packages that instantiate the
25210 integer and floating-point operations for the predefined
25211 integer and floating-point types as shown in the following table.
25213 @multitable @columnfractions .45 .55
25214 @item @emph{Package Name} @tab Instantiation
25216 @item @code{INTEGER_TEXT_IO}
25217 @tab @code{INTEGER_IO(INTEGER)}
25219 @item @code{SHORT_INTEGER_TEXT_IO}
25220 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25222 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25223 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25225 @item @code{FLOAT_TEXT_IO}
25226 @tab @code{FLOAT_IO(FLOAT)}
25228 @item @code{LONG_FLOAT_TEXT_IO}
25229 @tab @code{FLOAT_IO(LONG_FLOAT)}
25233 The HP Ada predefined packages and their operations
25234 are implemented using OpenVMS Alpha files and input-output
25235 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25236 Familiarity with the following is recommended:
25238 @item RMS file organizations and access methods
25240 @item OpenVMS file specifications and directories
25242 @item OpenVMS File Definition Language (FDL)
25246 GNAT provides I/O facilities that are completely
25247 compatible with HP Ada. The distribution includes the
25248 standard HP Ada versions of all I/O packages, operating
25249 in a manner compatible with HP Ada. In particular, the
25250 following packages are by default the HP Ada (Ada 83)
25251 versions of these packages rather than the renamings
25252 suggested in Annex J of the Ada Reference Manual:
25254 @item @code{TEXT_IO}
25256 @item @code{SEQUENTIAL_IO}
25258 @item @code{DIRECT_IO}
25262 The use of the standard child package syntax (for
25263 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25265 GNAT provides HP-compatible predefined instantiations
25266 of the @code{TEXT_IO} packages, and also
25267 provides the standard predefined instantiations required
25268 by the @cite{Ada Reference Manual}.
25270 For further information on how GNAT interfaces to the file
25271 system or how I/O is implemented in programs written in
25272 mixed languages, see @ref{Implementation of the Standard I/O,,,
25273 gnat_rm, GNAT Reference Manual}.
25274 This chapter covers the following:
25276 @item Standard I/O packages
25278 @item @code{FORM} strings
25280 @item @code{ADA.DIRECT_IO}
25282 @item @code{ADA.SEQUENTIAL_IO}
25284 @item @code{ADA.TEXT_IO}
25286 @item Stream pointer positioning
25288 @item Reading and writing non-regular files
25290 @item @code{GET_IMMEDIATE}
25292 @item Treating @code{TEXT_IO} files as streams
25299 @node Implementation Limits
25300 @section Implementation Limits
25303 The following table lists implementation limits for HP Ada
25305 @multitable @columnfractions .60 .20 .20
25307 @item @emph{Compilation Parameter}
25312 @item In a subprogram or entry declaration, maximum number of
25313 formal parameters that are of an unconstrained record type
25318 @item Maximum identifier length (number of characters)
25323 @item Maximum number of characters in a source line
25328 @item Maximum collection size (number of bytes)
25333 @item Maximum number of discriminants for a record type
25338 @item Maximum number of formal parameters in an entry or
25339 subprogram declaration
25344 @item Maximum number of dimensions in an array type
25349 @item Maximum number of library units and subunits in a compilation.
25354 @item Maximum number of library units and subunits in an execution.
25359 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
25360 or @code{PSECT_OBJECT}
25365 @item Maximum number of enumeration literals in an enumeration type
25371 @item Maximum number of lines in a source file
25376 @item Maximum number of bits in any object
25381 @item Maximum size of the static portion of a stack frame (approximate)
25386 @node Tools and Utilities
25387 @section Tools and Utilities
25390 The following table lists some of the OpenVMS development tools
25391 available for HP Ada, and the corresponding tools for
25392 use with @value{EDITION} on Alpha and I64 platforms.
25393 Aside from the debugger, all the OpenVMS tools identified are part
25394 of the DECset package.
25397 @c Specify table in TeX since Texinfo does a poor job
25401 \settabs\+Language-Sensitive Editor\quad
25402 &Product with HP Ada\quad
25405 &\it Product with HP Ada
25406 & \it Product with GNAT Pro\cr
25408 \+Code Management System
25412 \+Language-Sensitive Editor
25414 & emacs or HP LSE (Alpha)\cr
25424 & OpenVMS Debug (I64)\cr
25426 \+Source Code Analyzer /
25443 \+Coverage Analyzer
25447 \+Module Management
25449 & Not applicable\cr
25459 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
25460 @c the TeX version above for the printed version
25462 @c @multitable @columnfractions .3 .4 .4
25463 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
25465 @tab @i{Tool with HP Ada}
25466 @tab @i{Tool with @value{EDITION}}
25467 @item Code Management@*System
25470 @item Language-Sensitive@*Editor
25472 @tab emacs or HP LSE (Alpha)
25481 @tab OpenVMS Debug (I64)
25482 @item Source Code Analyzer /@*Cross Referencer
25486 @tab HP Digital Test@*Manager (DTM)
25488 @item Performance and@*Coverage Analyzer
25491 @item Module Management@*System
25493 @tab Not applicable
25500 @c **************************************
25501 @node Platform-Specific Information for the Run-Time Libraries
25502 @appendix Platform-Specific Information for the Run-Time Libraries
25503 @cindex Tasking and threads libraries
25504 @cindex Threads libraries and tasking
25505 @cindex Run-time libraries (platform-specific information)
25508 The GNAT run-time implementation may vary with respect to both the
25509 underlying threads library and the exception handling scheme.
25510 For threads support, one or more of the following are supplied:
25512 @item @b{native threads library}, a binding to the thread package from
25513 the underlying operating system
25515 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
25516 POSIX thread package
25520 For exception handling, either or both of two models are supplied:
25522 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
25523 Most programs should experience a substantial speed improvement by
25524 being compiled with a ZCX run-time.
25525 This is especially true for
25526 tasking applications or applications with many exception handlers.}
25527 @cindex Zero-Cost Exceptions
25528 @cindex ZCX (Zero-Cost Exceptions)
25529 which uses binder-generated tables that
25530 are interrogated at run time to locate a handler
25532 @item @b{setjmp / longjmp} (``SJLJ''),
25533 @cindex setjmp/longjmp Exception Model
25534 @cindex SJLJ (setjmp/longjmp Exception Model)
25535 which uses dynamically-set data to establish
25536 the set of handlers
25540 This appendix summarizes which combinations of threads and exception support
25541 are supplied on various GNAT platforms.
25542 It then shows how to select a particular library either
25543 permanently or temporarily,
25544 explains the properties of (and tradeoffs among) the various threads
25545 libraries, and provides some additional
25546 information about several specific platforms.
25549 * Summary of Run-Time Configurations::
25550 * Specifying a Run-Time Library::
25551 * Choosing the Scheduling Policy::
25552 * Solaris-Specific Considerations::
25553 * Linux-Specific Considerations::
25554 * AIX-Specific Considerations::
25555 * Irix-Specific Considerations::
25556 * RTX-Specific Considerations::
25559 @node Summary of Run-Time Configurations
25560 @section Summary of Run-Time Configurations
25562 @multitable @columnfractions .30 .70
25563 @item @b{alpha-openvms}
25564 @item @code{@ @ }@i{rts-native (default)}
25565 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25566 @item @code{@ @ @ @ }Exceptions @tab ZCX
25568 @item @b{alpha-tru64}
25569 @item @code{@ @ }@i{rts-native (default)}
25570 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25571 @item @code{@ @ @ @ }Exceptions @tab ZCX
25573 @item @code{@ @ }@i{rts-sjlj}
25574 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
25575 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25577 @item @b{ia64-hp_linux}
25578 @item @code{@ @ }@i{rts-native (default)}
25579 @item @code{@ @ @ @ }Tasking @tab pthread library
25580 @item @code{@ @ @ @ }Exceptions @tab ZCX
25582 @item @b{ia64-hpux}
25583 @item @code{@ @ }@i{rts-native (default)}
25584 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25585 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25587 @item @b{ia64-openvms}
25588 @item @code{@ @ }@i{rts-native (default)}
25589 @item @code{@ @ @ @ }Tasking @tab native VMS threads
25590 @item @code{@ @ @ @ }Exceptions @tab ZCX
25592 @item @b{ia64-sgi_linux}
25593 @item @code{@ @ }@i{rts-native (default)}
25594 @item @code{@ @ @ @ }Tasking @tab pthread library
25595 @item @code{@ @ @ @ }Exceptions @tab ZCX
25597 @item @b{mips-irix}
25598 @item @code{@ @ }@i{rts-native (default)}
25599 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
25600 @item @code{@ @ @ @ }Exceptions @tab ZCX
25603 @item @code{@ @ }@i{rts-native (default)}
25604 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25605 @item @code{@ @ @ @ }Exceptions @tab ZCX
25607 @item @code{@ @ }@i{rts-sjlj}
25608 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
25609 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25612 @item @code{@ @ }@i{rts-native (default)}
25613 @item @code{@ @ @ @ }Tasking @tab native AIX threads
25614 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25616 @item @b{ppc-darwin}
25617 @item @code{@ @ }@i{rts-native (default)}
25618 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
25619 @item @code{@ @ @ @ }Exceptions @tab ZCX
25621 @item @b{sparc-solaris} @tab
25622 @item @code{@ @ }@i{rts-native (default)}
25623 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25624 @item @code{@ @ @ @ }Exceptions @tab ZCX
25626 @item @code{@ @ }@i{rts-pthread}
25627 @item @code{@ @ @ @ }Tasking @tab pthread library
25628 @item @code{@ @ @ @ }Exceptions @tab ZCX
25630 @item @code{@ @ }@i{rts-sjlj}
25631 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25632 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25634 @item @b{sparc64-solaris} @tab
25635 @item @code{@ @ }@i{rts-native (default)}
25636 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
25637 @item @code{@ @ @ @ }Exceptions @tab ZCX
25639 @item @b{x86-linux}
25640 @item @code{@ @ }@i{rts-native (default)}
25641 @item @code{@ @ @ @ }Tasking @tab pthread library
25642 @item @code{@ @ @ @ }Exceptions @tab ZCX
25644 @item @code{@ @ }@i{rts-sjlj}
25645 @item @code{@ @ @ @ }Tasking @tab pthread library
25646 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25649 @item @code{@ @ }@i{rts-native (default)}
25650 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
25651 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25653 @item @b{x86-solaris}
25654 @item @code{@ @ }@i{rts-native (default)}
25655 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
25656 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25658 @item @b{x86-windows}
25659 @item @code{@ @ }@i{rts-native (default)}
25660 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25661 @item @code{@ @ @ @ }Exceptions @tab ZCX
25663 @item @code{@ @ }@i{rts-sjlj (default)}
25664 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
25665 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25667 @item @b{x86-windows-rtx}
25668 @item @code{@ @ }@i{rts-rtx-rtss (default)}
25669 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
25670 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25672 @item @code{@ @ }@i{rts-rtx-w32}
25673 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
25674 @item @code{@ @ @ @ }Exceptions @tab ZCX
25676 @item @b{x86_64-linux}
25677 @item @code{@ @ }@i{rts-native (default)}
25678 @item @code{@ @ @ @ }Tasking @tab pthread library
25679 @item @code{@ @ @ @ }Exceptions @tab ZCX
25681 @item @code{@ @ }@i{rts-sjlj}
25682 @item @code{@ @ @ @ }Tasking @tab pthread library
25683 @item @code{@ @ @ @ }Exceptions @tab SJLJ
25687 @node Specifying a Run-Time Library
25688 @section Specifying a Run-Time Library
25691 The @file{adainclude} subdirectory containing the sources of the GNAT
25692 run-time library, and the @file{adalib} subdirectory containing the
25693 @file{ALI} files and the static and/or shared GNAT library, are located
25694 in the gcc target-dependent area:
25697 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
25701 As indicated above, on some platforms several run-time libraries are supplied.
25702 These libraries are installed in the target dependent area and
25703 contain a complete source and binary subdirectory. The detailed description
25704 below explains the differences between the different libraries in terms of
25705 their thread support.
25707 The default run-time library (when GNAT is installed) is @emph{rts-native}.
25708 This default run time is selected by the means of soft links.
25709 For example on x86-linux:
25715 +--- adainclude----------+
25717 +--- adalib-----------+ |
25719 +--- rts-native | |
25721 | +--- adainclude <---+
25723 | +--- adalib <----+
25734 If the @i{rts-sjlj} library is to be selected on a permanent basis,
25735 these soft links can be modified with the following commands:
25739 $ rm -f adainclude adalib
25740 $ ln -s rts-sjlj/adainclude adainclude
25741 $ ln -s rts-sjlj/adalib adalib
25745 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
25746 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
25747 @file{$target/ada_object_path}.
25749 Selecting another run-time library temporarily can be
25750 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
25751 @cindex @option{--RTS} option
25753 @node Choosing the Scheduling Policy
25754 @section Choosing the Scheduling Policy
25757 When using a POSIX threads implementation, you have a choice of several
25758 scheduling policies: @code{SCHED_FIFO},
25759 @cindex @code{SCHED_FIFO} scheduling policy
25761 @cindex @code{SCHED_RR} scheduling policy
25762 and @code{SCHED_OTHER}.
25763 @cindex @code{SCHED_OTHER} scheduling policy
25764 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
25765 or @code{SCHED_RR} requires special (e.g., root) privileges.
25767 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
25769 @cindex @code{SCHED_FIFO} scheduling policy
25770 you can use one of the following:
25774 @code{pragma Time_Slice (0.0)}
25775 @cindex pragma Time_Slice
25777 the corresponding binder option @option{-T0}
25778 @cindex @option{-T0} option
25780 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
25781 @cindex pragma Task_Dispatching_Policy
25785 To specify @code{SCHED_RR},
25786 @cindex @code{SCHED_RR} scheduling policy
25787 you should use @code{pragma Time_Slice} with a
25788 value greater than @code{0.0}, or else use the corresponding @option{-T}
25791 @node Solaris-Specific Considerations
25792 @section Solaris-Specific Considerations
25793 @cindex Solaris Sparc threads libraries
25796 This section addresses some topics related to the various threads libraries
25800 * Solaris Threads Issues::
25803 @node Solaris Threads Issues
25804 @subsection Solaris Threads Issues
25807 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
25808 library based on POSIX threads --- @emph{rts-pthread}.
25809 @cindex rts-pthread threads library
25810 This run-time library has the advantage of being mostly shared across all
25811 POSIX-compliant thread implementations, and it also provides under
25812 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
25813 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
25814 and @code{PTHREAD_PRIO_PROTECT}
25815 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
25816 semantics that can be selected using the predefined pragma
25817 @code{Locking_Policy}
25818 @cindex pragma Locking_Policy (under rts-pthread)
25820 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
25821 @cindex @code{Inheritance_Locking} (under rts-pthread)
25822 @cindex @code{Ceiling_Locking} (under rts-pthread)
25824 As explained above, the native run-time library is based on the Solaris thread
25825 library (@code{libthread}) and is the default library.
25827 When the Solaris threads library is used (this is the default), programs
25828 compiled with GNAT can automatically take advantage of
25829 and can thus execute on multiple processors.
25830 The user can alternatively specify a processor on which the program should run
25831 to emulate a single-processor system. The multiprocessor / uniprocessor choice
25833 setting the environment variable @env{GNAT_PROCESSOR}
25834 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
25835 to one of the following:
25839 Use the default configuration (run the program on all
25840 available processors) - this is the same as having @code{GNAT_PROCESSOR}
25844 Let the run-time implementation choose one processor and run the program on
25847 @item 0 .. Last_Proc
25848 Run the program on the specified processor.
25849 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
25850 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
25853 @node Linux-Specific Considerations
25854 @section Linux-Specific Considerations
25855 @cindex Linux threads libraries
25858 On GNU/Linux without NPTL support (usually system with GNU C Library
25859 older than 2.3), the signal model is not POSIX compliant, which means
25860 that to send a signal to the process, you need to send the signal to all
25861 threads, e.g.@: by using @code{killpg()}.
25863 @node AIX-Specific Considerations
25864 @section AIX-Specific Considerations
25865 @cindex AIX resolver library
25868 On AIX, the resolver library initializes some internal structure on
25869 the first call to @code{get*by*} functions, which are used to implement
25870 @code{GNAT.Sockets.Get_Host_By_Name} and
25871 @code{GNAT.Sockets.Get_Host_By_Address}.
25872 If such initialization occurs within an Ada task, and the stack size for
25873 the task is the default size, a stack overflow may occur.
25875 To avoid this overflow, the user should either ensure that the first call
25876 to @code{GNAT.Sockets.Get_Host_By_Name} or
25877 @code{GNAT.Sockets.Get_Host_By_Addrss}
25878 occurs in the environment task, or use @code{pragma Storage_Size} to
25879 specify a sufficiently large size for the stack of the task that contains
25882 @node Irix-Specific Considerations
25883 @section Irix-Specific Considerations
25884 @cindex Irix libraries
25887 The GCC support libraries coming with the Irix compiler have moved to
25888 their canonical place with respect to the general Irix ABI related
25889 conventions. Running applications built with the default shared GNAT
25890 run-time now requires the LD_LIBRARY_PATH environment variable to
25891 include this location. A possible way to achieve this is to issue the
25892 following command line on a bash prompt:
25896 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
25900 @node RTX-Specific Considerations
25901 @section RTX-Specific Considerations
25902 @cindex RTX libraries
25905 The Real-time Extension (RTX) to Windows is based on the Windows Win32
25906 API. Applications can be built to work in two different modes:
25910 Windows executables that run in Ring 3 to utilize memory protection
25911 (@emph{rts-rtx-w32}).
25914 Real-time subsystem (RTSS) executables that run in Ring 0, where
25915 performance can be optimized with RTSS applications taking precedent
25916 over all Windows applications (@emph{rts-rtx-rtss}).
25920 @c *******************************
25921 @node Example of Binder Output File
25922 @appendix Example of Binder Output File
25925 This Appendix displays the source code for @command{gnatbind}'s output
25926 file generated for a simple ``Hello World'' program.
25927 Comments have been added for clarification purposes.
25929 @smallexample @c adanocomment
25933 -- The package is called Ada_Main unless this name is actually used
25934 -- as a unit name in the partition, in which case some other unique
25938 package ada_main is
25940 Elab_Final_Code : Integer;
25941 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
25943 -- The main program saves the parameters (argument count,
25944 -- argument values, environment pointer) in global variables
25945 -- for later access by other units including
25946 -- Ada.Command_Line.
25948 gnat_argc : Integer;
25949 gnat_argv : System.Address;
25950 gnat_envp : System.Address;
25952 -- The actual variables are stored in a library routine. This
25953 -- is useful for some shared library situations, where there
25954 -- are problems if variables are not in the library.
25956 pragma Import (C, gnat_argc);
25957 pragma Import (C, gnat_argv);
25958 pragma Import (C, gnat_envp);
25960 -- The exit status is similarly an external location
25962 gnat_exit_status : Integer;
25963 pragma Import (C, gnat_exit_status);
25965 GNAT_Version : constant String :=
25966 "GNAT Version: 6.0.0w (20061115)";
25967 pragma Export (C, GNAT_Version, "__gnat_version");
25969 -- This is the generated adafinal routine that performs
25970 -- finalization at the end of execution. In the case where
25971 -- Ada is the main program, this main program makes a call
25972 -- to adafinal at program termination.
25974 procedure adafinal;
25975 pragma Export (C, adafinal, "adafinal");
25977 -- This is the generated adainit routine that performs
25978 -- initialization at the start of execution. In the case
25979 -- where Ada is the main program, this main program makes
25980 -- a call to adainit at program startup.
25983 pragma Export (C, adainit, "adainit");
25985 -- This routine is called at the start of execution. It is
25986 -- a dummy routine that is used by the debugger to breakpoint
25987 -- at the start of execution.
25989 procedure Break_Start;
25990 pragma Import (C, Break_Start, "__gnat_break_start");
25992 -- This is the actual generated main program (it would be
25993 -- suppressed if the no main program switch were used). As
25994 -- required by standard system conventions, this program has
25995 -- the external name main.
25999 argv : System.Address;
26000 envp : System.Address)
26002 pragma Export (C, main, "main");
26004 -- The following set of constants give the version
26005 -- identification values for every unit in the bound
26006 -- partition. This identification is computed from all
26007 -- dependent semantic units, and corresponds to the
26008 -- string that would be returned by use of the
26009 -- Body_Version or Version attributes.
26011 type Version_32 is mod 2 ** 32;
26012 u00001 : constant Version_32 := 16#7880BEB3#;
26013 u00002 : constant Version_32 := 16#0D24CBD0#;
26014 u00003 : constant Version_32 := 16#3283DBEB#;
26015 u00004 : constant Version_32 := 16#2359F9ED#;
26016 u00005 : constant Version_32 := 16#664FB847#;
26017 u00006 : constant Version_32 := 16#68E803DF#;
26018 u00007 : constant Version_32 := 16#5572E604#;
26019 u00008 : constant Version_32 := 16#46B173D8#;
26020 u00009 : constant Version_32 := 16#156A40CF#;
26021 u00010 : constant Version_32 := 16#033DABE0#;
26022 u00011 : constant Version_32 := 16#6AB38FEA#;
26023 u00012 : constant Version_32 := 16#22B6217D#;
26024 u00013 : constant Version_32 := 16#68A22947#;
26025 u00014 : constant Version_32 := 16#18CC4A56#;
26026 u00015 : constant Version_32 := 16#08258E1B#;
26027 u00016 : constant Version_32 := 16#367D5222#;
26028 u00017 : constant Version_32 := 16#20C9ECA4#;
26029 u00018 : constant Version_32 := 16#50D32CB6#;
26030 u00019 : constant Version_32 := 16#39A8BB77#;
26031 u00020 : constant Version_32 := 16#5CF8FA2B#;
26032 u00021 : constant Version_32 := 16#2F1EB794#;
26033 u00022 : constant Version_32 := 16#31AB6444#;
26034 u00023 : constant Version_32 := 16#1574B6E9#;
26035 u00024 : constant Version_32 := 16#5109C189#;
26036 u00025 : constant Version_32 := 16#56D770CD#;
26037 u00026 : constant Version_32 := 16#02F9DE3D#;
26038 u00027 : constant Version_32 := 16#08AB6B2C#;
26039 u00028 : constant Version_32 := 16#3FA37670#;
26040 u00029 : constant Version_32 := 16#476457A0#;
26041 u00030 : constant Version_32 := 16#731E1B6E#;
26042 u00031 : constant Version_32 := 16#23C2E789#;
26043 u00032 : constant Version_32 := 16#0F1BD6A1#;
26044 u00033 : constant Version_32 := 16#7C25DE96#;
26045 u00034 : constant Version_32 := 16#39ADFFA2#;
26046 u00035 : constant Version_32 := 16#571DE3E7#;
26047 u00036 : constant Version_32 := 16#5EB646AB#;
26048 u00037 : constant Version_32 := 16#4249379B#;
26049 u00038 : constant Version_32 := 16#0357E00A#;
26050 u00039 : constant Version_32 := 16#3784FB72#;
26051 u00040 : constant Version_32 := 16#2E723019#;
26052 u00041 : constant Version_32 := 16#623358EA#;
26053 u00042 : constant Version_32 := 16#107F9465#;
26054 u00043 : constant Version_32 := 16#6843F68A#;
26055 u00044 : constant Version_32 := 16#63305874#;
26056 u00045 : constant Version_32 := 16#31E56CE1#;
26057 u00046 : constant Version_32 := 16#02917970#;
26058 u00047 : constant Version_32 := 16#6CCBA70E#;
26059 u00048 : constant Version_32 := 16#41CD4204#;
26060 u00049 : constant Version_32 := 16#572E3F58#;
26061 u00050 : constant Version_32 := 16#20729FF5#;
26062 u00051 : constant Version_32 := 16#1D4F93E8#;
26063 u00052 : constant Version_32 := 16#30B2EC3D#;
26064 u00053 : constant Version_32 := 16#34054F96#;
26065 u00054 : constant Version_32 := 16#5A199860#;
26066 u00055 : constant Version_32 := 16#0E7F912B#;
26067 u00056 : constant Version_32 := 16#5760634A#;
26068 u00057 : constant Version_32 := 16#5D851835#;
26070 -- The following Export pragmas export the version numbers
26071 -- with symbolic names ending in B (for body) or S
26072 -- (for spec) so that they can be located in a link. The
26073 -- information provided here is sufficient to track down
26074 -- the exact versions of units used in a given build.
26076 pragma Export (C, u00001, "helloB");
26077 pragma Export (C, u00002, "system__standard_libraryB");
26078 pragma Export (C, u00003, "system__standard_libraryS");
26079 pragma Export (C, u00004, "adaS");
26080 pragma Export (C, u00005, "ada__text_ioB");
26081 pragma Export (C, u00006, "ada__text_ioS");
26082 pragma Export (C, u00007, "ada__exceptionsB");
26083 pragma Export (C, u00008, "ada__exceptionsS");
26084 pragma Export (C, u00009, "gnatS");
26085 pragma Export (C, u00010, "gnat__heap_sort_aB");
26086 pragma Export (C, u00011, "gnat__heap_sort_aS");
26087 pragma Export (C, u00012, "systemS");
26088 pragma Export (C, u00013, "system__exception_tableB");
26089 pragma Export (C, u00014, "system__exception_tableS");
26090 pragma Export (C, u00015, "gnat__htableB");
26091 pragma Export (C, u00016, "gnat__htableS");
26092 pragma Export (C, u00017, "system__exceptionsS");
26093 pragma Export (C, u00018, "system__machine_state_operationsB");
26094 pragma Export (C, u00019, "system__machine_state_operationsS");
26095 pragma Export (C, u00020, "system__machine_codeS");
26096 pragma Export (C, u00021, "system__storage_elementsB");
26097 pragma Export (C, u00022, "system__storage_elementsS");
26098 pragma Export (C, u00023, "system__secondary_stackB");
26099 pragma Export (C, u00024, "system__secondary_stackS");
26100 pragma Export (C, u00025, "system__parametersB");
26101 pragma Export (C, u00026, "system__parametersS");
26102 pragma Export (C, u00027, "system__soft_linksB");
26103 pragma Export (C, u00028, "system__soft_linksS");
26104 pragma Export (C, u00029, "system__stack_checkingB");
26105 pragma Export (C, u00030, "system__stack_checkingS");
26106 pragma Export (C, u00031, "system__tracebackB");
26107 pragma Export (C, u00032, "system__tracebackS");
26108 pragma Export (C, u00033, "ada__streamsS");
26109 pragma Export (C, u00034, "ada__tagsB");
26110 pragma Export (C, u00035, "ada__tagsS");
26111 pragma Export (C, u00036, "system__string_opsB");
26112 pragma Export (C, u00037, "system__string_opsS");
26113 pragma Export (C, u00038, "interfacesS");
26114 pragma Export (C, u00039, "interfaces__c_streamsB");
26115 pragma Export (C, u00040, "interfaces__c_streamsS");
26116 pragma Export (C, u00041, "system__file_ioB");
26117 pragma Export (C, u00042, "system__file_ioS");
26118 pragma Export (C, u00043, "ada__finalizationB");
26119 pragma Export (C, u00044, "ada__finalizationS");
26120 pragma Export (C, u00045, "system__finalization_rootB");
26121 pragma Export (C, u00046, "system__finalization_rootS");
26122 pragma Export (C, u00047, "system__finalization_implementationB");
26123 pragma Export (C, u00048, "system__finalization_implementationS");
26124 pragma Export (C, u00049, "system__string_ops_concat_3B");
26125 pragma Export (C, u00050, "system__string_ops_concat_3S");
26126 pragma Export (C, u00051, "system__stream_attributesB");
26127 pragma Export (C, u00052, "system__stream_attributesS");
26128 pragma Export (C, u00053, "ada__io_exceptionsS");
26129 pragma Export (C, u00054, "system__unsigned_typesS");
26130 pragma Export (C, u00055, "system__file_control_blockS");
26131 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26132 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26134 -- BEGIN ELABORATION ORDER
26137 -- gnat.heap_sort_a (spec)
26138 -- gnat.heap_sort_a (body)
26139 -- gnat.htable (spec)
26140 -- gnat.htable (body)
26141 -- interfaces (spec)
26143 -- system.machine_code (spec)
26144 -- system.parameters (spec)
26145 -- system.parameters (body)
26146 -- interfaces.c_streams (spec)
26147 -- interfaces.c_streams (body)
26148 -- system.standard_library (spec)
26149 -- ada.exceptions (spec)
26150 -- system.exception_table (spec)
26151 -- system.exception_table (body)
26152 -- ada.io_exceptions (spec)
26153 -- system.exceptions (spec)
26154 -- system.storage_elements (spec)
26155 -- system.storage_elements (body)
26156 -- system.machine_state_operations (spec)
26157 -- system.machine_state_operations (body)
26158 -- system.secondary_stack (spec)
26159 -- system.stack_checking (spec)
26160 -- system.soft_links (spec)
26161 -- system.soft_links (body)
26162 -- system.stack_checking (body)
26163 -- system.secondary_stack (body)
26164 -- system.standard_library (body)
26165 -- system.string_ops (spec)
26166 -- system.string_ops (body)
26169 -- ada.streams (spec)
26170 -- system.finalization_root (spec)
26171 -- system.finalization_root (body)
26172 -- system.string_ops_concat_3 (spec)
26173 -- system.string_ops_concat_3 (body)
26174 -- system.traceback (spec)
26175 -- system.traceback (body)
26176 -- ada.exceptions (body)
26177 -- system.unsigned_types (spec)
26178 -- system.stream_attributes (spec)
26179 -- system.stream_attributes (body)
26180 -- system.finalization_implementation (spec)
26181 -- system.finalization_implementation (body)
26182 -- ada.finalization (spec)
26183 -- ada.finalization (body)
26184 -- ada.finalization.list_controller (spec)
26185 -- ada.finalization.list_controller (body)
26186 -- system.file_control_block (spec)
26187 -- system.file_io (spec)
26188 -- system.file_io (body)
26189 -- ada.text_io (spec)
26190 -- ada.text_io (body)
26192 -- END ELABORATION ORDER
26196 -- The following source file name pragmas allow the generated file
26197 -- names to be unique for different main programs. They are needed
26198 -- since the package name will always be Ada_Main.
26200 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26201 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26203 -- Generated package body for Ada_Main starts here
26205 package body ada_main is
26207 -- The actual finalization is performed by calling the
26208 -- library routine in System.Standard_Library.Adafinal
26210 procedure Do_Finalize;
26211 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26218 procedure adainit is
26220 -- These booleans are set to True once the associated unit has
26221 -- been elaborated. It is also used to avoid elaborating the
26222 -- same unit twice.
26225 pragma Import (Ada, E040, "interfaces__c_streams_E");
26228 pragma Import (Ada, E008, "ada__exceptions_E");
26231 pragma Import (Ada, E014, "system__exception_table_E");
26234 pragma Import (Ada, E053, "ada__io_exceptions_E");
26237 pragma Import (Ada, E017, "system__exceptions_E");
26240 pragma Import (Ada, E024, "system__secondary_stack_E");
26243 pragma Import (Ada, E030, "system__stack_checking_E");
26246 pragma Import (Ada, E028, "system__soft_links_E");
26249 pragma Import (Ada, E035, "ada__tags_E");
26252 pragma Import (Ada, E033, "ada__streams_E");
26255 pragma Import (Ada, E046, "system__finalization_root_E");
26258 pragma Import (Ada, E048, "system__finalization_implementation_E");
26261 pragma Import (Ada, E044, "ada__finalization_E");
26264 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26267 pragma Import (Ada, E055, "system__file_control_block_E");
26270 pragma Import (Ada, E042, "system__file_io_E");
26273 pragma Import (Ada, E006, "ada__text_io_E");
26275 -- Set_Globals is a library routine that stores away the
26276 -- value of the indicated set of global values in global
26277 -- variables within the library.
26279 procedure Set_Globals
26280 (Main_Priority : Integer;
26281 Time_Slice_Value : Integer;
26282 WC_Encoding : Character;
26283 Locking_Policy : Character;
26284 Queuing_Policy : Character;
26285 Task_Dispatching_Policy : Character;
26286 Adafinal : System.Address;
26287 Unreserve_All_Interrupts : Integer;
26288 Exception_Tracebacks : Integer);
26289 @findex __gnat_set_globals
26290 pragma Import (C, Set_Globals, "__gnat_set_globals");
26292 -- SDP_Table_Build is a library routine used to build the
26293 -- exception tables. See unit Ada.Exceptions in files
26294 -- a-except.ads/adb for full details of how zero cost
26295 -- exception handling works. This procedure, the call to
26296 -- it, and the two following tables are all omitted if the
26297 -- build is in longjmp/setjmp exception mode.
26299 @findex SDP_Table_Build
26300 @findex Zero Cost Exceptions
26301 procedure SDP_Table_Build
26302 (SDP_Addresses : System.Address;
26303 SDP_Count : Natural;
26304 Elab_Addresses : System.Address;
26305 Elab_Addr_Count : Natural);
26306 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26308 -- Table of Unit_Exception_Table addresses. Used for zero
26309 -- cost exception handling to build the top level table.
26311 ST : aliased constant array (1 .. 23) of System.Address := (
26313 Ada.Text_Io'UET_Address,
26314 Ada.Exceptions'UET_Address,
26315 Gnat.Heap_Sort_A'UET_Address,
26316 System.Exception_Table'UET_Address,
26317 System.Machine_State_Operations'UET_Address,
26318 System.Secondary_Stack'UET_Address,
26319 System.Parameters'UET_Address,
26320 System.Soft_Links'UET_Address,
26321 System.Stack_Checking'UET_Address,
26322 System.Traceback'UET_Address,
26323 Ada.Streams'UET_Address,
26324 Ada.Tags'UET_Address,
26325 System.String_Ops'UET_Address,
26326 Interfaces.C_Streams'UET_Address,
26327 System.File_Io'UET_Address,
26328 Ada.Finalization'UET_Address,
26329 System.Finalization_Root'UET_Address,
26330 System.Finalization_Implementation'UET_Address,
26331 System.String_Ops_Concat_3'UET_Address,
26332 System.Stream_Attributes'UET_Address,
26333 System.File_Control_Block'UET_Address,
26334 Ada.Finalization.List_Controller'UET_Address);
26336 -- Table of addresses of elaboration routines. Used for
26337 -- zero cost exception handling to make sure these
26338 -- addresses are included in the top level procedure
26341 EA : aliased constant array (1 .. 23) of System.Address := (
26342 adainit'Code_Address,
26343 Do_Finalize'Code_Address,
26344 Ada.Exceptions'Elab_Spec'Address,
26345 System.Exceptions'Elab_Spec'Address,
26346 Interfaces.C_Streams'Elab_Spec'Address,
26347 System.Exception_Table'Elab_Body'Address,
26348 Ada.Io_Exceptions'Elab_Spec'Address,
26349 System.Stack_Checking'Elab_Spec'Address,
26350 System.Soft_Links'Elab_Body'Address,
26351 System.Secondary_Stack'Elab_Body'Address,
26352 Ada.Tags'Elab_Spec'Address,
26353 Ada.Tags'Elab_Body'Address,
26354 Ada.Streams'Elab_Spec'Address,
26355 System.Finalization_Root'Elab_Spec'Address,
26356 Ada.Exceptions'Elab_Body'Address,
26357 System.Finalization_Implementation'Elab_Spec'Address,
26358 System.Finalization_Implementation'Elab_Body'Address,
26359 Ada.Finalization'Elab_Spec'Address,
26360 Ada.Finalization.List_Controller'Elab_Spec'Address,
26361 System.File_Control_Block'Elab_Spec'Address,
26362 System.File_Io'Elab_Body'Address,
26363 Ada.Text_Io'Elab_Spec'Address,
26364 Ada.Text_Io'Elab_Body'Address);
26366 -- Start of processing for adainit
26370 -- Call SDP_Table_Build to build the top level procedure
26371 -- table for zero cost exception handling (omitted in
26372 -- longjmp/setjmp mode).
26374 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
26376 -- Call Set_Globals to record various information for
26377 -- this partition. The values are derived by the binder
26378 -- from information stored in the ali files by the compiler.
26380 @findex __gnat_set_globals
26382 (Main_Priority => -1,
26383 -- Priority of main program, -1 if no pragma Priority used
26385 Time_Slice_Value => -1,
26386 -- Time slice from Time_Slice pragma, -1 if none used
26388 WC_Encoding => 'b',
26389 -- Wide_Character encoding used, default is brackets
26391 Locking_Policy => ' ',
26392 -- Locking_Policy used, default of space means not
26393 -- specified, otherwise it is the first character of
26394 -- the policy name.
26396 Queuing_Policy => ' ',
26397 -- Queuing_Policy used, default of space means not
26398 -- specified, otherwise it is the first character of
26399 -- the policy name.
26401 Task_Dispatching_Policy => ' ',
26402 -- Task_Dispatching_Policy used, default of space means
26403 -- not specified, otherwise first character of the
26406 Adafinal => System.Null_Address,
26407 -- Address of Adafinal routine, not used anymore
26409 Unreserve_All_Interrupts => 0,
26410 -- Set true if pragma Unreserve_All_Interrupts was used
26412 Exception_Tracebacks => 0);
26413 -- Indicates if exception tracebacks are enabled
26415 Elab_Final_Code := 1;
26417 -- Now we have the elaboration calls for all units in the partition.
26418 -- The Elab_Spec and Elab_Body attributes generate references to the
26419 -- implicit elaboration procedures generated by the compiler for
26420 -- each unit that requires elaboration.
26423 Interfaces.C_Streams'Elab_Spec;
26427 Ada.Exceptions'Elab_Spec;
26430 System.Exception_Table'Elab_Body;
26434 Ada.Io_Exceptions'Elab_Spec;
26438 System.Exceptions'Elab_Spec;
26442 System.Stack_Checking'Elab_Spec;
26445 System.Soft_Links'Elab_Body;
26450 System.Secondary_Stack'Elab_Body;
26454 Ada.Tags'Elab_Spec;
26457 Ada.Tags'Elab_Body;
26461 Ada.Streams'Elab_Spec;
26465 System.Finalization_Root'Elab_Spec;
26469 Ada.Exceptions'Elab_Body;
26473 System.Finalization_Implementation'Elab_Spec;
26476 System.Finalization_Implementation'Elab_Body;
26480 Ada.Finalization'Elab_Spec;
26484 Ada.Finalization.List_Controller'Elab_Spec;
26488 System.File_Control_Block'Elab_Spec;
26492 System.File_Io'Elab_Body;
26496 Ada.Text_Io'Elab_Spec;
26499 Ada.Text_Io'Elab_Body;
26503 Elab_Final_Code := 0;
26511 procedure adafinal is
26520 -- main is actually a function, as in the ANSI C standard,
26521 -- defined to return the exit status. The three parameters
26522 -- are the argument count, argument values and environment
26525 @findex Main Program
26528 argv : System.Address;
26529 envp : System.Address)
26532 -- The initialize routine performs low level system
26533 -- initialization using a standard library routine which
26534 -- sets up signal handling and performs any other
26535 -- required setup. The routine can be found in file
26538 @findex __gnat_initialize
26539 procedure initialize;
26540 pragma Import (C, initialize, "__gnat_initialize");
26542 -- The finalize routine performs low level system
26543 -- finalization using a standard library routine. The
26544 -- routine is found in file a-final.c and in the standard
26545 -- distribution is a dummy routine that does nothing, so
26546 -- really this is a hook for special user finalization.
26548 @findex __gnat_finalize
26549 procedure finalize;
26550 pragma Import (C, finalize, "__gnat_finalize");
26552 -- We get to the main program of the partition by using
26553 -- pragma Import because if we try to with the unit and
26554 -- call it Ada style, then not only do we waste time
26555 -- recompiling it, but also, we don't really know the right
26556 -- switches (e.g.@: identifier character set) to be used
26559 procedure Ada_Main_Program;
26560 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
26562 -- Start of processing for main
26565 -- Save global variables
26571 -- Call low level system initialization
26575 -- Call our generated Ada initialization routine
26579 -- This is the point at which we want the debugger to get
26584 -- Now we call the main program of the partition
26588 -- Perform Ada finalization
26592 -- Perform low level system finalization
26596 -- Return the proper exit status
26597 return (gnat_exit_status);
26600 -- This section is entirely comments, so it has no effect on the
26601 -- compilation of the Ada_Main package. It provides the list of
26602 -- object files and linker options, as well as some standard
26603 -- libraries needed for the link. The gnatlink utility parses
26604 -- this b~hello.adb file to read these comment lines to generate
26605 -- the appropriate command line arguments for the call to the
26606 -- system linker. The BEGIN/END lines are used for sentinels for
26607 -- this parsing operation.
26609 -- The exact file names will of course depend on the environment,
26610 -- host/target and location of files on the host system.
26612 @findex Object file list
26613 -- BEGIN Object file/option list
26616 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
26617 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
26618 -- END Object file/option list
26624 The Ada code in the above example is exactly what is generated by the
26625 binder. We have added comments to more clearly indicate the function
26626 of each part of the generated @code{Ada_Main} package.
26628 The code is standard Ada in all respects, and can be processed by any
26629 tools that handle Ada. In particular, it is possible to use the debugger
26630 in Ada mode to debug the generated @code{Ada_Main} package. For example,
26631 suppose that for reasons that you do not understand, your program is crashing
26632 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
26633 you can place a breakpoint on the call:
26635 @smallexample @c ada
26636 Ada.Text_Io'Elab_Body;
26640 and trace the elaboration routine for this package to find out where
26641 the problem might be (more usually of course you would be debugging
26642 elaboration code in your own application).
26644 @node Elaboration Order Handling in GNAT
26645 @appendix Elaboration Order Handling in GNAT
26646 @cindex Order of elaboration
26647 @cindex Elaboration control
26650 * Elaboration Code::
26651 * Checking the Elaboration Order::
26652 * Controlling the Elaboration Order::
26653 * Controlling Elaboration in GNAT - Internal Calls::
26654 * Controlling Elaboration in GNAT - External Calls::
26655 * Default Behavior in GNAT - Ensuring Safety::
26656 * Treatment of Pragma Elaborate::
26657 * Elaboration Issues for Library Tasks::
26658 * Mixing Elaboration Models::
26659 * What to Do If the Default Elaboration Behavior Fails::
26660 * Elaboration for Access-to-Subprogram Values::
26661 * Summary of Procedures for Elaboration Control::
26662 * Other Elaboration Order Considerations::
26666 This chapter describes the handling of elaboration code in Ada and
26667 in GNAT, and discusses how the order of elaboration of program units can
26668 be controlled in GNAT, either automatically or with explicit programming
26671 @node Elaboration Code
26672 @section Elaboration Code
26675 Ada provides rather general mechanisms for executing code at elaboration
26676 time, that is to say before the main program starts executing. Such code arises
26680 @item Initializers for variables.
26681 Variables declared at the library level, in package specs or bodies, can
26682 require initialization that is performed at elaboration time, as in:
26683 @smallexample @c ada
26685 Sqrt_Half : Float := Sqrt (0.5);
26689 @item Package initialization code
26690 Code in a @code{BEGIN-END} section at the outer level of a package body is
26691 executed as part of the package body elaboration code.
26693 @item Library level task allocators
26694 Tasks that are declared using task allocators at the library level
26695 start executing immediately and hence can execute at elaboration time.
26699 Subprogram calls are possible in any of these contexts, which means that
26700 any arbitrary part of the program may be executed as part of the elaboration
26701 code. It is even possible to write a program which does all its work at
26702 elaboration time, with a null main program, although stylistically this
26703 would usually be considered an inappropriate way to structure
26706 An important concern arises in the context of elaboration code:
26707 we have to be sure that it is executed in an appropriate order. What we
26708 have is a series of elaboration code sections, potentially one section
26709 for each unit in the program. It is important that these execute
26710 in the correct order. Correctness here means that, taking the above
26711 example of the declaration of @code{Sqrt_Half},
26712 if some other piece of
26713 elaboration code references @code{Sqrt_Half},
26714 then it must run after the
26715 section of elaboration code that contains the declaration of
26718 There would never be any order of elaboration problem if we made a rule
26719 that whenever you @code{with} a unit, you must elaborate both the spec and body
26720 of that unit before elaborating the unit doing the @code{with}'ing:
26722 @smallexample @c ada
26726 package Unit_2 is @dots{}
26732 would require that both the body and spec of @code{Unit_1} be elaborated
26733 before the spec of @code{Unit_2}. However, a rule like that would be far too
26734 restrictive. In particular, it would make it impossible to have routines
26735 in separate packages that were mutually recursive.
26737 You might think that a clever enough compiler could look at the actual
26738 elaboration code and determine an appropriate correct order of elaboration,
26739 but in the general case, this is not possible. Consider the following
26742 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
26744 the variable @code{Sqrt_1}, which is declared in the elaboration code
26745 of the body of @code{Unit_1}:
26747 @smallexample @c ada
26749 Sqrt_1 : Float := Sqrt (0.1);
26754 The elaboration code of the body of @code{Unit_1} also contains:
26756 @smallexample @c ada
26759 if expression_1 = 1 then
26760 Q := Unit_2.Func_2;
26767 @code{Unit_2} is exactly parallel,
26768 it has a procedure @code{Func_2} that references
26769 the variable @code{Sqrt_2}, which is declared in the elaboration code of
26770 the body @code{Unit_2}:
26772 @smallexample @c ada
26774 Sqrt_2 : Float := Sqrt (0.1);
26779 The elaboration code of the body of @code{Unit_2} also contains:
26781 @smallexample @c ada
26784 if expression_2 = 2 then
26785 Q := Unit_1.Func_1;
26792 Now the question is, which of the following orders of elaboration is
26817 If you carefully analyze the flow here, you will see that you cannot tell
26818 at compile time the answer to this question.
26819 If @code{expression_1} is not equal to 1,
26820 and @code{expression_2} is not equal to 2,
26821 then either order is acceptable, because neither of the function calls is
26822 executed. If both tests evaluate to true, then neither order is acceptable
26823 and in fact there is no correct order.
26825 If one of the two expressions is true, and the other is false, then one
26826 of the above orders is correct, and the other is incorrect. For example,
26827 if @code{expression_1} /= 1 and @code{expression_2} = 2,
26828 then the call to @code{Func_1}
26829 will occur, but not the call to @code{Func_2.}
26830 This means that it is essential
26831 to elaborate the body of @code{Unit_1} before
26832 the body of @code{Unit_2}, so the first
26833 order of elaboration is correct and the second is wrong.
26835 By making @code{expression_1} and @code{expression_2}
26836 depend on input data, or perhaps
26837 the time of day, we can make it impossible for the compiler or binder
26838 to figure out which of these expressions will be true, and hence it
26839 is impossible to guarantee a safe order of elaboration at run time.
26841 @node Checking the Elaboration Order
26842 @section Checking the Elaboration Order
26845 In some languages that involve the same kind of elaboration problems,
26846 e.g.@: Java and C++, the programmer is expected to worry about these
26847 ordering problems himself, and it is common to
26848 write a program in which an incorrect elaboration order gives
26849 surprising results, because it references variables before they
26851 Ada is designed to be a safe language, and a programmer-beware approach is
26852 clearly not sufficient. Consequently, the language provides three lines
26856 @item Standard rules
26857 Some standard rules restrict the possible choice of elaboration
26858 order. In particular, if you @code{with} a unit, then its spec is always
26859 elaborated before the unit doing the @code{with}. Similarly, a parent
26860 spec is always elaborated before the child spec, and finally
26861 a spec is always elaborated before its corresponding body.
26863 @item Dynamic elaboration checks
26864 @cindex Elaboration checks
26865 @cindex Checks, elaboration
26866 Dynamic checks are made at run time, so that if some entity is accessed
26867 before it is elaborated (typically by means of a subprogram call)
26868 then the exception (@code{Program_Error}) is raised.
26870 @item Elaboration control
26871 Facilities are provided for the programmer to specify the desired order
26875 Let's look at these facilities in more detail. First, the rules for
26876 dynamic checking. One possible rule would be simply to say that the
26877 exception is raised if you access a variable which has not yet been
26878 elaborated. The trouble with this approach is that it could require
26879 expensive checks on every variable reference. Instead Ada has two
26880 rules which are a little more restrictive, but easier to check, and
26884 @item Restrictions on calls
26885 A subprogram can only be called at elaboration time if its body
26886 has been elaborated. The rules for elaboration given above guarantee
26887 that the spec of the subprogram has been elaborated before the
26888 call, but not the body. If this rule is violated, then the
26889 exception @code{Program_Error} is raised.
26891 @item Restrictions on instantiations
26892 A generic unit can only be instantiated if the body of the generic
26893 unit has been elaborated. Again, the rules for elaboration given above
26894 guarantee that the spec of the generic unit has been elaborated
26895 before the instantiation, but not the body. If this rule is
26896 violated, then the exception @code{Program_Error} is raised.
26900 The idea is that if the body has been elaborated, then any variables
26901 it references must have been elaborated; by checking for the body being
26902 elaborated we guarantee that none of its references causes any
26903 trouble. As we noted above, this is a little too restrictive, because a
26904 subprogram that has no non-local references in its body may in fact be safe
26905 to call. However, it really would be unsafe to rely on this, because
26906 it would mean that the caller was aware of details of the implementation
26907 in the body. This goes against the basic tenets of Ada.
26909 A plausible implementation can be described as follows.
26910 A Boolean variable is associated with each subprogram
26911 and each generic unit. This variable is initialized to False, and is set to
26912 True at the point body is elaborated. Every call or instantiation checks the
26913 variable, and raises @code{Program_Error} if the variable is False.
26915 Note that one might think that it would be good enough to have one Boolean
26916 variable for each package, but that would not deal with cases of trying
26917 to call a body in the same package as the call
26918 that has not been elaborated yet.
26919 Of course a compiler may be able to do enough analysis to optimize away
26920 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
26921 does such optimizations, but still the easiest conceptual model is to
26922 think of there being one variable per subprogram.
26924 @node Controlling the Elaboration Order
26925 @section Controlling the Elaboration Order
26928 In the previous section we discussed the rules in Ada which ensure
26929 that @code{Program_Error} is raised if an incorrect elaboration order is
26930 chosen. This prevents erroneous executions, but we need mechanisms to
26931 specify a correct execution and avoid the exception altogether.
26932 To achieve this, Ada provides a number of features for controlling
26933 the order of elaboration. We discuss these features in this section.
26935 First, there are several ways of indicating to the compiler that a given
26936 unit has no elaboration problems:
26939 @item packages that do not require a body
26940 A library package that does not require a body does not permit
26941 a body (this rule was introduced in Ada 95).
26942 Thus if we have a such a package, as in:
26944 @smallexample @c ada
26947 package Definitions is
26949 type m is new integer;
26951 type a is array (1 .. 10) of m;
26952 type b is array (1 .. 20) of m;
26960 A package that @code{with}'s @code{Definitions} may safely instantiate
26961 @code{Definitions.Subp} because the compiler can determine that there
26962 definitely is no package body to worry about in this case
26965 @cindex pragma Pure
26967 Places sufficient restrictions on a unit to guarantee that
26968 no call to any subprogram in the unit can result in an
26969 elaboration problem. This means that the compiler does not need
26970 to worry about the point of elaboration of such units, and in
26971 particular, does not need to check any calls to any subprograms
26974 @item pragma Preelaborate
26975 @findex Preelaborate
26976 @cindex pragma Preelaborate
26977 This pragma places slightly less stringent restrictions on a unit than
26979 but these restrictions are still sufficient to ensure that there
26980 are no elaboration problems with any calls to the unit.
26982 @item pragma Elaborate_Body
26983 @findex Elaborate_Body
26984 @cindex pragma Elaborate_Body
26985 This pragma requires that the body of a unit be elaborated immediately
26986 after its spec. Suppose a unit @code{A} has such a pragma,
26987 and unit @code{B} does
26988 a @code{with} of unit @code{A}. Recall that the standard rules require
26989 the spec of unit @code{A}
26990 to be elaborated before the @code{with}'ing unit; given the pragma in
26991 @code{A}, we also know that the body of @code{A}
26992 will be elaborated before @code{B}, so
26993 that calls to @code{A} are safe and do not need a check.
26998 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27000 @code{Elaborate_Body} does not guarantee that the program is
27001 free of elaboration problems, because it may not be possible
27002 to satisfy the requested elaboration order.
27003 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27005 marks @code{Unit_1} as @code{Elaborate_Body},
27006 and not @code{Unit_2,} then the order of
27007 elaboration will be:
27019 Now that means that the call to @code{Func_1} in @code{Unit_2}
27020 need not be checked,
27021 it must be safe. But the call to @code{Func_2} in
27022 @code{Unit_1} may still fail if
27023 @code{Expression_1} is equal to 1,
27024 and the programmer must still take
27025 responsibility for this not being the case.
27027 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27028 eliminated, except for calls entirely within a body, which are
27029 in any case fully under programmer control. However, using the pragma
27030 everywhere is not always possible.
27031 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27032 we marked both of them as having pragma @code{Elaborate_Body}, then
27033 clearly there would be no possible elaboration order.
27035 The above pragmas allow a server to guarantee safe use by clients, and
27036 clearly this is the preferable approach. Consequently a good rule
27037 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27038 and if this is not possible,
27039 mark them as @code{Elaborate_Body} if possible.
27040 As we have seen, there are situations where neither of these
27041 three pragmas can be used.
27042 So we also provide methods for clients to control the
27043 order of elaboration of the servers on which they depend:
27046 @item pragma Elaborate (unit)
27048 @cindex pragma Elaborate
27049 This pragma is placed in the context clause, after a @code{with} clause,
27050 and it requires that the body of the named unit be elaborated before
27051 the unit in which the pragma occurs. The idea is to use this pragma
27052 if the current unit calls at elaboration time, directly or indirectly,
27053 some subprogram in the named unit.
27055 @item pragma Elaborate_All (unit)
27056 @findex Elaborate_All
27057 @cindex pragma Elaborate_All
27058 This is a stronger version of the Elaborate pragma. Consider the
27062 Unit A @code{with}'s unit B and calls B.Func in elab code
27063 Unit B @code{with}'s unit C, and B.Func calls C.Func
27067 Now if we put a pragma @code{Elaborate (B)}
27068 in unit @code{A}, this ensures that the
27069 body of @code{B} is elaborated before the call, but not the
27070 body of @code{C}, so
27071 the call to @code{C.Func} could still cause @code{Program_Error} to
27074 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27075 not only that the body of the named unit be elaborated before the
27076 unit doing the @code{with}, but also the bodies of all units that the
27077 named unit uses, following @code{with} links transitively. For example,
27078 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27080 not only that the body of @code{B} be elaborated before @code{A},
27082 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27086 We are now in a position to give a usage rule in Ada for avoiding
27087 elaboration problems, at least if dynamic dispatching and access to
27088 subprogram values are not used. We will handle these cases separately
27091 The rule is simple. If a unit has elaboration code that can directly or
27092 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27093 a generic package in a @code{with}'ed unit,
27094 then if the @code{with}'ed unit does not have
27095 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27096 a pragma @code{Elaborate_All}
27097 for the @code{with}'ed unit. By following this rule a client is
27098 assured that calls can be made without risk of an exception.
27100 For generic subprogram instantiations, the rule can be relaxed to
27101 require only a pragma @code{Elaborate} since elaborating the body
27102 of a subprogram cannot cause any transitive elaboration (we are
27103 not calling the subprogram in this case, just elaborating its
27106 If this rule is not followed, then a program may be in one of four
27110 @item No order exists
27111 No order of elaboration exists which follows the rules, taking into
27112 account any @code{Elaborate}, @code{Elaborate_All},
27113 or @code{Elaborate_Body} pragmas. In
27114 this case, an Ada compiler must diagnose the situation at bind
27115 time, and refuse to build an executable program.
27117 @item One or more orders exist, all incorrect
27118 One or more acceptable elaboration orders exist, and all of them
27119 generate an elaboration order problem. In this case, the binder
27120 can build an executable program, but @code{Program_Error} will be raised
27121 when the program is run.
27123 @item Several orders exist, some right, some incorrect
27124 One or more acceptable elaboration orders exists, and some of them
27125 work, and some do not. The programmer has not controlled
27126 the order of elaboration, so the binder may or may not pick one of
27127 the correct orders, and the program may or may not raise an
27128 exception when it is run. This is the worst case, because it means
27129 that the program may fail when moved to another compiler, or even
27130 another version of the same compiler.
27132 @item One or more orders exists, all correct
27133 One ore more acceptable elaboration orders exist, and all of them
27134 work. In this case the program runs successfully. This state of
27135 affairs can be guaranteed by following the rule we gave above, but
27136 may be true even if the rule is not followed.
27140 Note that one additional advantage of following our rules on the use
27141 of @code{Elaborate} and @code{Elaborate_All}
27142 is that the program continues to stay in the ideal (all orders OK) state
27143 even if maintenance
27144 changes some bodies of some units. Conversely, if a program that does
27145 not follow this rule happens to be safe at some point, this state of affairs
27146 may deteriorate silently as a result of maintenance changes.
27148 You may have noticed that the above discussion did not mention
27149 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27150 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27151 code in the body makes calls to some other unit, so it is still necessary
27152 to use @code{Elaborate_All} on such units.
27154 @node Controlling Elaboration in GNAT - Internal Calls
27155 @section Controlling Elaboration in GNAT - Internal Calls
27158 In the case of internal calls, i.e., calls within a single package, the
27159 programmer has full control over the order of elaboration, and it is up
27160 to the programmer to elaborate declarations in an appropriate order. For
27163 @smallexample @c ada
27166 function One return Float;
27170 function One return Float is
27179 will obviously raise @code{Program_Error} at run time, because function
27180 One will be called before its body is elaborated. In this case GNAT will
27181 generate a warning that the call will raise @code{Program_Error}:
27187 2. function One return Float;
27189 4. Q : Float := One;
27191 >>> warning: cannot call "One" before body is elaborated
27192 >>> warning: Program_Error will be raised at run time
27195 6. function One return Float is
27208 Note that in this particular case, it is likely that the call is safe, because
27209 the function @code{One} does not access any global variables.
27210 Nevertheless in Ada, we do not want the validity of the check to depend on
27211 the contents of the body (think about the separate compilation case), so this
27212 is still wrong, as we discussed in the previous sections.
27214 The error is easily corrected by rearranging the declarations so that the
27215 body of @code{One} appears before the declaration containing the call
27216 (note that in Ada 95 and Ada 2005,
27217 declarations can appear in any order, so there is no restriction that
27218 would prevent this reordering, and if we write:
27220 @smallexample @c ada
27223 function One return Float;
27225 function One return Float is
27236 then all is well, no warning is generated, and no
27237 @code{Program_Error} exception
27239 Things are more complicated when a chain of subprograms is executed:
27241 @smallexample @c ada
27244 function A return Integer;
27245 function B return Integer;
27246 function C return Integer;
27248 function B return Integer is begin return A; end;
27249 function C return Integer is begin return B; end;
27253 function A return Integer is begin return 1; end;
27259 Now the call to @code{C}
27260 at elaboration time in the declaration of @code{X} is correct, because
27261 the body of @code{C} is already elaborated,
27262 and the call to @code{B} within the body of
27263 @code{C} is correct, but the call
27264 to @code{A} within the body of @code{B} is incorrect, because the body
27265 of @code{A} has not been elaborated, so @code{Program_Error}
27266 will be raised on the call to @code{A}.
27267 In this case GNAT will generate a
27268 warning that @code{Program_Error} may be
27269 raised at the point of the call. Let's look at the warning:
27275 2. function A return Integer;
27276 3. function B return Integer;
27277 4. function C return Integer;
27279 6. function B return Integer is begin return A; end;
27281 >>> warning: call to "A" before body is elaborated may
27282 raise Program_Error
27283 >>> warning: "B" called at line 7
27284 >>> warning: "C" called at line 9
27286 7. function C return Integer is begin return B; end;
27288 9. X : Integer := C;
27290 11. function A return Integer is begin return 1; end;
27300 Note that the message here says ``may raise'', instead of the direct case,
27301 where the message says ``will be raised''. That's because whether
27303 actually called depends in general on run-time flow of control.
27304 For example, if the body of @code{B} said
27306 @smallexample @c ada
27309 function B return Integer is
27311 if some-condition-depending-on-input-data then
27322 then we could not know until run time whether the incorrect call to A would
27323 actually occur, so @code{Program_Error} might
27324 or might not be raised. It is possible for a compiler to
27325 do a better job of analyzing bodies, to
27326 determine whether or not @code{Program_Error}
27327 might be raised, but it certainly
27328 couldn't do a perfect job (that would require solving the halting problem
27329 and is provably impossible), and because this is a warning anyway, it does
27330 not seem worth the effort to do the analysis. Cases in which it
27331 would be relevant are rare.
27333 In practice, warnings of either of the forms given
27334 above will usually correspond to
27335 real errors, and should be examined carefully and eliminated.
27336 In the rare case where a warning is bogus, it can be suppressed by any of
27337 the following methods:
27341 Compile with the @option{-gnatws} switch set
27344 Suppress @code{Elaboration_Check} for the called subprogram
27347 Use pragma @code{Warnings_Off} to turn warnings off for the call
27351 For the internal elaboration check case,
27352 GNAT by default generates the
27353 necessary run-time checks to ensure
27354 that @code{Program_Error} is raised if any
27355 call fails an elaboration check. Of course this can only happen if a
27356 warning has been issued as described above. The use of pragma
27357 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
27358 some of these checks, meaning that it may be possible (but is not
27359 guaranteed) for a program to be able to call a subprogram whose body
27360 is not yet elaborated, without raising a @code{Program_Error} exception.
27362 @node Controlling Elaboration in GNAT - External Calls
27363 @section Controlling Elaboration in GNAT - External Calls
27366 The previous section discussed the case in which the execution of a
27367 particular thread of elaboration code occurred entirely within a
27368 single unit. This is the easy case to handle, because a programmer
27369 has direct and total control over the order of elaboration, and
27370 furthermore, checks need only be generated in cases which are rare
27371 and which the compiler can easily detect.
27372 The situation is more complex when separate compilation is taken into account.
27373 Consider the following:
27375 @smallexample @c ada
27379 function Sqrt (Arg : Float) return Float;
27382 package body Math is
27383 function Sqrt (Arg : Float) return Float is
27392 X : Float := Math.Sqrt (0.5);
27405 where @code{Main} is the main program. When this program is executed, the
27406 elaboration code must first be executed, and one of the jobs of the
27407 binder is to determine the order in which the units of a program are
27408 to be elaborated. In this case we have four units: the spec and body
27410 the spec of @code{Stuff} and the body of @code{Main}).
27411 In what order should the four separate sections of elaboration code
27414 There are some restrictions in the order of elaboration that the binder
27415 can choose. In particular, if unit U has a @code{with}
27416 for a package @code{X}, then you
27417 are assured that the spec of @code{X}
27418 is elaborated before U , but you are
27419 not assured that the body of @code{X}
27420 is elaborated before U.
27421 This means that in the above case, the binder is allowed to choose the
27432 but that's not good, because now the call to @code{Math.Sqrt}
27433 that happens during
27434 the elaboration of the @code{Stuff}
27435 spec happens before the body of @code{Math.Sqrt} is
27436 elaborated, and hence causes @code{Program_Error} exception to be raised.
27437 At first glance, one might say that the binder is misbehaving, because
27438 obviously you want to elaborate the body of something you @code{with}
27440 that is not a general rule that can be followed in all cases. Consider
27442 @smallexample @c ada
27445 package X is @dots{}
27447 package Y is @dots{}
27450 package body Y is @dots{}
27453 package body X is @dots{}
27459 This is a common arrangement, and, apart from the order of elaboration
27460 problems that might arise in connection with elaboration code, this works fine.
27461 A rule that says that you must first elaborate the body of anything you
27462 @code{with} cannot work in this case:
27463 the body of @code{X} @code{with}'s @code{Y},
27464 which means you would have to
27465 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
27467 you have to elaborate the body of @code{X} first, but @dots{} and we have a
27468 loop that cannot be broken.
27470 It is true that the binder can in many cases guess an order of elaboration
27471 that is unlikely to cause a @code{Program_Error}
27472 exception to be raised, and it tries to do so (in the
27473 above example of @code{Math/Stuff/Spec}, the GNAT binder will
27475 elaborate the body of @code{Math} right after its spec, so all will be well).
27477 However, a program that blindly relies on the binder to be helpful can
27478 get into trouble, as we discussed in the previous sections, so
27480 provides a number of facilities for assisting the programmer in
27481 developing programs that are robust with respect to elaboration order.
27483 @node Default Behavior in GNAT - Ensuring Safety
27484 @section Default Behavior in GNAT - Ensuring Safety
27487 The default behavior in GNAT ensures elaboration safety. In its
27488 default mode GNAT implements the
27489 rule we previously described as the right approach. Let's restate it:
27493 @emph{If a unit has elaboration code that can directly or indirectly make a
27494 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
27495 package in a @code{with}'ed unit, then if the @code{with}'ed unit
27496 does not have pragma @code{Pure} or
27497 @code{Preelaborate}, then the client should have an
27498 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
27500 @emph{In the case of instantiating a generic subprogram, it is always
27501 sufficient to have only an @code{Elaborate} pragma for the
27502 @code{with}'ed unit.}
27506 By following this rule a client is assured that calls and instantiations
27507 can be made without risk of an exception.
27509 In this mode GNAT traces all calls that are potentially made from
27510 elaboration code, and puts in any missing implicit @code{Elaborate}
27511 and @code{Elaborate_All} pragmas.
27512 The advantage of this approach is that no elaboration problems
27513 are possible if the binder can find an elaboration order that is
27514 consistent with these implicit @code{Elaborate} and
27515 @code{Elaborate_All} pragmas. The
27516 disadvantage of this approach is that no such order may exist.
27518 If the binder does not generate any diagnostics, then it means that it has
27519 found an elaboration order that is guaranteed to be safe. However, the binder
27520 may still be relying on implicitly generated @code{Elaborate} and
27521 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
27524 If it is important to guarantee portability, then the compilations should
27527 (warn on elaboration problems) switch. This will cause warning messages
27528 to be generated indicating the missing @code{Elaborate} and
27529 @code{Elaborate_All} pragmas.
27530 Consider the following source program:
27532 @smallexample @c ada
27537 m : integer := k.r;
27544 where it is clear that there
27545 should be a pragma @code{Elaborate_All}
27546 for unit @code{k}. An implicit pragma will be generated, and it is
27547 likely that the binder will be able to honor it. However, if you want
27548 to port this program to some other Ada compiler than GNAT.
27549 it is safer to include the pragma explicitly in the source. If this
27550 unit is compiled with the
27552 switch, then the compiler outputs a warning:
27559 3. m : integer := k.r;
27561 >>> warning: call to "r" may raise Program_Error
27562 >>> warning: missing pragma Elaborate_All for "k"
27570 and these warnings can be used as a guide for supplying manually
27571 the missing pragmas. It is usually a bad idea to use this warning
27572 option during development. That's because it will warn you when
27573 you need to put in a pragma, but cannot warn you when it is time
27574 to take it out. So the use of pragma @code{Elaborate_All} may lead to
27575 unnecessary dependencies and even false circularities.
27577 This default mode is more restrictive than the Ada Reference
27578 Manual, and it is possible to construct programs which will compile
27579 using the dynamic model described there, but will run into a
27580 circularity using the safer static model we have described.
27582 Of course any Ada compiler must be able to operate in a mode
27583 consistent with the requirements of the Ada Reference Manual,
27584 and in particular must have the capability of implementing the
27585 standard dynamic model of elaboration with run-time checks.
27587 In GNAT, this standard mode can be achieved either by the use of
27588 the @option{-gnatE} switch on the compiler (@command{gcc} or
27589 @command{gnatmake}) command, or by the use of the configuration pragma:
27591 @smallexample @c ada
27592 pragma Elaboration_Checks (RM);
27596 Either approach will cause the unit affected to be compiled using the
27597 standard dynamic run-time elaboration checks described in the Ada
27598 Reference Manual. The static model is generally preferable, since it
27599 is clearly safer to rely on compile and link time checks rather than
27600 run-time checks. However, in the case of legacy code, it may be
27601 difficult to meet the requirements of the static model. This
27602 issue is further discussed in
27603 @ref{What to Do If the Default Elaboration Behavior Fails}.
27605 Note that the static model provides a strict subset of the allowed
27606 behavior and programs of the Ada Reference Manual, so if you do
27607 adhere to the static model and no circularities exist,
27608 then you are assured that your program will
27609 work using the dynamic model, providing that you remove any
27610 pragma Elaborate statements from the source.
27612 @node Treatment of Pragma Elaborate
27613 @section Treatment of Pragma Elaborate
27614 @cindex Pragma Elaborate
27617 The use of @code{pragma Elaborate}
27618 should generally be avoided in Ada 95 and Ada 2005 programs,
27619 since there is no guarantee that transitive calls
27620 will be properly handled. Indeed at one point, this pragma was placed
27621 in Annex J (Obsolescent Features), on the grounds that it is never useful.
27623 Now that's a bit restrictive. In practice, the case in which
27624 @code{pragma Elaborate} is useful is when the caller knows that there
27625 are no transitive calls, or that the called unit contains all necessary
27626 transitive @code{pragma Elaborate} statements, and legacy code often
27627 contains such uses.
27629 Strictly speaking the static mode in GNAT should ignore such pragmas,
27630 since there is no assurance at compile time that the necessary safety
27631 conditions are met. In practice, this would cause GNAT to be incompatible
27632 with correctly written Ada 83 code that had all necessary
27633 @code{pragma Elaborate} statements in place. Consequently, we made the
27634 decision that GNAT in its default mode will believe that if it encounters
27635 a @code{pragma Elaborate} then the programmer knows what they are doing,
27636 and it will trust that no elaboration errors can occur.
27638 The result of this decision is two-fold. First to be safe using the
27639 static mode, you should remove all @code{pragma Elaborate} statements.
27640 Second, when fixing circularities in existing code, you can selectively
27641 use @code{pragma Elaborate} statements to convince the static mode of
27642 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
27645 When using the static mode with @option{-gnatwl}, any use of
27646 @code{pragma Elaborate} will generate a warning about possible
27649 @node Elaboration Issues for Library Tasks
27650 @section Elaboration Issues for Library Tasks
27651 @cindex Library tasks, elaboration issues
27652 @cindex Elaboration of library tasks
27655 In this section we examine special elaboration issues that arise for
27656 programs that declare library level tasks.
27658 Generally the model of execution of an Ada program is that all units are
27659 elaborated, and then execution of the program starts. However, the
27660 declaration of library tasks definitely does not fit this model. The
27661 reason for this is that library tasks start as soon as they are declared
27662 (more precisely, as soon as the statement part of the enclosing package
27663 body is reached), that is to say before elaboration
27664 of the program is complete. This means that if such a task calls a
27665 subprogram, or an entry in another task, the callee may or may not be
27666 elaborated yet, and in the standard
27667 Reference Manual model of dynamic elaboration checks, you can even
27668 get timing dependent Program_Error exceptions, since there can be
27669 a race between the elaboration code and the task code.
27671 The static model of elaboration in GNAT seeks to avoid all such
27672 dynamic behavior, by being conservative, and the conservative
27673 approach in this particular case is to assume that all the code
27674 in a task body is potentially executed at elaboration time if
27675 a task is declared at the library level.
27677 This can definitely result in unexpected circularities. Consider
27678 the following example
27680 @smallexample @c ada
27686 type My_Int is new Integer;
27688 function Ident (M : My_Int) return My_Int;
27692 package body Decls is
27693 task body Lib_Task is
27699 function Ident (M : My_Int) return My_Int is
27707 procedure Put_Val (Arg : Decls.My_Int);
27711 package body Utils is
27712 procedure Put_Val (Arg : Decls.My_Int) is
27714 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27721 Decls.Lib_Task.Start;
27726 If the above example is compiled in the default static elaboration
27727 mode, then a circularity occurs. The circularity comes from the call
27728 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
27729 this call occurs in elaboration code, we need an implicit pragma
27730 @code{Elaborate_All} for @code{Utils}. This means that not only must
27731 the spec and body of @code{Utils} be elaborated before the body
27732 of @code{Decls}, but also the spec and body of any unit that is
27733 @code{with'ed} by the body of @code{Utils} must also be elaborated before
27734 the body of @code{Decls}. This is the transitive implication of
27735 pragma @code{Elaborate_All} and it makes sense, because in general
27736 the body of @code{Put_Val} might have a call to something in a
27737 @code{with'ed} unit.
27739 In this case, the body of Utils (actually its spec) @code{with's}
27740 @code{Decls}. Unfortunately this means that the body of @code{Decls}
27741 must be elaborated before itself, in case there is a call from the
27742 body of @code{Utils}.
27744 Here is the exact chain of events we are worrying about:
27748 In the body of @code{Decls} a call is made from within the body of a library
27749 task to a subprogram in the package @code{Utils}. Since this call may
27750 occur at elaboration time (given that the task is activated at elaboration
27751 time), we have to assume the worst, i.e., that the
27752 call does happen at elaboration time.
27755 This means that the body and spec of @code{Util} must be elaborated before
27756 the body of @code{Decls} so that this call does not cause an access before
27760 Within the body of @code{Util}, specifically within the body of
27761 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
27765 One such @code{with}'ed package is package @code{Decls}, so there
27766 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
27767 In fact there is such a call in this example, but we would have to
27768 assume that there was such a call even if it were not there, since
27769 we are not supposed to write the body of @code{Decls} knowing what
27770 is in the body of @code{Utils}; certainly in the case of the
27771 static elaboration model, the compiler does not know what is in
27772 other bodies and must assume the worst.
27775 This means that the spec and body of @code{Decls} must also be
27776 elaborated before we elaborate the unit containing the call, but
27777 that unit is @code{Decls}! This means that the body of @code{Decls}
27778 must be elaborated before itself, and that's a circularity.
27782 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
27783 the body of @code{Decls} you will get a true Ada Reference Manual
27784 circularity that makes the program illegal.
27786 In practice, we have found that problems with the static model of
27787 elaboration in existing code often arise from library tasks, so
27788 we must address this particular situation.
27790 Note that if we compile and run the program above, using the dynamic model of
27791 elaboration (that is to say use the @option{-gnatE} switch),
27792 then it compiles, binds,
27793 links, and runs, printing the expected result of 2. Therefore in some sense
27794 the circularity here is only apparent, and we need to capture
27795 the properties of this program that distinguish it from other library-level
27796 tasks that have real elaboration problems.
27798 We have four possible answers to this question:
27803 Use the dynamic model of elaboration.
27805 If we use the @option{-gnatE} switch, then as noted above, the program works.
27806 Why is this? If we examine the task body, it is apparent that the task cannot
27808 @code{accept} statement until after elaboration has been completed, because
27809 the corresponding entry call comes from the main program, not earlier.
27810 This is why the dynamic model works here. But that's really giving
27811 up on a precise analysis, and we prefer to take this approach only if we cannot
27813 problem in any other manner. So let us examine two ways to reorganize
27814 the program to avoid the potential elaboration problem.
27817 Split library tasks into separate packages.
27819 Write separate packages, so that library tasks are isolated from
27820 other declarations as much as possible. Let us look at a variation on
27823 @smallexample @c ada
27831 package body Decls1 is
27832 task body Lib_Task is
27840 type My_Int is new Integer;
27841 function Ident (M : My_Int) return My_Int;
27845 package body Decls2 is
27846 function Ident (M : My_Int) return My_Int is
27854 procedure Put_Val (Arg : Decls2.My_Int);
27858 package body Utils is
27859 procedure Put_Val (Arg : Decls2.My_Int) is
27861 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
27868 Decls1.Lib_Task.Start;
27873 All we have done is to split @code{Decls} into two packages, one
27874 containing the library task, and one containing everything else. Now
27875 there is no cycle, and the program compiles, binds, links and executes
27876 using the default static model of elaboration.
27879 Declare separate task types.
27881 A significant part of the problem arises because of the use of the
27882 single task declaration form. This means that the elaboration of
27883 the task type, and the elaboration of the task itself (i.e.@: the
27884 creation of the task) happen at the same time. A good rule
27885 of style in Ada is to always create explicit task types. By
27886 following the additional step of placing task objects in separate
27887 packages from the task type declaration, many elaboration problems
27888 are avoided. Here is another modified example of the example program:
27890 @smallexample @c ada
27892 task type Lib_Task_Type is
27896 type My_Int is new Integer;
27898 function Ident (M : My_Int) return My_Int;
27902 package body Decls is
27903 task body Lib_Task_Type is
27909 function Ident (M : My_Int) return My_Int is
27917 procedure Put_Val (Arg : Decls.My_Int);
27921 package body Utils is
27922 procedure Put_Val (Arg : Decls.My_Int) is
27924 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
27930 Lib_Task : Decls.Lib_Task_Type;
27936 Declst.Lib_Task.Start;
27941 What we have done here is to replace the @code{task} declaration in
27942 package @code{Decls} with a @code{task type} declaration. Then we
27943 introduce a separate package @code{Declst} to contain the actual
27944 task object. This separates the elaboration issues for
27945 the @code{task type}
27946 declaration, which causes no trouble, from the elaboration issues
27947 of the task object, which is also unproblematic, since it is now independent
27948 of the elaboration of @code{Utils}.
27949 This separation of concerns also corresponds to
27950 a generally sound engineering principle of separating declarations
27951 from instances. This version of the program also compiles, binds, links,
27952 and executes, generating the expected output.
27955 Use No_Entry_Calls_In_Elaboration_Code restriction.
27956 @cindex No_Entry_Calls_In_Elaboration_Code
27958 The previous two approaches described how a program can be restructured
27959 to avoid the special problems caused by library task bodies. in practice,
27960 however, such restructuring may be difficult to apply to existing legacy code,
27961 so we must consider solutions that do not require massive rewriting.
27963 Let us consider more carefully why our original sample program works
27964 under the dynamic model of elaboration. The reason is that the code
27965 in the task body blocks immediately on the @code{accept}
27966 statement. Now of course there is nothing to prohibit elaboration
27967 code from making entry calls (for example from another library level task),
27968 so we cannot tell in isolation that
27969 the task will not execute the accept statement during elaboration.
27971 However, in practice it is very unusual to see elaboration code
27972 make any entry calls, and the pattern of tasks starting
27973 at elaboration time and then immediately blocking on @code{accept} or
27974 @code{select} statements is very common. What this means is that
27975 the compiler is being too pessimistic when it analyzes the
27976 whole package body as though it might be executed at elaboration
27979 If we know that the elaboration code contains no entry calls, (a very safe
27980 assumption most of the time, that could almost be made the default
27981 behavior), then we can compile all units of the program under control
27982 of the following configuration pragma:
27985 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
27989 This pragma can be placed in the @file{gnat.adc} file in the usual
27990 manner. If we take our original unmodified program and compile it
27991 in the presence of a @file{gnat.adc} containing the above pragma,
27992 then once again, we can compile, bind, link, and execute, obtaining
27993 the expected result. In the presence of this pragma, the compiler does
27994 not trace calls in a task body, that appear after the first @code{accept}
27995 or @code{select} statement, and therefore does not report a potential
27996 circularity in the original program.
27998 The compiler will check to the extent it can that the above
27999 restriction is not violated, but it is not always possible to do a
28000 complete check at compile time, so it is important to use this
28001 pragma only if the stated restriction is in fact met, that is to say
28002 no task receives an entry call before elaboration of all units is completed.
28006 @node Mixing Elaboration Models
28007 @section Mixing Elaboration Models
28009 So far, we have assumed that the entire program is either compiled
28010 using the dynamic model or static model, ensuring consistency. It
28011 is possible to mix the two models, but rules have to be followed
28012 if this mixing is done to ensure that elaboration checks are not
28015 The basic rule is that @emph{a unit compiled with the static model cannot
28016 be @code{with'ed} by a unit compiled with the dynamic model}. The
28017 reason for this is that in the static model, a unit assumes that
28018 its clients guarantee to use (the equivalent of) pragma
28019 @code{Elaborate_All} so that no elaboration checks are required
28020 in inner subprograms, and this assumption is violated if the
28021 client is compiled with dynamic checks.
28023 The precise rule is as follows. A unit that is compiled with dynamic
28024 checks can only @code{with} a unit that meets at least one of the
28025 following criteria:
28030 The @code{with'ed} unit is itself compiled with dynamic elaboration
28031 checks (that is with the @option{-gnatE} switch.
28034 The @code{with'ed} unit is an internal GNAT implementation unit from
28035 the System, Interfaces, Ada, or GNAT hierarchies.
28038 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28041 The @code{with'ing} unit (that is the client) has an explicit pragma
28042 @code{Elaborate_All} for the @code{with'ed} unit.
28047 If this rule is violated, that is if a unit with dynamic elaboration
28048 checks @code{with's} a unit that does not meet one of the above four
28049 criteria, then the binder (@code{gnatbind}) will issue a warning
28050 similar to that in the following example:
28053 warning: "x.ads" has dynamic elaboration checks and with's
28054 warning: "y.ads" which has static elaboration checks
28058 These warnings indicate that the rule has been violated, and that as a result
28059 elaboration checks may be missed in the resulting executable file.
28060 This warning may be suppressed using the @option{-ws} binder switch
28061 in the usual manner.
28063 One useful application of this mixing rule is in the case of a subsystem
28064 which does not itself @code{with} units from the remainder of the
28065 application. In this case, the entire subsystem can be compiled with
28066 dynamic checks to resolve a circularity in the subsystem, while
28067 allowing the main application that uses this subsystem to be compiled
28068 using the more reliable default static model.
28070 @node What to Do If the Default Elaboration Behavior Fails
28071 @section What to Do If the Default Elaboration Behavior Fails
28074 If the binder cannot find an acceptable order, it outputs detailed
28075 diagnostics. For example:
28081 error: elaboration circularity detected
28082 info: "proc (body)" must be elaborated before "pack (body)"
28083 info: reason: Elaborate_All probably needed in unit "pack (body)"
28084 info: recompile "pack (body)" with -gnatwl
28085 info: for full details
28086 info: "proc (body)"
28087 info: is needed by its spec:
28088 info: "proc (spec)"
28089 info: which is withed by:
28090 info: "pack (body)"
28091 info: "pack (body)" must be elaborated before "proc (body)"
28092 info: reason: pragma Elaborate in unit "proc (body)"
28098 In this case we have a cycle that the binder cannot break. On the one
28099 hand, there is an explicit pragma Elaborate in @code{proc} for
28100 @code{pack}. This means that the body of @code{pack} must be elaborated
28101 before the body of @code{proc}. On the other hand, there is elaboration
28102 code in @code{pack} that calls a subprogram in @code{proc}. This means
28103 that for maximum safety, there should really be a pragma
28104 Elaborate_All in @code{pack} for @code{proc} which would require that
28105 the body of @code{proc} be elaborated before the body of
28106 @code{pack}. Clearly both requirements cannot be satisfied.
28107 Faced with a circularity of this kind, you have three different options.
28110 @item Fix the program
28111 The most desirable option from the point of view of long-term maintenance
28112 is to rearrange the program so that the elaboration problems are avoided.
28113 One useful technique is to place the elaboration code into separate
28114 child packages. Another is to move some of the initialization code to
28115 explicitly called subprograms, where the program controls the order
28116 of initialization explicitly. Although this is the most desirable option,
28117 it may be impractical and involve too much modification, especially in
28118 the case of complex legacy code.
28120 @item Perform dynamic checks
28121 If the compilations are done using the
28123 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28124 manner. Dynamic checks are generated for all calls that could possibly result
28125 in raising an exception. With this switch, the compiler does not generate
28126 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28127 exactly as specified in the @cite{Ada Reference Manual}.
28128 The binder will generate
28129 an executable program that may or may not raise @code{Program_Error}, and then
28130 it is the programmer's job to ensure that it does not raise an exception. Note
28131 that it is important to compile all units with the switch, it cannot be used
28134 @item Suppress checks
28135 The drawback of dynamic checks is that they generate a
28136 significant overhead at run time, both in space and time. If you
28137 are absolutely sure that your program cannot raise any elaboration
28138 exceptions, and you still want to use the dynamic elaboration model,
28139 then you can use the configuration pragma
28140 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28141 example this pragma could be placed in the @file{gnat.adc} file.
28143 @item Suppress checks selectively
28144 When you know that certain calls or instantiations in elaboration code cannot
28145 possibly lead to an elaboration error, and the binder nevertheless complains
28146 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28147 elaboration circularities, it is possible to remove those warnings locally and
28148 obtain a program that will bind. Clearly this can be unsafe, and it is the
28149 responsibility of the programmer to make sure that the resulting program has no
28150 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28151 used with different granularity to suppress warnings and break elaboration
28156 Place the pragma that names the called subprogram in the declarative part
28157 that contains the call.
28160 Place the pragma in the declarative part, without naming an entity. This
28161 disables warnings on all calls in the corresponding declarative region.
28164 Place the pragma in the package spec that declares the called subprogram,
28165 and name the subprogram. This disables warnings on all elaboration calls to
28169 Place the pragma in the package spec that declares the called subprogram,
28170 without naming any entity. This disables warnings on all elaboration calls to
28171 all subprograms declared in this spec.
28173 @item Use Pragma Elaborate
28174 As previously described in section @xref{Treatment of Pragma Elaborate},
28175 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28176 that no elaboration checks are required on calls to the designated unit.
28177 There may be cases in which the caller knows that no transitive calls
28178 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28179 case where @code{pragma Elaborate_All} would cause a circularity.
28183 These five cases are listed in order of decreasing safety, and therefore
28184 require increasing programmer care in their application. Consider the
28187 @smallexample @c adanocomment
28189 function F1 return Integer;
28194 function F2 return Integer;
28195 function Pure (x : integer) return integer;
28196 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28197 -- pragma Suppress (Elaboration_Check); -- (4)
28201 package body Pack1 is
28202 function F1 return Integer is
28206 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28209 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28210 -- pragma Suppress(Elaboration_Check); -- (2)
28212 X1 := Pack2.F2 + 1; -- Elab. call (2)
28217 package body Pack2 is
28218 function F2 return Integer is
28222 function Pure (x : integer) return integer is
28224 return x ** 3 - 3 * x;
28228 with Pack1, Ada.Text_IO;
28231 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28234 In the absence of any pragmas, an attempt to bind this program produces
28235 the following diagnostics:
28241 error: elaboration circularity detected
28242 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28243 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28244 info: recompile "pack1 (body)" with -gnatwl for full details
28245 info: "pack1 (body)"
28246 info: must be elaborated along with its spec:
28247 info: "pack1 (spec)"
28248 info: which is withed by:
28249 info: "pack2 (body)"
28250 info: which must be elaborated along with its spec:
28251 info: "pack2 (spec)"
28252 info: which is withed by:
28253 info: "pack1 (body)"
28256 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28257 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28258 F2 is safe, even though F2 calls F1, because the call appears after the
28259 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28260 remove the warning on the call. It is also possible to use pragma (2)
28261 because there are no other potentially unsafe calls in the block.
28264 The call to @code{Pure} is safe because this function does not depend on the
28265 state of @code{Pack2}. Therefore any call to this function is safe, and it
28266 is correct to place pragma (3) in the corresponding package spec.
28269 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28270 warnings on all calls to functions declared therein. Note that this is not
28271 necessarily safe, and requires more detailed examination of the subprogram
28272 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28273 be already elaborated.
28277 It is hard to generalize on which of these four approaches should be
28278 taken. Obviously if it is possible to fix the program so that the default
28279 treatment works, this is preferable, but this may not always be practical.
28280 It is certainly simple enough to use
28282 but the danger in this case is that, even if the GNAT binder
28283 finds a correct elaboration order, it may not always do so,
28284 and certainly a binder from another Ada compiler might not. A
28285 combination of testing and analysis (for which the warnings generated
28288 switch can be useful) must be used to ensure that the program is free
28289 of errors. One switch that is useful in this testing is the
28290 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28293 Normally the binder tries to find an order that has the best chance
28294 of avoiding elaboration problems. However, if this switch is used, the binder
28295 plays a devil's advocate role, and tries to choose the order that
28296 has the best chance of failing. If your program works even with this
28297 switch, then it has a better chance of being error free, but this is still
28300 For an example of this approach in action, consider the C-tests (executable
28301 tests) from the ACVC suite. If these are compiled and run with the default
28302 treatment, then all but one of them succeed without generating any error
28303 diagnostics from the binder. However, there is one test that fails, and
28304 this is not surprising, because the whole point of this test is to ensure
28305 that the compiler can handle cases where it is impossible to determine
28306 a correct order statically, and it checks that an exception is indeed
28307 raised at run time.
28309 This one test must be compiled and run using the
28311 switch, and then it passes. Alternatively, the entire suite can
28312 be run using this switch. It is never wrong to run with the dynamic
28313 elaboration switch if your code is correct, and we assume that the
28314 C-tests are indeed correct (it is less efficient, but efficiency is
28315 not a factor in running the ACVC tests.)
28317 @node Elaboration for Access-to-Subprogram Values
28318 @section Elaboration for Access-to-Subprogram Values
28319 @cindex Access-to-subprogram
28322 Access-to-subprogram types (introduced in Ada 95) complicate
28323 the handling of elaboration. The trouble is that it becomes
28324 impossible to tell at compile time which procedure
28325 is being called. This means that it is not possible for the binder
28326 to analyze the elaboration requirements in this case.
28328 If at the point at which the access value is created
28329 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
28330 the body of the subprogram is
28331 known to have been elaborated, then the access value is safe, and its use
28332 does not require a check. This may be achieved by appropriate arrangement
28333 of the order of declarations if the subprogram is in the current unit,
28334 or, if the subprogram is in another unit, by using pragma
28335 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
28336 on the referenced unit.
28338 If the referenced body is not known to have been elaborated at the point
28339 the access value is created, then any use of the access value must do a
28340 dynamic check, and this dynamic check will fail and raise a
28341 @code{Program_Error} exception if the body has not been elaborated yet.
28342 GNAT will generate the necessary checks, and in addition, if the
28344 switch is set, will generate warnings that such checks are required.
28346 The use of dynamic dispatching for tagged types similarly generates
28347 a requirement for dynamic checks, and premature calls to any primitive
28348 operation of a tagged type before the body of the operation has been
28349 elaborated, will result in the raising of @code{Program_Error}.
28351 @node Summary of Procedures for Elaboration Control
28352 @section Summary of Procedures for Elaboration Control
28353 @cindex Elaboration control
28356 First, compile your program with the default options, using none of
28357 the special elaboration control switches. If the binder successfully
28358 binds your program, then you can be confident that, apart from issues
28359 raised by the use of access-to-subprogram types and dynamic dispatching,
28360 the program is free of elaboration errors. If it is important that the
28361 program be portable, then use the
28363 switch to generate warnings about missing @code{Elaborate} or
28364 @code{Elaborate_All} pragmas, and supply the missing pragmas.
28366 If the program fails to bind using the default static elaboration
28367 handling, then you can fix the program to eliminate the binder
28368 message, or recompile the entire program with the
28369 @option{-gnatE} switch to generate dynamic elaboration checks,
28370 and, if you are sure there really are no elaboration problems,
28371 use a global pragma @code{Suppress (Elaboration_Check)}.
28373 @node Other Elaboration Order Considerations
28374 @section Other Elaboration Order Considerations
28376 This section has been entirely concerned with the issue of finding a valid
28377 elaboration order, as defined by the Ada Reference Manual. In a case
28378 where several elaboration orders are valid, the task is to find one
28379 of the possible valid elaboration orders (and the static model in GNAT
28380 will ensure that this is achieved).
28382 The purpose of the elaboration rules in the Ada Reference Manual is to
28383 make sure that no entity is accessed before it has been elaborated. For
28384 a subprogram, this means that the spec and body must have been elaborated
28385 before the subprogram is called. For an object, this means that the object
28386 must have been elaborated before its value is read or written. A violation
28387 of either of these two requirements is an access before elaboration order,
28388 and this section has been all about avoiding such errors.
28390 In the case where more than one order of elaboration is possible, in the
28391 sense that access before elaboration errors are avoided, then any one of
28392 the orders is ``correct'' in the sense that it meets the requirements of
28393 the Ada Reference Manual, and no such error occurs.
28395 However, it may be the case for a given program, that there are
28396 constraints on the order of elaboration that come not from consideration
28397 of avoiding elaboration errors, but rather from extra-lingual logic
28398 requirements. Consider this example:
28400 @smallexample @c ada
28401 with Init_Constants;
28402 package Constants is
28407 package Init_Constants is
28408 procedure P; -- require a body
28409 end Init_Constants;
28412 package body Init_Constants is
28413 procedure P is begin null; end;
28417 end Init_Constants;
28421 Z : Integer := Constants.X + Constants.Y;
28425 with Text_IO; use Text_IO;
28428 Put_Line (Calc.Z'Img);
28433 In this example, there is more than one valid order of elaboration. For
28434 example both the following are correct orders:
28437 Init_Constants spec
28440 Init_Constants body
28445 Init_Constants spec
28446 Init_Constants body
28453 There is no language rule to prefer one or the other, both are correct
28454 from an order of elaboration point of view. But the programmatic effects
28455 of the two orders are very different. In the first, the elaboration routine
28456 of @code{Calc} initializes @code{Z} to zero, and then the main program
28457 runs with this value of zero. But in the second order, the elaboration
28458 routine of @code{Calc} runs after the body of Init_Constants has set
28459 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
28462 One could perhaps by applying pretty clever non-artificial intelligence
28463 to the situation guess that it is more likely that the second order of
28464 elaboration is the one desired, but there is no formal linguistic reason
28465 to prefer one over the other. In fact in this particular case, GNAT will
28466 prefer the second order, because of the rule that bodies are elaborated
28467 as soon as possible, but it's just luck that this is what was wanted
28468 (if indeed the second order was preferred).
28470 If the program cares about the order of elaboration routines in a case like
28471 this, it is important to specify the order required. In this particular
28472 case, that could have been achieved by adding to the spec of Calc:
28474 @smallexample @c ada
28475 pragma Elaborate_All (Constants);
28479 which requires that the body (if any) and spec of @code{Constants},
28480 as well as the body and spec of any unit @code{with}'ed by
28481 @code{Constants} be elaborated before @code{Calc} is elaborated.
28483 Clearly no automatic method can always guess which alternative you require,
28484 and if you are working with legacy code that had constraints of this kind
28485 which were not properly specified by adding @code{Elaborate} or
28486 @code{Elaborate_All} pragmas, then indeed it is possible that two different
28487 compilers can choose different orders.
28489 However, GNAT does attempt to diagnose the common situation where there
28490 are uninitialized variables in the visible part of a package spec, and the
28491 corresponding package body has an elaboration block that directly or
28492 indirectly initialized one or more of these variables. This is the situation
28493 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
28494 a warning that suggests this addition if it detects this situation.
28496 The @code{gnatbind}
28497 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
28498 out problems. This switch causes bodies to be elaborated as late as possible
28499 instead of as early as possible. In the example above, it would have forced
28500 the choice of the first elaboration order. If you get different results
28501 when using this switch, and particularly if one set of results is right,
28502 and one is wrong as far as you are concerned, it shows that you have some
28503 missing @code{Elaborate} pragmas. For the example above, we have the
28507 gnatmake -f -q main
28510 gnatmake -f -q main -bargs -p
28516 It is of course quite unlikely that both these results are correct, so
28517 it is up to you in a case like this to investigate the source of the
28518 difference, by looking at the two elaboration orders that are chosen,
28519 and figuring out which is correct, and then adding the necessary
28520 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
28524 @c *******************************
28525 @node Conditional Compilation
28526 @appendix Conditional Compilation
28527 @c *******************************
28528 @cindex Conditional compilation
28531 It is often necessary to arrange for a single source program
28532 to serve multiple purposes, where it is compiled in different
28533 ways to achieve these different goals. Some examples of the
28534 need for this feature are
28537 @item Adapting a program to a different hardware environment
28538 @item Adapting a program to a different target architecture
28539 @item Turning debugging features on and off
28540 @item Arranging for a program to compile with different compilers
28544 In C, or C++, the typical approach would be to use the preprocessor
28545 that is defined as part of the language. The Ada language does not
28546 contain such a feature. This is not an oversight, but rather a very
28547 deliberate design decision, based on the experience that overuse of
28548 the preprocessing features in C and C++ can result in programs that
28549 are extremely difficult to maintain. For example, if we have ten
28550 switches that can be on or off, this means that there are a thousand
28551 separate programs, any one of which might not even be syntactically
28552 correct, and even if syntactically correct, the resulting program
28553 might not work correctly. Testing all combinations can quickly become
28556 Nevertheless, the need to tailor programs certainly exists, and in
28557 this Appendix we will discuss how this can
28558 be achieved using Ada in general, and GNAT in particular.
28561 * Use of Boolean Constants::
28562 * Debugging - A Special Case::
28563 * Conditionalizing Declarations::
28564 * Use of Alternative Implementations::
28568 @node Use of Boolean Constants
28569 @section Use of Boolean Constants
28572 In the case where the difference is simply which code
28573 sequence is executed, the cleanest solution is to use Boolean
28574 constants to control which code is executed.
28576 @smallexample @c ada
28578 FP_Initialize_Required : constant Boolean := True;
28580 if FP_Initialize_Required then
28587 Not only will the code inside the @code{if} statement not be executed if
28588 the constant Boolean is @code{False}, but it will also be completely
28589 deleted from the program.
28590 However, the code is only deleted after the @code{if} statement
28591 has been checked for syntactic and semantic correctness.
28592 (In contrast, with preprocessors the code is deleted before the
28593 compiler ever gets to see it, so it is not checked until the switch
28595 @cindex Preprocessors (contrasted with conditional compilation)
28597 Typically the Boolean constants will be in a separate package,
28600 @smallexample @c ada
28603 FP_Initialize_Required : constant Boolean := True;
28604 Reset_Available : constant Boolean := False;
28611 The @code{Config} package exists in multiple forms for the various targets,
28612 with an appropriate script selecting the version of @code{Config} needed.
28613 Then any other unit requiring conditional compilation can do a @code{with}
28614 of @code{Config} to make the constants visible.
28617 @node Debugging - A Special Case
28618 @section Debugging - A Special Case
28621 A common use of conditional code is to execute statements (for example
28622 dynamic checks, or output of intermediate results) under control of a
28623 debug switch, so that the debugging behavior can be turned on and off.
28624 This can be done using a Boolean constant to control whether the code
28627 @smallexample @c ada
28630 Put_Line ("got to the first stage!");
28638 @smallexample @c ada
28640 if Debugging and then Temperature > 999.0 then
28641 raise Temperature_Crazy;
28647 Since this is a common case, there are special features to deal with
28648 this in a convenient manner. For the case of tests, Ada 2005 has added
28649 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
28650 @cindex pragma @code{Assert}
28651 on the @code{Assert} pragma that has always been available in GNAT, so this
28652 feature may be used with GNAT even if you are not using Ada 2005 features.
28653 The use of pragma @code{Assert} is described in
28654 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
28655 example, the last test could be written:
28657 @smallexample @c ada
28658 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
28664 @smallexample @c ada
28665 pragma Assert (Temperature <= 999.0);
28669 In both cases, if assertions are active and the temperature is excessive,
28670 the exception @code{Assert_Failure} will be raised, with the given string in
28671 the first case or a string indicating the location of the pragma in the second
28672 case used as the exception message.
28674 You can turn assertions on and off by using the @code{Assertion_Policy}
28676 @cindex pragma @code{Assertion_Policy}
28677 This is an Ada 2005 pragma which is implemented in all modes by
28678 GNAT, but only in the latest versions of GNAT which include Ada 2005
28679 capability. Alternatively, you can use the @option{-gnata} switch
28680 @cindex @option{-gnata} switch
28681 to enable assertions from the command line (this is recognized by all versions
28684 For the example above with the @code{Put_Line}, the GNAT-specific pragma
28685 @code{Debug} can be used:
28686 @cindex pragma @code{Debug}
28688 @smallexample @c ada
28689 pragma Debug (Put_Line ("got to the first stage!"));
28693 If debug pragmas are enabled, the argument, which must be of the form of
28694 a procedure call, is executed (in this case, @code{Put_Line} will be called).
28695 Only one call can be present, but of course a special debugging procedure
28696 containing any code you like can be included in the program and then
28697 called in a pragma @code{Debug} argument as needed.
28699 One advantage of pragma @code{Debug} over the @code{if Debugging then}
28700 construct is that pragma @code{Debug} can appear in declarative contexts,
28701 such as at the very beginning of a procedure, before local declarations have
28704 Debug pragmas are enabled using either the @option{-gnata} switch that also
28705 controls assertions, or with a separate Debug_Policy pragma.
28706 @cindex pragma @code{Debug_Policy}
28707 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
28708 in Ada 95 and Ada 83 programs as well), and is analogous to
28709 pragma @code{Assertion_Policy} to control assertions.
28711 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
28712 and thus they can appear in @file{gnat.adc} if you are not using a
28713 project file, or in the file designated to contain configuration pragmas
28715 They then apply to all subsequent compilations. In practice the use of
28716 the @option{-gnata} switch is often the most convenient method of controlling
28717 the status of these pragmas.
28719 Note that a pragma is not a statement, so in contexts where a statement
28720 sequence is required, you can't just write a pragma on its own. You have
28721 to add a @code{null} statement.
28723 @smallexample @c ada
28726 @dots{} -- some statements
28728 pragma Assert (Num_Cases < 10);
28735 @node Conditionalizing Declarations
28736 @section Conditionalizing Declarations
28739 In some cases, it may be necessary to conditionalize declarations to meet
28740 different requirements. For example we might want a bit string whose length
28741 is set to meet some hardware message requirement.
28743 In some cases, it may be possible to do this using declare blocks controlled
28744 by conditional constants:
28746 @smallexample @c ada
28748 if Small_Machine then
28750 X : Bit_String (1 .. 10);
28756 X : Large_Bit_String (1 .. 1000);
28765 Note that in this approach, both declarations are analyzed by the
28766 compiler so this can only be used where both declarations are legal,
28767 even though one of them will not be used.
28769 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
28770 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
28771 that are parameterized by these constants. For example
28773 @smallexample @c ada
28776 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
28782 If @code{Bits_Per_Word} is set to 32, this generates either
28784 @smallexample @c ada
28787 Field1 at 0 range 0 .. 32;
28793 for the big endian case, or
28795 @smallexample @c ada
28798 Field1 at 0 range 10 .. 32;
28804 for the little endian case. Since a powerful subset of Ada expression
28805 notation is usable for creating static constants, clever use of this
28806 feature can often solve quite difficult problems in conditionalizing
28807 compilation (note incidentally that in Ada 95, the little endian
28808 constant was introduced as @code{System.Default_Bit_Order}, so you do not
28809 need to define this one yourself).
28812 @node Use of Alternative Implementations
28813 @section Use of Alternative Implementations
28816 In some cases, none of the approaches described above are adequate. This
28817 can occur for example if the set of declarations required is radically
28818 different for two different configurations.
28820 In this situation, the official Ada way of dealing with conditionalizing
28821 such code is to write separate units for the different cases. As long as
28822 this does not result in excessive duplication of code, this can be done
28823 without creating maintenance problems. The approach is to share common
28824 code as far as possible, and then isolate the code and declarations
28825 that are different. Subunits are often a convenient method for breaking
28826 out a piece of a unit that is to be conditionalized, with separate files
28827 for different versions of the subunit for different targets, where the
28828 build script selects the right one to give to the compiler.
28829 @cindex Subunits (and conditional compilation)
28831 As an example, consider a situation where a new feature in Ada 2005
28832 allows something to be done in a really nice way. But your code must be able
28833 to compile with an Ada 95 compiler. Conceptually you want to say:
28835 @smallexample @c ada
28838 @dots{} neat Ada 2005 code
28840 @dots{} not quite as neat Ada 95 code
28846 where @code{Ada_2005} is a Boolean constant.
28848 But this won't work when @code{Ada_2005} is set to @code{False},
28849 since the @code{then} clause will be illegal for an Ada 95 compiler.
28850 (Recall that although such unreachable code would eventually be deleted
28851 by the compiler, it still needs to be legal. If it uses features
28852 introduced in Ada 2005, it will be illegal in Ada 95.)
28854 So instead we write
28856 @smallexample @c ada
28857 procedure Insert is separate;
28861 Then we have two files for the subunit @code{Insert}, with the two sets of
28863 If the package containing this is called @code{File_Queries}, then we might
28867 @item @file{file_queries-insert-2005.adb}
28868 @item @file{file_queries-insert-95.adb}
28872 and the build script renames the appropriate file to
28875 file_queries-insert.adb
28879 and then carries out the compilation.
28881 This can also be done with project files' naming schemes. For example:
28883 @smallexample @c project
28884 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
28888 Note also that with project files it is desirable to use a different extension
28889 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
28890 conflict may arise through another commonly used feature: to declare as part
28891 of the project a set of directories containing all the sources obeying the
28892 default naming scheme.
28894 The use of alternative units is certainly feasible in all situations,
28895 and for example the Ada part of the GNAT run-time is conditionalized
28896 based on the target architecture using this approach. As a specific example,
28897 consider the implementation of the AST feature in VMS. There is one
28905 which is the same for all architectures, and three bodies:
28909 used for all non-VMS operating systems
28910 @item s-asthan-vms-alpha.adb
28911 used for VMS on the Alpha
28912 @item s-asthan-vms-ia64.adb
28913 used for VMS on the ia64
28917 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
28918 this operating system feature is not available, and the two remaining
28919 versions interface with the corresponding versions of VMS to provide
28920 VMS-compatible AST handling. The GNAT build script knows the architecture
28921 and operating system, and automatically selects the right version,
28922 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
28924 Another style for arranging alternative implementations is through Ada's
28925 access-to-subprogram facility.
28926 In case some functionality is to be conditionally included,
28927 you can declare an access-to-procedure variable @code{Ref} that is initialized
28928 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
28930 In some library package, set @code{Ref} to @code{Proc'Access} for some
28931 procedure @code{Proc} that performs the relevant processing.
28932 The initialization only occurs if the library package is included in the
28934 The same idea can also be implemented using tagged types and dispatching
28938 @node Preprocessing
28939 @section Preprocessing
28940 @cindex Preprocessing
28943 Although it is quite possible to conditionalize code without the use of
28944 C-style preprocessing, as described earlier in this section, it is
28945 nevertheless convenient in some cases to use the C approach. Moreover,
28946 older Ada compilers have often provided some preprocessing capability,
28947 so legacy code may depend on this approach, even though it is not
28950 To accommodate such use, GNAT provides a preprocessor (modeled to a large
28951 extent on the various preprocessors that have been used
28952 with legacy code on other compilers, to enable easier transition).
28954 The preprocessor may be used in two separate modes. It can be used quite
28955 separately from the compiler, to generate a separate output source file
28956 that is then fed to the compiler as a separate step. This is the
28957 @code{gnatprep} utility, whose use is fully described in
28958 @ref{Preprocessing Using gnatprep}.
28959 @cindex @code{gnatprep}
28961 The preprocessing language allows such constructs as
28965 #if DEBUG or PRIORITY > 4 then
28966 bunch of declarations
28968 completely different bunch of declarations
28974 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
28975 defined either on the command line or in a separate file.
28977 The other way of running the preprocessor is even closer to the C style and
28978 often more convenient. In this approach the preprocessing is integrated into
28979 the compilation process. The compiler is fed the preprocessor input which
28980 includes @code{#if} lines etc, and then the compiler carries out the
28981 preprocessing internally and processes the resulting output.
28982 For more details on this approach, see @ref{Integrated Preprocessing}.
28985 @c *******************************
28986 @node Inline Assembler
28987 @appendix Inline Assembler
28988 @c *******************************
28991 If you need to write low-level software that interacts directly
28992 with the hardware, Ada provides two ways to incorporate assembly
28993 language code into your program. First, you can import and invoke
28994 external routines written in assembly language, an Ada feature fully
28995 supported by GNAT@. However, for small sections of code it may be simpler
28996 or more efficient to include assembly language statements directly
28997 in your Ada source program, using the facilities of the implementation-defined
28998 package @code{System.Machine_Code}, which incorporates the gcc
28999 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29000 including the following:
29003 @item No need to use non-Ada tools
29004 @item Consistent interface over different targets
29005 @item Automatic usage of the proper calling conventions
29006 @item Access to Ada constants and variables
29007 @item Definition of intrinsic routines
29008 @item Possibility of inlining a subprogram comprising assembler code
29009 @item Code optimizer can take Inline Assembler code into account
29012 This chapter presents a series of examples to show you how to use
29013 the Inline Assembler. Although it focuses on the Intel x86,
29014 the general approach applies also to other processors.
29015 It is assumed that you are familiar with Ada
29016 and with assembly language programming.
29019 * Basic Assembler Syntax::
29020 * A Simple Example of Inline Assembler::
29021 * Output Variables in Inline Assembler::
29022 * Input Variables in Inline Assembler::
29023 * Inlining Inline Assembler Code::
29024 * Other Asm Functionality::
29027 @c ---------------------------------------------------------------------------
29028 @node Basic Assembler Syntax
29029 @section Basic Assembler Syntax
29032 The assembler used by GNAT and gcc is based not on the Intel assembly
29033 language, but rather on a language that descends from the AT&T Unix
29034 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29035 The following table summarizes the main features of @emph{as} syntax
29036 and points out the differences from the Intel conventions.
29037 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29038 pre-processor) documentation for further information.
29041 @item Register names
29042 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29044 Intel: No extra punctuation; for example @code{eax}
29046 @item Immediate operand
29047 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29049 Intel: No extra punctuation; for example @code{4}
29052 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29054 Intel: No extra punctuation; for example @code{loc}
29056 @item Memory contents
29057 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29059 Intel: Square brackets; for example @code{[loc]}
29061 @item Register contents
29062 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29064 Intel: Square brackets; for example @code{[eax]}
29066 @item Hexadecimal numbers
29067 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29069 Intel: Trailing ``h''; for example @code{A0h}
29072 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29075 Intel: Implicit, deduced by assembler; for example @code{mov}
29077 @item Instruction repetition
29078 gcc / @emph{as}: Split into two lines; for example
29084 Intel: Keep on one line; for example @code{rep stosl}
29086 @item Order of operands
29087 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29089 Intel: Destination first; for example @code{mov eax, 4}
29092 @c ---------------------------------------------------------------------------
29093 @node A Simple Example of Inline Assembler
29094 @section A Simple Example of Inline Assembler
29097 The following example will generate a single assembly language statement,
29098 @code{nop}, which does nothing. Despite its lack of run-time effect,
29099 the example will be useful in illustrating the basics of
29100 the Inline Assembler facility.
29102 @smallexample @c ada
29104 with System.Machine_Code; use System.Machine_Code;
29105 procedure Nothing is
29112 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29113 here it takes one parameter, a @emph{template string} that must be a static
29114 expression and that will form the generated instruction.
29115 @code{Asm} may be regarded as a compile-time procedure that parses
29116 the template string and additional parameters (none here),
29117 from which it generates a sequence of assembly language instructions.
29119 The examples in this chapter will illustrate several of the forms
29120 for invoking @code{Asm}; a complete specification of the syntax
29121 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29124 Under the standard GNAT conventions, the @code{Nothing} procedure
29125 should be in a file named @file{nothing.adb}.
29126 You can build the executable in the usual way:
29130 However, the interesting aspect of this example is not its run-time behavior
29131 but rather the generated assembly code.
29132 To see this output, invoke the compiler as follows:
29134 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29136 where the options are:
29140 compile only (no bind or link)
29142 generate assembler listing
29143 @item -fomit-frame-pointer
29144 do not set up separate stack frames
29146 do not add runtime checks
29149 This gives a human-readable assembler version of the code. The resulting
29150 file will have the same name as the Ada source file, but with a @code{.s}
29151 extension. In our example, the file @file{nothing.s} has the following
29156 .file "nothing.adb"
29158 ___gnu_compiled_ada:
29161 .globl __ada_nothing
29173 The assembly code you included is clearly indicated by
29174 the compiler, between the @code{#APP} and @code{#NO_APP}
29175 delimiters. The character before the 'APP' and 'NOAPP'
29176 can differ on different targets. For example, GNU/Linux uses '#APP' while
29177 on NT you will see '/APP'.
29179 If you make a mistake in your assembler code (such as using the
29180 wrong size modifier, or using a wrong operand for the instruction) GNAT
29181 will report this error in a temporary file, which will be deleted when
29182 the compilation is finished. Generating an assembler file will help
29183 in such cases, since you can assemble this file separately using the
29184 @emph{as} assembler that comes with gcc.
29186 Assembling the file using the command
29189 as @file{nothing.s}
29192 will give you error messages whose lines correspond to the assembler
29193 input file, so you can easily find and correct any mistakes you made.
29194 If there are no errors, @emph{as} will generate an object file
29195 @file{nothing.out}.
29197 @c ---------------------------------------------------------------------------
29198 @node Output Variables in Inline Assembler
29199 @section Output Variables in Inline Assembler
29202 The examples in this section, showing how to access the processor flags,
29203 illustrate how to specify the destination operands for assembly language
29206 @smallexample @c ada
29208 with Interfaces; use Interfaces;
29209 with Ada.Text_IO; use Ada.Text_IO;
29210 with System.Machine_Code; use System.Machine_Code;
29211 procedure Get_Flags is
29212 Flags : Unsigned_32;
29215 Asm ("pushfl" & LF & HT & -- push flags on stack
29216 "popl %%eax" & LF & HT & -- load eax with flags
29217 "movl %%eax, %0", -- store flags in variable
29218 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29219 Put_Line ("Flags register:" & Flags'Img);
29224 In order to have a nicely aligned assembly listing, we have separated
29225 multiple assembler statements in the Asm template string with linefeed
29226 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29227 The resulting section of the assembly output file is:
29234 movl %eax, -40(%ebp)
29239 It would have been legal to write the Asm invocation as:
29242 Asm ("pushfl popl %%eax movl %%eax, %0")
29245 but in the generated assembler file, this would come out as:
29249 pushfl popl %eax movl %eax, -40(%ebp)
29253 which is not so convenient for the human reader.
29255 We use Ada comments
29256 at the end of each line to explain what the assembler instructions
29257 actually do. This is a useful convention.
29259 When writing Inline Assembler instructions, you need to precede each register
29260 and variable name with a percent sign. Since the assembler already requires
29261 a percent sign at the beginning of a register name, you need two consecutive
29262 percent signs for such names in the Asm template string, thus @code{%%eax}.
29263 In the generated assembly code, one of the percent signs will be stripped off.
29265 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29266 variables: operands you later define using @code{Input} or @code{Output}
29267 parameters to @code{Asm}.
29268 An output variable is illustrated in
29269 the third statement in the Asm template string:
29273 The intent is to store the contents of the eax register in a variable that can
29274 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29275 necessarily work, since the compiler might optimize by using a register
29276 to hold Flags, and the expansion of the @code{movl} instruction would not be
29277 aware of this optimization. The solution is not to store the result directly
29278 but rather to advise the compiler to choose the correct operand form;
29279 that is the purpose of the @code{%0} output variable.
29281 Information about the output variable is supplied in the @code{Outputs}
29282 parameter to @code{Asm}:
29284 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29287 The output is defined by the @code{Asm_Output} attribute of the target type;
29288 the general format is
29290 Type'Asm_Output (constraint_string, variable_name)
29293 The constraint string directs the compiler how
29294 to store/access the associated variable. In the example
29296 Unsigned_32'Asm_Output ("=m", Flags);
29298 the @code{"m"} (memory) constraint tells the compiler that the variable
29299 @code{Flags} should be stored in a memory variable, thus preventing
29300 the optimizer from keeping it in a register. In contrast,
29302 Unsigned_32'Asm_Output ("=r", Flags);
29304 uses the @code{"r"} (register) constraint, telling the compiler to
29305 store the variable in a register.
29307 If the constraint is preceded by the equal character (@strong{=}), it tells
29308 the compiler that the variable will be used to store data into it.
29310 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29311 allowing the optimizer to choose whatever it deems best.
29313 There are a fairly large number of constraints, but the ones that are
29314 most useful (for the Intel x86 processor) are the following:
29320 global (i.e.@: can be stored anywhere)
29338 use one of eax, ebx, ecx or edx
29340 use one of eax, ebx, ecx, edx, esi or edi
29343 The full set of constraints is described in the gcc and @emph{as}
29344 documentation; note that it is possible to combine certain constraints
29345 in one constraint string.
29347 You specify the association of an output variable with an assembler operand
29348 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
29350 @smallexample @c ada
29352 Asm ("pushfl" & LF & HT & -- push flags on stack
29353 "popl %%eax" & LF & HT & -- load eax with flags
29354 "movl %%eax, %0", -- store flags in variable
29355 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29359 @code{%0} will be replaced in the expanded code by the appropriate operand,
29361 the compiler decided for the @code{Flags} variable.
29363 In general, you may have any number of output variables:
29366 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29368 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29369 of @code{Asm_Output} attributes
29373 @smallexample @c ada
29375 Asm ("movl %%eax, %0" & LF & HT &
29376 "movl %%ebx, %1" & LF & HT &
29378 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29379 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29380 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29384 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29385 in the Ada program.
29387 As a variation on the @code{Get_Flags} example, we can use the constraints
29388 string to direct the compiler to store the eax register into the @code{Flags}
29389 variable, instead of including the store instruction explicitly in the
29390 @code{Asm} template string:
29392 @smallexample @c ada
29394 with Interfaces; use Interfaces;
29395 with Ada.Text_IO; use Ada.Text_IO;
29396 with System.Machine_Code; use System.Machine_Code;
29397 procedure Get_Flags_2 is
29398 Flags : Unsigned_32;
29401 Asm ("pushfl" & LF & HT & -- push flags on stack
29402 "popl %%eax", -- save flags in eax
29403 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29404 Put_Line ("Flags register:" & Flags'Img);
29410 The @code{"a"} constraint tells the compiler that the @code{Flags}
29411 variable will come from the eax register. Here is the resulting code:
29419 movl %eax,-40(%ebp)
29424 The compiler generated the store of eax into Flags after
29425 expanding the assembler code.
29427 Actually, there was no need to pop the flags into the eax register;
29428 more simply, we could just pop the flags directly into the program variable:
29430 @smallexample @c ada
29432 with Interfaces; use Interfaces;
29433 with Ada.Text_IO; use Ada.Text_IO;
29434 with System.Machine_Code; use System.Machine_Code;
29435 procedure Get_Flags_3 is
29436 Flags : Unsigned_32;
29439 Asm ("pushfl" & LF & HT & -- push flags on stack
29440 "pop %0", -- save flags in Flags
29441 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29442 Put_Line ("Flags register:" & Flags'Img);
29447 @c ---------------------------------------------------------------------------
29448 @node Input Variables in Inline Assembler
29449 @section Input Variables in Inline Assembler
29452 The example in this section illustrates how to specify the source operands
29453 for assembly language statements.
29454 The program simply increments its input value by 1:
29456 @smallexample @c ada
29458 with Interfaces; use Interfaces;
29459 with Ada.Text_IO; use Ada.Text_IO;
29460 with System.Machine_Code; use System.Machine_Code;
29461 procedure Increment is
29463 function Incr (Value : Unsigned_32) return Unsigned_32 is
29464 Result : Unsigned_32;
29467 Inputs => Unsigned_32'Asm_Input ("a", Value),
29468 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29472 Value : Unsigned_32;
29476 Put_Line ("Value before is" & Value'Img);
29477 Value := Incr (Value);
29478 Put_Line ("Value after is" & Value'Img);
29483 The @code{Outputs} parameter to @code{Asm} specifies
29484 that the result will be in the eax register and that it is to be stored
29485 in the @code{Result} variable.
29487 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29488 but with an @code{Asm_Input} attribute.
29489 The @code{"="} constraint, indicating an output value, is not present.
29491 You can have multiple input variables, in the same way that you can have more
29492 than one output variable.
29494 The parameter count (%0, %1) etc, now starts at the first input
29495 statement, and continues with the output statements.
29496 When both parameters use the same variable, the
29497 compiler will treat them as the same %n operand, which is the case here.
29499 Just as the @code{Outputs} parameter causes the register to be stored into the
29500 target variable after execution of the assembler statements, so does the
29501 @code{Inputs} parameter cause its variable to be loaded into the register
29502 before execution of the assembler statements.
29504 Thus the effect of the @code{Asm} invocation is:
29506 @item load the 32-bit value of @code{Value} into eax
29507 @item execute the @code{incl %eax} instruction
29508 @item store the contents of eax into the @code{Result} variable
29511 The resulting assembler file (with @option{-O2} optimization) contains:
29514 _increment__incr.1:
29527 @c ---------------------------------------------------------------------------
29528 @node Inlining Inline Assembler Code
29529 @section Inlining Inline Assembler Code
29532 For a short subprogram such as the @code{Incr} function in the previous
29533 section, the overhead of the call and return (creating / deleting the stack
29534 frame) can be significant, compared to the amount of code in the subprogram
29535 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29536 which directs the compiler to expand invocations of the subprogram at the
29537 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29538 Here is the resulting program:
29540 @smallexample @c ada
29542 with Interfaces; use Interfaces;
29543 with Ada.Text_IO; use Ada.Text_IO;
29544 with System.Machine_Code; use System.Machine_Code;
29545 procedure Increment_2 is
29547 function Incr (Value : Unsigned_32) return Unsigned_32 is
29548 Result : Unsigned_32;
29551 Inputs => Unsigned_32'Asm_Input ("a", Value),
29552 Outputs => Unsigned_32'Asm_Output ("=a", Result));
29555 pragma Inline (Increment);
29557 Value : Unsigned_32;
29561 Put_Line ("Value before is" & Value'Img);
29562 Value := Increment (Value);
29563 Put_Line ("Value after is" & Value'Img);
29568 Compile the program with both optimization (@option{-O2}) and inlining
29569 (@option{-gnatn}) enabled.
29571 The @code{Incr} function is still compiled as usual, but at the
29572 point in @code{Increment} where our function used to be called:
29577 call _increment__incr.1
29582 the code for the function body directly appears:
29595 thus saving the overhead of stack frame setup and an out-of-line call.
29597 @c ---------------------------------------------------------------------------
29598 @node Other Asm Functionality
29599 @section Other @code{Asm} Functionality
29602 This section describes two important parameters to the @code{Asm}
29603 procedure: @code{Clobber}, which identifies register usage;
29604 and @code{Volatile}, which inhibits unwanted optimizations.
29607 * The Clobber Parameter::
29608 * The Volatile Parameter::
29611 @c ---------------------------------------------------------------------------
29612 @node The Clobber Parameter
29613 @subsection The @code{Clobber} Parameter
29616 One of the dangers of intermixing assembly language and a compiled language
29617 such as Ada is that the compiler needs to be aware of which registers are
29618 being used by the assembly code. In some cases, such as the earlier examples,
29619 the constraint string is sufficient to indicate register usage (e.g.,
29621 the eax register). But more generally, the compiler needs an explicit
29622 identification of the registers that are used by the Inline Assembly
29625 Using a register that the compiler doesn't know about
29626 could be a side effect of an instruction (like @code{mull}
29627 storing its result in both eax and edx).
29628 It can also arise from explicit register usage in your
29629 assembly code; for example:
29632 Asm ("movl %0, %%ebx" & LF & HT &
29634 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29635 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
29639 where the compiler (since it does not analyze the @code{Asm} template string)
29640 does not know you are using the ebx register.
29642 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29643 to identify the registers that will be used by your assembly code:
29647 Asm ("movl %0, %%ebx" & LF & HT &
29649 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29650 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29655 The Clobber parameter is a static string expression specifying the
29656 register(s) you are using. Note that register names are @emph{not} prefixed
29657 by a percent sign. Also, if more than one register is used then their names
29658 are separated by commas; e.g., @code{"eax, ebx"}
29660 The @code{Clobber} parameter has several additional uses:
29662 @item Use ``register'' name @code{cc} to indicate that flags might have changed
29663 @item Use ``register'' name @code{memory} if you changed a memory location
29666 @c ---------------------------------------------------------------------------
29667 @node The Volatile Parameter
29668 @subsection The @code{Volatile} Parameter
29669 @cindex Volatile parameter
29672 Compiler optimizations in the presence of Inline Assembler may sometimes have
29673 unwanted effects. For example, when an @code{Asm} invocation with an input
29674 variable is inside a loop, the compiler might move the loading of the input
29675 variable outside the loop, regarding it as a one-time initialization.
29677 If this effect is not desired, you can disable such optimizations by setting
29678 the @code{Volatile} parameter to @code{True}; for example:
29680 @smallexample @c ada
29682 Asm ("movl %0, %%ebx" & LF & HT &
29684 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29685 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29691 By default, @code{Volatile} is set to @code{False} unless there is no
29692 @code{Outputs} parameter.
29694 Although setting @code{Volatile} to @code{True} prevents unwanted
29695 optimizations, it will also disable other optimizations that might be
29696 important for efficiency. In general, you should set @code{Volatile}
29697 to @code{True} only if the compiler's optimizations have created
29699 @c END OF INLINE ASSEMBLER CHAPTER
29700 @c ===============================
29702 @c ***********************************
29703 @c * Compatibility and Porting Guide *
29704 @c ***********************************
29705 @node Compatibility and Porting Guide
29706 @appendix Compatibility and Porting Guide
29709 This chapter describes the compatibility issues that may arise between
29710 GNAT and other Ada compilation systems (including those for Ada 83),
29711 and shows how GNAT can expedite porting
29712 applications developed in other Ada environments.
29715 * Compatibility with Ada 83::
29716 * Compatibility between Ada 95 and Ada 2005::
29717 * Implementation-dependent characteristics::
29718 * Compatibility with Other Ada Systems::
29719 * Representation Clauses::
29721 @c Brief section is only in non-VMS version
29722 @c Full chapter is in VMS version
29723 * Compatibility with HP Ada 83::
29726 * Transitioning to 64-Bit GNAT for OpenVMS::
29730 @node Compatibility with Ada 83
29731 @section Compatibility with Ada 83
29732 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
29735 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
29736 particular, the design intention was that the difficulties associated
29737 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
29738 that occur when moving from one Ada 83 system to another.
29740 However, there are a number of points at which there are minor
29741 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
29742 full details of these issues,
29743 and should be consulted for a complete treatment.
29745 following subsections treat the most likely issues to be encountered.
29748 * Legal Ada 83 programs that are illegal in Ada 95::
29749 * More deterministic semantics::
29750 * Changed semantics::
29751 * Other language compatibility issues::
29754 @node Legal Ada 83 programs that are illegal in Ada 95
29755 @subsection Legal Ada 83 programs that are illegal in Ada 95
29757 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
29758 Ada 95 and thus also in Ada 2005:
29761 @item Character literals
29762 Some uses of character literals are ambiguous. Since Ada 95 has introduced
29763 @code{Wide_Character} as a new predefined character type, some uses of
29764 character literals that were legal in Ada 83 are illegal in Ada 95.
29766 @smallexample @c ada
29767 for Char in 'A' .. 'Z' loop @dots{} end loop;
29771 The problem is that @code{'A'} and @code{'Z'} could be from either
29772 @code{Character} or @code{Wide_Character}. The simplest correction
29773 is to make the type explicit; e.g.:
29774 @smallexample @c ada
29775 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
29778 @item New reserved words
29779 The identifiers @code{abstract}, @code{aliased}, @code{protected},
29780 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
29781 Existing Ada 83 code using any of these identifiers must be edited to
29782 use some alternative name.
29784 @item Freezing rules
29785 The rules in Ada 95 are slightly different with regard to the point at
29786 which entities are frozen, and representation pragmas and clauses are
29787 not permitted past the freeze point. This shows up most typically in
29788 the form of an error message complaining that a representation item
29789 appears too late, and the appropriate corrective action is to move
29790 the item nearer to the declaration of the entity to which it refers.
29792 A particular case is that representation pragmas
29795 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
29797 cannot be applied to a subprogram body. If necessary, a separate subprogram
29798 declaration must be introduced to which the pragma can be applied.
29800 @item Optional bodies for library packages
29801 In Ada 83, a package that did not require a package body was nevertheless
29802 allowed to have one. This lead to certain surprises in compiling large
29803 systems (situations in which the body could be unexpectedly ignored by the
29804 binder). In Ada 95, if a package does not require a body then it is not
29805 permitted to have a body. To fix this problem, simply remove a redundant
29806 body if it is empty, or, if it is non-empty, introduce a dummy declaration
29807 into the spec that makes the body required. One approach is to add a private
29808 part to the package declaration (if necessary), and define a parameterless
29809 procedure called @code{Requires_Body}, which must then be given a dummy
29810 procedure body in the package body, which then becomes required.
29811 Another approach (assuming that this does not introduce elaboration
29812 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
29813 since one effect of this pragma is to require the presence of a package body.
29815 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
29816 In Ada 95, the exception @code{Numeric_Error} is a renaming of
29817 @code{Constraint_Error}.
29818 This means that it is illegal to have separate exception handlers for
29819 the two exceptions. The fix is simply to remove the handler for the
29820 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
29821 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
29823 @item Indefinite subtypes in generics
29824 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
29825 as the actual for a generic formal private type, but then the instantiation
29826 would be illegal if there were any instances of declarations of variables
29827 of this type in the generic body. In Ada 95, to avoid this clear violation
29828 of the methodological principle known as the ``contract model'',
29829 the generic declaration explicitly indicates whether
29830 or not such instantiations are permitted. If a generic formal parameter
29831 has explicit unknown discriminants, indicated by using @code{(<>)} after the
29832 type name, then it can be instantiated with indefinite types, but no
29833 stand-alone variables can be declared of this type. Any attempt to declare
29834 such a variable will result in an illegality at the time the generic is
29835 declared. If the @code{(<>)} notation is not used, then it is illegal
29836 to instantiate the generic with an indefinite type.
29837 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
29838 It will show up as a compile time error, and
29839 the fix is usually simply to add the @code{(<>)} to the generic declaration.
29842 @node More deterministic semantics
29843 @subsection More deterministic semantics
29847 Conversions from real types to integer types round away from 0. In Ada 83
29848 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
29849 implementation freedom was intended to support unbiased rounding in
29850 statistical applications, but in practice it interfered with portability.
29851 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
29852 is required. Numeric code may be affected by this change in semantics.
29853 Note, though, that this issue is no worse than already existed in Ada 83
29854 when porting code from one vendor to another.
29857 The Real-Time Annex introduces a set of policies that define the behavior of
29858 features that were implementation dependent in Ada 83, such as the order in
29859 which open select branches are executed.
29862 @node Changed semantics
29863 @subsection Changed semantics
29866 The worst kind of incompatibility is one where a program that is legal in
29867 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
29868 possible in Ada 83. Fortunately this is extremely rare, but the one
29869 situation that you should be alert to is the change in the predefined type
29870 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
29873 @item Range of type @code{Character}
29874 The range of @code{Standard.Character} is now the full 256 characters
29875 of Latin-1, whereas in most Ada 83 implementations it was restricted
29876 to 128 characters. Although some of the effects of
29877 this change will be manifest in compile-time rejection of legal
29878 Ada 83 programs it is possible for a working Ada 83 program to have
29879 a different effect in Ada 95, one that was not permitted in Ada 83.
29880 As an example, the expression
29881 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
29882 delivers @code{255} as its value.
29883 In general, you should look at the logic of any
29884 character-processing Ada 83 program and see whether it needs to be adapted
29885 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
29886 character handling package that may be relevant if code needs to be adapted
29887 to account for the additional Latin-1 elements.
29888 The desirable fix is to
29889 modify the program to accommodate the full character set, but in some cases
29890 it may be convenient to define a subtype or derived type of Character that
29891 covers only the restricted range.
29895 @node Other language compatibility issues
29896 @subsection Other language compatibility issues
29899 @item @option{-gnat83} switch
29900 All implementations of GNAT provide a switch that causes GNAT to operate
29901 in Ada 83 mode. In this mode, some but not all compatibility problems
29902 of the type described above are handled automatically. For example, the
29903 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
29904 as identifiers as in Ada 83.
29906 in practice, it is usually advisable to make the necessary modifications
29907 to the program to remove the need for using this switch.
29908 See @ref{Compiling Different Versions of Ada}.
29910 @item Support for removed Ada 83 pragmas and attributes
29911 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
29912 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
29913 compilers are allowed, but not required, to implement these missing
29914 elements. In contrast with some other compilers, GNAT implements all
29915 such pragmas and attributes, eliminating this compatibility concern. These
29916 include @code{pragma Interface} and the floating point type attributes
29917 (@code{Emax}, @code{Mantissa}, etc.), among other items.
29921 @node Compatibility between Ada 95 and Ada 2005
29922 @section Compatibility between Ada 95 and Ada 2005
29923 @cindex Compatibility between Ada 95 and Ada 2005
29926 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
29927 a number of incompatibilities. Several are enumerated below;
29928 for a complete description please see the
29929 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
29930 @cite{Rationale for Ada 2005}.
29933 @item New reserved words.
29934 The words @code{interface}, @code{overriding} and @code{synchronized} are
29935 reserved in Ada 2005.
29936 A pre-Ada 2005 program that uses any of these as an identifier will be
29939 @item New declarations in predefined packages.
29940 A number of packages in the predefined environment contain new declarations:
29941 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
29942 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
29943 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
29944 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
29945 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
29946 If an Ada 95 program does a @code{with} and @code{use} of any of these
29947 packages, the new declarations may cause name clashes.
29949 @item Access parameters.
29950 A nondispatching subprogram with an access parameter cannot be renamed
29951 as a dispatching operation. This was permitted in Ada 95.
29953 @item Access types, discriminants, and constraints.
29954 Rule changes in this area have led to some incompatibilities; for example,
29955 constrained subtypes of some access types are not permitted in Ada 2005.
29957 @item Aggregates for limited types.
29958 The allowance of aggregates for limited types in Ada 2005 raises the
29959 possibility of ambiguities in legal Ada 95 programs, since additional types
29960 now need to be considered in expression resolution.
29962 @item Fixed-point multiplication and division.
29963 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
29964 were legal in Ada 95 and invoked the predefined versions of these operations,
29966 The ambiguity may be resolved either by applying a type conversion to the
29967 expression, or by explicitly invoking the operation from package
29970 @item Return-by-reference types.
29971 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
29972 can declare a function returning a value from an anonymous access type.
29976 @node Implementation-dependent characteristics
29977 @section Implementation-dependent characteristics
29979 Although the Ada language defines the semantics of each construct as
29980 precisely as practical, in some situations (for example for reasons of
29981 efficiency, or where the effect is heavily dependent on the host or target
29982 platform) the implementation is allowed some freedom. In porting Ada 83
29983 code to GNAT, you need to be aware of whether / how the existing code
29984 exercised such implementation dependencies. Such characteristics fall into
29985 several categories, and GNAT offers specific support in assisting the
29986 transition from certain Ada 83 compilers.
29989 * Implementation-defined pragmas::
29990 * Implementation-defined attributes::
29992 * Elaboration order::
29993 * Target-specific aspects::
29996 @node Implementation-defined pragmas
29997 @subsection Implementation-defined pragmas
30000 Ada compilers are allowed to supplement the language-defined pragmas, and
30001 these are a potential source of non-portability. All GNAT-defined pragmas
30002 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30003 Reference Manual}, and these include several that are specifically
30004 intended to correspond to other vendors' Ada 83 pragmas.
30005 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30006 For compatibility with HP Ada 83, GNAT supplies the pragmas
30007 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30008 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30009 and @code{Volatile}.
30010 Other relevant pragmas include @code{External} and @code{Link_With}.
30011 Some vendor-specific
30012 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30014 avoiding compiler rejection of units that contain such pragmas; they are not
30015 relevant in a GNAT context and hence are not otherwise implemented.
30017 @node Implementation-defined attributes
30018 @subsection Implementation-defined attributes
30020 Analogous to pragmas, the set of attributes may be extended by an
30021 implementation. All GNAT-defined attributes are described in
30022 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30023 Manual}, and these include several that are specifically intended
30024 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30025 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30026 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30030 @subsection Libraries
30032 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30033 code uses vendor-specific libraries then there are several ways to manage
30034 this in Ada 95 or Ada 2005:
30037 If the source code for the libraries (specs and bodies) are
30038 available, then the libraries can be migrated in the same way as the
30041 If the source code for the specs but not the bodies are
30042 available, then you can reimplement the bodies.
30044 Some features introduced by Ada 95 obviate the need for library support. For
30045 example most Ada 83 vendors supplied a package for unsigned integers. The
30046 Ada 95 modular type feature is the preferred way to handle this need, so
30047 instead of migrating or reimplementing the unsigned integer package it may
30048 be preferable to retrofit the application using modular types.
30051 @node Elaboration order
30052 @subsection Elaboration order
30054 The implementation can choose any elaboration order consistent with the unit
30055 dependency relationship. This freedom means that some orders can result in
30056 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30057 to invoke a subprogram its body has been elaborated, or to instantiate a
30058 generic before the generic body has been elaborated. By default GNAT
30059 attempts to choose a safe order (one that will not encounter access before
30060 elaboration problems) by implicitly inserting @code{Elaborate} or
30061 @code{Elaborate_All} pragmas where
30062 needed. However, this can lead to the creation of elaboration circularities
30063 and a resulting rejection of the program by gnatbind. This issue is
30064 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30065 In brief, there are several
30066 ways to deal with this situation:
30070 Modify the program to eliminate the circularities, e.g.@: by moving
30071 elaboration-time code into explicitly-invoked procedures
30073 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30074 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30075 @code{Elaborate_All}
30076 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30077 (by selectively suppressing elaboration checks via pragma
30078 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30081 @node Target-specific aspects
30082 @subsection Target-specific aspects
30084 Low-level applications need to deal with machine addresses, data
30085 representations, interfacing with assembler code, and similar issues. If
30086 such an Ada 83 application is being ported to different target hardware (for
30087 example where the byte endianness has changed) then you will need to
30088 carefully examine the program logic; the porting effort will heavily depend
30089 on the robustness of the original design. Moreover, Ada 95 (and thus
30090 Ada 2005) are sometimes
30091 incompatible with typical Ada 83 compiler practices regarding implicit
30092 packing, the meaning of the Size attribute, and the size of access values.
30093 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30095 @node Compatibility with Other Ada Systems
30096 @section Compatibility with Other Ada Systems
30099 If programs avoid the use of implementation dependent and
30100 implementation defined features, as documented in the @cite{Ada
30101 Reference Manual}, there should be a high degree of portability between
30102 GNAT and other Ada systems. The following are specific items which
30103 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30104 compilers, but do not affect porting code to GNAT@.
30105 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30106 the following issues may or may not arise for Ada 2005 programs
30107 when other compilers appear.)
30110 @item Ada 83 Pragmas and Attributes
30111 Ada 95 compilers are allowed, but not required, to implement the missing
30112 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30113 GNAT implements all such pragmas and attributes, eliminating this as
30114 a compatibility concern, but some other Ada 95 compilers reject these
30115 pragmas and attributes.
30117 @item Specialized Needs Annexes
30118 GNAT implements the full set of special needs annexes. At the
30119 current time, it is the only Ada 95 compiler to do so. This means that
30120 programs making use of these features may not be portable to other Ada
30121 95 compilation systems.
30123 @item Representation Clauses
30124 Some other Ada 95 compilers implement only the minimal set of
30125 representation clauses required by the Ada 95 reference manual. GNAT goes
30126 far beyond this minimal set, as described in the next section.
30129 @node Representation Clauses
30130 @section Representation Clauses
30133 The Ada 83 reference manual was quite vague in describing both the minimal
30134 required implementation of representation clauses, and also their precise
30135 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30136 minimal set of capabilities required is still quite limited.
30138 GNAT implements the full required set of capabilities in
30139 Ada 95 and Ada 2005, but also goes much further, and in particular
30140 an effort has been made to be compatible with existing Ada 83 usage to the
30141 greatest extent possible.
30143 A few cases exist in which Ada 83 compiler behavior is incompatible with
30144 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30145 intentional or accidental dependence on specific implementation dependent
30146 characteristics of these Ada 83 compilers. The following is a list of
30147 the cases most likely to arise in existing Ada 83 code.
30150 @item Implicit Packing
30151 Some Ada 83 compilers allowed a Size specification to cause implicit
30152 packing of an array or record. This could cause expensive implicit
30153 conversions for change of representation in the presence of derived
30154 types, and the Ada design intends to avoid this possibility.
30155 Subsequent AI's were issued to make it clear that such implicit
30156 change of representation in response to a Size clause is inadvisable,
30157 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30158 Reference Manuals as implementation advice that is followed by GNAT@.
30159 The problem will show up as an error
30160 message rejecting the size clause. The fix is simply to provide
30161 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30162 a Component_Size clause.
30164 @item Meaning of Size Attribute
30165 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30166 the minimal number of bits required to hold values of the type. For example,
30167 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30168 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30169 some 32 in this situation. This problem will usually show up as a compile
30170 time error, but not always. It is a good idea to check all uses of the
30171 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30172 Object_Size can provide a useful way of duplicating the behavior of
30173 some Ada 83 compiler systems.
30175 @item Size of Access Types
30176 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30177 and that therefore it will be the same size as a System.Address value. This
30178 assumption is true for GNAT in most cases with one exception. For the case of
30179 a pointer to an unconstrained array type (where the bounds may vary from one
30180 value of the access type to another), the default is to use a ``fat pointer'',
30181 which is represented as two separate pointers, one to the bounds, and one to
30182 the array. This representation has a number of advantages, including improved
30183 efficiency. However, it may cause some difficulties in porting existing Ada 83
30184 code which makes the assumption that, for example, pointers fit in 32 bits on
30185 a machine with 32-bit addressing.
30187 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30188 access types in this case (where the designated type is an unconstrained array
30189 type). These thin pointers are indeed the same size as a System.Address value.
30190 To specify a thin pointer, use a size clause for the type, for example:
30192 @smallexample @c ada
30193 type X is access all String;
30194 for X'Size use Standard'Address_Size;
30198 which will cause the type X to be represented using a single pointer.
30199 When using this representation, the bounds are right behind the array.
30200 This representation is slightly less efficient, and does not allow quite
30201 such flexibility in the use of foreign pointers or in using the
30202 Unrestricted_Access attribute to create pointers to non-aliased objects.
30203 But for any standard portable use of the access type it will work in
30204 a functionally correct manner and allow porting of existing code.
30205 Note that another way of forcing a thin pointer representation
30206 is to use a component size clause for the element size in an array,
30207 or a record representation clause for an access field in a record.
30211 @c This brief section is only in the non-VMS version
30212 @c The complete chapter on HP Ada is in the VMS version
30213 @node Compatibility with HP Ada 83
30214 @section Compatibility with HP Ada 83
30217 The VMS version of GNAT fully implements all the pragmas and attributes
30218 provided by HP Ada 83, as well as providing the standard HP Ada 83
30219 libraries, including Starlet. In addition, data layouts and parameter
30220 passing conventions are highly compatible. This means that porting
30221 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30222 most other porting efforts. The following are some of the most
30223 significant differences between GNAT and HP Ada 83.
30226 @item Default floating-point representation
30227 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30228 it is VMS format. GNAT does implement the necessary pragmas
30229 (Long_Float, Float_Representation) for changing this default.
30232 The package System in GNAT exactly corresponds to the definition in the
30233 Ada 95 reference manual, which means that it excludes many of the
30234 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30235 that contains the additional definitions, and a special pragma,
30236 Extend_System allows this package to be treated transparently as an
30237 extension of package System.
30240 The definitions provided by Aux_DEC are exactly compatible with those
30241 in the HP Ada 83 version of System, with one exception.
30242 HP Ada provides the following declarations:
30244 @smallexample @c ada
30245 TO_ADDRESS (INTEGER)
30246 TO_ADDRESS (UNSIGNED_LONGWORD)
30247 TO_ADDRESS (@i{universal_integer})
30251 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30252 an extension to Ada 83 not strictly compatible with the reference manual.
30253 In GNAT, we are constrained to be exactly compatible with the standard,
30254 and this means we cannot provide this capability. In HP Ada 83, the
30255 point of this definition is to deal with a call like:
30257 @smallexample @c ada
30258 TO_ADDRESS (16#12777#);
30262 Normally, according to the Ada 83 standard, one would expect this to be
30263 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30264 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30265 definition using @i{universal_integer} takes precedence.
30267 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30268 is not possible to be 100% compatible. Since there are many programs using
30269 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30270 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30271 declarations provided in the GNAT version of AUX_Dec are:
30273 @smallexample @c ada
30274 function To_Address (X : Integer) return Address;
30275 pragma Pure_Function (To_Address);
30277 function To_Address_Long (X : Unsigned_Longword)
30279 pragma Pure_Function (To_Address_Long);
30283 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30284 change the name to TO_ADDRESS_LONG@.
30286 @item Task_Id values
30287 The Task_Id values assigned will be different in the two systems, and GNAT
30288 does not provide a specified value for the Task_Id of the environment task,
30289 which in GNAT is treated like any other declared task.
30293 For full details on these and other less significant compatibility issues,
30294 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30295 Overview and Comparison on HP Platforms}.
30297 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30298 attributes are recognized, although only a subset of them can sensibly
30299 be implemented. The description of pragmas in @ref{Implementation
30300 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30301 indicates whether or not they are applicable to non-VMS systems.
30305 @node Transitioning to 64-Bit GNAT for OpenVMS
30306 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30309 This section is meant to assist users of pre-2006 @value{EDITION}
30310 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30311 the version of the GNAT technology supplied in 2006 and later for
30312 OpenVMS on both Alpha and I64.
30315 * Introduction to transitioning::
30316 * Migration of 32 bit code::
30317 * Taking advantage of 64 bit addressing::
30318 * Technical details::
30321 @node Introduction to transitioning
30322 @subsection Introduction
30325 64-bit @value{EDITION} for Open VMS has been designed to meet
30330 Providing a full conforming implementation of Ada 95 and Ada 2005
30333 Allowing maximum backward compatibility, thus easing migration of existing
30337 Supplying a path for exploiting the full 64-bit address range
30341 Ada's strong typing semantics has made it
30342 impractical to have different 32-bit and 64-bit modes. As soon as
30343 one object could possibly be outside the 32-bit address space, this
30344 would make it necessary for the @code{System.Address} type to be 64 bits.
30345 In particular, this would cause inconsistencies if 32-bit code is
30346 called from 64-bit code that raises an exception.
30348 This issue has been resolved by always using 64-bit addressing
30349 at the system level, but allowing for automatic conversions between
30350 32-bit and 64-bit addresses where required. Thus users who
30351 do not currently require 64-bit addressing capabilities, can
30352 recompile their code with only minimal changes (and indeed
30353 if the code is written in portable Ada, with no assumptions about
30354 the size of the @code{Address} type, then no changes at all are necessary).
30356 this approach provides a simple, gradual upgrade path to future
30357 use of larger memories than available for 32-bit systems.
30358 Also, newly written applications or libraries will by default
30359 be fully compatible with future systems exploiting 64-bit
30360 addressing capabilities.
30362 @ref{Migration of 32 bit code}, will focus on porting applications
30363 that do not require more than 2 GB of
30364 addressable memory. This code will be referred to as
30365 @emph{32-bit code}.
30366 For applications intending to exploit the full 64-bit address space,
30367 @ref{Taking advantage of 64 bit addressing},
30368 will consider further changes that may be required.
30369 Such code will be referred to below as @emph{64-bit code}.
30371 @node Migration of 32 bit code
30372 @subsection Migration of 32-bit code
30377 * Unchecked conversions::
30378 * Predefined constants::
30379 * Interfacing with C::
30380 * Experience with source compatibility::
30383 @node Address types
30384 @subsubsection Address types
30387 To solve the problem of mixing 64-bit and 32-bit addressing,
30388 while maintaining maximum backward compatibility, the following
30389 approach has been taken:
30393 @code{System.Address} always has a size of 64 bits
30396 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
30400 Since @code{System.Short_Address} is a subtype of @code{System.Address},
30401 a @code{Short_Address}
30402 may be used where an @code{Address} is required, and vice versa, without
30403 needing explicit type conversions.
30404 By virtue of the Open VMS parameter passing conventions,
30406 and exported subprograms that have 32-bit address parameters are
30407 compatible with those that have 64-bit address parameters.
30408 (See @ref{Making code 64 bit clean} for details.)
30410 The areas that may need attention are those where record types have
30411 been defined that contain components of the type @code{System.Address}, and
30412 where objects of this type are passed to code expecting a record layout with
30415 Different compilers on different platforms cannot be
30416 expected to represent the same type in the same way,
30417 since alignment constraints
30418 and other system-dependent properties affect the compiler's decision.
30419 For that reason, Ada code
30420 generally uses representation clauses to specify the expected
30421 layout where required.
30423 If such a representation clause uses 32 bits for a component having
30424 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
30425 will detect that error and produce a specific diagnostic message.
30426 The developer should then determine whether the representation
30427 should be 64 bits or not and make either of two changes:
30428 change the size to 64 bits and leave the type as @code{System.Address}, or
30429 leave the size as 32 bits and change the type to @code{System.Short_Address}.
30430 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
30431 required in any code setting or accessing the field; the compiler will
30432 automatically perform any needed conversions between address
30436 @subsubsection Access types
30439 By default, objects designated by access values are always
30440 allocated in the 32-bit
30441 address space. Thus legacy code will never contain
30442 any objects that are not addressable with 32-bit addresses, and
30443 the compiler will never raise exceptions as result of mixing
30444 32-bit and 64-bit addresses.
30446 However, the access values themselves are represented in 64 bits, for optimum
30447 performance and future compatibility with 64-bit code. As was
30448 the case with @code{System.Address}, the compiler will give an error message
30449 if an object or record component has a representation clause that
30450 requires the access value to fit in 32 bits. In such a situation,
30451 an explicit size clause for the access type, specifying 32 bits,
30452 will have the desired effect.
30454 General access types (declared with @code{access all}) can never be
30455 32 bits, as values of such types must be able to refer to any object
30456 of the designated type,
30457 including objects residing outside the 32-bit address range.
30458 Existing Ada 83 code will not contain such type definitions,
30459 however, since general access types were introduced in Ada 95.
30461 @node Unchecked conversions
30462 @subsubsection Unchecked conversions
30465 In the case of an @code{Unchecked_Conversion} where the source type is a
30466 64-bit access type or the type @code{System.Address}, and the target
30467 type is a 32-bit type, the compiler will generate a warning.
30468 Even though the generated code will still perform the required
30469 conversions, it is highly recommended in these cases to use
30470 respectively a 32-bit access type or @code{System.Short_Address}
30471 as the source type.
30473 @node Predefined constants
30474 @subsubsection Predefined constants
30477 The following table shows the correspondence between pre-2006 versions of
30478 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
30481 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
30482 @item @b{Constant} @tab @b{Old} @tab @b{New}
30483 @item @code{System.Word_Size} @tab 32 @tab 64
30484 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
30485 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
30486 @item @code{System.Address_Size} @tab 32 @tab 64
30490 If you need to refer to the specific
30491 memory size of a 32-bit implementation, instead of the
30492 actual memory size, use @code{System.Short_Memory_Size}
30493 rather than @code{System.Memory_Size}.
30494 Similarly, references to @code{System.Address_Size} may need
30495 to be replaced by @code{System.Short_Address'Size}.
30496 The program @command{gnatfind} may be useful for locating
30497 references to the above constants, so that you can verify that they
30500 @node Interfacing with C
30501 @subsubsection Interfacing with C
30504 In order to minimize the impact of the transition to 64-bit addresses on
30505 legacy programs, some fundamental types in the @code{Interfaces.C}
30506 package hierarchy continue to be represented in 32 bits.
30507 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
30508 This eases integration with the default HP C layout choices, for example
30509 as found in the system routines in @code{DECC$SHR.EXE}.
30510 Because of this implementation choice, the type fully compatible with
30511 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
30512 Depending on the context the compiler will issue a
30513 warning or an error when type @code{Address} is used, alerting the user to a
30514 potential problem. Otherwise 32-bit programs that use
30515 @code{Interfaces.C} should normally not require code modifications
30517 The other issue arising with C interfacing concerns pragma @code{Convention}.
30518 For VMS 64-bit systems, there is an issue of the appropriate default size
30519 of C convention pointers in the absence of an explicit size clause. The HP
30520 C compiler can choose either 32 or 64 bits depending on compiler options.
30521 GNAT chooses 32-bits rather than 64-bits in the default case where no size
30522 clause is given. This proves a better choice for porting 32-bit legacy
30523 applications. In order to have a 64-bit representation, it is necessary to
30524 specify a size representation clause. For example:
30526 @smallexample @c ada
30527 type int_star is access Interfaces.C.int;
30528 pragma Convention(C, int_star);
30529 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
30532 @node Experience with source compatibility
30533 @subsubsection Experience with source compatibility
30536 The Security Server and STARLET on I64 provide an interesting ``test case''
30537 for source compatibility issues, since it is in such system code
30538 where assumptions about @code{Address} size might be expected to occur.
30539 Indeed, there were a small number of occasions in the Security Server
30540 file @file{jibdef.ads}
30541 where a representation clause for a record type specified
30542 32 bits for a component of type @code{Address}.
30543 All of these errors were detected by the compiler.
30544 The repair was obvious and immediate; to simply replace @code{Address} by
30545 @code{Short_Address}.
30547 In the case of STARLET, there were several record types that should
30548 have had representation clauses but did not. In these record types
30549 there was an implicit assumption that an @code{Address} value occupied
30551 These compiled without error, but their usage resulted in run-time error
30552 returns from STARLET system calls.
30553 Future GNAT technology enhancements may include a tool that detects and flags
30554 these sorts of potential source code porting problems.
30556 @c ****************************************
30557 @node Taking advantage of 64 bit addressing
30558 @subsection Taking advantage of 64-bit addressing
30561 * Making code 64 bit clean::
30562 * Allocating memory from the 64 bit storage pool::
30563 * Restrictions on use of 64 bit objects::
30564 * Using 64 bit storage pools by default::
30565 * General access types::
30566 * STARLET and other predefined libraries::
30569 @node Making code 64 bit clean
30570 @subsubsection Making code 64-bit clean
30573 In order to prevent problems that may occur when (parts of) a
30574 system start using memory outside the 32-bit address range,
30575 we recommend some additional guidelines:
30579 For imported subprograms that take parameters of the
30580 type @code{System.Address}, ensure that these subprograms can
30581 indeed handle 64-bit addresses. If not, or when in doubt,
30582 change the subprogram declaration to specify
30583 @code{System.Short_Address} instead.
30586 Resolve all warnings related to size mismatches in
30587 unchecked conversions. Failing to do so causes
30588 erroneous execution if the source object is outside
30589 the 32-bit address space.
30592 (optional) Explicitly use the 32-bit storage pool
30593 for access types used in a 32-bit context, or use
30594 generic access types where possible
30595 (@pxref{Restrictions on use of 64 bit objects}).
30599 If these rules are followed, the compiler will automatically insert
30600 any necessary checks to ensure that no addresses or access values
30601 passed to 32-bit code ever refer to objects outside the 32-bit
30603 Any attempt to do this will raise @code{Constraint_Error}.
30605 @node Allocating memory from the 64 bit storage pool
30606 @subsubsection Allocating memory from the 64-bit storage pool
30609 For any access type @code{T} that potentially requires memory allocations
30610 beyond the 32-bit address space,
30611 use the following representation clause:
30613 @smallexample @c ada
30614 for T'Storage_Pool use System.Pool_64;
30617 @node Restrictions on use of 64 bit objects
30618 @subsubsection Restrictions on use of 64-bit objects
30621 Taking the address of an object allocated from a 64-bit storage pool,
30622 and then passing this address to a subprogram expecting
30623 @code{System.Short_Address},
30624 or assigning it to a variable of type @code{Short_Address}, will cause
30625 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
30626 (@pxref{Making code 64 bit clean}), or checks are suppressed,
30627 no exception is raised and execution
30628 will become erroneous.
30630 @node Using 64 bit storage pools by default
30631 @subsubsection Using 64-bit storage pools by default
30634 In some cases it may be desirable to have the compiler allocate
30635 from 64-bit storage pools by default. This may be the case for
30636 libraries that are 64-bit clean, but may be used in both 32-bit
30637 and 64-bit contexts. For these cases the following configuration
30638 pragma may be specified:
30640 @smallexample @c ada
30641 pragma Pool_64_Default;
30645 Any code compiled in the context of this pragma will by default
30646 use the @code{System.Pool_64} storage pool. This default may be overridden
30647 for a specific access type @code{T} by the representation clause:
30649 @smallexample @c ada
30650 for T'Storage_Pool use System.Pool_32;
30654 Any object whose address may be passed to a subprogram with a
30655 @code{Short_Address} argument, or assigned to a variable of type
30656 @code{Short_Address}, needs to be allocated from this pool.
30658 @node General access types
30659 @subsubsection General access types
30662 Objects designated by access values from a
30663 general access type (declared with @code{access all}) are never allocated
30664 from a 64-bit storage pool. Code that uses general access types will
30665 accept objects allocated in either 32-bit or 64-bit address spaces,
30666 but never allocate objects outside the 32-bit address space.
30667 Using general access types ensures maximum compatibility with both
30668 32-bit and 64-bit code.
30670 @node STARLET and other predefined libraries
30671 @subsubsection STARLET and other predefined libraries
30674 All code that comes as part of GNAT is 64-bit clean, but the
30675 restrictions given in @ref{Restrictions on use of 64 bit objects},
30676 still apply. Look at the package
30677 specs to see in which contexts objects allocated
30678 in 64-bit address space are acceptable.
30680 @node Technical details
30681 @subsection Technical details
30684 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
30685 Ada standard with respect to the type of @code{System.Address}. Previous
30686 versions of GNAT Pro have defined this type as private and implemented it as a
30689 In order to allow defining @code{System.Short_Address} as a proper subtype,
30690 and to match the implicit sign extension in parameter passing,
30691 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
30692 visible (i.e., non-private) integer type.
30693 Standard operations on the type, such as the binary operators ``+'', ``-'',
30694 etc., that take @code{Address} operands and return an @code{Address} result,
30695 have been hidden by declaring these
30696 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
30697 ambiguities that would otherwise result from overloading.
30698 (Note that, although @code{Address} is a visible integer type,
30699 good programming practice dictates against exploiting the type's
30700 integer properties such as literals, since this will compromise
30703 Defining @code{Address} as a visible integer type helps achieve
30704 maximum compatibility for existing Ada code,
30705 without sacrificing the capabilities of the 64-bit architecture.
30708 @c ************************************************
30710 @node Microsoft Windows Topics
30711 @appendix Microsoft Windows Topics
30717 This chapter describes topics that are specific to the Microsoft Windows
30718 platforms (NT, 2000, and XP Professional).
30721 * Using GNAT on Windows::
30722 * Using a network installation of GNAT::
30723 * CONSOLE and WINDOWS subsystems::
30724 * Temporary Files::
30725 * Mixed-Language Programming on Windows::
30726 * Windows Calling Conventions::
30727 * Introduction to Dynamic Link Libraries (DLLs)::
30728 * Using DLLs with GNAT::
30729 * Building DLLs with GNAT::
30730 * Building DLLs with GNAT Project files::
30731 * Building DLLs with gnatdll::
30732 * GNAT and Windows Resources::
30733 * Debugging a DLL::
30734 * Setting Stack Size from gnatlink::
30735 * Setting Heap Size from gnatlink::
30738 @node Using GNAT on Windows
30739 @section Using GNAT on Windows
30742 One of the strengths of the GNAT technology is that its tool set
30743 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
30744 @code{gdb} debugger, etc.) is used in the same way regardless of the
30747 On Windows this tool set is complemented by a number of Microsoft-specific
30748 tools that have been provided to facilitate interoperability with Windows
30749 when this is required. With these tools:
30754 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
30758 You can use any Dynamically Linked Library (DLL) in your Ada code (both
30759 relocatable and non-relocatable DLLs are supported).
30762 You can build Ada DLLs for use in other applications. These applications
30763 can be written in a language other than Ada (e.g., C, C++, etc). Again both
30764 relocatable and non-relocatable Ada DLLs are supported.
30767 You can include Windows resources in your Ada application.
30770 You can use or create COM/DCOM objects.
30774 Immediately below are listed all known general GNAT-for-Windows restrictions.
30775 Other restrictions about specific features like Windows Resources and DLLs
30776 are listed in separate sections below.
30781 It is not possible to use @code{GetLastError} and @code{SetLastError}
30782 when tasking, protected records, or exceptions are used. In these
30783 cases, in order to implement Ada semantics, the GNAT run-time system
30784 calls certain Win32 routines that set the last error variable to 0 upon
30785 success. It should be possible to use @code{GetLastError} and
30786 @code{SetLastError} when tasking, protected record, and exception
30787 features are not used, but it is not guaranteed to work.
30790 It is not possible to link against Microsoft libraries except for
30791 import libraries. The library must be built to be compatible with
30792 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
30793 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
30794 not be compatible with the GNAT runtime. Even if the library is
30795 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
30798 When the compilation environment is located on FAT32 drives, users may
30799 experience recompilations of the source files that have not changed if
30800 Daylight Saving Time (DST) state has changed since the last time files
30801 were compiled. NTFS drives do not have this problem.
30804 No components of the GNAT toolset use any entries in the Windows
30805 registry. The only entries that can be created are file associations and
30806 PATH settings, provided the user has chosen to create them at installation
30807 time, as well as some minimal book-keeping information needed to correctly
30808 uninstall or integrate different GNAT products.
30811 @node Using a network installation of GNAT
30812 @section Using a network installation of GNAT
30815 Make sure the system on which GNAT is installed is accessible from the
30816 current machine, i.e., the install location is shared over the network.
30817 Shared resources are accessed on Windows by means of UNC paths, which
30818 have the format @code{\\server\sharename\path}
30820 In order to use such a network installation, simply add the UNC path of the
30821 @file{bin} directory of your GNAT installation in front of your PATH. For
30822 example, if GNAT is installed in @file{\GNAT} directory of a share location
30823 called @file{c-drive} on a machine @file{LOKI}, the following command will
30826 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
30828 Be aware that every compilation using the network installation results in the
30829 transfer of large amounts of data across the network and will likely cause
30830 serious performance penalty.
30832 @node CONSOLE and WINDOWS subsystems
30833 @section CONSOLE and WINDOWS subsystems
30834 @cindex CONSOLE Subsystem
30835 @cindex WINDOWS Subsystem
30839 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
30840 (which is the default subsystem) will always create a console when
30841 launching the application. This is not something desirable when the
30842 application has a Windows GUI. To get rid of this console the
30843 application must be using the @code{WINDOWS} subsystem. To do so
30844 the @option{-mwindows} linker option must be specified.
30847 $ gnatmake winprog -largs -mwindows
30850 @node Temporary Files
30851 @section Temporary Files
30852 @cindex Temporary files
30855 It is possible to control where temporary files gets created by setting
30856 the @env{TMP} environment variable. The file will be created:
30859 @item Under the directory pointed to by the @env{TMP} environment variable if
30860 this directory exists.
30862 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
30863 set (or not pointing to a directory) and if this directory exists.
30865 @item Under the current working directory otherwise.
30869 This allows you to determine exactly where the temporary
30870 file will be created. This is particularly useful in networked
30871 environments where you may not have write access to some
30874 @node Mixed-Language Programming on Windows
30875 @section Mixed-Language Programming on Windows
30878 Developing pure Ada applications on Windows is no different than on
30879 other GNAT-supported platforms. However, when developing or porting an
30880 application that contains a mix of Ada and C/C++, the choice of your
30881 Windows C/C++ development environment conditions your overall
30882 interoperability strategy.
30884 If you use @command{gcc} to compile the non-Ada part of your application,
30885 there are no Windows-specific restrictions that affect the overall
30886 interoperability with your Ada code. If you plan to use
30887 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
30888 the following limitations:
30892 You cannot link your Ada code with an object or library generated with
30893 Microsoft tools if these use the @code{.tls} section (Thread Local
30894 Storage section) since the GNAT linker does not yet support this section.
30897 You cannot link your Ada code with an object or library generated with
30898 Microsoft tools if these use I/O routines other than those provided in
30899 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
30900 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
30901 libraries can cause a conflict with @code{msvcrt.dll} services. For
30902 instance Visual C++ I/O stream routines conflict with those in
30907 If you do want to use the Microsoft tools for your non-Ada code and hit one
30908 of the above limitations, you have two choices:
30912 Encapsulate your non-Ada code in a DLL to be linked with your Ada
30913 application. In this case, use the Microsoft or whatever environment to
30914 build the DLL and use GNAT to build your executable
30915 (@pxref{Using DLLs with GNAT}).
30918 Or you can encapsulate your Ada code in a DLL to be linked with the
30919 other part of your application. In this case, use GNAT to build the DLL
30920 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
30921 environment to build your executable.
30924 @node Windows Calling Conventions
30925 @section Windows Calling Conventions
30930 * C Calling Convention::
30931 * Stdcall Calling Convention::
30932 * Win32 Calling Convention::
30933 * DLL Calling Convention::
30937 When a subprogram @code{F} (caller) calls a subprogram @code{G}
30938 (callee), there are several ways to push @code{G}'s parameters on the
30939 stack and there are several possible scenarios to clean up the stack
30940 upon @code{G}'s return. A calling convention is an agreed upon software
30941 protocol whereby the responsibilities between the caller (@code{F}) and
30942 the callee (@code{G}) are clearly defined. Several calling conventions
30943 are available for Windows:
30947 @code{C} (Microsoft defined)
30950 @code{Stdcall} (Microsoft defined)
30953 @code{Win32} (GNAT specific)
30956 @code{DLL} (GNAT specific)
30959 @node C Calling Convention
30960 @subsection @code{C} Calling Convention
30963 This is the default calling convention used when interfacing to C/C++
30964 routines compiled with either @command{gcc} or Microsoft Visual C++.
30966 In the @code{C} calling convention subprogram parameters are pushed on the
30967 stack by the caller from right to left. The caller itself is in charge of
30968 cleaning up the stack after the call. In addition, the name of a routine
30969 with @code{C} calling convention is mangled by adding a leading underscore.
30971 The name to use on the Ada side when importing (or exporting) a routine
30972 with @code{C} calling convention is the name of the routine. For
30973 instance the C function:
30976 int get_val (long);
30980 should be imported from Ada as follows:
30982 @smallexample @c ada
30984 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
30985 pragma Import (C, Get_Val, External_Name => "get_val");
30990 Note that in this particular case the @code{External_Name} parameter could
30991 have been omitted since, when missing, this parameter is taken to be the
30992 name of the Ada entity in lower case. When the @code{Link_Name} parameter
30993 is missing, as in the above example, this parameter is set to be the
30994 @code{External_Name} with a leading underscore.
30996 When importing a variable defined in C, you should always use the @code{C}
30997 calling convention unless the object containing the variable is part of a
30998 DLL (in which case you should use the @code{Stdcall} calling
30999 convention, @pxref{Stdcall Calling Convention}).
31001 @node Stdcall Calling Convention
31002 @subsection @code{Stdcall} Calling Convention
31005 This convention, which was the calling convention used for Pascal
31006 programs, is used by Microsoft for all the routines in the Win32 API for
31007 efficiency reasons. It must be used to import any routine for which this
31008 convention was specified.
31010 In the @code{Stdcall} calling convention subprogram parameters are pushed
31011 on the stack by the caller from right to left. The callee (and not the
31012 caller) is in charge of cleaning the stack on routine exit. In addition,
31013 the name of a routine with @code{Stdcall} calling convention is mangled by
31014 adding a leading underscore (as for the @code{C} calling convention) and a
31015 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31016 bytes) of the parameters passed to the routine.
31018 The name to use on the Ada side when importing a C routine with a
31019 @code{Stdcall} calling convention is the name of the C routine. The leading
31020 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31021 the compiler. For instance the Win32 function:
31024 @b{APIENTRY} int get_val (long);
31028 should be imported from Ada as follows:
31030 @smallexample @c ada
31032 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31033 pragma Import (Stdcall, Get_Val);
31034 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31039 As for the @code{C} calling convention, when the @code{External_Name}
31040 parameter is missing, it is taken to be the name of the Ada entity in lower
31041 case. If instead of writing the above import pragma you write:
31043 @smallexample @c ada
31045 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31046 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31051 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31052 of specifying the @code{External_Name} parameter you specify the
31053 @code{Link_Name} as in the following example:
31055 @smallexample @c ada
31057 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31058 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31063 then the imported routine is @code{retrieve_val}, that is, there is no
31064 decoration at all. No leading underscore and no Stdcall suffix
31065 @code{@@}@code{@var{nn}}.
31068 This is especially important as in some special cases a DLL's entry
31069 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31070 name generated for a call has it.
31073 It is also possible to import variables defined in a DLL by using an
31074 import pragma for a variable. As an example, if a DLL contains a
31075 variable defined as:
31082 then, to access this variable from Ada you should write:
31084 @smallexample @c ada
31086 My_Var : Interfaces.C.int;
31087 pragma Import (Stdcall, My_Var);
31092 Note that to ease building cross-platform bindings this convention
31093 will be handled as a @code{C} calling convention on non-Windows platforms.
31095 @node Win32 Calling Convention
31096 @subsection @code{Win32} Calling Convention
31099 This convention, which is GNAT-specific is fully equivalent to the
31100 @code{Stdcall} calling convention described above.
31102 @node DLL Calling Convention
31103 @subsection @code{DLL} Calling Convention
31106 This convention, which is GNAT-specific is fully equivalent to the
31107 @code{Stdcall} calling convention described above.
31109 @node Introduction to Dynamic Link Libraries (DLLs)
31110 @section Introduction to Dynamic Link Libraries (DLLs)
31114 A Dynamically Linked Library (DLL) is a library that can be shared by
31115 several applications running under Windows. A DLL can contain any number of
31116 routines and variables.
31118 One advantage of DLLs is that you can change and enhance them without
31119 forcing all the applications that depend on them to be relinked or
31120 recompiled. However, you should be aware than all calls to DLL routines are
31121 slower since, as you will understand below, such calls are indirect.
31123 To illustrate the remainder of this section, suppose that an application
31124 wants to use the services of a DLL @file{API.dll}. To use the services
31125 provided by @file{API.dll} you must statically link against the DLL or
31126 an import library which contains a jump table with an entry for each
31127 routine and variable exported by the DLL. In the Microsoft world this
31128 import library is called @file{API.lib}. When using GNAT this import
31129 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31130 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31132 After you have linked your application with the DLL or the import library
31133 and you run your application, here is what happens:
31137 Your application is loaded into memory.
31140 The DLL @file{API.dll} is mapped into the address space of your
31141 application. This means that:
31145 The DLL will use the stack of the calling thread.
31148 The DLL will use the virtual address space of the calling process.
31151 The DLL will allocate memory from the virtual address space of the calling
31155 Handles (pointers) can be safely exchanged between routines in the DLL
31156 routines and routines in the application using the DLL.
31160 The entries in the jump table (from the import library @file{libAPI.dll.a}
31161 or @file{API.lib} or automatically created when linking against a DLL)
31162 which is part of your application are initialized with the addresses
31163 of the routines and variables in @file{API.dll}.
31166 If present in @file{API.dll}, routines @code{DllMain} or
31167 @code{DllMainCRTStartup} are invoked. These routines typically contain
31168 the initialization code needed for the well-being of the routines and
31169 variables exported by the DLL.
31173 There is an additional point which is worth mentioning. In the Windows
31174 world there are two kind of DLLs: relocatable and non-relocatable
31175 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31176 in the target application address space. If the addresses of two
31177 non-relocatable DLLs overlap and these happen to be used by the same
31178 application, a conflict will occur and the application will run
31179 incorrectly. Hence, when possible, it is always preferable to use and
31180 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31181 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31182 User's Guide) removes the debugging symbols from the DLL but the DLL can
31183 still be relocated.
31185 As a side note, an interesting difference between Microsoft DLLs and
31186 Unix shared libraries, is the fact that on most Unix systems all public
31187 routines are exported by default in a Unix shared library, while under
31188 Windows it is possible (but not required) to list exported routines in
31189 a definition file (@pxref{The Definition File}).
31191 @node Using DLLs with GNAT
31192 @section Using DLLs with GNAT
31195 * Creating an Ada Spec for the DLL Services::
31196 * Creating an Import Library::
31200 To use the services of a DLL, say @file{API.dll}, in your Ada application
31205 The Ada spec for the routines and/or variables you want to access in
31206 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31207 header files provided with the DLL.
31210 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31211 mentioned an import library is a statically linked library containing the
31212 import table which will be filled at load time to point to the actual
31213 @file{API.dll} routines. Sometimes you don't have an import library for the
31214 DLL you want to use. The following sections will explain how to build
31215 one. Note that this is optional.
31218 The actual DLL, @file{API.dll}.
31222 Once you have all the above, to compile an Ada application that uses the
31223 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31224 you simply issue the command
31227 $ gnatmake my_ada_app -largs -lAPI
31231 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31232 tells the GNAT linker to look first for a library named @file{API.lib}
31233 (Microsoft-style name) and if not found for a libraries named
31234 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31235 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31236 contains the following pragma
31238 @smallexample @c ada
31239 pragma Linker_Options ("-lAPI");
31243 you do not have to add @option{-largs -lAPI} at the end of the
31244 @command{gnatmake} command.
31246 If any one of the items above is missing you will have to create it
31247 yourself. The following sections explain how to do so using as an
31248 example a fictitious DLL called @file{API.dll}.
31250 @node Creating an Ada Spec for the DLL Services
31251 @subsection Creating an Ada Spec for the DLL Services
31254 A DLL typically comes with a C/C++ header file which provides the
31255 definitions of the routines and variables exported by the DLL. The Ada
31256 equivalent of this header file is a package spec that contains definitions
31257 for the imported entities. If the DLL you intend to use does not come with
31258 an Ada spec you have to generate one such spec yourself. For example if
31259 the header file of @file{API.dll} is a file @file{api.h} containing the
31260 following two definitions:
31272 then the equivalent Ada spec could be:
31274 @smallexample @c ada
31277 with Interfaces.C.Strings;
31282 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31285 pragma Import (C, Get);
31286 pragma Import (DLL, Some_Var);
31293 Note that a variable is
31294 @strong{always imported with a Stdcall convention}. A function
31295 can have @code{C} or @code{Stdcall} convention.
31296 (@pxref{Windows Calling Conventions}).
31298 @node Creating an Import Library
31299 @subsection Creating an Import Library
31300 @cindex Import library
31303 * The Definition File::
31304 * GNAT-Style Import Library::
31305 * Microsoft-Style Import Library::
31309 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31310 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31311 with @file{API.dll} you can skip this section. You can also skip this
31312 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31313 as in this case it is possible to link directly against the
31314 DLL. Otherwise read on.
31316 @node The Definition File
31317 @subsubsection The Definition File
31318 @cindex Definition file
31322 As previously mentioned, and unlike Unix systems, the list of symbols
31323 that are exported from a DLL must be provided explicitly in Windows.
31324 The main goal of a definition file is precisely that: list the symbols
31325 exported by a DLL. A definition file (usually a file with a @code{.def}
31326 suffix) has the following structure:
31331 @r{[}LIBRARY @var{name}@r{]}
31332 @r{[}DESCRIPTION @var{string}@r{]}
31342 @item LIBRARY @var{name}
31343 This section, which is optional, gives the name of the DLL.
31345 @item DESCRIPTION @var{string}
31346 This section, which is optional, gives a description string that will be
31347 embedded in the import library.
31350 This section gives the list of exported symbols (procedures, functions or
31351 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
31352 section of @file{API.def} looks like:
31366 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
31367 (@pxref{Windows Calling Conventions}) for a Stdcall
31368 calling convention function in the exported symbols list.
31371 There can actually be other sections in a definition file, but these
31372 sections are not relevant to the discussion at hand.
31374 @node GNAT-Style Import Library
31375 @subsubsection GNAT-Style Import Library
31378 To create a static import library from @file{API.dll} with the GNAT tools
31379 you should proceed as follows:
31383 Create the definition file @file{API.def} (@pxref{The Definition File}).
31384 For that use the @code{dll2def} tool as follows:
31387 $ dll2def API.dll > API.def
31391 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
31392 to standard output the list of entry points in the DLL. Note that if
31393 some routines in the DLL have the @code{Stdcall} convention
31394 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
31395 suffix then you'll have to edit @file{api.def} to add it, and specify
31396 @option{-k} to @command{gnatdll} when creating the import library.
31399 Here are some hints to find the right @code{@@}@var{nn} suffix.
31403 If you have the Microsoft import library (.lib), it is possible to get
31404 the right symbols by using Microsoft @code{dumpbin} tool (see the
31405 corresponding Microsoft documentation for further details).
31408 $ dumpbin /exports api.lib
31412 If you have a message about a missing symbol at link time the compiler
31413 tells you what symbol is expected. You just have to go back to the
31414 definition file and add the right suffix.
31418 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
31419 (@pxref{Using gnatdll}) as follows:
31422 $ gnatdll -e API.def -d API.dll
31426 @code{gnatdll} takes as input a definition file @file{API.def} and the
31427 name of the DLL containing the services listed in the definition file
31428 @file{API.dll}. The name of the static import library generated is
31429 computed from the name of the definition file as follows: if the
31430 definition file name is @var{xyz}@code{.def}, the import library name will
31431 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
31432 @option{-e} could have been removed because the name of the definition
31433 file (before the ``@code{.def}'' suffix) is the same as the name of the
31434 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
31437 @node Microsoft-Style Import Library
31438 @subsubsection Microsoft-Style Import Library
31441 With GNAT you can either use a GNAT-style or Microsoft-style import
31442 library. A Microsoft import library is needed only if you plan to make an
31443 Ada DLL available to applications developed with Microsoft
31444 tools (@pxref{Mixed-Language Programming on Windows}).
31446 To create a Microsoft-style import library for @file{API.dll} you
31447 should proceed as follows:
31451 Create the definition file @file{API.def} from the DLL. For this use either
31452 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
31453 tool (see the corresponding Microsoft documentation for further details).
31456 Build the actual import library using Microsoft's @code{lib} utility:
31459 $ lib -machine:IX86 -def:API.def -out:API.lib
31463 If you use the above command the definition file @file{API.def} must
31464 contain a line giving the name of the DLL:
31471 See the Microsoft documentation for further details about the usage of
31475 @node Building DLLs with GNAT
31476 @section Building DLLs with GNAT
31477 @cindex DLLs, building
31480 This section explain how to build DLLs using the GNAT built-in DLL
31481 support. With the following procedure it is straight forward to build
31482 and use DLLs with GNAT.
31486 @item building object files
31488 The first step is to build all objects files that are to be included
31489 into the DLL. This is done by using the standard @command{gnatmake} tool.
31491 @item building the DLL
31493 To build the DLL you must use @command{gcc}'s @option{-shared}
31494 option. It is quite simple to use this method:
31497 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
31500 It is important to note that in this case all symbols found in the
31501 object files are automatically exported. It is possible to restrict
31502 the set of symbols to export by passing to @command{gcc} a definition
31503 file, @pxref{The Definition File}. For example:
31506 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
31509 If you use a definition file you must export the elaboration procedures
31510 for every package that required one. Elaboration procedures are named
31511 using the package name followed by "_E".
31513 @item preparing DLL to be used
31515 For the DLL to be used by client programs the bodies must be hidden
31516 from it and the .ali set with read-only attribute. This is very important
31517 otherwise GNAT will recompile all packages and will not actually use
31518 the code in the DLL. For example:
31522 $ copy *.ads *.ali api.dll apilib
31523 $ attrib +R apilib\*.ali
31528 At this point it is possible to use the DLL by directly linking
31529 against it. Note that you must use the GNAT shared runtime when using
31530 GNAT shared libraries. This is achieved by using @option{-shared} binder's
31534 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
31537 @node Building DLLs with GNAT Project files
31538 @section Building DLLs with GNAT Project files
31539 @cindex DLLs, building
31542 There is nothing specific to Windows in the build process.
31543 @pxref{Library Projects}.
31546 Due to a system limitation, it is not possible under Windows to create threads
31547 when inside the @code{DllMain} routine which is used for auto-initialization
31548 of shared libraries, so it is not possible to have library level tasks in SALs.
31550 @node Building DLLs with gnatdll
31551 @section Building DLLs with gnatdll
31552 @cindex DLLs, building
31555 * Limitations When Using Ada DLLs from Ada::
31556 * Exporting Ada Entities::
31557 * Ada DLLs and Elaboration::
31558 * Ada DLLs and Finalization::
31559 * Creating a Spec for Ada DLLs::
31560 * Creating the Definition File::
31565 Note that it is preferred to use the built-in GNAT DLL support
31566 (@pxref{Building DLLs with GNAT}) or GNAT Project files
31567 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
31569 This section explains how to build DLLs containing Ada code using
31570 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
31571 remainder of this section.
31573 The steps required to build an Ada DLL that is to be used by Ada as well as
31574 non-Ada applications are as follows:
31578 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
31579 @code{Stdcall} calling convention to avoid any Ada name mangling for the
31580 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
31581 skip this step if you plan to use the Ada DLL only from Ada applications.
31584 Your Ada code must export an initialization routine which calls the routine
31585 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
31586 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
31587 routine exported by the Ada DLL must be invoked by the clients of the DLL
31588 to initialize the DLL.
31591 When useful, the DLL should also export a finalization routine which calls
31592 routine @code{adafinal} generated by @command{gnatbind} to perform the
31593 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
31594 The finalization routine exported by the Ada DLL must be invoked by the
31595 clients of the DLL when the DLL services are no further needed.
31598 You must provide a spec for the services exported by the Ada DLL in each
31599 of the programming languages to which you plan to make the DLL available.
31602 You must provide a definition file listing the exported entities
31603 (@pxref{The Definition File}).
31606 Finally you must use @code{gnatdll} to produce the DLL and the import
31607 library (@pxref{Using gnatdll}).
31611 Note that a relocatable DLL stripped using the @code{strip}
31612 binutils tool will not be relocatable anymore. To build a DLL without
31613 debug information pass @code{-largs -s} to @code{gnatdll}. This
31614 restriction does not apply to a DLL built using a Library Project.
31615 @pxref{Library Projects}.
31617 @node Limitations When Using Ada DLLs from Ada
31618 @subsection Limitations When Using Ada DLLs from Ada
31621 When using Ada DLLs from Ada applications there is a limitation users
31622 should be aware of. Because on Windows the GNAT run time is not in a DLL of
31623 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
31624 each Ada DLL includes the services of the GNAT run time that are necessary
31625 to the Ada code inside the DLL. As a result, when an Ada program uses an
31626 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
31627 one in the main program.
31629 It is therefore not possible to exchange GNAT run-time objects between the
31630 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
31631 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
31634 It is completely safe to exchange plain elementary, array or record types,
31635 Windows object handles, etc.
31637 @node Exporting Ada Entities
31638 @subsection Exporting Ada Entities
31639 @cindex Export table
31642 Building a DLL is a way to encapsulate a set of services usable from any
31643 application. As a result, the Ada entities exported by a DLL should be
31644 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
31645 any Ada name mangling. As an example here is an Ada package
31646 @code{API}, spec and body, exporting two procedures, a function, and a
31649 @smallexample @c ada
31652 with Interfaces.C; use Interfaces;
31654 Count : C.int := 0;
31655 function Factorial (Val : C.int) return C.int;
31657 procedure Initialize_API;
31658 procedure Finalize_API;
31659 -- Initialization & Finalization routines. More in the next section.
31661 pragma Export (C, Initialize_API);
31662 pragma Export (C, Finalize_API);
31663 pragma Export (C, Count);
31664 pragma Export (C, Factorial);
31670 @smallexample @c ada
31673 package body API is
31674 function Factorial (Val : C.int) return C.int is
31677 Count := Count + 1;
31678 for K in 1 .. Val loop
31684 procedure Initialize_API is
31686 pragma Import (C, Adainit);
31689 end Initialize_API;
31691 procedure Finalize_API is
31692 procedure Adafinal;
31693 pragma Import (C, Adafinal);
31703 If the Ada DLL you are building will only be used by Ada applications
31704 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
31705 convention. As an example, the previous package could be written as
31708 @smallexample @c ada
31712 Count : Integer := 0;
31713 function Factorial (Val : Integer) return Integer;
31715 procedure Initialize_API;
31716 procedure Finalize_API;
31717 -- Initialization and Finalization routines.
31723 @smallexample @c ada
31726 package body API is
31727 function Factorial (Val : Integer) return Integer is
31728 Fact : Integer := 1;
31730 Count := Count + 1;
31731 for K in 1 .. Val loop
31738 -- The remainder of this package body is unchanged.
31745 Note that if you do not export the Ada entities with a @code{C} or
31746 @code{Stdcall} convention you will have to provide the mangled Ada names
31747 in the definition file of the Ada DLL
31748 (@pxref{Creating the Definition File}).
31750 @node Ada DLLs and Elaboration
31751 @subsection Ada DLLs and Elaboration
31752 @cindex DLLs and elaboration
31755 The DLL that you are building contains your Ada code as well as all the
31756 routines in the Ada library that are needed by it. The first thing a
31757 user of your DLL must do is elaborate the Ada code
31758 (@pxref{Elaboration Order Handling in GNAT}).
31760 To achieve this you must export an initialization routine
31761 (@code{Initialize_API} in the previous example), which must be invoked
31762 before using any of the DLL services. This elaboration routine must call
31763 the Ada elaboration routine @code{adainit} generated by the GNAT binder
31764 (@pxref{Binding with Non-Ada Main Programs}). See the body of
31765 @code{Initialize_Api} for an example. Note that the GNAT binder is
31766 automatically invoked during the DLL build process by the @code{gnatdll}
31767 tool (@pxref{Using gnatdll}).
31769 When a DLL is loaded, Windows systematically invokes a routine called
31770 @code{DllMain}. It would therefore be possible to call @code{adainit}
31771 directly from @code{DllMain} without having to provide an explicit
31772 initialization routine. Unfortunately, it is not possible to call
31773 @code{adainit} from the @code{DllMain} if your program has library level
31774 tasks because access to the @code{DllMain} entry point is serialized by
31775 the system (that is, only a single thread can execute ``through'' it at a
31776 time), which means that the GNAT run time will deadlock waiting for the
31777 newly created task to complete its initialization.
31779 @node Ada DLLs and Finalization
31780 @subsection Ada DLLs and Finalization
31781 @cindex DLLs and finalization
31784 When the services of an Ada DLL are no longer needed, the client code should
31785 invoke the DLL finalization routine, if available. The DLL finalization
31786 routine is in charge of releasing all resources acquired by the DLL. In the
31787 case of the Ada code contained in the DLL, this is achieved by calling
31788 routine @code{adafinal} generated by the GNAT binder
31789 (@pxref{Binding with Non-Ada Main Programs}).
31790 See the body of @code{Finalize_Api} for an
31791 example. As already pointed out the GNAT binder is automatically invoked
31792 during the DLL build process by the @code{gnatdll} tool
31793 (@pxref{Using gnatdll}).
31795 @node Creating a Spec for Ada DLLs
31796 @subsection Creating a Spec for Ada DLLs
31799 To use the services exported by the Ada DLL from another programming
31800 language (e.g.@: C), you have to translate the specs of the exported Ada
31801 entities in that language. For instance in the case of @code{API.dll},
31802 the corresponding C header file could look like:
31807 extern int *_imp__count;
31808 #define count (*_imp__count)
31809 int factorial (int);
31815 It is important to understand that when building an Ada DLL to be used by
31816 other Ada applications, you need two different specs for the packages
31817 contained in the DLL: one for building the DLL and the other for using
31818 the DLL. This is because the @code{DLL} calling convention is needed to
31819 use a variable defined in a DLL, but when building the DLL, the variable
31820 must have either the @code{Ada} or @code{C} calling convention. As an
31821 example consider a DLL comprising the following package @code{API}:
31823 @smallexample @c ada
31827 Count : Integer := 0;
31829 -- Remainder of the package omitted.
31836 After producing a DLL containing package @code{API}, the spec that
31837 must be used to import @code{API.Count} from Ada code outside of the
31840 @smallexample @c ada
31845 pragma Import (DLL, Count);
31851 @node Creating the Definition File
31852 @subsection Creating the Definition File
31855 The definition file is the last file needed to build the DLL. It lists
31856 the exported symbols. As an example, the definition file for a DLL
31857 containing only package @code{API} (where all the entities are exported
31858 with a @code{C} calling convention) is:
31873 If the @code{C} calling convention is missing from package @code{API},
31874 then the definition file contains the mangled Ada names of the above
31875 entities, which in this case are:
31884 api__initialize_api
31889 @node Using gnatdll
31890 @subsection Using @code{gnatdll}
31894 * gnatdll Example::
31895 * gnatdll behind the Scenes::
31900 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
31901 and non-Ada sources that make up your DLL have been compiled.
31902 @code{gnatdll} is actually in charge of two distinct tasks: build the
31903 static import library for the DLL and the actual DLL. The form of the
31904 @code{gnatdll} command is
31908 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
31913 where @var{list-of-files} is a list of ALI and object files. The object
31914 file list must be the exact list of objects corresponding to the non-Ada
31915 sources whose services are to be included in the DLL. The ALI file list
31916 must be the exact list of ALI files for the corresponding Ada sources
31917 whose services are to be included in the DLL. If @var{list-of-files} is
31918 missing, only the static import library is generated.
31921 You may specify any of the following switches to @code{gnatdll}:
31924 @item -a@ovar{address}
31925 @cindex @option{-a} (@code{gnatdll})
31926 Build a non-relocatable DLL at @var{address}. If @var{address} is not
31927 specified the default address @var{0x11000000} will be used. By default,
31928 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
31929 advise the reader to build relocatable DLL.
31931 @item -b @var{address}
31932 @cindex @option{-b} (@code{gnatdll})
31933 Set the relocatable DLL base address. By default the address is
31936 @item -bargs @var{opts}
31937 @cindex @option{-bargs} (@code{gnatdll})
31938 Binder options. Pass @var{opts} to the binder.
31940 @item -d @var{dllfile}
31941 @cindex @option{-d} (@code{gnatdll})
31942 @var{dllfile} is the name of the DLL. This switch must be present for
31943 @code{gnatdll} to do anything. The name of the generated import library is
31944 obtained algorithmically from @var{dllfile} as shown in the following
31945 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
31946 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
31947 by option @option{-e}) is obtained algorithmically from @var{dllfile}
31948 as shown in the following example:
31949 if @var{dllfile} is @code{xyz.dll}, the definition
31950 file used is @code{xyz.def}.
31952 @item -e @var{deffile}
31953 @cindex @option{-e} (@code{gnatdll})
31954 @var{deffile} is the name of the definition file.
31957 @cindex @option{-g} (@code{gnatdll})
31958 Generate debugging information. This information is stored in the object
31959 file and copied from there to the final DLL file by the linker,
31960 where it can be read by the debugger. You must use the
31961 @option{-g} switch if you plan on using the debugger or the symbolic
31965 @cindex @option{-h} (@code{gnatdll})
31966 Help mode. Displays @code{gnatdll} switch usage information.
31969 @cindex @option{-I} (@code{gnatdll})
31970 Direct @code{gnatdll} to search the @var{dir} directory for source and
31971 object files needed to build the DLL.
31972 (@pxref{Search Paths and the Run-Time Library (RTL)}).
31975 @cindex @option{-k} (@code{gnatdll})
31976 Removes the @code{@@}@var{nn} suffix from the import library's exported
31977 names, but keeps them for the link names. You must specify this
31978 option if you want to use a @code{Stdcall} function in a DLL for which
31979 the @code{@@}@var{nn} suffix has been removed. This is the case for most
31980 of the Windows NT DLL for example. This option has no effect when
31981 @option{-n} option is specified.
31983 @item -l @var{file}
31984 @cindex @option{-l} (@code{gnatdll})
31985 The list of ALI and object files used to build the DLL are listed in
31986 @var{file}, instead of being given in the command line. Each line in
31987 @var{file} contains the name of an ALI or object file.
31990 @cindex @option{-n} (@code{gnatdll})
31991 No Import. Do not create the import library.
31994 @cindex @option{-q} (@code{gnatdll})
31995 Quiet mode. Do not display unnecessary messages.
31998 @cindex @option{-v} (@code{gnatdll})
31999 Verbose mode. Display extra information.
32001 @item -largs @var{opts}
32002 @cindex @option{-largs} (@code{gnatdll})
32003 Linker options. Pass @var{opts} to the linker.
32006 @node gnatdll Example
32007 @subsubsection @code{gnatdll} Example
32010 As an example the command to build a relocatable DLL from @file{api.adb}
32011 once @file{api.adb} has been compiled and @file{api.def} created is
32014 $ gnatdll -d api.dll api.ali
32018 The above command creates two files: @file{libapi.dll.a} (the import
32019 library) and @file{api.dll} (the actual DLL). If you want to create
32020 only the DLL, just type:
32023 $ gnatdll -d api.dll -n api.ali
32027 Alternatively if you want to create just the import library, type:
32030 $ gnatdll -d api.dll
32033 @node gnatdll behind the Scenes
32034 @subsubsection @code{gnatdll} behind the Scenes
32037 This section details the steps involved in creating a DLL. @code{gnatdll}
32038 does these steps for you. Unless you are interested in understanding what
32039 goes on behind the scenes, you should skip this section.
32041 We use the previous example of a DLL containing the Ada package @code{API},
32042 to illustrate the steps necessary to build a DLL. The starting point is a
32043 set of objects that will make up the DLL and the corresponding ALI
32044 files. In the case of this example this means that @file{api.o} and
32045 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32050 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32051 the information necessary to generate relocation information for the
32057 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32062 In addition to the base file, the @command{gnatlink} command generates an
32063 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32064 asks @command{gnatlink} to generate the routines @code{DllMain} and
32065 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32066 is loaded into memory.
32069 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32070 export table (@file{api.exp}). The export table contains the relocation
32071 information in a form which can be used during the final link to ensure
32072 that the Windows loader is able to place the DLL anywhere in memory.
32076 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32077 --output-exp api.exp
32082 @code{gnatdll} builds the base file using the new export table. Note that
32083 @command{gnatbind} must be called once again since the binder generated file
32084 has been deleted during the previous call to @command{gnatlink}.
32089 $ gnatlink api -o api.jnk api.exp -mdll
32090 -Wl,--base-file,api.base
32095 @code{gnatdll} builds the new export table using the new base file and
32096 generates the DLL import library @file{libAPI.dll.a}.
32100 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32101 --output-exp api.exp --output-lib libAPI.a
32106 Finally @code{gnatdll} builds the relocatable DLL using the final export
32112 $ gnatlink api api.exp -o api.dll -mdll
32117 @node Using dlltool
32118 @subsubsection Using @code{dlltool}
32121 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32122 DLLs and static import libraries. This section summarizes the most
32123 common @code{dlltool} switches. The form of the @code{dlltool} command
32127 $ dlltool @ovar{switches}
32131 @code{dlltool} switches include:
32134 @item --base-file @var{basefile}
32135 @cindex @option{--base-file} (@command{dlltool})
32136 Read the base file @var{basefile} generated by the linker. This switch
32137 is used to create a relocatable DLL.
32139 @item --def @var{deffile}
32140 @cindex @option{--def} (@command{dlltool})
32141 Read the definition file.
32143 @item --dllname @var{name}
32144 @cindex @option{--dllname} (@command{dlltool})
32145 Gives the name of the DLL. This switch is used to embed the name of the
32146 DLL in the static import library generated by @code{dlltool} with switch
32147 @option{--output-lib}.
32150 @cindex @option{-k} (@command{dlltool})
32151 Kill @code{@@}@var{nn} from exported names
32152 (@pxref{Windows Calling Conventions}
32153 for a discussion about @code{Stdcall}-style symbols.
32156 @cindex @option{--help} (@command{dlltool})
32157 Prints the @code{dlltool} switches with a concise description.
32159 @item --output-exp @var{exportfile}
32160 @cindex @option{--output-exp} (@command{dlltool})
32161 Generate an export file @var{exportfile}. The export file contains the
32162 export table (list of symbols in the DLL) and is used to create the DLL.
32164 @item --output-lib @var{libfile}
32165 @cindex @option{--output-lib} (@command{dlltool})
32166 Generate a static import library @var{libfile}.
32169 @cindex @option{-v} (@command{dlltool})
32172 @item --as @var{assembler-name}
32173 @cindex @option{--as} (@command{dlltool})
32174 Use @var{assembler-name} as the assembler. The default is @code{as}.
32177 @node GNAT and Windows Resources
32178 @section GNAT and Windows Resources
32179 @cindex Resources, windows
32182 * Building Resources::
32183 * Compiling Resources::
32184 * Using Resources::
32188 Resources are an easy way to add Windows specific objects to your
32189 application. The objects that can be added as resources include:
32218 This section explains how to build, compile and use resources.
32220 @node Building Resources
32221 @subsection Building Resources
32222 @cindex Resources, building
32225 A resource file is an ASCII file. By convention resource files have an
32226 @file{.rc} extension.
32227 The easiest way to build a resource file is to use Microsoft tools
32228 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32229 @code{dlgedit.exe} to build dialogs.
32230 It is always possible to build an @file{.rc} file yourself by writing a
32233 It is not our objective to explain how to write a resource file. A
32234 complete description of the resource script language can be found in the
32235 Microsoft documentation.
32237 @node Compiling Resources
32238 @subsection Compiling Resources
32241 @cindex Resources, compiling
32244 This section describes how to build a GNAT-compatible (COFF) object file
32245 containing the resources. This is done using the Resource Compiler
32246 @code{windres} as follows:
32249 $ windres -i myres.rc -o myres.o
32253 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32254 file. You can specify an alternate preprocessor (usually named
32255 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32256 parameter. A list of all possible options may be obtained by entering
32257 the command @code{windres} @option{--help}.
32259 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32260 to produce a @file{.res} file (binary resource file). See the
32261 corresponding Microsoft documentation for further details. In this case
32262 you need to use @code{windres} to translate the @file{.res} file to a
32263 GNAT-compatible object file as follows:
32266 $ windres -i myres.res -o myres.o
32269 @node Using Resources
32270 @subsection Using Resources
32271 @cindex Resources, using
32274 To include the resource file in your program just add the
32275 GNAT-compatible object file for the resource(s) to the linker
32276 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32280 $ gnatmake myprog -largs myres.o
32283 @node Debugging a DLL
32284 @section Debugging a DLL
32285 @cindex DLL debugging
32288 * Program and DLL Both Built with GCC/GNAT::
32289 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32293 Debugging a DLL is similar to debugging a standard program. But
32294 we have to deal with two different executable parts: the DLL and the
32295 program that uses it. We have the following four possibilities:
32299 The program and the DLL are built with @code{GCC/GNAT}.
32301 The program is built with foreign tools and the DLL is built with
32304 The program is built with @code{GCC/GNAT} and the DLL is built with
32310 In this section we address only cases one and two above.
32311 There is no point in trying to debug
32312 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32313 information in it. To do so you must use a debugger compatible with the
32314 tools suite used to build the DLL.
32316 @node Program and DLL Both Built with GCC/GNAT
32317 @subsection Program and DLL Both Built with GCC/GNAT
32320 This is the simplest case. Both the DLL and the program have @code{GDB}
32321 compatible debugging information. It is then possible to break anywhere in
32322 the process. Let's suppose here that the main procedure is named
32323 @code{ada_main} and that in the DLL there is an entry point named
32327 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32328 program must have been built with the debugging information (see GNAT -g
32329 switch). Here are the step-by-step instructions for debugging it:
32332 @item Launch @code{GDB} on the main program.
32338 @item Start the program and stop at the beginning of the main procedure
32345 This step is required to be able to set a breakpoint inside the DLL. As long
32346 as the program is not run, the DLL is not loaded. This has the
32347 consequence that the DLL debugging information is also not loaded, so it is not
32348 possible to set a breakpoint in the DLL.
32350 @item Set a breakpoint inside the DLL
32353 (gdb) break ada_dll
32360 At this stage a breakpoint is set inside the DLL. From there on
32361 you can use the standard approach to debug the whole program
32362 (@pxref{Running and Debugging Ada Programs}).
32365 @c This used to work, probably because the DLLs were non-relocatable
32366 @c keep this section around until the problem is sorted out.
32368 To break on the @code{DllMain} routine it is not possible to follow
32369 the procedure above. At the time the program stop on @code{ada_main}
32370 the @code{DllMain} routine as already been called. Either you can use
32371 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
32374 @item Launch @code{GDB} on the main program.
32380 @item Load DLL symbols
32383 (gdb) add-sym api.dll
32386 @item Set a breakpoint inside the DLL
32389 (gdb) break ada_dll.adb:45
32392 Note that at this point it is not possible to break using the routine symbol
32393 directly as the program is not yet running. The solution is to break
32394 on the proper line (break in @file{ada_dll.adb} line 45).
32396 @item Start the program
32405 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
32406 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
32409 * Debugging the DLL Directly::
32410 * Attaching to a Running Process::
32414 In this case things are slightly more complex because it is not possible to
32415 start the main program and then break at the beginning to load the DLL and the
32416 associated DLL debugging information. It is not possible to break at the
32417 beginning of the program because there is no @code{GDB} debugging information,
32418 and therefore there is no direct way of getting initial control. This
32419 section addresses this issue by describing some methods that can be used
32420 to break somewhere in the DLL to debug it.
32423 First suppose that the main procedure is named @code{main} (this is for
32424 example some C code built with Microsoft Visual C) and that there is a
32425 DLL named @code{test.dll} containing an Ada entry point named
32429 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
32430 been built with debugging information (see GNAT -g option).
32432 @node Debugging the DLL Directly
32433 @subsubsection Debugging the DLL Directly
32437 Find out the executable starting address
32440 $ objdump --file-header main.exe
32443 The starting address is reported on the last line. For example:
32446 main.exe: file format pei-i386
32447 architecture: i386, flags 0x0000010a:
32448 EXEC_P, HAS_DEBUG, D_PAGED
32449 start address 0x00401010
32453 Launch the debugger on the executable.
32460 Set a breakpoint at the starting address, and launch the program.
32463 $ (gdb) break *0x00401010
32467 The program will stop at the given address.
32470 Set a breakpoint on a DLL subroutine.
32473 (gdb) break ada_dll.adb:45
32476 Or if you want to break using a symbol on the DLL, you need first to
32477 select the Ada language (language used by the DLL).
32480 (gdb) set language ada
32481 (gdb) break ada_dll
32485 Continue the program.
32492 This will run the program until it reaches the breakpoint that has been
32493 set. From that point you can use the standard way to debug a program
32494 as described in (@pxref{Running and Debugging Ada Programs}).
32499 It is also possible to debug the DLL by attaching to a running process.
32501 @node Attaching to a Running Process
32502 @subsubsection Attaching to a Running Process
32503 @cindex DLL debugging, attach to process
32506 With @code{GDB} it is always possible to debug a running process by
32507 attaching to it. It is possible to debug a DLL this way. The limitation
32508 of this approach is that the DLL must run long enough to perform the
32509 attach operation. It may be useful for instance to insert a time wasting
32510 loop in the code of the DLL to meet this criterion.
32514 @item Launch the main program @file{main.exe}.
32520 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
32521 that the process PID for @file{main.exe} is 208.
32529 @item Attach to the running process to be debugged.
32535 @item Load the process debugging information.
32538 (gdb) symbol-file main.exe
32541 @item Break somewhere in the DLL.
32544 (gdb) break ada_dll
32547 @item Continue process execution.
32556 This last step will resume the process execution, and stop at
32557 the breakpoint we have set. From there you can use the standard
32558 approach to debug a program as described in
32559 (@pxref{Running and Debugging Ada Programs}).
32561 @node Setting Stack Size from gnatlink
32562 @section Setting Stack Size from @command{gnatlink}
32565 It is possible to specify the program stack size at link time. On modern
32566 versions of Windows, starting with XP, this is mostly useful to set the size of
32567 the main stack (environment task). The other task stacks are set with pragma
32568 Storage_Size or with the @command{gnatbind -d} command.
32570 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
32571 reserve size of individual tasks, the link-time stack size applies to all
32572 tasks, and pragma Storage_Size has no effect.
32573 In particular, Stack Overflow checks are made against this
32574 link-time specified size.
32576 This setting can be done with
32577 @command{gnatlink} using either:
32581 @item using @option{-Xlinker} linker option
32584 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
32587 This sets the stack reserve size to 0x10000 bytes and the stack commit
32588 size to 0x1000 bytes.
32590 @item using @option{-Wl} linker option
32593 $ gnatlink hello -Wl,--stack=0x1000000
32596 This sets the stack reserve size to 0x1000000 bytes. Note that with
32597 @option{-Wl} option it is not possible to set the stack commit size
32598 because the coma is a separator for this option.
32602 @node Setting Heap Size from gnatlink
32603 @section Setting Heap Size from @command{gnatlink}
32606 Under Windows systems, it is possible to specify the program heap size from
32607 @command{gnatlink} using either:
32611 @item using @option{-Xlinker} linker option
32614 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
32617 This sets the heap reserve size to 0x10000 bytes and the heap commit
32618 size to 0x1000 bytes.
32620 @item using @option{-Wl} linker option
32623 $ gnatlink hello -Wl,--heap=0x1000000
32626 This sets the heap reserve size to 0x1000000 bytes. Note that with
32627 @option{-Wl} option it is not possible to set the heap commit size
32628 because the coma is a separator for this option.
32634 @c **********************************
32635 @c * GNU Free Documentation License *
32636 @c **********************************
32638 @c GNU Free Documentation License
32640 @node Index,,GNU Free Documentation License, Top
32646 @c Put table of contents at end, otherwise it precedes the "title page" in
32647 @c the .txt version
32648 @c Edit the pdf file to move the contents to the beginning, after the title